First Response in Fukushima Daiichi Nuclear Power Station

First Response at Tohoku Chihou Taiheiyou Oki Earthquake in Fukushima Daiichi Nuclear Power Station
We have put all efforts on settlement of the situation as the first
priority regarding the severe accident of the nuclear power station caused
by Tohoku Chihou Taiheiyou Oki Earthquake occurred on March 11, and
conducted a thorough survey and review on the accident.
This time, we would like to inform the facts on the first response at
Tohoku Chihou Taiheiyou Oki Earthquake in Fukushima Daiichi Nuclear Power
Station, based on various information sources as of today and interviews
with the relevant persons. In case that we find new facts through further
surveys, we would like to inform on another occasion.
Appendix1:List of Documents on Response in Fukushima Daiichi Nuclear Power Station(PDF 8.18KB)
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110618e3.pdf
Appendix2:Fukushima Daiichi Nuclear Power Station Response after the earthquake(PDF 485KB)
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110618e15.pdf
http://www.tepco.co.jp/en/press/corp-com/release/11061805-e.html
Press Release (Jun 18,2011)

Appendix1:List of Documents on Response in Fukushima Daiichi Nuclear Power Station(PDF 8.18KB)
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110618e3.pdf
Page 1 Page 1
List of Documents on Response in Fukushima Daiichi List of Documents on Response in Fukushima Daiichi
Nuclear Power Station Nuclear Power Station
○First Response at the Earthquake in Fukushima Daiichi Nuclear Power ○ First Response at the Earthquake in Fukushima Daiichi Nuclear Power
Station Station
○Main Timeline of Unit 1 of Fukushima Daiichi Nuclear Power Station from ○ Main Timeline of Unit 1 of Fukushima Daiichi Nuclear Power Station from
the Occurrence of the Earthquake to March 12 (Sat) the Occurrence of the Earthquake to March 12 (Sat)
・Response regarding Alternative Water Injection for Unit 1 of Fukushima ? Response regarding Alternative Water Injection for Unit 1 of Fukushima
Daiichi Nuclear Power Station Daiichi Nuclear Power Station
・Response regarding Ventilation Operation for Primary Containment ? Response regarding Ventilation Operation for Primary Containment
Vessel of Unit 1 of Fukushima Daiichi Nuclear Power Station Vessel of Unit 1 of Fukushima Daiichi Nuclear Power Station
○Main Timeline of Unit 2 of Fukushima Daiichi Nuclear Power Station from ○ Main Timeline of Unit 2 of Fukushima Daiichi Nuclear Power Station from
the Occurrence of the Earthquake to March 15 (Tue) the Occurrence of the Earthquake to March 15 (Tue)
・Response regarding Alternative Water Injection for Unit 2 of Fukushima ? Response regarding Alternative Water Injection for Unit 2 of Fukushima
Daiichi Nuclear Power Station Daiichi Nuclear Power Station
・Response regarding Ventilation Operation for Primary Containment ? Response regarding Ventilation Operation for Primary Containment
Vessel of Unit 2 of Fukushima Daiichi Nuclear Power Station Vessel of Unit 2 of Fukushima Daiichi Nuclear Power Station
○Main Timeline of Unit 3 of Fukushima Daiichi Nuclear Power Station from ○ Main Timeline of Unit 3 of Fukushima Daiichi Nuclear Power Station from
the Occurrence of the Earthquake to March 15 (Tue) the Occurrence of the Earthquake to March 15 (Tue)
・Response regarding Alternative Water Injection for Unit 3 of Fukushima ? Response regarding Alternative Water Injection for Unit 3 of Fukushima
Daiichi Nuclear Power Station Daiichi Nuclear Power Station
・Response regarding Ventilation Operation for Primary Containment ? Response regarding Ventilation Operation for Primary Containment
Page 2 Page 2
Vessel of Unit 3 of Fukushima Daiichi Nuclear Power Station Vessel of Unit 3 of Fukushima Daiichi Nuclear Power Station
○Main Timeline of Unit 4, 5 & 6 of Fukushima Daiichi Nuclear Power Station ○ Main Timeline of Unit 4, 5 & 6 of Fukushima Daiichi Nuclear Power Station
from the Occurrence of the Earthquake to March 15 (Tue) from the Occurrence of the Earthquake to March 15 (Tue)
End End
Original Japanese text:
Vessel of Unit 3 of Fukushima Daiichi Nuclear Power Station
Contribute a better translation
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110618e15.pdf


Appendix2:Fukushima Daiichi Nuclear Power Station Response after the earthquake(PDF 485KB)
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110618e15.pdf
Page 1 Page 1
Fukushima Daiichi Nuclear Power Station Fukushima Daiichi Nuclear Power Station
Response after the earthquake Response after the earthquake
This document is a summary of the latest information obtained through information and This document is a summary of the latest information obtained through information and
interviews with personnel concerned. We will continue investigation and announce interviews with personnel concerned. We will continue investigation and announce
when new facts and findings are obtained. when new facts and findings are obtained.
○Activities between occurrence of the Great East Japan Earthquake at 14:46, ○ Activities between occurrence of the Great East Japan Earthquake at 14:46,
March 11 to the first tsunami hit the site at 15:27 on March 11. March 11 to the first tsunami hit the site at 15:27 on March 11.
【 Evacuation and safety confirmation 】 Evacuation and safety confirmation []
・ Personnel in the administration building evacuated to the parking lot in front of the ? Personnel in the administration building evacuated to the parking lot in front of the
building and called over the names. Emergency response personnel stationed in the building and called over the names. Emergency response personnel stationed in the
Anti-Seismic Building (TSC Building) and started response. Everyone was familiar Anti-Seismic Building (TSC Building) and started response. Everyone was familiar
with evacuation route because emergency drill was done just a week before the with evacuation route because emergency drill was done just a week before the
earthquake. earthquake.
【 SCRAM Response 】 SCRAM Response []

・ Operators started normal scram response after the shaking trailed off. Shift ? Operators started normal scram response after the shaking trailed off. Shift
Supervisor confirmed scram of the units and supervised response in between the Supervisor confirmed scram of the units and supervised response in between the
unit 1 and 2 control panels. Each operator was assigned to control panels and Chief unit 1 and 2 control panels. Each operator was assigned to control panels and Chief
Operator conducted monitoring and operation, also reported plant situation to Shift Operator conducted monitoring and operation, also reported plant situation to Shift
Supervisor. Supervisor.
・ At 14:52, operators confirmed automatic start up of the Isolation Condenser (IC) at ? At 14:52, operators confirmed automatic start up of the Isolation Condenser (IC) at
Unit 1. Because reactor water stayed in normal level, operators decided to use HPCI Unit 1. Because reactor water stayed in normal level, operators decided to use HPCI
when water level dropped and to control reactor pressure by IC. when water level dropped and to control reactor pressure by IC.
・ At 15:03, reactor pressure of Unit 1 dropped so fast and the reactor coolant ? At 15:03, reactor pressure of Unit 1 dropped so fast and the reactor coolant
temperature decreased 55 C per hour, exceeding a criteria in the Tech.Spec. Then temperature decreased 55 C per hour, exceeding a criteria in the Tech.Spec. Then
operators closed MO-3A and 3B, return isolation valves of IC. IC was in stand-by operators closed MO-3A and 3B, return isolation valves of IC. IC was in stand-by
condition with other valves in the IC remained open. Operators judged that only one condition with other valves in the IC remained open. Operators judged that only one
train of IC was sufficient to control the reactor pressure in 6 -- 7 MPa. They decided train of IC was sufficient to control the reactor pressure in 6 - 7 MPa. They decided
to use Train A and started to control the pressure by operating MO-3A. to use Train A and started to control the pressure by operating MO-3A.
・ As for Unit 2, RCIC was started manually but tripped because of high reactor water ? As for Unit 2, RCIC was started manually but tripped because of high reactor water
level. After that, RCIC was started manually again. level. After that, RCIC was started manually again.

・ MCR became white as if laid a smoke screen by dust caused by the earthquake. ? MCR became white as if laid a smoke screen by dust caused by the earthquake.
Page 2 Page 2
After the shaking was trailed off, operators started normal scram response. Shift After the shaking was trailed off, operators started normal scram response. Shift
Supervisor was reported plant scrams. Emergency Diesel Generator (DG) started Supervisor was reported plant scrams. Emergency Diesel Generator (DG) started
up due to loss of off-site power. Emergency bus was confirmed to be charged by up due to loss of off-site power. Emergency bus was confirmed to be charged by
DG. DG.
・ At Unit 3, RCIC was manually started but tripped by high reactor water level. ? At Unit 3, RCIC was manually started but tripped by high reactor water level.
・ After the earthquake, safety of the operators was checked. Earthquake and Tsunami ? After the earthquake, safety of the operators was checked. Earthquake and Tsunami
alert were paged to the plant workers. alert were paged to the plant workers.

・ Shift Supervisor were checking control panel at his desk and securing his safety ? Shift Supervisor were checking control panel at his desk and securing his safety
until the shaking trailed off. Other operators also secured their safety at the same until the shaking trailed off. Other operators also secured their safety at the same
time paid attention to monitoring panels. After the shaking, operators checked time paid attention to monitoring panels. After the shaking, operators checked
alarms. Most of the alarms was sounding at that time. alarms. Most of the alarms was sounding at that time.
・ Since Paging and ITV were unavailable, PHS (Personal Handy phone System: like ? Since Paging and ITV were unavailable, PHS (Personal Handy phone System: like
cell phone) was utilized to order evacuation for field workers. Shift operators cell phone) was utilized to order evacuation for field workers. Shift operators
returned to the MCR after gathered in anteroom. returned to the MCR after gathered in anteroom.
○ Activities after Loss of all AC Power at 15:42 on March 11 ○ Activities after Loss of all AC Power at 15:42 on March 11
【Situation at Main Control Room of Unit 1/2】 - Situation at Main Control Room of Unit 1 / 2]
・ Lighting and indicators in the MCR gradually fading due to loss of all AC power. ? Lighting and indicators in the MCR gradually fading due to loss of all AC power.
Sound of alarm was lost, too. In Unit 1-side of MCR, only emergency lights remained. Sound of alarm was lost, too. In Unit 1-side of MCR, only emergency lights remained.
In Unit 2- side, all lighting was lost and it became completely dark. By command of In Unit 2 - side, all lighting was lost and it became completely dark. By command of
Shift Supervisor, operators checked availability of equipment in MCR. Shift Supervisor, operators checked availability of equipment in MCR.
・ For Unit1, IC and HPCI were operable by DC power. However, valve status of IC ? For Unit1, IC and HPCI were operable by DC power. However, valve status of IC
was not indicated on the control panel. Operators judged HPCI was not operable was not indicated on the control panel. Operators judged HPCI was not operable
because indicators on the control panel were gradually faded. For Unit 2, operating because indicators on the control panel were gradually faded. For Unit 2, operating
status of RCIC became unknown. status of RCIC became unknown.
・ At 15:50, instrumentation power was lost and reactor water levels for Units 1 and 2 ? At 15:50, instrumentation power was lost and reactor water levels for Units 1 and 2
became unknown. became unknown.
・ Communication between MCR and the site emergency response headquarters was ? Communication between MCR and the site emergency response headquarters was
limited to a hot-line and fixed-line phone, it was not able to use PHS. limited to a hot-line and fixed-line phone, it was not able to use PHS.
【Situation at Main Control Room of Unit 3/4】 - Situation at Main Control Room of Unit 3 / 4]
・ Due to loss of all AC power, lighting in MCR was emergency light only. Since Unit 4 ? Due to loss of all AC power, lighting in MCR was emergency light only. Since Unit 4
was in refueling outage and completely defueled, parameters such as reactor water was in refueling outage and completely defueled, parameters such as reactor water
level was checked mainly focused at Unit 3. This was conducted with flashlights. level was checked mainly focused at Unit 3. This was conducted with flashlights.
・ Per operating procedure at the time of loss of AC power, unnecessary load was cut ? Per operating procedure at the time of loss of AC power, unnecessary load was cut
to extend battery life for RCIC and HPCI. to extend battery life for RCIC and HPCI.
Page 3 Page 3
・ At 16:03, RCIC was manually started, parameters like discharge pressure and ? At 16:03, RCIC was manually started, parameters like discharge pressure and
rotating speed were confirmed in MCR. Operating status was monitored and made rotating speed were confirmed in MCR. Operating status was monitored and made
HPCI start up ready. HPCI start up ready.
【Situation at Main Control Room of Unit 5/6】 - Situation at Main Control Room of Unit 5 / 6]
・ Two DGs at Unit 5 and two DGs at Unit 6 were stopped simultaneously by the ? Two DGs at Unit 5 and two DGs at Unit 6 were stopped simultaneously by the
tsunami. One remained DG at Unit 6 continued operation with adjusting frequency. tsunami. One remained DG at Unit 6 continued operation with adjusting frequency.
・ MCR at Unit 5 lost lighting and emergency lights put on, but these emergency lights ? MCR at Unit 5 lost lighting and emergency lights put on, but these emergency lights
faded gradually then MCR became dark. MCR at Unit 6 was same as normal. faded gradually then MCR became dark. MCR at Unit 6 was same as normal.
・ ?
【 Restoration of MCR Instrumentation 】 [Restoration of MCR Instrumentation]
・ The restoration team in the site emergency ? The restoration team in the site emergency
response headquarters prepared for necessary response headquarters prepared for necessary
documents and drawings to restore power in MCRs. documents and drawings to restore power in MCRs.
Also they started to gather batteries and cables Also they started to gather batteries and cables
at offices of contractor's office in the site. The at offices of contractor's office in the site. The
team carried batteries and cables which were team carried batteries and cables which were
collected in the site to MCR of Unit 1/2. Then collected in the site to MCR of Unit 1 / 2. Then
confirming drawings, they started to connect confirming drawings, they started to connect
the batteries to instrument panel in the MCR . At the batteries to instrument panel in the MCR. At
the event of “ECCS was unavailable to inject water the event of "ECCS was unavailable to inject water
into the reactor”, a top priority was to understand into the reactor ", a top priority was to understand
the status of water injection into the RPV. So the status of water injection into the RPV. So
restoration work was focused on connecting restoration work was focused on connecting
batteries to reactor water indicator which functions batteries to reactor water indicator which functions
by DC power. by DC power.
・ Reactor water levels were become clear for Unit 1 ? Reactor water levels were become clear for Unit 1
at 21:19 and for Unit 2 at 21:50. at 21:19 and for Unit 2 at 21:50.
・ The restoration team of the emergency response headquarters installed a small ? The restoration team of the emergency response headquarters installed a small
generator to restore lighting in MCR. Temporary lights were installed in MCR of Unit generator to restore lighting in MCR. Temporary lights were installed in MCR of Unit
1/2 at 20:49 and Unit 3/4 at 21:58. 1 / 2 at 20:49 and Unit 3 / 4 at 21:58.
【 Securing Power Supply, Starting Restoration Work 】 - Securing Power Supply, Starting Restoration Work]
＜ Securing Power Supply Vehicle ＞
・ Corporate Distribution Department ordered branch offices to secure high and low ? Corporate Distribution Department ordered branch offices to secure high and low
voltage power supply vehicles and confirm driving route to Fukushima Diichi NPS. voltage power supply vehicles and confirm driving route to Fukushima Diichi NPS.
・ Although high and low voltage power supply vehicles headed to Fukushima Daiichi, ? Although high and low voltage power supply vehicles headed to Fukushima Daiichi,
Temporary Batteries were used to Temporary Batteries were used to
supply power to instrumentation supply power to instrumentation
Checking indicators with flashlight Checking indicators with flashlight
Page 4 Page 4
they were not able to drive up to the site fast enough because of damages of roads they were not able to drive up to the site fast enough because of damages of roads
and traffic jam . It was considered to transport the power supply vehicles by and traffic jam. It was considered to transport the power supply vehicles by
choppers of the Self Defense Force, but it turned out that the weight of the vehicles choppers of the Self Defense Force, but it turned out that the weight of the vehicles
were too heavy to carry. TEPCO requested Tohoku Electric Power Company to were too heavy to carry. TEPCO requested Tohoku Electric Power Company to
dispatch power supply vehicles to Fukushima Daiichi NPS. dispatch power supply vehicles to Fukushima Daiichi NPS.

・ As a result of equipment soundness check, it turned out that breakers were ? As a result of equipment soundness check, it turned out that breakers were
dropped and not usable in the switchyard and off-site power would not be dropped and not usable in the switchyard and off-site power would not be
restored soon. Also DGs were not operable and difficult to be restored soon restored soon. Also DGs were not operable and difficult to be restored soon
because they were submerged. It was concluded that power restoration using because they were submerged. It was concluded that power restoration using
power supply vehicles were necessary. power supply vehicles were necessary.
・ Visual inspections for inundation status and damages on exterior and insulation ? Visual inspections for inundation status and damages on exterior and insulation
resistance tests were conducted on the power panels (M/C and P/C) in the turbine resistance tests were conducted on the power panels (M / C and P / C) in the turbine
buildings (part of them are not in the turbine building). It was confirmed that all of the buildings (part of them are not in the turbine building). It was confirmed that all of the
M/C and P/C at Units 1 and 3 was inoperable, all of the M/C at Unit 2 was also M / C and P / C at Units 1 and 3 was inoperable, all of the M / C at Unit 2 was also
inoperable, part of P/C at Unit 2 was operable. (later we confirmed 4 out of 7 P/Cs inoperable, part of P / C at Unit 2 was operable. (later we confirmed 4 out of 7 P / Cs
were operable.) were operable.)

・ The site engines decided to connect power supply vehicles to the primary side of a ? The site engines decided to connect power supply vehicles to the primary side of a
power transformer (6.9kV/480V) in a P/C at Unit 2 to have 480 V to use SLC pumps. power transformer (6.9kV/480V) in a P / C at Unit 2 to have 480 V to use SLC pumps.
・ Considering distance to the P/C of Unit 2 and workability for laying cables, the ? Considering distance to the P / C of Unit 2 and workability for laying cables, the
power supply vehicle was set at the side of the turbine building and cable was power supply vehicle was set at the side of the turbine building and cable was
laid from the equipment hatch of the turbine building to the P/C in the north laid from the equipment hatch of the turbine building to the P / C in the north
side of the first floor of the building. The distance was about 200 m. side of the first floor of the building. The distance was about 200 m.
・ The cable laid in the building was carried in by a 4-ton unic truck. This cable was ? The cable laid in the building was carried in by a 4-ton unic truck. This cable was
stored by an on-site contractor for outage works. stored by an on-site contractor for outage works.
＜ Arrival of Power Supply Vehicles ＞
・ Power supply vehicles of Tohoku EPC and TEPCO arrived at the site during midnight ? Power supply vehicles of Tohoku EPC and TEPCO arrived at the site during midnight
of March 11 and early morning of March 12. of March 11 and early morning of March 12.
・ In cable connection, TEPCO's power supply vehicles were given priority. ? In cable connection, TEPCO's power supply vehicles were given priority.
＜ Cable Laying and Connection ＞
・ Cable in the building was more than 10 cm ? Cable in the building was more than 10 cm
diameter, about 200m long and weigh more than diameter, about 200m long and weigh more than
1 ton. Usually, laying this kind of cable takes 1 ton. Usually, laying this kind of cable takes
considerable days using machine but 40 TEPCO considerable days using machine but 40 TEPCO
personnel laid the cable in 4, 5 hours by hand . personnel laid the cable in 4, 5 hours by hand.
Sagging of Road Sagging of Road
Page 5 Page 5
・ It was very difficult to work steadily because of extremely bad working condition ? It was very difficult to work steadily because of extremely bad working condition
such as dark place, water puddle by the tsunami, debris and lost manhole lids. such as dark place, water puddle by the tsunami, debris and lost manhole lids.
It was necessary and quite a challenge to look for cable penetration in the dark and It was necessary and quite a challenge to look for cable penetration in the dark and
make cable route by destroying doors. Also, cable work was suspended by make cable route by destroying doors. Also, cable work was suspended by
evacuation with continued Tsunami Alarm and many aftershocks. evacuation with continued Tsunami Alarm and many aftershocks.
・ Cable terminal connection to P/C was completed only a few engineers, usually this ? Cable terminal connection to P / C was completed only a few engineers, usually this
takes several hours. takes several hours.
・ Though it was necessary to maintain communication between the field and the site ? Though it was necessary to maintain communication between the field and the site
emergency response headquarters, the communication was almost lost in the site emergency response headquarters, the communication was almost lost in the site
and had to walk to locations where communication was possible , very time and had to walk to locations where communication was possible, very time
consuming for the emergency situation. consuming for the emergency situation.
・ At 15:30, cable connection between the primary side of the P/C at Unit 2 and ? At 15:30, cable connection between the primary side of the P / C at Unit 2 and
the high voltage power supply vehicle was completed . Power was supplied just the high voltage power supply vehicle was completed. Power was supplied just
short of the SLC pump. However, at 15:36, Unit 1 exploded and debris by the short of the SLC pump. However, at 15:36, Unit 1 exploded and debris by the
explosion hit and damaged the cable, then the high voltage power supply explosion hit and damaged the cable, then the high voltage power supply
vehicle automatically stopped. Field work was suspended and everyone vehicle automatically stopped. Field work was suspended and everyone
evacuated to Anti-Seismic Building (TSC Building). evacuated to Anti-Seismic Building (TSC Building).
【 Confirmation of Water Injection to RPV 】 - Confirmation of Water Injection to RPV]

・ In MCR, operators found indication light of MO-3A and MO-2A after temporary ? In MCR, operators found indication light of MO-3A and MO-2A after temporary
restoration of DC power. The indicators showed the valves were closed. Then an restoration of DC power. The indicators showed the valves were closed. Then an
operator opened the valves at 18:18 and confirmed the light indicated the valve operator opened the valves at 18:18 and confirmed the light indicated the valve
status from close to open. Also steam generation was confirmed after the valve status from close to open. Also steam generation was confirmed after the valve
operation. operation.
・ At 18:25, the operator closed the return line isolation valve (MO-3A). At 21:30, the ? At 18:25, the operator closed the return line isolation valve (MO-3A). At 21:30, the
operator opened the MO-3A and confirmed that steam was generated. operator opened the MO-3A and confirmed that steam was generated.

・ In the early morning of March 12, an operator confirmed ? In the early morning of March 12, an operator confirmed
operating status at the field(RCIC Room). Equipped with Self operating status at the field (RCIC Room). Equipped with Self
air set, flashlight and high boot. It took about an hour to go air set, flashlight and high boot. It took about an hour to go
to and back from the RCIC room. Usually this takes only 10 to and back from the RCIC room. Usually this takes only 10
minutes but at that time, there were still concerns of minutes but at that time, there were still concerns of
aftershocks and tsunami and putting on/off the self air set aftershocks and tsunami and putting on / off the self air set
took extra time. took extra time.
・ In RCIC room, there was a water puddle and it's depth was ? In RCIC room, there was a water puddle and it's depth was
Self Air Set Self Air Set
Page 6 Page 6
about the height of the boots. Faint metallic sound was heard but the operator was about the height of the boots. Faint metallic sound was heard but the operator was
not able to check the rotating part. He returned to the MCR but was not able to not able to check the rotating part. He returned to the MCR but was not able to
determine whether RCIC was operating or not. Since PHS was not functioning, he determine whether RCIC was operating or not. Since PHS was not functioning, he
reported the situation after getting back to the MCR reported the situation after getting back to the MCR
・ Then at 2:00, the operator went there again. Water puddle increased and the ? Then at 2:00, the operator went there again. Water puddle increased and the
operating status of RCIC was not able to see in the RCIC room. The operator operating status of RCIC was not able to see in the RCIC room. The operator
determined RCIC was in operation by checking reactor pressure and RCIC determined RCIC was in operation by checking reactor pressure and RCIC
discharge pressure at the instrument rack of RCIC and RCIC discharge pressure discharge pressure at the instrument rack of RCIC and RCIC discharge pressure
was high. After he reported this after returning to the MCR then reported to the site was high. After he reported this after returning to the MCR then reported to the site
emergency response headquarters at 2:55. emergency response headquarters at 2:55.
Page 7 Page 7
Time line sequence of major events following earthquake to May 12 Time line sequence of major events following earthquake to May 12
th th
(Sat) for (Sat) for
Unit 1 at Fukushima Daiichi Nuclear Power Station Unit 1 at Fukushima Daiichi Nuclear Power Station
This report is based on various information as well as testimonies received from This report is based on various information as well as testimonies received from
relevant people up to this point in time. Further announcements may be released upon relevant people up to this point in time. Further announcements may be released upon
the discovery of new information identified during the investigation. the discovery of new information identified during the investigation.
March 11 March 11
th th
, 2011 2011
2:46 pm The reactor was scrammed automatically after the Tohoku Chihou 2:46 pm The reactor was scrammed automatically after the Tohoku Chihou
Taiheiyou Oki Earthquake occurred. The third state of emergency was Taiheiyou Oki Earthquake occurred. The third state of emergency was
announced. announced.
2:47 pm The main turbine was suspended automatically. Diesel generator for emergency 2:47 pm The main turbine was suspended automatically. Diesel generator for emergency
started automatically. started automatically.
2:52 pm The isolation condenser (hereafter referred as “IC”) started automatically. 2:52 pm The isolation condenser (hereafter referred as "IC") started automatically.
3:02 pm Subcritical state of reactor was confirmed. 3:02 pm Subcritical state of reactor was confirmed.
Approx. 3:03 pm IC was suspended manually to control the reactor pressure. The control Approx. 3:03 pm IC was suspended manually to control the reactor pressure. The control
of the reactor pressure by IC was started. of the reactor pressure by IC was started.
3:06 pm Headquarter for major disaster countermeasures was established in the head 3:06 pm Headquarter for major disaster countermeasures was established in the head
office to grasp situations of damages and to restore the outage due to the office to grasp situations of damages and to restore the outage due to the
earthquake. earthquake.
3:27 pm The first tsunami hit the Muclear Power Station. 3:27 pm The first tsunami hit the Muclear Power Station.
3:35 pm The second tsunami hit the Muclear Power Station. 3:35 pm The second tsunami hit the Muclear Power Station.
3:37 pm All the alternating-current sources were stopped. 3:37 pm All the alternating-current sources were stopped.
3:42 pm It was decided that a specific incident stipulated in Article 10, Clause 1 of 3:42 pm It was decided that a specific incident stipulated in Article 10, Clause 1 of
the Act on Special Measures Concerning Nuclear Emergency Preparedness the Act on Special Measures Concerning Nuclear Emergency Preparedness
has occurred, and relevant governments were notified of the incident. has occurred, and relevant governments were notified of the incident.
3:42 pm 3:42 pm
The first Level Emergency” was declared, and Emergency Response The first Level Emergency "was declared, and Emergency Response
Headquarter was established (as Joint Headquarter with Headquarter for major Headquarter was established (as Joint Headquarter with Headquarter for major
disaster countermeasures mentioned above). disaster countermeasures mentioned above).
4:36 pm It was decided that a specific incident (impossibility of water injection by 4:36 pm It was decided that a specific incident (impossibility of water injection by
Emergency Core Cooling System) stipulated in article 15, clause 1 of Act on Emergency Core Cooling System) stipulated in article 15, clause 1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness has occurred, Special Measures Concerning Nuclear Emergency Preparedness has occurred,
because the reactor water level and the status of water injection was not because the reactor water level and the status of water injection was not
confirmed. The relevant governments were notified of the incident at 16:45. confirmed. The relevant governments were notified of the incident at 16:45.
4:36 pm “The second Level Emergency” was declared. 4:36 pm "The second Level Emergency" was declared.
4:45 pm It was decided to cancel a specific incident (impossibility of water injection by 4:45 pm It was decided to cancel a specific incident (impossibility of water injection by
Page 8 Page 8
Emergency Core Cooling System) stipulated in article 15, clause 1 of Act on Special Emergency Core Cooling System) stipulated in article 15, clause 1 of Act on Special
Measures Concerning Nuclear Emergency Preparedness, because the reactor Measures Concerning Nuclear Emergency Preparedness, because the reactor
water level was confirmed. The relevant governments were notified of the water level was confirmed. The relevant governments were notified of the
cancellation at 16:55. cancellation at 16:55.
5:07 pm It was decided that a specific incident (impossibility of water injection by 5:07 pm It was decided that a specific incident (impossibility of water injection by
Emergency Core Cooling System) stipulated in article 15, clause 1 of Act on Special Emergency Core Cooling System) stipulated in article 15, clause 1 of Act on Special
Measures Concerning Nuclear Emergency Preparedness has occurred, because Measures Concerning Nuclear Emergency Preparedness has occurred, because
the reactor water level was not confirmed again. The relevant governments were the reactor water level was not confirmed again. The relevant governments were
notified of the cancellation at 17:12. notified of the cancellation at 17:12.
5:12 pm General Manager of Power station directed to start consideration of 5:12 pm General Manager of Power station directed to start consideration of
measure to injecting water to Reactor using the Fire Protection System which measure to injecting water to Reactor using the Fire Protection System which
is installed as a measure for accident management and fire fighter. is installed as a measure for accident management and fire fighter.
5:30 pm Diesel-powered fire pump activated. (idle activity) 5:30 pm Diesel-powered fire pump activated. (Idle activity)
6:18 pm Operated to open IC return line of isolation valve (MO-3A) and IC steam line of 6:18 pm Operated to open IC return line of isolation valve (MO-3A) and IC steam line of
isolation valve (MO-2A). Confirmed steam rising out. isolation valve (MO-2A). Confirmed steam rising out.
6:25 pm Operated to close IC return line of isolation valve (MO-3A) 6:25 pm Operated to close IC return line of isolation valve (MO-3A)
8:49 pm Temporary lighting was turned on in the main control room. 8:49 pm Temporary lighting was turned on in the main control room.
8:50 pm Government of Fukushima prefecture ordered to evacuate for the residents within 8:50 pm Government of Fukushima prefecture ordered to evacuate for the residents within
2km radius from Fukushima Daiichi Nuclear Power Station. 2km radius from Fukushima Daiichi Nuclear Power Station.
9:19 pm Water level in the reactor found out. Top of active fuel (hereinafter “TAF”) +200mm 9:19 pm Water level in the reactor found out. Top of active fuel (hereinafter "TAF") +200 mm
9:23 pm The Prime Minister ordered the residents to evacuate within 3km radius from 9:23 pm The Prime Minister ordered the residents to evacuate within 3km radius from
Fukushima Daiichi Nuclear Power Station, and ordered the residents to stay Fukushima Daiichi Nuclear Power Station, and ordered the residents to stay
indoors within 3km to 10 km radius. indoors within 3km to 10 km radius.
9:30 pm Operated to open IC return line of isolation valve (MO-3A). Confirmed steam 9:30 pm Operated to open IC return line of isolation valve (MO-3A). Confirmed steam
rising out. rising out.
9:51 pm Prohibited entry into the reactor building as the radioactive dose increased. 9:51 pm Prohibited entry into the reactor building as the radioactive dose increased.
10:00 pm Confirmed water level in the reactor was TAF+550 mm. Reported it to the 10:00 pm Confirmed water level in the reactor was TAF +550 mm. Reported it to the
authorities at 10:20 pm. authorities at 10:20 pm.
11:00 pm Reported to the authorities as a result of survey at 11:40 pm, an increase of 11:00 pm Reported to the authorities as a result of survey at 11:40 pm, an increase of
radioactive dose in the turbine building (1.2mSv/h in front of the double doors in radioactive dose in the turbine building (1.2mSv / h in front of the double doors in
the North on the first floor of the turbine building, 0.5mSv/h in front of the double the North on the first floor of the turbine building, 0.5mSv / h in front of the double
doors in the South on the first floor of the turbine building) doors in the South on the first floor of the turbine building)
March 12 March 12
th th
, 2011 2011
0:06 am The General Manager of power station instructed to prepare to vent the Primary 0:06 am The General Manager of power station instructed to prepare to vent the Primary
Containment Vessel (hereinafter “the Vent”) as the drywell (hereinafter “D/W”) Containment Vessel (hereinafter "the Vent") as the drywell (hereinafter "D / W")
pressure was likely to exceed 600kPa abs and there was a possibility to pressure was likely to exceed 600kPa abs and there was a possibility to
Page 9 Page 9
implement the Vent. implement the Vent.
0:30 am Government confirmed the completion of evacuation of the residents (3km radius 0:30 am Government confirmed the completion of evacuation of the residents (3km radius
of the periphery of Fukushima Daiichi Nuclear Power Station in Futaba Town and of the periphery of Fukushima Daiichi Nuclear Power Station in Futaba Town and
Okuma Town, reconfirmed at 1:45 am) Okuma Town, reconfirmed at 1:45 am)
0:49 am As D/W pressure was likely to exceed 600kPa abs, it was judged to a specific 0:49 am As D / W pressure was likely to exceed 600kPa abs, it was judged to a specific
incident (extraordinary increase of pressure in the Primary Containment Vessel) incident (extraordinary increase of pressure in the Primary Containment Vessel)
occurred, based on Article 15, clause 1 of Act on Special Measures Concerning occurred, based on Article 15, clause 1 of Act on Special Measures Concerning
Nuclear Emergency Preparedness. Reported it to the authorities at 0:55 am Nuclear Emergency Preparedness. Reported it to the authorities at 0:55 am
1:30 am Proposed and obtained agreement to implement the Vent at Unit1 and Unit2 to 1:30 am Proposed and obtained agreement to implement the Vent at Unit1 and Unit2 to
prime minister, minister of economy, trade and industry and Nuclear and prime minister, minister of economy, trade and industry and Nuclear and
Industrial Safety Agency. Industrial Safety Agency.
1:48 am Confirmed that diesel-powered fire pump stopped because of defects. Started to 1:48 am Confirmed that diesel-powered fire pump stopped because of defects. Started to
consider connecting the water inlet of the Fire Protection Line with a fire engine. consider connecting the water inlet of the Fire Protection Line with a fire engine.
2:47 am Reported to the authorities, D/W pressure reached 840 kPa abs at 2:30 am 2:47 am Reported to the authorities, D / W pressure reached 840 kPa abs at 2:30 am
3:06 am Press conference about the Vent implementation was held. 3:06 am Press conference about the Vent implementation was held.
3:33 am Reported to the authorities, the result of evaluation of radioactive exposure in 3:33 am Reported to the authorities, the result of evaluation of radioactive exposure in
the case that the Vent was implemented. the case that the Vent was implemented.
4:55 am Confirmed the radioactive dose in the power station rised (0.069μSv /h 4:55 am Confirmed the radioactive dose in the power station rised (0.069μSv / h
(4:00) => 0.59μSv /h(4:23) around main gate) and reported it to the authorities. (4:00) => 0.59μSv / h (4:23) around main gate) and reported it to the authorities.
5:14 am As the radioactive dose increased in the premise of the power plant and the D/W 5:14 am As the radioactive dose increased in the premise of the power plant and the D / W
pressure tended to decrease, it was judged that “radioactive material leakage to pressure tended to decrease, it was judged that "radioactive material leakage to
the exterior” occurred. Reported it to the authorities. the exterior "occurred. Reported it to the authorities.
5:44 am The Prime Minister ordered the residents within 10km radius of Fukushima 5:44 am The Prime Minister ordered the residents within 10km radius of Fukushima
Daiichi Nuclear Power Station to evacuate. Daiichi Nuclear Power Station to evacuate.
5:46 am The fire engine started plain water injection into the reactor through the Fire 5:46 am The fire engine started plain water injection into the reactor through the Fire
Protection Line. Protection Line.
6:33 am Confirmed that consideration was being given to the evacuation from Okuma 6:33 am Confirmed that consideration was being given to the evacuation from Okuma
Town to an area located in Miyakoji. Town to an area located in Miyakoji.
6:50 am There was an order of The Minister of Economy, Trade and Industry to implement 6:50 am There was an order of The Minister of Economy, Trade and Industry to implement
the Vent based on the laws and ordinances (manual Vent). the Vent based on the laws and ordinances (manual Vent).
7:11 am The Prime Minister arrived at Fukushima Daiichi Nuclear Power Station. 7:11 am The Prime Minister arrived at Fukushima Daiichi Nuclear Power Station.
8:03 am The General Manager of the power station instructed to aim to implement the 8:03 am The General Manager of the power station instructed to aim to implement the
Vent at 9 am. Vent at 9 am.
8:04 am The Prime Minister left Fukushima Daiichi Nuclear Power Station. 8:04 am The Prime Minister left Fukushima Daiichi Nuclear Power Station.
8:27 am Confirmed the information that part of the residents in Okuma Town have not 8:27 am Confirmed the information that part of the residents in Okuma Town have not
been able to evacuate yet. been able to evacuate yet.
Page 10 Page 10
8:37 am Reported to the Fukushima Prefectural Government that we were preparing for 8:37 am Reported to the Fukushima Prefectural Government that we were preparing for
the start of the Vent around 9 am. Coordination was done with Fukushima the start of the Vent around 9 am. Coordination was done with Fukushima
Prefectural government to implement vent operations subsequent to the Prefectural government to implement vent operations subsequent to the
evacuation. evacuation.
9:03 am Confirmed that the evacuation of Okuma Town (Kuma area) residents had been 9:03 am Confirmed that the evacuation of Okuma Town (Kuma area) residents had been
completed. completed.
9:04 am Person on duty left for the scene in order to implement the Vent. 9:04 am Person on duty left for the scene in order to implement the Vent.
9:05 am Announcement of implementation of the Vent. 9:05 am Announcement of implementation of the Vent.
Approx. 9:15 am Manually opened the vent valve (MO valve) of Primary Containment Approx. 9:15 am Manually opened the vent valve (MO valve) of Primary Containment
Vessel (hereinafter ”PCV”) Vessel (hereinafter "PCV")
9:30 am An operation of the vent valve (A/O valve) of the suppression chamber 9:30 am An operation of the vent valve (A / O valve) of the suppression chamber
(hereinafter “S/C”) was tried but given up due to high radioactive dose. (Hereinafter "S / C") was tried but given up due to high radioactive dose.
9:53 am Reported to the authorities, an evaluation result of exposure in the case that the 9:53 am Reported to the authorities, an evaluation result of exposure in the case that the
Vent was implemented. Vent was implemented.
10:17 am S/C vent valve (AO valve) was opened in the central control room (with 10:17 am S / C vent valve (AO valve) was opened in the central control room (with
expectation of residual pressure of instrumentation air system). expectation of residual pressure of instrumentation air system).
10:40 am As the radioactive dose increased at the main gate and the monitoring post, it 10:40 am As the radioactive dose increased at the main gate and the monitoring post, it
was judged that there was a high possibility that radioactive materials were was judged that there was a high possibility that radioactive materials were
released because of the Vent. released because of the Vent.
11:15 am Confirmed that there was a possibility that the Vent was not fully effective as the 11:15 am Confirmed that there was a possibility that the Vent was not fully effective as the
radioactive dose decreased. radioactive dose decreased.
11:39 am Reported to the authorities, that radioactive exposure of an employee of Tepco 11:39 am Reported to the authorities, that radioactive exposure of an employee of Tepco
exceeded 100 mSv (106.30 mSv), who had entered into the reactor building for exceeded 100 mSv (106.30 mSv), who had entered into the reactor building for
the Vent operation. the Vent operation.
2:30 pm When setting up a makeshift air compressor around 2 pm in order to operate the 2:30 pm When setting up a makeshift air compressor around 2 pm in order to operate the
S/C vent valve (AO valve), we confirmed that the D/W pressure decreased and S / C vent valve (AO valve), we confirmed that the D / W pressure decreased and
judged that the “release of radioactive materials” occurred by the Vent. We judged that the "release of radioactive materials" occurred by the Vent. We
reported this information to the authorities at 3:18 pm. reported this information to the authorities at 3:18 pm.
2:53 pm 80 tons (accumulated total) plain water had just been poured into the reactor by 2:53 pm 80 tons (accumulated total) plain water had just been poured into the reactor by
the fire engines. the fire engines.
2:54 pm The General Manager of the power plant instructed to implement an injection of 2:54 pm The General Manager of the power plant instructed to implement an injection of
seawater into the reactor. seawater into the reactor.
3:18 pm Reported the following items to the authorities: recovery work of standby liquid 3:18 pm Reported the following items to the authorities: recovery work of standby liquid
control system was in progress, the standby liquid control pump was scheduled to control system was in progress, the standby liquid control pump was scheduled to
be activated and boric-acid solution was scheduled to be injected into the reactor be activated and boric-acid solution was scheduled to be injected into the reactor
as soon as those were ready, furthermore, seawater was hereafter scheduled to as soon as those were ready, furthermore, seawater was hereafter scheduled to
Page 11 Page 11
be injected into the reactor through the Fire Protection Line as soon as that was be injected into the reactor through the Fire Protection Line as soon as that was
ready. ready.
3:36 pm All the preparations were complete for the injection of boric-acid solution through 3:36 pm All the preparations were complete for the injection of boric-acid solution through
the standby liquid control system, upon power restoration by use of a power the standby liquid control system, upon power restoration by use of a power
supply car. supply car.
3:36 pm An explosion occurred in the reactor building. Power- supply facility for the 3:36 pm An explosion occurred in the reactor building. Power-supply facility for the
standby liquid control system and pre-arranged hose for seawater injection were standby liquid control system and pre-arranged hose for seawater injection were
damaged and out of commission. damaged and out of commission.
4:27 pm Measuring the dose exceeding 500μSv /h at the monitoring post (1,015μSv /h), 4:27 pm Measuring the dose exceeding 500μSv / h at the monitoring post (1,015 μSv / h),
judged as a specific incident occurred based on article 15, clause 1 of Act on judged as a specific incident occurred based on article 15, clause 1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness (radiation dose Special Measures Concerning Nuclear Emergency Preparedness (radiation dose
increased abnormally at the boundary of the site). Reported this information to increased abnormally at the boundary of the site). Reported this information to
the authority. the authority.
6:05 pm The information was shared among the head office and the power station that 6:05 pm The information was shared among the head office and the power station that
there was an order of The Minister of Economy, Trade and Industry based on the there was an order of The Minister of Economy, Trade and Industry based on the
laws and ordinances. laws and ordinances.
6:25 pm The Prime Minister ordered the residents within 20km radius from Fukushima 6:25 pm The Prime Minister ordered the residents within 20km radius from Fukushima
Daiichi Nuclear Power Station to evacuate. Daiichi Nuclear Power Station to evacuate.
7:04 pm Seawater was started to be injected into the reactor by the fire engines through 7:04 pm Seawater was started to be injected into the reactor by the fire engines through
the Fire Protection Line. the Fire Protection Line.
8:45 pm Boric-acid solution was started to be mixed with seawater and injected into the 8:45 pm Boric-acid solution was started to be mixed with seawater and injected into the
reactor. reactor.
End End
Page 12 Page 12
Fukushima Daiichi Nuclear Power Station Unit 1 Fukushima Daiichi Nuclear Power Station Unit 1
Alternative Water Injection Alternative Water Injection
This document is a summary of the latest information obtained through information and This document is a summary of the latest information obtained through information and
interviews with personnel concerned. We will continue investigation and announce when interviews with personnel concerned. We will continue investigation and announce when
new facts and findings are obtained. new facts and findings are obtained.
○Activities after Determination and Reporting of Loss of ECCS at 16:36 on ○ Activities after Determination and Reporting of Loss of ECCS at 16:36 on
March11. March11.
【 Planning for Alternative Injection 】 Planning for Alternative Injection]]
・ Frequent evacuation and suspension of field work due to continued ? Frequent evacuation and suspension of field work due to continued
tsunami alerts and aftershocks. Working without lighting and tsunami alerts and aftershocks. Working without lighting and
communication measures and significant amount of debris and soil by communication measures and significant amount of debris and soil by
the tsunami made the field operation very difficult . the tsunami made the field operation very difficult.
・ At 17:12, the site emergency response headquarters started to discuss ? At 17:12, the site emergency response headquarters started to discuss
using the alternative water injection which was put in place as an using the alternative water injection which was put in place as an
accident management measures (AM) and the fire protection tanks and accident management measures (AM) and the fire protection tanks and
fire engines deployed after Niigataken Chuetsuoki Earthquake . fire engines deployed after Niigataken Chuetsuoki Earthquake.
・ Meanwhile, operators checked measures for alternative water injection with ? Meanwhile, operators checked measures for alternative water injection with
AM procedure in the MCR and confirmed injection line to RPV then started AM procedure in the MCR and confirmed injection line to RPV then started
to use Diesel Driven Fire Pump (D/D FP). to use Diesel Driven Fire Pump (D / D FP).
・ Operators lined up alternative water injection with D/D FP and Fire ? Operators lined up alternative water injection with D / D FP and Fire
Protection line via Core Spray System , opening valves in the Core Spray Protection line via Core Spray System, opening valves in the Core Spray
lines by hand in the dark reactor building. After depressurize the RPV lines by hand in the dark reactor building. After depressurize the RPV
below 0.69 MPa, water injection through FP/CS became available. below 0.69 MPa, water injection through FP / CS became available.
・ At 17:30, D/D FP started up but in stand-by. ? At 17:30, D / D FP started up but in stand-by.
・ The restoration team of the site emergency response headquarters ? The restoration team of the site emergency response headquarters
conducted visual inspections for inundation status and damages on conducted visual inspections for inundation status and damages on
exterior and insulation resistance tests were conducted on the power exterior and insulation resistance tests were conducted on the power
panels (M/C and P/C) and found power supply equipment in Unit 1 was panels (M / C and P / C) and found power supply equipment in Unit 1 was
unable to use but one of P/Cs in Unit 2 was operable. The team made plans unable to use but one of P / Cs in Unit 2 was operable. The team made plans
to use SLC (Stand by Liquid Control) system to inject water in the RPV, since to use SLC (Stand by Liquid Control) system to inject water in the RPV, since
the SLC had high discharge pressure. Power supply for the SLC was the SLC had high discharge pressure. Power supply for the SLC was
planed to be restored by power supply vehicle via P/C in Unit 2 . planed to be restored by power supply vehicle via P / C in Unit 2.
・ Monitoring instruments in the MCR were unable to use because of ? Monitoring instruments in the MCR were unable to use because of
power outage . Then an operator entered in the dark reactor building and power outage. Then an operator entered in the dark reactor building and
Page 13 Page 13
confirmed the reactor pressure was 6.9 MPa as of 20:07. Later, water level confirmed the reactor pressure was 6.9 MPa as of 20:07. Later, water level
indicator returned its function and indicated the level was 200 mm above TAF indicator returned its function and indicated the level was 200 mm above TAF
(Top of Active Fuel) at 21:19. (Top of Active Fuel) at 21:19.
Page 14 Page 14
○Activities after Starting Consideration for Connecting Water Injection Line from ○ Activities after Starting Consideration for Connecting Water Injection Line from
Fire Engine to Fire Protection Line at 1:48 on March 12 Fire Engine to Fire Protection Line at 1:48 on March 12
【 Diesel Driven Fire Pump (D/D FP) 】 [Diesel Driven Fire Pump (D / D FP)]
・ At 1:48, an Operator found D/D FP was stopped which had been on stand by ? At 1:48, an Operator found D / D FP was stopped which had been on stand by
to inject water into the RPV. In order to start the D/D FP again, diesel fuel to inject water into the RPV. In order to start the D / D FP again, diesel fuel
was carried to the pump and fueled manually and batteries stored at an was carried to the pump and fueled manually and batteries stored at an
office of on-site contractor was carried and replaced but the pump did office of on-site contractor was carried and replaced but the pump did
not work. not work.
【 Preparation for Water Injection from Fire Engine 】 Preparation for Water Injection from Fire Engine []
・ It was impossible to use filtered water as water source for RPV because fire ? It was impossible to use filtered water as water source for RPV because fire
hydrant was damaged and water was spewed. To have sufficient hydrant was damaged and water was spewed. To have sufficient
amount of filtered water for the amount of filtered water for the
injection, valves were closed around injection, valves were closed around
the area . Also other water sources were the area. Also other water sources were
looked for and the fire protection tank looked for and the fire protection tank
was confirmed to be available. was confirmed to be available.
・ One fire engine was made ready for injection to ? One fire engine was made ready for injection to
the RPV. Other two fire engines were the RPV. Other two fire engines were
unavailable, for one was failed by the tsunami and the other was not able to unavailable, for one was failed by the tsunami and the other was not able to
move from the area near Unit 5/6. Damages on the road and debris by the move from the area near Unit 5 / 6. Damages on the road and debris by the
tsunami divided the access route between Units 1 -- 4 side and Units 5,6 tsunami divided the access route between Units 1 - 4 side and Units 5,6
side. side.
・ There were a lot of obstacles to deploy the ? There were a lot of obstacles to deploy the
available fire engine close to Unit 1. Tank available fire engine close to Unit 1. Tank
swept by the tsunami blocked a road in swept by the tsunami blocked a road in
front of the old-administration building and front of the old-administration building and
the road was impassable. The gate at the the road was impassable. The gate at the
physical protection headquarters lost physical protection headquarters lost
power and did not open. The restoration power and did not open. The restoration
team of the site emergency response headquarters looked for rout in team of the site emergency response headquarters looked for rout in
the site, then got access for the fire engine by breaking a lock at the the site, then got access for the fire engine by breaking a lock at the
gate between Units 2 and 3. gate between Units 2 and 3.
・ As for the fire engine, measures were studied to inject water via Fire ? As for the fire engine, measures were studied to inject water via Fire
Protection line. Also additional fire engines and water transportation by the Protection line. Also additional fire engines and water transportation by the
Tank moved by Tsunami Tank moved by Tsunami
Sagged Road in the Site Sagged Road in the Site
Page 15 Page 15
SDF were considered. SDF were considered.
・ Reactor pressure was 0.8 MPa at 2:4. ? Reactor pressure was 0.8 MPa at 2:4.
【 Restoration of SLC system 】 [Restoration of SLC system]
・ Power supply and pump in SLC system were not affected by the tsunami. ? Power supply and pump in SLC system were not affected by the tsunami.
Since the SLC has high-head pump, power supply was being restored by the Since the SLC has high-head pump, power supply was being restored by the
power supply vehicle. power supply vehicle.
○Activities after Starting Water Injection into the RPV at 5:46, on 3/12 ○ Activities after Starting Water Injection into the RPV at 5:46, on 3 / 12
【 Prepare/Continue Freshwater Injection 】 - Prepare / Continue Freshwater Injection]
・ A fire engine in the garage moved to Unit 1. At first, the fire engine pumped ? A fire engine in the garage moved to Unit 1. At first, the fire engine pumped
up water at the fire protection tank then drove close to the reactor up water at the fire protection tank then drove close to the reactor
building and injected water through FP line, this operation was building and injected water through FP line, this operation was
repeated because it was considered the elevation at the fire protection tank repeated because it was considered the elevation at the fire protection tank
was too low and the discharge pressure of the pump in the fire engine was was too low and the discharge pressure of the pump in the fire engine was
not enough. It took significant amount of time to drive the fire engine not enough. It took significant amount of time to drive the fire engine
carefully under the half-collapsed building . carefully under the half-collapsed building.
・ It took time to go back and forth the fire engine between the fire ? It took time to go back and forth the fire engine between the fire
protection tank and the reactor building , after some trial and error , protection tank and the reactor building, after some trial and error,
continuous water injection started by using a horse equipped on the fire continuous water injection started by using a horse equipped on the fire
engine to directly connect the fire protection tank and the fire protection line engine to directly connect the fire protection tank and the fire protection line
to the RPV. to the RPV.
・ Additional fire engine arrived to the site and this one was used to transport ? Additional fire engine arrived to the site and this one was used to transport
freshwater from the fire protection tank at Unit 3 to the fire protection tank at freshwater from the fire protection tank at Unit 3 to the fire protection tank at
Unit 1 repeatedly . The fire protection tank had room for only one horse, Unit 1 repeatedly. The fire protection tank had room for only one horse,
so water injection to the RPV had to be suspended when the second so water injection to the RPV had to be suspended when the second
fire engine came to replenish the water in the tank . fire engine came to replenish the water in the tank.
【 Preparation for Seawater Injection and SLC 】 Preparation for Seawater Injection and SLC []
・ Because of the limitation of the amount of freshwater in the fire protection ? Because of the limitation of the amount of freshwater in the fire protection
tanks, preparation for seawater injection was tanks, preparation for seawater injection was
initiated. initiated.
・ Instead of taking seawater directly from the ? Instead of taking seawater directly from the
sea, the backwash pit where seawater was sea, the backwash pit where seawater was
filled by the tsunami was selected as a supply filled by the tsunami was selected as a supply
souse taking the road conditions in the site souse taking the road conditions in the site
Injection by Fire Engine Injection by Fire Engine
Page 16 Page 16
and distance from Unit 1 into consideration. and distance from Unit 1 into consideration.
・ At 14:53, 80,000 Litter of fresh water had been injected to the RPV. ? At 14:53, 80,000 Litter of fresh water had been injected to the RPV.
・ At 14:54, Site Vice President directed to prepare for seawater injection to the ? At 14:54, Site Vice President directed to prepare for seawater injection to the
RPV. Since freshwater in the fire protection tank at Unit 1 was drying up, RPV. Since freshwater in the fire protection tank at Unit 1 was drying up,
freshwater was transported from other fire protection tanks in a quick pace freshwater was transported from other fire protection tanks in a quick pace
and preparation for seawater injection was moved ahead. and preparation for seawater injection was moved ahead.
・ Around 15:30, cable connection between the primary side of P/C at Unit ? Around 15:30, cable connection between the primary side of P / C at Unit
2 and high-voltage power supply vehicle was completed. Power was 2 and high-voltage power supply vehicle was completed. Power was
supplied just short of the SLC pump. supplied just short of the SLC pump.
・ Lining up of seawater injection was completed with three fire engines ? Lining up of seawater injection was completed with three fire engines
connected in series to have sufficient head. Seawater was taken from the connected in series to have sufficient head. Seawater was taken from the
backwash pit at Unit 3. backwash pit at Unit 3.
Page 17 Page 17
・ At 15:36, Unit 1 reactor building exploded. ? At 15:36, Unit 1 reactor building exploded.
? Workers at the field evacuated, rescued ? Workers at the field evacuated, rescued
and transported the injured. (TEPCO: 3, and transported the injured. (TEPCO: 3,
Contractor: 2) Contractor: 2)
? To verify safety and see effect of the ? To verify safety and see effect of the
explosion, field survey and walk down explosion, field survey and walk down
were conducted. (Status of fire engines, were conducted. (Status of fire engines,
damages to the buildings and smoking damages to the buildings and smoking
etc.) Fire engines maintained their etc.) Fire engines maintained their
function though windshield was broken. function though windshield was broken.
? As for the SLC pump, ballistic fragments by the explosion ? As for the SLC pump, ballistic fragments by the explosion
damaged cable damaged the cable and high-voltage power damaged cable damaged the cable and high-voltage power
supply vehicle stopped automatically. supply vehicle stopped automatically.
? The hoses prepared for seawater injection was also damaged. ? The hoses prepared for seawater injection was also damaged.
・ ?
It was impossible to resume restoration work until evacuation, It was impossible to resume restoration work until evacuation,
confirmation of the safety of workers and the field were completed. confirmation of the safety of workers and the field were completed.
・ Workers removed debris, collected hoses from outdoor fire hydrants ? Workers removed debris, collected hoses from outdoor fire hydrants
and laid hoses again to seawater injection. Because the debris near and laid hoses again to seawater injection. Because the debris near
Unit 1 had high radiation, all these activities were monitored by Unit 1 had high radiation, all these activities were monitored by
radioactive protection technicians. radioactive protection technicians.
・ At 19:04, seawater injection started using the fire protection line and fire ? At 19:04, seawater injection started using the fire protection line and fire
engines. engines.
Explosion of Unit 1 Reactor Building Explosion of Unit 1 Reactor Building
Page 18 Page 18
The status of administration main building The status of administration main building
Unit 1, Fukushima Daiichi Nuclear Power Station Unit 1, Fukushima Daiichi Nuclear Power Station
The operation of the vent valve at the PCV The operation of the vent valve at the PCV
This summarizes the facts based on info and testimony available to date. We will This summarizes the facts based on info and testimony available to date. We will
continue the investigation. If new facts are confirmed at a later date, we will announce continue the investigation. If new facts are confirmed at a later date, we will announce
again. again.
? Activities after report “At 4:36 PM on March 11, Determination and Report of ? Activities after report "At 4:36 PM on March 11, Determination and Report of
ECCS's inability to inject water” ECCS's inability to inject water "
・ We were endeavoring to restore indicators in the Main Control Room. We did below ? We were endeavoring to restore indicators in the Main Control Room. We did below
works. works.
【 Preparation work for opening the vent valve 】
・ At the Main Control Room we submitted the accident management (“AM”) operation
procedure to the chief operator and confirmed the procedure. Also, we began
confirming the name and place of valves required for opening the vent valves
(“Vent”) using the checklist for valves.
・ Generation team of Power station emergency response headquarters (“PSER”)
began reviewing the AM operation procedure and checking the Vent procedures
without electricity.
・ Restoration team of PSER, during aftershocks,
went to the administration main building
(entrance prohibited) to get drawings in order
to check the model and structure of the S/C
vent valve (AO valve) required for Vent and
open manually . At the same time, we inquired
our subcontractors. From the drawings, we
confirmed that there is a handle on the small valve of S/C vent valve (AO valve) and
could be opened manually. We notified the Main Control Room accordingly.
【 The dose at the work place began to increase 】
・ 9:51 PM， The dose at the R/B began to increase . We prohibited entry to R/B.
・ 10:00 PM, PSER have been reported that the figures by APD went up to 0.8mSv
during a very short period of time at the R/B.
・ 11:00 PM，because of the influence of increase of dose at R/B, the radiation dose
in the T/B increased. (in front of the airlock, north side, 1FL, T/B: 1.2mSv/h，in
front of the airlock, south side, 1FL, T/B: 0.5mSv/h）。
【 D/W pressure began to increase 】
Page 19 Page 19
・ 11:50PM, at the Main Control Room, Restoration team of PSER connected the
battery for the reactor water level gauge to D/W pressure gauge to check the
pressure. The pressure indicated was 600kPa abs. Reported that to PSER.
? Activities after “At 12:06 AM on March 12, D ／ W pressure may exceed 600kPa
abs. Instruction from the Station Manager to proceed with the preparation”
【 began to confirm the actual Vent procedures 】
・ At the Main Control Room we put together the piping and instrumentation diagrams,
AM procedure manual, documents such as the drawings of valves and the
whiteboard. We began confirming the actual procedures such as how to operate the
valve and sequences.
・ At 1:30 AM, we asked for permission to do Vent to Prime Minister, Minister of METI
and NISA and got approval. From Headquarters Task Force (“HTF”), we received
instruction “We would like you to do Vent by whatever ways to operate the MO
valve and AO valve. At 3:00 AM, Minister of METI and we will announce doing
Vent. After the announcement, please do Vent.”
【 continue confirmation of Vent procedures 】
・ 2:24 AM， PSER received the evaluation result of work time at the field site to do
Vent. If the atmospheric radiation is 300mSv/h, we have 17 minutes of work
time under the radiation limit for emergency response (100mSv/h) (the air in
the self-contained breathing apparatus lasts 20 minutes. Need to take iodine
tablets.)
・ 2:30 AM，D/W pressure reached 840kPa abs（the maximum operation pressure =
427kPa gauge
※ ※
） )
※528.3kPa abs（＝427kPa gage＋101.3kPa）
・ 3:45AM， HTF made the evaluation on exposure dose at the surrounding areas at
the time of Vent and shared with the power station. At the power station, in order to
measure dose in the R/B, we opened the airlock. As we saw white gaseous
substance, we instantaneously closed the airlock. We couldn't conduct dose
measurement.
・ At the Main Control Room, in preparation for Vent, we repeatedly confirmed the
sequence of operation of valves, location of valves in Torus Room, height of
valves etc. We collected as many equipments as possible required for the work.
Those are fire fighting garments, self-contained breathing apparatus, APD, survey
meter and flashlights.
・ At 4:30 AM, because of the risk of tsunami by aftershocks, PSER instructed the
Page 20 Page 20
Main Control Room to prohibit operation at the field site.
・ At 4:45 AM, PSER delivered APDs (set at 100mSv) and full face masks to the Main
Control Room. At 4:50 AM, as the worker returned to the main anti-earthquake
building was contaminated, we decided to equip, from the entrance of the main
anti-earthquake building, “full face mask + charcoal filter + B garment, C
garment or coverall” when we go to the field site . After that, at 5:00 AM, Main
Control Room was instructed to equip similarly “full face mask + charcoal filter +
B garment.
・ At the Main Control Room as the dose increased, the Chief shift operator instructed
shift operators to move to Unit 2 side with relatively lower dose.
・ At 6:33 AM，as to the status of evacuation at surrounding areas, we confirmed that
residents are planning to move from Okuma town to Miyakoji.
・ 8:03 AM, Station Chief instructed to target 9 AM to do Vent for Unit 1.
・ At the Main Control Room, we formed three teams, two persons for each (Chief
shift operator and deputy chief shift operator) because of the following
reasons: (i) it is impossible to work by one person because of complete
darkness (ii) the high anticipated dose and (iii) may need to return because of
the aftershock.
・ We confirmed the status of evacuation by residents. At 8:27 AM, TEPCO employees
dispatched to Okuma town office reported to PSER that part of Okuma town
hadn't yet evacuated.
・ At 8:37 ， we notified Fukushima prefecture that we are preparing for the
commencement of Vent from 9:00 AM. We coordinated to Vent after evacuation
is over.
・ At 9:03 AM，we confirmed that Kuma area, Okuma town finished evacuation. We
notified Fukushima prefecture that we will make announcement to the media and do
Vent at 9:05 AM.
? Activities after “At 9:04 AM on March 12, shift operators departed to the field
site to do Vent”
【 Open PCV vent valve (MO valve) 】
・ At 9:04，in order to open PCV vent valve, two shift
operators went to the field site. They were equipped with
fire fighting garment, self-contained breathing
apparatus and APD. As the electricity was lost, the field
sites in R/B and T/B were in complete darkness. They
Page 21 Page 21
departed with flashlights. As there was no communication channel with the field
site, we decided to dispatch teams to the field site one by one. After one team
returned to the Main Control Room, the next team departed.
・ The first team departed the Main Control Room to the field site to open the PCV vent
valve (MO valve). At 9:15 AM, opened to 25% per the operation procedure and
returned to the Main Control Room. The exposure
dose was 25mSv.
【 open the S/C vent valve (AO valve) - small 】
・ At 9:24 AM, in order to open the S/C vent valve (AO
valve) -- small, team 2 departed the Main Control
Room to Torus Room. During the way, dose
increased and as there was a risk to exceed the
dose limit, 100mSv, at 9:30 AM, team returned to
the Main Control Room.
・ As the dose was high, we gave up the work by team 3. We reported to the PSER.
【 Considered measures to open S/C vent valve (AO valve ） -large 】
・ As we could not open the S/C vent valve (AO valve) -- small at the field site, the
PSER began considering the location to connect the temporary air compressor (to
11:00 AM). Also, PSER instructed the Main Control Room to open the S/C vent
valve (AO valve) -- small by remote operation hoping for the residual air pressure in
the I&C compressed air line.
【 remote opening of the vent valve (AO valve) -- small (hoping for the residual air
pressure in the I&C compressed air line) ， reading at monitoring posts (“MP”)
became higher 】
・ At 10:17 AM，did the first remote opening, uncertain whether the valve opened.
・ At 10:23 AM，did the second remote opening, uncertain whether the valve opened.
・ At 10:24 AM，did the third remote opening, uncertain whether the valve opened.
・ At 10:40 AM, as we confirmed that the dose at the main gate and MP became higher,
PSER determined that it was highly likely that radioactive substances were released
by Vent. At 11:15 AM, as the dose became lower, PSER suspected that the Vent
was insufficient.
【 Opening the S/C vent valve (AO valve ） -large 】
・ The restoration team of PSER looked for the temporary compressor, received info
that the there was one at the subcontractor's office and decided to go and search at
there. In order to connect the temporary compressor, we needed the adaptor. By
using the piping and instrumentation diagrams, we decided the place to connect. At
Page 22 Page 22
the field site, we took photos of that place and returned to PSER.
・ At 12:30 PM, we looked for the adaptor. We found the temporary compressor at our
subcontractor's office and transferred that by a crane truck. As the dose was high,
we located the compressor at the outside of large equipments carry-in opening. At
2:00 PM, we started the temporary compressor.
・ At 2:30 PM, we confirmed that D/W pressure went down and determined this
as “release of radioactive substances” by Vent.
D/W pressure 0.75MPa→0.58MPa(2:50 PM)
Page 23 Page 23
Time line sequence of major events following earthquake to May 15
th th
(Tue) for Unit 2 at Fukushima Daiichi Nuclear Power Station
This report is based on various information as well as testimonies received from
relevant people up to this point in time. Further announcements may be released upon
the discovery of new information identified during the investigation.
Friday March 11, 2011
2:46 pm Touhoku-Pacific earthquake occurred. The 3rd emergency attitude was
automatically issued.
2:47 pm Automatic Reactor scram , Stopped automatically Main Turbine, Started
Emergency generator automatically.
2:50 pm Manually started up Reactor Core Isolation Cooling System (hereinafter
RCIC).
2:51 pm Shut down RCIC (High Reactor water level).
3:01 pm Confirmed uncritical on Reactor.
3:02 pm Manually started RCIC.
3:06 pm Set up an Emergency Center at headquarter.(To figure out the situation by
damage caused by earthquake, recovering from blackout etc)
3:27 pm 1
st st
wave of Tsunami arrived.
3:28 pm RCIC shut down (High Reactor water level).
3:35 pm 2
nd nd
wave of Tsunami arrived.
3:39 pm Manually started up RCIC.
3:41 pm Lost all AC power sources.
3:42 pm Judged that specific issue (lost all AC power sources) based on the
article 10, clause 1 of Act on Special Measures Concerning Nuclear
Emergency Preparedness occurred and reported to authority etc.
3:42 pm The 1
st st
emergency attitude was issued. Set headquarter for Emergency
Headquarters (Combined headquarter with headquarters for major disaster
countermeasures).
4:36 pm Judged that the specific issue (Enable to inject water by Emergency
Core Cooling System) based on the article 15, clause 1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness
occurred because of enable to confirm Reactor water level and
situation of injecting water. Reported it to authority etc. at 4:45 pm.
4:36 pm 2
nd nd
emergency attitude was issued.
Page 24 Page 24
5:12 pm General Manager of Power station directed to start consideration of
measure to injecting water to Reactor using the Fire Protection System
which is installed as a measure for accident management and fire
fighter.
8:49 pm Temporary lighting was turned on in the main control room.
8:50 pm Government of Fukushima prefecture ordered to evacuate for the residents
within 2km radius from Fukushima Daiichi Nuclear Power Station.
9:02 pm Reported the risk that the water level may reach to Top of Active fuel
(hereinafter TAF) because of uncertain Reactor water level and enable
to check the condition of injecting water by RCIC to the Reactor.
9:13 pm Estimated the TAF reaching time at 9:40 pm, report it to authority.
9:23 pm Prime minister ordered to evacuate for the residents in 3km radius from
Fukushima Daiichi Nuclear Power Station, and to shelter indoors for the
residents in 3km to 10 km radius.
10:00 pm As Reactor water level was turned out to be at TAF+3400mm,
estimated to take more time to reach TAF and reported authority at
22:10 and 22:20.
Saturday, March 12, 2011
12:30 am Confirmed evacuating measure of residents by national government has
been completed (Confirmed the evacuation inside 3km radius in Futaba
town and Okuma town has been completed, reconfirmed at 1:45)
Approx. Approx.
1:30 am Proposed and obtained agreement to implement vent at Unit1 and Unit2 to
prime minister, minister of economy, trade and industry and Nuclear and
Industrial Safety Agency.
2:55 am Confirmed RCIC is under operation.
3:06 am Press conference about vent implementation was held.
3:33 am Reported the result of evaluation exposure dose in the case of vent was
implemented to authorities.
4:55 am Confirmed the radiation dose in the power station raised (0.069μSv /h
(4:00) => 0.59μSv /h(4:23) around main gate) and reported it to authority.
5:44 am Prime minister ordered to the residents in 10km radius from Fukushima
Daiichi Nuclear Power Station to evacuate.
6:50 am The order to implement vent based on the law by minister of economy, trade
and industry (manually vent).
Page 25 Page 25
7:11 am Prime minister arrived at Fukushima Daiichi Nuclear Power Station.
8:04 am Prime minister departed from Fukushima Daiichi Nuclear Power Station.
4:27 pm Measuring the dose exceeding 500μSv /h by monitoring post (1,015μSv /h),
judged as specific event based on article 15,clause 1 of Act on Special
Measures Concerning Nuclear Emergency Preparedness occurred
(Radiation dose raised abnormally at boundary of the site) and reported it to
the authority.
5:30 pm General Manager of the power station ordered to prepare the operation
of vent.
6:25 pm Prime minister ordered the residents in 20km radius from Fukushima Daiichi
Nuclear Power Station to evacuate.
Sunday, March 13, 2011/06/21
8:10 am Primary Containment Vessel (hereinafter PCV) Vent valve “OPEN”.
8:56 am As radioactive dose exceeding 500μSv /h(882μSv /h) was measured by
monitoring post, it was judged to specific issue based on Article15,
clause1 of Act on Special Measures Concerning Nuclear Emergency
Preparedness occurred, and reported to the authorities.
10:15 am General Manager of Power Station ordered to start Vent operation .
11:00 am Vent line composition was completed except for rupture disc.
11:00 am Prime minister ordered sheltering indoors to the residents in the area of
over 20km to 30km radius from Fukushima Daiichi Nuclear Power Station.
11:20 am Announcement of implementation of the Vent.
12:05 pm General Manager of Power Station ordered to prepare to use sea
water.
2:15 pm As radioactive dose exceeding 500μSv /h(905μSv /h) was measured by
monitoring post, it was judged to specific issue (radioactive dose at
boundary abnormally raise) based on Article15, clause1 of Act on Special
Measures Concerning Nuclear Emergency Preparedness occurred, and
reported to the authorities at 2:23.
3:18 pm Reported evaluation result of dose exposure in case of implementation of
Vent to authorities.
Monday, March 14, 2011
2:20 am As radioactive dose exceeding 500μSv /h(751μSv /h) was measured
around main gate, it was judged to specific issue(radioactive dose at
Page 26 Page 26
boundary abnormally raised) based on Article15, clause1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness
occurred, and reported to the authorities at 4:24.
2:40 am As radioactive dose exceeding 500μSv /h(650μSv /h) was measured by
monitoring post, it was judged to specific issue(radioactive dose at
boundary abnormally raised) based on Article15, clause1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness
occurred, and reported to the authorities at 5:37.
4:00 am As radioactive dose exceeding 500μSv /h(820μSv /h) was measured by
monitoring post, it was judged to specific issue (radioactive dose at
boundary abnormally raised) based on Article15, clause1 of Act on Special
Measures Concerning Nuclear Emergency Preparedness occurred, and
reported to the authorities at 8:00.
9:12 am As radioactive dose exceeding 500μSv /h(518.7μSv /h) was measured by
monitoring post, it was judged to specific issue (radioactive dose at
boundary abnormally raised) based on Article15, clause1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness
occurred, and reported to the authorities at 9:34.
11:01 am The large valve of suppression chamber became (hereinafter “S/C”)
“Close” because of the explosion of building of Unit 3. Incapable of
“Open” was confirmed. Prepared water injection line was not
available because of breakage of the fire engine and the hose.
1:05 pm Recommencement of composing line of injecting seawater including fire
engine.
1:18 pm As Reactor water level was downward trend , reported to start preparation
work such as injecting seawater to the Reactor immediately to the
authorities.
1:25 pm As Reactor water level is decreasing, the RCIC function seems to be lost,
judged Article15, clause1 of Act on Special Measures Concerning Nuclear
Emergency Preparedness occurred (Lost Reactor Cooling Function) , and
reported to the authorities at 1:38 pm.
3:26 pm Evaluated TAF reaching time is 4:30 pm, reported it to the authorities.
4:30 pm Activated fire engine for injecting seawater to the Reactor.
4:34 pm Started operation for reducing Reactor pressure, and reported to start
injecting seawater using fire protection system to authorities.
5:17 pm Reactor water level reached TAF. Reported it to the authorities at 5:25 pm.
Page 27 Page 27
Approx. Approx.
6:00 pm Started Reactor depressurization (Reactor pressure 5.4MPa=>7:03 pm
0.63 MPa ).
6:22 pm Reactor water level reached TAF-3,700mm. Judge the fuel was exposed to
air. Reported to the authorities at 7:32pm.
7:20 pm Confirmed the fire engine for injecting seawater to the Reactor stopped due
to out of fuel.
7:54 pm
Started injecting seawater to the Reactor from Fire Protection
System by fire engine (started up at 7:54 pm and 7:57)
Approx. Approx.
9:00 pm Operated to open the small valve of S/C vent valve(AO valve). The
vent line composition was completed except for rupture disc.
9:20 pm Opened 2 Safety Release Valves (hereinafter SRV) and confirmed
recovering of water level. Reported it to the authorities at 9:34 pm (as of
9:30 pm Reactor water level=TAF-3,000mm).
9:35 pm As radioactive dose exceeding 500 μSv/h was measured by monitoring
car(760μSv/h), it was judged to specific issue (radioactive dose at
boundary abnormally raised) based on Article15, clause1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness occurred,
and reported to the authorities at 10:35 pm.
10:50 pm As Dry Well (hereinafter D/W) pressure exceeded maximum usage
pressure 427kPa gage, it was judged to specific issue (RPV pressure
abnormally raised) based on Article15, clause1 of Act on Special
Measures Concerning Nuclear Emergency Preparedness occurred, and
reported to the authorities at 11:39 pm.
Approx. Approx.
11:35 pm As the pressure at S/C side was lower than working pressure of the
rupture disk and the pressure at D/W side was raising, decided measure
of vent operation with opening small valve of D/W vent.
Tuesday, March 15, 2011
12:02 am Operated to open the small valve of D/W vent valve (AO valve). Vent
line composition except for rupture disc was completed (confirmed
the valve was closed few minutes later).
3:00 am As D/W pressure exceeded designed maximum usage pressure, tried to
operate to reduce pressure and injecting water to the Reactor. But the
Page 28 Page 28
situation was not depressurized sufficiently. Reported it to the authorities
at 4:17 am.
Approx. Approx.
6:00-6:10 am A large impulsive sound occurred around suppression chamber.
6:50 am As radioactive dose exceeding 500μSv/h(518.7μSv /h) was measured at
around main gate, it was judged to specific issue (radioactive dose at
boundary abnormally raised) based on Article15, clause1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness
occurred, and reported to the authorities at 7:00 am.
7:00 am Report to authorities on evacuation to Fukushima Daini except for the
needed personnel such as monitoring and work.
8:11 am As radioactive dose exceeding 500μSv/h(807μSv /h) was measured by
monitoring post, it was judged to specific issue (radioactive materials
abnormally released due to fire disaster and explosion)
based on
Article15, clause1 of Act on Special Measures Concerning Nuclear
Emergency Preparedness occurred, and reported to the authorities at
8:36am. At 8:25 am, confirmed white smoke (seems steam) rising out
from the wall around 5
th th
floor of Reactor Building, reported to the
authorities at 9:18pm.
4:00 pm As radioactive dose exceeding 500μSv/h(531.6μSv /h) was measured at
main gate, it was judged to specific issue (radioactive dose at boundary
abnormally raised) based on Article15, clause1 of Act on Special
Measures Concerning Nuclear Emergency Preparedness occurred, and
reported to the authorities at 4:22 pm.
11:05 pm As radioactive dose exceeding 500μSv/h(4548μSv /h) was measured at
around main gate, it was judged to specific issue (radioactive dose at
boundary abnormally raised) based on Article15, clause1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness
occurred, and reported to the authorities at 11:20 pm.
END
Page 29 Page 29
Fukushima Daiichi Nuclear Power Station Unit 2
Alternative Water Injection
This report is summary of the fact information and verbal evidence currently we have.
When we found new facts through the continuous investigation, we will update fact in this
report.
○Activities after Determination and Reporting of Loss of ECCS at 16:36 on
March11.
【 Planning for Alternative Injection 】
・ At 17:12, start examination of using alternative method of water injection
(Fire Protection System(“FP”), Feed Water Make-up System and
Containment Vessel Cooling System), which are installed under
Accident Management Plan(“AP) and using fire engine with water from
fire protection pool which was installed as a lesson of Chuetu-Oki
Earthquake.
・ In the Main Control Room, to secure alternative method of water injection,
prepare AM manual on the Chief Unit Operator's desk and conduct
confirmation of water injection line into the reactor .
・ Taking the radiation level of Unit 1 into consideration, before the radiation
getting higher, in order to establish water injection line for alternative
method by way of Residual Heat Reduction System, open the valves of
Residual Heat Removal System manually in the turbine and reactor
building, in the darkness, and secure the situation where water injection is
possible after decompression of reactor (below 0.69MPa).
・ Restoration Team of Power Station Emergency Response Team has
confirmed status of submergence and damage of Power Panel (High
Voltage Clad Switch Gear, Power Center) and as a result of insulation
resistance test, confirmed one of the power center was alive and start
examination of water injection by using Control Rod Drive System(“CRD”)
and Standby Liquid Control System(“SLC”), where high pressure water
injection is possible, after power restoration to power center by power
supply vehicle.
・ At 22:00，water level gauge of the reactor has turned out and as its reading
was Top of Active Fuel(“TAF”) +3400mm, confirmed not reaching TAF.
Page 30 Page 30
【 Restoration of power for alternative water injection 】
As power panel and pumps of CRD and SLC was not damaged by sea water,
and high pressure water injection was possible, restoration of power by power
supply vehicle to the power center was carried out.
・ At around 15:30, though cable was connected to the primary side of the P/C
of Unit 2 and, in parallel, connection was made between high voltage power
supple vehicle, at 15:36 explosion occurred at Unit 1. Installed cables were
damaged by explosion litter and high voltage poser supply vehicle was
tripped. All the workers stopped their work and evacuated to the Main
Anti-Earthquake Building.
・ On the next day, tried restart of power supply vehicle, which was connected to
power center of unit 2, however, current surge relay was operated and failed
to supply power.
○Activities after 「 3/13 12:05 Direction by Station Manager to prepare to use sea
water 」
【 Start preparation of sea water injection 】
・ In preparation of RCIC out of service, in order to secure switching of sea
water injection, proceed establishment of water line of back wash valve pit
of Unit 3 as water source, and installed hose pipe of fore engines.
【 Reestablishment of sea water injection pipe line after explosion of Unit 3 】
・ At 3/14 11:01 ， due to the explosion of reactor building of Unit 3, to
secure safety all the workers evacuated from site. Hose piping was
ready to use but were unavailable to use due to the damage of fire
engines and hose pipe.
・ In the afternoon, immediately dashed off to the site and confirmed
status of the site and, according to the scattered situation of rubble,
decided to precede injecting water sourcing not from the back wash
valve pit of Unit 3 but directly from the shallow draft quay. In the high
radiation environment surrounded by scattered rubble, proceed
preparing new water injection line by using useable fire engines and
hose pipe.
・ At 13:18，water level of reactor was in the down trend, at 13:25，determined
lose of RCIC function. Estimated from the current situation, reaching TAF
will be at around 16:30. Continuously prepare for sea water injection and at
Page 31 Page 31
14:43connected to FP by fire engine.
・ From after 15PM to after 16PM， due to the aftershocks centered in
offshore of Fukushima Prefecture, work was conducted with
difficulties of suspension of work and evacuation.
・ At around 16:30started fire engine and prepared for the readiness to
start water injection when decompression of reactor.
【 Decompression of Reactor 】
・ In order to inject water from fire engine, decompression of reactor by
opening Safety and Relief Valve (“SR”) was necessary , however, as
temperature and pressure of Suppression Chamber (“S/C”) was so
high (3/14 12:30 S/C Temperature was 149.3℃ and S/C pressure was
486Pa) that, even if the SR valve was opened, there was a possibility
of pressure reduction difficulty as the steam will not be condensed,
decided after conducting Containment Vessel Vent (“Vent”), then open
the SR valve and water injection will be started.
・ At around 16:00 頃，as it was foreseeable taking time until opening vent
valve, changed priority on decompression of reactor by opening SR valve.
Station manger also directed to conduct opening vent valve in parallel.
・ Under the lack of power, battery was necessary to open the SR valve.
Gathered batteries out from the cars and carried to main control room
and connected to the electricity cable, however, as the power voltage
was lacking, add batteries, try operating several SR valves, continue
efforts to decompressing reactor and at around 18:00 start decompression
of the reactor.
・ Time was consumed as the temperature and pressure of S/C was high and
difficult condition for condensation.
Reactor pressure 6.998MPa(16:34)→6.075MPa(18:03)→0.63MPa(19:03)
［ Restart of Fire Engines ］
・ Radiation at site was high and confirmation of operating status of fire
engines was forced in rotation, at 19:20, confirmed fire engine which was
used for water injection was stopped due to the shortage of fuel. After
fueling, started water injection into the reactor by using FP line by fire
engine(at 19:54, 19:57 started respectively).
End End
Page 32 Page 32
Unit 2, Fukushima Daiichi Nuclear Power Station
The operation of the vent valve at the PCV
This summarizes the facts based on info and testimony available to date. We will
continue the investigation. If new facts are confirmed at a later date, we will announce
again.
?
Activities after report “At 4:36 PM on March 11, Determination and Report of
ECCS's inability to inject water”
・ As a result of restoration work of instruments, at 9:50 PM, we could confirm the
Reactor water level (Top of Active Fuel +3400mm). At 11:25 PM, we could confirm
the D/W pressure (0.141MPa abs). At 2:55 AM, on March 12, we could confirm
operation of RCIC. We decided to prioritize opening the vent valve (“Vent”) for
Unit 1 . We proceeded with Vent of Unit 1. At the same time, we continued
monitoring parameters of Unit 2.
?
Activities after “At 5:30 PM on March 12, Instruction from the Station Manager to
proceed with the preparation of Vent”
【 Preparation work for Vent 】
・ Water injection to the Reactor by RCIC continued. D/W pressure was stable at
200～300kPaabs. As we expected that sooner or later we have to do Vent, we
began preparation for the venting line-up together with Unit 3. As the dose at the
field site was low, we decided to open valves for Vent, other than the rupture disk.
・ At 12:06 AM on March 12, we confirmed that D/W pressure for Unit 1 may have
exceeded 600kPa abs. We started the actual work for Vent. At that time, as for Unit
2, we checked from the drawings of valves whether we could manually open
valves required for Vent and whether we could attach the jig and force the
valve open. Based on the result, the piping and instrumentation diagram, AM
operation procedure and the Vent procedure for Unit 1, we confirmed the operation
procedure of valves for Vent (PCV vent valve (MO valve) can be opened manually
S/C vent valve (AO valve) cannot be opened manually) and prepared the Vent
procedure. We also checked the places of valves for Vent using the valve check
sheet.
（From here, March 13）
【 Open PCV vent valve (MO valve) and S/C vent valve (AO valve)-large 】
・ In order to manually open PCV vent valve (MO valve), shift operators wore
Page 33 Page 33
necessary equipments such as the self-contained breathing apparatus,
brought the flashlight and departed for R/B.
・ At 8:10 AM, opened PCV vent valve (MO valve) by 25% per the operation
procedure.
・ At 11:00 AM, we excited the solenoid for S/C vent valve (AO valve)-large by a small
generator for the temporary lighting at the Main Control Room and opened S/C vent
valve (AO valve)-large. We made up the vent line other than the rupture disk.
（D/W pressure was lower than the working pressure of the rupture disk (427kPa
gauge), so Vent hadn't yet occurred. We kept the vent valves open and continued
monitoring D/W pressure.）
?
Activities after “At 11:01 AM on March 14, R/B of Unit 3 exploded. The water
injection line prepared was out of order because of damage to the fire engine and
hose.”
【 Impact of the explosion 】
・ Because of the explosion, the excitation of the solenoid for S/C vent valve (AO
valve)-large turned off and the S/C vent valve closed. We had to do the venting
line-up again.
・ After the explosion, workers other than shift operators at the Main Control
Room suspended all works and evacuated to the main anti-earthquake
building. As we had to confirm the workers ' safety and the status of the field
site, we couldn ' t resume work for a while.
・ D/W pressure was around 450kPa abs, stable below the Vent pressure.
【 Open S/C vent valve (AO valve)-small 】
・ After the instruction for evacuation was lifted, at 4:00 PM, we tried to open S/C vent
valve (AO valve)-large. At 4:20 PM, as the air pressure from the compressor was
insufficient, we couldn't open.
・ As there was no change on D/W pressure, at 6:35 PM, we tried to open not only S/C
vent valve (AO valve)-large but also S/C vent valve (AO valve)-small to restore the
vent line. We presumed that we couldn't open S/C vent valve (AO valve)-large
because of malfunction of solenoid.
・ At 9:00 PM, we could slightly open S/C vent valve (AO valve)-small. We established
the venting line-up other than the rupture disk.
（D/W pressure was lower than the working pressure of the rupture disk (427kPa
gauge), so Vent hadn't yet occurred. We kept the vent valves open and continued
monitoring D/W pressure.）
Page 34 Page 34
【 open D/W vent valve -small 】
・ At 10:50 PM，D/W pressure increased. As the pressure exceeded the maximum
operating pressure (427kPa gauge), we determined that specific incident stipulated
in article 15 of Act on Special Measures Concerning Nuclear Emergency
Preparedness”D/W pressure excessively high” occurred.
・ D/W pressure was in upward trend whereas S/C pressure was stable around 300
～400kPa abs. The pressure was not unified. As S/C pressure was lower than the
working pressure of the rupture disk and D/W pressure increased, we decided to
open D/W vent valve (AO valve)-small to do Vent.
・ At 12:02 AM on March 15, we finished preparation of the venting line-up other than
the rupture disk. A few minutes later, we confirmed that the rupture disk was closed.
（D/W pressure did not go down from 750kPa abs. After that, D/W pressure was
stable but high.）
?
Activities after “ At 6:00～6:10 AM on March 15, a big boom occurred around the
suppression chamber ”
・ At 6:00～6:10, a big boom occurred around the S/C. The measured S/C pressure
went down to 0MPaabs.
・ Other than TEPCO employees and workers required for plant supervision and
temporary restoration work, we temporarily evacuated to Fukushima Daini.
? 650 persons moved to Fukushima Daini. 70 persons stayed at the power
station headquarters.
・ Shift operators periodically went to the Main Control Room to log D/W pressure etc.
? At 11:25 AM, we confirmed decrease in D/W pressure (730kPa
abs(7:20)→155kPa abs(11:25))
End End
Page 35 Page 35
Time line sequence of major events following earthquake to May 15
th th
(Tue) for Unit 3 at Fukushima Daiichi Nuclear Power Station
This report is based on various information as well as testimonies received from
relevant people up to this point in time. Further announcements may be released upon
the discovery of new information identified during the investigation.
Friday, March 11, 2011
2:46 pm Great East Japan Earthquake occurred. 3rd emergency attitude was
automatically announced.
2:47 pm Reactor scram occurred automatically , main turbine tripped manually.
Around 2:48 pm Emergency diesel generators activated automatically
2:54 pm It was confirmed that the reactor was subcritical
3:05 pm Reactor Core Isolation Cooling System (hereinafter called “RCIC”) activated
manually
3:06 pm Emergency Center was established at the main office (in order to figure out the
damage situation caused by the earthquake and to restore the blackouts)
3:25 pm RCIC tripped (as the reactor water level was high)
3:27 pm 1st wave of the seismic sea wave arrived
3:35 pm 2nd wave of the seismic sea wave arrived
3:38 pm All AC electric power supply was lost
3:42 pm It was determined that a specific incident stipulated in article 10, clause 1 of
Act on Special Measures Concerning Nuclear Emergency Preparedness (loss
of all AC electric supply) occurred and it was informed to the government
offices etc.
3:42 pm 1st emergency attitude was announced. Contingency Planning Center was
established (and combined with Emergency Center)
4:03 pm RCIC activated manually
4:36 pm 2nd emergency attitude was announced
8:50 pm Fukushima prefecture ordered the residents within 2km radius of the periphery of
Fukushima Daiichi Nuclear Power Station to evacuate
9:23 pm Prime Minister ordered the residents within 3km radius of the periphery of
Fukushima Daiichi Nuclear Power Station to evacuate, and the residents within 3km
to 10km radius of the periphery to evacuate indoors
9:58 pm Temporary lights in the main control room were turned on.
Page 36 Page 36
Saturday, March 12, 2011
0:30 am Government confirmed the completion of evacuation of the residents (3km radius of
the periphery of Fukushima Daiichi Nuclear Power Station in Futaba Town and
Okuma Town, reconfirmed at 1:45 am)
4:55 am Increase of the radiation dose was confirmed (Near the main gate, 0.069μSv/h,
4:00 am to → 0.59μSv/h, 4:23 am), and it was informed to the government offices
etc. etc.
5:44 am Prime Minister ordered the residents 10km radius of the periphery of Fukushima
Daiichi Nuclear Power Station to evacuate.
7:11 am Prime Minister arrived at Fukushima Daiichi Nuclear Power Station
8:04 am Prime Minister departed from Fukushima Daiichi Nuclear Power Station
11:36 am RCIC tripped
0:35 pm High Pressure Core Injection System (hereinafter called “HPCI”) activated
automatically (as the reactor water level was low)
5:30 pm Plant manager ordered to prepare for the vent of primary containment vessel
(hereinafter called “vent”)
6:25 pm Prime Minister ordered the residents 20km radius of the periphery of Fukushima
Daiichi Nuclear Power Station to evacuate
Sunday, March 13, 2011
2:42 am HPCI stopped
5:10 am It was determined that a specific incident stipulated in article 15, clause 1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness (loss of reactor
cooling function) occurred as the injection of water by RCIC was impossible, and it
was informed to the government offices etc. at 5:58 am
5:15 am Plant manager ordered to complete the lineup of the vent except for the
rupture disk
5:50 am Press release of implementation of the vent
6:19 am As it was determined that the water level reached to the top of active fuel
(hereinafter called “TAF”) at 4:15 am, it was informed to the government offices etc.
7:35 am The result of the evaluation exposure dose by vent was informed to the government
offices etc.
7:39 am Spray inside the primary containment vessel started, and it was informed to the
government offices etc. at 7:56 am
8:35 am Primary containment vessel (hereinafter called “PCV”) vent valve (MO valve) was
Page 37 Page 37
opened
8:41 am By opening the large valve of the vent valve (AO valve) of the suppression
chamber (hereinafter called “S/C”), the configuration of the vent line was
completed except for the rupture disk. It was informed to the government
offices etc. at 8:46 am
8:56 am As the radiation dose over 500μSv/h was measured at the monitoring post, it was
determined that a specific incident stipulated in article 15, clause 1 of Act on Special
Measures Concerning Nuclear Emergency Preparedness (radiation dose at the
border of the site increased extraordinary) occurred and it was reported to the
government offices etc. at 9:01 am
Around 9:08 am A rapid depressurization of the reactor pressure by safety relief valve was
implemented. It was informed to the government offices at 9:20 am that injection of
water to the reactor through fire extinction system will be implemented hereafter
9:25 am Injection of fresh water (with boric acid) into the reactor by fire truck through fire
extinction system was started
9:36 am Drop of drywell (hereinafter called “D/W”) pressure caused by vent operation
was confirmed. It was informed to the government offices that injection of
water to the reactor through fire extinction system started
10:30 am Plant Manager ordered to intend an injection of sea water
11:00 am Prime minister ordered the residents 20km to 30km radius of the periphery of
Fukushima Daiichi Nuclear Power Station to evacuate indoors
11:17 am The close of large valve of S/C vent valve (AO valve) was confirmed (as the
pressure of the air tank for the actuation dropped)
12:20 am Injection of fresh water terminated
12:30 am The large valve of S/C vent valve (AO valve) was opened (as the air tank for the
actuation was exchanged)
1:12 pm Injection of sea water into the reactor through the fire extinction system
started
2:15 pm As the radiation dose over 500μSv/h was measured at the monitoring post
(905μSv/h), it was determined that a specific incident stipulated in article 15, clause
1 of Act on Special Measures Concerning Nuclear Emergency Preparedness
(radiation dose at the border of the site increased extraordinary) occurred and it was
reported to the government offices etc. at 2:23 pm
Monday, March 14, 2011
1:10 am As there were little sea water left to inject into the reactor, a fire truck was arranged
Page 38 Page 38
to supply sea water into the reversing valve pit
2:20 am As the radiation dose over 500μSv/h was measured near the main gate (751μSv/h),
it was determined that a specific incident stipulated in article 15, clause 1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness (radiation dose at
the border of the site increased extraordinary) occurred and it was reported to the
government offices etc. at 4:24 am
2:40 am As the radiation dose over 500μSv/h was measured at the monitoring post
(650μSv/h), it was determined that a specific incident stipulated in article 15, clause
1 of Act on Special Measures Concerning Nuclear Emergency Preparedness
(radiation dose at the border of the site increased extraordinary) occurred and it was
reported to the government offices etc. at 5:37 am
3:20 am Injection of sea water by fire truck restarted
4:00 am As the radiation dose over 500μSv/h was measured at the monitoring post
(820μSv/h), it was determined that a specific incident stipulated in article 15, clause
1 of Act on Special Measures Concerning Nuclear Emergency Preparedness
(radiation dose at the border of the site increased extraordinary) occurred and it was
reported to the government offices etc. at 8:00 am
5:20 am The operation of the small valve of the S/C vent valve (AO valve) started
6:10 am It was confirmed that the small valve of the S/C valve (AO valve) was opened
9:12 am As the radiation dose over 500μSv/h was measured at the monitoring post
(518.7Sv/h), it was determined that a specific incident stipulated in article 15, clause
1 of Act on Special Measures Concerning Nuclear Emergency Preparedness
(radiation dose at the border of the site increased extraordinary) occurred and it was
reported to the government offices etc. at 9:34 am
9:20 am The injection of sea water from the shallow draft quay into the reversing valve pit
was started
11:01 am An explosion occurred in the reactor building. Injection of sea water
stooped as the fire truck and hose were damaged
Around 4:30 pm New injection line into the reactor was constructed by exchanging
the fire truck and horse, and the injection of sea water restarted
9:35 pm As the radiation dose over 500μSv/h was measured by the monitoring car
(760Sv/h), it was determined that a specific incident stipulated in article 15, clause 1
of Act on Special Measures Concerning Nuclear Emergency Preparedness
(radiation dose at the border of the site increased extraordinary) occurred and it was
reported to the government offices etc. at 10:35 pm
Page 39 Page 39
Tuesday, March 15, 2011
6:50 am As the radiation dose over 500μSv/h was measured near the main gate (583.7Sv/h),
it was determined that a specific incident stipulated in article 15, clause 1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness (radiation dose at
the border of the site increased extraordinary) occurred and it was reported to the
government offices etc. at 7:00 am
7:00 am It was informed to the government offices etc. that the employees except for the
needed personnel for the monitoring and the operation would evacuate temporally to
the Fukushima Daini Nuclear Power Station
7:55 am Steam floating at the upper side of the reactor building was confirmed, and it was
informed to the government offices etc.
8:11 am As the radiation dose over 500μSv/h was measured near the main gate (807Sv/h),
it was determined that a specific incident stipulated in article 15, clause 1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness (extraordinary
emission of radioactive material result from fire and explosion etc.) occurred and it
was reported to the government offices etc. at 8:36 am
4:00 pm As the radiation dose over 500μSv/h was measured at the main gate (531.6Sv/h), it
was determined that a specific incident stipulated in article 15, clause 1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness (radiation dose at
the border of the site increased extraordinary) occurred and it was reported to the
government offices etc. at 4:22 pm
11:05 pm As the radiation dose over 500μSv/h was measured near the main gate
(4,548Sv/h), it was determined that a specific incident stipulated in article 15, clause
1 of Act on Special Measures Concerning Nuclear Emergency Preparedness
(radiation dose at the border of the site increased extraordinary) occurred and it was
reported to the government offices etc. at 11:20 pm
Page 40 Page 40
Fukushima Daiichi Nuclear Power Station Unit 3
Alternative Water Injection
This document is a summary of the latest information obtained through information and
interviews with personnel concerned. We will continue investigation and announce when
new facts and findings are obtained.
Activities after “the stoppage of RCIC at 11:36 am on March 12”
【 Water Injection by Fire Engines 】
・ Fire engines in the site were called but could not arrive, because they were
all being used for water injection to Unit 1.
・ Since tsunami occurred, the traffic between Unit 3 and Unit 5/6 had been
disrupted due to the damage of the road and rubbles caused by tsunami.
However, as restoration work such as road leveling with sandbags and
removal of rubbles progressed, the restored traffic between Unit 3 and Unit
5/6 allowed us to bring the fire engines from Unit 5/6. Also, a fire engine
prepared as a backup facility for the emergency of Fukushima Daini moved to
Fukushima Daiichi. Fire engines for water injection were lined up, sourcing
freshwater from fire cistern.
・ In order to inject water by fire engines, it was necessary to decrease the
reactor pressure by operating Safety Relief Valve (S/R Valve), but S/R Valve
was not able to be operated because batteries had run out. Since batteries in
the site were already collected for the restoration of indicators, Unit 1 and 2,
there were no extra batteries in the site. Therefore, we removed and
gathered batteries from employees' car and connected them to indicators of
Main Control Room. At approximately 9:08 am we opened S/R Valve and
conducted rapid decrease of the reactor pressure.
・ Through that operation the reactor pressure went below the fire engines' jet
force, which allowed us to start alternative water injection by fire engines at
9:25 am.
【 Restoration of existing cooling facilities 】
・ We tried to restart water injection by existing cooling facilities, but could not.
・ We tried water injection by diesel powered fire-extinguishing pumps, but
could not because the reactor pressure was as high as approximately
4MPa.
・ We tried to reboot HPCI, but could not due to the lack of batteries.
Page 41 Page 41
・ We tried water injection through RCIC by confirming the situation in
RCIC operation room, but could not reboot it.
【 Restoration of High Pressure Core Injection System 】
・ Since the previous day we continued power restoration work via Power
Center in order to restore Boric Acid Injection System that was capable of
high pressure water injection, but the work was not successfully progressed
due to the interruption of the work and evacuation caused by earthquakes
from time to time and bad work environment (dark place, obstacles scattered
and manhole covers lost). As a result, the restoration was not completed.
Activities after Plant Manager's order “we will move by taking into account
seawater injection,” at 10:30 am on March 13.
【 Switching to seawater 】
・ Since freshwater of near fire cisterns ran out at 12:20 pm, we started to
change the water supply line in order to use seawater in the vertical shaft of
reversing valve. We had been well prepared for quick switching, but we were
forced to suspend the work by the evacuation order caused by aftershocks.
The work was completed as soon as it was resumed, and seawater injection
started at 1:12 pm.
・ Concurrently, we prepared additional freshwater.
【 Supply of seawater to the vertical shaft of reversing valve 】
・ We had been requesting several offices for the support of fire engines, but it
was not impossible for such fire engines to directly approach the power
station due to radioactivity and contamination in the site and bad condition of
the road to the station. It took longer time for fire engines to arrive at the
station because the drivers needed to be changed to the plant operators at
Off-site Center or J-Village.
・ We tried to take seawater accumulated at the basement of the turbine, Unit 4
by breaking the entrance shutters of truck bay doors of the turbine building
and moving fire engines to the place, but could not. Additionally, we
examined the possibility of taking water from the discharge channel of Unit 4
or the skill training center's pool, but that was not implemented.
・ Since the remaining amount of seawater in the vertical shaft of revering valve
became little at 1:10 am on March 14, we stopped the operation of fire
engines in order to supply seawater to the vertical shaft. With regard to
seawater injection to Unit 3, we were able to resume injection at 3:20 am
Page 42 Page 42
since we could take seawater by putting fire engines close to the vertical
shaft of reversing valve and placing the nozzle of the hose at deeper spot.
・ Additional fire engines arrived at the station early in the morning. In order to
directly take seawater and supply it to the vertical shaft of reversing valve, we
placed 2 fire engines at around Shallow Draft Quay and arranged the line for
water supply. We started supplying seawater from Shallow Draft Quay to the
vertical shaft of reversing valve at 9:20 am.
・ 7 Water Supply Vehicles (each 5 tons) of Self Defense Force that were
requested as the source of freshwater arrived at the station. We decided to
use them to supply water to the vertical shaft of reversing valve and placed
them at the shaft at 10:53 am. We started water supply, but stopped due to
the explosion of the reactor building.
Page 43 Page 43
○Activities after
Explosion occurred at the reactor building at 11:01 am on
March 14. Seawater injection was stopped since fire engines and
hoses got damaged.
【Damage】
・ Workers except for operators in
Main Control Room interrupted their
work
and and
evacuated to
Main Main
Anti-Earthquake Building. We could
not resume restoration work for a
while since it took time for us to
confirm workers safety and the
situation of the site. 4 TEPCO
employees, 3 workers of partner companies and 4 persons of Self Defense
Force got injured.
・ Rubbles with high level of radioactivity were scattered around by the
explosion. Seawater injection was stopped since fire engines and hoses
got damaged. Due to the rubbles the vertical shaft of reversing valve
became unusable.
【Restart of water injection to the reactor】
・ Since the vertical shaft of reversing valve was not available, we placed
good fire engines around Shallow Draft Quay and re-arranged hoses in
order to take seawater directly from sea and inject it to the reactor.
By connecting 2 fire engines in series, we formed the water supply line
toward both Unit 2 and 3. At approximately 4:30 pm, we restarted seawater
injection by fire engines.
End End
External View of Unit 3 after explosion
Page 44 Page 44
Unit 3, Fukushima Daiichi Nuclear Power Station
The operation of the vent valve at the PCV
This summarizes the facts based on info and testimony available to date. We will
continue the investigation. If new facts are confirmed at a later date, we will announce
again.
?
Activities after “At 5:30 PM on March 12, Instruction from the Station Manager to
proceed with the preparation of opening the vent valve (“Vent”)”
【 Preparation work for Vent 】
・ At the Main Control Room, at 9:00 PM, we started considering Vent procedures.
We checked the sequence and places of valves and wrote on the whiteboard.
・ The generation team of the power station emergency response headquarters
( PSER ) completed the Vent procedure manual for Unit 1. Based on that Vent
procedure manual for Unit 1 and the accident management procedure manual for
Unit 3, generation team considered the Vent procedure manual for Unit 3 together
with the restoration team. We notified the Vent procedure manual to the Main
Control Room.
（From here, March 13）
・ At 4:50 AM, in order to open S/C vent valve (AO valve)-large, we excited the
solenoid using a small generator for the temporary lighting at the Main Control
Room. The shift operator checked the indicator of the valve at the Torus Room. As
the indicator showed “closed”, we determined that the valve was completely closed.
Inside the Torus Room was very hot because of the Reactor steam flow from the
safety relief valve to S/C (S/C is below the Torus Room). There was no lighting ie
complete darkness. It was a tough working environment.
【 finish the venting line-up 】
・ At 5:15 AM, Station Manager instructed to complete the venting line-up other than
the rupture disk and prepare for the press release.
・ At 5:23 AM，as the solenoid for S/C vent valve (AO valve)-large was excited but
the S/C vent valve was closed, we determined that we had to change the air tank.
After that, we changed the air tank and opened the S/C vent valve.
・ At 5:50 AM，we made the press release regarding Vent.
・ At 8:35 AM, we manually opened the vent valve (MO valve) to 15% per the
procedure.
Page 45 Page 45
?
Activities after “At 8:41 AM on March 13, with the opening of S/C vent valve (AO
valve)-large, we finished the venting line-up other than the rupture disk”
【 maintained the venting line-up 】
・ At 8:41AM, we finished the venting line-up. The pending was rupture of the rupture
disk.
・ At 9:24 AM, as D/W pressure went down 0.637 MPa abs (9:10 AM) to 0.540 MPa
abs (9:24 AM), PSER determined that Vent was done around 9:20 AM.
・ At 9:28 AM, as the air tank's pressure at S/C vent valve (AO valve) was in
downward trend, we went to the field site to tighten the connecting parts. We
confirmed air leakage and repaired.
・ At 11:17 AM, we confirmed closing of S/C vent valve (AO valve)-large due to loss of
air pressure. We replaced the air tank and opened. At 12:30 PM, we confirmed that
S/C vent valve (AO valve)-large was open.
・ In order to open and lock S/C vent valve (AO valve)-large S/C at open position, we
went to the Torus Room. As the temperature was high and there was vibration due
to the operation of the safety relief valve, we could not open and lock.
【 dose at the field site increased 】
・ At 2:31 PM, we observed over 300mSv/h at the north side airlock, R/B (there
was white gaseous substance inside) and 100mSv/h at the south side airlock.
At 3:28 PM, the dose at the Main Control Room of Unit 3 side went up to
12mSv/h. Shift operators evacuated to Unit 4 side.
・ At 5:52 PM, we finished charging the temporary compressor. As dose was high, the
restoration team of PSER brought the temporary compressor to the large
equipments carry-in opening by a crane truck and connected to IA line.
・ At 8:10 PM, we determined that S/C vent valve (AO valve)-large opened from the
reduction of D/W pressure.
・ After this, because of loss of air pressure for S/C vent valve (AO valve)-large and
loss of excitation of the solenoid at the air supply line, we couldn't maintain the S/C
vent valve open. Several times we operated the valve to open.
?
3/15 4:00 PM confirmed close ／ 3/15 4:05 PM operated to open
?
3/17 9:00 PM confirmed close ／ 3/17 9:30 PM operated to open
?
3/18 5:30 AM confirmed close ／ 3/18 5:30 AM operated to open
?
3/19 11:30 AM confirmed close ／ 3/20 11:25 AM operated to open
?
4/8 6:30 PM confirmed close
（From here, March 14）
【 add the vent line 】
Page 46 Page 46
・ From 2:00 AM, D/W pressure was in upward trend
※ ※
. We decided to open S/C vent
valve (AO valve)-small. At 3:40 AM, we excited the solenoid.
※0.265MPa abs（2:00 AM）→0.315MPa abs（3:00 AM）
・ At 5:20 AM, we started operation to open S/C vent valve (AO valve)-small. At 6:10
AM, we confirmed that the valve was open.
・ After this, because of loss of air pressure for S/C vent valve (AO valve)-small and
loss of excitation of the solenoid at the air supply line, we couldn't maintain the S/C
vent valve open. Several times we operated the valve to open.
? 3/15 4:00 PM confirmed close／3/16 1:55 AM operated to open
? 4/8 6:30 PM confirmed close
End End
Page 47 Page 47
Time line sequence of major events following earthquake to May 15
th th
(Tue) for Unit 4 to 6 at Fukushima Daiichi Nuclear Power Station
This report is based on various information as well as testimonies received from
relevant people up to this point in time. Further announcements may be released upon
the discovery of new information identified during the investigation.
［Reference：Status of Unit 4 to 6 at the occurrence of the earthquake］
・ Unit 4 had been shut down since November 30
th th
, 2010 due to regular inspection. All
the fuels had been transferred from reactor to spent fuel pool because shroud work
had been conducted.
・ Unit 5 had been shut down since January 3
rd rd
, 2011 due to regular inspection. When
the earthquake occurred, fuel was installed and pressure leakage test for reactor
pressure vessel was being conducted.
・ Unit 6 had been shut down since August 14
th th
, 2010 due to regular inspection. The
period of shutdown had been extended due to a defect found in combustible gas
density control system. When the earthquake occurred, fuel was installed in the
reactor which was in cold shutdown.
Friday, March 11, 2011
2:46 pm Great East Japan Earthquake occurred. 3rd emergency attitude was
automatically announced.
2:47 pm Emergency diesel generator (hereinafter called “DG”) activated automatically in
Unit 5
3 DG activated automatically at Unit ６
3:06 pm Emergency Center was established at the head office (Recognizing the degree
of damages caused by the earthquake, restoring blackouts)
3:27 pm 1st seismic sea wave arrived
3:35 pm 2nd seismic sea wave arrived
3:36 pm 2 DG in Unit 6 tripped
3:38 pm All AC electric power supply was lost in Unit 4
3:40 pm All AC electric power supply was lost in Unit 5
3:42 pm It was determined that a specific incident stipulated in article 10,clause 1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness (loss of all AC
electric supply) occurred in Unit １
※ ※
，２
※ ※
，３
※ ※
，４
※ ※
and ５
※ ※
and it was reported
to the government offices etc.
Page 48 Page 48
※ On April 24
th th
, it was corrected to Unit 1, 2 and 3.
3:42 pm 1st emergency attitude was announced. Contingency Planning Center was
established
(Later, incorporated with Emergency center)
4:36 pm 2nd emergency attitude was announced
8:50 pm Fukushima prefecture ordered the residents within 2km radius of the periphery of
Fukushima Daiichi Nuclear Power Station to evacuate
9:23 pm Prime Minister ordered the residents within 3km radius of the periphery of
Fukushima Daiichi Nuclear Power Station to evacuate, and the residents within
3km to 10km radius of the periphery to evacuate indoors
Saturday, March 12, 2011
12:30 am Government confirmed the completion of evacuation of the residents (3km
radius of the periphery of Fukushima Daiichi Nuclear Power Station in
Futaba Town and Okuma Town, reconfirmed at 1:45 am)
4:55 am Increase of the radiation dose was confirmed and it was informed to the
government offices etc.
5:44 am Prime Minister ordered the residents 10km radius of the periphery of Fukushima
Daiichi Nuclear Power Station.
6:06 am Pressure in reactor pressure vessel was reduced by opening a valve on the
top in Unit 5.
7:11 am Prime Minister arrived at Fukushima Daiichi Nuclear Power Station
8:04 am Prime Minister departed from Fukushima Daiichi Nuclear Power Station
8:13 am Power became available from DG in Unit 5 and 6
4:27 pm As the radiation dose exceeded 500μSv/h (1,015μSv/h) at the monitoring post, it
was determined that a specific incident stipulated in article 15, clause 1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness (Extraordinary
increase in radiation dose at the border of the site) occurred and it was reported
to the government offices etc.
6:25 pm Prime Minister ordered the residents 20km radius of the periphery of Fukushima
Daiichi Nuclear Power Station to evacuate.
Page 49 Page 49
Sunday, March 13, 2011
8:56 am As the radiation dose exceeded 500μSv/h (882μSv/h) at the monitoring post, it
was determined that a specific incident stipulated in article 15, clause 1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness (Extraordinary
increase in radiation dose at the border of the site) occurred and it was reported
to the government offices etc. at 9:01 am.
11:00 am Prime Minister ordered the residents 20km to 30km radius of the periphery of
Fukushima Daiichi Nuclear Power Station to evacuate.
1:20 pm Water injection by condenser pump powered by DG was initiated in Unit6
(continued intermittently)
2:15 pm As the radiation dose exceeded 500μSv/h (905μSv/h) at the monitoring post, it
was determined that a specific incident stipulated in article 15, clause 1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness (Extraordinary
increase in radiation dose at the border of the site) occurred and it was reported
to the government offices etc. at 2:23 pm.
6:29 pm Water injection by condenser pump powered by DG was initiated in Unit5
(continued intermittently)
Monday, March 14, 2011
2:20 am As the radiation dose exceeded 500μSv/h (751μSv/h) around the main gate, it
was determined that a specific incident stipulated in article 15, clause 1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness (Extraordinary
increase in radiation dose at the border of the site) occurred and it was reported
to the government offices etc. at 4:24 am.
2:40 am As the radiation dose exceeded 500μSv/h (650μSv/h) at the monitoring post, it
was determined that a specific incident stipulated in article 15, clause 1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness (Extraordinary
increase in radiation dose at the border of the site) occurred and it was reported
to the government offices etc. at 5:37 am.
4:00 am As the radiation dose exceeded 500μSv/h (820μSv/h) at the monitoring post, it
was determined that a specific incident stipulated in article 15, clause 1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness (Extraordinary
increase in radiation dose at the border of the site) occurred and it was reported
to the government offices etc. at 8:00 am.
4:08 am Temperature in spent fuel pool of Unit 4 was confirmed to be ８４℃
9:12 am As the radiation dose exceeded 500μSv/h (518.7μSv/h) at the monitoring post, it
Page 50 Page 50
was determined that a specific incident stipulated in article 15, clause 1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness (Extraordinary
increase in radiation dose at the border of the site) occurred and it was reported
to the government offices etc. at 9:34 am.
9:35 pm As the radiation dose exceeded 500μSv/h (760μSv/h) when measured by the
monitoring car, it was determined that a specific incident stipulated in article 15,
clause 1 of Act on Special Measures Concerning Nuclear Emergency
Preparedness (Extraordinary increase in radiation dose at the border of the site)
occurred and it was reported to the government offices etc. at 10:35 pm.
Tuesday, March 15, 2011
Approx.6:00?6:10 am
Explosive sound was confirmed. Later, damage to the roof of reactor building's
5 Five
th th
floor in Unit 4 was confirmed
6:50 am As the radiation dose exceeded 500μSv/h (583.7μSv/h) around the main gate, it
was determined that a specific incident stipulated in article 15, clause 1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness (Extraordinary
increase in radiation dose at the border of the site) occurred and it was reported
to the government offices etc. at 7:00 am.
7:55 am Damage to the roof of reactor building's 5
th th
floor in Unit 4 was reported to
government's offices etc.
8:11 am Damage to reactor building in Unit 4 was confirmed. Also, as the radiation dose
exceeded 500μSv/h (807μSv/h) around the main gate, it was determined that a
specific incident stipulated in article 15, clause 1 of Act on Special Measures
Concerning Nuclear Emergency Preparedness (Extraordinary release of
radiation materials caused by fire explosion) occurred and it was reported to the
government offices etc. at 8:36 am.
9:38 am Fire was confirmed around north west part of 3
rd rd
floor in reactor building of Unit 4.
It was reported to the government offices etc. at 9:38 am.
Approx. 11:00 am
TEPCO staff confirmed that the fire at reactor building of Unit 4 was off. It was
reported to government offices etc. at 11:45 am.
4:00 pm As the radiation dose exceeded 500μSv/h (531.6μSv/h) at the main gate, it was
determined that a specific incident stipulated in article 15, clause 1 of Act on
Special Measures Concerning Nuclear Emergency Preparedness (Extraordinary
increase in radiation dose at the border of the site) occurred and it was reported
Page 51 Page 51
to the government offices etc. at 4:22 pm.
11:05 pm As the radiation dose exceeded 500μSv/h (4548μSv/h) around the main gate, it
was determined that a specific incident stipulated in article 15, clause 1 of Act
on Special Measures Concerning Nuclear Emergency Preparedness
(Extraordinary increase in radiation dose at the border of the site) occurred
and it was reported to the government offices etc. at 11:20 pm.
End End
Original Japanese text:
cell phone) was utilized to order evacuation for field workers. Shift operators
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