Grid Failure + ECCS Failure Part 3 – reactor 3.

The following post consists of highly selected quotes from the TEPCO document chronologies given by the text “Measures Taken at Fukushima Daiichi Nuclear Power Station and Fukushima Daini Nuclear Power Station (December 2011 Edition)”. The quotes are taken from the 166 page appendices of the document and focus upon the timing of events and the consequences of grid and ECCS failures at Fukushima Diiachi. The document is authored by TEPCO, Japan and the appendix only is available at :
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/111222e18.pdf

Chronology of Main Events at Fukushima Daiichi Nuclear Power Station
Unit 3 from Impact of Earthquake through Tuesday, March 15

Friday March 11 2011
16:03 The RCIC was started up manually.
15:38 All AC power supplies were lost.
11:13 The DDFP started up automatically.
11:36 The DDFP stopped.
11:36 The RCIC stopped automatically.
12:06 The DDFP activated and started an alternative S/C spray.
12:35 The High Pressure Coolant Injection System (hereafter the “HPCI”)
started up automatically (reactor water level low).
Sunday, March 13, 2011
2:42 The HPCI was stopped in order to shift to the DDFP as an alternative
means of water injection into the reactor.
2:45 An operator tried opening one Safety Release Valve (hereafter “SRV”) but the valve did not open. Subsequently, the operator tried opening all the valvesone by one but none of them opened.
3:05 It was reported to the Main Control Room that the formation of an alternative line of water injection into the reactor had been completed.
3:51 The reactor water level meters were restored.
4:52 It was confirmed that although an operator had opened the large valve of the vent valve (AO valve) of the suppression chamber (hereafter the “S/C”), it
closed because the filling pressure of the air cylinder was 0.
5:08 Alternative spraying the S/C with the DDFP started (discontinued at 7:43).
5:10 The Power Station failed to inject water into the reactor through the RCIC.
The Emergency Countermeasures Headquarters accordingly decided on the
occurrence of a specified event (loss of the reactor cooling function) subject
to the Provisions of Article 15 Clause 1 of the Disaster Prevention Act and
reported this to the competent government departments and agencies at 5:58.
5:15 The Site Superintendent instructed operators to complete the formation
of a vent line except for the rupture disk.

5:23 Operators started replacing air cylinders to perform an “open” operation of
the large valve of the vent valve (AO valve) of the S/C.
5:50 Press release on vent operation.
6:19 The Emergency Countermeasures Headquarters decided on the reach of the
top of active fuel (hereafter “TAF”) at 4:15 and reported the event to the
competent government departments and agencies.
7:35 The Emergency Countermeasures Headquarters reported the result of its
dosage assessment in the event that the vent was operated to the competent
government departments and agencies.
7:39 Operators started spraying the primary containment vessel. The Emergency
Countermeasures Headquarters reported the operation to the competent
government departments and agencies at 7:56.
8:35 Operators opened the vent valve (MO valve) of the primary containment
vessel (“hereafter the “PCV”).
8:41 By opening the large valve of the vent valve (AO valve) of the S/C, the
formation of a vent line, except for the rupture disk, was completed, and
reported to the competent government departments and agencies at 8:46.

8:56 In the area around monitoring post No. 4, a radiation dose exceeding 500μSv/h (882μSv/h) was measured. The Emergency Countermeasures Headquarters accordingly decided on the occurrence of a specified event (abnormal rise in radiation dose on the site boundary) subject to the provisions of Article 15 Clause 1 of the Nuclear Disaster Prevention Act and reported the event to the competent government departments and agencies at
9:01.
9:08 (Approx.) Operators manipulated the safety release valve to rapidly reduce the reactor pressure. The Emergency Countermeasures Headquarters informed the
competent government departments and agencies at 9:20 of its plan to start
water injection into the reactor through the Fire Protection System line.
9:25 A fire engine started freshwater (containing boric acid) injection into the
reactor through the Fire Protection System line.
9:36 It was confirmed that the venting operation had triggered a decrease in
the drywell (hereafter the “D/W”) pressure at around 9:20. The
Emergency Countermeasures Headquarters also reported to the
competent government departments and agencies that it had started
water injection into the reactor through the Fire Protection System line.
10:30 The Site Superintendent instructed operators to work with seawater
injection in mind.
11:17 It was confirmed that the large valve of the vent valve (AO valve) of the S/C had been in a “closed” state (due to a decrease in the pressure of the
operational air cylinders).
12:20 Injection of freshwater completed.
13:12 The fire engine started seawater injection into the reactor through the
Fire Protection System line.
14:15 In the area around monitoring post No. 4, a radiation dose exceeding
500μSv/h (905μSv/h) was measured. The Emergency Countermeasures
Headquarters accordingly decided on the occurrence of a specified event
(Abnormal rise in radiation dose in the site boundary) subject to the
provisions of Article 15 Clause 1 of the Nuclear Disaster Prevention Act and
reported the event to the competent government departments and agencies at
14:23.
14:31 The measurement results of radiation doses were reported, which indicated
300mSv/h or more at the double door on the north side of the Reactor
Building and 100mSv/h on the south side.
14:45 (Approx.) The radiation dose in the area surrounding the double door of the Reactor Building was on the increase. Like the Reactor Building of Unit 1, there wasa possibility of hydrogen having accumulated in the Reactor Building of Unit 3. Since the risk of explosion was high, workers started to evacuate their work sites (work resumed at around 17:00).

Monday, March 14, 2011

5:20 An operator started the “open” operation of the small valve (AO valve) of the vent valve of the S/C.
6:10 An operator confirmed the “open’ state of the small valve of the vent valve
(AO valve) of the S/C.
6:30 (Approx.) The D/W pressure increased and there was a possibility of explosion, hence workers started evacuation (work resumed at around 7:35).
9:05 Seawater supply started from the Shallow Draft Quay to the reversing valve
pit.
9:12 In the area around monitoring post No. 3, a radiation dose exceeding
500μSv/h (518.7μSv/h) was measured. The Emergency Countermeasures
Headquarters accordingly decided on the occurrence of a specified event
(Abnormal rise in radiation dose on the site boundary) subject to the
provisions of Article 15 Clause 1 of the Nuclear Disaster Prevention Act and
reported the event to the competent government departments and agencies at
9:34.
11:01 An explosion occurred at the Reactor Building.

16:30 (Approx.) The fire engine and hose sustained damage in the explosion, which led to the discontinuance of seawater injection. The fire engine and hose were thus replaced and a new line of water injection into the reactor from the
Shallow Draft Quay was formed. Seawater injection was resumed.
21:35 In the area around the main gate, a radiation dose exceeding 500μSv/h
(760μSv/h) was measured. The Emergency Countermeasures Headquarters
accordingly decided on the occurrence of a specified event (Abnormal rise in
radiation dose on the site boundary) subject to the provisions of Article 15
Clause 1 of the Nuclear Disaster Prevention Act and reported the event to the
competent government departments and agencies at 22:35.

Tuesday, March 15, 2011

6:00 to 6:10 (Approx.) A large impulsive sound broke out. The ceiling on the Unit 4 side of the Main Control Room shook.
6:50 In the area around the main gate, a radiation dose exceeding 500μSv/h
(583.7μSv/h) was measured. The Emergency Countermeasures Headquarters
accordingly decided on the occurrence of a specified event (Abnormal rise in
radiation dose on the site boundary) subject to the provisions of Article 15
Clause 1 of the Nuclear Disaster Prevention Act and reported the event to the
competent government departments and agencies at 7:00.
7:00 The Emergency Countermeasures Headquarters informed the competent
government departments and agencies of a temporary evacuation of personnel
to Fukushima Daini, except for the personnel needed for monitoring and other
operations.
7:55 It was confirmed that steam was rising on the upper side of the Reactor
Building, which was reported to the competent government departments and agencies.

8:11 In the area around the main gate, a radiation dose exceeding 500μSv/h
(807μSv/h) was measured. The Emergency Countermeasures Headquarters
accordingly decided on the occurrence of a specified event (Abnormal
emission of radioactive materials on fire or explosion, etc.) subject to the
provisions of Article 15 Clause 1 of the Nuclear Disaster Prevention Act and
reported the event to the competent government departments and agencies at
8:36.
11:00 The Prime Minister issued an order confining local residents indoors staying in areas within a 20 to 30-km radius of the Fukushima Daiichi power station.
16:00 In the area around the main gate, a radiation dose exceeding 500μSv/h
(531.6μSv/h) was measured. The Emergency Countermeasures Headquarters
accordingly decided on the occurrence of a specified event (Abnormal rise in
radiation dose on the site boundary) subject to the provisions of Article 15
Clause 1 of the Nuclear Disaster Prevention Act and reported the event to the
competent government departments and agencies at 16:22.
23:05 In the area around the main gate, a radiation dose exceeding 500μSv/h
(4548μSv/h) was measured. The Emergency Countermeasures Headquartersaccordingly decided on the occurrence of a specified event (Abnormal rise in radiation dose on the site boundary) subject to the provisions of Article 15 Clause 1 of the Nuclear Disaster Prevention Act and reported the event to the competent government departments and agencies at 23:20.
End of file

Fukushima Daiichi Nuclear Power Station Unit 3
State of Alternate Coolant Injection

○ Activities after “16:03 of March 11 when manually starting up the Reactor Core Isolation Cooling System (hereafter the “RCIC”)” (Reactor 3)

Although all the AC power supplies were lost, the DC power supply remained intact and available. Pursuant to the operation procedure description, the Emergency Countermeasures Headquarters worked to reserve the reactor water level by using the Reactor Core Isolation Cooling System (hereafter the “RCIC“) and the High Pressure Coolant Injection System (hereafter the “HPCI“), both of which use DC power for operation control.

[Reserving the reactor water level by the RCIC]
・ To stabilize the reservation of the reactor water level by the RCIC, operators took measures to prevent automatic shutdown due to high reactor water level and to save the battery power needed for operation control.
 To prevent automatic shutdown due to the high reactor water level, the Main Control Room operated the RCIC control panel to form the following two lines that supply water to a water injection line in the reactor and a test line used for regular functional tests (from the condensate storage tank (hereafter the “CST”), water source, to a line returning to the CST), while monitoring the
reactor water level. The Main Control Room defined the range of water level arrangements used to reserve the water level.

Two operators were assigned to monitor the reactor water level, while a further two operators were assigned to operate the RCIC and exchanged information with each other. In addition, for the next means of water injection, operators prepared for smooth HPCI startup after stopping the RCIC by, for example, tagging switches, etc. on the HPCI control panel.

It was crucial to preserve battery power. Thus, the operators set flow rates by adjusting the opening of valves on the test line and with the FIC so that the reactor water level would change slowly, meaning a reduced number
of valves in operation and the flow instrument controller (hereafter the “FIC”) operation.
Operators also repeated the method involving an operator changing the flow rate setting when the reactor water level approaches the upper or lower
end of the water level adjustment range (rated flow: 25.2L/s) within the range 100% to approx. 75%).

 To save even more battery power, operators disconnected the loads of monitoring instruments, control panels and computers from others except those facilities crucial for monitoring and operation control. Monitoring instruments are doubled into systems A and B, only one of which was used at any one time to
reduce the battery power consumption. In addition, emergency lights and clocks
in the Main Control Room were disconnected while fluorescent lights of other
rooms were pulled off.

[Starting up the diesel-driven fire pump (hereafter the “DDFP”) and alternative spraying of the S/C (“S/C”)]
・ After the earthquake, the status indicator of the DDFP, used for alternative water injection, indicated a halt state in the Main Control Room. At 3:27 on March 12, an operator tried manipulating operation switches in the Main Control Room. However, the DDFP did not start up.
・ Since the RCIC was injecting water into the reactor, steam from the motive turbine was exhausted into the S/C, hence from March 12, the drywell (hereafter the “D/W”) pressure was on the rise. Accordingly, the Emergency Countermeasures
Headquarters studied alternative spraying of the S/C using the DDFP, to limit the rises in S/C and D/W pressures. To this end, operators confirmed operation
procedures and locations of valves based on the AM operation procedure
description.
・ Operators were subdivided into two teams to form an alternative line of spraying the S/C through the residual heat removal system (“RHR”) from the Fire Protection System (“FP”) line. The two teams headed for the Reactor Building and the Turbine Building. Since the solenoid valves for the line had no power source, the Main Control Room was unable to operate those valves. Putting on a full-face mask, operators using flashlights amid complete darkness manually opened five valves, including the RHR valve on the morning of March 12.

○ Activities “after 11:36 of March 12 when stopping the RCIC”
[Stopping and re-starting the RCIC]

While operators were steadily maintaining the reactor water level, the RCIC status indicator in the Main Control Room indicated a halt state. Consequently, the indication values, including those of flow rates and discharge pressure meters, also indicated zero, hence operators confirmed that the RCIC had stopped. However, no “stop” alarming functioned due to the loss of power.
・ Although an operator tried starting up the RCIC on its control panel in the Main Control Room, the RCIC soon ceased to operate after starting up, hence two
operators headed for the RCIC room in the basement of the Reactor Building to
check the conditions. They wore a full-face mask and long boots used for outside
patrols. Using flashlights, they entered the RCIC room through the HPCI room and
found that the floor was covered in water ankle-deep. Water also dropped from the ceiling of the room on the steam stop valve, etc. of the RCIC.
・ The operators checked the site and confirmed that there was no defect of the of the steam stop valve mechanical structure units. When an operator in the Main Control Room tried starting up the RCIC, the steam stop valve closed soon after startup, and the RCIC stopped.

[Maintaining the reactor water level and reducing reactor pressure with the HPCI]

Operators were urged to check the conditions of the halted RCIC and for startup
operation. At 12:35 on March 12, the HPCI automatically started up due to the low reactor water level and resumed water injection into the reactor. Since the motive turbine of the HPCI spent the steam from the reactor, the reactor pressure started to go down.
・ As was done for the RCIC, operators manipulated switches on the HPCI control panel to form two water supply lines, namely the reactor water injection line and the test line. Two operators were assigned to monitor the reactor water level, and a further two operators to operate the HPCI. Since the flow rate of the latter exceeded that of RCIC, the reactor water level rose rapidly, making it difficult for the operators to set the HPCI flow rate. Thus, after setting more variable water level adjustment, the operators maintained the reactor
water level to prevent automatic shutdown of the HPCI due to the high
reactor water level. In addition, operators set the minimum flow valve
to shut down to prevent a rise in the water level of the destination S/C.
・ To save battery power, as with RCIC measures, the operators set flow rates
by adjusting the opening of the valves on the test line and with the FIC so that the reactor water level changes slowly. The operators repeated the method whereby they changed the flow rate settings when the reactor water level approached the upper or lower ends of the water level adjustment range (flow rate: 268L/s) within a range of 100 to approx. 75%.

At 20:36 on March 12, the power of the reactor water level meter was lost, which resulted in the reactor water level not being monitored by operators. The flow rate setting of the HPCI was thus raised slightly to monitor the operational state with the reactor pressure and HPCI discharge pressure, etc.

○ Activities “after 2:42 on March 13 when the HPCI halted”
[State of the HPCI halt]

The rotation speed of the HPCI turbine was lower than the operational range specified in the operation procedure description, while the discharge pressure of the HPCI was so low that it could have stopped anytime. Consequently, operators were unable to monitor the reactor water level, which hence remained unknown.
・ Operators monitored the reactor pressure, the HPCI discharge pressure, etc. while considering whether “water was being injected into the reactor,” “whether the reactor water level is being maintained,” and “when to shift to the DDFP,” etc.
・ Under the circumstances, from 2:00 on March 13, the reactor pressure that had
remained stable at approx. 1MPa began to decline. The power generation team and
the Main Control Room were afraid of possible damage to facilities due to the
decline in the reactor pressure, since it would trigger a further decline in the rotation speed of the HPCI turbine, exposing the facilities to greater vibration and possibly causing damage.* In addition, since the reactor pressure and HPCI discharge pressure were nearly equal, The Power Station estimated that the HPCI was unable to inject water into the reactor. Under these circumstances, the Power Station decided to inject water into the reactor through the DDFP, as an alternative means, and stop the HPCI, hurriedly.

* In the event that damage occurs around the HPCI turbine, steam from the reactor will be emitted in the HPCI room as motive steam.
・ Operators headed for the Reactor Building prior to stopping the HPCI, in order to check the DDFP operational state and manually open the RHR injection valve prior to shifting to alternative water injection into the reactor from the alternative spray of the S/C.
・ At 2:42 on March 13, an operator informed the power generation team of the HPCI of the halt, pressed the HPCI button on the HPCI control panel in the Main Control Room, closed the steam inlet valve of the HPCI turbine with the switch, and halted the HPCI.

(Paul Langley: as a brief aside: the turbine spoken of above is the emergency core cooling system turbine which is stream by the pressure difference between the pressure vessel and the torus. A steam line from the pressure vessel is connected to the turbine and a steam line connects the outlet of the turbine to the torus. Thus, when activated in an emergency, the turbine drives a pump which impels water flow through to the HCPI and the RCCI. The heat is removed from the circuits by condensers located on the roofs of the reactors. The torus itself, having a large surface area radiates some heat in a crude heat exchange with its surroundings. The bearings of the turbine burn out and pressure difference between the pressure vessel and the torus diminishes as the turbine works. The American expectation was and is that any station blackout could not possibly last more than 8 hours anywhere on planet earth under any circumstance. Why they believed and believe that profound lie is based not in reality but upon nuclear ideology – “reactors are safe and such an event is irrational to consider”. I hope this is clear to everyone. The chronology of reactor 3 is the most profound description of the reactor’s emergency core cooling systems failing one after the other as time went on without grid reconnection. With the explosion and damage to the roof, the main thing to report in terms of reactor function would be the loss of the ECCS heat removal condensers. I expect severe abuse from nuclear “experts” who, since 1969, have unable to come up with any solution to these well known, decades old, safety concerns regarding station blackout.

In emergency, “the ultimate heatsink” is NOT the primary cooling loop, it is the ECCS multiple cooling loops. Supposed nuclear experts such as Gundersen have done no service to the world in their phony explanations to the world. imo so sue me Arnie.)

From 5:08 on March 13, operators tried starting up the RCIC on the RCIC control panel in the Main Control Room after setting a low flow rate with the FIC so that the bite-in state of the mechanical structure would have no impact during the RCIC startup. However, the mechanical structure of the steam stop valve was dislocated, resulting in the closure of the valve and stoppage of the RCIC.
・ Since the RCIC startup failed, the Emergency Countermeasures Headquarters
decided at 5:10 on March 13 that the event came under the category of a specified event (Loss of reactor cooling function) as defined in the provisions of Article 15 Clause 1 of the Nuclear Disaster Prevention Act, and reported the event to the competent government departments and agencies at 5:58.

[Preparing an alternative water injection line in the reactor with a fire engine]
・ While restoring the SLC and other permanent reactor water injection facilities, the Emergency Countermeasures Headquarters concurrently arranged fire engines.
・ At around 5:30 on March 13, fire engines owned by Kashiwazaki Kariya Nuclear
Power Station, which stood by in Fukushima Daini, left Fukushima Daini and
arrived at Fukushima Daiichi at around 6:30. When operators checked the fire
engines on the side of Units 5 and 6 at around 6:00, they were identified as available for operation and thus collected for water injection into the reactor of Unit 3.
・ As was done for Unit 1, the formation of a seawater injection line from the reversing valve pit of Unit 3 as a water source was completed. Subsequently, however, the line was changed to a freshwater injection line from the anti-fire water tank as a water source.

Water injection into the reactor with the DDFP or fire engines required a reduction of the reactor pressure with SRV. The Emergency Countermeasures Headquarters estimated that ten 12V batteries (DC power 125V) would be necessary to start up the SRV. However, such batteries had been used for the restoration, etc. of the instruments of Units 1 and 2.
・ At around 7:00 on March 13, the Emergency Countermeasures Headquarters asked
TEPCO employees in the Seismic Isolated Building to offer batteries of their private cars. After a sufficient number of willing employees had gathered, they removed the batteries from their cars. These batteries were then gathered together in front of the Seismic Isolated Building, whereupon five members of the recovery team transported them with their private car to the Main Control Room of Unit 3.

・ At around 9:08 on March 13, the SRV was opened. Reduction of the reactor pressure started rapidly. Along with reduction of the reactor pressure, operators started water injection with the DDFP and from 9:25, with fire
engines. The Emergency Countermeasures Headquarters requested additional freshwater supply from others. The fire brigade drew up water from the
simulant fuel pool in the Technical Training Center in the Power Station site and other sources, which was then supplied to the anti-fire water tank to continue water injection.
・ At around 9:40 on March 13, the operation to connect ten batteries serially was completed and they were connected to the SRV control panel. Operators opened the SRV with the operation switch and maintained the reduction in pressure

[Studying measures to prevent explosions]

After the explosion at the Reactor Building of Unit 1, the Nuclear Restoration Teamof the Head Office Disaster Control HQ believed from an early stage that hydrogen had caused the explosion and accordingly started to study how to release accumulating gas in the Reactor Building.
・ At around 9:40 on March 13, the Site Superintendent explained the key to
preventing similar explosions, although the cause of the explosion may not have
been hydrogen. Together with the Head Office Disaster Control HQ, the Emergency
Countermeasures Headquarters started to study preventive measures.

【Evacuating before explosion and study on methods to prevent explosions】
・ At around 14:45 on March 13, the radiation dose behind the double doors of the
Reactor Building indicated approx. 300mSv/h. The Emergency Countermeasures
Headquarters anticipated another explosion of accumulated hydrogen in the Reactor Building like that of Unit 1 and, therefore, decided to temporarily evacuate workers in the Main Control Room and field.
・ After the evacuation, at around 17:00 on March 13, the Emergency Countermeasures Headquarters cancelled the evacuation of the workers engaged in checking venting lines for soundness and reworked the seawater injection line. Workers resumed operations.

On the afternoon on March 13, the Chief Cabinet Secretary held a press conference on the situation of Unit 3 at the Prime Minister’s Office and announced a possible explosion of hydrogen.
・ Subsequently, as means of releasing the hydrogen in the Reactor Building, a number of methods were proposed including “release of the blowout panel,” “piercing the ceiling of the Reactor Building,” and “using a water jet to make a hole in the Reactor Building wall.” Methods other than the “water jet” carried a high risk of explosion due to the sparks created when making a hole. The high radiation dose on the work site also prevented the adoption of other methods.
・ The Emergency Countermeasures Headquarters focused on studying the “water jet”
method and made arrangement for facilities.

・ The fire brigade, which had been monitoring the water level of the reversing valvepit of Unit 3 and the pressure and flow rate of the fire engine that was injecting water, guided water wagons for water supply to the reversing valve pit of Unit 3.
While the fire brigade was guiding several water wagons, an explosion occurred,
whereupon the surroundings immediately turned white due to smoke, etc. After a
while, debris began to drop from the sky, clattering. To protect themselves, the fire brigade members escaped behind nearby pipes. Although the shelter was inadequate, miraculously, all workers were unscathed.
・ When the surrounding smoke eased off, two injured employees were walking near
the service building of Unit 3. The fire brigade, after calling for workers at the work sites to gather together, started walking to evacuate through the road between Units 2 and 3 where debris was scattered.
・ When the fire brigade members and other workers passed the gate between Units 2 and 3, a truck of the Self Defense Forces of Japan arrived. All the members then got on the loading space of the truck and returned to the Seismic Isolated Building.


Appearance of Unit 3 immediately after the explosion
(Photo taken on March 21, 2011) Source: TEPCO

・ At 11:01 on March 14, an explosion occurred at Unit 3, smoking. Later,
pictures of the building werebroadcasted on TV.
・ The Site Superintendent instructed subordinates to evacuate and check
for safety. The Site Superintendent also ordered the security team to
measure and report radiation doses. Since a tsunami warning had been
issued, Site Superintendent ordered the earliest evacuation.
・ Workers other than operators at the Main Control Room suspended their work and
evacuated to the Seismic Isolated Building.
・ At 11:15 on March 15, the parameters of Unit 3 were reported. The reactor pressures of systems A and B were respectively 0.195 and 0.203MPa. The D/W pressure was 380kPa[abs]. The S/C pressure was 390kPa[abs]. Since parameters remained available and based on the measurement values of the reactor pressure and the Primary Containment Vessel pressure, the Site Superintendent decided that these facilities remained sound.
・ At around 11:30 on March 14, the results of checking personnel for safety were
immediately reported to the Emergency Countermeasures Headquarters. According
to initial reports, some 40 persons were missing and there were several injuries. The Emergency Countermeasures Headquarters requested ambulances via the Head Office Disaster Control HQ (the total injured included four TEPCO employees, three workers of contractor companies, and four soldiers of the Self Defense Forces of Japan).
・ At around 11:40 on March 14, the Emergency Countermeasures Headquarters
confirmed the safety of operators at the Main Control Room. It was reported that a total of seven persons, consisting of six soldiers of the Self Defense Forces of Japan and one worker of a contractor company, were missing. Later, the Self Defense Forces of Japan retreated.

At 13:05 on March 14, when all the operators and workers still remained shocked at a second explosion following that of Unit 1, the Site Superintendent issues the following instruction to take measures for control Unit 2: “The reactor water level of Unit 2 is confirmed as declining. If this state continues, the reactor will reach the TAF (top of active fuel) at around 16:00. We will form a reactor water injection line and restore the reversing valve pit of Unit 3, the water source, by 14:30. Be careful to avoid other explosions. The explosion at Unit 3 might have disrupted facilities.
Do not easily assume that facilities are available for operation.”

・ At 14:50 on March 14, it was reported to the Emergency Countermeasures
Headquarters that the blowout panels on the sea side of Unit 2 were open. (A
subsequent survey identified that the explosion at Unit 1 had caused the opening.)

From 13:05 on March 14, immediately after the instruction of Site Superintendent, the fire brigade headed for the work sites to check the situation. They were exposed to high radiation doses when passing through roads with scattered debris. ・ At around 16:30 of the 14th, The fire engine was started up to resume the seawater injection line. End of file

Activities since the “vent line configuration was completed except for the ruptured discs by opening the suppression chamber vent valve (AO valve) large valve at 8:41 on March 13.”
[Maintenance of the vent line]

From around 2:00 on March 14, the D/W pressure continued to increase* and the rising trend could not be stopped even by increasing the amount of water to be injected to the reactor. Accordingly, we decided to open the S/C vent valve (AO valve) small valve and started the operation of opening the S/C vent valve (AO valve) small valve at 5:20.
Then we finished the opening operation at 6:10.
* 255 kPa [abs](1:30) → 265 kPa [abs](2:00)
・ At 11:01 on March 14, an explosion occurred in the Unit 3 Reactor Building.

(Works on March 15)
・ At 16:00 on March 15, it was confirmed that the S/C vent valve (AO valve) large valve was closed due to the failure of the small generator that had been used for excitation of solenoid valves of the large and small valves. Then we conducted the opening operation at 16:05 by replacing the small generator and exciting the S/C vent valve (AO valve) large solenoid valve.
・ The valve was difficult to keep open due to the difficulty in keeping the drive air pressure and the excitation of the solenoid valve in the air supply line for the S/C vent valve (AO valve) large and small valves, and hence the opening operation was conducted several times.
(S/C vent valve (AO valve) large valve)
 At 21:00 on March 17, the valve was confirmed to be closed; around 21:30 on March 17, opening operation was conducted
 At 5:30 on March 18, the valve was confirmed to be closed; around 5:30 on March 18, opening operation was conducted
 At 11:30 on March 19, the valve was confirmed to be closed; around 11:25 on March 20, opening operation was conducted
 Around 18:30 on April 8, the valve was confirmed to be closed. (S/C vent valve (AO valve) small valve)
 At 1:55 on March 16, opening operation was conducted
 Around 18:30 on April 8, the valve was confirmed to be closed.

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