PEER REVIEW: Daini, Onagawa & Tokai

These are notes we have on events and damage at the other nearby reactors during the 3-11 quake/tsunami. We are trying to detail all of the events and risk factors at these other reactors to see what worked and what failed at these during the disaster. There may have been risks or near misses at these other facilities that were somewhat ignored due to the events at Daiichi.


Daini Reactors



This flooded the pump rooms used for the essential service water system transferring heat to the sea, the
ultimate heat sink of the reactors
In unit 3, one seawater pump remained operational
The steam powered reactor core isolation cooling system (RCIC) in all 4 units was activated and ran as needed
to maintain water level
At the same time, operators utilized the safety relief valve systems to keep the reactor pressures from getting
too high by dumping the heat to the suppression pools
In unit 3, the residual heat removal system (RHR) was started to cool the suppression pool and later brought
the reactor to cold shutdown on March 12
In units 1, 2, and 4 heat removal was unavailable, so the suppression pools began heating up and on March 12,
the water temperature in the pools of units 1, 2, and 4 topped 100 °C between 05:30 and 06:10 JST, removing
the ability to remove pressure from the reactor and drywell
Operators had to prepare an alternate injection line for each unit as the RCIC cannot run indefinitely only while
there is sufficient pressure and steam in the reactor to drive its turbine, once reactor pressure drops below a
certain level, the RCIC shuts down automatically
Operators prepared for this and setup an alternate injection line using a non-emergency system known as the
Makeup Water Condensate System to maintain water level which was an accident mitigation method TEPCO
put in place at all its nuclear plants. The system was started and stopped in all 4 units, including unit 3, as
needed to maintain the water level
The RCICs in each unit later shut down due to low reactor pressure
Operators had to also use the MUWC and the makeup water purification and filtering (MUPF) system to try to
cool the suppression pool and drywell in addition to the reactor to prevent the drywell pressure from getting too
Water injection into unit 4 was later switched from the MUWC to the High Pressure Core Spray (HPCS) system,
part of the Emergency Core Cooling System. While the water level was maintained in the three units using
emergency water injection, pressures in the containment vessel continued to rise and the operators prepared
to vent the containments making restoration of heat removal urgent. Unit 1 was prioritized as it had the highest
drywell pressure
The service seawater system pumps in the pump room were repaired in units 1, 2 and 4 starting March 13th
and cooling was switched to the Residual Heat Removal System (RHR).
The RHR systems were first activated to cool down the suppression pools (torus) and drywells, and water
injections were made to the reactors using the Low Pressure Coolant Injection (LPCI) mode as needed

Coolant temperatures below 100 °C (cold shutdown) were reached in reactor 2 about 34 hours after the
emergency shut down (SCRAM) restoring the ability to lower the pressure of the reactor via the torus. Reactors
1 and 3 followed at 1:24 and 3:52 on March 14 and Reactor 4 at 7:00 on March 1. The loss of cooling water
at reactors 1, 2 and 4 was classified a level 3 on the International Nuclear Event Scale (serious incident) by
Japanese authorities as of March 18.

Officials made preparations for release of pressure from the plant on March 12. As of March 20, however, no
pressure release had been reported.

An evacuation order was issued to people living within 3 kilometres (1.9 mi) of the plant, subsequently
expanded to 10 km (6.2 mi). Air traffic was restricted in a 10 km (6.2 mi) radius around the plant, according to a
NOTAM. These zones were superseded by the 20 km evacuation and 30 km no-fly zones around Fukushima I
on March 12 and 15, respectively.

TEPCO announced that a worker who had been seriously injured by the earthquake and trapped in the crane
operating console of the exhaust stack was transported to the ground at 5:13 p.m. and confirmed dead at 5:17

Smoke was escaping from one of the buildings on 30 March 2011. It was emitted from equipment which
supplies electrical power to a motor pump that collects outdoor water. The smoke stopped after workers
disconnected the motor.

By March 15, all four reactors of Fukushima II reached cold shutdown which remained non-threatening through

As of June 2011, 7,000 tons of seawater from the tsunami remained in the plant. The plant planned to release it
all back into the ocean, as the tanks and structures holding the water were beginning to corrode. Approximately
3,000 tons of the water was found to contain radioactive substances, and Japan’s Fisheries Agency refused
permission to release that water back into the ocean.

On December 26, 2011, the Prime Minister officially cancelled the nuclear emergency declaration for the
Fukushima Daini plant officially ending the incident. However, the emergency situation continues at the much

more heavily damaged Fukushima Daiichi plant.

On February 8, 2012, opened to news media for the first time since 2011 Tōhoku earthquake and tsunami.

On March 11, 2011, a 9-meter-high tsunami struck the No. 2 plant, while the No. 1 plant was hit by a 13-meter-
high tsunami. The tsunami caused the No. 2 plant’s seawater pumps, used to cool reactors, to fail.

Of the plant’s four reactors, three were in danger of meltdown. One external high-voltage power line still
functioned, allowing plant staff in the central control room to monitor data on internal reactor temperatures and
water levels.

2,000 employees of the No. 2 plant worked to stabilize the reactors. Some employees connected 200-meter
sections of cable, each weighing more than a ton, over a distance of 9 kilometres.

It is pointed out only 40 employees would have been at the plant if the earthquake had occurred in the evening
or on a weekend. According to the head of the plant, the plant was near meltdown

Onagawa Reactors



The Onagawa-3 unit was used as a prototype for the Higashidori Nuclear Power Plant.

Unit 3 conforms fully to ISO 14001, a set of international environmental management standards.

Unit 3’s waste heat water leaves 7 degrees Celsius higher than it came in and is released 10 meters under the
surface of the water, in order to reduce adverse effects on the environment

Unit 3 March 11, 2011 2011 Tōhoku earthquake damaged the turbines after a fire broke out and was shut down

On April 8, 2011, a leak of radioactive water spilled from pools holding spent nuclear fuel rods following the
2011 Tōhoku earthquake , the nuclear safety agency said, was reported by Kyodo News

A fire from the turbine section of the plant following the 2011 Tōhoku earthquake was reported by Kyodo News.

On March 13, 2011, levels of radiation on site reached 21μSv/hour, a level at which Tohoku Electric Power
Company were mandated to declare state of emergency, and they did so at 12:50, declaring the lowest-level
such state. Within 10 minutes the level had dropped to 10μSv/hour.The Japanese authorities assume the
temporarily heightened values were due to radiation from the Fukushima I nuclear accidents and not from
the plant itself. On March 13 20:45 UTC, the IAEA announced that radiation levels at the Onagawa plant had
returned to normal background levels.

The three units remain in cold shutdown since the earthquake of 11 March.

Two hundred people who lost their homes to the tsunami took refuge in the plant.

The April 7th aftershock damaged 2 of the 3 external power lines to the plant but cooling was maintained
through the third line.

Tokai Reactors



Unit 1 British Magnox 159 MW reactor operated from 1966 to 1998 and was first reactor to operate in
Unit 2 BWR5 was the first reactor in Japan to operate over 1000 MWj
Unit 2 had shutdown automatically after the earthquake

Following the 2011 Tōhoku earthquake and tsunami the number 2 reactor was one of eleven nuclear
reactors nationwide to be shut down automatically.

It was reported on 14 March that a cooling system pump for the number 2 reactor had stopped working.
Japan Atomic Power Company stated that there was a second operational pump and cooling was working,
but that two of three diesel generators used to power the cooling system were out of order.

In 2007, Ibaraki Prefecture assumed possible attack tsunami height 5.7 metre, and additional seawall
construction to immune to 6.1 metre tsunami height had been conducted and completed 2 days before
2011 Tōhoku earthquake and tsunami, 9 March 2011. The height of 5.4 metre tsunami attacked on
11March to the plant. These fact are disclose to news media at the time of plant inspection by government
on 13 February 2012.

During the earthquake of 11 March 2011, the Tokai-power plant suffered external power-loss, just like
it happened in Fukushima. Thanks to extra and voluntarily measurements taken by the Japan Atomic
Power, the reactors could still be cooled safely, and another major accident was prevented. In 2002
was concluded, based on an evaluation technology adopted by the Japan Society of Civil Engineers,
that at this place tsunami waves could be expected as high as 4.86 meters. After the government of the
prefecture Ibaraki in October 2007 their own calculations published, and estimated that these waves

could be as high as 6 to 7 meters. Japan Atomic Power changed its wave level assumption to 5.7 meters.
The reconstruction works were started in July 2009 to raise the height of the 4.9-meter protection around
the plant to 6.1 meters, in order to protect the seawater pumps designed to cool an emergency diesel
generator. Although most of the works were completed by September 2010, cable holes in the levee were
still not fully covered. This work was scheduled to take place before around May 2011. When the tsunami
did hit the Tokai plant in March, the waves were 5.3 to 5.4 meters in height, even higher than earlier
estimations but still 30 to 40 centimeters lower than the last assumption. The Tokai plant suffered a loss of
external power-supply like it happened in Fukushima. Even the levee was overrun in Tokai, but only one
of three seawater pumps did fail, and the reactors could be kept stable and safe in cold shutdown with the
emergency diesel generator cooled by the two remaining seawater pumps. [7]

After the disaster in Fukushima a stress-test was ordered by the Japanese government, after
investigations the electrical installations of the Tokai Daini reactor did not meet the earthquake-resistance
standards set by the government.

Petitions have been signed to try and prevent the unit 2 reactor from starting again

This article would not be possible without the extensive efforts of the SimplyInfo research team
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