How

Onagawa

Responded at the Time?
The Nuclear Power Station
That Withstood the Great East Japan Earthquake

A Report from the Scene by
Science Journalist

Wako Tojima

C ont ents

Onagaw a

Where is the boundary between success and failure?

3

How did the plant staff respond at the time?

15

The success of Onagawa was not a “miracle”

4

Narrowing down of contact routes and concentrating on the situation at hand

16

The Great East Japan Earthquake and its unprecedented devastation

4

Ten persons donned fire suits and went to scene of fire17

Most reactors safely achieved cold shutdown

5“We prepared extra sandbags just in case”

18“Let’s all take refuge at the power station!”

19“Just load it up with supplies!”

21
23

Fukushima Daini, where 200 persons hooked up cables
totaling 9 kilometers in length5

Achievement of Stopping, Cooling, and Containing

7

The many layers of readiness at Onagawa

10“Handle normal times with emergencies in mind so that you are able to handle
emergencies like normal times”

A sterling example winning worldwide praise

13“Our power station”

24

The steadfast diligence for seeing things through to successful completion

25

Cover images
The Samenoura community of Ishinomaki City, near the Onagawa Nuclear Power Station, right after thedisaster hit.
Before the disaster, many people in this community were engaged in ﬁshing and living out their daily lives,
but they suffered enormous damage from the tsunami.
With nearly all the homes and other buildings having been washed away, more than 100 residents took
refuge at the Onagawa NPS. (March 2011)*This pamphlet is a translation of the revised version ofan article published in the monthly magazine Hiroba ( No.431) issued by the Tohoku Energy Conference.

Lessons to take us to the futureWith three years having passed since the accident at the Tokyo
Electric Power Company (TEPCO) Fukushima Daiichi Nuclear
Power Station resulting from the Great East Japan Earthquake,efforts continue on raising the safety level of nuclear power plants
throughout Japan. The importance of learning the lessons from this
accident in upgrading safety goes without saying, but at the sametime there is much of value to be learned from the examples of thenuclear power plants that withstood the earthquake and tsunami.
For a case study, science journalist Wako Tojima visited the
Onagawa Nuclear Power Station owned and operated by Tohoku
Electric Power Co., Inc. and filed this report from the scene.

Wako Tojima listens to Superintendent Shun Tsubata
at the Onagawa Nuclear Power Station(Onagawa-cho, Oshika-gun and Ishinomaki City, Miyagi Prefecture),
where work proceeds on raising the ﬂood wall height

1

2

The untiring steps toward
greater safety to be learned
from the nuclear power plantthat withstood the disaster
Where is the boundary between success and failure?
Since the Great East Japan Earthquake of March
11, 2011, I have walked in the disaster sites and haveseen the aftermath up close.
The Fukushima Daiichi Nuclear Power Station
owned by Tokyo Electric Power Co., Inc. had themisfortunate of suffering a major accident. The
Fukushima Daini and Onagawa Nuclear Power

Stations, meanwhile, were able to shutdown safely
even though Fukushima Daini was situatedgeographically close to Fukushima Daiichi
and Onagawa experienced the same or greater levelsof shaking and tsunami waves as Fukushima Daiichi.
What’s more, as the surrounding communities

were devastated by the disaster, the Onagawa siteactually served as a shelter for evacuees.
What was it that decided the very different fatesof these facilities?
I wanted to walk around seeing as many cases as
possible, listening to the stories of those who
experienced it firsthand, and confirming with myown eyes the “boundary between success andfailure.”In the course of documenting this story, I became
convinced that, in addition to learning from failure,
there is much to be learned from success that canhelp take us to the future.

Fukushima Daiichi Nuclear Power Station
when the tsunami arrived

The success of Onagawa
was not a “miracle”
In November 2013 I had the opportunity to give atalk in Taipei. After the Fukushima Daiichi accident,
there was growing concern in Taiwan about thesafety of nuclear power generation, and I was invited
to speak because of a desire to learn more about thesituation in Japan.
My presentation, aided by photograph slides,
showed the situation when I visited nuclear power
plants throughout Japan after the disaster.
I was surprised to discover that in Taiwan, it was
not widely known that nuclear power plants had
survived the Magnitude 9.0 earthquake and tsunami.
After my talk, reporters from various media
pressed me for details about the reasons for the“success” of the Onagawa Nuclear Power Station.
Speaking with confidence and pride, I stated
repeatedly that, “While there are those who see thesuccess of Onagawa as a ‘miracle,’ I don’t agree.
Having visited the site, I believe it was because of
the readiness in place at the time that the reactors
were shut down safely.”
What I would like to talk about here is why I feelthat way.

Fukushima Daini Nuclear Power Station when the tsunami arrived
Photos: Tokyo Electric Power Co.

The Great East Japan Earthquake
and its unprecedented
devastation
At 14:46 on March 11, 2011, an earthquake struck
approximately 130 km off the Sanriku coast, on theocean floor at a depth of around 24 km. The
magnitude was 9.0. Nearly 20,000 people lost theirlives to this, one of the largest quakes ever to strike
Japan.
The intensity of shaking in Japanese scale was
Shindo 6+ at the Fukushima Daiichi Nuclear Power
Station, while Shindo 6- was recorded in
Onagawa-cho, Miyagi Prefecture, the site of the
Onagawa Nuclear Power Station. Peak groundacceleration of 567.5 Gal, an unprecedented level,
was measured in the second basement floor of the
Onagawa Unit 1 reactor building.
Then a tsunami exceeding 18 meters, “as if theentire sea had risen up,” swallowed the town of
Onagawa-cho. Eight percent of the approximately
10,000 residents died, and some 4,411 homes weretotally or partially destroyed.

Fukushima Daiichi Nuclear Power Station following hydrogen-air explosions

3

4

Most reactors safely achieved cold shutdown
Of the 54 nuclear power plants in Japan, those
directly affected by this Great East Japan Earthquake
were the nuclear power-related facilities along the
Pacific coast of eastern Japan.
From the north, these were the Higashidori
Nuclear Power Station owned by Tohoku ElectricPower and the reprocessing plant owned by the Japan
Nuclear Fuel Limited in Aomori Prefecture, theOnagawa plant in Miyagi Prefecture, the Fukushima
Daiichi and Daini Nuclear Power Stations both
owned by TEPCO in Fukushima Prefecture, and theTokai No. 2 Power Station owned by the Japan
Atomic Power Company in Ibaraki Prefecture.
While Units 1 to 4 of Fukushima Daiichi
unfortunately incurred accidents, Units 5 and 6 on
the same site, Fukushima Daini Units 1 to 4 located
10 km away, Onagawa Units 1 to 3 located closer tothe epicenter, and all the other facilities were free ofmajor safety problems.
The status of each individual reactor was varied,such as being stopped for regular inspection, on the
point of being started up, or operating normally; but
looking at the results, most of the plants were able toachieve cold shutdown of their reactors (Fig.1).

Fig.1 Situation at nuclear power stations
at time of Great East Japan Earthquake and after■ Reactor shut down for regular inspection▲ Starting up● Operating

Higashidori Nuclear Power Station(Tohoku Electric Power Co., Inc.)

Unit 1■
Onagawa Nuclear Power Station(Tohoku Electric Power Co., Inc.)

Unit 1

Unit 2

Unit 3▲●●All cold shutdown
Fukushima Daiichi Nuclear Power Station(Tokyo Electric Power Co., Inc.)
Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 Unit 6

●

●

●

■

■

■

Accidents occurred at Units 1 to 4
Fukushima Daini Nuclear Power Station(Tokyo Electric Power Co., Inc.)

Unit 1

Unit 2

Unit 3

Unit 4●●●●All cold shutdown
Onagawa
Nuclear Power Station

By the following day (March 12) they had
somehow managed to obtain replacement electricmotors, power cable, a power supply truck, andmobile transformer. One electric motor was air-liftedfrom a Toshiba plant. Another was transported bytruck from the Kashiwazaki-Kariwa Nuclear Power
Station (TEPCO) in Niigata Prefecture.
Power generation staff inspected the component
cooling water system (CCWS) pump, which is part of
the residual heat removal system, and replaced its
electric motor.
It then took only a day to hook up a cable fromthe power panel in the waste processing building,which had survived the disaster. Most of thetemporary cable, with a total length of 9 km, wascarried on the shoulders and backs of approximately
200 workers, all cooperating to deploy the cable.
Thanks to their effort, the residual heat removal
system pump was started up. By the morning of the
15th, cold shutdown of all units had been confirmed.

accordingly less severe than at Daiichi. Even so, thetsunami came in with considerable force toward themountain side, causing water to flow into thebuildings.
As a result, the emergency power for Unit 1 wasflooded. All the seawater pumps were also knocked
out, with the exception of Unit 3.
“Because Unit 3 had survived, 500 people put inan exhaustive effort to restore power, such as byreplacing the motor and cable.”
Naohiro Masuda, the Fukushima Daini Site
Superintendent, conveyed his vivid recollections of
the situation that day.

Tokai No. 2 Power Station(The Japan Atomic Power Company)●

Late on the night of March 11, while the tsunami
warning was continuing the staff at the Fukushima
Daini Power Station walked inside the facilities toconfirm the extent of damage to equipment. With
many of the instruments having suffered damage
from the water, they worked at a fever pitch inattempting to restore the residual heat removal
system (RHR).

Cold shutdown

Fig.2 Outline of the Accident at the Fukushima Daiichi Nuclear Power Station

Fukushima Daini, where 200 persons hooked up
cables totaling 9 kilometers in length
What was the reason for the very different fates ofFukushima Daiichi and the other power plants?
At the time of the earthquake, Units 5 and 6 of
Fukushima Daiichi were undergoing regularinspection. Units 1 to 4 of Daini were all in
operation.
Comparing tsunami wave heights, at Daiichi Units
1 to 4 they varied from 11.5 to 15.5 meters. At Units
5 and 6 the waves were 13 to 14.5 meters high.
Whereas Units 1 to 4 are situated at a height of 10
meters, Units 5 and 6 are at 13 meters.
For this reason, Units 1 to 4 lost their external
power supply, followed by loss of the emergency
diesel generators and power panel functioning

5

as well as DC power supply due to the tsunami, on
top of that, loss of heat removal functioning by
seawater pumps (Fig. 2).
One of the emergency diesel generators for Unit
6, on the other hand, was still “alive” and managed
somehow to be started up. Fortunately it was possible
to connect this power also to the adjacent Unit 5,
enabling a heat removal route to be obtained bymeans of this temporary power supply and seawaterpump.
Meanwhile, there was Fukushima Daini located
10 km from Daiichi. The inundation height here
was around 7 meters and the site is located at a heightof 12 meters. The effects of the tsunami were

Reactor building
Spent fuel poolPrimary containment vessel
Reactorpressure
vesselCooldown
Cool the temperature of
the reactor water andspent fuel pool water tomaintain a low temperature.

Containment
Prevent radioactive materials
from being released
outside the reactor building
by ﬁve-layer wall.

Fuel

Heat
exchanger

Control rods

Suppression
pool

Shutdown
Shut down the reactor byinserting all control rods toprevent neutrons from causing
nuclear ﬁssion.

Residual heat removal system pump

A hydrogen explosion
blew off the top side of
the reactor building anddamaged the fuel rods,
resulting in a partial lossof the containment function.
Seawater pump
Ocean

Loss of power to the pumps used to circulate water
to cool the reactor coolant resulted in the loss ofthe cooling function.

6

Fig. 4 Overview of Onagawa Nuclear Power Station

At the time I visited in July 2012, while clear
traces of the tsunami were still visible here and there,
the recovery work was proceeding steadily.
I was able to spend time walking throughout theplant, and was permitted to visit every nook andcorner, including the reactor containment vessel. The
impression I got was of calm, quiet and orderly
procedures taking place, much like a regularinspection.
According to Site Superintendent Masuda, “Theequipment vital to safety was not damaged by theearthquake. The plant is stabilized, so we carry out
repeated training in maintenance and security,
making sure our workers master a wide range oftechniques.”
The power supply trucks, fire trucks and heavyequipment needed in an emergency are kept on highground, and each day is filled with training inconnecting power cables, operating heavy equipment,
supplying water and so on.
I also learned that the maintenance workers aremaking efforts to obtain qualifications, including alicense to operate heavy equipment, so that they will
be capable of making an emergency response on theirown if that becomes necessary.
The policy is to have front-line workers build up
the capability to handle any kind of situation, andbelieving in that capability, to entrust things to them.
The “keys to success” that I observed at Fukushima
Daini were confirmed for me even further at
Onagawa.
Higashidori
Nuclear Power Station

MaintenanceCenterPR Center

Achievement of Stopping,
Cooling, and Containing
The Onagawa Nuclear Power Station is located at
the center of the Oshika Peninsula at the southern tipof the Sanriku Coast, in Onagawa-cho, Oshika-gun
and Ishinomaki City, Miyagi Prefecture. The distancefrom the earthquake epicenter is approximately 123
km, which is closer than Fukushima Daiichi.
Peak ground acceleration of 567.5 Gal, an
unprecedented level, was measured in the second
basement floor of the Onagawa Unit 1 reactor
building. This was greater than the 550 Gal recorded
at Unit 2 of Fukushima Daiichi (Fig. 3).
The maximum tsunami height at both Fukushima
Daiichi and Onagawa was around 13 meters.

Fig. 3 Scale of earthquake and tsunami at
Onagawa Nuclear Power Station
and Fukushima Daiichi Nuclear Power Station

Tohoku Electric Power Co., Inc.
Peak
ground acceleration（Gal）
Onagawa
NuclearPower Station★
Sendai City

Epicenter×

Fukushima
DaiichiNuclearPower Station

567(Unit 1)

550*

(Unit 2)

Maximumtsunami height（m）13(measured value)

13*(estimated value)* Fukushima Nuclear Accidents Investigation Report(Tokyo Electric Power Co., Inc., June 20, 2012)

Fukushima Daiichi Nuclear Power Station

Unit 1

Administrationbuilding (old)

Gymnasium

Unit 2Current administrationbuilding

Unit 3

Under construction attime of quake

Facilities overview
Unit 1

Unit 2

Unit 3

Rated electrical
output524 MW

825 MW

825 MW

Date of commercial
operation startJune 1984

July 1995

January 2002

Reactor type

Onagawa Units 1 to 3 are BWR (Boiling Water
Reactors), the same as at the Fukushima plants.
Unit 1 (524 MW) started commercial operation inJune 1984. Unit 2 (825 MW) went into operation in
July 1995 and Unit 3 (same output) in January 2002
(Fig. 4).
At the time the quake hit, Units 1 and 3 wereoperating normally at full output. The reactor of Unit
2 had just begun its startup procedure at 14:00.
When the heavy shaking from the earthquake
was detected, all three units went into automatic
shutdown mode as they were designed to. Thenthe emergency diesel generators (DG) wereautomatically started. Next the reactor core isolation
cooling system (RCIC) in Units 1 and 3 wasmanually started.
At 15:29, 43 minutes after the quake, the largest
tsunami wave arrived. Seawater flowed into abuilding attached to the Unit 2 reactor building as aresult, shutting down the reactor component coolingwater system train B and the high-pressure core spraycomponent cooling water system.

Boiling Water Reactor (BWR)

Toppled heavy oil storage tank(Stored amount when toppled: approx. 600kl)(TEPCO)

78

Fortunately, train A was unaffected; moreover,power could be shared between each of the units.
Reactor cooling by pump was therefore started for allunits.
In just over 10 hours, the reactor temperature at
all units dropped below 100°C, achieving cold
shutdown.
The exhaust pipe monitors and radiation monitors
in each zone showed no abnormal readings.
The three steps of Stopping, Cooling, andContaining had safely been completed (Fig. 5).

The main damage from the earthquake was firedamage to the non-safety related High Voltage Metal
Clad Switchgear (A), housed inside the power
panel of Unit 1. There were no problems with thenon-safety High Voltage Metal Clad Switchgear (B)and emergency power supplies.
The main damage from the tsunami was floodingof buildings adjacent to the Unit 2 reactor building
and toppling of a heavy oil storage tank near thebay. None of this damage had any effect on cold
shutdown of the reactors.

Fig. 5 Plant status after earthquake struck (main timelines of Units 1 to 3)
Unit 1(operating at rated thermal output)

Unit 2(beginning startup sequence
after 11th regular inspection)

Unit 3(operating at rated thermal output)◆ March 11 (Fri.)
14:46 Reactor automaticallyshut down
Main turbine automaticallyshut down
14:47 Emergency diesel generators (DG)
(A) (B) automatically started◆ March 11 (Fri.)
14:46 Reactor automaticallyshut down*◆ March 11 (Fri.)
14:46 Reactor automaticallyshut down

14:47 DG (A) (B) (H) automaticallystarted14:49 Cold shutdown conﬁrmed

14:47 Main turbine automaticallyshut down

14:57 Fire alarm announcement
14:59 Reactor core isolation coolingsystem (RCIC) manually started
15:05 Reactor sub-criticality conﬁrmed

15:29◆ March 12 (Sat.)
0:58
Cold shutdown conﬁrmed

The biggest difference that emerges between
Onagawa and Fukushima Daiichi is the safety margin
for earthquakes and tsunamis. From the hard(equipment) standpoint, first of all, I would like tonote the following three points.
The first is that a power supply could be obtained
immediately following the earthquake and also after
the tsunami arrived (Fig. 6).
At Fukushima Daiichi Units 1 to 4, external
power supplies were lost, and emergency power
supplies were also all stopped due to the tsunami. By
contrast, Onagawa still had one of five external
power lines connected to the power station, and wasable to use six of the eight emergency diesel
generators. It was also possible to share theemergency generators among all units.

The second is the height of the site (Fig. 7).
The maximum tsunami height initially assumed
at both Fukushima Daiichi and Onagawa was around3 meters. Fukushima Daiichi was therefore built at aheight of around 10 meters, whereas Onagawa wasbuilt at a height of approximately 14.8 meters.
As noted earlier, the maximum tsunami heighton March 11 was around 13 meters at both locations.
Thanks to this extra margin at Onagawa, even though
the whole peninsula dropped one meter lower due toland subsidence in the quake, the facility wasprotected by the 13.8 meter height of its location andit was not washed over by the tsunami.

Fig. 7 Tsunami situation

15:26 RCIC manually started

Highest tsunami wave arrived
15:35

22:55 Fire declared to be extinguished
23:46 Reactor cooling begun by meansof residual heat removal system(RHR) pump (A)

14:57 Reactor sub-criticality
conﬁrmed

The many layers of readiness at Onagawa

15:42

DG (B) automatically
stopped (because CCWS
stopped due to ﬂooding
from tsunami)
DG (H) automatically
stopped (because CCWS
stopped due to ﬂooding
from tsunami)◆ March 12 (Sat.)
12:12

Reactor cooling begun bymeans of RHR pump (A)* Reactor was sub-critical because
startup had just begun (at room
temperature and normal pressure)

Building attached toUnit 2 reactor building(ﬂooded by seawater)
Unit 1heavy oil storage tank(toppled)

23:51 Reactor cooling begun bymeans of RHR pump (A)Site height: 13.8m(14.8m prior to earthquake)◆ March 12 (Sat.)
1:17

Cold shutdown conﬁrmed

Fig. 6 Securing of power supply immediately following earthquake
1. Emergency power supply
was secured

Emergency diesel generators (DG) were all normal (in standby mode)*

2. External power supply
was also secured(1) Matsushima main lines (275 kV): 1 line normal, 1 line stopped (restored Mar. 17, 2011)(2) Oshika main lines (275 kV): 2 lines stopped (restored Mar. 12, 2011)(3) Tsukahama branch line (66 kV) : 1 line stopped (restored Mar. 26, 2011)

Bay height: 2.5m
(3.5m prior to earthquake)

Tsunami height: approx. 13m
Time of highest tsunami wave arrival: 15:29(43 minutes after quake occurred)*The Unit 2 train B DG and train H DG (high-pressure core spray) became unavailable due to tsunami ﬂooding.
(The train A DG was available and power interconnection between all units was possible.)

910

When I visited the Onagawa Nuclear Power
Station one year after the disaster, Toshiaki Yashima,
Chairman Emeritus of Tohoku Electric who had been
involved in the plant even before it was built,
repeatedly expressed deep appreciation for the“predecessors.”
According to Mr. Yashima, Tohoku Electric
formed an internal committee of experts to study pasttsunamis around 1968. They decided to locate theplant at a height of 14.8 meters, citing historicalevidence of large tsunamis in the past, including
the Sanriku tsunamis of 1896 (Great Meiji Tsunami)
and 1933 (Showa Sanriku Tsunami) as well as
the Jogan Tsunami of 869 and Keicho Sanriku
Tsunami of 1611.
Then in 1987 when applying for approval to build
Unit 2, the estimated tsunami height was revised
upward to approximately 9 meters after studying theeffects of the Jogan Tsunami (geological survey). On
this basis it was decided to perform additional
reinforcement on the flood wall to protect theembankment with concrete blocks, up to a height of
9.7 meters from the base (Fig. 8).

In addition the seawater pump room in each Unit
had been built in a pit surrounded by walls at thetime of construction, and work had been carried out
since then to deepen the intake channel for obtaining
emergency cooling seawater during low tide.
Thanks to these various countermeasures carriedout over time, the facility “withstood not only the
first tsunami wave but the following waves as well.”Third was the seismic margin.
By June 2010, work had been completed for
upgrading the earthquake safety at Onagawa,including the addition of supports for equipment andpipes. This was done at a total of around 6,600 places
for the three units.
The towers supporting the exhaust ducts were also
reinforced with steel, and the towers and ducts wereconnected by seismic dampers, in order to increase
the seismic margin further.

Fig. 8 Strengthening of ﬂood wall (embankment protection)
Embankment protection by concrete blocks
was preformed up to a height of 9.7m
(additional work)

When Unit 2 was built,
assumed tsunami level estimated to be 9.1m
■ Matters accounted for in design- Stability at the time of tsunami drawback- Seismic resistance
O．P．
9．7m*
Embankment protection
5
O．P．
3．5m*
1．0m
2．1m

15

Pipe with support added

These extra layers of readiness proved their worth
at the time of the disaster. As I will talk about later
below, not only did the old administration building
serve as an emergency response room, but it also
provided temporary shelter for residents fleeing thedisaster in the nearby communities, as the seismic
upgrades were of great benefit.

Site ground

Embankment
protection*Indicates height before earthquake

Tsunami observation records

10Max. level approx. 13m

Withstood not only
ﬁrst tsunami wave
but the following waves as well

5
Level
0
(O.P.m)−5−10

Based on what was learned from the Niigata
Chuetsu-oki earthquake of 2007, major seismic
reinforcement by means of braces had also been
completed by 2010 in the administration building,including the emergency response room andcomputer room.
The new administration building currently in use
with its seismic isolation structure had been underconstruction since 2009, but seismic reinforcement of
the old building in use at the time of the earthquake
was carried out at the same time.

Support added

O．P．
14．8m*

3m
0．

1．
1：

Seawater pump room pit

Lower limit of tide gauge observation range

−15

14：30

15：00

15：30

16：00

16：30

17：00

Time

Recorded by backup tide gauge installed March 29, 2010

O.P. : Onagawa Peil, the Onagawa NPS datum plane
for construction,-0.74m below standard mean sea level of Tokyo Bay (T.P.)

Old administration building that had been reinforced with braces for improved seismic resistance11

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A sterling example winning worldwide praise
In July 2012, around the same time as my visit to
the Onagawa Nuclear Power Station, the plant was
visited also by a mission of 20 international experts,
led by Sujit Kumar Samaddar, Head of theInternational Seismic Safety Centre of the IAEA
(International Atomic Energy Agency), and including
regulatory agency staff from the French IRSN(Institute for Radiological Protection and Nuclear
Safety) and U.S. NRC (Nuclear Regulatory
Commission) as well as civilian experts. Their
purpose was to share data from Onagawa with IAEA
member countries.
After spending 11 days walking throughout thefacility and conducting thoroughgoing investigations,the mission members were surprised to discover“no significant damage” that would affect structural
performance.

The report states that “Despite prolonged groundshaking and a significant level of seismic energy
input to NPS facilities the structures, systems andcomponents of the Onagawa NPS performed its
intended functions without any significant damage.
The lack of any serious damage to all classes ofseismically designed facilities attests to therobustness of these facilities under severe seismic
ground shaking. It was concluded that the facilities of
the Onagawa NPS remain “remarkably undamaged”
given the magnitude, distance and duration of groundshaking. ”
When I returned to the Onagawa Nuclear Power
Station once again in October 2013, I heard anotherpiece of good news.
WANO (the World Association of Nuclear
Operators) had decided to present a Nuclear
Excellence Award to Tohoku Electric Senior
Executive Officer Takao Watanabe (currently
Managing Director and General Manager of the
Nuclear Power Department), who at the time of theearthquake was Superintendent of the Onagawa
Nuclear Power Station. The award was for promotionof excellence in the safe operation of commercial
nuclear power.
WANO cited the following three reasons for theaward.
1. For his superb leadership in preparing the
Onagawa nuclear plant and staff to be ready for
emergencies.
2. For his inspirational leadership enabling thesafe shutdown of three reactors during the largest
earthquake and tsunami encountered by any nuclear
plant in the world.
3. For providing for the safety of many residentsof the local community following the earthquake andtsunami.

Members whose combined efforts earned them a WANO Nuclear Excellence Award

What impressed me in particular about this award
was that it acknowledged the “people” (soft) aspectof the successful outcome. In any case, the actions
could not have been accomplished without thetireless efforts of the Superintendent and entire staff.
Attending the awards ceremony in Moscow, Mr.
Watanabe said that what made him happy more thananything was being told by the WANO Chairman,“This award is for you and for your staff.”“Then when I was leaving the ceremony, one of
the attendees, whom I had never met, said to me, ‘We
are very proud of you.’ It was an emotional momentfor me.”WANO awards ceremony in Moscow
Photo: The Electric Daily News (The Denki Shimbun)

IAEA mission to Onagawa Nuclear Power Station to examine
the performance of systems, structures and components following
the Great East Japan Earthquake and Tsunami

1314

How did the plant staff
respond at the time?
Just what kinds of feats, recognized also by
nuclear plant operators around the world, did the
Onagawa NPS staff pull off?
How did each of the people on the scene go into
action?
I will try to piece together the story, based ontalking with then Superintendent Watanabe, thepeople working in the plant at the time, and people
from the nearby community. (The positions of people
mentioned are as of that time.)
March 11, 2011. At the Onagawa Nuclear Power
Station, Units 1 and 3 continued to generate powerstably.
Unit 2 was at the end of a regular inspection, andKazuo Sakuma, Shift Supervisor and head of TeamA, responsible for Units 1 and 2, had been busy sincemorning making final checks for restarting thereactor.
Team A consisted of 12 members working under
Mr. Sakuma. That morning, following a day off, thedaytime shift started from 8:40 in the main control
room.
14:00. Right on schedule, they began pulling
control rods from Unit 2 and the startup process wasproceeding normally.
“We’ll be able to start generating power shortly.”
Along with a feeling of accomplishment after
completing the regular inspection process, there wasan air of excitement as the reactor was being put backinto service.
14:46. Before long the reactor would reachcriticality.
“Things are looking pretty good.”
Mr. Sakuma sat down in his chair with a sense ofrelief. Right at that moment he could hear and feelthe shaking. Then the main control room began
swaying violently.

15

He instinctively stood up and moved to the centerof the room, where he hung on to a pillar, whilelooking at the display panel to check the plant status.
The operators held onto hand rails on the control
panel and likewise carefully watched the display.
The generator output meter could be seen
dropping rapidly, from 100% to 0%. They knew theUnit 1 reactor had shut down automatically.
Meanwhile, in his office on the second floor of
the administration building, Superintendent Takao
Watanabe, who was waiting for notification that Unit
2 had reached criticality, felt the sudden shaking andducked under his desk.
Looking at the generator output meters in the
Superintendent’s office, he could see them dropping
rapidly for Units 1 and 3. Struggling to stand as theroom continued to sway, he shouted to the others,“Units 1 and 3 have stopped! We need to hold an
emergency session!”
Before long dozens of people, including theSuperintendent, Deputy Superintendent, andsupervisors/section managers, had assembled in theemergency response room on the third floor of theadministration building.
“The first thing we need to do is gather accurate
information and communicate it!”
Mr. Watanabe set up contact lines for eachreactor unit so that the plant situation could be
conveyed from the main control room of each unit to
the emergency response room. While gathering
information and trying to determine the situation, hekept the Head Office, located in Sendai City,
informed about the plant status.

Managing Director Takao Watanabe, who wasSuperintendent of the Onagawa Nuclear Power Station
at the time of the Great East Japan Earthquake

Talking with Managing Director Watanabe about the situation and responseat the plant when the Great East Japan Earthquake struck,
while looking at pictures from that time

Narrowing down of contact routes and concentratingon the situation at hand“The Head Office played the role of exchanging
information outside the company, so we were able toconcentrate on the situation facing us,” said Mr.
Watanabe, as he recalled the situation on that day.
“For contacts we used double routes. There were
two routes between the emergency response roomand the main control rooms of Units 1 and 2, where
they were faced with the serious situations of apower panel fire and inflow of seawater into thebuilding. One was a route between the Shift
Supervisor and the Engineering Supervisor in theemergency response room, and the other route was
between me and the Deputy Superintendent on
the scene.
Similarly, for keeping the Head Office informed,
the Engineering Supervisor of the plant contacted asection manager in the Head Office Nuclear Power
Department. To supplement this, we also set up thesecond route between me and the General Managerof the Nuclear Power Department. Because he used
to be the Superintendent of a nuclear power plant, he
had a good handle on the information.”“Just doing video conferencing all day would be
like doing a play-by-play of a fire scene. It’s
definitely not a good thing. During that time the fire
will keep spreading.”
When the plant decided to take in local residents
who were fleeing from the disaster, for example, theconversation with the Head Office was typicallyshort and to the point.
“We’re going to offer shelter to evacuees.”“OK, how many?”“We’ll let you know when we figure that out.”
Keeping reports to the necessary minimum, they
devoted their attention to dealing with the situation at
the plant. Assignment of personnel was left up to theSuperintendent, who could make decisions and act onthem immediately. The Head Office had people who
were well familiar with the plant, and they devoted
their efforts to providing logistical support.
Their trust of the people on the scene paved theway to a successful outcome.

16

Talking with Superintendent Shun Tsubata,
Assistant Staff Manager Kazuo Sakuma,
and Assistant Manager Yasuhiro Utsumi about the situation
and response at the plant at the time of
the Great East Japan Earthquake

Ten persons donned fire suits and went to scene of fire
14:49. Cold shutdown of Unit 2, which had juststarted up moments earlier, was confirmed. The
operators in the main control rooms, while
continuing to be rocked by aftershocks, carried out
operations toward cold shutdown of the remaining
Units 1 and 3, with no time to sit down.
They were well prepared for such a situation,
having conducted regular drills premised on various
accidents and disasters, using a simulator identical toan actual main control room. Therefore Mr. Sakuma
was confident they would be able to take the reactors
safely to cold shutdown.
Even so, the shaking this time was unlike
anything they had experienced. And then there were
the reports of a huge tsunami approaching. No doubt
they were fighting to maintain their composure. By
then the floor was scattered with debris from ceiling
panels and fluorescent lights that had fallen, whichcrashed and cracked under the feet of the workers. As
they endeavored to recall their training, they kept on
encouraging each other.

17

Meanwhile, fire alarms had been sounding since
right after the quake.
Workers heading to the scene reported thick blacksmoke rising.
Yasuhiro Utsumi, Specialty Leader for Turbine
Facilities in the Mechanical Maintenance Section,
was in the administration building when he felt theinitial shaking. When he learned of a tsunami
warning and evacuation order, he headed on foot to
the gymnasium parking lot.
“Take refuge! Everyone evacuate!”
Learning of the Superintendent’s instructions, theplant staff assembled in the parking lot. At the sametime, said Mr. Utsumi, “We also had heard about a fire
breaking out, and were ready to go out and fight it.”
“We need ten people from Turbine Facilities to go
to the scene of the fire.”
When that instruction went out, Mr. Utsumi, who
was familiar with the location, was first to decide.
When he asked, “Who else is going?” nine people
quickly raised their hands at the same time.
“Wow, these people are all volunteering?”
He was moved almost to tears. As they put on
their fire suits in the gymnasium, Mr. Utsumi was
racking his brain, trying to decide the best route forfinding their way to the fire while keeping them all
safe.

Assistant Staff Manager Kazuo Sakuma(Shift Supervisor at the time)

All they knew was that the fire was in the Unit 1
turbine building; they did not know what was
burning or the exact location. Entering the turbine
building, they first gathered up any fire extinguishers
they happened upon. Hoping to use the stairway
nearest to the fire, they opened the door, but wereimmediately engulfed in thick black smoke,
obscuring their vision.
“We can’t go down this way.”
While keeping in touch with the Mechanical
Maintenance Manager by phones, they tried to findanother route they could use.
Mr. Utsumi and the deputy leader of thefire-fighter group strapped on oxygen masks, andwalked carefully a step at a time inside the stairwell,darkened from the billowing smoke.
“If it’s burning, we ought to see flames,” hethought. But no flames were to be seen anywhere.
Inside the high-voltage power panel, sparks from a
breaker had melted cable insulation. That was thecause of the smoke.
Since their oxygen supply was nearly exhausted,
they returned for the time being. Just in the nick oftime. The moment they returned to the stairs andopened the door, an alarm started beeping. Only asmall amount of oxygen remained.
After repeated trips back and forth, they were
finally able to put out the fire using a dry chemicalfire extinguisher. By that time it was 22:55.

Yasuhiro Utsumi,
Assistant Manager of Turbine Facilities
in the Maintenance Department(Specialty Leader at the time)“We preparedextra sandbags just in case”
While the fire alarm was echoing in their ears,
they learned that a building attached to the Unit 2
reactor building was becoming flooded.
The Unit 2 reactor, as noted above, had stopped
during its startup process and cold shutdown had
been confirmed a few minutes later. Right after theearthquake struck, three emergency diesel generators
had started up and were ready to supply electricity at
any time.
At 15:29, the largest tsunami wave arrived. Thiswas followed by the successive stoppage of twodiesel generators, at 15:35 and 15:42. Alarms
sounded in the main control room.
An operator immediately ran to the scene, andreported that “Water is filling up the component
cooling water heat exchanger room in the thirdbasement floor of the reactor building! ”
Where was the water coming from? That was still
unclear. Superintendent Watanabe asked theRadiation Safety Section to analyze the water.

18

Onagawa town center← To Ishinomaki

Once it was clear that it was seawater, 25 people
from Reactor Facilities in the Mechanical
Maintenance Section, using eight emergency pumps,
began pumping out the water. They could not pump
it to ground level from the third basement level all at
once. Some quick-thinking worker found a large
plastic container.
They put the container on a landing in thestairwell, pumped water into it, and then pumped thatwater up to a higher level. Since the elevator was
stopped, they had to carry equipment up and down
the stairs. Mustering all hands available, they
continued this bucket brigade process through thenight.
Of the three emergency generators, the one thatwas working had to be protected by all means.
“Just in case, prepare a hundred sandbags! ”
Upon receiving this instruction from Jiro Masuko,
Deputy Superintendent, everyone pitched in to carrysandbags down to the third basement level.
Hearing that more water might be coming, Mr.
Masuko asked for more sandbags. “We made someextra ones. How many are needed?”“How many did you make?”“We’ve made 300 so far.”Without waiting around to be told what to do
next, people given one instruction were taking actionin advance by thinking ahead. When it came topreparing and hauling sandbags, too, people would
take the initiative, announcing, “I will send somepeople from my group to help!”
Thinking ahead to how they could help out, theplant staff took advance action. Mr. Watanabe wasdeeply heartened to witness this level of cooperation.

19

Onagawa Oshika Prefectural Road
(Gobuura Highway)

Tsukahama/Koyadori(130/225)

Oshika Peninsula Park
Prefectural Road
(Cobalt Line)

Other districts (18)

Onagawa
Nuclear Power Station

Iigohama (66/90)

Yoriiso (0/350)
Sheltering in elementary school
Maeami (28/90)“Let’s all take refuge
at the power station!”
After the tsunami hit, contacts with the outside
world became more difficult; and some 1,500 persons,
including workers from partner firms, were strandedin the plant, unable to confirm the safety of theircolleagues or families.
Besides those 1,500 persons, on March 11 there
were 17 visitors who had come to tour Unit 2, mostly
university students from Sendai City.
When the earthquake hit, their tour had just ended
and they were returning to the security checkpoint.
“No matter what, we had to keep our guests safe.”
That was the first thing in the mind of Nobuo
Soekawa, Public Relations Manager at the Onagawa
plant PR Center, even as the Center swayed violently
in the quake.
After several attempts trying to contact by phones
the people from the Sendai Office and PR Center
who were showing the visitors around, he finally got
through and learned that they were safe, having taken
shelter in the administration building.
Before he had time to relish that news, two
exhausted-looking men with little more than theclothes on their back opened the glass door of the PR
Center. They were Masao Abe, head of the
Samenoura district of Ishinomaki City, located southof the Onagawa NPS, and one other person from the
district.
“Everything has been washed away. Help the
people in our district.”
While Mr. Soekawa had heard on the radio about
the tsunami warning, he was not aware of thesituation in the nearby communities. Seeing thedesperate state of his old friend Mr. Abe, he realized
how serious things were.

Ishinomaki-Ayukawa
Prefectural Road
(Omotehama Highway)

Samenoura (101/130)

Facilities sheltering
evacuees
PR Center
Administrationbuilding (old)
Gymnasium

Fig. 9 Sheltering of evacueesat the Onagawa Nuclear Power Station

On that day, Mr. Abe had been filling bags with
seaweed in a shed at his home along the coast. Whilehe had managed to escape to higher ground, his home
and all his belongings had been washed completely
into the ocean.
Only two homes were left in the Samenoura
district, the rest having been completely wiped out;
and the shelter on high ground was unusable. The
residents who had fled to high ground were huddled
together outdoors, quaking with fright.
“At this rate the older folks won’t make it throughthe night.”“What are we going to do?”“How about asking at the power station? Why
don’t you try the PR Center?”
Someone from the district had raised the idea ofgoing to the power station. District Representative
Abe and one other person hitchhiked as far as they
could until the road was cut off, then walked the restof the way until reaching the PR Center, at a heightof 120 meters.

Notation: As of March 14, 2011 (evacuees/total residents)
Places where roads were cut off right after
earthquake (There were many other such places)×

Mr. Soekawa quickly opened the large hall andspread out whatever sheets and blankets he could
find. It must have been past 16:00. Neither of themen was sure of the exact time, but darkness was
beginning to fall and they could feel it becoming
increasingly cold.
The number of those taking shelter eventually
grew to 50 persons. At the PR Center blankets, work
clothes, and disposable hand-warmers were
distributed; but there was no heat because the power
was out. Before long the darkness of night enveloped
the Center.
Superintendent Watanabe made the decision
to move the evacuees from the Center to theadministration building, making use of two buses that
normally carried workers at the plant. There werealso some local residents who evacuated directly tothe power plant.
The next morning (March 12), two buses weredispatched from the power plant to the Samenoura
district to pick up more people. Eventually the
number of Samenoura residents taking refuge at theplant reached 101 persons (Fig. 9).

20

“Why did we think to go to the power plant? We
just naturally felt this was one place that would besafe,” said Mr. Abe, who was now able to smile
calmly as he looked back at that time.
“We knew all about the power plant since before
it was built. And having built the weather
observation tower, we were aware of the actual plant
and radiation levels. The women in our community
had also toured inside the plant. At events andfestivals we often meet up with people of the plant,
and we knew that if something happened, the power
plant would be the one place able to stand strong.”

Talking with Public Relations Manager Nobuo Soekawa at the Onagawa NPS PR Center
about how local residents came to be shelteredat the plant after the Great East Japan Earthquake

The gymnasium of the Onagawa NPS
where local residents were given shelter
after the Great East Japan Earthquake“Just load it up with supplies!”“Can we put up some of the local residents at theplant?”
When he received a phone call from Mr.
Soekawa, Superintendent Watanabe had been
engaged in a frantic battle to deal with the floodingin the building attached to the reactor building,and putting out the fire.
Still, upon hearing, “There are people soaked tothe bone. They are cold and there’s no power. Whatdo you want us to do?” without a moment’s
hesitation he replied, “Let’s have them come to thepower station.”“There was nothing brave about that decision. We
were all victims of this disaster. They were familiar
faces, and anyone would have let them in under thosecircumstances. (During the time they were taking
shelter) they wondered if there was anything they
could do to help out, and there were offers, includingfrom the tour group, to do things like cleaning, forwhich we were grateful.”
Mr. Watanabe quietly spoke to me about how theresidents came to be sheltered at the plant.
Their acceptance required approval of the General
Affairs, Public Relations, and Security Sections; but
the eyes of these staff members also said, “Let’s takethem in.”

21

The power plant had around 4,500 emergency
meals in stock. With the roads being cut off, thenumber of employees and members of partner firms“confined” inside the power station grounds
exceeded 1,500 people. In other words, there was notenough to feed everyone three meals.
“For now, the only thing we can do is to try andget by on one meal a day.”March 11, evening. That was the assessment of
Keiichi Meguro, Assistant Manager of the General
Affairs Section. On top of that there were the local
residents.
“There’s no way we were going to deny food topeople who had lost their homes to the tsunami andwere soaking wet,” said Mr. Meguro.
Because of such sentiments, priority was given to
the sheltered residents when distributing emergency
food. Uniforms and winter clothing provided for theplant workers were also distributed to them.
“We need food, water, blankets, and oxygen tanks
right away,” said Mr. Watanabe, speaking to the
Head Office by video conference.
The next morning Executive Vice President Takeo
Umeda left for the plant in a helicopter loaded up
with supplies.

“No one has to come along with me. Just load it
up with supplies!” Vice President Umeda thendelivered the supplies himself.
On the return trip, the helicopter carried a
pregnant woman close to giving birth and a patient
requiring oxygen, accompanied by Akemi Kashiwaya
from the General Affairs Section, who had registerednurse qualification. The helicopter landed at theKasuminome Air Field of the Self-Defense Forces,from where they were rushed to a Sendai hospital byambulance. Ms. Kashiwaya accompanied them to thehospital before turning them over to the care offamily members.
The residents who had taken shelter were latertransferred to the gymnasium, as their number grewto 364 by March 14.
In late April, people from the Head Office brought
over rice balls and tea, and the evacuees were able towalk around enjoying the cherry blossoms on theplant grounds.
In the ocean, evacuation boats that had lost its
port set down anchor in the bay of the power station.
For a period of three months in all, up to June 6,
the power station continued to protect the local
populace.

Living under the same roof, the plant staff andlocal residents ate together and shared in the joys andtribulations of overcoming the disaster ordeal
together. Their bonds became even firmer andstronger than before.
“If the power plant had not taken us in on thatday, some people might have frozen to death inSamenoura,” said Mr. Abe as he recollected theexperience.
“We were not lacking when it came to food andclothing, and people in other shelters were envious
because of how good we had it. What made us thehappiest was that after moving to the gymnasium,
each of us was allowed to make a three-minute phonecall. Being unable to use their mobile phones, manyof the people didn’t know if their family members
were safe. We were really, truly grateful for thatthoughtfulness.”
Even when word of the accident at Fukushima
Daiichi reached the gymnasium, “I knew Onagawa
would be all right,” laughed Mr. Abe.
“It withstood an earthquake and tsunami thatpowerful, so we believe in the Onagawa NPS. Now
we’re just hoping it will be restarted soon and go
back to producing electricity.”22

If the plant were to become cut off from the outside
world, it was decided that the Vice President would
come from the Head Office, and a heliport was built.
“The image training was useful, but it would havebeen better to practice the real thing,” said Mr.
Watanabe. In listing other areas needing
improvement, he noted that this time there happened
to be construction workers on hand to operate theheavy equipment, but it would be better to enable
plant staff to do that.

“Our power station”
Mr. Soekawa and Mr. Abe, who was head of the Samenoura district of Ishinomaki City at the time

“Handle normal times with emergencies in mind so thatyou are able to handle emergencies like normal times”
For Onagawa, from the time the earthquake
struck, taking command was basically left up to thesite, with the Head Office and branches, etc. quickly
moving to provide logistical support. The decision towelcome nearby evacuees in the plant was also madeby then Superintendent Watanabe.
It would seem that this policy of giving priority
to the people on the front lines, who are rooted
in the local region, is what led to both the solid
preparedness on the hard (equipment) side and thesuccessful disaster response on the soft (people) side.
The staff at the Onagawa NPS were unanimous instating that “It was the regular training that reallymattered.”
In response to my question, “What was the key
to success?” the first thing Managing Director
Watanabe said at the Head Office was, “Because wewere ready.”“Of the five external power lines, only one could
be used. People have said it’s like having your headattached to your body by only one piece of skin,
but the next morning it had already been restored.

23

That’s how strong we had built the transmission
lines. Not only was the plant built on high ground,but the pumps were protected by a pit formation, theflood wall was reinforced and so on. It was these
double and triple precautions that paid off.”Training was also an essential aspect.
“They say, ‘Handle normal times with emergencies
in mind so that you are able to handle emergencies
like normal times.’’ You can draw up a basic scenario,
but you have to adapt flexibly to a changing situation.
Flipping through manuals does not build up thenecessary skills. The most important training is that by
operators for 'stopping.' On the simulator we create avariety of equipment malfunctions, earthquakes andother mishaps. Since an earthquake cannot be
replicated on the simulator, a few years back weembedded speakers in the floor. They emit a roaring
sound, raising the tension level. We conduct training
to see if the operators can perform well under suchconditions.”
This was the first time for a helicopter to land at
the power station, but Mr. Watanabe noted that they
had performed image training for such an event.

Making everyone aware of the importance of
training, including plant staff and members of partner
firms, is not an easy matter. To that end, what
Managing Director Watanabe stresses is “my plant”
awareness.
“As has been pointed out many times by many
people, the most basic awareness is that ‘We are theones who must maintain safety.’ It’s what has been
impressed upon us by our seniors, and our role is topass it along to others.”
Born in Minami-soma, Fukushima Prefecture,and having majored in electrical engineering at thegraduate school of Waseda University, ever since
entering Tohoku Electric Power, Mr. Watanabe has
walked the consistent path of a “technology guy.”
The Onagawa Nuclear Power Station was his firstassignment on the front lines of power generation.
“I worked in the three-part shift in the main
control room. I was also involved in building and test
operation of Units 2 and 3. Since I lived with myfamily in Onagawa, for our son Onagawa is his home
town. The awareness of ‘together with the local
community’ came naturally.”

Before becoming Superintendent at Onagawa in
2009, he had headed the Higashidori Nuclear Power
Station in Aomori. At that time he used “Wa Plant”
to refer to the “my plant” mentality. In the Tsugaru

dialect of Aomori, Wa means “We.” Japanese Wa
also refers to the “Ring” of the community and the“Harmony” of teamwork.
Then at Onagawa he would talk about building an“O-Ra-Ho power station.” Oraho in the local dialect
means “ourselves.”“O” stands also for otagai, appreciating eachother’s standpoint. “Ra” stands for rashisa, living up
to one’s own potential. And “Ho” stands for hokori,
the pride of a professional. He then turned these into
the slogan, “Aim to build an O-Ra-Ho (our) power
station.”At first he would try to convey his messages tothe staff at regular meetings, but when someone
suggested communicating more widely by means of a“wall newspaper” or the like, he decided to post a“Message from the Superintendent.”“Around twice a month, I would create thesemessages on the PC late at night. The messages wereposted near the entrance, where they could be seenby the people who wore helmets and boots. The
feeling I tried to convey was, ‘First of all, thank you
all for your hard work. There is still much to be done,
but I’m happy for the fact that we can makeelectricity here.”24Current Superintendent Shun Tsubata, whotransferred to Onagawa from Higashidori after thedisaster, spoke proudly of the organization, notingthat “The Onagawa members have a sense ofsolidarity from having overcome the disaster
together. They have the strength to make it through.”
Work has begun on raising the height of the flood
wall. When it was built in April 2012, it wasapproximately 3 meters high (around 17 meters
above sea level). This will be raised to approximately
15 meters, or around 29 meters above sea level. The
total length will also be increased, from the current
600 meters to around 800 meters (Fig.11).
Shun Tsubata, Superintendentof the Onagawa Nuclear Power Station

The steadfast diligence forseeing things throughto successful completion
Based on the knowledge and experience gained
from the disaster, initiatives are being carried out
currently at the nuclear power plants throughout
Japan to raise their safety levels even further(Fig.10).
At the Onagawa Nuclear Power Station, the floodwall is being made higher, the emergency power
supplies are being made more diverse, and work has
begun on mounting seismic isolation fittings ontransmission line support insulators. In addition,
severe accident measures and training are being
strengthened further.
What impressed me in particular is all thepractical training being carried out so that workers
will be able to cope with heavy snow, darkness ofnight, and other harsh conditions. This training isbased on the principle of giving priority to the people
on the front lines and geared to Onagawa’s specificsituation.

Fig. 10 Examples of Safety Assurance Measures implemented after the Fukushima Daiichi Accident
Short Term Measures (completed)

Mid & Long Term Measures (to be implemented in a few years)

Additional deployment of emergency
power source vehicles

Installation of coastal levee

Emergency
SafetyMeasures

sea
level

Interconnection of emergency diesel
generators between units
Unit 1DG“I want us to build up even further our strength to
make it through, drawing on our diverse experiences.
The construction work will take another two years,
but we will be taking this as a chance for humanresource development, piling on the training.”
The steps toward safety never come to an end.
That’s why the only thing we can do is to learn fromfailure and from success, continuing on with the
unflagging efforts toward reduction of danger
and greater safety. I see this as the wisdom of
humankind.
Paying close attention to detail, never taking
shortcuts, being honest and steadfast.

That is what the word madee is said to mean in
the Fukushima dialect. It aptly describes the kind of
approach that is the key to success, and that is anecessary part of all processes toward safety.

concrete
structure

power supply trucks

Measures forsecuring power
SourceInstallation of protection walls

groundBreakwater
wall (new)Protection wall(new)
Watertight doors (new)Inspection of transmission line towers and measures against
earthquake and tsunami

Unit 2

DG

DG

DG(Fig. 10)

Deployment of wheel loaders

Installation of the reactor building ventilationand hydrogen detectors (BWR)
HydrogenHydrogenSettlement ofprocedure manuals fordrilling work/preparationfor equipment andmaterials

SevereAccident
Measures

Installment ofhydrogen detector

Reactorcontainment
vesselReactorcore

Installment of
the reactor building
ventilation system

Reactorpressure
vesselReactor building

Fig. 11 Initiatives for further enhancement of safety

Basic structure (cross-section) of ﬂood wall (steel pipe vertical wall)
Site side

Ocean side
O.P. approx. 29m*
Steel pipe
(2.5m diameter)

Impermeable wall (prestressed concrete)

Approx. 15m highSite height
O.P. approx. 13.8m

O.P. approx. 17m
Current ﬂood wall: approx. 3m highConcretewaterprooﬁng
Groundimprovement*A height accounting for land subsidence (approx. 1m) of the power station site due to an offshore earthquake in the Tohoku region
O.P.: Onagawa Peil, the Onagawa NPS datum plane for construction, -0.74m below standard mean sea level of Tokyo Bay (T.P.)

With Superintendent Tsubata
on high ground 60m above sea level overlooking
the entire Onagawa Nuclear Power Station

25

26

High-voltage power panel in elevated power supply center.
Six power supply trucks, able to be connected by cable in an emergency,
were also deployed at this elevated site.

Practice starting large-capacity power supply equipment,
conducted as snow falls

Wako Tojima

Practice securing water source with backup water truck(portable pump). The water source (condensate storage tank) for
supplying water from a tank to a nuclear reactor or spent fuel pool isreplenished with coolant.

Science Journalist

Visiting Lecturer, School of Social and International
Studies, University of Tsukuba
Awards
Ministry of Foreign Affairs, Diplomacy Forum,
Foreign Minister’s Prize
The 7th Award for Excellent Endeavors from theSocial and Environment Division of the Atomic
Energy Society of Japan
CareerGraduated from the College of Comparative
Culture, University of Tsukuba (Japan-U.S.
relations) in 1985. While enrolled, studied
Practice hooking up power supply truck

Practice sending water with water truck (backup seawater pump).
If the regular seawater pumps cannot be used, the truck pumpis used to pump up seawater from the ocean and send it
on to the cooling system.

Operation training on simulator premisedon loss of all AC power supplies

American Politics at the University of Kansas
as part of the International Exchange Programof the Ministry of Education, Culture, Sports,
Science and Technology (MEXT).
After working as a science reporter for The
Yomiuri Shimbun, became a freelance writer
primarily on scientiﬁc topics, seeking to identify
relationships between science and society, witha focus on “life” in the areas of the environment,
energy, medicine, life sciences, as well as
science and technology.
Writings and Publications [in Japanese]
Jintai saisei ni idomu (Taking up the challengeof regenerating human body parts); Meii ga
kotaeru 55-sai karano kenkoryoku (Famous
doctors’ advices on healthy living after
55; Hoshasen riyo no kiso-chishiki (Basicsof radiation use); Shiin jiten (Encyclopediaof death causes); Yomigaeru shinzo(Regeneration of the heart); and many
more books.
Long-running column on “Shin Yojokun (Newprecepts for the preservation of health)” inWork proceeds on raising the ﬂood wall height at the Onagawa Nuclear Power Station

27

monthly Bungeishunju; numerous other articles.

282-8-13 Chuo, Aoba-ku, Sendai, Miyagi, 980-0021, Japan (10th ﬂoor of Daiwa Securities Sendai Building)
TEL +81-(0)22-267-0021
http://www.t-enecon.com

This pamphlet was printed
using eco-friendly paperand vegetable oil ink.
2014. 05