the 2011 great east japan earthquake, tsunami and nuclear disaster

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proceedings

The 2011 Great East Japan earthquake, tsunami and nuclear disaster

1 2

1 Akira Inokuma DEng Executive director, Japan Federation of Construction management Engineers Associations, Tokyo, Japan

2 Daisuke Nagayama DPhil Chief executive officer, orientia United Co., Ltd, Tokyo, Japan

The Great East Japan earthquake of 11 March 2011 was a tragedy of unprecedented scale, one of the largest natural

disasters experienced by a developed nation. The disaster began with the primary damage of the earthquake,

which further led to the devastating secondary damage of the tsunamis and culminated in the tertiary damage

of the fukushima I nuclear power plant. This last has become a source of concern not only to the people living in

the power plant’s vicinity, but elsewhere in Japan and around the world. This paper provides an overview of the

disasters, the ongoing recovery operations and a summary of the lessons learned.

Proceedings of the Institution of Civil Engineers Civil Engineering 166 November 2013 Issue CE4 Pages 170–177 http://dx.doi.org/10.1680/cien.13.00001 Paper 1300001

received 01/02/2013 Accepted 16/04/2013

Keywords: disaster engineering / management / nuclear power

ICE Publishing: All rights reserved

Civil Engineering Volume 166 Issue CE4

The 2011 Great East Japan earthquake, tsunami and nuclear disaster Inokuma and Nagayama

1. Introduction

Over 2 years have passed since the Great East Japan earthquake and tsunami ravaged the north-eastern regions of Japan. It was one of the most devastating catastrophes in the modern history of the country.

The authors of this paper are civil engineers but not experts in disaster prevention, seismology or nuclear engineering. Their purpose in writing this paper is not to provide the technical details of the events or the aftermath, but to provide a holistic perspective of the natural catastrophe, the events that followed and the key lessons learned to a wider international audience.

The paper starts by providing an overview and explains some of the distinguishing characteristics of the earthquake and tsunami, along with the status of the ongoing recovery and remedies. It goes on to explain the catastrophe at the Fukushima I nuclear power plant, with details about the radioactive contamination, evacuation and controlled blackouts. It concludes by summarising the lessons learned as presented by national commissions and independent experts.

2. The 2011 Great East Japan earthquake and tsunami

2.1 Earthquake and tsunamiAt 2.46 p.m. on 11 March 2011, the earth shook violently for

over 6 min. The earthquake, which would later be known as the Great East Japan earthquake, recorded a moment magnitude of 9·0. The epicentre was around 70 km off the coast of Japan’s Miyagi prefecture in the Pacific Ocean at a depth of 24 km. As shown in Figure 1, virtually the entire Japanese archipelago was affected by the subsequent tsunami waves.

Tidestation

Inundation height

Run-up height

Normal tide level

0.2 – 0.7 m0.7 – 2.5 m

>2.5 m

Epicentre120°E

987654321

Obs

erve

d in

unda

tion

hei

ght:

m

130°E

140°E

150°E20°N

30°N

40°N

figure 1. The march 2011 tsunami waves impacted most of Japan, with inundation heights up to 30 m and run-up heights reaching 43 m (after ministry of Land, Infrastructure, Transport and Tourism (2012))

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Civil Engineering Volume 166 Issue CE4 November 2013


The tsunami struck the entire eastern coast of Japan shortly after the earthquake. Within 3 min of the earthquake, the Meteorological Agency of Japan sent out emergency tsunami warnings, from Hokkaido in the north to the tip of Kyushu in the south as well as the Ogasawara Islands in the east (Japan Meteorlogical Agency, 2011). After the earthquake, the global positioning system swell meters located around 20 km off the coast of north-eastern Japan recorded rapid increases in the sea level, so the Meteorological Agency immediately expanded the emergency warning zones and announced higher-than-expected tsunami wave heights.

The agency continued the warnings until the warnings were finally dismissed at 5.58 p.m. on 13 March 2011. The waves encroached with an inundation height of 20–30 m, and in Miyako, Iwate prefecture, the run-up height was up to 43·3 m. People trying to flee in their cars had their escape routes cut off and were seen live on television news vanishing under the waves as entire cities were inundated.

2.2 DamageThe casualties of the Great East Japan earthquake are 15 882

people dead and over 2668 missing (National Police Agency, 2013), with a further 313 329 people evacuated from their homes (Reconstruction Agency, 2013).

A characteristic that distinguishes the Great East Japan earthquake from the country’s other two great earthquakes of the last century is the percentage of victims who died from drowning (Figure 2). While death by fire was the cause of 87% of deaths in the Great Kanto earthquake of 1923 and death by crushing (e.g. due to collapsed buildings) was the cause of 83% of deaths in the Great Hanshin earthquake of 1995, in the Great East Japan earthquake of 2011, 93% of deaths were caused by drowning in the tsunami waves.

The sheer power of the tsunami can be seen clearly from Figure 3, which shows the Taro district in Iwate prefecture before and after 11 March 2011. Taro had been repeatedly hit by tsunamis in its history and therefore had built two 10 m high breakwaters to protect the town. However, most of these were broken into pieces and others were overtopped. The dead and missing rate in this district was approximately 6% of the population.

The Great East Japan earthquake’s tsunami damages extended over the entire eastern coast of the Japanese archipelago, and therefore the damage caused to the infrastructure and the economy was of colossal

figure 3. Aerial views of Taro in the Iwate prefecture taken before and after the tsunami waves hit – most of the port’s 10 m high breakwaters were destroyed or overtopped, killing 6% of the population (from Tohoku Construction Association)

Great Kanto earthquake (1923) Great Hanshin earthquake (1995) Great East Japan earthquake (2011)

Death by drowning Death by fire Death by crushing Others/unknown

87.1%

12.8% 1.1%10.5%

83.3%

4.4%2.4% 3.9%

92.4%

0% 0% 2.1%

figure 2. Distribution of the causes of deaths in the three deadliest earthquakes since 1900 in Japan (based on data from the reconstruction Design Council (2011) in response to the Great East Japan earthquake)

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magnitude. As for housing, about 130 000 houses were completely destroyed and around 240 000 houses were seriously damaged (National Police Agency, 2013). As shown in Table 1, infrastructure and property damage were estimated at approximately 17 trillion yen (£118 billion).

2.3 ongoing recovery and reconstructionThe government’s reconstruction plan was designed to be

completed in 10 years. It was separated into two phases, with the first 5 years as a ‘concentrated reconstruction phase’. The second phase for the remaining reconstruction will be designed in more detail as the plans from the first 5 years are implemented and evaluated.

The measures to be taken in the reconstruction plan fall into three main categories. The first includes measures for the recovery and reconstruction of the disaster-stricken areas as well as the rehabilitation of residents’ daily lives. The second category includes measures in which the areas that were indirectly affected by the disaster, such as those to which evacuees have moved as well as areas to which the negative socio-economic effects have reached, are reconstructed and

revitalised. The third category involves measures that should be taken as a lesson from the Great East Japan earthquake and subsequent tsunami, such as disaster prevention, control and mitigation.

The budgetary size of the 5 year ‘concentrated reconstruction phase’ was estimated at approximately 19 trillion yen (£132 billion) by the Japanese government’s reconstruction headquarters and was later approved by parliament as the separate special-account spending on reconstruction from the Great East Japan earthquake. Around 13 trillion yen (£90 billion) of this budget would be secured by the first and second supplementary budgets of 2011, as well as other measures like spending cuts. The entire 10 year reconstruction plan was estimated at 23 trillion yen (£160 billion) (Reconstruction Agency, 2011), which does not include the costs that may accrue from the Atomic Energy Damage Compensation laws or the Act to establish the Nuclear Damage Compensation Facilitation Corporation (National Diet of Japan, 2011a).

In the immediate aftermath of the earthquake, much of the infrastructure in the coastal areas of the Tohoku region was damaged and unusable, but recovery of major infrastructure was conducted with surprising speed. For example, 347 km of the 675 km Tohoku Expressway had been damaged by the earthquake, but traffic restrictions were lifted on 24 March following completion of emergency restoration measures (Cabinet Office, 2012). By 20 November 2011, the vast majority of infrastructure had been rebuilt and restored, as shown in Figure 4.

While the recovery of infrastructure was prompt, the recovery of residential property has not proceeded with the same speed. On 19 November 2012, the national newspaper Yomiuri Shimbun reported that of the 23 930 publicly run ‘restoration housings’ that have been planned by municipalities in the disaster-stricken Iwate, Miyagi and Fukushima prefectures, construction had begun for just 848 houses, and land had only been acquired for 5204 houses (Yomiuri Shimbun, 2012).

According to the article, the delay is partly due to a lack of land and a shortage of municipal officials to handle the projects. According to a news report on 1 November 2012, one of the reasons why there is a lack of land is due to landowners’ unwillingness to sell the land or lease it for long periods of time (Iwate Nippo, 2012). Furthermore, the article points out that the underlying reason why landowners are not willing to sell or lease their land is due to the lower prices being offered by municipalities.

3. The Fukushima I nuclear power plant

3.1 AccidentAbout 41 min after the first shocks, the tsunami hit the Fukushima

I nuclear plant, which has six nuclear reactors (Figure 5). The days, weeks and months to follow came to be known as the Fukushima I nuclear disaster, culminating in a nuclear meltdown categorised as level 7 on the international nuclear event scale (IAEA, 2011). Soon after the accident, areas inside the 30 km radius from Fukushima I had been designated as evacuation zones, which were reviewed and narrowed in 2012.

The nuclear disaster first began with the earthquake at 2.46 p.m. on 11 March. Although reactors 1, 2 and 3 automatically reached scram status (i.e. emergency shutdown), the earthquake had damaged the power transmission and distribution facilities between the Fukushima transformer substation and the reactors, and the plant lost all external power.

A little under an hour later at 3.37 p.m., the peak of the tsunami

Recovered Not recovered

0% 20% 40% 60% 80% 100%

Port

Airport

Railway

Shinkansen

Roads

Expressway

Cellular phone lines

Communication lines

Postal delivery service

Post office operation

Bank service

Petrol stations operation

Water supply

Liquefied petroleum gas supply

Town gas supply

Electricity supply

32

0

3

0

1

0

2

1

20

11

16

15

2

5

14

4

68

100

97

100

99

100

98

99

80

89

84

85

98

95

86

96

figure 4. Status of infrastructure recovery at 30 November 2011 – much was rebuilt and restored within just a few weeks (Cabinet office)

Damage category Value: ¥ trillion Value: £ billion

Buildings (housing, offices, plants, machinery, etc.)

10·4 72·7

Services (water service, gas, electricity, communication and broadcasting facilities)

1·3 9·1

Infrastructure (road, harbours, drainage, airports, etc.)

2·2 15·4

others (agriculture, forestry, fisheries)

3·0 21·0

Total 16·9 118·2

Table 1. Estimated physical damage caused by the Great East Japan earthquake (based on data at 24 June 2011 from the Cabinet office of Japan)

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wave arrived, which flooded and totally destroyed diesel generators for emergency electric power (Figure 6), and the direct current power supply for reactors 1, 2 and 4, resulting in loss of all power – except for an external supply to reactor 6 (National Diet of Japan, 2012). It is estimated by the Fukushima Nuclear Accident Independent Investigation Commission (NAIIC) that by around 6.10 p.m., the reactor core had been partially exposed in reactor 1, and damage had begun by 6.50 p.m. Freshwater injection began at 5.46 a.m. on 12 March, and venting at approximately 2.30 p.m., but at 3.36 p.m. a hydrogen explosion had blown the top half of the building away. Reactor 3 followed the same fate and ultimately led to a hydrogen explosion at 11.01 a.m. on 14 March. Reactor 4 reached a hydrogen explosion at 6.00 a.m. on 15 March (Figure 7). Reactor 2 had leaked water containing radioactive material as a result of severe damage to the pressure suppression chamber, presumably breached by an explosion.

As of 17 November 2012, all six of the nuclear reactors at the Fukushima I plant have been shut down. Of the six reactors, it has been officially decided that 1, 2, 3 and 4 will be decommissioned. At the time of the earthquake and tsunami, reactors 5 and 6 had been in cold shutdown due to periodic inspection and are still in the same status (Tepco, 2012).

500 kV transm

ission

275 kV transm

ission

275 kV transm

ission

Reactor 6

Reactor 5

High voltage switching yard

High voltage switching yard

Anti-earthquake building

Emergency responsecentre

Administrationoffice

Intake channels

Northbreakwater

Eastbreakwater

Southbreakwater

Turbine buildings

Radiation waste treatment facility

Servicehall

Common poolbuildings

Reactor 1

Reactor 2

Reactor 3

Reactor 4

Cooling waterdischarge

Cooling waterdischarge

Turbine buildings

figure 5. Layout of the Fukushima I nuclear power plant, which is on the eastern shoreline facing the earthquake epicentre (after National Diet Commission (2011b))

figure 7. Aerial view of Fukushima I power plant on 16 march 2011 showing exploded reactor buildings 1, 3 and 4 (Digital Globe)

Turbine buildingNuclear reactor

Pressure suppression chamber

Maincontrol

room

Emergency dieselgenerator room

14 m: inundation level

10 m

4 m

Sea level

figure 6. Cross-section of the Fukushima I plant reactors showing the inundation level that destroyed the emergency generators, causing over-heating and explosions in reactors 1–4 (after National Diet Commission (2011b))

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3.2 radioactive contaminationThe crisis at Fukushima I brought about immediate, extensive

and sustained consequences to the surrounding areas. As can be seen in Figure 8, radioactive material spread as far north as Iwate prefecture and as far south as Tochigi and Ibaraki prefectures.

It is said that, due to the direction of the wind in March 2011, much of the radioactive material had been blown to the Pacific Ocean, but on days such as 15 March, which was the day on which the explosion happened in reactor 4, the winds blew in the opposite direction towards inland Japan (Mainichi Shimbun, 2012).

3.3 EvacuationResidents living within 30 km of Fukushima I were eventually

forced to evacuate from their homes due to the risks from radiation. On 11 March 2011, residents living within 3 km of the plant

were ordered to evacuate to outside areas, and residents who lived between 3 km and 10 km from the plant were ordered to remain indoors. On the morning of 12 March, residents within a 10 km radius of the plant were ordered to evacuate. Then, after the explosion of reactor 1 in the evening of 12 March, the evacuation area was expanded from a 10 km to a 20 km radius around the plant. Residents within a 10 km radius of the Fukushima II plant, around 11 km to the south, were ordered also to evacuate. After the 15

March explosion of Fukushima I reactor 4, the government ordered people within a 30 km radius of the plant to evacuate (Mainichi Shimbun, 2012).

On 22 April 2011, several areas outside the 20 km (30 km in some areas) radius of Fukushima I (e.g. parts of Katsurao village, Iidate village, Tamura city, Kawauchi village) became designated as the planned evacuation areas where people were asked to evacuate to, or emergency evacuation areas, where people could remain but schools were shut down. On the same day, the area within a 20 km radius of Fukushima I became designated as a vigilance area where people were not allowed to enter. As of January 2013, no casualties have been reported as being directly caused by the nuclear accident but, according to the government, even in December 2012 there were still about 321 000 evacuees.

3.4 Controlled blackoutsControlled blackouts were implemented in the Kanto region,

which is located south of Fukushima prefecture, as a countermeasure for uncontrolled electricity shortages. As reported by CNN on 31 March 2011, ‘the loss of two nuclear power plants meant that the Tokyo region would face the summer peak demand with a loss of about 20% of capacity’, and ‘other utilities can supply only a limited amount of additional electricity because Tokyo Electric runs power at a different frequency from the rest of the country’ (Ferguson, 2011).

Due to the risk of a massive uncontrolled blackout, controlled blackouts were implemented on 14 March in parts of Ibaraki, Shizuoka, Yamanashi and Chiba prefectures, and continued for 1 h 24 min. Controlled blackouts were further implemented after 15 March, and on 17 March the average electricity demand from 9.00 a.m. to 10.00 a.m. reached 33·3 GW, which was 99·4% of the supply capacity at that time.

Controlled blackouts were implemented in 14·4 million households in the region. The risk that demand would surpass supply was prevalent but, in hindsight, controlled blackouts were not necessary after 28 March, which Tokyo Electric Power Company (Tepco) later explained as being the result of increased supply through thermal power stations that had resumed operation.

3.5 DecontaminationThe government declared in January 2012 that in the fiscal years

of 2012 and 2013, the areas in which the annual radiation dose was recorded as 20–50 mSv should be gradually reduced to below 20 mSv, but decontamination progress has been lagging.

According to the Ministry of Environment (2012), special laws for countermeasures against environmental contamination by radioactive material released by the nuclear accident following the Great East Japan earthquake were announced at the end of August 2011 and fully implemented by 26 January 2012. With these laws, special decontamination areas were designated and, after hearings with the heads of local municipalities, the environment minister decided on a special area decontamination implementation plan. In parallel with the plan, investigations were implemented for the status of buildings, screening points and temporary waste-storage areas.

First, the decontamination model was decided upon, then preliminary decontamination was implemented, followed by actual decontamination, which utilised the experience and information gathered in the model and preliminary decontamination. The goal for the decontamination project was decided as follows.

Radiation level: kBq/m2

>30001000–3000600–1000300–600100–30060–10030–6010–30<10

The area wheremeasurement resultscould not be obtained

160 km

100 km

60 km

30 km

20 km

Fukushima Inuclear powerplant

km0 50

figure 8. results of radiation monitoring around Fukushima prefecture – unfortunately the wind changed from westerly to easterly on the day reactor 4 exploded, contaminating large areas inland (adapted from mEXT (2011))

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n Decrease the degree of contamination (annual radiation dose) for the general public by approximately 50% by the end of August 2013 in comparison to August 2011.

n Decrease the degree of contamination (annual radiation dose) for children by approximately 60% by the end of August 2013 in comparison to August 2011.

n The long-term goal was to decrease annual radiation dose to below 1 mSv per year as a result of the decontamination.

As of January 2013, decontamination is being implemented in only two municipalities, and plans have been devised in other regions.

3.6 Investigation committeesAs the emergency of the accident was slowly alleviated, the

Japanese public, opposition parties and civic organisations began to raise questions as to whether the Fukushima I nuclear disaster was entirely natural and inevitable, or could have been mitigated if the known risks had been properly countered.

In an effort to answer the questions, four nuclear accident investigation commissions were formed separately. The four commissions are commonly known as the Private Sector Commission, the Tokyo Electric Commission, the Diet Commission and the Government Commission.

Final reports were submitted by all four commissions by the end of July 2012. The characteristics of the reports differ due to the rationales for the commissions’ establishment.

4. Lessons

4.1 Earthquake and tsunamiThe 2011 Great East Japan earthquake has become a painful lesson

for the country of Japan, and has affected people’s emotions on an unprecedented scale, with knock-on effects throughout the world both in terms of disaster management and energy policy.

Precisely because it was such an emotional event that could occur almost anywhere in the world, it is of utmost importance to take lessons from the earthquake through an objective perspective. Many comments and opinions have been presented by a great many experts in various fields; the authors chose several lessons based on two criteria: applicability to future disasters and objectivity.

4.2 Emergency tsunami warningOne of the ways to minimise casualties caused by tsunamis is

to provide reliable, accurate information to residents in a timely manner. According to an article in Jiji News, delays in fleeing from the tsunami were caused, to some extent, by the first warnings underestimating the tsunami wave heights, (Jiji Tsushin, 2012).

The first tsunami warnings released 3 min after the earthquake were based on the estimation that the earthquake was 7·9 in magnitude, which was ultimately revised to 9·0. Thus, the first warning announced that the tsunami height would be 3 m, which was significantly lower than the actual waves. Residents aware of the maximum wave height their seawalls could withstand thus received a false sense of security.

The government Meteorological Agency uses the ‘Meteorological Agency magnitude’ as the scale showing how large an earthquake is. It is computable within about 3 min of an earthquake to provide the first round of tsunami warnings as quickly as possible. Yet there is a technological limitation to this method and, for large earthquakes of moment magnitude 8·0 or higher, an accurate assessment of the actual magnitude of the earthquake is very difficult.

The swell meters were able correctly to predict a tsunami height of over 10 m in Miyagi prefecture and 6 m in Fukushima prefecture, but the warning was received 28 min after the earthquake. The Meteorological Agency says that data from the underwater water-pressure gauge located further from the coast than the swell meters could not be fully reflected in the warnings.

There is a trade-off between the speed and accuracy of the warning, and thus utmost care should be taken to prevent underestimates. Thus, considering the results of the tsunami, the Meteorological Agency suggests that when providing the first tsunami warnings in the future, they should use qualitative terms such as ‘huge’ to describe the tsunami rather than to try to provide an estimated height.

4.3 Scope of civil engineering and education for securityThe role and scope of civil engineers is another crucial question

that arose from the tragedy. Civil engineering in the strict sense has been honed over the centuries to be able to cope with a wide array of structural requirements. Yet Toshitaka Katada, a professor at Gunma University, whose disaster-prevention education programme that taught students and parents led to a 99·8% survival rate of elementary and junior high students in Kamaishi city in the Iwate prefecture, argues that civil engineers should not focus solely on structures. They should incorporate other fields and expand their scope into areas that go beyond physical structures if necessary (JACIC, 2011).

Katada had been involved in disaster protection and hazard simulations for decades before the Great East Japan earthquake. In his past work, he interviewed residents whose houses were damaged by storms and heavy rain and asked them why they did not escape even when the rain had flooded their homes above floor level. The residents would express anger and criticise local authorities for not issuing evacuation notices, but Katada criticises such attitudes as a lack of a sense of independence, which ultimately leads to vulnerability in Japan’s disaster-prevention plans.

In the case of the Great East Japan earthquake, many of the deaths in Kamaishi city happened in the ‘safety zone’ rather than the ‘hazard zones’, which had been shown in the hazard map issued by local authorities. In other words, the people had become too dependent on the authorities and accustomed to waiting for orders. They believed what the hazard map forecast rather than making decisions based on what was actually happening. Katada further recommends that people should be educated to be able to make their own rational decisions rather than wait for orders or blindly trust hazard maps.

He concludes with the following recommendation: ‘Whether there is a tsunami warning or not, there is always the risk of a tsunami after a large earthquake, so one should always try to evacuate. If there was no tsunami despite the evacuation, one can just say ‘good, there was not a tsunami’. By continuing this, when one day a tsunami actually happens, one can say, ‘it was indeed good to have evacuated’’ (JACIC, 2011: p. 6).

4.4 ‘Tough’ breakwater Breakwaters are designed to calm waters within harbours and

reduce the effect of waves, so they can also provide protection from tsunamis. In the Great East Japan earthquake, it has been analysed that the breakwaters in Kamaishi Port delayed overtopping by approximately 6 min and decreased the wave height within the harbour by approximately 40% (Hosokawa et al., 2011).

However, in some cases the breakwaters slid and collapsed. It is assumed that the cause of the collapses are compound, with the

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wave power causing the sliding and overflow causing scouring of foundations, particularly on the landward side. Furthermore, the fast flow of water damages the concrete block protection of the embankments, such that the wave pressure finally causes the parapet walls to collapse. This was an unexpected phenomenon, and thus the new idea for a ‘tough’ breakwater has since been proposed.

The tough breakwaters are designed with three design concepts (Figure 9). The first is a more protected rear embankment foundation, the second is a stronger overall protective covering and the third relates to the parapet. The methods of construction are explained below.

n Rear foundation protection – decrease the rear embankment slope angle, provide a protective horiztonal slab over the rear toe and improve the soil around the toe.

n Stronger protective covering – increase protective material thickness over the front slope, crown and rear slope of the embankment and improve the connections between protective units.

n Parapet walls – avoid using parapet walls by raising the embankment to provide the required design height, or reinforce parapets with steel bars if they have to be used.

Figure 10 is an example of an actual application. In the case of the proposed tough seawall in southern Sendai Bay, the 20 km embankment will be covered by interlinked concrete blocks that are 2 t in weight and 0·5 m thick. The blocks are used on both the seaward side and landward side, and the seawall is designed to continue resisting a tsunami even if it is moved or inclined. The Ministry of Land, Infrastructure, Transport and Tourism says it is studying the new design.

4.5 Nuclear power stationLessons from the Fukushima I nuclear disaster have been examined

meticulously by the four commissions. Among the four commissions, the Diet Commission chaired by Kiyoshi Kurokawa, former chairman of the Science Council of Japan, is regarded as the most objective.

Concerning analysis of the accident, the Diet Commission describes the basic characteristics of the accident as, ‘the result of collusion between the government, the regulators and Tepco, and the lack of governance by said parties. They effectively betrayed the nation’s right to be safe from nuclear accidents. Therefore, we conclude that the accident was clearly ‘manmade.’ We believe that the root causes were the organisational and regulatory systems that supported faulty rationales for decisions and actions, rather than issues relating to the competency of any specific individual’ (National Diet of Japan, 2011b: p. 16).

With regard to the reasons why the accident has such characteristics, the Diet Commission says in its report (National Diet of Japan, 2011b: p. 27) that, ‘The structure of Fukushima [I] Unit 1 was incapable of withstanding the powerful earthquake and massive tsunami of 11 March 2011. The specifications for the plant lacked adequate anti-quake and anti-tsunami yield strengths because: 1) the guidelines for nuclear plant construction were insufficient at the time the construction permit was granted for Units 1 through 3 in the late 1960s’.

In 1981, a regulatory guide for reviewing seismic design of nuclear power reactor facilities was set by the Nuclear Safety Commission (NSC). In 2006, NSC released a revised version of the former guidelines (NSC, 2006). The Nuclear and Industrial Safety Agency (Nisa) acted to require that nuclear operators assess the anti-seismic safety of their sites according to the new guidelines – the so-called ‘anti-seismic back-check.’ In March 2008, Tepco submitted an interim anti-seismic back-check report on unit 5 of Fukushima I, stating the safety of its anti-seismic measures and assuming an increased safety tolerance level of the maximum seismic acceleration to 600 cm/s2.

4 m

3 m

+7.2 m

1:2 1:5

Seaward side Land sideInterconnected 2 t protection blocks

2 t protection blocksover foundation

Foundation

2-t protection blocks

figure 10. Cross-section of a new 20 km ‘tough’ breakwater at Sendai Bay – it is designed to continue resisting tsunami waves even when moved (after Government of Japan (2011) and Nikkei Construction (2013))

‘Tough’ Raise crown (no parapet)and increase protection

thicknessReduce rear slope,increase protectionthickness, protect toeand improve ground

Conventional

Seawardside

figure 9. Proposed improvements for breakwaters are based on the fact that many failed due to sliding, rear toe erosion and parapet wall collapse (after Government of Japan (2011))

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According to the Diet Commission’s investigation, Tepco learned through the interim report assessment process that many reinforcements were required to meet the standards of the new guidelines. However, no reinforcements had been made to units 1–3 at the time of the 11 March earthquake. ‘Although Nisa had recognized the need for the reinforcements and the backcheck, the regulator failed in its oversight of Tepco’s progress’ (National Diet of Japan, 2011b: p. 27).

Concerning the lessons of the accident, the Diet Commission reports the following seven recommendations

n monitoring of the nuclear regulatory body by the National Dietn reforming the crisis-management systemn government responsibility for public health and welfaren monitoring the operatorsn setting criteria for the new regulatory bodyn reforming laws related to nuclear energyn developing a system of independent investigation commissions

(National Diet of Japan 2011).

As for the question of whether the earthquake had indeed been one of the direct causes of this Fukushima I nuclear disaster, no conclusion has been reached because of the present state of danger at the nuclear power plant. It is an important point to verify in the future.

One point that the authors would like to suggest is the fact that the Fukushima II nuclear power plant – which began operation in 1982, is located approximately 11 km south of the Fukushima I plant and right by the coast, as is Fukushima I – did not reach a state of meltdown. The main reason for this is that, unlike Fukushima I, Fukushima II could secure the electricity source to be able to cool down the reactor. It was mainly due to a single cable between the plant and the external electricity supply.

There was also a difference in the location of the emergency diesel generators in the power plant. At the Fukushima I, the emergency generators are located in the turbine building, which is closer to the sea than the reactor building, whereas at Fukushima II the emergency generators are located inside the reactor building. At both power plants, water from the tsunami flowed into the turbine building but some of the diesel generators survived at Fukushima II, while no generators survived at Fukushima I plant. A lesson from this is that newly improved design methods should be applied to existing operational structures.

Whether the accident can truly be declared as ‘man-made’, as stated in the Diet Commission’s final report, is still an open question. But if lessons are not learned from what has happened in Fukushima and the same mistakes are repeated, there can be no defence against charges of negligence.

Acknowledgements

The authors would like to express their deepest condolences to the victims of the 2011 Great East Japan earthquake and to the friends and families of victims who still suffer from the tragic catastrophe. The authors would also like to express their deepest gratitude to all people from all countries that have extended their hearts to the people of Japan.

references

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Government of Japan (2011) Kaigan Teibou Nado no Nebariduyoi Kouzou Oyobi Taishin Taisaku ni Tuite. Government of Japan, Tokyo, Japan (in Japanese). See http://www.pref.iwate.jp/~hp0212/fukkou_net/pdf_doc/tsunamibousai_08_01_9.pdf (accessed 02/08/2013).

hosokawa S, miyata m, Aoki N and Kamouchi K (2011) Tsunami ni Taishite Nebarizuyoi Kouwan-kouzoubutsu no Sekkei-shuhou ni Kansuru Kenkyu. ministry of Land, Infrastructure and Transportation, Tokyo, Japan (in Japanese).

IAEA (International Atomic Energy Agency) (2011) IAEA Briefing on Fukushima Nuclear Accident (26 April 2011, 18:00 UTC). IAEA, Vienna, Austria. See http://www.iaea.org/newscenter/news/2011/fukushima260411.html (accessed 02/08/2013).

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