The Fukushima Nuclear Power Plant accident and exposures in the environment

The Fukushima Nuclear Power Plant accident and exposuresin the environment

Keiichi Akahane • Shunsuke Yonai • Shigekazu Fukuda •

Nobuyuki Miyahara • Hiroshi Yasuda • Kazuki Iwaoka •

Masaki Matsumoto • Akifumi Fukumura • Makoto Akashi

Published online: 17 January 2012

� Springer Science+Business Media, LLC 2012

Abstract The Great East Japan Earthquake has occurred

on March 11, 2011, in the Tohoku District of Japan. Due to

the earthquake, big tsunamis were induced, and they rushed

to the Fukushima Nuclear Power Stations, causing severe

accidents. Radioactive materials including I-131, Cs-137

and so on were emitted from the plant to the environment.

The Japanese government, Fukushima prefectural govern-

ment and other local governments have struggled against

the accidents. The restricted area and deliberate evacuation

area are set by the government, and the residents are

evacuated. The dose rates in and around Fukushima Pre-

fecture have been monitored by the governments and other

involved organizations. Fukushima government has started

the health management survey for all residents in Fuku-

shima Prefecture including the questions on their activities

for the estimations of their external doses.

Keywords Fukushima � Earthquake � Nuclear accident �Radiation exposure

1 The Great East Japan Earthquake

The Great East Japan Earthquake occurred at 14:46 on

March 11, 2011, in the Tohoku District of Japan, causing

severe damages to the area and the residents. The magni-

tude of the earthquake was estimated to be 9.0, which is the

highest recorded in the history of Japan. Until September

16, 2011, the number of death was 15,790; 4,056 persons

were missing; and 5,933 were wounded. Because of the

damages, many residents in Fukushima had to evacuate

from the area after the earthquake.

Due to the earthquake, big tsunamis occurred and rushed

to the coast of Fukushima, breaking and washing out many

persons, homes, buildings and many other things. The

Fukushima Dai-ichi Nuclear Power Stations located in the

towns of Okuma and Futaba near the coast (Fig. 1) were

also attacked by the tsunamis, and the external power

supplies for the nuclear power stations (NPS) were dam-

aged by these tsunamis. Subsequent accidents in the

buildings of the reactors emitted radioactive materials to

the environment.

The Japanese government has submitted two reports on

the accident at Fukushima Nuclear Power Stations to

International Atomic Energy Agency (IAEA) in June and

September 2011a, b. This article basically refers to the two

reports and some other sources. Some more recent data

were added.

2 Fukushima Nuclear Power Stations

There were 17 nuclear power plants in 13 prefectures in

Japan as of January 1, 2011, producing 48.847 million kW

electricity from 54 reactors. In Fukushima Prefecture, 10

boiling water reactors (BWR) were operated in 3 plants as

of January 1, 2011. The Fukushima Dai-ichi power plant is

one of them and has 4 BWRs (Fig. 2). After the earth-

quake, the first big tsunami reached the coast from the sea

at 15:27, 41 min after the earthquake, and the second wave

reached the Fukushima Dai-ichi Nuclear Power Stations

(NPS) at 15:35.

K. Akahane (&) � S. Yonai � S. Fukuda � N. Miyahara �H. Yasuda � K. Iwaoka � M. Matsumoto �A. Fukumura � M. Akashi

National Institute of Radiological Sciences (NIRS),

4-9-1, Anagawa, Inage-ku 263-8555, Chiba-shi, Japan

e-mail: [email protected]

123

Environmentalist (2012) 32:136–143

DOI 10.1007/s10669-011-9381-2

Since the waves of these tsunamis entered the Fuku-

shima Dai-ichi NPS site, the emergency generators of

electricity of NPS lost their abilities, and electric power

supply for the reactors stopped. Since the cooling systems

were damaged in the reactors, internal pressure levels

increased, and the hydrogen explosions occurred in the

first, third and forth reactors during March 12–15 (Fig. 3).

The monitoring data measured out of 20-km zone of the

NPS show that the dose rate levels were highest around the

explosions; subsequently, the levels have been decreasing

(Fig. 4).

A lot of radioactive materials including I-131 and

Cs-137 were released into the environment. According to

the estimation using MELCOR code by the Nuclear and

Industrial Safety Agency, the total amounts of radioactive

materials released were estimated to be 1–2 9 1017 Bq for

I-131 and 1–2 9 1016 Bq for Cs-137, respectively.

The radioactive materials released from the reactors

went into the air and moved as plume along with the winds

diffusing into the environments. The rainfall started on

March 15, so the radioactive materials also fell into the

surface of the ground under the way of the wind. Due to the

wind direction and the rainfall, the dose rate levels in the

northwest direction from the NPS became higher than that

in other areas.

3 Activities of the government and local governments

The Japanese government and local governments have

continuously struggled against the severe situations after

the earthquake and nuclear power plant accident based on

the regulations concerning the accidents since March 11.

The standards for the action on radiation protection mainly

refer to International Commission on Radiological Pro-

tection (ICRP) publications (Fig. 5).

On March 11, the Fukushima governor instructed

Okuma and Futaba towns to evacuate the residents within

2 km radius to other areas. The Japanese government also

instructed the local governments to evacuate the residents

within 3 km radius and to allow the residents within 10 km

radius to stay in their houses. On March 12, the Japanese

government instructed the stay-in-house residents within

10 km radius to evacuate from the area. On the same day,

the Japanese government instructed the Fukushima gov-

ernment, cities, towns and villages to evacuate the residents

within 20 km radius.

The Japanese government set ‘‘restricted area’’ to

evacuate the residents within 20 km radius from the

Fukushima Dai-ichi NPS on March 12, and the residents

within radius between 20 and 30 km were ordered ‘‘stay-

in-house’’ on March 15. In the restricted area, residents

have in principle been prohibited from access to the area.

The ‘‘stay-in-house’’ area was changed to ‘‘deliberate

evacuation area’’ and ‘‘evacuation-prepared area in case of

emergency’’ on April 22 by the government. In addition,

regions including specific spots, where accumulated dose

Tokai Dai-ni NPS

Fukushima Dai-ni NPS

Fukushima Dai-ichi

Onagawa NPS

Fig. 1 Locations of nuclear power stations including Fukushima Dai-

ichi NPS

Unit 4

Unit 3

Unit 2

Unit 1

Unit 5

Unit 6

Fig. 2 Fukushima Dai-ichi Nuclear Power Station

Environmentalist (2012) 32:136–143 137

123

Fig. 3 Damages by the explosions of units in Fukushima Dai-ichi NPS

Fig. 4 Dose rates at points out of 20-km zone of Fukushima Dai-ichi NPS

138 Environmentalist (2012) 32:136–143

123

was likely to reach 20 mSv within a year, were set to be

evacuation-recommended regions (Fig. 6).

On September 30, ‘‘evacuation-prepared area in case of

emergency’’ was cancelled by the government.

4 Environmental doses

The radiation dose levels have been monitored on many

points, not only around the NPS but also on other areas by

monitoring posts, etc. A lot of values of dose rates have

been reported by the Japanese government, local govern-

ments, related institutions and other related sources after

the accident, based on their own dose measurements.

Among them, for example, the measured data of aircraft

monitoring showed the air dose rate over 1 m above

ground level (Fig. 7). The dose rate distributions are

clearly shown in the above-mentioned figure. Estimated

dose rate as of August 11, 2011, is shown in Fig. 8. The

integrated dose map up to March 11, 2012, is also shown in

Fig. 9.

5 Dose limits for the workers

After the accident, many involved persons of Tokyo

Electric Power Company (TEPCO) and other organizations

have been working in and around the NPS site for bringing

the nuclear reactions under control and for reducing the

release of the radioactive materials. The dose limit for the

radiation workers have been set to be 50 mSv per year and

100 mSv for 5 years in the Japanese regulations on radia-

tion protection based on ICRP Publication 60. In emer-

gency case, the dose limit is 100 mSv in the regulation

laws. However, the limit was changed to be 250 from

100 mSv on March 14 as one of countermeasures against

this emergency situation.

The exposure dose levels of the workers between March

and July have been reported with the internal doses until

May (Table 1). The maximum dose was about 200 mSv,

and the average was about 8 mSv in the data of 16,633

radiation workers. The doses of six persons exceeded

250 mSv among them, and the range of the exposures is

from about 300 mSv to 670 mSv, with internal exposures

ranging from about 240 to 590 mSv.

As two radiation workers have worked putting their foot

in the retention water in Fukushima Dai-ichi NPS, their

feet were highly exposed to radiation in the water on March

24. They were hospitalized in the hospital of Fukushima

Medical University and NIRS. The dose levels were esti-

mated to be 2–3 Sv.

6 Doses of the residents

A simplified survey for thyroid internal exposure was

performed for 1,149 children in Iwaki city, Kawamata

town and Iitate village (Fig. 10). Of the 1,149 people, 66

Fig. 5 Criteria of the radiation

dose for the radiation protection


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people were in the locations having higher background

doses and the ages of 3 people were unknown, so the

thyroid doses of the remaining 1,080 people were mea-

sured. The doses were below 0.2 lSv/h, which is equiva-

lent to 100 mSv dose for 1-year-old children.

To roughly estimate the internal exposure levels, whole-

body counter (WBC) examinations have been done for 122

residents in Namie town, Iitate village and part of Kawa-

mata town from June 27 to July 16. The results showed that

the internal exposure doses to Cs-134 and Cs-137 were

estimated as low as less than 1 mSv even in total.

For considering the health of the residents in Fukushima,

Fukushima prefectural government has started the health

management survey for all residents in Fukushima Pre-

fecture (Fig. 11). This survey has been instructed by

Fukushima Prefecture and performed by Fukushima Med-

ical University in cooperation with National Institute of

Radiological Sciences (NIRS).

Minami Soma City

Iitate Village

Namie Town

Katsurao Village

Futaba Town

Okuma Town

Tomioka Town

Naraha Town

Hirono Town

Kawauchi Village

Tamura City

Kawamata Town

Date City

Iwaki City

Ono Town

Hirata Village

Nihonmatsu City

Soma City

Fukushima City

Koriyama City

Ryozenmachi-KamioguniTsukudatemachi-Tsukidate

Ryozenmachi-Ishida

Ohara, Haramachi WardOgai, Haramachi Ward

Takanokura, Haramachi Ward

Baba, Haramachi WardKatakura, Haramachi Ward

Oshigama, Haramachi Ward

Shimokawauchi

Deliberate Evacuation Area

Evacuation-Prepared Area in case of Emergency

Restricted Area

Regions including Specific Spots Recommended for Evacuation

Deliberate Evacuation Area



Restricted Area

Fukushima Dai-chi NPS

Fukushima Dai-ni NPS

20km

30km

Restricted Area, Deliberate Evacuation Area, Evacuation-Prepared Area in case of Emergency And Regions including Specific Spots Recommended for Evacuation (As of August 3, 2011)

Jisabara, Kashima Ward

Ryozenmachi-Shimooguni

Fig. 6 Restricted area, deliberate evacuation area and evacuation-prepared area in case of emergency around the Fukushima Dai-ichi NPS


123

The survey consists of two parts, namely the basic

survey and the detailed survey. The purpose of the basic

survey is to estimate exposure doses through filling in

action records by the residents after March 11. The ques-

tionnaires were sent to about 2.02 million people living in

the prefecture as of March 11. After the basic survey, the

detailed survey will be performed to examine the health

conditions of the residents in the prefecture and to manage

their health in the future. In the detailed survey, thyroid

gland examinations and medical checkups will be done for

the residents.

For the estimations of external exposures for the resi-

dents, the external dose calculation system was developed

by NIRS. The doses can be estimated based on the dose

rate maps from March 12 to July 11, 2011, and the action

data of the Fukushima residents collected from the Fuku-

shima Health Management Survey. The maps were made

using calculated data of the System for Prediction of

Environmental Emergency Dose Information (SPEEDI) for

March 12–14, because there are no sufficient measured

monitoring data to construct the dose rate map. For the

period of 15 March–11 July, the maps were made referring

to the MEXT monitoring data. Each map is constructed

with 2 km 9 2 km meshes, and each mesh has its own

dose rate value of effective dose (lSv/h). The background

dose rate values before the accident are reduced from the

monitoring dose rate for the meshes.

To grasp the exposure levels of the Fukushima residents,

18 evacuation patterns of the residents during 12 March to

11 July were assumed, and the external doses were calcu-

lated by the external dose calculation system of NIRS. The

doses were reported on 13 December. The doses of the

residents evacuated from the area within 20 km were

estimated to be less than several mSv, and the levels of the

residents from ‘‘deliberate evacuation area’’ were also

estimated to be less than 20 mSv.

Based on the returned questionnaires of the health

management survey of the Fukushima residents, the

external doses of 1,727 residents in Yamakiya area in

Kawamata town, Namie town and Iitate village have been

Fig. 7 Air dose rate over 1 m above ground level by air monitoring Fig. 8 Dose rate map estimated as of August 11, 2011


123

calculated and reported on December 13 by Fukushima

prefectural government. The results show that the doses of

62.8% of the residents excluding radiation workers are less

than 1 mSv. Among them, the estimated doses of 4 persons

were more than 10 mSv, and the maximum dose was

14.5 mSv.

7 Dose limits for the public

The tentative regulation values on the densities of radio-

active materials in eatables and drinkables were noticed by

the Ministry of Health, Labour and Welfare on March 17

(Table 2). The density values of I-131 were derived based

on the equivalent dose of thyroid, that is 50 mSv. For

cesium, these values were based on the effective dose

5 mSv. As of August 31, 16,584 inspections were carried

out, and there were 596 cases exceeding the provisional

regulation values.

8 Social reactions

The accident was very serious, and Japan has been strug-

gling for the settlement. For the adequate promotion of the

recovery, scientific evidence must be required as the basis.

It is obvious that specialists on radiation protection have to

do their best for the residents, the governments and the

general public.

Fig. 9 Integrated dose map estimated up to March 11, 2012

Table 1 Cumulative doses of radiation workers

Dose (mSv) External dose between March and July External dose between March and July ? the internal dose until May

TEPCO

employees

Employees of

subcontractors

Total TEPCO

employees

Employees of

subcontractors

Total

More than 250 0 0 0 6 0 6

250 or less but more than 200 0 0 0 1 2 3




50 or less but more than 20 413 1,049 1,462 560 1,250 1,810

20 or less but more than 10 613 1,582 2,195 532 1,700 2,232

10 or less 2,003 10,585 12,588 1,772 10,147 11,919

Total 3,236 13,397 16,633 3,236 13,397 16,633

Maximum (mSv) 182.33 199.42 199.42 678.08 236.42 678.08

Average (mSv) 13.20 6.80 8.03 19050 8.00 10.30

Fig. 10 Thyroid internal exposures of Fukushima children in

numbers


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References

Nuclear Emergency Response Headquarters of Government of Japan

(2011a) Report of the Japanese Government to the IAEA

Ministerial Conference on Nuclear Safety—The Accident at

TEPCO’s Fukushima Nuclear Power Stations, June 2011

Nuclear Emergency Response Headquarters of Government of Japan

(2011b) Additional Report of the Japanese Government to the

IAEA—The Accident at TEPCO’s Fukushima Nuclear Power

Stations—(Second Report), September 2011

Health Management Survey for the Residentsin Fukushima Prefecture (for all the prefecture’s residents)

Basic survey

Ascertain health conditions

Subjects: Residents in Fukushima prefecture as of March 11, 2011Method: Self-completion questionnaire Details: Record of actions since March 11

(estimated exposure dose evaluations)Details: Thyroid ultrasonography

* Ascertain the present condition of all survey participants in the next three yearsand conduct periodic examinations thereafter

Thyroid gland examination (to be conducted for all Fukushima prefecture residents aged 18 or younger, including those taking refuge outside the prefecture)

Subjects: Residents not residing in evacuation areas

Details: General medical checkup items

Having workplace medical checkups, municipal medical checkups and/or cancer screening helps ensure early detection and early treatment of diseases.

Conducting of medical checkups for Fukushima prefecture

Subjects: Residents residing in evacuation areas, etcDetails: General medical checkup items as well as differential white blood count, etc.

Detailed survey

Creation of a databaseUtilized for long-term healthcare and medicaltreatment of Fukushima prefecture residentsKnowledge acquired in providing healthcare will beused for future generations

Ongoing management

Results of health surveys and examinations recorded and retained by individualsIncrease awareness of radiation

Follow-up• Whole-body counter• Individual dosimeter

Ascertain radioactive dose (Basic data)

Medical checkups (utilizing existing medical checkups)

Consultation and support Treatment

Health management file(provisional name)

Survey regarding pregnant women and nursing mothers (questionnaire survey targeting residents who applied for a maternity and child health hanndbook between August 1, 2010 and July 31,

Survey regarding mental health and lifestyle (questionnaire survey targeting residents in evacuation areas, etc.)

Fig. 11 Health management

survey for the residents in

Fukushima Prefecture

Table 2 Index for the restrictions of intake noticed by the Ministry of Health, Labour and Welfare on March 17

Nuclides Index for the restrictions of intake (Bq/kg)

Radioactive iodine (typical: 131I) Water milk, milk products * vegetables (excluding roots and potatoes) 300

2,000

Radioactive cesium Water milk, milk products vegetables grain meat, egg, fish, others 200

500

Uranium Food for infants water milk, milk products vegetables grain meat, egg, fish, others 20

100

Plutonium and alpha-emitters of transuranic

elements (Sum of the densities of Pu-238,

Pu-239, Pu-240, Pu-242, Am-241, Cm-242,

Cm-243)

Food for infants water milk, milk products vegetables grain meat, egg, fish, others 1

10

* Guidance: Not use for infants when over 100 Bq/kg


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The Fukushima Nuclear Power Plant accident and exposures in the environment