Radiation Information Evaluated bythe Radiation Effects Subcommitteeof the NSIC of AESJ
in the Fukushima Nuclear Disaster
Faculty of Engineering, Fukuyama University
Itsumasa URABE

The Japanese Nuclear EmergencyResponse System
 Act on Special Measure Concerning Nuclear

Emergency Preparedness.
 Basic Disaster Prevention Plan.(Vol.15)
 Guideline for Protective Actions toRadiological Disasters by Nuclear Accidents(NSC Japan).

Basic Ideas in the Emergency Response System:
１．Quick establishment of initial response organizations.
２．Co-ordination and integration between national and localgovernments.

Some Difficulties in the Early Stage ofEmergency Response to the Nuclear
Disaster
Emergency monitoring system had not worked for longtime.
 The information from the SPEEDI system did not utilized
for planning protective actions because the necessary
information from the plant could not be obtained.
 Failure of the systematic emergency monitoring forplanning appropriate protective actions. (spatialdistribution, priority, ranking) Determination of protective actions was done with having
no relation with emergency monitoring information.
 Confusion between dose and dose rate or total amount of
intake and concentration of radioactive materials.
Radiation Effects Subcommittee Organized inthe Fukushima Nuclear Disaster
Sections ofAESJ

Health Physics・Environmental Science, Radiation
Engineering, Sociological Environment

Member

I.Urabe, T.Hattori, H.Yamazawa, S.Yokoyama, T.Takahashi,
T.Momose, I.Iimoto, T.Iguchi, H.Hirayama, H.Takahashi,
M.Uematsu, T.Sanami, H.Nakashima, T.Iwai, M.Morokuzu,T.Mishima, T.Inamura, T.Sawada

Purpuses

・Contribute to decrease reasonably the doses of the public
exposed to radioactive materials released from the reactor
and the workers engaged in protective action.
・Prepare the radiological information which will contribute toinvestigate the problems raised in the future.
・Communicate with the people in the world on the experienceof emergency response to radiological disasterIssues Discussed in this Subcommittee
Estimation of total amount of radioactive materials
released from the reactors.
 Collection, analysis, and evaluation of radiologicalinformation based on the monitored data.
 Radiation measuring technique needed under theradiological emergency.
 Management of exposure doses of the public and peoples
working for protective action.
 Co-operation of specialists belong to various scientificorganizations.
 Release of the finding information to the public ororganizations relating to the Fukushima radiologicaldisaster management.
From the Guideline to EnvironmentalRadiation Monitoring (Nu.Sci.Com.)-1
The 1st Stage of Emergency Monitoring
The 1st stage emergency monitoring should bestarted immediately after the declaration of thenuclear emergency, and it is required to be started
as soon as possible and the accuracy of the data is
not required as that at the 2nd stage.・・・
１．Evaluation of radiation exposure rates and released radioactivematerials (radioactive noble gases, radioactive iodine and uraniumor plutonium) in the natural environment around the nuclear facilities.
２．Evaluation of radioactive materials in drinking water, green
vegetables, milk and rain water .
３．Expeditious prediction of radiation doses for planning emergency
countermeasures against radiological disaster.

From the Guideline to Environmental
Radiation Monitoring (Nu.Sci.Com.)-2
The 2nd Stage of Emergency Monitoring
The 2nd stage monitoring should be ・・ after
confirming the slight release of radioactive materials
based on the prediction of the accident progression,and it is needed to collect information for evaluationof exposure doses of the public and the effects ofenvironment. ・・ data should be obtained moreaccurately than those required at the 1st stage.・・・
１．Detailed assessment of the movement of the released radioactive
materials is required for evaluation of radiation doses of the public.
２．Monitoring should be implemented at intervals of several days in wider
range of the 1st stage.
３．Monitored data will be used for release of protective measures.

1．Estimation of Radioactive Materials
Released from the Reactors (1) Total amount of radioactive materials wereestimated on the basis of

１．Monitored data around the site boundary of the nuclear
facilities and environmental monitoring data by Fukushima
prefecture.
２．Calculation by the System for Prediction ofEnvironmental Emergency Dose Information (SPEEDI)
131I(Bqh-1)

1016
1014
1013～1012

137Cs(Bqh-1)

⎛ 1
⎜
⎝ 100

⎞
1⎟
⎠

of 131I

periodA few hours
A few days
About 2 weeks

1．Estimation of Radioactive Materials
Released from the Reactors (2) The atmospheric diffusion of radioactive materials

were evaluated１．Evacuation area (within 20km
radius from the plants)
２．The area up to several tensof km northwestward of thenuclear power plants.
３．Wide spread Area
(Fukushima Nakadori, Tohokuand Kanto Districts)

H.Yamazawa and S.Hirao;J.AESJ,53(7) 2011

2．Preparation of the Plane View ofExposure Rate Distribution (1) Evaluation of the exposure pathways to the publicRadioactive Materials in the Atmosphere

Agricaltural Products

Soil & Othe Surface

Water
External(Cloud)Internal(Inhalation)
Shipping Restrictions
Ingestion Restrictions

Internal(Food & Water)

External(Deposited)The Public

１．Main exposure path way was the external exposure by radioactive materials
released to the air or to the sea.
２．Internal exposure by inhaling radioactive materials could not be estimated.

2．Preparation of the Plane View ofExposure Rate Distribution (2) Findings from the plane view of exposure rates
１．Exposure rates morethan 20 μSv h-1 wereobserved in the planned
relocation area in thenorthwestward from thenuclear power plants.
２．Exposure rates around
1μSvh-1～5μSvh-1 werewidely observed andrelatively high exposure
rates were observed inNaka-dori area of
Fukushima prefecture.

Exposure rate

2．Preparation of the Plane View of
Exposure Rate Distribution (3)The analysis procedure employed here was subsequentlyapplied as a methodology for investigation of environmental
radiation dose distributions for planning radiologicalcountermeasures.

Exposure rate distribution reported by the MEXT on August 2, 2011

2．Preparation of the Plane View of
Exposure Rate Distribution (4) Some Notes to be considered in case ofannouncing radiation information to thepublic

１．It is needed to provide detailed explanation notto make inhabitants feel anxiety and not tocause social confusion.
２．It is very important to prepare discussion
among stakeholders on the effects resulting fromthe announcement of radiation information.

3．Estimation of Radioactive Materials
Released to the Sea Area (1) Support to radioactivity analysis of seawater andseafood planned by National Nuclear Emergency
Preparedness Organization.
 Study on the movements of radioactive materials
in the seawater and ocean soil.
１． The contamination process of the ocean soil and fish
was clarified from the movement of radioactive materials
estimated by the realistic analysis system using
atmosphere-ocean combined model for contaminationmaterials.
２． Contamination of sea area was significantly caused bysome percentage of the radioactive materials released tothe air.

3．Estimation of Radioactive Materials
Released to the Sea Area (2) Study on the movementsof radioactive materials
in the seawater andocean soil.

１． It was clarified from themovement of radioactive
materials in the coastal zone of
the nuclear power plants thatradioactive materials is still
releasing from the power plants tothe sea.
２． International consensus on therelease of radioactive materials
toward the sea area will be
required in the future.
Reported by D.Tsumune on July 2, 2011

Future Problems
Understanding of realistic radiological condition of theliving environments where the public would live again.
 Communications among stakeholders to choose
appropriate countermeasures to reduce radiation doses
as low as reasonably achievable.
 Requirements to release from the nuclear andradiological emergency situation.
 Reconstruction of the nuclear emergency preparedness
system based on the lessons learned from thecountermeasures performed in the early stage of theradiological emergency.
・Establishment of network among the organizations as early as
possible for planning countermeasures based on the radiation
information derived systematically.
・Estimation of radiation doses of the public and the workers engaged inprotective actions under the emergency exposure condition.