United Nations Scientific Committee on the Effects of Atomic Radiation

ELECTRONIC ATTACHMENTSUMMARY OF THE MAIN OUTCOMES OF MEETINGSWITH THE JAPANESE RESEARCH COMMUNITY
Developments since the 2013 UNSCEAR report on the levels and effects of radiation
exposure due to the nuclear accident following the great east-Japan earthquake and tsunami
A 2017 white paper to guide the Scientific Committee’s future programme of work

Notes
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© United Nations, October 2017. All rights reserved, worldwide.
This publication has not been formally edited.

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Contents
I.

INTRODUCTION .............................................................................................................. 3

II.

ATMOSPHERIC SOURCE TERM AND SUBSEQUENT DISPERSION AND
DEPOSITION ..................................................................................................................... 4

III.

RADIONUCLIDE RELEASES, DISPERSION AND DEPOSITION IN THE
OCEAN............................................................................................................................... 5

IV.

TRANSFER OF RADIONUCLIDES IN THE TERRESTRIAL
ENVIRONMENT ............................................................................................................... 5

V.

DOSES TO THE PUBLIC ................................................................................................. 6

VI.

DOSES TO WORKERS ..................................................................................................... 7VII. HEALTH EFFECTS FOR PUBLIC AND WORKERS .................................................... 7
VIII. DOSES AND EFFECTS FOR NON-HUMAN BIOTA .................................................... 8
IX.

IMPLICATIONS FOR THE COMMITTEE’S FOLLOW-UP ACTIVITIES ................... 9

REFERENCE ............................................................................................................................... 9I.
1.

INTRODUCTION

The objectives of the meetings with the Japanese research community were:(a) To exchange information on gaps and uncertainties in assessments of the health andenvironmental impacts of radiation exposure due to the accident at the Fukushima Daiichi
Nuclear Power Station (FDNPS) and how further research could improve the quality androbustness of the assessments;(b) To exchange information on the objectives, scope, content, status and envisaged
outcomes of major Japanese research projects/programmes and determine the extent towhich they address the research needs identified in the 2013 report;(c)
To better inform the Committee when making judgements on if, and if so when, it
may be appropriate to update its 2013 report;(d) To establish mechanisms to enable effective dialogue and exchange of information
between the Committee and the Japanese research community.

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2.
Two meetings were held in Japan in the period 13 to 17 November 2016. The first washeld in Tokyo to discuss projects/programmes being carried out or funded at a national level; thesecond was held in Fukushima City for those projects/programmes being carried out largely
under the auspices of the Fukushima Prefecture. Members of the Expert Group and the JapaneseWorking Group attended both meetings, together with lead researchers for each project/programme and representatives of a number of organizations that had commissioned/funded theresearch. The main outcomes of these meetings are summarized below.

II.

ATMOSPHERIC SOURCE TERM AND SUBSEQUENTDISPERSION AND DEPOSITION

3.
The 2013 report had provided estimates of the atmospheric source term due to theaccident and the subsequent dispersion and deposition. There are significant uncertainties forthe source term, both in the temporal patterns of the releases and for the estimates ofradionuclide concentrations—in air and from deposition—derived from the atmospherictransport and dispersion models (ATDM). There are also uncertainties in the understanding of
the chemical form of the radioiodine released during the accident.
4.
After the FDNPS accident, various ministries/agencies of the Japanese Government
have supported several major research projects/programmes. A “Comprehensive Study toAssess Radiation Doses to Residents from the Fukushima NPP Accident” (subsequently
referred to as the “Comprehensive Study”) is being undertaken with support from the Japanese
Ministry of Environment (MOE) for the assessment of radiation doses to residents from the
FDNPS accident. The MOE is also supporting a project concerned with radiation exposure andrisk from suspended particulate matter. A project on levels of radioactive material in air isbeing funded by the Japanese Ministry of Education, Culture, Sport, Science and Technology(MEXT) and by the Nuclear Regulatory Agency (NRA). The MEXT, NRA and MOE are also
funding a project on levels of radioactive material in soil, the ocean and non-human biota,
together with the mitigation of radioactive material in the environment.
5.
Within the Comprehensive Study, the Nuclear Science and Engineering Centre at theJapan Atomic Energy Agency (JAEA) is implementing a new meteorological model withenhanced data assimilation to provide improved ATDM simulations. It addresses theuncertainties in the source term and modelling by using improved ATDM results, actual
measurement data on radionuclides in the environment and an updated source term. This
includes improved estimates of 131I and other radionuclides in soil (derived from detailed
analysis of 129I in soil) and air (using air samples collected at the time of the atmosphericreleases. The updated source term is based on a new deposition scheme and updated
monitoring data. A database combining the ATDM outputs, the reactor inventory and the postaccident environmental measurements has been established to facilitate the optimization of the
ATDM simulations and to improve the estimates of radionuclides in the plume following theaccident.
6.
Within the study funded by MEXT, the Fukushima Environmental Safety Centre at
JAEA is leading a study aimed at characterizing and mapping the ground deposition around
FDNPS, based on the results of large scale environmental monitoring programmes, combinedwith investigations of radionuclide migration in the environment. Use is being made of theextensive measurements of air kerma rates from the monitoring at fixed locations and from thesurveys using measurement systems that are hand-carried, car-borne and transported on rotary
wing aircraft (drones and helicopter). Data on radionuclide deposition on the ground, from theanalysis of soil samples and studies of 137Cs depth profiles in soil, have been used to produce

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detailed maps that show the temporal and spatial variations of the ground deposition. Data
from the atomic mass spectrometry measurements of 129I in soil samples provide improved
maps of 131I deposition. Information on the ratios of ground deposition of 134Cs to 137Cs has
been used to estimate the contribution from each reactor unit to the ground deposition at
different locations around FDNPS. Measurements of temporal decreases in air kerma rates byhandheld and car-borne monitors have been used to estimate air kerma rates into the future.
These environmental monitoring data have been compiled in a database and the air kerma rates
have been combined with information on individual patterns of behaviour to estimate potential
doses from external exposure for individual evacuees returning to their homes.

III. RADIONUCLIDE RELEASES, DISPERSION AND DEPOSITION IN
THE OCEAN7.
The 2013 report had provided estimates of the radionuclide releases, dispersion anddeposition in the ocean from the FDNPS accident. There is large variability in the publishedestimates for releases and discharges to the ocean and further research is needed to improve theestimates of the magnitude of the releases and the understanding of the dispersion in the Pacific
Ocean of radionuclides from the accident.
8.
The Nuclear Science and Engineering Centre at JAEA is undertaking studies toquantify the magnitude of releases of radioactive water from FDNPS to the ocean. Levels of137
Cs are being monitored in seawater close to FDNPS and in the surrounding coastal area. A
seabed coating inside the port of FDNPS and a sea-facing impermeable wall have significantly
reduced the leakage rate of radiocaesium from the port, but measurements show that someleakage continues. Data are available on the inventories and fluxes to the ocean up to the year
2014 and further studies and monitoring will allow the forecast of levels into the future.

IV. TRANSFER OF RADIONUCLIDES IN THE TERRESTRIAL
ENVIRONMENT
9.
The estimation of ingestion doses to the public beyond the first year in the 2013 report
had been based on the use of the FARMLAND model [B1] using very conservative
assumptions. At the time of the assessment there had been limited data on concentration ratios
and transfer factors for rice, fish, crops, animals and other foodstuffs in Japan, and values for
European conditions had generally been used in the model. There is a need for data on thevalues of these model parameters for Japanese conditions to improve the assessment of doses
to the public and to quantify the impact of remediation on these doses.
10.
The Fukushima Environmental Safety Centre at JAEA is undertaking several relevant
studies: one is assessing the migration of radionuclides in the terrestrial environment; theFukushima Mapping Project, carried out in collaboration with a number of universities andinstitutes, is looking at the mechanisms of radiocaesium migration in various environmental
media, mainly in the Abukuma river basin, where the lead is being taken by Tsukuba
University; and the F-Trace Project aims to study the behaviour of radiocaesium in the forests
affected by the FDNPS accident and to evaluate its transport through river systems to the ocean.
11.
The Institute of Environmental Radioactivity (IER) at Fukushima University isundertaking six projects associated with the FDNPS accident, covering radionuclide transport in
the terrestrial and aquatic environments, the physio-chemical forms of radionuclides, long-term
behaviour of radionuclides in the marine environment, the long-term behaviour of radionuclides

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in ecosystems, and the development of tools for simulation of radionuclide dynamics and for themeasurement of radionuclides. One study at IER on radionuclides in the aquatic environment isinvestigating the wash-off of radiocaesium from the river catchments of Fukushima Prefecture,
the vertical migration and distribution of radiocaesium in soils, the removal of 137Cs from water,
and the monitoring of 137Cs in soil and bottom sediments in lakes and rivers.
12.
Further studies at IER are aimed at modelling radionuclides in the aquatic environment,
including the modelling of pathways for transport of radionuclides in rivers and reservoirs
affected by the accident, and the application of hydrological dispersion models in an analysis
of decontamination.

V. DOSES TO THE PUBLIC
13.
The aim of the assessments carried out for the 2013 report had been to make realistic
estimates of doses to the public from the FDNPS accident, based on the data and information
then available. The priorities for research to improve the assessment of doses to the public had
included: the further measurement of dose rates due to external exposure to deposited material
in various environments, together with studies to forecast and track changes over time andquantify the impact of environmental remediation programmes; better characterization of
distributions of doses to the public, including the variability between individuals anduncertainties; and the use of improved models with parameters specific to Japan.
14.
Estimates of radiation doses to residents from the FDNPS accident are being made aspart of the Comprehensive Study. Account is being taken of uncertainties in the source term
and atmospheric dispersion modelling by using improved ATDM results, actual measurementsof radionuclides in the environment and information on individual behaviour following theaccident. Improved estimates of 131I and other radionuclides in soil and air, derived fromdetailed analysis of 129I in soil and air samples collected at the time of the atmospheric releases,
are being made. Estimates of doses to residents of Fukushima Prefecture from internal
exposure in the early phase of the accident are also being made. A gamma spectroscopic
analysis of data from the body surface screening measurements carried out on evacuees andresidents during March 2011 has been used to improve estimates of doses due to inhalation at
different locations. In a study of doses from ingestion of food and water, information on
individual behaviour and ATDM results were combined to estimate doses to the public fromintake of tap water following the accident.
15.
The National Institute for Quantum and Radiological Science and Technology – National
Institute for Radiological Science (QST-NIRS) is carrying out studies to estimate doses toresidents of Fukushima Prefecture from internal exposure in the early phase of the accident.
Doses to the thyroid have previously been estimated from the limited number of direct thyroid
measurements and from whole body measurements. Published information on the individual
evacuation behaviour of the residents and maps of radionuclide concentrations in air from recent
ATDM modelling have been used to enhance the previous approach and provide better estimates of
the thyroid doses for evacuees. In addition, a two-year study is proposed to develop parameters forrate of uptake into the thyroid and for thyroid volumes more specific to Japanese people.
16.
The Fukushima Prefecture Government has established the Fukushima HealthManagement Survey (FHMS), which is implemented through Fukushima Medical University(FMU), local Governments and commissioned institutes. One part of the FHMS is the “Basic
Survey”, which aims to provide dose estimates for the approximately 2 million residents inFukushima Prefecture. The FMU is responsible for the estimation of the external dose for the

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first four months after the accident for residents in all Fukushima Prefecture municipalities.
These estimations are derived from information on individual behaviour from the Basic Survey
questionnaire, combined with data for dose rates as a function of time and location. Doseestimates from external exposure have been carried out for most of the residents participatingin the survey, using behavioural data from the questionnaire. Updated results of these analyses
are provided regularly to an oversight committee and are published online. Survey participants
are provided with their own individual dose assessment. A method has been developed toestimate doses to those who have not responded to the survey.

VI. DOSES TO WORKERS
17.
For the assessment of doses to workers involved in the accident, priorities for research
identified in the 2013 report had included: the quantification of uncertainties in reported doses
to workers (arising from differences in the individual worker histories, the time varying levelsof radionuclides and dose rates where the workers worked and rested, the use of protective
measures and the use of shared personal dosimeters); and the estimation of doses to the lens of
the eye for workers involved in the on-site mitigation strategies.
18.
A dose reconstruction study initiated by the Ministry of Health, Labour and Welfare(MHLW) is underway as part of the worker epidemiological study organized by the Radiation
Effects Research Foundation (RERF) to provide improved estimates of doses to workers due toboth internal and external exposure. A project is underway to re-evaluate doses to the thyroidof the most heavily exposed workers by computational simulation based on voxel phantoms
and Magnetic Resonance Imaging measurement. A probabilistic assessment of uncertainties inthe doses to workers arising from uncertainties in the intake scenarios is underway. Futurestudies include the creation of a database of information on the emergency operations andperformance testing of the personal dosimeters for irradiation geometry, protective equipment
and shielding effects.

VII. HEALTH EFFECTS FOR PUBLIC AND WORKERS
19.
The 2013 report had included a commentary on the health implications for the public
and workers arising from radiation exposure due to the accident based on the data andinformation then available. Priorities for research had included the continuation of the healthsurvey in Fukushima Prefecture, the analysis and quantification of the impact ofultrasonography surveys on the apparent incidence of thyroid cancer in Fukushima Prefecture
and the consideration of establishing a cohort for epidemiological study with members whose
individual doses could be adequately assessed. For workers, priorities included the screening ofworkers for thyroid cancer and the monitoring of the more highly exposed workers for longterm health effects.
20.
The “Detailed Survey” in FHMS aims to assess and monitor the health and wellbeing ofresidents of Fukushima Prefecture. It includes a “Thyroid Ultrasound Examination”. There ispublic concern about thyroid cancer among children and an expectation for ultrasoundexaminations. Mass screening programmes carry the possibility of over-diagnosis and standard
protocols were developed to minimize screening effects. The full scale survey programme
started in 2014 and is now in its third round of examinations.

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21.
The Detailed Survey also includes a Comprehensive Health Check to address any
health issues at an early stage. It is mainly aimed at former residents of the evacuation zones.
The examinations are carried out at locations within Fukushima Prefecture and at accredited
locations around Japan. These studies include a longitudinal study of cardiovascular risk
factors such as changes in body weight, and prevalence of hypertension, diabetes mellitus,
dyslipidaemia, liver dysfunction, atrial fibrillation and increased mean body mass. The study
will provide a better understanding of the health implications of the FDNPS accident for
Fukushima residents.
22.
A “Mental Health and Lifestyle Survey” aims to provide a better understanding ofphysical and mental health and lifestyle of residents of Fukushima Prefecture and a “Pregnancy
and Birth Survey” aims to provide appropriate medical care and support to mothers.
Measurements using Whole Body Counters and personal dosimeters are being conducted aspart of the health care services, and the data will be collected in a database by FMU.
23.
RERF is undertaking an epidemiological study on the health effects among the FDNPS
emergency workers. The Nuclear Emergency Worker Study (NEWS) is a prospective cohort
study covering the lifetime of the workers exposed in 2011. The major components of the study
include a health examination, a thyroid cancer study, a cataract study, a study of psychologicaleffects, a mortality/cancer incidence study and a radiobiological study. The radiation dose
estimates include both physical and biological dose estimation methods. A network of medical
institutes has been established across Japan to undertake the health examinations. Standard
procedures and a quality assurance programme for the health tests have been established.
NEWS will make use of the database of the National Cancer Registry System that wasestablished on 1 January 2016. A computerized communication system will support theexchange of information for the study. Work is currently underway to recruit study participants
to establish the lifetime cohort study population.

VIII.

DOSES AND EFFECTS FOR NON-HUMAN BIOTA

24.
The 2013 report had included an assessment of the exposures of non-human biota andassociated effects as a result of the accident. Priorities for research had included further
analysis of environmental effects reported in field studies to determine whether radiation
exposure was an important factor.
25.
The Biodiversity Policy Division in the Ministry of Environment is carrying out anumber of studies of radiation effects on wild plants and animals following the accident. One
study is measuring 134Cs and 137Cs concentrations in plant and animal samples from high andlow dose rate areas around the restricted areas. A programme to record environmental changes
using cameras at fixed locations is also underway.
26.
The Institute of Environmental Radioactivity (IER) at Fukushima University is
studying wildlife populations chronically exposed to radiation from the accident. The studies
include an examination of the impacts on wildlife populations in the evacuated zone, theaccurate determination of the radiation dose for free-ranging animals (such as wild boar)
through the use of portable tracking and radiation measurement tools, and collaborative studies
to evaluate sublethal chronic effects on wildlife at low doses.

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IX. IMPLICATIONS FOR THE COMMITTEE’S FOLLOW-UP
ACTIVITIES
27.
Within the next two to three years (i.e. by 2020), these ongoing studies are expected toprovide:(a) Significant improvements in estimates of the source term for releases to atmosphere(both in the temporal pattern and physico-chemical forms of the released material) and inmeasured and estimated levels of radionuclides in the environment (both airborne anddeposited on the ground);(b) Improved estimates of the amounts of radionuclides released to the ocean, how they
have varied with time and of their subsequent dispersion in coastal waters and more widelyin the Pacific Ocean;(c)Enhanced understanding of the transfer of radionuclides through the terrestrial
environment, enabling the development of improved models (and parameter values) thatare specific to Japanese conditions;(d) Better estimates of the doses received by members of the public, in particular doses
from internal exposure to short-lived radionuclides in the early phase of the accident, doses
from external exposure and how they varied according to behaviour and location, and doses
from the ingestion of foodstuffs from the second year after the accident onwards;(e)

A better understanding of the impacts of remediation;(f)

Improved estimates of doses to workers from internal and external exposure;(g)

Further information on the health of residents of Fukushima Prefecture;(h) Further evidence to help clarify the extent to which radiation exposure as a result of
the FDNPS accident has resulted in population-level effects on non-human biota.

Reference
B1

Brown, J. and J.R. Simmonds. FARMLAND a dynamic model for the transfer ofradionuclides through terrestrial foodchains. NRPB-R273. National RadiologicalProtection Board, Chilton, 1995.