Preparing a scientific report to the General Assembly on 'Exposures due to the nuclear
accident following the Great East-Japan earthquake and tsunami'
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2012 J. Radiol. Prot. 32 N113
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JOURNAL OF RADIOLOGICAL PROTECTION
J. Radiol. Prot. 32 (2012) N113–N118 doi:10.1088/0952-4746/32/1/N113
Preparing a scientific report to the General Assembly
on ‘Exposures due to the nuclear accident following the
Great East-Japan earthquake and tsunami’
Chair of UNSCEAR, Vienna International Centre, PO Box 500, A-1400 Vienna, Austria
Federal Office for Radiation Protection (BfS), Department of Radiation Protection and Health,
Ingolstaedter Landstraße 1, 85764 Oberschleissheim, Germany
Received 30 January 2012, accepted for publication 1 February 2012
Published 6 March 2012
Online at stacks.iop.org/JRP/32/N113
At its 58th session in May 2011, the United Nations Committee on the
Effects of Atomic Radiation (UNSCEAR) decided to carry out, once sufficient
information was available, a full assessment of the levels of exposure and
radiation risksattributable totheFukushimaaccident. Itenvisagesa preliminary
document for consideration at its 59th session in May of 2012 and a more
complete report for the 60th session of the Committee in 2013. This paper
summarises the aims and objectives of the project, the scope, the working
arrangements as well as the relation of the work to other activities.
At its 58th session in May 2011, the Scientific Committee considered the implications of
the nuclear power plant accident of March 2011, as far as radiation levels and effects were
concerned. The Committee expressed its sympathy and solidarity with the Japanese people and
wished for a prompt recovery from the aftermath of these devastating natural events. It also
conveyed to the Japanese scientists that were currently assessing the radiation consequences
its availability to support their efforts.The Committee has extensive experience in the
appropriate scientific methodologies for exposure assessment of accidental releases. It has
recently published reports on the current scientific knowledge of radiation-related heath effects
(including those related to accidental exposure, mainly after Chernobyl and focused at low
doses and dose rates) [1, 2]. These could serve as a basis for assessment of the radiation levels
and effects attributable to the accident. The Committeerecognised that the emergency situation
in Japan was still in progress and thus a Committee report based on current information and
possible effects attributable to the accident would be incomplete. In addition, there was a vast
amount of environmental data that had been and would continue to be collected. It is likely
© 2012 IOP Publishing LtdPrinted in the UK
Figure 1. UNSCEAR’s Fukushima assessment working arrangements.
that the data from the accident would take many months to analyse. Notwithstanding this, the
Committee recommended starting with the compilation of all relevant data and information as
soon as possible.
The Committee decided to carry out, once sufficient information was available, a full
assessment of the levels of exposure and radiation risks attributable to the accident. It envisages
a preliminary document for consideration at its 59th session in May of 2012 and a more
complete report for the 60th session of the Committee in 2013. The work will heavily rely
on in-kind contributions of key experts and organizations who are willing and able to work
intensively to produce the report in a short period of time.
The UNSCEAR report will only assess the levels of exposure and related scientifically based
health effects. Major focus will be related to the quality of measurements and possible organ
dose calculations for specific subpopulations. One top priority will be the collection and
assessment of some specific radionuclides, related for example to thyroid cancer or leukaemia
The report will not address policy matters or identify lessons to be learned with respect
to nuclear safety, radiation protection, environmental protection, emergency preparedness and
response, or public health actions. It will be critical to maintain close coordination with
activities being undertaken by the Japanese government, in order to avoid confusion and
The report will define or adopt methodologies to estimate doses for different population
groups inside and outside of Japan. These dose estimates will be based on available data
and information, obtained through official channels, published in the open literature, or from
other sources where the quality of the information can be assured. The report will briefly
discuss any other published assessments that are available. A detailed dose assessment will be
conducted for the first year based on measurements made in the first year and state-of-the-art
models. Projections for indicative doses in coming years will be made based on past scientific
Uncertainty/sensitivityanalyses will be performed, as appropriate, to allow the Committee
to make qualitative statements of the confidence in its conclusions.
The interim report will discuss issues which the Committee can be sure of at that point
(beginning 2012). On the other hand, the main scientific report for the 60th session of
UNSCEAR in 2013 has to be extremely well written and supported by evidence documented
withfullrigour. The typicaltargetaudience besidepoliticianswould bescience journalists. The
report’s annexes will contain more detailed information for scientists. It would be likely that
another more complete and definitive report would be needed several years after the accident
TheChernobylexperience tellsustoexpect publicdistressandanxiety, and concerns about
the long-term implications of the accident . The work of UNSCEAR will be very important
to provide an independent authoritative assessment of the long-term implications of radiation
exposure from radionuclides in the environment. UNSCEAR can contribute much to providing
better background information to help improve the understanding of the public and decision-
makers about radiation and its effects. The effects of long-lived radioactive material in the
environment will likely continue to be of concern long after the physical recovery from the
tsunami is complete. It will be important for the global community to respond in a coordinated
and thoughtful manner in coming years.
Specific objectives of the UNSCEAR work will be to address the following questions.
• What is the amount and nature of radioactive material released to the environment? How
much to air? How much to sea?
• What radionuclides were released?
• What was the time profile? What events led to releases and the dispersion patterns?
• What are the uncertainties on the source term estimates?
Environmental dispersion and deposition.
• What was the dispersion pattern (air and sea)? What were the atmospheric concentrations
of radionuclides with time and location? What are the deposition pattern and modalities?
What radionuclides were deposited?
• Where are the hotspots and how can they be explained?
• How does it compare with accidents at Chernobyl, TMI, and Windscale?
Doses to members of the public.
• What effects due to radiation were observed if any?
• Which are the key exposure pathways?
• What were the levels and time profiles of contamination in various foodstuffs (farmed and
natural), and expectations based on past experience?
• What were the protective actions taken, who was affected and when?
• What were the key organ and effective doses to adults, children, infants, and foetuses
for each prefecture (and some specific settlements/districts) and in other countries and/or
regions of the world?
116 W Weiss
• What were the doses for the first year based on measurements?
• What is the effect on these dose estimates from the ongoing remediation and protective
• What doses are projected for beyond the first year?
• What are the uncertainties associated with the dose estimates?
• What were the populations most at risk?
Doses to occupationally exposed persons.
• What effects were observed if any?
• What were the exposures of operational staff and emergency response personnel (levels, at
what times)? Key organ and effective doses?
• What are the uncertainties associated with estimates of their doses?
• What were the working conditions that affected exposure?
• What groups of workers were most at risk? How can they be characterised?
• What medical monitoring was implemented in groups of workers most at risk?
Effects on the natural environment
• What effects were observed if any?
• In what components of the natural terrestrial and aquatic environments and in which
species are there significant accumulations of radionuclides?
• What in general terms were the doses and dose rates to plants and animals?
• What are the uncertainties associated with those dose estimates?
• How do they compare with normal exposures?
• Did any plants or animals receive doses at levels at which UNSCEAR would expect
• How confident is UNSCEAR in the representativeness and quality of the information, and
of their assessment?
• What is the likely impact on human health and environment? For what time period are
effects expected and of what type?
• What are the unknowns and needs for future research or follow-up?
5. Working arrangements
A kick-off meeting has been organised on 30 June/1 July 2011 to conduct preliminary planning
of the UNSCEAR assessment. 34 participants from 10 state members of UNSCEAR and three
observer countries as well as from four international organizations attended the meeting. The
main objectives of the meeting were to agree on the work plan which had been developed
in close co-operation with the Japanese counterparts (Permanent Mission of Japan in Vienna,
NIRS, NSC) and to find ways in moving forward to getting relevant data for the assessment.
The work will be organised in four groups:
Group A: data compilation, screening, QA, documentation;
Group B: radionuclide releases and dispersion;
Group C: dose and risk assessment: (a) humans and (b) biota;
Group D: worker doses and health effects.
The management of the work will be performed by Weiss (BfS) and Yoshiharu Yonekura
(NIRS) in close co-operation with the UNSCEAR secretariat.