Cooperation between the IAEA andFukushima Prefecture
In the Area of Radiation Monitoring, Remediation andWaste Management following the Accident atTEPCO’s Fukushima Daiichi Nuclear Power Plant

Interim Report(2013 – 2015)

IAEA, VIENNA 2016

1.

OBJECTIVES AND SCOPE

Following the accident at TEPCO’s Fukushima Daiichi Nuclear Power Plant 1 in March 2011, theFukushima Prefecture (hereinafter referred to as ‘the Prefecture’) and the IAEA concluded aMemorandum of Cooperation. Radiation monitoring, remediation, decontamination and human healthwere identified as propriety areas for cooperation. Concrete projects, as well as ways and means toimplement them, were discussed between the IAEA and the Prefecture.
Further to the Memorandum, the Practical Arrangements were prepared and signed between the IAEA
and the Prefecture. The objective of the Practical Arrangements was to set forth the framework forcooperation between the Prefecture and the IAEA, and to provide broad and extensive assistance in thePrefecture, in areas related to radiation monitoring and remediation, in order to ensure ongoingprotection of people and the environment from ionizing radiation in the Prefecture after the accident.
The Practical Arrangements were signed in December 2012 and are valid for a period of five years
after signature. It can be extended by the mutual consent of both sides. Implementation of the projects
under the Practical Arrangements began in March 2013 and are planned to conclude in December 2017.
The main role of the IAEA in implementation of these projects is the provision of effective technicalassistance and support based on international experience and best practices.
This interim report introduces activities undertaken during the implementation of individual projects
during the first three years (2013 to 2015) as well as highlights and results of this cooperation.

2.

TOPICS OF COOPERATIONThe IAEA and the Prefecture have identified the following areas and activities in which cooperation
may be pursued:Research and study on radiation monitoring including application of environmental mapping
technology by using unmanned aerial vehicles and the IAEA’s assistance in the use of radiation
monitoring data to develop maps to be made available to the public;

Research and study on off-site decontamination, including the IAEA’s assistance in analyses ofresults of environmental monitoring and exploration of exposure pathways in order to reduce oravoid exposure;Research and study on the management of radioactive waste including IAEA’s assistance in thestudy on management methods of low level radioactive waste from the above-referenced
decontamination activities.

The above-referenced cooperation is designed to complement existing Japanese activities and toprovide immediate assistance and support, which will be of direct benefit to those living in thePrefecture.

3.

ACTIVITIES AND ACHIEVEMENTS

3.1. OFF-SITE DECONTAMINATION AND ENVIRONMENTAL MONITORING
In the freshwater bodies of the Prefecture – more than four years after the accident – dissolved
radiocaesium2 levels in water are close to or below the detection limit. This can be explained by thestrong sorption of radiocaesium by sediments, in which much higher radiocaesium levels are observed.
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Hereinafter referred to as ‘Fukushima Daiichi NPP’
Hereinafter, the term radiocaesium includes 134Cs and 137Cs.

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In addition, due to radioactive decay, there is also a clear decline of the concentration of radiocaesiumin suspended sediments.
The reduction of the radiocaesium levels in the environment is mainly caused by radioactive decay,
whereas the runoff of radiocaesium provides only a minor contribution to the reduction of the overall
inventory in the catchment. When the radiocaesium is attached to particles, it is subject tosedimentation in ponds, lakes, and reservoirs i.e. such waters act as a sediment trap.
A key question of the work is related to the long term behavior of radiocaesium in the freshwater
environment. Therefore, in addition to the measurements of radiocaesium in water and sediments bythe Prefecture, mathematic models have been used to estimate the transport of radiocaesium from theupper part of a catchment area through the river system of the Prefecture to the Pacific Ocean. The
results of these calculations help with the interpretation of monitoring measurements. Additionally,such models provide valuable input when planning the possible effects of countermeasures.
At some locations, river banks are used for recreation by the local population. The Prefecture initiated anumber of demonstration projects to test the effectiveness of measures for reducing gamma dose rates
at recreation areas near rivers. Comprehensive measurements show that the gamma dose rates could be
reduced by about 50%.
Experience gained through remediation activities of freshwater bodies worldwide indicates thattechnical measures have only a limited potential to control the dispersion of radionuclides in water
bodies. For reducing exposures to the public arising from the use of water, experience has shown thateasy to implement recommendations and restrictions with regard to the use of freshwater bodies are
more effective in reducing exposure.
Since 2011, under coordination of the Prefecture, intensive decontamination work has been carried out
in private homes and public areas, on agricultural land and in forests. For public facilities,decontamination is the most advanced; as of 29 February 2016, 90% of the planned activities werecompleted. Depending on the type of area treated, gamma dose rates were reduced by a factorof 1.5 to 2. Such reduction factors are very similar to those achieved by remediation measures in areas
affected by the Chernobyl accident.

3.2. EVALUATION OF THE LONG TERM BEHAVIOUR AND IMPACT OFRADIONUCLIDES IN FORESTS
The importance of forests in the economy of the Prefecture and in the life of its inhabitants underlines
the need to understand the mechanisms of movement and cycling of radiocaesium within theseecosystems. One of the main sources of knowledge on the behaviour of radionuclides in forests is
research carried out in Europe in the years following the Chernobyl accident in 1986. However, forests
in Europe differ from those in Japan and the results of previous studies may not be directly applicable.
For that reason, an extensive forest monitoring program has been established by the Prefecture.
The research undertaken by the Prefecture suggests that clay minerals present in the forest soils in thePrefecture are helping to immobilize radiocaesium, resulting in a low transfer to understory vegetationand to trees. Given the importance of the forests as an economic resource, the relatively low
concentrations of radiocaesium measured by the Prefecture in harvested wood allows the unrestricted
use of timber. The IAEA has underlined the importance of assessing if this trend continues in futureyears.
Initial indications from work undertaken by the Prefecture are that the future planting of trees does notneed to be restricted as the levels of radiocaesium will be significantly reduced when these trees reachmaturity and are harvested in 50 to 80 years’ time. The Prefecture also recognizes that the reduction indose rate due to natural decay will gradually allow harvesting of wood from wider areas of forest, and3

this, however, in turn may bring need for monitoring of large volume of harvested timber, as well as
managing radiation exposure of forest workers.
Another important observation to emerge from the Prefecture’s monitoring programme is that the bulkof the radiocaesium initially deposited on the forests of the Prefecture has now been transferred to thesoil and litter layer, where it continues to contribute to the gamma dose rate. Most of the radiocaesium
initially deposited is retained within the forest and the amount of radiocaesium lost from the system todate seems to be low. This suggests that the contamination of nearby agricultural land is unlikely,
except in the case of a major landslide or other similar event. On the other hand, the half-life of 30years of 137Cs is a dominating factor in the reduction of gamma dose rate within the forest. Several
countermeasures, involving the addition of uncontaminated soil or wood chips, are currently beingevaluated by the Prefecture in terms of long term effectiveness and applicability.
The life cycle of forest trees from planting to harvesting is normally a number of decades. At the timeof the Fukushima Daiichi NPP accident, the forests that received fallout were at various stages ofdevelopment, from newly-planted saplings to fully mature trees ready for harvesting. The IAEA has
advised that the uptake of radiocaesium by forest vegetation and trees, and the redistribution between
the different components of trees, will need to be monitored for several years to ensure that the longterm cycling mechanisms are fully understood. Now that appropriate monitoring programmes havebeen established by the Prefecture, the IAEA has also advised that consideration can be given to
reducing the frequency of monitoring in future years. The knowledge gained will allow the forests to
be managed in an effective manner and to maintain them as both an economic and a leisure resource.

3.3. MANAGEMENT OF RADIOACTIVE WASTE FROM DECONTAMINATIONACTIVITIESThe safety assessment was carried out by the Prefecture using the IAEA methodology for assessing thesafety for predisposal radioactive waste management facilities and activities. The results of the safetyassessment have indicated that IAEA methodology is appropriate for the specific conditions andstorage facilities for radioactive waste in the Prefecture. The implementation process was supported byapplying the IAEA methodology – the SAFRAN software developed by the IAEA – for assisting indevelopment of the safety assessment for predisposal facilities and/or activities. It is standalone
software, which allow user to change/adopt the preinstalled parameters, enabling the iterative processof development of the safety assessment. It allows reviewing of the key steps relevant for safety, andtheir consequent refinements. This approach also assists in optimizing the main parameters responsible
for radiation safety in a consistent and traceable manner.
The results gained from application of the IAEA methodology by the Prefecture to the storage facilities
in the Prefecture clearly indicate that all radiation doses (calculated using a conservative approach) are
under normal operating conditions well below the prescribed dose limits. A systematic analysis of all
relevant hazards by the Japanese experts would provide a sound justification for further examinationand potential application of measures which might be necessary in future to avoid any type of undue
consequences to the human population and/or environment under the accidental situations.
The development of the safety assessment for the temporary storage facility at the Prefecture is an
important step in finding a safe and reliable solution for storage of the large amounts of radioactive
waste accumulated from remediation activities after the Fukushima Daiichi NPP accident.

3.4. THE USE OF RADIATION MONITORING DATA TO DEVELOP MAPS TO BE
MADE AVAILABLE TO THE PUBLIC
The Prefecture website is extensively used by the local population as an authoritative source ofinformation. The Prefecture sought the views of those who use the website in order to identify the typeof information they require and how the website can be improved to better meet their needs. The needfor the Prefecture to supplement the information available through the website with a broader outreach4

to the public was highlighted. In this regard, the Prefecture has identified the information needs ofreturning evacuees are particularly important.
Best international practice and experience in providing radiation data to the public was reviewed
among radiation protection, public information and IT experts. A wide range of options regarding data
presentation, including the use of interactive maps, were considered. Technical issues such as how topresent representative data, how to indicate long term trends in dose rate and how to merge data fromfixed monitoring stations and different types of measurement surveys, as well as different approaches
and practical solutions, were discussed.
Based on the discussions with IAEA experts, the Prefecture prepared a tender document to update its
website. The new website went live in 2016. Therefore, this project has now been successfully
concluded.

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