Radiation Monitoring and Remediation Following the
Fukushima Daiichi Nuclear Power Plant Accident

Cooperation between
Fukushima Prefecture and the IAEA

SUMMARY REPORT(2013 to 2017)[Fukushima Prefecture Initiative Projects](temporary translation)

March 2018
Fukushima Prefecture

Introduction
Fukushima Prefecture suffered immense damage from the Great East Japan Earthquake that occurred on
11 March 2011 and the accompanying disaster at Tokyo Electric Power's Fukushima Daiichi Nuclear Power
Plant1. Radioactive materials released into the environment contaminated the land and forced more than160,000 prefectural residents to evacuate. About 50,000 residents have still not returned home, even at thecreation of this report about 7 years after the disaster.
Concentrating the world's wisdom is important to restore the environment after the unprecedented nuclear
disaster, and create an environment where prefectural residents can make a safe living in the future. Therefore,
we initiated a collaboration with the International Atomic Energy Agency (hereinafter, IAEA), which has
extensive knowledge in the nuclear field. In December 2012, a memorandum of cooperation between
Fukushima Prefecture and the IAEA was signed. Based on this memorandum, a practical arrangement in thefields of decontamination and radiation monitoring between Fukushima Prefecture and the IAEA was signedon the same day (projects based on this arrangement are referred to as FCPs).
Following this, additional agreements were signed for five Fukushima Prefecture Initiative Projects(hereinafter, FIPs) with a period of 3 years in April and October 2013 as a new framework in which support
from the IAEA was provided for the projects implemented by Fukushima Prefecture. These agreements
initiated FIPs. In April and May 2016, agreements were signed to extend the cooperation period until
December 2017 and alter the extent of cooperation2.
[FIPs]
1 Survey of radionuclide movement in river systems
2 Survey of radionuclide movement with wild life
3 Countermeasures for radioactive materials in rivers and lakes
4 Development of environmental mapping technology using GPS walking surveys
5 Study of the proper treatment of waste containing radioactive materials at municipal solid waste
Incinerators
Fukushima Prefecture and the IAEA initiated cooperative projects in 2013. This report summarises theachievements about the part of FIPs out of the above projects over the past 5 years and provides a broad
overview of the future outlook.
We would like to express our gratitude to IAEA specialists, experts from international and domesticorganisations and local governmental staff for their assistance in these cooperative projects.
We expect this report to contribute to the safety and security of prefectural residents as well as people allover the world.

1

Tokyo Electric Power's Fukushima Daiichi Nuclear Power Plant transitioned to Tokyo Electric Power
Company Holdings’ Fukushima Daiichi Nuclear Power Plant on 1 April 2016.
2 In accordance with the change in the scope of cooperation, the names of FIPs havechanged.

Contents
1. FIP1 Survey of radionuclide movement in river systems ........................................................ 1
1.1. Purpose ........................................................................................................................... 1
1.2. Content of implementation .............................................................................................. 2
1.3. Results ............................................................................................................................ 4
1.4. Conclusions ................................................................................................................... 10
2. FIP2: Survey of radionuclide movement with wild life ......................................................... 122.1. Purpose ......................................................................................................................... 122.2. Content of implementation ............................................................................................ 122.3. Results .......................................................................................................................... 14
2.4. Conclusions ................................................................................................................... 23
3. FIP3: Countermeasures for radioactive materials in rivers and lakes ................................... 25
3.1. Purpose ......................................................................................................................... 25
3.2. Content of Implementation ............................................................................................ 25
3.3. Results .......................................................................................................................... 29
3.4. Conclusions ................................................................................................................... 35
4. FIP4: Developing of environmental mapping technology using GPS walking surveys ........... 37
4.1. Purpose ......................................................................................................................... 37
4.2. Content of implementation ............................................................................................ 38
4.3. Results .......................................................................................................................... 41
4.4. Conclusions ................................................................................................................... 47
5. FIP5: Study of proper treatment of waste containing radioactive materials at municipal solid
waste incinerators ................................................................................................................... 48
5.1. Purpose ......................................................................................................................... 48
5.2. Content of implementation ............................................................................................ 49
5.3. Results .......................................................................................................................... 54
5.4. Conclusions ................................................................................................................... 66
Contents of major support received from the IAEA ................................................................. 69

|1

1. FIP1 Survey of radionuclide movement in river systems
Abstract
It is important to provide the necessary information for the safe use of river water in the prefectural land
contaminated with radioactive materials. We conducted surveys of rivers in Fukushima Prefecture to clarify
the dynamics of radioactive materials, and to verify the accuracy of a simulation model.
In particular, we collected necessary data from the Hirose River to predict the dynamics of radionuclides
using the TODAM model. The simulation results indicated that the TODAM model could roughly reproduce
the concentration changes accompanying the downflow of radiocaesium at each monitoring point along theHirose River however, improvements in the accuracy of the model results are necessary.
In the Abukuma River system and the major rivers in Hamadori area, we investigated the flow dynamics
of suspended radiocaesium adsorbed by microparticles. According to this analysis, the suspended
radiocaesium concentrations are still decreasing. In addition, it was also shown that the migration ofradiocaesium was affected by dams at the basins and decontamination practices.

1.1. Purpose

River water is widely used for drinking
water and farming. In 2011, however, theaccident at Tokyo Electric Power's Fukushima
Daiichi Nuclear Power Plant resulted in wide
contamination of the prefectural area withradioactive materials. Since river basins werealso contaminated, it is important to clarify the
dynamics of radioactive materials in rivers andto provide the necessary information for thesafe use of river water. If radiocaesium
absorbed by suspended particulate matter andflows downstream in a suspended form, redeposition after events, such as floods, may
affect the ambient air dose rate. Accordingly,
the migration of dissolved radiocaesium
through the ecosystem should be considered(Figure 1). Thus, we evaluated the dynamics ofradiocaesium depending on its form. The

Figure 1: Schematic diagram describing dynamics ofradiocaesium in a river basin.

purpose of this survey is to investigate thedynamics of radiocaesium with river flow down in Fukushima prefecture and to verify it by model
simulation based on the monitoring data.

2|
1.2. Content of implementation(1) Survey of the Hirose River basin
A survey was conducted at the Hirose River and its tributaries during 5 year periods beginning infiscal year 2013. The Hirose River is a tributary of the Abukuma River. The Hirose River has catchments
close to an area of substantial radiocaesium deposition. Figure 2(a) shows a quantitative summary ofradiocaesium deposition on the ground surface in this basin. The amount as of 2 July, 2011 is refered ti
as the initial deposition in this document. We could find a red area, indicating high radiocaesium levels,
near the southeast boundary of the Hirose River basin. Radiocaesium deposition was also high in thebasins of the tributaries, the Nuno River and the Oguni River (Table 1).

Figure 2: Monitoring points in this survey and the initial amounts of Cs-137 in theseareas (as of 2 July, 2011).
(a) Hirose River basin. Numbers in the figure correspond to those in Table 3.
(b) Area included in the wide area river survey.
*Source: Results of the Third Airborne Monitoring by MEXT (2011).
http://radioactivity.nsr.go.jp/ja/contents/5000/4858/24/1305819_0708.pdf. In (b), the area
outside the third airborne monitoring range was evaluated by both the airborne monitoring
results by the prefecture (http://emdb.jaea.go.jp/emdb/en/portals/b224/) and the radiocaesium
deposition results from the first unattended helicopter survey within 3 km from the Fukushima
Daiichi Nuclear Power Plant (http://emdb.jaea.go.jp/emdb/portals/b225/).

|3
Table 1: Catchment area and initial Cs-137 deposition within the Hirose River basin.
Catchment area [km2]

Average Cs-137 deposition [kBq/m2]

Hirose River

267.9

231

Takane River

19.2

270

Nuno River

18.6

343

Ishida River

30.1

290

Oguni River

40.4

343

Figure 2(a) showed the nine monitoring points and table 2 listed the major monitoring items. River
water samples of about 100 L were obtained at the points to measure of radiocaesium concentration.
Suspended and dissolved caesium were collected separately from the river water. Their concentrations
were measured using a germanium semiconductor detector. To determine the radiocaesium
concentration, we used gamma-ray spectrometry with a germanium semiconductor detector, one of aseries of measurements established by the Ministry of Education, Culture, Sports, Science andTechnology.
Based on the monitoring data, we applied the Time-dependent One-dimensional Degradation And
Migration (TODAM) model for the verification of radiocaesium dynamics in the Hirose River. The
TODAM model can simulate temporal changes in radionuclides in waters and sediments. For example,
the TODAM model enables us to estimate the amounts of radionuclides transported to the Pacific Ocean
via rivers, to predict the places in rivers which sediments deposited frequently, and evaluate the effects
of decontamination within basins on the amounts of sediment discharge. In this survey, we used the
TODAM model to estimate the amounts of radiocaesium transported during flood events, to predict theradiocaesium adsorbed by sediments is deposited, and to estimate the amount of radiocaesium from theHirose River to the Abukuma River.
Table 2: Major monitoring items.

Air dose rate

Cross-sectional diagram, latitude, longitude,and vegetation
Air dose rates at heights of 1 m and 1 cm

Consecutive monitoring

Water level and turbidity.

River Shape

Ordinary water level

Monitoring

Monitoring

Turbidity, suspended solids, pH, andradiocaesium concentrations (Cs-134 · Cs-137)
Particle size distribution, mineral composition,and radiocaesium concentrations
Discharge and velocity.

Water samplingRadiocaesium, Ca2+, and NH4+ concentrations

Water sampling
Soil sampling
Flooding event

Discharge and velocity.

(2) Wide-area river survey
From the fiscal year 2015, we performed a multipoint survey of the Abukuma River basin and eight4|
water systems in the Hamadori area. Figure 2(b) shows the positions and characteristics of themonitoring points. In survey (1) of the Hirose River, a single basin was investigated in detail. On theother hand, in this wide-area survey, many rivers were investigated continuously by the same method
to clarify long-term changes and relationships with the basin characteristics. This survey was acontinuation of a survey performed by Tsukuba University. Until the end of the fiscal year 2014, theuniversity performed a survey on consignment from the Ministry of Education, Culture, Sports, Scienceand Technology and Nuclear Regulatory Agency. This report also includes those past monitoring data.
At each monitoring point, we set a suspended sediment sampler to collect suspended sediments (SS),a water gauge to measure the water level, and a turbidimeter to measure the turbidity of river water. At
some points, however, we used the water-level telemetry data by Fukushima Prefecture or the Ministryof Land, Infrastructure, Transport and Tourism instead of installing a water gauge. Suspended sediments
captured in the samplers were collected every month or every several months. The samples were driedat 110 °C for 24 h, and the concentrations of the suspended caesium-134 and caesium-137 were
measured using a germanium semiconductor detector. The turbidity and water level were measured
every 10 min. We calculated SS concentrations [g/L] and flow rates [m3/s] by the generated calculation
using the appropriate formulas. For the suspended caesium-137 migration [Bq], we multiplied the SSconcentrations by the flow rate and by the caesium-137 concentration in the same period.

1.3. Results(1) Survey of the Hirose River basin

Figure 3 showed river bed cross sections and status photos at the monitoring points of the Ochiai
Bridge and the Mano Bridge on the Hirose River. Both points are about 24 km away from each other.
Although the water depth was comparable, the river width at the Mano Bridge including the floodplains
was about twice as long as that at the Ochiai Bridge. This result indicates that a lot of sediments
transported by the river have deposited on the floodplains.

Figure 3: The cross sections and site photographs at the monitoring points in the
Hirose River basin (ex. St. 3 Ochiai Bridge and St. 9 Mano Bridge).

|5During the monitoring period, it was sometimes observed disruptions of the riverbeds and banks
during some flood events and depositions of new sediments on the riverbed. However, the cross sectionsof riverbed at all monitoring points did not show any great change.
Table 3 shows the observed suspended and dissolved caesium-137 concentrations in the river waterat each monitoring point of the Hirose river basin in April 2016. The Kd values are also presented andwere defined as follows: (solid-liquid distribution coefficient (Kd) = suspended radiocaesium
concentration/dissolved radiocaesium concentration). The concentrations of both suspended anddissolved radiocaesium were high in the Oguni River, where radiocaesium deposition was greater thanthat at other monitoring points. The Kd value, that is the ratio of the radiocaesium concentrations
between the solid and liquid phases, varied between 105 to 106 at every point. These values were greaterthan those reported in Europe after the Chernobyl accident (8×103 to 4.2×105；Smith et al., 2005).

Table 3: Suspended and dissolved Cs-137 concentrations and Kd values at each monitoring point
within the Hirose River basin.
Suspended Cs-137

Dissolved Cs-137

Kd value[Bq/kg][mBq/L][L/kg]

St. 1

Upstream of Hirose River

4982

1.8

2.76×106

St. 2

Takane River

2889

3.0

9.62×105

St. 3

Ochiai Bridge

5012

3.7

1.34×106

St. 4

Nunokawa River

4385

1.3

3.44×106

St. 5

Takaisaku Bridge

3865

3.2

1.21×106

St. 6

Ishida River

3432

2.7

1.25×106

St. 7

Jizougawara Bridge

5626

2.8

2.01×106

St. 8

Oguni River

11790

15.7

7.50×105

St. 9

Mano Bridge

3210

2.7

1.21×106

Figure 4 shows the changes in suspended caesium-137 and suspended solid (SS) concentrations at
each monitoring point along the Hirose River at the ordinary water level. The suspended caesium-137
concentration was high in the some of the tributaries, as mentioned above. This parameter is greatly
affected by the initial deposition in thee basins. The results varied among monitoring points, probably
owing to river wall construction. This is supported by the higher SS concentrations in the river waterdespite the ordinary water level.

6|

Figure 4: Suspended and dissolved Cs-137, and SS concentrations at each monitoring
point.

The TODAM model was provided by Prof. Yasuo Onishi, an IAEA specialist, in fiscal year 2015.
Figure 5 shows a schematic of the monitoring network used to apply the TODAM model to the Hirose
River. The distance was assumed to be 31,732 m from the mouth of the Hirose River, where it merges
with the Abukuma River, to the point where the Takane River and the Hirose River merge. We included
the inflows from the Takane River, Nuno River, Ishida River, and Oguni River, which are main
tributaries of the Hirose River in the simulation. For the Hirose River, the simulation was performed
every 200 mm in the flow channel direction, and 150 calculation points were set in the Hirose Riverbasin.
We simulated the radiocaesium dynamics in the Hirose River based on the monitoring data. For thissimulation, we received technical supports from Prof. Onishi. Figure 6 shows a simulation result, thatis, radiocaesium concentrations by the TODAM model. The ordinary water level and flow rate
conditions were set for the simulation, and measured radiocaesium concentration at the upstream end(St.1) of the main stream of the Hirose River and the main tributary were set as boundary conditions.

|7
Near the downstream end (St. 9), the measured and estimated values differed slightly. However,concentration changes at each monitoring point along the Hirose River could be roughly reproduced.

Figure 5: A schematic representation of the monitoring network in the Hirose
River basin.

Figure 6: A result of simulation by TODAM model.

(2) Wide-area river survey
Figure 7 showed caesium-137 concentrations in the Abukuma River system and rivers in the
Hamadori area until May 2017. Variation in the concentrations can be explained by differences in theinitial caesium-137 deposition among the basins. However, significant decreasing trends in the caesium137 concentrations were commonly observed at all monitoring points for about one year after theaccident. The rate of decrease slowed slightly thereafter, but this general trend has continued to thepresent time. The Nuclear Regulatory Agency indicated that differences in the rate of decrease in the8|caesium-137 concentration result from variation in land use types among the basins2).

Figure 7: Changes in suspended Cs-137 concentrations in river waters.
(a) Abukuma River system and (b) rivers in the Hamadori area.

Figure 8 shows the monthly changes in suspended caesium-137 at six monitoring points from 2011
to August 2015 (flux at each monitoring point). These amounts did not show a clear trend owing to theextensive temporal variation in river flow and SS concentrations. The ratio of the integrated suspended
caesium-137 migration amount to the amount of caesium-137 deposited in the basin at each point (basin
area × the initial caesium-137 deposition) was 2.7% to 3.4% at two points along the Abukuma River,and 0.7% to 1.4% at four points along its tributaries.
Figure 9 showed the suspended caesium-137 migration standardized by both the initial amount of
caesium-137 deposition and river flow (upper graph) and the proportion of the watersheds of a dam tothe total area (excluding No.12, 17, 18 due to several problems during the monitoring period. lower
graph) from October 2012 to October 2014. Small caesium-137 migrations were detected at the points
where the watershed area of the dam was occupied most area of the basin (red hatched part in the graph).

|9Figure 8: Monthly migration of the suspended Cs-137 at monitoring points (No.1-6)
from May 2011 to September 2015.

Figure 9: Migration of the suspended Cs-137 from Oct. 2012 to Oct. 2014. Red
shadow bars indicate the monitoring point with higher proportion of the watershedarea for dams to the total basin area.

10 |Finally, we evaluated the effects of surface decontamination practices by the national and municipal
governments on caesium-137 concentrations in the river waters. Because the observed decreases incaesium-137 concentrations, as shown in Figure 7, were similar to the trends observed in European
rivers after the Chernobyl accident, this decline is expected to result from the natural attenuation
process1). It is difficult to determine the effect of surface decontamination practices on the caesium-137
concentrations in rivers owing to the extremely small area subjected to decontamination relative to thetotal basin area. Thus, at two monitoring points in the Kuchibuto River basin (No.1 and 2. Fig. 2), we
investigated the relationship between the progress in surface decontamination and the concentrations of
the suspended caesium-137 in river waters (Fig. 10). The effects are expected to be pronounced at thosepoints because the basin was entirely within the special decontamination area. The intensive surface
decontamination practices were conducted in the area from Apr. 2014 to Dec. 2015. During this period,
the suspended caesium-137 concentrations at both points were decreased substantially. The rapid
decrease can be attributed to surface decontamination because the observed changes exceed those thatcan be explained by natural attenuation (Fig. 10).

Figure 10: Suspended Cs-137 concentrations at the monitoring points in the special
decontamination area (No.1 and 2) and outside the area (No. 6). The effective
ecological half-lives are also shown3).
Blue bars indicate the progression of the surface decontamination for farmlands after Apr.
2014.

1.4. Conclusions
We conducted continuous monitoring and applied the TODAM model to the Hirose River basin to
investigate the dynamics of radiocaesium. The simulation was able to roughly reproduce the actual changes
in radiocaesium at each monitoring point with the river flow. Further studies are needed to improve theprediction accuracy by continuous monitoring and the re-evaluation of the effects of high initial| 11radiocaesium amounts in the Oguni River basin.
The suspended radiocaesium concentrations showed decreasing trends over time in the Abukuma Riversystems and major rivers in the Hamadori area in the wide-area multipoint survey. In addition, it was
shown the reduction of radiocaesium migration at points with watersheds including dams therein.
Furthermore, effects of surface decontamination were detected at some monitoring points. Continuous
monitoring and subsequent assessments are important owing to potential changes in radiocaesium
concentrations in river waters in response to various processes, such as the recovery of vegetation andresumption of agricultural practices. Accordingly, we will continue to provide information for the safe andsecure use of water by the residents in Fukushima Prefecture.

References
1) Smith, J.T., Voitsekhovitch, O. V., Konoplev, A. V., Kudelsky, A. V., 2005. Radioactivity in aquatic
systems, in: Smith, J.T., Beresford, N.A. (Eds.), Chelnobyl - Catastrophe and Consequences. Praxis
Pablishing, pp. 139–190.
2) The Nuclear Regulatory Agency (2015), Fiscal 2014 Project Report about Integration of Radioactive
Material Distribution Data and Development of Migration Model Accompanying Disaster at Tokyo
Electric Power's Fukushima Daiichi Nuclear Power Plant - Part 2 "Radiocaesium migration status survey
on river water systems" at http://radioactivity.nsr.go.jp/ja/list/560/list-1.html
3) Pröhl, G., Ehlken, S., Fiedler, I. G. Kirchner, G. Klemt, E. Zibold G. (2006). Ecological half-lives of 90Sr
and 137Cs in terrestrial and aquatic ecosystems, Journal of Environmental Radioactivity, 91(1–2), 41-72.

12 |2. FIP2: Survey of radionuclide movement with wild life
Abstract
To understand radionuclide behavior in the ecosystem, Fukushima Prefecture is conducting survey andresearch on radionuclide migration in wild animals that are part of the ecosystem. Radiocaesium
concentrations in wild animals will be measured to investigate changes with the passage of time anddifferences between species.
We also investigated the behaviors of wild animals because radionuclide behavior in wild animals is
considered to be closely related to the behaviors of the animals.

2.1. Purpose
The accident at Tokyo Electric Power's Fukushima Daiichi Nuclear Power Plant caused wide-area
environmental contamination with radioactive materials. Radionuclides were detected in many wild
animals inhabiting the natural environment because they took radioactive materials from the naturalenvironment through food.
Since 2011 immediately after the accident, Fukushima Prefecture has been monitoring radionuclide
concentrations in the muscles of wild animals that are possibly hunted for consumption to contribute thesafe and secure of prefectural residents. As a result, caesium-134 and caesium-137 were mainly detectedin the muscles of wild animals as artificial gamma-ray emitting nuclides. However, there were not enoughinformation as regards radiocaesium migration from the ecosystem to wild animals. This is why we started
investigation and research into the dynamics of radiocaesium in the ecosystem to understand theimplications for the lifting of restrictions, and make prefectural residents feel safe. The behaviors and food
habits of wild animals are considered to have a close relationship with radiocaesium migration to thoseanimals. However, much is still unknown about the ecology of wild animals, such as behaviors and dietary
habits. In particular, almost no research has been carried out about the behaviors of wild animals in areas
evacuated by residents because of the evacuation order. Therefore, we carried out a home range survey aspart of a series of surveys to clarify the ecology of wild animals.

2.2. Content of implementation
We selected wild boars which inhabit wide areas of the prefecture as the main subjects of this research,
because even studies assessing the impact of the Chernobyl disaster did not show any clear tendency of
decrease in the time-series changes of radiocaesium taken into living things.

(1) Radionuclide dynamics in wild animals
A. Measurement of gamma-ray emitting radionuclide concentrations in wild animals
We measured gamma-ray emitting nuclides (wet weight) contained in the muscles of game species(wild boars, Asian black bear, copper pheasant, green pheasant, spot-billed duck, and mallard)
captured by nuisance kill or by hunting. Figure 1 shows the measuring procedure. By using themeasurement result, we investigated the dispersion of caesium-137 contained in the muscles of wild

| 13boars and other animals between individuals, and the tendency of fluctuation with the passage of timeafter the accident. We also measured gamma-ray emitting radionuclide concentrations in stomach
contents and of various organs in the same way to check radionuclide distributions in wild boars.
We checked the caesium-137 soil ground deposition at the capture points of target wild animals
from their capture information, and analyzed relationships between caesium-137 soil grounddeposition and caesium-137 concentration in muscle. As to the soil ground deposition, we used theresults of UAV surveys carried out by the Japan Atomic Energy Agency.

Example of sample (Muscle)

Cell U-8

Measurement of radionuclide concentration(Germanium semiconductor detector)

Figure 1: Measurement of radionuclides in wild animals.
B. Radionuclide migration from the environment into wild animals
To investigate the effect of foods on caesium-137 concentrations in the muscles of wild animals,
we measured caesium-137 concentrations in the stomach contents of wild boars captured in
Nihonmatsu City from fiscal 2013 to 2015. Then, we investigated relationships between caesium137 concentrations in stomach contents and in the muscles of the same individuals.
C. Physicochemical fractions of radiocaesium in stomach contents
There are three physicochemical fractionsof radiocaesium in soil (Figure 2). In the caseof plants, they mainly absorb radiocaesium of
exchangeable fractions. However, for plants,
radiocaesium of strongly bound fraction likeas strongly bound clay ores is difficult toabsorb. In the case of wild boar, it is thoughtthat they are considered to take in soil wheneating foods or gaining minerals intentionally.

Soil
Figure 2: Physicochemical fractions ofradiocaesium in soil.
Exchangeable fraction: Comparatively, easily to elute.
Organic matter bound fraction: Coupled with organic
matter.
Strongly bound fraction: Exist in soil particle.

Because of soil intake and the influence ofphysicochemical fractions of radiocaesium in soil, there is also possibility that caesium-137
concentration in the muscles of boars is higher than those in other wildlife. However, it is muchremains unknown about amounts of absorption and migration of caesium-137 from soil and foods
eaten by boar into their bodies.
In this study, we focus on about concentrations and ratios of physicochemical fractions of caesium137 in stomach contents, and research about relationships between physicochemical fractions of14 |caesium-137 in stomach contents and migration into their body.
The physicochemical fractions of radiocaesium is related to the absorption of the radiocaesium
from soil to plants. Collaborate with the Institute of Environmental Radioactivity at Fukushima
University, we are verifying the possibility that the physicochemical fractions of radiocaesium instomach contents affects radiocaesium migration into wild boars.

(2) Investigating the home ranges of wild animals
We attached GPS data loggers (hereinafter, GPS collars) (Figure 3) to wild boars and investigatedtheir behaviors. We set the GPS fix schedule of GPS collars as 1 GPS fix / 15 minutes, and recorded
wild boar behaviors for more than one month. We investigated wild boar behaviors inside and outside
the evacuation order zone (Figure 4).

Figure 3: GPS collar.

Figure 4: Attaching a GPS collar to an anethesized wild boar
captured with the cooperation of a harmful bird and animal
capture team.

2.3. Results(1) Dynamics of radionuclides in wild animals

Figure 5: Results of monitoring caesium-137 concentration in wild boar muscles.
The X-axis indicates wild boar capture timing, and the Y-axis indicates logarithmically transformed
caesium-137 concentration. The black dots indicate the measured values for individuals. The bar
graph shows the geometric mean value of caesium-137 concentration in each year. Each box indicatesthe reliability section from 75% at the top and 25% at the bottom. The bars indicate the maximum andminimum values (Annual change: May 2011 to March 2017).

| 15
A. Results of measuring gamma-ray emitting radionuclide concentrations in wild animals
Figure 5 shows the caesium-137 concentration in the muscles of wild boars captured throughout
Fukushima Prefecture from May 2011 until March 2017.
From figure 5, Any clear tendency was not shown because the dispersion between individuals was
great.
For comparison with wild boars
captured in Fukushima Prefecture,
we investigated the annual changesof radiocaesium concentrations inwild boars captured in Europe after
the Chernobyl disaster. Figure 6
shows the case of Regensburg inSouth Germany (Semizhon et al.
2009). Also in the case ofRegensburg,

caesium-137(Semizhon et al. 2009)

Figure 6: Temporal trends of caesium-137 in themuscle of boars (Regensburg, Southern Germany).

concentration varied greatly between individuals and did not show any clear tendency of decrease.
Since wild boars in Fukushima Prefecture also showed a similar tendency, we should monitor thecontamination trends in wild boars captured in Fukushima Prefecture.
Figure 7 shows caesium-137 concentrations in the muscles of Asian black bears that inhabit theforest ecosystem like wild boars. In Asian black bears, caesium-137 concentrations decreased withthe passage of years. This indicates that the annual change of caesium-137 concentration in muscles
differs depending on the animal species.

Figure 7: Results of monitoring caesium-137 concentration in Asian black bear muscles.
The X-axis indicates Asian black bear capture timing, and the Y-axis indicates logarithmicallytransformed caesium-137 concentration. The black dots indicate the measured values for individuals.
The bar graph shows the geometric mean value of caesium-137 concentration in each year. Each box
indicates the reliability section from 75% at the top and 25% at the bottom. The bars indicate themaximum and minimum values (Annual change: May 2011 to March 2017).

16 |Figure 8 shows relationships between caesium-137 soil ground deposition at the wild boar andAsian black bear capture points, and caesium-137 concentrations in muscles. Both wild boars andAsian black bears showed positive relationships between caesium-137 soil ground deposition at thecapture points and caesium-137 concentrations in muscles. Wild boars and Asian black bears
captured at points of greater caesium-137 in-soil deposition amounts showed higher caesium-137
concentrations in muscles. From the regression line in the figure, wild boars showed higher
concentrations in muscles than Asian black bears captured at points of the same soil grounddeposition.

Figure 8: Relationships between caesium-137 concentrations in Asian
black bear and wild boar muscles, and the amount of caesium-137
deposition to soil at the capture points.

Figure 9 shows wild boar and Asian black bear monitoring results by coloring depending on thearea of capture. Individuals with high caesium-137 concentrations in muscles were frequently
captured in the Hamadori region where the caesium-137 soil ground deposition is comparatively
great. Individuals with low caesium-137 concentrations in muscles were frequently captured in the
Aizu region where the caesium-137 soil ground deposition is comparatively small.
It has also been confirmed with birds that caesium-137 concentration in muscles differs between
species.
Figure 10 shows caesium-137 concentrations in the muscles of copper pheasant, green pheasant,spot-billed duck, and mallard captured in the period from October 2011 until February 2017.
Consider of the including of N.D. values, the caesium-137 concentration in muscles were higher
in copper pheasant that is not a migratory bird and inhabits a forest ecosystem than in the otherspecies.

| 17

Figure 9: Monitoring results of caesium-137 concentration in the muscles of wild boars
and Asian black bear (by the captured area).
The X-axis indicate the capture timing of wild boar and black bear and the Y-axis indicateslogarithmically transformed caesium-137 concentration. The dots indicate the measured value
for individuals that captured Hamadori (red dot), Nakadori (yellow dot), and Aizu (green dot).
(Annual change: May 2011 to March 2017)

18 |Figure 10: Results of monitoring caesium-137 concentration in muscle
of copper pheasants, green pheasants, spot-billed duck, and mallard(Data period: October 2011 to February 2017). N.D., not detected
Figure 11 shows the temporal change of caesium-137 concentration in muscle about copper
pheasant and green pheasant. Caesium-137 concentration in muscle decreased gradually in thegreen pheasant, but no clear trend was observed in the copper pheasant because of great dispersion
between individuals like wild boars. The reason for the difference between species is probably
because of difference of food habitat and/or the condition of the accumulation of radionuclides intheir environmental habitat; copper pheasant mainly inhabits forests, while pheasant mainly
inhabits the Satoyama ecosystem.

Figure 11: Changes caesium-137 concentrations in muscle of copper
pheasant and green pheasant.

| 19
B. Radionuclide migration from the environment
into wild animals
Figure 12 shows relationships between
caesium-137 concentrations in the muscles andstomach contents of the same wild boars. The
caesium-137 concentrations in the muscles andstomach contents showed positive relationships.
These relationships indicate the strong effect ofintake of caesium-137 such as food item andsoil on caesium-137 concentrations in wildboars.
According to research on the impact of theChernobyl disaster, caesium-137 concentrationsin the muscles of wild animals vary with the

Figure 12: Relationship between caesium-137
concentration in muscle and in stomach
contents of wild boar.

seasons because of such biological factors as
food habits and habitat use. Thus, we analyzed relationships between caesium-137 concentrations in
the muscles of wild boars and Asian black bears, and the months in which the animals were captured.
Figure 13 shows the results.

Figure 13: Seasonal variation of caesium-137 concentration in wild boar andAsian black bear muscles.
Both species of wild boar and Asian black bear showed seasonal variation of caesium-137
concentration in muscles. However, the variation pattern differs between the species. Caesium-137
concentrations in the muscles of wild boars were low in May to August, and high in November toMarch. Caesium-137 concentrations in the muscles of Asian black bears decreased from May to
September, then increased until January.

20 |C. Physicochemical fractions of radiocaesium contained in stomach contents
Figure 14 shows correlations between caesium-137 concentrations in muscles of wild boars
captured in the prefecture in 2015, and caesium-137 concentrations of each fraction in stomach
contents. Caesium-137 concentrations in muscles showed significant correlations with concentrations
in exchangeable fractions, and concentrations summed of exchangeable fractions and organic matterbound fractions in the stomach contents. However, caesium-137 concentrations in muscles did notshow significant correlations with concentrations of strongly bound fractions. Therefore, there is apossibility that exchangeable fractions and organic matter-bound fractions contained in ingestingfood item and soil are strongly related to caesium-137 migration into the bodies of wild boars.

Figure 14: Correlations of caesium-137 concentration from fractions between wild boar
muscles and stomach contents.

(2) Investigating the home ranges of wild animals
We tracked behaviors by using a GPS collar, and could define a home range as shown in Figure 15.
The home range was separated into core area of high point concentration (area containing almost 95%
of points by concentration analysis), and a roaming area containing all points (outermost area). This
individual had two core area. The total area was about 37 ha and the home range area was 244 ha.

| 21

Figure 15: Example of sample structure of home range area.
We carried out wild boar home range surveys in Fukushima City and Tazawa, Iwashiro-chiku,
Nihonmatsu City outside the evacuation order zone. Figure 16 shows the survey results on the samescale(one-kilometer mesh in the figure). Fukushima City has urban and suburban environments, while
Tazawa, Iwashiro-chiku, Nihonmatsu City is located between plains and mountains. The wild boars
surveyed on this occasion had core area of about 20 to 50 ha and home ranges of about 100 to 250 ha.

Figure 16: Size of wild boar home range outside the evacuation order zone.
We investigated wild boar home ranges in Tomioka-town, inside the evacuation order zone, to see
how the ranges would change if human activities became weak. Figure 17 shows the core area and homerange areas of individuals tracked inside and outside the evacuation order zone. No. 50, 85, and 208 arein the evacuation order zone. No. 52 and 58 are in an environment around cities without the evacuation
order zone. No. 66 and 67 are in mountainous areas outside the evacuation order zone. They seem to bereceiving damage control pressure. In the current survey, the number of samples is small and the sex,
weight and duration of GPS collar attachment differ between individuals (Table 1). Therefore, humanpressure increases seem to be reducing the home ranges.

22 |Figure 17: Comparison of home range and core area.

Table 1: Sexes, weights, and numbers of days with GPS collar
ID

No. 50No. 85

No. 208

No. 52

No. 58

No. 66

No. 67

Sex

♂

♀

♀

♂

♂

♀

♀

Weight
（kg）

37

48

51

44

70

35

37

81

99

117

99

50

110

34

Numbers ofdays withGPS collar

Wild boar home ranges may change dependingon the timing of survey. Therefore, we compared
the home range sizes of eight individuals whose
data could be acquired for one month or longer in
November to December (winter), and January to
February (the breeding season). Although thenumber of samples was small, the home ranges
tended to be larger inside the evacuation orderzone than outside (Figure 18).
We investigated habitat type in the home ranges
of individuals. In home ranges of individuals at
inside the evacuation order zone, farmland
occupied a high percentage. It suggested that the

Figure 18: Average of home range size of wildboars inside and outside the evacuation zone.
The error bars indicate the minimum andmaximum values.

home ranges of individuals in inside theevacuation order zone tended to extend to farmland (Figure 19).

| 23

Figure 19: Ratio of land use in the home ranges of wild boars inside and outside
the evacuation order zone (each bar indicates the value for an individual).

2.4. Conclusions① When caesium-137 concentrations in the muscles of wild boars and Asian black bears were compared,
wild boars showed higher concentrations. When copper pheasant and green pheasant were compared,
copper pheasant showed high concentrations. The tendency differed between species.
② Caesium-137 concentrations in the muscles of wild boars were found to have been strongly affected byfood habits. Both wild boars and Asian black bear showed high concentrations in winter although theirvariation patterns were different.
③ Compared with wild boars outside the evacuation order zone, individuals inhabiting inside theevacuation order zone tend to have larger home ranges and shifted to farmland.
From ① and ② above, food habits greatly affect caesium-137 migration from the environment towild animals. In Europe, high radiocaesium concentrations in the muscles of wild boars is considered
attributable to the foraging of Deer Truffle that is a kind of mushroom. However, the compositional
analysis of wild boar stomach contents in Fukushima Prefecture has not yet shown any mushroom pieces.
When a kind of wild mushroom called Koutake was fed to captured wild boars, some of the boars ate themushroom, but not decisively. Since it is necessary to know the detailed food habits of wild boars inFukushima Prefecture and cesium concentrations in foods, we started studying foraging behaviors by using
GPS collars with cameras, and food habits by DNA analysis of wild boar stomach contents. We are also
proceeding with the detailed analysis of the physicochemical fractions of caesium-137 in foods because
they may affect caesium-137 absorption from foods into the body. We will conduct these investigations on
animals of other species, particularly Asian black bears inhabiting the same forest ecosystem as wild boars,
and compare the acquired data with those of wild boars. These investigations will clarify the mechanismof radiocaesium migration from the environment into wild animals. They will also clarify why caesium137 concentrations are higher in the muscles of wild boars than in those of other wild animals, and why
radiocaesium concentrations in muscles differ between species.
Wild boar home ranges showed the tendency of ③ above but the number of surveyed individuals was
small. In addition to the above food habits survey, we are continuing the home range survey to know the24 |behavioral characteristics of wild boars in more detail. The findings and survey techniques regarding the
behavior of wild boars obtained this time will be applied to ways of dealing with wild animals in
evacuation order-lifted areas where residents have begun to return.
We will keep monitoring the transitions of radiocaesium concentrations in the bodies of wild boars andother animals to study the prediction of fluctuation tendency. As to some species showing in-muscle
caesium-137 concentration decrease, we will study survey methods to discuss the lifting of shipping andintake restrictions.

| 25

3. FIP3: Countermeasures for radioactive materials in rivers and lakes
Abstract
We synthesised findings concerning the behaviour of and countermeasures against radiocaesium in rivers
and lakes. We devised a decontamination measure for radiocaesium in riversides and verified its effectivenessand sustainability. In addition, we investigated the contamination state of public sites in Fukushima
prefectural riversides and discussed suitable measures to address contamination.

3.1. Purpose
The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident of Tokyo Electric Power Company
emitted radioactive materials (particularly radiocaesium) into the environment. This disturbed the use andmanagement of rivers and lakes and caused public anxiety. Governments and research institutions havemonitored water, sediments, and fishery products, investigated the behaviour of radioactive materials, anddevised countermeasures. In this project, we selected suitable countermeasures against radiocaesium inFukushima Prefecture by organizing results obtained worldwide. We also performed a decontamination
test at a riverside; this method has been not established previously, and accordingly we verified its
effectiveness and sustainability. We investigated the contamination state of riverside parks in Fukushima
Prefecture and discussed appropriate countermeasures.

3.2. Content of Implementation(1) Selection of suitable measures against radiocaesium in Fukushima Prefecture
We organized suitable countermeasures against contamination in rivers and lakes after the Fukushima
nuclear accident.

(2) Riverside decontamination and the sustainability of its effectA. Purpose
Countermeasures against external exposure at riversides, particularly decontamination strategies,
have not been established. Rivers are a major transport route for radiocaesium, and sediments withradiocaesium are frequently and heavily deposited onto riversides. Soil decontamination methods infarmland, forest, and residential areas are based on the assumption that radiocaesium is distributed
within a depth of several centimeters, and thus these methods may be unsuitable for riversides. We
tested a sediment removal method that considers the spatial distribution of radiocaesium in riversides
and investigated the sustainability of the effect for 2 years after decontamination. The following
results have been published, in part, by Nishikiori and Suzuki.1)
B. Methods
The test site was located 55 km northwest of FDNPP and at the lower part of the Kami-Oguni
River (Figure 1a, 1b), a tributary of the Abukuma River (Figure 1a, 1b). The total deposition densityof caesium-134 and caesium-137 was 300–600 kBq/m2. Most of the watershed is covered with forests,

26 |and agricultural land and residential land are found along the river (Figure 1b). The test site consistedof a river bank, which is approximately 170 in length and 2–6 m in width, and the total width of theriver and banks was 15 m on average (Figures 1c, 1d). The left bank, right bank, and flood channel
were used as a school route, an orchard, and a place for outdoor education, respectively. The schoolroute on the left bank was decontaminated before this experiment.

Figure 1: Outline of test site.
Radiocaesium deposition densities (decay correction date: July 2, 2011) were obtained fromthe third airborne monitoring survey data.2)
Figure 2 shows the test procedures. The air dose rates at a height of 1 m were measured using a
NaI scintillation survey meter before decontamination and for 2 years after decontamination.
Sediments in the flood channel and in the river bed were collected just before and for 2 years after
decontamination. The radiocaesium concentration and weight of the mud fraction (silt and clay) were
measured for sediment samples after gravel was removed.
Additional annual external exposure doses before and after decontamination were estimated bymultiplying the time spent on the dikes and the flood channel and the average air dose rates at a heightof 100 cm on the left dike and the flood channel. A value of 0.04 mSv/h measured before theaccident3) was subtracted from the average air dose rates to account for natural background levels.
The durations were 35 h per year for commuting (10 min per day, 210 days per year) and 24 h foroutdoor education (2 h per day, 12 days per year).

| 27

Figure 2: Photographs of the decontamination test procedures.

(3) Investigation of contamination in riverside parks and the selection of countermeasures
A. Purpose
As mentioned above, radiocaesium frequently accumulates on riversides via sediment deposition.
The upstream areas of the coastal region in Fukushima Prefecture were heavily contaminated, andthe downstream riversides are likely contaminated to a greater extent than the surrounding area.
Therefore, we investigated the contamination condition of riverside parks in the coastal region anddiscuss countermeasures.
B. Methods
We investigated two downstream points along the Niida River in the coastal region (Figure 3).
Park A is located along the main stream of the Niida River, and park B is located along the Mizunashi
River, a tributary of the Niida River. A dam is located 5 km upstream of park B. The total deposition
density of caesium-134 and caesium-137 was greater than 1000 kBq/m2 in the upstream area but lessthan 100 kBq/m2 in the most downstream area. The deposition densities were 490 and 210 kBq/m2
in parks A and B, respectively.4) The area of parks A and B are 2.7 and 1.6 ha, respectively.

28 |In August 2015, the air dose rate was measured 1 m above the ground using a portable gammaray-measuring device (Gamma Plotter H, Japan Radiation Engineering Co., Ltd.). A map of the air
dose rate was generated using Restoration Support System for Environment software [RESET](developed by the Japan Atomic Energy Agency).
Just after obtaining the measurements (6–11 September, 2015), an extreme flood inundated nearly
half the area of the parks. According to data obtained at an AMeDAS meteorological station located
6 km southeast of park A, the total precipitation during the period was 385.5 mm.5) The air dose rate
was measured again on September 28, 2015. The external exposure doses for activities in the parks,
such as recreation, walking, and maintaining flowerbeds, were also measured using a dose meter(DOSE e nano, Fuji Electric Co., Ltd.). The durations of the activities were assumed to be 36 h peryear (park A, 12 h per year for recreation, 12 h per year for walking, and 12 h per year for maintaining
flowerbeds; park B, 24 h per year for recreation and 12 h per year for walking). Soil was sampled toinvestigate the radiocaesium distribution in the parks.

Figure 3: Location of study sites. Radiocaesium deposition densities.
(decay correction date: July 2, 2011) were obtained from the third airborne monitoring
survey data.2)(4) Interview survey on issues related to the water environment and investigation of temporal trends
A. Purpose
Five years have passed since the FDNPP accident. To evaluate medium- and long-term
countermeasures, it is necessary to understand the major issues related to the water environment inFukushima Prefecture and their temporal trends. The aims of this study are were to clarify these issues
by conducting interviews with parties interested in the water environment and to elucidate thetemporal changes in the view of Fukushima prefectural residents regarding the safety of the water
environment based on an annual public opinion survey.

| 29
B. Methods
We conducted interviews about issues related to radioactive materials in the water environment
with Fukushima governmental staff involved in water use measures and synthesized these issues. A
public opinion survey on prefectural policies is conducted every year by the Fukushima Prefecture
government to investigate the awareness and needs of residents as a basis for policy on
countermeasures.6) We obtained the raw data from the survey for 2010 to 2015. In the public opinion
survey, the following questions were used for the analysis: "Do you feel that your living environmentis safe from environmental pollution including water and air pollution? (safety view on the water andair environments)" and "Is your living space secure from radiation? (low anxiety about radiation
risks)". We analyzed temporal changes in the view of the safety of the water and air environmentswith respect to sex, age, and living region. We also investigated the relationship between the view ofsafety regarding the water and air environments and the low anxiety about radiation risks.

3.3. Results(1) Selection of suitable measures against radiocaesium in Fukushima Prefecture
Issues and measures concerning the use of rivers and lakes were well organized in the guidelines
established by concerned ministries7),8) and in a report concerning the Chernobyl accident.9) Table 1
briefly lists the main points.
Table 1: Issues and measures for specific purposes in rivers and lakes.
Issue

Related media

MeasuresInternal exposure by drinking

Rivers and lakes

Changing water sources

Transfer from irrigation water toRivers and lakes

Reducing sediment inflow using silt fences

agricultural products and external
exposure during farming

Sediment deposition in dams
Irrigation ponds

Reducing sediment outflow using silt fences
Decontamination of bottom sedimentInternal exposure by consuming

Agricultural products

Potassium fertilization to suppress uptake

Rivers and lakes

Shipping restrictions

fishery products
External exposure by using

Potassium input (effective only in closed lakes)
Rivers and lakes

Use restriction and soil decontaminationwatersides

Removing riverbed sediments to reduce sediment(Parks, roads, residences, etc.)

deposition onto riversides
Embankment for inundation control

Common to all issues

Irrigation ponds

Use restriction, decontamination, and covering of(at drainage)

exposed bottom sediments
Source decontamination and sediment discharge
prevention
Risk communication to reduce anxiety about use

30 |(2) Riverside decontamination and the sustainability of its effectFigure 4 shows the vertical distribution of radiocaesium concentrations in flood channel sediments
before decontamination. The caesium-134 concentration was several kBq/kg because 3.5 years had
passed since the FDNPP accident. However, at points 1 and 2, the caesium-137 concentration exceeded
10 kBq/kg, even at layers deeper than 10 cm. The layers had a high percentage of mud fraction (39% to56%). Since radiocaesium has strong adsorption properties in clay and silt10), radiocaesium in layersrich in mud are unlikely to migrate into underlying layers. Therefore, the high level of radiocaesium inthe lower layer was likely caused by sediment deposition. In contrast, the radiocaesium concentrations
were relatively low at points 3 to 5. We considered the heterogeneity in the vertical and horizontal
radiocaesium distributions and adjusted the removal depth of the flood channel sediment to 15 to 35 cm.
Since a similar depth distribution of radiocaesium has been reported for floodplains11),12), it is important
to investigate the depth distribution prior to riverside decontamination.

Figure 4: Vertical distribution of the radiocaesium concentration and the mud fraction inflood channel sediment.

Figure 5: Maps of the air dose rate 1 m above the ground before and after decontamination.

| 31
Figure 5 shows the air dose rate distribution before and after decontamination. The mean dose rate 1
m aboveground was 0.66 µSv/h (standard deviation, 0.22 µSv/h) before decontamination. The value
decreased by a factor of approximately two at the completion of decontamination to 0.34 µSv/h(standard deviation, 0.11 µSv/h), indicating that the method was effective.
Figure 6 shows the mean air dose rate for 2 years after decontamination. The values for the control
area 20 m upstream from the decontaminated area are also given. Four rainfall events of ≥50 mm wereobserved at AMeDAS Yanagawa station, 9 km north of the test site5), during the 2-years period after
decontamination, and accordingly the flood channel was likely inundated several times. However, theair dose rate gradually decreased, as in the control area. The caesium-137 concentrations in the top layer(a depth of 5 cm) of flood channel sediments were <3 kBq/kg at five points, shown in Figure 4. Thus,
the decontamination effect was maintained. The plant community in the flood channel was removed
after decontamination, and sediment deposition was likely difficult. It is necessary to investigate
whether the decontamination effect is maintained, even when the the plant community regrows.

Figure 6. Temporal change in the air dose rate at 1 meter above the ground.
Results are presented as means and standard deviations.
The additional annual external exposure doses during commuting and outdoor education at the testsite were estimated to be 0.029 and 0.016 mSv before and after decontamination, respectively. In KamiOguni and Shimo-Oguni Districts, similar to the area of our test watershed, annual external exposures
doses were determined for daily life based on glass dosimeter measurements. The average additional
external exposure during the period from July 2013 to June 2014 was 1.23 mSv.13) The dose during theactivities at the test site (commuting and outdoor education) accounted for only 2.3% and 1.3% of thetotal value before and after decontamination, respectively. As described in 3.3.(4), some Fukushima
Prefecture residents still feel anxiety about the water environment. Decontamination is one of thetangible measures described in Table 1. The effectiveness of intangible measures, such as risk
communication, should also be examined.

32 |(3) Investigation of contamination in riverside parks and the selection of countermeasures
Figure 7 shows maps of the air dose rate at 1 m above the ground in park A in August and September
2015 (before and after an extreme flood). Before the flood, a high air dose rate (≥1.0 µSv/h) was detectedin the riverside and the northeastern area. After the flood, however, the air dose rate dropped to <1.0
µSv/h in these areas. In park B, there were no significant differences before and after the flood (Figure
8).

Figure 7: Map of the air dose rate at 1 m above the ground in park A. The park is areasurrounded by a white line.

Figure 8: Map of the air dose rate at 1 m above the ground in park B. The park is areasurrounded by a white line.
Figure 9 shows the radiocaesium inventory and concentration in the soil of park A. The total inventory
to the sampled depth was 200 to 400 kBq/m2 at the lawn and the flowerbed and was approximately 2400

| 33
kBq/m2 at the riverside (i.e., approximately 10-fold greater than observed at the lawn and the flowerbed).
The high air dose rate at the riverside before the flood likely reflected this radiocaesium distribution.
For the caesium-137 vertical distribution, the concentration was high only at a depth of several
centimeters at the lawn, and it was low and uniform to a depth of 15 cm at the flowerbed due to tilling.
At the riverside, the concentration was low to a depth of 25 to 30 cm, and the peak was observed at
depth of about 40 to 50 cm. When observing the soil profile at point 3, the color and particle size of thesediment clearly changed at a depth of around 30 cm. Thus, the upper 30 cm of the sediment was likely
deposited during the flood in September 2015. The drop in the air dose rate after the flood probably
reflected this deposition of sediment with the low concentration and erosion at the northeastern part ofthe park (Figure 7). In the Niida River watershed, it was reported that this extreme flood caused severe
erosion in the upstream area and the deposition of sediment with a low concentration in the downstream
area, leading to natural decontamination.14) Our study results in park A are consistent with this.

Figure 9: Vertical distribution of radiocaesium in the soil in park A. Samples werecollected after the extreme flood in September 2015.
In park B, the total inventory of caesium-137 was in the same range (130 to 220 kBq/m2) in areas
affected and unaffected by the extreme flood. Most caesium-137 was retained in the surface layers(Figure 10). This state shows little sediment deposition, and therefore shows no significant changes in
the air dose rate after the flood. The difference in sediment deposition and caesium-137 accumulationin these parks may be explained as follows. First, the riverside of park B was lawn, whereas that of park
A was covered with a plant community with a height of around 1 m. The plant community may favor
sediment deposition. Second, a dam in the upstream area of park B likely catches sediments and reduces

34 |the sediment supply to the park. Third, sediment with a high radiocaesium concentration is unlikely to
be transferred to park B because a heavily contaminated area (≥1000 kBq/m2) is located in the upstream
area of the dam (Figure 3).

Figure 10: Vertical distribution of radiocaesium in the soil in park B. Samples werecollected after the extreme flood in September 2015.
Additional annual external exposure doses during activities in parks A and B were estimated to be
0.018 mSv and 0.009 mSv, respectively. In the administrative district where the parks are located,
external exposure was determined for daily life based on glass dosimeter measurements. The additional
annual external exposure dose was 0.44 mSv (for a 3-month measurement period from July to
September 2015, the value quadrupled).15) The dose during the activities in the parks accounted for 2%
to 4% of the total value. Therefore, effect of decontamination on exposure reduction in the parks islimited. Considering the results obtained for the Kami-Oguni River, time spent at the riverside is usuallylimited, and natural decontamination occasionally occurs. Tangible countermeasures, such as
decontamination, are not necessarily suitable for the riverside. However, radiocaesium occasionallyaccumulates during small- and medium-scale floods in riversides, where sediments are easily depositedand the upstream area is heavily contaminated. The air dose rate may increase in these riversides.
Therefore, to effectively mitigate anxiety, continued monitoring and predictions of the contamination
state may be useful in the future.

(4) Interview survey on issues related to the water environment and investigation of temporal trends
The Fukushima Prefecture government indicated the following issues related to radioactive materials
in the water environment 5 years after the FDNPP accident:- interference with activities perforemed before the accident;- impact of radioactive materials on the future; and| 35- continuation of countermeasures.
We found that the recovery of the view of residents regarding the safety of the water and air
environments differed among regions, based on the public opinion survey results. The recovery was
slower in the Nakadori (central) and Hamadori (coastal) regions than in the Aizu (eastern) region (Figure11). The safety view was significantly associated with the perception of radiation risk.

Figure 11: Temporal changes in the response to the question "Do you feel that yourliving environment is safe from environmental pollution including water and air
pollution?". EOAs represents evacuation order areas.
3.4. Conclusions
In this project, we selected suitable countermeasures against radiocaesium in freshwater systems in
Fukushima Prefecture by reviewing findings obtained worldwide. We also performed a decontamination
test at a riverside, accounting for the spatial distribution of radiocaesium, and verified its effectiveness.
Although radiocaesium sometimes accumulates in downstream riversides, extreme floods act as natural
decontamination process. In addition, external exposure at riversides is limited. However, residents inheavily contaminated regions (e.g., the Hamadori region, including evacuation areas) have persistentanxiety regarding the water environment. For addressing anxiety, it is necessary to clarify the factors that
determine anxiety and discuss appropriate solutions.
Information about the main results of this project has been provided to relevant divisions of the
Fukushima Prefectural Government, and the riverside decontamination technique may be a general river
improvement strategy, as evidenced by the study results.

36 |References
1) Nishikiori, T., Suzuki, S. (2017) Radiocesium decontamination of a riverside in Fukushima, Japan.
Journal of Environmental Radioactivity, 177, 58-64.
2) Ministry of Education, Culture, Sports, Science and Technology (2011) Results of deposition ofradioactive cesium of the third airborne monitoring survey. http://emdb.jaea.go.jp/emdb/portals/b224/
3) Minato, S. (2006) Distribution of terrestrial γ ray dose rates in Japan. Journal of Geography, 115 (1), 8795.
4) Nuclear Regulation Authority (2017) Extension site of distribution map of radiation dose.
http://ramap.jmc.or.jp/map/
5) Japan Meteorological Agency (2017) Data and Material.
http://www.jma.go.jp/jma/menu/menureport.html.
6) Fukushima Prefectural Government (2017) Fukushima Prefectural Public Opinion Survey.
https://www.pref.fukushima.lg.jp/sec/01010e/koucho1-439.html.
7) Ministry of the Environment, Government of Japan (2014) Decontamination Guidelines, second ed.
https://josen.env.go.jp/material/
8) Ministry of Agriculture, Forestry and Fisheries (2015) Manual of countermeasure techniques against
radioactive materials in irrigation ponds.
9) IAEA (2006) Environmental consequences of the Chernobyl accident and their remediation: Twenty
years of experience report of the Chernobyl forum expert group ‘environment’. Vienna.
10) Nakao, A., Funakawa, S., Tsukada, H., Kosaki, T. (2012) The fate of caesium-137 in a soil environment
controlled by immobilization on clay minerals. SANSAI Environ. An Environmental Journal for the
Global Community, 6, 17-29.
11) Tanaka, K., Kondo, H., Sakaguchi, A., Takahashi, Y. (2015) Cumulative history recorded in the depth
distribution of radiocesium in sediments deposited on a sandbar. Journal of Environmental
Radioactivity, 150, 213-219.
12) Konoplev A., Golosov V., Wakiyama Y., Takase T., Yoschenko V., Yoshihara T., Parenyuk O., Cresswell
A., Ivanov M., Carradine M., Nanba K., Onda Y. (in press) Natural attenuation of Fukushima-derived
radiocesium in soils due to its vertical and lateral migration. Journal of Environmental Radioactivity.
doi:10.1016/j.jenvrad.2017.06.019.
13) Date City (2015) Reconstruction and recovery news at Date City, 22, 1-4.
http://www.city.date.fukushima.jp/soshiki/12/763.html
14) Konoplev, A., Golosov, V., Laptev, G., Nanba, K., Onda, Y., Takase, T., Wakiyama Y., Yoshimura, K.
(2016) Behavior of accidentally released radiocesium in soil–water environment: Looking at Fukushimafrom a Chernobyl perspective. Journal of environmental radioactivity, 151, 568-578.
15) Minami-Soma City (2016) Result of second measurement of individual cumulative dose in 2015 (Julyto September 2015). http://www.city.minamisoma.lg.jp/index.cfm/10,28438,61,367,html.

| 37

4. FIP4: Developing of environmental mapping technology using GPS walking surveys
Abstract

Fukushima Prefecture developed environmental mapping technology with GPS walking surveys as atool for surveying the regional distribution of air dose rates.
This report covers the results of parameter verification necessary for the development of thistechnology and the history of development.
4.1. Purpose

To understand the air dose rate (hereinafter simply referred to as the dose rate) in Fukushima
Prefecture after the accident at the Fukushima Daiichi Nuclear Power Plant, we have conducted fixedpoint measurements with monitoring posts and dose rate measurements in car-borne surveys using
the GPS-linked dose rate measurement device KURAMA (Kyoto University RAdiation MApping
System), and have provided information to prefecture residents on the prefecture homepage (Figure
1 and 2).
(b)(a)

Figure 1: Example of current monitoring.
(a): Example of a fixed-point measurement(using a real-time dose-rate measurement system)(b): Example of a car-borne survey (KURAMA-II installed on the back of a local bus)(a)Figure 2: Fukushima Prefecture radiation measurement map.
(http://fukushima-radioactivity.jp/pc/)(a): Example of a fixed-point measurement(b): Example of a traveling survey

(b)

38 |
As of March 2016, measurements are being made at 3500 fixed points with monitoring posts inFukushima Prefecture. Car-borne surveys using local buses are also being conducted with the purpose ofinterpolating the fixed-point measurements.
It is, however, difficult to conduct fixed-point measurements or car-borne surveys in some places,
including parks, forests, and alleys near residential areas, and dose rates sometimes differ between fixed
measuring points at the same facility or site (Figure 3). For these reasons, in addition to fixed-point
measurements and car-borne surveys, we require measurement technology with which to grasp a moredetailed distribution of dose rates, and we need to present the measurement results in a format that is easy
to understand.
Therefore, to employ interpolation to obtain dose rates for parks, forests, and alleys near residential
areas where fixed-point measurements and car-borne surveys are difficult, we developed environmental
mapping technology using GPS walking surveys together with unmanned aerial vehicles (UAVs)
developed by the IAEA.
The prefecture and IAEA have shared the development of environmental mapping technology with GPS
walking surveys (FIP4) and environmental mapping technology with unmanned aerial vehicles (FCP3),and by combining these technologies and visualizing measurement results, we were able to create dose
distribution maps that are more detailed and effective.

Figure 3: Measurement ranges of conventional measurement methods.

4.2. Content of implementation(1) Development of equipment
We used the KURAMA-II, which was developed by Kyoto University, for walking surveys, andassembled five pieces of equipment in a way suited to walking surveys (Figure 4). The orange
backpack contains a CsI (T1) scintillation detector, which is a low-dose-rate detector, and a high-| 39
precision GPS unit. The back packer measures the dose rate by walking on a transverse course whilemerging dose rate data from the low-dose CsI detector and position information from the highprecision GPS device.

(a)

(b)

Figure 4: Walking survey equipment.
(a): Appearance of the devices(b): Low-dose-rate CsI detector (Hamamatsu Photonics K.K. C12137-01) and highprecision GPS unit (SOKKIA GIR1600)
The measurement screen is shown in Figure 5. The measurement interval may be selected as 3 seconds,
5 seconds, and so on. At the start of the measurement, information such as the current position and dose
rate are recorded to a notebook computer, and the position information, dose rate, trends, and mapping
results are displayed on the computer screen.
Measurers can look at the screen to check the measurement position and dose rate while conducting
detailed measurements.

Figure 5: Display screen on a personal computer.

(2) Development of mapping technology using Geographic Information System (GIS)
We conducted a specification study and developed a GIS tool for capturing, combining, and mapping
the dose rate and position information gained from walking surveys and UAVs. An overview of the tool
is shown in Figure 6.

40 |Result of air-borne
survey by a UAVResult of walking
surveyGIS tool

Combined map

Figure 6: Overview of the GIS tool.

Figure 7: Data including the dose rate.

It is possible to produce a contour map using the GIS tool. Data in comma-separated-value format
recorded in walking surveys are converted to Microsoft Excel file format (Figure 7), and point data withdose rate information are created from the latitudinal and longitudinal information contained in the data
(Figure 8). With the GIS tool, it is possible to estimate the dose rate at unmeasured positions and to
produce contour maps from the point data created using any interpolation algorithm, such as Inverse
Distance Weighting (IDW) algorithm (Figure 9).

Figure 8: Map data and dose rate plotting.

Figure 9: Interpolated dose map.

(3) Walking survey implementation
We collected parameters necessary for walking surveys, and carried out the survey in several areas.

(4) Manual preparation
We created a manual surveying the walking survey method. Photos and sentences are combined inthis manual for easy understanding.

| 41
4.3. Results(1) Gathering parameters necessary for walking surveys
We conducted a field test of walking surveys, andgathered data for evaluation and analysis (Figure 10).
Data

were

gathered

to

check

the

direction

characteristics and appropriate measurement density, as
well as to determine correction factors.
A. Checking direction characteristics
Shielding from the measurers themselves affects
the contribution from the radiation source depending

Figure 10: View of a walking survey.

on the walking direction in walking surveys (Figure 11). Walking surveys were therefore conductedby changing the walking speed and by walking back and forth so as to straddle the radiation source
and check the effect of direction characteristics.
As a result, while shifts occurred in places where peaks appeared, they fell within a range of about
2 meters, and measurements showed that the maximum value of the dose rate was nearly the same
during forward and reverse passes (Figure 12). We also confirmed that reducing the walking speed
caused the peaks of the dose rate distribution to grow sharply (Figures 13 and 14).
Judging from the above result, the impact of directional characteristics on a measured value of awalk survey was considered small at a constant walking speed.
3

Direction A (slow)
Direction A (ordinary)dose rate [μSv/h]Direction A (fast)
Direction B (slow)

2

Direction B (ordinary)
Direction B (fast)

1

0
-20

-10

0

10

20

distance from radiation hotspot [m]Figure 11: Measurement of direction
characteristics.

Figure 12: Measurements after changing speed
and direction.

dose rate [μSv/h]4

survey metervery slow
slow
ordinary
fast

3
2
1
0
-20

-10

0

10

distance from radiation hotspot [m]Figure 13: Change in walking speed.

Figure 14: Change in measurements due towalking speed.

20

42 |
B. Determination of correction factors in a comparison test with survey meters
We assumed measurements made with a NaI (Tl) scintillation survey meter (TCS-172B) at a heightof 1m to be the most reliable, and the survey meter was calibrated with traceability. We comparedmeasurements made using a survey meter with those obtained in a walking survey (Figure 15). A
comparison was made at several points with differing dose rates. At each point, we faced north, south,
east, and west and made measurements five times in each direction to mitigate direction
characteristics. We then took the average value for all directions as the measurement for that point.
We next plotted the measurements of walking surveys against the survey meter to determine thecorrection factor.

(a)

(b)

Figure 15: Images of measuring.
(a): Measurement with a survey meter(b): Measurement with a walking survey
Both measurements were made facing four directions.
The results of the comparison are shown in Figure 16(a). There was good linearity between themeasurements of walking surveys and the survey meter below a survey meter measurement of 1
μSv/h, whereas the linearity deteriorated above approximately 1 μSv/h. This phenomenon is due tocount loss caused by excessive radiation incidence on the low-dose CsI detector.

(a)
NaI(Tl) Scintillation Survey meter[μSv/h]1.0
y = 1.3287x
R² = 0.9957

0.8

y = 0.9888x
R² = 0.9931

0.6

0.4

0.2

0.0
0.0

0.2

0.4

0.6

Walking Survey [μSv/h]

0.8

1.0

| 43

(b)
NaI(Tl) Scintillation Survey meter[μSv/h]20
y = 0.2553x2 + 1.0814x
R² = 0.9963
15
y = 1.1285x
R² = 0.9984

10

5

0
0

5

10

15

20

Walking Survey [μSv/h]

Figure 16: Comparison of measurements of the survey meter and walking survey.
(a): Chart plotting data below 1 μSv/h(b): Chart plotting all data
● Comparison of the measurements of the low-dose-rate CsI detector (Cs-137, 662keV measuring
range: 0.001 to 10 μSv/h) and NaI survey meter.
● Comparison of the measurements of the high-dose-rate CsI detector (Cs-137, 662keV measuring
range: 0.01 to 100 μSv/h) and NaI survey meter.
Note that the approximate curve is not affected by the self-dose from the measurement detector,
with the intercept being zero.
In light of the above results, we changed the detector to a high-dose-rate CsI detector (Figure 17)
and compared the results obtained using the survey meter with measurement results of walking
surveys again. The results are shown in Figure 16(b). We confirmed that as a result of changing thedetector, the linearity of walking survey measurements against survey meter measurements is
obtained even in the high dose range.
We also confirmed that the high-dose CsI detector can make better measurements than the lowdose rate CsI detector in the high dose range in field tests. This is also confirmed in Figure 18, whichshows the walking survey results having changed detectors at the same geographic point. The
maximum indicated value is higher for the high-dose-rate CsI detector than for the low-dose-rate CsI
detector, and the high-dose-rate area represented by red markers appears, indicating thatmeasurements are made without counting loss of radiation.

Figure17: High-dose CsI detector (Hamamatsu Photonics C12137).

44 |According to the above comparisons, we set the correction factor of walking surveys to 1.3 whenusing the low-dose-rate CsI detector at points with a dose rate less than 1 µSv/h and 1.1 when using
the high-dose-rate CsI detector.

(b)

(a)

Figure 18: Walking surveys having changed the detector.
(a): Walking survey with the low-dose-rate CsI detector.
The indicated value range is 2.77 to 5.99 μSv/h.
(b): Walking survey with the high-dose-rate CsI detector.
The indicated value range is 5.00 to 29.5 μSv/h.
C. Confirming variations in measurements
We conducted-fixed point measurements to confirm variations in measurements for a measurement
time of 3 seconds in the low dose rate range. Fixed-point measurements were made with both the
low-dose-rate CsI detector and the high-dose-rate CsI detector.
Results showed that the variation in measurement results was larger for the high-dose-rate CsI
detector at points with a low dose rate (Figure 19). The variation coefficient obtained from dividing
the standard deviation of measurements by the average value was 19.7% for the low-dose-rate CsI
detector but 42.7% for the high-dose-rate detector. Error in measurements made with the low-doserate

detector

was

small
0.12

rate achieved with the large

0.10

crystal

while

error

in

measurements made with thehigh-dose-rate detector waslarge because of the small

dose rate [µSv/h]because of the high counting

0.08
0.06
0.04

counting rate achieved with

0.02

the small crystal.

0.00

On this basis, we decided

KURAMA for
low dose rate
KURAMA forhigh dose rate

3

18

33

48

63

78

93

108

time [sec.]

to use the low-dose-rate CsI
detector, which has a small

Figure 19: Measured value dispersion check.

123

| 45
variation at low dose rates, at geographic points with a dose rate less than 1 µSv/h, and to use thehigh-dose-rate CsI detector at geographic points with a dose rate greater than 1 µSv/h.

(2) Conducting walking surveys
With the purpose of studying the operation of walking surveys and acquiring basic data, weconducted walking surveys at places with differing conditions. Examples of such walking surveys aredescribed below.

A. Walking survey in western Fukushima City
We conducted a walking survey on a trial basis in western Fukushima City. At the center of thisgeographic area is a surface paved with asphalt, with ditches along the edges. There were no
obstructions on the outside of the asphalt surface, leaving the surface wide open and surrounded bygrass.
Results of a walking survey conducted at this geographic point are shown in Figure 20. The paved
surface at the center of the range of the walking survey had a low dose rate compared with that of thesurroundings. It is considered that this low dose rate is due to the easy decontamination of the paved
surface and the strong effect of weathering. In addition, the radiation dose in the vicinity of the ditch
was higher than that of the surroundings. This is probably because there was an inflow of radioactive
material from the surrounding area.
We conducted a high-density walking survey and tested interpolation with a GIS tool (Figure 21).
Interpolation was conducted with IDW. The interpolated radiation dose rate in the paved area waslow, and the dose rate in the vicinity of the ditch was high.

Paved area

Figure 20: Results of a walking survey
in western Fukushima City.

Figure 21: Results of interpolation with
IDW.

46 |
B. Walking survey in the periphery of a temporary storage area

We conducted a walking survey ina temporary storage area and its
periphery in the Nakadori region of
Fukushima Prefecture (Figure 22). The
area inside the red frame in the figure is
the temporary storage area. The dose
rate near the temporary storage area
was equal to or less than the dose ratein the periphery, and no effect ofexternal decontaminated waste on theoutside area was seen in this temporarystorage area.

Figure 22: Dose map.
(with the temporary storage area indicatedby the red frame.)C. Walking survey in the Hamadori region (outside the evacuation zone)
We conducted a walking survey around rivers in the Hamadori region of Fukushima Prefecture(outside the evacuation zone) (Figures 23 and 24). There is a paved surface on the left side of the
figure, with the rest of the study area being gravel or grassland. The dose rate was low on the paved
surface and nearly uniform in other areas.

Figure 23: Dose map.

Figure 24: IDW interpolation result.

D. Walking survey in a difficult-to-return evacuation zone
We conducted a walking survey in a difficult-to-return evacuation zone in Fukushima Prefecture(Figures 25 and 26). The area where the walking survey was conducted was nearly uniform grassland.
The dose rate was nearly uniform in the area, with no large deviation observed.

| 47

Figure 25: Dose map.

Figure 26: Results of interpolation by
IDW.

4.4. Conclusions
Results were obtained in developing walking surveys by 2015.
In terms of developed equipment, the walking survey system adopted KURAMA, which was designed
by Kyoto University and has a structure suitable for a walking survey. Additionally, to analyze the obtained
data or to work with other monitoring methods, such as a UAV survey, we prepared a GIS data processing
system. Furthermore, by collecting data for the determination of direction characteristics and calibration
constants, it has become possible to measure the dose rate in a walking survey.
We conducted walking surveys at several points and confirmed that it is possible to measure the air dose
rate and to create a contour map with a GIS processing system.
We published a manual for walking surveys and made the manual available to the general public.
In fiscal 2016, we are conducting walking surveys or lending necessary equipment at the request ofmunicipalities.

48 |5. FIP5: Study of proper treatment of waste containing radioactive
materials at municipal solid waste incinerators
Abstract
At municipal solid-waste (MSW) incineration facilities in operation (stoker-type incinerators), we
performed tests to characterise changes in the migration of radiocaesium to fly ash due to changes in the
combustion temperature of the MSW incinerator, the addition of a radiocaesium evaporation accelerator or
inhibitor, or the co-incineration of radiocaesium bearing used filter cloth from bag filters of MSW
incineration facilities. We also performed radiocaesium leaching tests of incinerated ash (bottom ash and fly
ash from stoker–type incinerators) and a laboratory test to examine a method to reduce radiocaesium
solubility of ash from a MSW incineration facility (i.e., a stoker–type incinerator).

5.1. Purpose
Incinerating MSW that contains radiocaesium dispersed by the accident at the Fukushima Daiichi
Nuclear Power Plant of Tokyo Electric Power Company causes radiocaesium to migrate to and become
concentrated in bottom ash and fly ash. Bottom and fly ash generated in this way cannot be disposed of ina landfill, even if the radiocaesium concentration is below 8000 Bq/kg, a reference value set by law.
Bottom ash and fly ash that must be stored in the incineration facilities has thus accumulated.
Although the level of radioactivity has decreased appreciably since the accident, ash containing
radioactive substances is still being generated from the daily incineration of MSW. Proper treatment anddisposal of the ash is an urgent issue (Figure 1)

Figure 1: Waste incineration processes and research issues.

| 49
We thus conducted tests to confirm the effectiveness of methods to control the migration ofradiocaesium to bottom ash and fly ash. After understanding general aspects of the radiocaesium leaching
characteristics of incineration ash generated in Fukushima Prefecture, we examined technologies andmethods to make radiocaesium in bottom ash and fly ash less soluble.
Used filter cloth from bag filters attached by fly ash containing radiocaesium is also generated byincineration facilities. The proper treatment of the cloth is another issue.
The co-incineration of the cloth with MSW is conceivable. To evaluate the feasibility of co-incineration,
it is necessary to understand the co-incineration-induced changes in the radiocaesium distribution tobottom ash and fly ash and its effect on the incineration facility and the environment when co-incinerationis conducted. We thus conducted co-incineration demonstration tests.

5.2. Content of implementation(1) Radiocaesium distribution between bottom ash and fly ash
Radiocaesium generally tends to evaporate during incineration and to transfer to fly ash rather thanremaining in bottom ash. The ratios of the distribution of radiocaesium to bottom ash and fly ash atincineration facilities in Fukushima Prefecture are given in Table 1. Approximately 60% of total
radiocaesium is transferred to fly ash.
Table 1: Radiocaesium distribution between bottom ash and fly ash at MSW
incineration facilities in Fukushima Prefecture.

Facilty

Capacity

Dustcollection[t/d]Annualinicineration(2011fy)

Ash generation

Radiocaesium
concentration

Radiocaesium
distribution

BA

BA

BA

[t/y]

[t/y]

FA

A

105

BF

16,035

2,053

B

120

BF

28,964

4,019

F

80

BF

20,2302,190

FA[Bq/kg]
632

FA
[％]

12,22049,400

45

55

747

3,910

34,900

38

62

1,076

16,64033,900

50

50

G

100

EP

30,111

2,912

737

3,920

36,300

30

70

H

90

BF

16,948

1,392

681

1,494

6,640

31

69

J

60

BF

10,181

1,342

336

639

4,650

35

65

N

50

BF

837

93

41

3,140

13,110

35

65

P

50

BF

8,906

720

422

2,269

5,690

40

60

Q

150

EP

35,612

4,797

724

7,540

45,500

52

48

R

40

BF

12,401

2,190

262

2,200

17,360

51

49

S

30

BF

4,574

381

86

1,706

12,26038

62Note 1 V alues in this table are not corrected for the amount of water and materials added.
Note 2 incinerators at all facilities are of the stoker furnace.
Note 3 Radiocaesium concentrations were measured in July 2011.
Note 4 Dust collection method, BF:bag filter; EP:electrostatic precipitator

We identified the following five main factors that have the potential to govern the transfer ofradiocaesium: (a) combustion temperature, (b) air ratio, (c) waste composition, (d) addition of chemicals,and (e) particle size of ash.
Among these factors, (b) air ratio (air volume) affects various system parameters, including the flue

50 |gas velocity, which potentially disturbs the combustion balance and affects proper incineration, (c)waste composition cannot be controlled, and (e) ash particle size is technically difficult to control. We
thus focused on the relationships between the migration behaviour of radiocaesium and (a) combustion
temperature and (d) addition of chemicals
A. Effect of combustion temperature
We performed tests in cooperation with Facilities A to D. All facilities were equipped with stoker
furnaces.
We compared the distribution of radiocaesium to bottom ash and fly ash when the temperature at
the incineration chamber outlet was increased (or decreased) 50°C from the normal operating
temperature with the distribution during normal operation.
To obtain a combustion chamber outlet temperature of 50°C higher or lower than that in normal
operation, we changed the temperature of combustion air supplied to the combustion chamber (i.e.,
primary air) by approximately 50°C from the temperature maintained during normal operation. The
amount of combustion air (i.e., primary air) was not changed to prevent changes in the production ofbottom ash and fly ash due to ash blow up. Other operating conditions, such as those related to thefurnace water spray and the amount of secondary air, differ among facilities.
The true combustion temperature (combustion temperature range in the incinerator) could not bemeasured directly. Therefore, we used the combustion chamber outlet temperature measured by thefacility as an index of the combustion temperature and evaluated the impact of the chamber outlet
temperature changes on radiocaesium migration. At Facility C, however, we inserted a thermocouple
into the incineration chamber to measure the internal temperature as an index of the combustion
temperature because the automatic control of secondary air flow could not be disengaged, andchanges in the combustion chamber outlet temperature might not correspond to actual changes in theincinerator internal temperature.
The test operation was continued for 1 day (i.e., 24 h) under the same conditions based on the timeneeded to stabilize the combustion state and the long retention time of the bottom ash in the system.
We sampled fly ash and flue gas at least 1 h after the establishment of the test conditions.
For bottom ash, owing to the facility-specific retention time inside the incinerator and ash
discharger, we predetermined for each facility a sampling time based on the retention times estimatedin a simple model and a tracer test (where metal cans were thrown into the waste hopper and theirarrival was observed at a planned sampling point).
Figure 2 shows sampling points for bottom ash, fly ash, and exhaust gas, and estimated retention
times of bottom ash inside the system for Facility A.

| 51

Figure 2: Sampling positions and estimated residence times ofbottom ash, fly ash, and exhaust gas at incinerator Facility A.
The measurements and analysis procedures are shown in Table 2 for the bottom ash, fly ash, andflue gas sampled as described above.
Table 2: Samples and measurement items.
Waste Composition

Moisture content, ash content, combust content, material
composition, lower calorific value、elemental analysis（C、H、N、O、S、Cl）

Bottom Ash

Radiocaesium concentration(Note 1), ignition loss(Note 2)
elemental analysis（Cs、Na、K、Ca、Mg、Al、Si、P、Fe）
Radiocaesium concentration(Note 1), elemental analysis（Cs、Na、K、Ca、Mg、Al、Si、P、Fe）
Radiocaesium concentration(Note 3), Dioxins(Note 2)

Fly AshFlue Gas

Note 1 :Four samples of bottom ash and fly ash were collected every hour. Four were mixed
and distributed for the analysis. Radiocaesium concentration of Four samples before
mixing were also subject to NaI gamma ray spectrometer.
Note 2 :Conducted to check that there is no incomplete combustion under low temperature
operation.
Note 3 :Conducted to check that there is not increased radiocaesium under hightemperature operation and operation with radiocaesium evaporation promotoin
agents added.

Analytical results for the waste composition are given in Table 3 and constitute the most basic
information about waste. Compositional differences are thought to define the behaviour ofradiocaesium in the combustion process.

52 |Table 3: Waste composition analysis.
Facility
Collection date(2014)
Apparent specific gravity
Moisture content
Ash content
Lower callorific value
Paper/cloth
Plastic/synthetic
resin/rubber/leather
Compsition of
Wood/bamboo/straw
dried waste
Kitchen waste
Non-burnable
Other(under 5mm )Paper/cloth
Plastic/synthetic
resin/rubber/leather
Wood/bamboo/straw
Ash content ofKitchen waste
dried waste
Non-burnable
Other(under 5mm )Total
CarbonHydrogen
Nitrogen
Elemental
composition
Sulphur
Chlorine
Oxygen6/26
3[kg/m ] 220
[％]
45.65
[％]
9.72
[kJ/kg] 8,460
[％]
53

A
6/27
217
47.12
6.32
9,380
38.4

10/15
131
39.18
10.16
9,920
39.4

7/9
139
43.16
8
8,330
59.2

B
7/10
223
45.13
7.36
9,420
45.4

7/29
97
36.38
5.54
12,100
56.3

C
7/30
126
45.78
6.14
10,130
37.5

11/25
184
49.38
8.15
7,700
39

D
11/28
176
45.15
6.86
8,620
49.7

[％]

22.6

27.1

18.6

15.5

21.2

22.7

32.9

21.4

24.1

[％]
[％]
[％]
[％]
[％]

13.7
3.7
2.3
4.7
5.6

10
14.3
2.4
7.8
4.4

24.8
9.5
5.1
2.6
5

8.1
13.9
0.4
2.9
7.7

11.2
10.4
4.6
7.2
2.9

6.7
9.2
0.6
4.5
4.9

12
8.4
2.5
6.7
4.3

14.1
14.9
4.3
6.3
3.7

8.3
10
0.7
7.2
4.5

[％]

1.9

1.2

1

0.9

1.4

1.2

1.6

1.9

2.7

[％]
[％]
[％]
[％]
[％]
[％]
[％]
[％]
[％]
[％]
[％]

4.7
0.7
2.3
2.7
17.9
40.36
6.36
0.71
0.08
0.31
36.2

1.1
1
2.4
1.9
12
49.98
8.1
0.81
0.07
0.16
31.07

3.1
1.1
5.1
1.3
16.6
47.11
7.19
1.16
0
0.81
31.48

1.6
2.5
0.4
1.1
14.2
44.15
6.49
1.18
0.07
0.15
34.2

0.4
1.5
4.6
2.6
13.4
48.27
7.19
1.48
0.08
0.57
33.19

0.4
0.6
0.6
1
8.7
50.91
8.23
0.56
0.06
0.42
31.68

0.7
0.6
2.5
1.6
11.3
54.47
9.3
0.66
0.07
0.42
26

0.8
3.1
4.3
2.3
16.1
44.37
7.07
0.97
0.06
0.21
34.97

0.9
1.7
0.7
2
12.5
46.9
7.1
0.61
0.07
0.21
33.17

We did not observe a clear relation between the composition of waste and the area or season inwhich the waste was generated. The waste incinerated at Facilities A and B had calorific values of
8,330 to 9,920 kJ/kg, while all values exceeded 10,000 kJ/kg at Facility C, which had higher caloric
value for waste in summer. Meanwhile, although Facility D received autumn waste at the end of
November, it had the lowest calorific value.
B. Continuous sampling test
We conducted a tests in order to understand the relations between combustion temperature andradiocaesium distribution during normal furnace operation. Stoker furnace equipped two facilities (Band F) hosted continuous five days bottom and fly ash sampling of every two hours. Ash sampledwere subject to radiocaesium concentration measurement by NaI spectroscopy.
The first four samples obtained each day were mixed together, divided and distributed for Ge
measurements and an elemental (Cs, Na, K, Ca, Mg, Al, Si, P, and Fe) analysis. These data were used
to examine the relationship between the combustion temperature during normal operation andmigration behaviour (distribution to bottom ash/fly ash) of radiocaesium.
Sampling points and times were determined according to the methods employed in subsection (1)A.
C. Effects of a radiocaesium evaporation accelerator and inhibitor
We examined the effects of adding hydrated lime (Ca(OH)2), which is expected to promote the| 53
evaporation of radiocaesium, and bentonite (clay), which is expected to inhibit the evaporation ofradiocaesium.
① Test of hydrated lime (2.4%) and bentonite (2.2%) addition at Facility A② Test of hydrated lime (2.6%, 5.5%) addition at Facility A to determine the reproducibility of theeffect observed in test ①.
③ Test of hydrated lime (2.2%) addition at Facility D to determine whether the results obtained in
tests ① and ② are facility-specific.
④ The materials were sprayed on the surface of each crane of waste thrown into the hopper.

(2)

Proper treatment of used filter cloths of bag filters
We conducted three test runs at both Facility B using glass-fibre made filter cloths and at Facility E

using Tefaire® filter cloths. In one run, ordinary incineration was performed without used filter cloths
co-incineration (Run-1). In the other two runs, co-incineration of used filter cloths with MSW was
performed, but the used filter cloth throw-in ratio and interval differed betweenRun-2 and Run-3(Table 4). At Facility B, two used filter cloth throw-in ratios were set according to a questionnaire
survey of facilities having with actual experience with co-incineration treatment. These were the meanvalue of 0.20% and the maximum value of 0.40%. At Facility E, the throw-in ratio was set to 0.03%
according to ‘Cleaning Technical Report, No. 8’ issued by the Clean Authority of Tokyo (2008) andother data7)8). The incinerators at both facilities are stoker-type incinerators.
Table 4: Details of the used bag filter cloth co-incineration test.
Facility name
Filter cloth materialRun
Co-incineration ratio
Filter cloth input amount
Input amount and time interval, time continued
Used filter
cloth

RUN 1
Normaloperation

Radiocaesium

B (60 t/furnaceday)
Glass fibre
RUN 2
RUN 3
0.2%
0.4%
6.4 kg/H
12.8 kg/H(1.5/0.5 H),
3/0.5 H, 6 H
6h

RUN 1
Normaloperation○

E (75 t/furnaceday)
Tefaire®
RUN 2
RUN 3
0.03%
0.90 kg/H
0.5/1 H, 6 H
1.5/3H, 6 H○

Radiocaesium
Hydrogen chloride

○
–

○
○

○
○

○
–

–
○

○
○

Sulphur oxide
Nitrogen oxide

–
–

○
○

○
○

–
–

○
○

○
○

Dioxins (*2)
Fluorinecompounds

–
–

–
–

○
–

–
○

–
○ (fourtimes)○○ (fourtimes)

Radiocaesium
(*1)

○

○

○

○

○

○

Bottom ash

Fly ashIgnition loss (*2)
Radiocaesium
(*1)

–
○

–
○

○
○

–
○

–
○

○
○

Flue gasMeasurement
item*1) Radiocaesium samples were collected once perhour for NaI measurements, for a total of fivesamples, four of which were mixed into one sample
and then divided for Ge measurements.
*2) Conducted in the RUN under the most severe
conditions.

There were two cases of the co-incineration ratio(average 0.20% and maximum 0.40%) based onquestionnaire survey results of facilities that
previously conducted co-incineration before.
Filter cloth dimensions: φ164 mm  5250 mm(L).
The manufacturer’s standard value was used forweight: 2.38 kg each, calculated from a densityof 880 g/m2.
Radiocaesium concentration of the filter cloth
subject to co-incineration: 600 Bq/kg.

The co-incineration ratio was set at 0.03%,
according to “Seiso Giho No. 8 2008 Tokyo
23 Special District Authority”.
Filter cloth dimensions: φ140 mm  6000 mm(L).
The manufacturer’s standard value for weight
was used: 1.71 kg each calculated from adensity of 650 g/m2, but the measured value atthe facility was 2.0 kg each.
Radiocaesium concentration of the filter cloth
subject to co-incineration: 1260 Bq/kg.

54 |Regarding the effects of co-incineration on the migration behaviour of radiocaesium due to fly ashthat contains radiocaesium adhering to the filter cloth, the effect of used cloths with glass fibre forwhich combustion is difficult in the established conditions, and the increase in the concentration offluorine compounds due to the combustion of Tefaire®, we collected and analysed bottom ash, fly ash,and flue gas before and during the test or collected measurements obtained by the facility. For these
items, we then compared the data obtained before inputting the filter cloth and during the test andsurveyed the effects. Sampling points and times were set according to the methods described insubsection (1)A.

(3) Study on the reduction of radiocaesium leaching from fly ash
A. Data acquisition of radiocaesium leaching characteristics
We sampled bottom ash, fly ash and limited number of boiler ash from 15 incineration facilities
in Fukushima Prefecture and performed radiocaesium leaching tests for a total of 64 samples toacquire radiocaesium leaching data. For some facilities, we sampled and tested summer and winterash to evaluate seasonal changes in radiocaesium leaching properties. Leaching tests were
performed in accordance with ’JIS K0058-1, As-is Agitation Test’; each sample was placed in acontainer as is, pure water was added at a volume that was 10 times greater than the amount of ash(L/kg), and the top liquid phase was agitated with a propeller.
B. Laboratory radiocaesium immobilisation test
As zeolite, bentonite, and sewage sludge are expected to reduce radiocaesium leaching fromincineration ash, we used these three materials as additives to the sampled incineration ash. The test
procedure simulates the actual fly ash kneading process. We added the materials to bottom ash, flyash, and treated fly ash obtained from Facility K at various ratios (20% and 5% of dry ash weight)
and added water (30%). The water-supplemented samples were thoroughly mixed and kept at various
temperatures (25°C and 80°C) for different periods (one week and one month). Then, each sample
was subjected to leaching tests.

5.3. Results(1) Radiocaesium distribution between bottom ash and fly ash
A. Effect of combustion temperature
Data on the migration and distribution of radiocaesium are given in Table 5.
Ordinary untouched operation is regarded as a standard test.
The tests were conducted at four facilities, but we were unable to obtain a combustion chamber
outlet temperature that was higher than that of standard operation during high-temperature operation
at Facility C. Additionally, at Facility D, we were unable to obtain a combustion chamber outlet
temperature that was lower than that of standard operation in low-temperature operation.

| 55
Table 5: Combustion temperature and migration of radiocaesium for each facility and each test.
Facility

A

Test
date

[℃]

Bottom ash

Bottom ash[℃]

Fly ashFly ashFly ash/bottom
Distribution
ash radiocaesium
ratio % ofconcentration
radiocaesium
ratio(※3）
to fly ash

Standard1

125

904

1,580

8,300

1,900

13,00060

6.8Standard2

121

912

1,750

10,3002,100

16,00063

7.6

6/26 High temp1

183

964

2,020

10,8002,500

17,00061

6.8

6/27 High temp2

189

950

1,460

13,5001,900

21,000

72

11.1

119

923

840

14,8001,100

23,000

84

20.9

123

940

1,990

14,6002,400

23,000

69

9.6

121

904

1,260

14,5001,400

20,000

76

14.3

116

891

920

15,7001,200

22,000

83

18.3

116

904

540

10,400650

15,000

84

23.1
5.7

10/14
10/16
10/17

Hydrated
lime2.4%
Bentonite
2.2%
Standard
Hydrated
lime2.6%
Hydrated
lime5.5%

7/8

Low temp1

101

855

1,020

5,700

1,200

6,800

68

7/9

Low temp2

103

842

900

4,600

980

5,500

67

5.6

7/10 High temp1

200

946

940

5,100

1,000

6,100

68

6.1

7/11 High temp2

194

956

590

4,700

630

5,600

76

8.9

930

7,800

1,100

12,000

71

10.9

1,110

6,400

1,300

9,900

64

7.6

1,740

9,600

1,800

15,000

63

8.3

1,490

9,500

1,700

15,000

64

8.8
6.7

7/28

933
※1
(1043)
931
※1
(984)
924
※1
(1040)
937※1(1075)

Standard1

52

7/29 High temp1

100

7/30 High temp2

100

7/31

Standard2

52

11/25 Standard1

178

880

480

1,590

430

2,900

54

11/26 Low temp1

129

867

480

1,450

430

2,600

52

6

11/27 Low temp2

134

873

453

1,470

400

2,600

54

6.5

11/28 Standard2

177

883

530

1,250

470

2,200

46

4.7

Hydrated
lime2.2%

178

893

410

1,280

360

2,300

53

6.4

C

D

Radiocaesium
concentration[Bq/kg](corrected value(※2））

Combustion
chamberoutlet temp

6/24

7/3

B

Radiocaesium
concentration[Bq/kg](measurement value）

Primary
air temp

6/23

7/2

A
Add

Test

11/29

(※1) In-core farnace tempreture measured with a provisionally installed thermocouple(※2) Measured values were corrected for flue gas treatment agents and water added during the process.
(※3) Corrected values were used.

At Facilities A and B, where high-temperature runs produced high combustion chamber outlet
temperatures, the ratio of distribution to fly ash increased on the second day of the high-temperaturerun. We obtained a rise of 2.6% in the distribution rates at Facility A and a rise of 0.8% at Facility B
per 10°C combustion temperature by linear approximation, excluding data obtained on the first day(Figures 3 and 4).

(Facility A)
Hydrated Lime 2.4%
High Temp 2
BentoniteStandard 2
Standard 1
High Temp 1

Combustion chamber outlet T (℃)

Figure 3: Rate of the distribution ofradiocaesium to fly ash versus the
combustion chamber outlet
temperature (Facility A).

Radiocaesium distribution ratio to
fly ash (%)

Radiocaesium distribution ratio to
fly ash (%)

56 |(Facility B)
High Temp 2
Low Temp 2
Low Temp 1

High Temp 1

Combustion chamber outlet T (℃)

Figure 4: Rate of the distribution ofradiocaesium to fly ash versus the
combustion chamber outlet
temperature (Facility B).

To examine variation in the temperature and migration status of radiocaesium before and after
changing the combustion temperature conditions from standard to high-temperature operation, we
sampled bottom ash and fly ash every 2 h for 2 days at Facility B, and measured by a NaI. In responseto the change in operation mode from low-temperature operation to high-temperature operation, thecombustion chamber outlet temperature increased approximately 100°C, from 850°C to 950°C, andthe ratio of fly ash/bottom ash radiocaesium concentration increased along with the increasing
temperature (Figure 5).

Figure 5: Combustion chamber outlet temperature andradiocaesium concentration ratio (Facility B).

| 57
B. Continuous sampling test
Figures 6 (Facility B) and 7 (Facility F) show the combustion chamber outlet temperature, NaIdetector-based radiocaesium concentration in bottom ash and fly ash, ratio of the radiocaesium
distribution to fly ash based on NaI measurements, and ratio of the radiocaesium distribution ratio
to fly ash based on Ge measurements.

Figure 6: Radiocaesium concentrations in bottom ash and fly ash, radiocaesium
distribution based on NaI and Ge measurements, and combustion chamber outlet
temperature (dry ash at Facility B).

Figure 7: Radiocaesium concentrations in bottom ash and fly ash, radiocaesium
distribution besed on NaI and Ge measurements, and combustion chamber outlet
temperature (dry ash at Facility F).

58 |It is difficult to detect a clear relationship between the combustion chamber outlet temperature andthe distribution of radiocaesium to fly ash.
As shown in the plots of the temperature against the ratio of the radiocaesium distribution to fly
ash based on NaI measurements (Figures 8 and 9), the increase in the combustion chamber outlet
temperature at Facility B was accompanied by an increase in the ratio of the radiocaesium distribution
to fly ash. Sudden drops in temperature may correspond to the inputs of sewage sludge, and it should
be noted that the waste composition also changed substantially. The range of outlet temperatures forthe combustion chamber of Facility F was small, and no clear relationship between the radiocaesium
distribution ratio and combustion chamber outlet temperature was observed.

Figure 8: Combustion chamber outlet
temperature and radiocaesium distribution
to fly ash (Facility B); the radiocaesium
concentration was measured by NaI.

Figure 9: Combustion chamber outlet
temperature and radiocaesium distribution
to fly ash (Facility F); radiocaesium
concentration was measured by NaI.

Regarding the relationship between basicity and radiocaesium distribution, at Facilities F, wedetected positive correlations between the basicity of the waste calculated from the chemicalcomposition of ash sampled during the 5-day continuous sampling test and the radiocaesium
distribution ratio to fly ash (Figure 11). However, we found no positive correlations at the Facility
B(Figure 10).

Figure 10: Basicity and radiocaesium distribution to fly ash calculated
from the ash composition (Facility B).

| 59

Figure 11: Basicity and radiocaesium distribution to fly ash calculated
from the ash composition (Facility F).

C. Effects of a radiocaesium evaporation accelerator and inhibitor
The addition of hydrated lime Ca(OH)2, (subsection 5.2.(1) C ①) at Facility A increased the ratioof radiocaesium distribution to fly ash remarkably (9.3% increase per 1% addition). However, theinhibitory effect of bentonite could not be confirmed (Figure 12).

Figure 12: Effect of additives on the radiocaesium distribution to fly ash(Facility A).
We conducted additional tests to determine the general effects of hydrated lime; an effect was
confirmed at Facility A, but it was weaker than that observed in the first test. Additionally, hydrated
lime had no effect at Facility D (Figure 13).

60 |Figure 13: Effect of hydrated lime on the radiocaesium distribution
to fly ash (Facility D).

A higher basicity of incinerated waste of Facility D should accelerate the evaporation ofradiocaesium1). The basicity of the waste, based on the chemical analysis of bottom ash and fly ash
conducted at Facilities A to D, is given in Table 6. The basicity of waste at Facility A was lower thanthat at other facilities. It is probable that the obvious effect observed at Facility A was due to theaddition of the basicity-increasing material, hydrated lime, to low-basicity waste. In the case of
Facility D, it is possible that the basicity-increasing material was added to waste whose basicity was
somewhat high, and the hydrated lime thus did not promote the evaporation of radiocaesium.
Table 6: Basicity of waste calculated from the chemical compositions of BA and FA.
Facility
Ash samplingdate(2014)
Hydrated lime
added[%]
CaO/SiO2

A
6/23 6/26--

0.44 0.55
0.49

7/2
2.4
1.03※1(CaO+MgO+Al2O3) 0.81 0.97
1.43※1/SiO2
0.88
Radiocaesium
60
61
84
distribution to
FA[%]

B

10/14 10/16 10/17
-

2.6

5.5

0.65 1.02※2 1.42※2
1.07 1.46※2 1.89※2
76

83

84

7/8

C

D

7/10 7/28 7/29 11/25 11/26

-

-

-

-

0.82 1.11 0.96 0.62
0.95

68

68

64

0.75

0.71
1.11

1.33
71

-

0.67

0.77

1.38 1.79 1.58 1.13
1.56

-

1.22

1.16
54

52

11/29
2.2
1.42※3
1.89※353

Calculation of basisity for days that hydrated lime was added: We used the average of analyzed chemical composition values andadded hydrated lime quantity of 6/24 and 7/2(※1), the analyzed value of 10/14 for 10/16 and 10/17(※2), and the average ofanalyzed value and added hydrated lime quantity of 11/25 and 11/26 for 11/29(※3）.

In this test, strict operating conditions were used that differ from typical operating conditions, andit was thought that these conditions increased the radiocaesium concentration in flue gas. We
therefore conducted measurements of flue gas and dioxins. We did not detect radiocaesium in the flue

| 61gas. Furthermore, the dioxin concentration in the flue gas and ignition loss values of bottom ash met
relevant regulations (Table 7).
Table 7: DXNs concentration in flue gas and ignition loss of bottom ash.
Operating
Facility
Measurement datecondition
B
C

Low-T
Low-T
Low-T
Low-T

2014
2014

DXNs in flue[ng-TEQ/m3N]

IL of BA [%]Measured Criteria Measured Criteria

July 8July 8
Nov. 26
Nov. 27

0.032
0.019
0.00040.00038

5.9
6.0
<0.1
0.2

5
0.1

10
10

(2) Proper treatment test of used filter cloths of bag filters
The co-incineration of used filter cloth with MSW was confirmed to be safe and feasible under theproper management of the co-incineration ratio.
Based on many measurements, used filter cloth co-incineration did not affect the measurements, but
increased the concentration of radiocaesium in ash (Table 8).
Table 8: Radiocaesium concentration in bottom ash and fly ash.
Facility

B

Test RUN No.

RUN 1

Used filter cloths input(pieces)
Used filter
Radiocaesium
clothsconcentration（Cs-134＋Cs-137） Bottom ash[Bq/kg]Fly ash

-

RUN 2

E
RUN 3

1.5/0.5H 3.0/0.5H

RUN 1
-

600

RUN 2

RUN 3

0.5/1.0H 1.5/3.0H
1,260

318

400

800

266

157

105

2,400

3,260

3,640

1,400

1,210

1,220

An increase was observed at Facility B and no increase was observed at Facility E. The increase isthought to be caused by a change in the radiocaesium concentration in co-incinerated MSW, rather than
the input of used filter cloth. This is supported by two pieces of evidence. First, the increase was higher
than the value calculated from the radiocaesium concentration of the input filter cloth. Second, theincreased values remained within the range of variation of the measurements obtained by the facility in2015. No radiocaesium was detected in flue gas and no effects of co-incineration on flue gas wereobserved. Table 9 presents the results for Facility E.
Regarding concerned fluorine gas when Tefaire cloths were co-incinerated, measured values wereless than approximately 1 mg/m3N.
There were no changes in the ignition loss of bottom ash, harmful acidic substances, and dioxins influe gas at either facility. These parameters are conceivably change when combustion conditions
deteriorate (Table 10).

62 |Table 9: Radiocaesium concentration in flue gas during bag filter cloth co-incineration tests.
Facility

B

Sampling pointE

Bag filter outlet

Bag filter outlet

Sampling date(2015)

7/28

7/29

7/30

10/26

10/27

10/28

RUN no. and used filter cloth input
rate(pieces)

RUN1

RUN2

RUN3

RUN 1

RUN 2

RUN 3

-

0.5/H

1.5/H

Radiocaesium
concentration in fluegas

FilterDrain

3[Bq/m N]-

1.5/0.5H 3.0/0.5H

Cs-134

<0.3

<0.3

<0.3

<0.3

<0.3

<0.3

Cs-137

<0.3

<0.3

<0.3

<0.3

<0.3

<0.3

Cs-134

<0.3

<0.3

<0.3

<0.3

<0.3

<0.3

Cs-137

<0.3

<0.3

<0.3

<0.3

<0.3

<0.3

3

63,90064,60037,60038,50035,300

Wet flue gas[m N/h]56,000Dry flue gas[m N/h][%]344,40054,70052,20026,10027,10025,600

20.8

14.5

19.1

30.2

29.6

27.1

CO2

[%]

2.9

2.5

3.2

5.6

6.7

6.3

O2

[%]

17.6

17.9

17.1

14.7

13.5

13.8

CO

[%]

<0.1

<0.1

<0.1

<0.01

<0.01

<0.01

N2

[%]

79.5

79.6

79.7

79.7

79.8

79.9

Moisture content
Gas
composition

Table 10: Harmful acidic substances and dioxins in flue gas, and ignition loss of bottom ash.
FacilityB

RUN No.

Flue gas

RUN2

RUN3

E
Past figure

RUN2

RUN3

<5

<5

150

170

120

150

<10
(2015)
140～150(2015)
27～32(2015)SOx[m N/h]

3

<5

<5

NOx

[ppm]

140

160

HCl

[mg/m N]

3

<10

<10

HF

[mg/m N]

3

-

-

-

<1.1

<1

3

-

0.01

0.046～0.072(2015)-

0.0028

[%]

-

5.1

5.0～8.1(2015)-

5.1

Dioxins
Bottom Ignition
ash
loss

[ng-TEQ/m N]

Past figure<3.5～80(2015)
99～180(2015)<5～310(2015)<1（2015）
0.060～0.099(2015)
1.3～6.2(2015)(3) Study of the reduction of radiocaesium leaching from fly ash
A. Data acquisition of radiocaesium leaching characteristics
We sampled bottom ash and fly ash from 15 MSW incineration facilities in Fukushima Prefecture
and performed radiocaesium leaching tests using these samples. The test results indicate thatradiocaesium leaching from bottom ash was limited (below 1% to 16%), but leaching from fly ash
was extreamly high (35% to 94%), as is generally known (Tables 11-1, 2, 3, and 4). Please note that‘BA’ and ‘FA’ in the tables are the abbreviations of ‘bottom ash’ and ‘fly ash’ respectively.

| 63
Table 11-1: Radiocaesium leaching test results (1).
FacilityA
2014

Samplimg date

6/23

Sample typeRadiocaesium
concentration in solid[Bq/kg]

Cs134
Cs137

7/2

【Leaching test】
Radiocaesium
concentration in liquid[Bq/L]
Leaching rate

BA

9/10
FA

BA

9/11
FA

25

65

250

C
2014
7/28
BA
FA

D
2014
11/25
BA FA

E
2015
10/26
BA FA

92

56

BA

FA

BA

FA

BA

9/7
FA

BA

9/8
FA

400

2,100

300

3,900

45

380

43

320

24

190

300

1,700

1,400 6,100

760

11,000 220 1,600 230 1,500 180 1,100 230 1,100 130

960

790

5,500 350 1,100 210 1,100

Total 1,800 8,200 1,060
Cs134
Cs137

B
2015
9/9
BA FA
280

390

300

14,900 265 1,980 273 1,820 205 1,380 295 1,350 154 1,150 1,090 7,200 442 1,490 266 1,400

0.1

130

0.1

230

0.1

31

0.1

28

0.1

20

0.1

15

0.1

18

0.1

130

2

16

0.1

22

1

360

3

670

1

130

0.1

110

0.1

94

0.1

70

0.1

77

2

380

5

54

0.1

92

Total

1

490

3

900

1

161

0.2

138

0.2

114

0.2

85

0.2

95

2

510

7

70

0.2

114

[％]

0.6

59

3.6

61

3.8

81

0

76

0.0

83

0

63

0

83

2.2

65

16

47

0

81

FA-t

Table 11-2: Radiocaesium leaching test results (2).
10/13
BA

10/12
FA

10/14
BA

10/13
FA

F
2015
10/15 10/14
BA
FA

BA

G
2016
3/11
FA
FA-t

BA

I
2016
3/17
FA

550

4,100

1,000

6,300

700

5,500

930

4,700

580

4,300

42

310

300

9

50

200

2,300

840

2,300

17,0004,500

27,0003,100

23,0003,900

20,0002,500

18,000220 1,600

1,500

40

260 1,200

11,0004,200

Total 2,850

21,1005,500

33,3003,800

28,5004,830

24,7003,080

22,300260 1,900

1,800

49

310 1,400

13,000

5,000

3

290

3

350

2

330

1

310

2

300

<0.1

21

24

<0.1

5

1

75

80

12

1,200

11

1,500

8

1,400

6

1,300

10

1,300

0.2

100

120

0.1

24

6

270

390

15

1,490

14

1,850

10

1,730

7

1,610

12

1,600

<0.3

120

140

<0.2

29

7

450

470

5

71

3

56

3

61

1

65

4

72

<1

63

78

<4

94

5

35

94

Facility
Samplimg date
Sample typeRadiocaesium
concentration in solid[Bq/kg]

Cs134
Cs137

Cs【Leaching test】
134
Radiocaesium
Csconcentration in liquid 137[Bq/L]
Total
Leaching rate

[％]

10/16
BA

10/15
FA

10/17
BA

10/16
FA

H
2016
3/1
BA FA-t

Table 11-3: Radiocaesium leaching test results (3).
Facility
Sampiling date(2016 fy)J
8/24 2/10 8/24 2/10 8/24 2/10
BA
FA
BA
S
W
S
W
S
W

8/24 2/10
FA
S
W

K
8/24 2/10
Boiler ash
SW

8/24 2/10 8/25 2/9
FA-t
BA
S
W
S
W

S

W

Radiocaesium
concentration in solid[Bq/kg]Cs-134

<6

10

48.3

81

74

10

340

129

553

274

103

31

16

244

232

Cs-137
Total

44
<50

67
77

315
363

560
641

404
478

67
77

2,010
2,350

841
970

3,110 1,960 1,640
3,660 2,260 1,910

718
821

174
205

105
121

1,480 1,570
1,720 1,800【Leaching test】
Radiocaesium
concentration in liquid[Bq/L]

Cs-134

<0.6

<0.4

3.9

6

<0.8 <0.4

29

10.2

19.6

11.5

26

9.2

<0.9 <0.4

19

19.5

Cs-137

<0.7

<0.4

24.6

42

0.8

<0.4

157

66.7

117

76.3

138

62.1 <0.7

0.5

113

134

Total

<1.3

<0.8

28.5

48

<1.6 <0.8

186

76.9

137

87.8

164

71.3 <1.6 <0.9

132

154

Cs-134+
Cs-137<10.
<26.0 <10.4 78.5 74.9 <3.3
4

79.1

79.3

37.4

38.8

85.9

86.8 <7.8 <7.4

76.7

85.6

CS-137

<15.9

78.1

79.3

37.6

38.9

84.1

86.5 <4.0

76.4

85.4

Sample type

Leaching rate[%]

<6.0

78.1

75

2

<6.0

298

L
8/25

2/9
FA

4.8

Table 11-4: Radiocaesium leaching test results (4).
FacilityM

Sampiling date(2016 fy)【Leaching test】
Radiocaesium
concentration in liquid[Bq/L]
Leaching rate[%]

N

1/30

9/6

2/8

8/25

8/25

S

W

S

W

Boiler ash
S
W

S

W

S

W

Cs-134

452

438

1,290

1,460

1,530

815

908

76

69

Cs-137
Total

2,460 2,780 6,960 9,150 8,570 5,720 4,710 5,860 409 464 4,750 3,040 187 103 1,190 1,120 995 754
2,910 3,220 8,250 10,600 10,100 6,610 5,530 6,770 485 533 5,590 3,490 215 118 1,410 1,290 1,170 865

Cs-134

<0.9

<0.5

51

82

46

17.7

48

56.9 <0.6 <0.6

59

35.8 <0.7 <0.4

11

7.5

7.8

Cs-137
Total
Cs-134+
Cs-137
CS-137

1
<1.9

<0.7
<1.2

284
335

521
603

270
316

117
135

271
319

365 0.9 2.2
422 <1.5 <2.8

344
403

235
271

64
75

51.5
59

44.5 35.3
52.3 40.6

BA

FA

893

1/30 9/30 2/9

O

1/20

Sample typeRadiocaesium
concentration in solid[Bq/kg]

8/25

FA-t

9/30

2/9

9/30 2/10

S

W

S

W

836

450

28

15

BA

FA

9/30

2/10

9/30

S

W

S

W

219

170

171

111

BA

FA

<0.8 <0.4<1.5 <0.8

2/10

FA-t

5.3

<0.7

<0.4

40.6

56.9

31.3

20.4

57.7

62.3 <3.1 <5.3 72.1

77.7 <7.0 <6.8 52.9

45.7

44.7

46.9

0.4

<0.3

40.8

56.9

31.5

20.4

57.5

62.3

77.2 <4.3 <3.9 53.4

46

44.7

46.8

2.2 4.7

72.4

64 |
For ash from Facilities D and M, we should note that the radiocaesium leaching rate was low for
fly ash but high for bottom ash. In addition, the radiocaesium concentration in incinerated ash may
differ greatly among facilities. We saw no clear seasonal trends in the radiocaesium leaching rates
when comparing summer and winter (Figures 14 and 15).

Figure 14: Facility-by-facility radiocaesium
concentration in summer and winter samples.

Figure 15: Facility-by-facility radiocaesium
leaching rate from summer and winterincineration ash.

Here, fly ash refers to crude ash captured by a bag filter not yet treated by chelating agent additionor other methods. Treated fly ash is described as FA-t. If possible, we also sampled and measured
boiler ash whose generation is small and indicated as “BoA”. Radiocaesium concentration of BoA is
closer to FA and radiocaesium leaching rate shows intermediate value between BA and FA.

| 65
B. Laboratory radiocaesium immobilisation test
Table 12 and Figure 16 show relationships between test specimen conditions (ash type, additive
material type, addition rate, curing temperature and curing time) and the radiocaesium leaching rate.
Table 12: Laboratory radiocaesium immobilisation test.
Ash
type

CuringCs
Added
Addition
Curingtemperaleaching
chemicals
ratio
periodture[℃]
rate [％]
Chemicals not added
25

Zeolite

25
20%
80
25
5%
Fly ash80
Bentonite
25
20%
80
25
5%
80

Sewagesludge25
20%
80CuringAdded
Addition
Curingtemperachemicals
ratio
periodture[℃]
Chemicals not added

79.1
1week

13

1month

18.3

1week

51.2

1month

57.8

1week

4.3

1month

4.8

1week

17.3

1month

24.2

1week

41.9

1month

45.5

1week

53.4

1month

67.2

1week

14.1

1month

14.8

1week

17.2

1month

28.7

1week

71.5

1month

79.2

1week

81.7

1month

87.9

1week

66.2

5%
80

Ash
type

1month

61

1week

66.5

1month67.9

85.9

ZeoliteTreatedfly ash Bentonite

Cs
leaching
rate [％]
24.8

20%

80

1monthSewagesludge14.7
59.4

Chemicals not added
25
5%80
Zeolite25
20%
80

Bottom
ash

25
5%
80
Bentonite
25
20%
80

2
1week

<0.9

1month

<1.1

1week

<0.9

1month

<1.1

1week

<1.0

1month

<1.0

1week

<1.1

1month

<1.0

1week

<1.0

1month

1

1week

<1.0

1month

<0.9

1week

<1.1

1month

<1.1

1week

<1.2

1month<1.0Black numerals indicate elution rates calculated from caesium-134 and caesium-137, and red and blue
numerals indicate elution rates calculated from caesium-137 (Red indicates the most immobilised case).

Figure 16: Relationship between leaching rate and additive, rate of addition,
cure temperature and cure duration (Fly ash).

66 |A very obvious reduction of radiocaesium leaching rate was observed for fly ash. The addition of
20% zeolite and 1 week of curing at 25°C resulted in the greatest reduction in the radiocaesium
leaching rate, from 79.1% to less than 5%.
The materials added to fly ash showed leaching rate reduction in decreasing order as follows:zeolite, bentonite and sewage sludge. Both zeolite and bentonite showed1/3 lower leaching rates forthe addition of 20% than for 5%. Zeolite was not effective at a higher cure temperature (80°C)
compared with bentonite. For both zeolite and bentonite, longer (one month) curing duration had
slightly adverse effects on the leaching rate reduction.

5.4. Conclusions
Table 13 summarizes the achievements. Various methods have been developed to control theradiocaesium distribution in bottom ash and fly ash during the MSW incineration process. These include
changing the combustion temperature. However, we found that it was difficult to change the temperature
within a range that is applicable to an incinerator in operation because the Waste Management and Public
Cleaning Law prescribes maintenance and management standards. The addition of chemicals to the waste
has promoted radiocaesium migration to fly ash to a great extent but the reproducibility of this effect waspoor. Waste composition possibly affects the promotion or inhibition of migration in response to added
chemicals. We will determine their impact by laboratory tests, where waste composition is easy to control.
With respect to the co-incineration of waste bag filter cloths with MSW at their original facility, we
verified that co-incineration is a safe and appropriate treatment method when the ratio of the cloths in the
mixture is managed appropriately.
We checked radiocaesium leaching characteristics from MSW incineration ash of facilities in theprefecture by radiocaesium leaching tests. According to the test result, the leaching rate differs remarkably
between bottom ash (35% to 94%) and fly ash (less than 1% to 16%), differs depending on the facility,and does not show any significant seasonal changes. We will add and update data periodically.
In the laboratory radiocaesium immobilisation test, zeolite and bentonite, especially zeolite showed
excellent ability to reduce the leaching rate of radiocaesium from fly ash from 79% to less than 5%. This
result shows its possible practical application. We will further examine better methods for the addition andmixing of the material and ash, and identify materials capable of more effective radiocaesium leaching
reduction. We plan to improve the understanding of the longevity of the leaching reduction effect and theeffect of chelation.
Some of the achievements to date were presented at the Japan Waste Management Association
Meeting8),9). The information has also been provided to Fukushima Prefecture's general waste management
division and municipalities as well as the special district authorities in the prefecture at the waste
management meeting held by the general waste management division. We will continue to provide
information to contribute to the proper treatment of waste contaminated with radioactive materials.

| 67
Table 13: Achievements to date.
Test

No. of facility
cooperated

Results

4

Tests were conducted at four facilities but the expected combustion temperature was not
obtained in some cases. In cases where high combustion temperature could be obtained,radiocaesium distribution to fly ash increased on the second day run (Distribution ratio
up rise of 0.8% and 26% per 10℃ rise of combustion temperature).

(A)-1
Effect of combustion
temperature（A）
Radiocaesium
distribution between
bottom ash and fly ash(A)-2Continuous sampling test

2

(A)-3
Effect of a radiocaesium
evaporation accelerator
and inhibitor（B）
Proper treatment of used filter cloths of bag filters

2

2

(C)-1
（C）
Study of the reductionof radiocaesium
leaching from fly ash

Date acquisition ofradiocaesium leaching
characteristics

15

(C)-2
Laboratory radiocaesium
immobilisation test

1

Relationships between combustion temperature during usual operation andradiocaesium migration behaviours (distribution to bottom ash and fly ash) were
investgated. No clear relationships were found.
In the first test, when hydrated lime (Ca(OH)2) was sprayed over the waste as aevaporation promoter, the radiocaesium distribution to fly ash increased remarkably(distribution rate up 9.3% per 1% addition). However bentonite addition did not show any
evaporation prohibiting effect. We conducted additional tets to check the reproducibility
and facility dependence of hydrated lime’s radiocaesium evaporation effect. Hydrated
lime showed the evaporation effect again to some extent but not as remarkable as in thefirst test.
As to the co-incineration of used filter cloths contaminated with fly ash containing
radiocaesium with MSW, we confirmed that it is safe and proper treatment by managing
the co-incineration ratio appropriately.
We conducted testing on radiocaesium leaching from bottom ash and fly ash at 15
general waste incineration facilities in Fukushima Prefecture. Leaching of radiocaesium
from bottom ash was limited (below 1% to 16%). However, fairly high leaching rate (35%
to 94%) from fly ash was confirmed. In was confirmed that that the radiocaesium
concentration in ash and the leaching rate differ depending on the facility and that theseasonal variation of radiocaesium leaching from incinerated ash is small.
Zeolite and bentonite showed excellent ability to immobilize radiocaesium in fly ash. In
particular, zeolite showed high performance. When zeolite was added 20% to fly ash, theleaching rate decreased from 79% to 4.3%. This result implicates possible practical useof the material.

References
1) Hidetoshi Kuramochi (2013)“Incineration of waste contaminated with radioactive materials: Issues andscientific findings so far (research review)”, Safety Engineering，vol. 52，No. 5, pp282-290
2) Taku Iguchi and Takashi Kawano (2013) “Research on radiocaesium behavior during waste incineration”,
Proceedings of the Second Research Meeting of the Society for Remediation of Radioactive
Contamination in Environment - p141, 2013
3) Kenichi Harada, Kouga Fukushima, Hidetoshi Kuramochi, Makoto Otake, Shinichi Sugita, and Toru
Yamaki (2014), “Demonstrated Incineration of Grasses Contaminated by Radioactive Material”,
Proceedings of the 35th Japan Wastw Management Association Meeting, V-103
4) Mitsuhiro Tada, Yohei Tomita, Yasuhiro Miyakoshi, and Eiichi Shibuya (2013) “Cesium behavior in theincineration process and development of volatilization prevention technology” Proceedings for the Second
Research Meeting of the Society for Remediation of Radioactive Contamination in Environment - p65
5) Masaki Takaoka (2013) “Measurement of radioactive materials in flue gas at waste incineration facilities”,
Journal of Japan Society of Material Cycles and Waste Management, Vol.24, No.4, pp258-266
6) Toru Kameo, Naoki Maruyama, and Nobukazau Sano (2003), and Clean Authority of Tokyo, “Regarding
the disposal of waste filter cloths from bag filters”, Cleaning Technology Report (Clean Authority ofTokyo), No. 3, pp57-63
7) Eiichi Wakaizumi (2008), “Regarding the incineration disposal of Tefaire® filter cloths at incineration
facilities” Cleaning Technology Report (Clean Authority of Tokyo), No. 8, pp15-19
8) Shinichi Yamasaki, Hirofumi Yoshita, Hitoshi Suzuki, Minako Kamota, Hidetoshi Kuramochi, Kazuko

68 |Yui, Minoru Okoshi, Nobuyuki Odawara, and Atsushi Fujimagari (2016), “Regarding the result of surveyof radioactive material migration to bottom ash and fly ash under combustion temperature controlled
incineration”, Proceedings of the 37th Japan Waste Management Association Meeting, V-3-123
9) Hirofumi Yoshita, Koki Kokubun, Naoharu Murasawa, and Shinichi Yamasaki (2017), “Regarding theresult of demonstrative coincineration test of waste bag filter cloths with municipal solid waste”,
Proceedings of the 37th Japan Waste Management Association Meeting, V-3-122
10) Waste Management and Public Cleansing Law (Law No. 137 of 1970)

| 69

Contents of major support received from the IAEA
1. FIP1 Survey of radionuclide movement in river systems
・Provision of the TODAM model, a numerical simulation of contaminant migration in a river network,for the quantitative estimation of radionuclides deposited in rivers.
・Technical guidance on the selection of monitoring points and monitoring items, with an emphasis on
the importance of continuous monitoring at each monitoring point, based on previous studies ofChernobyl and Mayak.
・Advice about the operation of TODAM model using the monitoring data by the prefecture, that is, theimportance of measuring the Kd value (solid-liquid distribution coefficient) and sediment particle size
distribution at each observation point, as well as ion concentrations in rivers.
・Advice about the effectiveness of combining wide-area monitoring and simulation models, and theimportance of including small lakes as research subjects for improving our understanding of the
dynamics of radioactive materials in rivers.
・Advice about the need to assess the impact of decontamination and analyzing data excluding artificial
effects.
・Support for on-site inspections concerning radionuclides monitoring in Ukraine, Germany, Slovakia,
and so on.

2. FIP2: Survey of radionuclide movement with wild life
・Provision of foreign literature describing the relationship between wild animals and radionuclides, suchas radionuclide migration to wild animals, including boars and deer, in various regions following theChernobyl nuclear disaster and changes in radiocaesium levels in the bodies of birds, such as theAmerican gallinule and American wood duck, at the Savannah River Ecology Laboratory.
・Provision of information about recent scientific results concerning the bioaccumulation of radiocaesium
and in vivo radiocaesium concentration measurement technology.
・Discussions of study results and data analysis methods, such as the potential for mushrooms to explaina higher radiocaesium concentration in wild boars than those in other taxa in Fukushima Prefecture,
based on observation that mushrooms (deer truffles) cause a high radiocaesium concentration in themuscle tissues of wild boars in Europe.
・Explanation of the impact of the Chernobyl disaster on wildlife animal groups in surrounding areas, thedynamics of wolves and other animals and survey methods to clarify these impacts.

3. FIP3: Countermeasures for radioactive materials in rivers and lakes
・Provision of information related to the environmental dynamics of radioactive materials in rivers andlakes.
・Provision of information related to global environmental remediation activities in rivers and lakes,
including the removal of radioactive materials (countermeasures against the discharge of radioactive
material from the heavily contaminated floodplain in the vicinity of the Chernobyl nuclear power

70 |plant, and countermeasures against the inflow of radioactive materials into the Kiev Reservoir).
・Facilitation of a visit to the Chernobyl accident site.
・Recommendation regarding the evaluation of a radiocaesium decontamination test in a riverside (e.g.,
selection of the study site, simulation before decontamination, particle size of sediment, and density ofthe plant community).
・Advice on the study of countermeasures against radiocaesium in riverside parks (investigation of thehistory of floods, dikes and dredging to prevent recontamination).
・Recommendations about the study of Fukushima prefectural residents' anxiety and issues related to thewater environment (including the age and sex of residents as factors).
・Support related to the preparation of published materials (papers).

4. FIP4: Developing of environmental mapping technology using GPS walking surveys
・ Provision of information about efforts made by various institutions, such as the United States
Environmental Protection Agency and Lawrence Berkeley National Laboratory, to perform local
radiation dose mapping.
・Suggestion that inverse-distance weighting (IDW) is more appropriate than Kriging as a means ofinterpolation for walking surveys using GIS and that the shielding effect of buildings and the like must
be considered.
・Advice to judge measurement conditions of walking surveys according to the conditions at eachmeasurement point, as uniform measuring conditions are not always necessary.

5. FIP5: Study of proper treatment of waste containing radioactive materials at municipal solid waste
incinerators
・Provision of information related to treatment methods employed in other countries for fly ash, treatment
methods employed in other countries for low-level radioactive waste (i.e. incineration, melting
treatment of metal, and plasma melting) and instruments for measuring the concentrations of radioactive
substances in waste.
・Technical advice about the incineration of general waste, such as the need for studies conducted fromthe perspective of the radiocaesium balance of payments, the importance of comparative analyses ofactual test data and model analysis results, and the need to optimize test conditions and assess wastequality.
・Advice about the importance of countermeasures against the generation of hydrogen fluoride in themixed incineration of bag filters (made from Teflon).
・Advice regarding the safety (e.g. exposure protection and management) of facility workers.
・Suggestion that reducing radiocaesium elution from fly ash is important for the margin of safety whenlandfilling fly ash.