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

Cooperation between
Fukushima Prefecture and the IAEA
INTERIM REPORT(2013 to 2020)【Fukushima Prefecture Initiative Projects】【Executive Summary】(Temporary translation)

March 2021
Fukushima Prefecture

1

Introduction
The Great East Japan Earthquake occurred on 11 March 2011. It was followed by the accident of Tokyo ElectricPower Company's Fukushima Daiichi Nuclear Power Plant1, and radioactive materials have been released into theenvironment which contaminated the land. Due to the contamination of the land and other relevant reasons, morethan 160,000 prefectural residents were forced to evacuate. About 38,000 residents have not been able to return
home, as of 2020 July, about 9 years after the disaster (Fukushima Prefecture’s website “Fukushima Revitalization
Station”; https://www.pref.fukushima.lg.jp/uploaded/attachment/403521.pdf).
In order for Fukushima Prefecture to recover from the severe and unprecedented nuclear disaster and create anenvironment where the residents can live with peace of mind in the future, it was necessary to respond at theaftermath by collecting knowledge and world-wide experience, so the prefecture decided to cooperate with theInternational Atomic Energy Agency (hereinafter referred to as the “IAEA”), which owns high-level nuclear-related
knowledge. In December 2012, a memorandum for cooperation was signed between the prefecture and the IAEA.
Based on the memorandum, an agreement relating to the fields of “radiation monitoring” and “decontamination”
was signed between the parties on the same day (projects based on this agreement is referred to as “FCPs; Fukushima
Cooperative Project”).
Subsequently in April and October 2013, agreements were signed for five projects (hereinafter referred to as “FIPs;
Fukushima Initiative Project”) as described below in a new framework in which these projects would be supportedby the IAEA for three years, and the FIPs started (hereinafter referred to as “previous Project”). In April and May
2016, they signed agreements for extending the FIP cooperation period (originally set at “until December 2017”)
expanding the range of their cooperation2.
The achievements of the FIPs conducted between April 2013 and December 2017 were compiled in the report on“Cooperation between Fukushima Prefecture and the IAEA – SUMMARY REPORT (2013 to 2017) [Fukushima
Prefecture Initiative Projects]” in March 2018 (hereinafter referred to as "previous report"). The previous report isavailable in a book form and also in the following website:
https://www.pref.fukushima.lg.jp/sec/298/iaeasummary2017.html
However, because remediation of the environment in the Prefecture was halfway through and the accomplishmentof the proposed projects required further support from the IAEA, the prefecture obtained in December 2017 the
IAEA’s agreement and signature for a continued support until December 2022 (hereinafter referred to as “thisProject”). This report is an interim report on activities from Fiscal Year (hereinafter referred to as “FY”) 2013,
focusing on activities from FY2018 to FY2019, excluding FIP4. FIP4 was completed in FY2015 and has not been
extended, so the previous report is reprinted with some wording revised and updated since FY2015.

1 The owner of the Fukushima Daiichi Nuclear Power Plant was renamed from Tokyo Electric Power Company toTokyo Electric Power Company Holdings, Incorporated in April 1, 2016.
2 In accordance with the change of the cooperation range, the names of some FIPs were changed.

2

List of themes for the Fukushima Initiative Projects (FIPs) (themes in parentheses are titles used until 2017.)
FIP 1 Survey, and evaluation of the effect, of radiocesium dynamics in the aquatic systems based on thecontinuous monitoring(Survey of radionuclide movement in river systems)
FIP 2 Survey of radionuclide movement with wildlife
FIP 3 Sustainable countermeasures to radioactive materials in freshwater system(Countermeasures for radioactive materials in rivers and lakes)
FIP 4 Development of environmental mapping technology using GPS walking surveys
FIP 5 Study of proper treatment of waste containing radioactive material(Study of the proper treatment of waste containing radioactive materials at municipal solid waste
incinerators)

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1. FIP1 Survey, and evaluation of the effect, of the effect of radiocesium dynamics in aquatic systems
based on the continuous monitoring
1.1. Purpose
As a result of the Fukushima Daiichi Nuclear Power Plant accident in March 2011, large amounts ofradioactive materials were released as fallout into the environment and deposited on prefectural land. Nine
years after the accident, the concentration of radiocesium in the rivers of Fukushima Prefecture has decreased
sufficiently. However, continuous monitoringof the effects of changes in the surrounding
environment on the transport of in rivers is
considered necessary. In the project, we havecontinued

to

study

the

dynamics

ofradiocesium in rivers, using direct monitoring
and TODAM model simulations. In addition,
we have examined the current status ofradiocesium microparticles in river water andsources of suspended radiocesium in rivers inFukushima Prefecture.
1.2. Content of implementation

Figure 1. Monitoring points used in this study:(a)Kuchibuto River Basin (b)Wide-area multipoint
survey and (c) Hirose River Basin
Amount of radiocesium deposition on ground surfaces(as of July 2, 2011) *Source: Results of the 3rd
aircraft monitoring by the Ministry of Education,
Culture, Sports, Science and Technology (2011)

Using monitoring networks established in theprevious project (Figure 1(a), (b) and (c)) , weobtained continuous data for turbidity and waterlevels, collected suspended solids (SS) using SS
sampler, and collected river water samples formeasurements of suspended and dissolved cesium137.

Years from the accident

Figure 2. Cesium-137 concentrations in river water(a) Suspended cesium-137, (b) Dissolved cesium-137

4

1.3. Results
Changes in the suspended and dissolved cesium137 concentrations in river water over time areshown in Figure 2. The concentration of radiocesiumin rivers has continued to decrease over time,
although the changes are not as marked as
immediately after the accident. Based on these data,
the effective environmental half-lives of suspended
and dissolved cesium-137 were estimated to beabout 2.8 years and 3.6 years (excluding the data in2011), respectively. It is estimated that the effective
environmental half-life of suspended cesium-137
immediately after the accident was 0.24 years in the
Abukuma River compared to 0.31 years in the Figure 3. Change in suspended cesium-137 concentration
over the course of decontamination
Pripyat River after the Chernobyl Nuclear Power
Plant accident. In the second year and beyond,the decreasing rate of the concentration ofsuspended cesium-137 has lowered to about 1/10of the initial rate in Fukushima. However, likejust after the accident, the values of effective
environmental half-lives are similar still (valuesof Fukushima are within the same range of thevalues of European rivers; 1 to 4 years).
To assess the detailed changes in suspended
radiocesium concentrations in rivers in response
to decontamination activities in basins, the data
for the Kuchibuto River Basin (Figure 1(a))
designated as a special decontamination area
after the nuclear accident were analyzed. During
the period of intensive decontamination activities
in the basin, suspended cesium-137 concentrations
decreased significantly at upstream monitoring
point in the basin (Figure 3). It is considered that

Figure 4. Simulation results of changes in cesium-137
concentrations during flood events using TODAM
model [Upper rows: Suspended cesium concentration,
lower rows: Dissolved cesium-137 concentration](high-water flow events from 16 August to 19
August 2016)

this decrease occurred in response to the increased
sediment runoff resulting from decontamination practices. The amount of runoff decreased after the completionof decontamination, but was still higher than before decontamination started.
For the model simulations, the Kuchibuto River Basin (Figure 1 (a)) has been added as an additional river
basin in this period of the project (i.e. in addition to the Hirose River Basin (Figure 1 (c)). Figure 4 shows thesimulation results for the changes in suspended and dissolved cesium-137 concentrations in river water underhigh-flow conditions in the Hirose River Basin. Although deviations were observed at some points, the general

5pattern observed in measured cesium-137 concentrations was reproduced.
1.4. Conclusions
In this project, continuous monitoring of the radiocesium concentrations in river water as well as future
predictions by the model has been undertaken. The findings indicate that the decreasing trend observed inradiocesium concentrations that was reported previously has been maintained. In addition, the decontamination
activities undertaken in the prefecture have had a marked effect on the concentration of suspended cesium-137
in river waters. The simulation results were refined under base-flow condition. In addition, the simulation was
carried out under high-flow condition. Finally, preparation for new surveys and monitoring have been started
in another basin.

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2. FIP2 Survey of radionuclide movements with wildlife

2.1. Purpose
The accident at the Fukushima Daiichi Nuclear Power Plant caused a widespread environmental contamination
by radioactive materials. Radionuclides have been detected in many wild animals and we have conductedstudies to understand the movements of radionuclides in the ecosystem to clarify radiocesium migration towild animals.
2.2. Content of implementation(1) Measurement of radionuclide concentrations in the muscles of wild animals
Cesium-137
concentrations
were investigated based on the
results of monitoring survey ofradionuclide concentrations in
the muscles of wild animals
such as wild boars and others inFukushima Prefecture.
(2) Long-term fluctuations ofcesium-137 concentrationsin the muscles of wild boars
and Asian black bears
The long-term fluctuations ofcesium-137 concentrations in
the muscle of wild boars andAsian black bears after theaccident were analyzed with alinear model.
(3) Genetic population
structure of wild boars
The MIG-seq analysis was
performed using wild boar DNA
to investigate the wild boar
genetic population structure in
Fukushima prefecture.

Figure 1. Cs-137 concentrations in the muscles of (a) wild boars
and (b) Asian black bears (in regions where they were captured)* Each dot indicates the measured value for each wild animal.

7

2.3. Results(1) Measurement of radionuclide concentrations in the muscles of wild animals
In Soso District, Ken-poku District and Ken-chu District where the cesium-137 deposition density on soils was
relatively high, many wild boars and Asian black bears captured in May 2011 to March 2020 were detectedwith high cesium-137 concentrations,. This trend suggested that there was a correlation between cesium-137
concentrations in muscle of these species and the amount of cesium-137 deposition on soil. On the other handin Ken-chu District, some wild boars showed cesium-137 concentrations lower than the detection limit although,those showing cesium-137 concentrations close to 10,000 Bq/kg were also observed even in recent years (Figure
1).
(2) Long-term fluctuations of cesium-137 concentrations in the muscles of wild boars and Asian black
bears
With regard to cesium-137 concentrations in the muscles of wild boars, a decreasing trend was observed during
the entire period, in both the low-concentration period (April to August) and high-concentration period(December to March). However, the rate of decrease was small, and the cesium-137 concentrations estimatedfrom a regression line showed a wide range in the high-concentration period. As for A decreasing trend ofcesium-137 concentrations in the muscles of Asian black bears was also observed during the entire period andin the low-concentration period (July to September), but the range of estimated values widened over time during
the high-concentration period (November to January) (Figure. 2).

Figure 2. Long-term fluctuations of Cs-137 concentrations in the muscles of(a) wild boars and (b) Asian black bears

8(3) Genetic population structure of wild boars
DNA was extracted from the muscle tissue of
wild

boars

Kumamoto

capturedin

Prefectures.

Fukushima

andSingle-nucleotide

polymorphisms (SNPs) were obtained fromgenome-wide regions by MIG-seq method. The
results of the STRUCTURE analysis data for wildboars suggested that they were divided into two
genetic lineages (Figures 3 and 4). The results ofcluster analysis revealed two clusters that can bedivided into an eastern group inhabiting northern

Figure 3. Grouping of specimens after their
MIG-seq analyses and the number of analyses

Soso District, southern Soso District, Iwaki
District and Ken-nan District of Fukushima Prefecture, and a western group inhabiting Ken-poku District,Ken-chu District and Aizu District of Fukushima Prefecture and Kumamoto Prefecture (Figures 3 and 5).
Moreover, the results of the detection rates of two genetic lineages in each city, town and village inFukushima Prefecture suggested that these lineages are divided by the east and west area along with
Abukuma River as the boundary that restricted the movement to east and west (Figure 6).

Figure 4. Results of STRUCTURE analysis based on wild boars’ DNA data

Figure 5. Results of cluster analysis based on wild boars’ DNA data

9

Figure 6. Geographical distribution of wild boars of two genetic lineages

2.4. Conclusions
High cesium-137 concentrations of muscle were observed in wild boars and Asian black bears captured in areas
where the cesium-137 deposition density was high, but the concentrations significantly varied among individuals in
the areas. Even in recent years, high cesium-137 concentrations of muscle were observed.
The long-term fluctuations of cesium-137 concentrations in the muscles of wild boars and Asian black bears,
decrease over time during the entire period and in low-concentration periods. but during the high-concentration
periods, the range of estimated values increased over time.
Genetic analysis of wild boars in Fukushima Prefecture suggested that they were divided into two genetic lineages
and these genetic populations divided by east and west area along with Abukuma River and around as the boundarythat restricted the movement to east and west.

Cesium-137 concentrations in muscles of wild boars and Asian black bears were on a decreasing trend, butthey varied among individuals and fluctuated seasonally. Therefore, in order to precisely estimate their longterm fluctuations, further data expansion is necessary. Moreover, the movement and dispersion of the wild
animals seem to be a factor contributing to the variation of cesium-137 concentrations observed even among
those captured in the same region.
In the future, the monitoring of radiocesium concentrations in the bodies of wild boars and others will be continued,
and the factors contributing to the high radiocesium concentrations in some wild animals will be investigated.

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3. FIP3 Sustainable countermeasures to radioactive materials in freshwater system
3.1. Purpose
Radioactive materials (mainly radiocesium) spreading in the environment due to the accident at the
Fukushima Daiichi Nuclear Power Plant had contaminated the water environment. As a response, monitoring
surveys on water, deposited materials and aquatic products were conducted to clarify the behavior ofradioactive materials, and decontamination and some other measures were taken by administrative agencies
and research institutions. In this project that lasted until December 2017, applicable radioactive material
countermeasures were organized based on the existing knowledge accumulated domestically and abroad. A
decontamination test was also performed at a river where limited decontamination measures were taken,
thereby clarifying the effectiveness of sustainability of decontamination. In addition, contamination situations
were surveyed targeting public riverside areas in Fukushima Prefecture. The results of these surveys wereshown in a previous report. However, flood can cause the erosion and deposition of sediments containing
radioactive materials and change the contamination situation at the river. This could raise the concern of recontamination of these public areas. For this reason, in 2018 and onward, the sustainability of decontamination
effect on riverside areas where the decontamination test has been performed and was continuously checked,
and the contamination situations and changes in air dose rate at riverside parks due to large flooding causedby typhoon No. 19 (Hagibis) in 2019 were investigated.
3.2. Content of implementation(1) Verification of the sustainability of decontamination effect on riverside areas under the vegetation
At the riverbank where the decontamination test was conducted in 2014, air dose rates and radioactive
concentrations in sediments were measured under the vegetated condition to check the re-contamination.
(2) Changes in contamination situation in riverside area due to large flooding
At riverside areas and riverside parks (three points in total) where surveys had been conducted in the past,changes in the air dose rate and the situations of the parks after the passage of typhoon No. 19 (Hagibis) in2019 were investigated.
3.3. Results(1) Verification of the sustainability of decontamination effect on riverside areas under the vegetation
At the test site, air dose rates at both the decontaminated and non-decontaminated zones continued todecrease (Figure 1). In the decontaminated zone, a decontamination test revealed that the air dose rate halved,
and even after a weeding operation was stopped in 2017, the air dose rates continued decreasing. The rateof decrease in dose rate in the non-decontaminated zone was faster than that in the decontaminated zone.
The measuring of air dose rates after the decontamination test confirmed no re-contamination.
From the end of 2016 until August 2017, the radiocesium concentrations in newly-deposited materials that
accumulated on the flood channel with vegetation were higher than those without vegetation, but lower thanthose before the decontamination test. On the other hand, after typhoon No. 21 (Lan) in 2017, a 20 cm thicksediment deposited in the riverside area; however, its radiocesium concentration and mud ratio were low.
After one-year of vegetation recovery, a normal rainfall can cause the deposition of fine-grained sediment

11

which is trapped by the vegetation; however, the trapping effect of the fine-grained sediments is deemed tohave been small in large-scale flooding.

Figure 1. Changes in air dose rate at the Kami-Oguni River
Note: The physical dacay of radiocesium 134 and 137 was calculated with the initialdeposition ratio being 1:1. Initial values were fitted to the values measured
on November 16, 2014 after the completion of the decontamination test.

(2) Changes in contamination situation in riverside area due to large flooding
The air dose rates measured in all surveyed sites generally decreased after typhoon Hagibis (Figure 2). The
reduction rate was larger than that due to the physical decay of radiocesium and was greatly larger than that
following the typhoon No. 15 (Etau) in 2015. The survey results at riverside parks indicated that sedimentswith high radiocesium concentrations were partly flushed away along the river and that a large volume ofsand, pebble and gravel were deposited along the river channel. The loss of radiation sources due to sediment
outflow and a shielding effect due to covering by sand and gravels whose radiocesium concentrations were
low seems to have contributed to the reduction in the air dose rates.
This survey revealed that typhoon No. 19 (Hagibis) in 2019 did not cause re-contamination in general;
rather, it was confirmed that natural attenuation has caused the decreased air dose rates.

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Figure 2. Air dose rate distribution in a riverside park [(a) after the passage ofTyphoon No. 19, (b) before its passage]
Note: Background photograph (a) is a satellite image taken by the Cabinet
Intelligence and Research Office on October 17, 2019. Background photograph(b) was obtained from Google Earth Pro (date of the photo: October 21, 2018).

3.4. Conclusions
At the riverside site where the decontamination test was performed in 2014, the persistence of thedecontamination test was confirmed. Air dose rate decreased with time even on the vegetated flood channel.
An increase in radiocesium accumulation on the flood channel was not observed. These results show thepersistence of the decontamination test.
In order to investigate the re-contamination in the riversides due to the passage of typhoon No. 19 (Hagibis)
in 2019, air dose rate and the situation of the sites were investigated at riverside parks etc. Air dose rate did
not increase in general; rather, a large decrease in the air dose rate along the riversides and the effect ofnatural attenuation due to flooding were observed.

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4. FIP4 Development of environmental mapping technology using GPS walking surveys
4.1. Purpose
To understand the air dose rate in
Fukushima

Prefecture

after

the

accident at the Fukushima Daiichi
NuclearPower

Plant,

we

haveconducted air dose rate measurements
employing a variety of methods, andhave provided information on our
homepage.
However, it is difficult to conduct
fixed-point measurements or carborne

surveysinsomeplaces,Range where air dose rate can be understood with traveling surveys and fixed point
measurement

including parks, forests, and alleys

Range subject to walking surveys

near residential areas. We therefore

Figure 1. Measurement range of walking surveys

developed environmental mapping
technology using GPS walking surveys (hereinafter, simply referred to as walking surveys) to interpolate otherforms of monitoring.
4.2. Content of implementation(1) Development of equipment
We used the KURAMA (Kyoto University RAdiation MApping
System)-II, which was developed by Kyoto University, for walking

surveys. KURAMA-II is a system that can combine data obtained
from a radiation detector and GPS device to map air dose rates.
We used a high-precision GPS device and stored the equipment
in a backpack in a way suited to walking surveys. A manual was
prepared so that even inexperienced people can use the system.
We also developed a GIS data processing system for mapping the

Figure 2. View of a walking survey

measured results.
(2) Gathering parameters necessary for walking surveys
Because shielding from the measurers themselves affects the contribution from the radiation source
depending on the walking direction in walking surveys, we checked the direction characteristics.
We assumed measurements made with a NaI (Tl) survey meter at a height of 1m to be the most reliable, andthe survey meter was calibrated with traceability. To determine correction factors of walking surveys in acomparison test with survey meters, we compared measurement data made using a survey meter with thoseobtained in a walking survey.
(Note: Reprint of the executive summary of the previous report with some wordings revised and update added since the theme
ended in FY2015).

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4.3. Results
Results for the direction characteristics indicate that the impact of direction characteristics on a measured
value of a walk survey was considered small. Additionally, in our comparison with NaI (Tl) survey meters, wefound that it is necessary to use different CsI detectors for low and high air dose rates with 1 µSv/h as thedividing line.
In light of this, we set the correction factors to 1.3 when using a low-air-dose-rate detector and 1.1 when using
a high-air-dose-rate detector.
4.4. Conclusions
Results were obtained in developing walking surveys by 2015, making it possible to measure the air dose rate
in a walking survey.
In FY2016, we conducted walking surveys or lent the necessary equipment at the request of municipalities.
In recent years, walking surveys have been utilized in the public projects for monitoring of the air dose rates(e.g., Satoyama Restoration Model Project).

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5. FIP5 Study of proper treatment of waste containing radioactive material
5.1. Purpose

The incineration of municipal waste containing radiocesium scattered from the accident at TEPCO’s
Fukushima Daiichi Nuclear Power Plant resulted in the migration of radiocesium to bottom ash and fly ash.
Because radiocesium in fly ash in particular is likely to elute upon contact with water, there is a concern thatafter it is put in landfill, it will contaminate the surrounding environment by radiocesium. Therefore, it is anurgent task to properly treat and disposal of the bottom ash and fly ash contained in it.
Based on understanding of the characteristics of radiocesium elution from bottom ash and fly ash, thetechnology to suppress radiocesium elution by utilizing clay minerals has been studied. Moreover, at the
Fukushima Prefecture’s landfill disposal sites that have started the landfill of incineration ash containing
radiocesium, a correlation between a disposal site structure and radiocesium concentrations in leachate(seeping water) is being investigated.
5.2. Content of implementation(1) Tests on radiocesium elution suppression
Radiocesium concentrations and Cs elution rates in pure water were measured for bottom ash, humidified
bottom ash (treated bottom ash), fly ash, and fly ash subjected to heavy metal elution prevention treatment(treated fly ash); each of these were sampled from municipal waste incineration facilities in Fukushima
Prefecture. In addition, acid clay, which is expected to be effective as a radiocesium elution suppressor, wasadded to the incineration ash, and the measurement of radiocesium concentration in eluate (effluent) from theash and the analysis of element concentration were carried out.
(2) Tests on radiocesium elution suppression in incineration ash at municipal waste incineration
facility
The feasibility of radiocesium elution suppression by zeolite, which was found effective in suppressing
radiocesium elution from the incineration ash in previous studies, was verified by conducting zeolite addition
tests at municipal waste incineration facilities.
(a) A test during normal operation
Using incineration ash obtained during the normal operation of municipal waste incineration facilities,
radiocesium concentration measurements, radiocesium elution tests, and radiocesium elution tests with theaddition of zeolite were carried out.
(b) Tests on zeolite addition to an exhaust gas treatment agent at actual facilities
At the waste incineration facilities mentioned in (a), an exhaust gas treatment agent was mixed with zeolite
before the operations of the facilities, and the post-operation exhaust gas was analyzed and the treated fly ash
was sampled. Using the sampled treated fly ash, the radiocesium concentration measurements and radiocesium
elution tests were carried out.
(c) Tests on zeolite addition to the mixture of fly ash and chelate agent by kneading at actual facilities
At the municipal waste incineration facilities mentioned in (a), during a treatment for suppressing heavy metalelution from fly ash by using a chelate agent, zeolite was added and then the facilities were operated.
Subsequently, the treated fly ash was sampled. Using the sampled treated fly ash, a radiocesium concentration

16

measurement and a radiocesium elution test were carried out.
(3) Situations of landfill and radiocesium elution
Investigations were conducted at landfill disposal sites in Fukushima Prefecture to investigate correlations
between radiocesium concentrations in leachate and the situations of the incineration ash landfill.
(4) Correlation between the annual elution situation of radiocesium and other elements
Leachate was sampled once a month from the landfill disposal sites where radiocesium had been detectedin leachate, and the concentrations of radiocesium and other elements were analyzed.
5.3. Results(1) Tests on radiocesium elution suppression
Regarding radiocesium concentrations in incineration ash, those in fly ash and treated fly ash were higher
than those in bottom ash and treated bottom ash. Radiocesium elution rates were also higher for fly ash andtreated fly ash than bottom ash and treated bottom ash. Long-term elution tests in which fly ash was mixed
with a heavy metal elution suppression agent (chelate agent) and acid clay indicated that the acid clay has aradiocesium elution suppression effect (Figure 1) and does not block the heavy metal elution suppression
effect of the chelate agent.

Figure 1. Results of radiocesium elution suppression tests (radiocesium elution rates)(2) Tests on radiocesium elution suppression in incineration ash at municipal waste incineration
facilities(a) A Test during a normal operation
An elution test using incineration ash sampled during the normal operation indicated that the radiocesium
concentration and radiocesium elution rate were higher for fly ash than they are in the bottom ash.
Repetitive elution tests conducted on the same samples indicated that the radiocesium elution rate at the

17first test was the highest (Table 1 and 2). Furthermore, based on comparison with the elution test in which
zeolite was added to fly ash and to the treated fly ash, it was concluded that zeolite suppresses radiocesium
elution and that zeolite addition do not block the heavy metal elution suppression effect of chelate agent.

Table 1. Results of repetitive elution tests
using bottom ash (during normal operation)

Table 2. Results of repetitive elution tests using
treated fly ash (normal operation)(b) Tests on zeolite addition to an exhaust gas treatment agent at actual facilities
An exhaust gas treatment agent and zeolite were mixed and injected (by blow injection) into exhaust gas at
waste incineration facilities. As a result, the mixture neither negatively affected the exhaust gas nor blocked
the heavy metal elution suppression effect of chelate agent and was able to suppress the radiocesium elution
caused by contact between treated fly ash and water.
(c) Tests on zeolite addition to the mixture of fly ash and chelate agent by kneading at actual facilities
When zeolite was added to chelated fly ash, the kneaded mixture did not block the heavy metal elution
suppression effect of the chelate agent and it suppressed radiocesium elution to the same degree as the blow
injection mentioned above.
(3) Situations of landfill and radiocesium elution
As a result of investigating the situations of incineration ash landfill and radiocesium concentrations inleachate at landfill disposal sites, no radiocesium was detected from the leachate of the sites where only bottom
ash was landfilled, and radiocesium was detected from leachate of the sites where fly ash was landfilled incontact with water in the same way as before the accident and also at some landfill disposal sites where fly ash
was landfilled without contact with water.
(4) Correlation between the annual elution situation of radiocesium and other elements
When radiocesium concentrations in leachate were measured at four landfill disposal sites where radiocesium
had been detected from leachate for two consecutive years, no common seasonality trend in radiocesium
concentration was observed (Figures 2 and 3). In addition, no seasonality in radiocesium concentration wasobserved in any disposal site.

18

Figure 2. Measurement results in FY 2017

Figure 3. Measurement results in FY 2018

Regarding a relationship between theconcentrations of radiocesium and otherelements, a positive correlation wasobserved between radiocesium elution
concentration and chloride ion elution
concentration (Figure 4). This suggests
the possibility that the chloride ion
concentration in incineration ash and thelevel of chloride ion elution affect theradiocesium elution.

Figure 4. Correlation between radiocesium and chloride ion concentrations

5.4. Conclusions
In order to study methods for treating, disposing of, and managing radiocesium-containing fly ash generated
in the prefecture, we conducted investigations and tests at landfill disposal sites and waste incineration facilities.
As a result of investigating leachate, we found that the landfilling of fly ash in contact with rainwater causes
radiocesium elution from the fly ash, resulting in radiocesium being detected from leachate.
In order to suppress radiocesium elution from the fly ash, we conducted elution tests using incineration ash
as well as tests for suppressing radiocesium elution from the incineration ash in laboratory and landfill disposalsites. As a result, we found that the addition of zeolite to incineration ash significantly suppresses radiocesium
elution. However, the application of these methods to actual disposal facilities requires the consideration of thecharacteristics of each incineration facility and landfill disposal site, including consideration of an increase in theamount of landfill disposal due to zeolite addition as well as facility structure and capacity.