Dose assessment for the future use of the former temporary storage sites

1. Introduction
In March 2011, the accident at TEPCO's Fukushima Daiichi Nuclear Power Station caused
radioactive materials to be dispersed, contaminating large areas of Fukushima and other parts ofeastern Japan. In order to recover the environment from radioactive contamination,
decontamination work is being carried out in the living areas mainly in accordance with “Act on
Special Measures concerning the Handling of Pollution by Radioactive Materials”. As shown in
Figure 1, decontamination in Fukushima Prefecture is carried out in two main categories: thespecial decontamination areas (SDA) where the national government formulates adecontamination implementation plan and decontamination projects are carried out, and theintensive contamination survey areas (ICSA) where municipalities formulate a decontamination
implementation plan and decontamination projects are carried out. Whole area decontamination
based on the Act on Special Measures was completed by March 2018, excluding the areas wherereturning is difficult in SDA.1
The soil and waste removed in Fukushima Prefecture as a result of decontamination activities
are stored at temporary storage sites (TSSs), etc., and then transported to Interim Storage Facility,
where they will be safely and centrally managed and stored until final disposal is performed
outside Fukushima Prefecture. After the soil and waste has been removed from the TSS, the TSS
will be restored to their original condition based on the land-use before the TSS was created (Landfeature will be restored.) During the restoration work, it is checked that there is no obvious
contamination due to the storage by the measurement of the air dose rate by the manager of the
TSSs (mainly local municipalities) before the return to the landowners. If contamination is
confirmed, decontamination should be carried out following the guidelines established by the
Ministry of the Environment.2, 3
When the TSSs are returned to the landowners after restoration, the results of exposure dose
assessment in the TSSs can be presented to the landowners to effectively certify the present day
safety of the TSSs. Considering the role of Fukushima Prefecture for supporting the municipalities,
it is particularly important to assess the current and potential future additional exposure doses
from use of the land at the former TSSs in ICSA.
This study establishes a method to assess the additional exposure dose associated with thepotential future use of the former TSS after restoration. Various potential land-uses, assessment
scenarios, calculation models and parameters were examined, and the additional exposure dose
per unit concentration of radioactive cesium (1 Bq/kg) was calculated. These results can then be
used to assess the additional potential future dose at each TSS according to the concentration ofradioactive cesium in soil at site. Uncertainty in the level of additional dose was assessed bycomparing the results of calculations using average values for parameters such as exposure time1and food intake with those using conservative values. Furthermore, the additional exposure doses
were calculated on a case study basis using the measured cesium concentration values and air
dose rates in the topsoil of the actual TSS, and compared with 1 mSv/year *1 which is the target
value of the additional exposure doses.
After describing the background of the assessment and information on the TSS and its restoration,
the assessment scenarios were examined and assessed considering various possibilities. Reference
is made to the IAEA document, General Safety Guide No. GSG-34 (hereinafter referred to as"GSG-3") and Safety Guide No.WS-G-5.1 5(hereinafter referred to as "WS-G-5.1").

GSG-3

provides recommendations to meet the safety requirements of the IAEA document General Safety
Requirements Part 56. GSG-3 states that the reliability of the assessment results can be improvedby combining the probabilistic and deterministic approaches. However, in order to use aprobabilistic approach, it is necessary to understand the probability distribution of the parametervalues, but such data are not available. Therefore, although this study did not undertake aprobabilistic approach, the reliability of the assessment was improved by assessing the exposure
dose using parameter values such as mean values and evaluating the effect of the uncertainty inthese parameter values by considering their variability. The flow diagram of this study is shownin Figure 2.

SDA
ICSA
Former SDA
Former ICSA

Names of municipalities in the former SDA or ICSA

Figure 1. ICSA in Fukushima Prefecture 7

2*1 The basic policy based on the Law Concerning Special Measures against Radiation Contamination states that thelong-term goal is that the additional exposure dose (exposure to artificial radionuclides) should be less than 1
mSv/year. This is the same value as the ICRP recommended public exposure dose limit of 1 mSv/year.

Figure 2. Flow diagram of dose assessment in the present study
2. Design, safety measures and restoration of TSS
The TSSs for removed soil and waste are designed and managed in accordance with theguideline2 established by the Ministry of the Environment. In the guideline, in order to achieve
the safe storage of the removed soils and wastes, the TSS has seven facility requirements for thesafe storage: 1) shielding and isolation, 2) prevention of dispersion of the removed soil and waste,3) prevention of penetration of rainwater, etc., 4) prevention of outflow of the removed soil, waste
and radioactive materials, 5) prevention of effect from substances other than radioactive materials,
6) resistance to earthquake, etc., 7) other necessary measures, and three management
requirements: 1) restriction of entry, 2) monitoring the radiation dose and carrying out repairs, 3)
keeping records. Figure 3 shows the design and structure of a typical above-ground TSS. At TSSs,
the measurements of air dose rates and other data are carried out before the beginning of thestorage of the removed soil and waste, during storage and after the stored soil has been removed.
The distribution on the area size of TSSs in ICSA is shown in Figure 4. Over 60% have areas
between 1,000 m2 and 10,000 m2. The information on the size and the land use before the land
was developed as the TSS is shown in Table 1 and it was mainly used as agricultural land (e.g.
paddy field or field), forest or park.
The transportation of the removed soil and waste from the TSSs to the Interim Storage Facility
and their restoration are still in progress. The return of the land of former TSS to the landowners
has already been completed at many sites in Fukushima Prefecture. Figure 5 shows the numberof TSSs in the ICSA.
3Container with removed soil and waste
Container with uncontaminated soil for shielding
Water barrier sheet* Required if combustible waste is included.
Heat and gas discharge
tubes

Hole to monitor groundwater.

Water barrier sheet

Water collection tank.

Source: Decontamination information website - Temporary storage area
Figure 3. Basic design and structure of TSS 880%80

Number of TSS [%]

60%
60

40
40%

20
20%

0
0%
0

1

10

2

100

3

1,000

4

10,000 5 100,000 6 1,000,000

area size [unit: m2]

Source: Decontamination Countermeasure Division Fukushima Prefectural Government

Figure 4

Area size distribution of TSSs for ICSA in Fukushima Prefecture4

Table 1. Original land-use and area size of TSSs in ICSA
original land-use

area size [unit: m2]

Number of TSS with known
original land use and area sizemeanminimum

maximum

Paddy

232

8,511

182

129,079

Cropland

282

5,333

10

55,853

Pasture10

54,371500

363,000

Forest104

11,77515

122,000

Park

70

1,828

9

20,000The other122

10,48415

360,871

821

8,204

9

363,000(parking lots, etc.)
Total

Source: Decontamination Countermeasure Division Fukushima Prefectural Government

1000

927
822

Number of TSSs

800

600

400

171

200

0
0
2014/3

4
2015/38
2016/312
2017/316
2018/320
2019/324
2020/328
2021/332
2022/3Figure 5. Number of TSSs of ICSA in Fukushima Prefecture over time 9
The restoration of the TSSs is carried out in accordance with the guidelines 2, 3 established by
the Ministry of the Environment. When the movement of the stored soil and waste has been
completed, the TSSs will be restored to the original state*2 following the process shown in Figure
6 and returned to the landowner.
The restoration of the TSSs is basically to restore the original land state before the TSS. That is,where the shape of the land was changed to enable its usage as a TSS, it will be returned to its
previous shape. In addition, the function of the land will be restored so that the usage of the land*2
will not be hindered.
Although the TSS is designed to prevent contamination of the topsoil with radioactive materials,
under the incidental event of a leak of radionuclide during transport or storage of removed soil
5
*2 The land use may be changed to a different land use than before the TSS was established, dependingon the wishes of the land owner.

and waste, the topsoil might become contaminated with radionuclides. After the removal of soil
and waste from the TSS and the removal of the structures of the TSS, the air dose rates and/or
cesium concentrations in topsoil are measured to confirm that there is no local contamination of
the land. The measurement points are basically the centre position of the area where the soil andwaste placed and one point at each of the four corners of the TSS. If there are multiple the areas
within one temporary storage area, measure the center and four corners of each.
Determine the presence or absence of contamination by comparing measurements taken after
soil removal with measurements taken before TSS establishment, during management of its or on
the surrounding decontaminated land of the same land-use. If localized contamination is found,
topsoil removal, etc. should be performed by the Municipality. After all restoration work iscompleted, air dose rates, and/or cesium concentrations in topsoil are measured again.
All results of the air dose rate and other measurements are recorded and presented when the land
is returned to the landowner after the restoration is completed.
In the flow diagram of restoration of the TSS shown in the guideline2 established by the Ministryof the Environment, the measurement of the air dose rates is supposed to be conducted. Although
the additional exposure assessment is not included.

Flow diagram of restoration of TSS
Removal of soil and waste from TSS(1) Confirmation and organization of
conditions.

Determining the shape of the land after restoration andthe construction method *Original topography and landforms,
changes due to the creation of the TSS.

(2) Removal of structures, etc.

Plans for use of the former TSS site,plans to resume farming, etc.

(3) Investigation after removal of the structure
Confirmation of the effects of the creation of TSS (local
contamination by radionuclides, ground subsidence,
consolidation, hardening, etc.)* When making
determinations, consult
and confirm with thelandowner.

Decide on specific restoration details, construction methods, etc. *(4) Construction of restoration works (restoration of topography and features etc.)(5) Measurement of air dose rate after restoration and confirmation of thequality of the resoration (in the presence of the landowner)

Return of land

Figure 6. Flow diagram of restoration of TSS 2
3. Assessment model
3.1. Target persons and period for assessment
The target of the assessment is future users of the former TSS site in ICSA. Since the values of6dose conversion factors, food intake, exposure time, etc. differ depending on the age of the users,
the age groups of the target persons were divided into adults (over 20 years old) and minors, andthe minors were subdivided into 1-6 years old, 7-14 years old and 15-19 years old. The assessment
was conducted using the appropriate parameter values for each age group. Due to radionuclide
decay, the radionuclide concentrations in the environment will generally decrease with time. The
exposure of people to radionuclides will depend both on the concentrations of radionuclides andthe activities of the people at the former TSS. For example, forestry work may cause people toreceive varying exposures with time and the maximum exposures may not occur at the start of theassessment period. For these reasons we have assessed the factors that could lead to exposure
doses to be higher in some years.
3.2. Assessment scenarios
As recommended in GSG-3 and WS-G-5.1, the assessment scenarios were developed in orderto perform the exposure dose assessment. In addition, since it is stated that potential hazards
should be considered in the assessment scenarios, various possibilities were considered.
In order to create an assessment scenario according to the land use of the former TSSs, the land
use which could be considered in the former TSS was examined. The TSSs are basically restored
to the land-use and shape prior to the installation, but may be changed to a different shape than
before depending on the intentions of the land owner. Therefore, not only the conventional landuse of agricultural land, forest, park and parking lot, but also other potential land-uses such as
housing, factories, commercial facilities, and material storage areas were considered as shown in
Figure 7 .

Figure 7: The land-use assumed for the former TSS
7

The agricultural land scenario was categorized into paddy, cropland, pasture and orchard
scenarios. The cropland scenario was subdivided into two scenarios: a vegetable scenario with
the internal exposure due to food intake and a flower scenario with long working hours leading
to external exposures. The pasture scenario was subdivided into two: milk cow and beef cattle.
For the forest scenario, managed forest and natural forest scenarios were considered, but only the
managed forest scenario was assessed because it takes a very long time for the former TSS to
become close to a natural forest condition, and the radionuclides are undergoing radioactive decay
during that period. Among other land uses, for buildings, residential areas (houses, etc.), placesof employment (factories) and commercial facilities were considered, but only the scenario of
housing was assessed because the exposure time of persons would be the longest. For the “nonbuilding” scenarios, park, parking lots and material storage areas were considered, but only the
scenario of the park where the person's exposure occupancy time would be the longest wasassessed. These nine types of scenarios are shown in Table 2.
For each scenario, the exposure pathways depending on the land-use are defined by the Atomic
Energy Society of Japan (AESJ) Standard Safety Assessment Methodology for Shallow
Subsurface Disposal: 2016 10 (hereinafter referred to as the "AESJ Standard") and the IAEA Safety
Reports Series No. 44 11 (hereinafter referred to as "SRS No. 44"). Common exposure pathways
which were included for all scenarios were: the external exposure during activities and occupationof the former TSS, the internal exposure due to unintentional ingestion of soil at the former TSS,
and the internal exposure due to inhalation of soil and dust generated from TSS. Regarding theinternal exposure due to the intake of food from the former TSS, the intake of crops in the Paddy
scenario, the Cropland (vegetable) scenario, and the Orchard scenario, the intake of milk in the
Pasture (milk cow) scenario, and the intake of crops from kitchen garden in the Residence
scenario were also included. Monitoring of drinking water (including well water) in Fukushima
Prefecture 12 has not detected radioactive cesium, therefore, exposure due to ingestion of waterfrom the former TSS was excluded from the assessment in the present study. An illustration of thedifferent exposure pathways is shown in Figure 8.
In the Pasture (beef cattle) scenario, the intake of beef from cattle that had grazed on the former
TSS was considered to be possible, but as slaughter is not allowed except in licensed
slaughterhouses under the law, it was judged that a farmer would not consume beef that grazed
on their former TSS. For that reason, the internal exposure due to the beef intake was not included.
It is known that there have been no cases of cattle being raised in barns built on the site of TSSs
(Source: Decontamination Countermeasure Division Fukushima Prefectural Government).
However, since it cannot be ruled out that there may be cases of cowsheds being built in the future,
the assumption of raising cattle on the site of the TSS was included in the Pasture (milk cow andbeef cattle) scenarios.
8In the forest scenario, the intake of mushroom and wild plants is possible but these are mainly
taken in natural forests 13. Therefore, the intake of mushrooms and wild plants from the former
TSS was excluded from the assessment in the present study.
Where the scenario considers adults working on the land, such as agricultural land and forest, it
is assumed that children may accompany the adult workers, so the above scenarios and exposure
pathways are set to be common to all age groups.
Table 2. List of land-use scenarios and respective exposure pathways
No.

Land-use

activity

Exposure pathway
1) External exposure of workers during rice cultivation
2) Internal exposure of workers due to ingesting the grown rice

1

Paddy

Grow and consume rice3) Internal exposure of workers due to ingestion of soil during ricecultivation
4) Internal exposure of workers due to inhalation of dust generated
during rice cultivation
1) External exposure of workers during vegetable cultivation
2) Internal exposure of workers due to ingesting the grown2

Cropland(vegetable)

vegetable
Grow and consume vegetables 3) Internal exposure of workers due to ingestion of soil during
vegetable cultivation
4) Internal exposure of workers due to inhalation of dust generated
during vegetable cultivation
1) External exposure of workers during flower cultivation3

Cropland(flower)2) Internal exposure of workers due to ingestion of soil during
Grow flowers

flower cultivation
3) Internal exposure of workers due to inhalation of dust generated
during flower cultivation
1) External exposure of workers during fruit cultivation
2) Internal exposure of workers due to ingesting fruit

4

OrchardGrow and consume fruit3) Internal exposure of workers due to ingestion of soil during fruit
cultivation
4) Internal exposure of workers due to inhalation of dust generated
during fruit cultivation

5

Pasture(milk cow)

1) Grow the pasture at TSS

1) External exposure of workers during raising milk cows

2) Feed the pasture to the milk 2) Internal exposure of workers due to consuming milk from cows
cow at the INSIDE of TSS

raised93) Consume the milk

3) Internal exposure of workers due to ingestion of soil during
raising milk cows
4) Internal exposure of workers due to inhalation of dust generated
during raising milk cows
1) External exposure of workers during raising beef cattle

6

Pasture(beef cattle)

1) Grow the pasture at TSS

2) Internal exposure of workers due to ingestion of soil during

2) Feed the pasture to the beef raising beef cattle
cattle at the INSIDE of TSS

3) Internal exposure of workers due to inhalation of dust generated
during raising beef cattle
1) External exposure of workers during forestry work

7

ManagedForest2) Internal exposure of workers due to ingestion of soil during
Forest management

silvicultural work.
3) Internal exposure of workers due to inhalation of dust generated
during silvicultural work.
1) External exposure during living indoors

1) living the house built at the
TSS
8Residence 2) manage kitchen
garden*3 and consume
the vegetable

2) External exposure during kitchen gardening
3) Internal exposure due to ingestion of vegetable grown fromkitchen garden
4) Internal exposure due to ingestion of soil during kitchen
gardening5) Internal exposure due to inhalation of dust generated during
kitchen gardening
1) External exposure while staying in the park
2) Internal exposure due to ingestion of soil while staying in the

9

Park

Stay at the park

park3) Internal exposure due to inhalation of dust generated whilestaying in the park

10
*3 Although there are many possible varieties of outdoor work on a residential property, kitchen garden wasconsidered representative for the assessment in the present study.

Figure 8. Illustration of potential exposure pathways
3.3. Calculation models and parameters
In assessing the additional exposure doses from the potential future use of the former TSSs, thecalculation models used are shown (Formula 1 to Formula 8, and these are based on the formulae
given in) derived from the AESJ Standard and SRS No.44. The internal exposure model for soil
ingestion, shown in Formula 3 is based on, the internal exposure model for food ingestion shown
in Formula 2. For the internal exposure model for soil ingestion in Formula 3, and also for themodel for the radionuclide transfer from soil to airborne dust shown in Formula 5, an additionalparameter was included to account for the tendency that the concentration of radionuclide tends
to increase as the particle size becomes fine - SRS No. 44.
Formula 1. External Exposure
𝐷𝑒𝑥𝑡 (𝑖) = 𝐶𝑠 (𝑖)𝑆𝑠 (𝑖)𝑡𝑠 𝐷𝐶𝐹,𝐸𝑋𝑇 (𝑖)𝐷𝑒𝑥𝑡 (𝑖)：External radiation dose from radionuclide i［Sv/year］
𝐶𝑠 (𝑖)：Radionuclide i concentration in soil［Bq/kgDW］
𝑆𝑠 (𝑖)：Radionuclide i shielding factor (screening factor) [-]𝑡𝑠 ：Exposure time (Annual activity time)［h/year］
𝐷𝐶𝐹,𝐸𝑋𝑇 (𝑖) ：Conversion factor of external exposure dose due to radionuclide i［（Sv/h）/（Bq/kgDW）］
Formula 2 internal exposure due to food ingestion
11

𝐷𝑖𝑛𝑔,𝑓 (𝑖) = 𝐶𝑓 (𝑖)𝑀𝑓 𝐺𝑓 𝐷𝐶𝐹,𝐼𝑁𝐺 (𝑖)𝐷𝑖𝑛𝑔,𝑓 (𝑖)：Internal radiation dose due to the oral intake of radionuclide i［Sv/year］
𝐶𝑓 (𝑖)：Radionuclide i concentration in food［Bq/kgFW］
𝑀𝑓 ：Annual amount of food intake［kgFW/year］
𝐺𝑓 ：Market dilution factor of food [-]𝐷𝐶𝐹,𝐼𝑁𝐺 ：Conversion factor of internal exposure dose due to the oral intake of radionuclide i［Sv/Bq］
Formula 3 Internal exposure due to soil ingestion
𝐷𝑖𝑛𝑔,𝑠 (𝑖) = 𝐶𝑠 (𝑖)𝑓𝑐,𝑠 𝑀𝑠 𝑡𝑠,𝑖𝑛𝑔 𝐷𝐶𝐹,𝐼𝑁𝐺 (𝑖)𝐷𝑖𝑛𝑔,𝑠 (𝑖)：Internal radiation dose from radionuclides i due to the oral intake of soil [Sv/year]
𝐶𝑠 (𝑖)：Radionuclide i concentration in soil [Bq/kgDW]
𝑓𝑐,𝑠 ：Concentration factor of specific activity in the fine fraction for soil ingestion [-]𝑀𝑠 ：Soil intake per hour [kgDW/h]
𝑡𝑠,𝑖𝑛𝑔 ：Soil ingestion time in former TSS [h/year]
𝐷𝐶𝐹,𝐼𝑁𝐺 (𝑖)：Conversion factor of internal exposure dose due to the oral intake of radionuclide i[Sv/Bq]Formula 4 Internal exposure due to dust inhalation
𝐷𝑖𝑛ℎ (𝑖) = 𝐶𝑎 (𝑖)𝐵𝐴 𝑡𝑠,𝑖𝑛ℎ 𝐷𝐶𝐹,𝐼𝑁𝐻 (𝑖)𝐷𝑖𝑛ℎ (𝑖)：Internal radiation dose due to the inhalation of radionuclide i［Sv/year］
𝐶𝑎 (𝑖)：Airborne radionuclide i concentration［Bq/m3］
𝐵𝐴 ：Breathing rate［m3/h］
𝑡𝑠,𝑖𝑛ℎ ：Dust inhalation time in former TSS［h/year］
𝐷𝐶𝐹,𝐼𝑁𝐻 (𝑖)：Conversion factor of internal exposure dose due to the inhalation of radionuclide i［Sv/Bq］
Formula 5 Radionuclide transfer from soil to airborne dust in air
𝐶𝑎 (𝑖) = 𝐶𝑠 (𝑖)𝑓𝑐,𝑑 𝑑𝑅
𝐶𝑎 (𝑖)：Airborne radionuclide i concentration［Bq/m3］
𝐶𝑠 (𝑖)：Radionuclide i concentration in soil［Bq/kgDW］
𝑓𝑐,𝑑 ：Concentration factor of specific activity in the fine fraction for soil [-]𝑑𝑅 ：Airborne dust concentration［kgDW/m3］
Formula 6 Radionuclide transfer from soil to rice, vegetables and fruits
𝐶𝑉,𝑓 (𝑖) = 𝐶𝑠 (𝑖)𝑇𝑅,𝑓 (𝑖)𝐶𝑉,𝑓 (𝑖)：Radionuclide i concentration in plant［Bq/kgFW］
12

𝐶𝑠 (𝑖)：Radionuclide i concentration in soil［Bq/kgDW］
𝑇𝑅,𝑓 (𝑖)：Radionuclide i transfer factor (transfer from soil to agricultural product)［（Bq/kgFW）/（Bq/kgDW）］
Formula 7 Radionuclide transfer from soil to pasture
𝐶𝑉,𝑝 (𝑖) = 𝐶𝑠 (𝑖)𝑇𝑅,𝑝 (𝑖)𝐶𝑉,𝑝 (𝑖)：Radionuclide i concentration in pasture［Bq/kgDW］
𝐶𝑠 (𝑖)：Radionuclide i concentration in soil［Bq/kgDW］
𝑇𝑅,𝑝 (𝑖)：Radionuclide i transfer factor (transfer from soil to pasture)［（Bq/kgDW）（Bq/kgDW）/］
Formula 8 Radionuclide transfer from pasture to livestock product𝐶𝐶𝑎 (𝑖) = 𝐶𝑉,𝑝 (𝑖)𝑓𝑟 𝑀𝑔 𝑇𝐴𝑀 (𝑖)𝐶𝐶𝑎 (𝑖)：Radionuclide i concentration in livestock product［Bq/kgFW］
𝐶𝑉,𝑝 (𝑖)：Radionuclide i concentration in pasture［Bq/kgDW］
𝑓𝑟 ：Market dilution factor of feed [-]𝑀𝑔 ：Feed intake by livestock［kgDW/day］
𝑇𝐴𝑀 (𝑖)：Ratio of consumed radionuclide i transfer to livestock product［day/kgFW］
Assessment generally used the average parameter suitable for each age group (adults, 1-6 years
old, 7-14 years old, 15-19 years old) were used. For the dose conversion factors and transfer
factors, the values described in Satoh, et al. report 14 and the IAEA and ICRP documents 15, 16 wereused. For parameters for which the average value is unknown, the values described in the
documents 10, 17 of the Atomic Energy Society of Japan and Technical Reports Series No. 472 18 of
the IAEA were used. The parameter values used for the assessment are shown in Appendix A,
Tables A1-A10.
The radionuclides considered were cesium-134 and cesium-137, which have longer half-lives
than other radionuclides released in the Fukushima Dai-ichi nucler power plant accident and werereleased into the environment in large quantities according to the Japanese government’s reports
19. The abundance ratio of cesium-134 and cesium-137 was calculated from the Japanese

government’s reports, taking into account radioactive radioactive decay, starting from an assumed
a ratio of 1: 1 at the time of the accident.
The conversion factor of external exposure dose in Formula 1 depends on the depth distributionof radioactive cesium. The distribution of radioactive cesium in the soil of the TSSs depends onthe construction method of the TSS, the land use of the site and the time elapsed since the accident.
It is assumed that the depth distribution of radioactive cesium is exponentially distributed 20, 21 or
has a peak at some depth if there is no artificial mixing or agitation (e.g. digging, ploughing) 22.
When there is artificial mixing or agitation the concentration of cesium in the soil profile is13averaged 20.
When the radioactive cesium is exponentially distributed from the ground surface, theradioactivity concentration Am (ζ) (Bq/kg) at the mass depth ζ (g/cm2) is expressed by the
exponential equation 23 (9) according to the radioactivity concentration Am,0 (Bq/kg), the mass
depth ζ (g/cm2) and the relaxation mass depth β (g/cm2).
𝐴𝑚 (𝜁) = 𝐴𝑚,0 exp⁡(−𝜁/𝛽) ･････ (9)The mass depth⁡𝜁 is defined as the product of soil depth (cm) and density (g/cm3). The
relaxation mass depth β is a parameter representing the depth distribution of radioactive cesium,and the smaller the value, the more the radioactivity concentration is concentrated near the groundsurface. Kato, et al. report 21 that the relaxation mass depth β on land without artificial mixing justafter the accident becomes around 1 g/cm2. On the other hand, according to the investigation
conducted by the Nuclear Regulation Authority about 9 years after the accident, it is reported thatthe relaxation mass depth β was about 4 24. In this study, for calculating the exposure dose we
assumed that the cesium is at the surface of the soil and so we set the external exposure doseconversion factor⁡𝐷𝐶𝐹,𝐸𝑋𝑇 (𝑖) for the relaxation mass depth β to 1 g/cm2.
3.4. Assessment Method of additional exposure dose from the former TSS with unit
concentration of radioactive cesium

3.4.1. Assessment Method of using average and standard parameter values
The additional exposure dose per unit concentration of radioactive cesium in soil was calculated
based on the scenarios, models and parameters set out in Sections 3.1 to 3.3. Regarding theconcentration of radioactive cesium, the concentration of cesium-137, which has a long half-lifeand remains for a long time, was set to 1 Bq/kg as of June 2022. The concentration of cesium-134
was set to 0.03 Bq/kg in consideration of the radioactive decay that has occurred between theaccident and June 2022 assuming a ratio of cesium-134 to cesium-137 at the time of the accident
of 1.
However, in the Managed Forest scenario, the assessment results are presented for the logging
performed in the 45th year*4 after tree planting, considering the working time involved inharvesting and radioactive decay of cesium. The concentration of radioactive cesium after 45
years (June 2067) was calculated considering radioactive decay, and the concentration of cesium137 was set to 0.36 Bq/kg and the concentration of cesium-134 was set to 8.2×10-9 Bq/kg.
3.4.2. Method of uncertainty analysis
The GSG-3 states that consideration of uncertainty is essential in safety assessment. Uncertainty
exists in each of the assessment scenarios, models and parameters. As for the assessment scenarios,
14*4 The standard number of years it takes to grow and harvest a cedar tree in Fukushima Prefecture is 45 years
25, 26, 27, 28.

we considered that uncertainty was addressed because the scenarios covered various cases
considering various possibilities, and even if there is a change in land-use in the future, it would
be covered by the scenarios discussed in Section 3.2. In addition, since the models refer to the
AESJ Standard which are the documents of Japanese academic societies, and some of thecalculation formulas are conservatively modified by referring to the IAEA documents 11, theuncertainty in the models was judged to be covered.
The parameter values set for the assessment of the additional exposure doses in Section 3.4.1
are average or standard values, but there are variations in each parameter value and it is necessary
to consider uncertainty. Therefore, uncertainty was examined by evaluating the additional
exposure dose with conservative parameters used for the assessment of the additional exposure
dose per unit concentration of radioactive cesium in Section 3.4.1. However, GSG-3 notes that a
conservative assessment may show results that are not realistic, and caution is needed in theirinterpretation. The parameters under consideration for the uncertainty analysis were those thatmet both conditions (a) and (b), or only condition (c).
(a) Parameters of the exposure pathway, which account for more than 5% of the total additional
exposure dose in any of the four age groups（See Tables 7-10）(b) Averages and standard values.
(c) Parameters whose values change as a result of considering variations in parameters thatmatch both conditions (a) and (b).
The parameters that match both conditions (a) and (b) were the external exposure time (𝑡𝑠 ), theannual intake of food⁡(𝑀𝑓 ), and the market dilution factor of food (𝐺𝑓 ). The parameters consistent
with condition (c) were the soil ingestion time in former TSS (𝑡𝑠,𝑖𝑛𝑔 ), the dust inhalation time informer TSS (𝑡𝑠,𝑖𝑛ℎ ) and the market dilution factor of feed(𝑓𝑟 ). The list of parameters that wereconservatively set to account for uncertainty is given in Tables 3-6. The method for setting eachparameter considering the variations is as Appendix B.

15

Table 3. Parameters considered for uncertainty in each scenario (Adult)
Scenario

Standard

Conservative

parameter values

parameter values

183 h/year

640 h/year

53 h/year

186 h/year

54 kgFW/year

98 kgFW/year

0.5

1858 h/year

1,069 h/year

102 kgFW/year

191 kgFW/year

0.5

1852 h/year

989 h/year

540 h/year

781 h/year

37 kgFW/year

113 kgFW/year

0.5

11,244 h/year

2,284 h/year

23 kgFW/year

70 kgFW/year

market dilution factor of food（𝐺𝑓 ）0.51market dilution factor of feed （𝑓𝑟 ）

0.12

0.18

928 h/year

1,686 h/year

54 h/year

77 h/year

5,778 h/year

8,618 h/year

178 h/year

518 h/year

Parameters considered for uncertainty
external exposure time(𝑡𝑠 ), soil ingestion time in former
TSS (𝑡𝑠,𝑖𝑛𝑔 )Paddy

dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )annual intake of food（𝑀𝑓 ）market dilution factor of food（𝐺𝑓 ）external exposure time(𝑡𝑠 ), soil ingestion time in former

CroplandTSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )(vegetable)annual intake of food（𝑀𝑓 ）market dilution factor of food（𝐺𝑓 ）Croplandexternal exposure time(𝑡𝑠 ), soil ingestion time in former(flower)

TSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )external exposure time(𝑡𝑠 ), soil ingestion time in former

Orchard

TSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )annual intake of food（𝑀𝑓 ）market dilution factor of food（𝐺𝑓 ）external exposure time(𝑡𝑠 ), soil ingestion time in former
TSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )Pasture(milk cow)

annual intake of food（𝑀𝑓 ）Pastureexternal exposure time(𝑡𝑠 ), soil ingestion time in former(beef cattle)

TSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )Managedexternal exposure time(𝑡𝑠 ), soil ingestion time in former

ForestTSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )ResidencePark

external exposure time (indoor）（𝑡𝑠 ）external exposure time(𝑡𝑠 ), soil ingestion time in former
TSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )16

Table 4. Parameters considered for uncertainty in each scenario (1-6 years old)
Scenario

Standard

Conservative

parameter values

parameter values

183 h/year

640 h/year

53 h/year

186 h/year

35 kgFW/year

51 kgFW/year

0.5

1858 h/year

1,069 h/year

47 kgFW/year

75 kgFW/year

0.5

1852 h/year

989 h/year

540 h/year

781 h/year

34 kgFW/year

68 kgFW/year

0.5

11,244 h/year

2,284 h/year

52 kgFW/year

107 kgFW/year

market dilution factor of food（𝐺𝑓 ）0.51market dilution factor of feed （𝑓𝑟 ）

0.12

0.18

928 h/year

1,686 h/year

54 h/year

77 h/year

6,998 h/year

8,618 h/year

232 h/year

515 h/year

Parameters considered for uncertainty
external exposure time(𝑡𝑠 ), soil ingestion time in former
TSS (𝑡𝑠,𝑖𝑛𝑔 )Paddy

dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )annual intake of food（𝑀𝑓 ）market dilution factor of food（𝐺𝑓 ）external exposure time(𝑡𝑠 ), soil ingestion time in former

CroplandTSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )(vegetable)annual intake of food（𝑀𝑓 ）market dilution factor of food（𝐺𝑓 ）Croplandexternal exposure time(𝑡𝑠 ), soil ingestion time in former(flower)

TSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )external exposure time(𝑡𝑠 ), soil ingestion time in former

Orchard

TSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )annual intake of food（𝑀𝑓 ）market dilution factor of food（𝐺𝑓 ）external exposure time(𝑡𝑠 ), soil ingestion time in former
TSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )Pasture(milk cow)

annual intake of food（𝑀𝑓 ）Pastureexternal exposure time(𝑡𝑠 ), soil ingestion time in former(beef cattle)

TSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )Managedexternal exposure time(𝑡𝑠 ), soil ingestion time in former

ForestTSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )ResidencePark

external exposure time (indoor）（𝑡𝑠 ）external exposure time(𝑡𝑠 ), soil ingestion time in former
TSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )17

Table 5. Parameters considered for uncertainty in each scenario (7-14 years old)
Scenario

Standard

Conservative

parameter values

parameter values

183 h/year

640 h/year

53 h/year

186 h/year

61 kgFW/year

92 kgFW/year

0.5

1858 h/year

1,069 h/year

88 kgFW/year

133 kgFW/year

0.5

1852 h/year

989 h/year

540 h/year

781 h/year

27 kgFW/year

61 kgFW/year

0.5

11,244 h/year

2,284 h/year

92 kgFW/year

147 kgFW/year

market dilution factor of food（𝐺𝑓 ）0.51market dilution factor of feed （𝑓𝑟 ）

0.12

0.18

928 h/year

1,686 h/year

54 h/year

77 h/year

5,315 h/year

6,991 h/year

217 h/year

593 h/year

Parameters considered for uncertainty
external exposure time(𝑡𝑠 ), soil ingestion time in former
TSS (𝑡𝑠,𝑖𝑛𝑔 )Paddy

dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )annual intake of food（𝑀𝑓 ）market dilution factor of food（𝐺𝑓 ）external exposure time(𝑡𝑠 ), soil ingestion time in former

CroplandTSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )(vegetable)annual intake of food（𝑀𝑓 ）market dilution factor of food（𝐺𝑓 ）Croplandexternal exposure time(𝑡𝑠 ), soil ingestion time in former(flower)

TSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )external exposure time(𝑡𝑠 ), soil ingestion time in former

Orchard

TSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )annual intake of food（𝑀𝑓 ）market dilution factor of food（𝐺𝑓 ）external exposure time(𝑡𝑠 ), soil ingestion time in former
TSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )Pasture(milk cow)

annual intake of food（𝑀𝑓 ）Pastureexternal exposure time(𝑡𝑠 ), soil ingestion time in former(beef cattle)

TSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )Managedexternal exposure time(𝑡𝑠 ), soil ingestion time in former

ForestTSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )ResidencePark

external exposure time (indoor）（𝑡𝑠 ）external exposure time(𝑡𝑠 ), soil ingestion time in former
TSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )18

Table 6. Parameters considered for uncertainty in each scenario (15-19 years old)
Scenario

Standard

Conservative

parameter values

parameter values

183 h/year

640 h/year

53 h/year

186 h/year

78 kgFW/year

118 kgFW/year

0.5

1858 h/year

1,069 h/year

89 kgFW/year

145 kgFW/year

0.5

1852 h/year

989 h/year

540 h/year

781 h/year

24 kgFW/year

64 kgFW/year

0.5

11,244 h/year

2,284 h/year

36 kgFW/year

88 kgFW/year

market dilution factor of food（𝐺𝑓 ）0.51market dilution factor of feed （𝑓𝑟 ）

0.12

0.18

928 h/year

1,686 h/year

54 h/year

77 h/year

5,315 h/year

6,991 h/year

210 h/year

526 h/year

Parameters considered for uncertainty
external exposure time(𝑡𝑠 ), soil ingestion time in former
TSS (𝑡𝑠,𝑖𝑛𝑔 )Paddy

dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )annual intake of food（𝑀𝑓 ）market dilution factor of food（𝐺𝑓 ）external exposure time(𝑡𝑠 ), soil ingestion time in former

CroplandTSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )(vegetable)annual intake of food（𝑀𝑓 ）market dilution factor of food（𝐺𝑓 ）Croplandexternal exposure time(𝑡𝑠 ), soil ingestion time in former(flower)

TSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )external exposure time(𝑡𝑠 ), soil ingestion time in former

Orchard

TSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )annual intake of food（𝑀𝑓 ）market dilution factor of food（𝐺𝑓 ）external exposure time(𝑡𝑠 ), soil ingestion time in former
TSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )Pasture(milk cow)

annual intake of food（𝑀𝑓 ）Pastureexternal exposure time(𝑡𝑠 ), soil ingestion time in former(beef cattle)

TSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )Managedexternal exposure time(𝑡𝑠 ), soil ingestion time in former

ForestTSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )ResidencePark

external exposure time (indoor）（𝑡𝑠 ）external exposure time(𝑡𝑠 ), soil ingestion time in former
TSS (𝑡𝑠,𝑖𝑛𝑔 ), dust inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ )19

4. Assessment Result of additional exposure dose per unit concentration of radioactive cesium
4.1 Assessment results using average and standard parameter values
The calculation results of the additional exposure dose per unit concentration of the radioactive
cesium in soil are shown in Tables 7 to 10. The calculated additional exposure doses were highest
for the Residence scenario. The 1-6 years old age group received the highest exposure doses of
4.1×10-4 (mSv/year)/(Bq/kg).
For all scenarios other than the Paddy scenario, external exposure was the dominant contributor
to total additional exposure dose. In the Residence scenario, the external exposure dose was larger
than in the other scenarios due to the longer time spent at the TSS site (home time. In the Paddy
scenario, since the time spent (working hours) at the former TSS was relatively short, theimportance of the external exposure dose was relatively lower. The internal exposure doses dueto the soil ingestion and the dust inhalation were small in all scenarios. The additional exposure
dose in each exposure pathway was slightly different among the age groups, but the total values
did not differ significantly.
Moreover, when conducting the additional exposure dose assessment in response to requests
from municipalities and landowners of the TSSs, actual values should be applied not only for theconcentration of radioactive cesium in the topsoil, but also for various parameters with respect tothe potential usage time and food intake from the former TSS. As the result of this, more realistic
assessment becomes possible. In this study, although the ratio between the cesium-134 and thecesium-137 was decided based on the ratio in June 2022, it is possible to consider an actual
measurement day and change the existence ratio. However, since the existence ratio of cesium
134 is very small as of June 2022, it is considered that there is little effect even if it is changed inconsideration of the actual measurement date in the future.

20

Table 7. Additional exposure dose per unit concentration of radioactive cesiumin each scenario (Adults)(mSv/year) / (Bq/kg)
Internal exposure

Internal exposure Internal exposure(food ingestion)(soil ingestion)(dust inhalation)

1.9×10-5

1.5×10-5

2.1×10-9

6.1×10-10

3.4×10-5

56.9%

43.1%

0.0%

0.0%

100.0%

Cropland

9.1×10-5

2.8×10-5

9.7×10-9

9.9×10-9

1.2×10-4(vegetable)

76.6%

23.4%

0.0%

0.0%

100.0%

Cropland

9.1×10-5-

9.6×10-9

9.8×10-9

9.1×10-5(flower)

100.0%

-

0.0%

0.0%

100.0%

5.7×10-5

9.9×10-6

6.1×10-9

6.2×10-9

6.7×10-5

85.2%

14.7%

0.0%

0.0%

100.0%

Scenario

External exposure

Paddy

Orchard
Pasture1.3×10(milk cow)

97.8%

-4

3.0×10-6

1.4×10

2.2%

-8

0.0%

1.4×10-8

0.0%

1.4×10-4
100.0%

Pasture9.9×10-5-

1.0×10(beef cattle)

100.0%

-

0.0%

0.0%

100.0%

Managed1.1×10-5-

2.7×10-11

1.2×10-9

1.1×10-5

Forest100.0%

-

0.0%

0.0%

100.0%

2.6×10-4

6.4×10-6

1.6×10-9

1.6×10-9

2.7×10-4

97.6%

2.4%

0.0%

0.0%

100.0%

1.9×10-5-

2.0×10-9

2.1×10-9

1.9×10-5

100.0%

-

0.0%

0.0%

100.0%

Residence

Park

-8

Total

1.1×10（The lower row shows the percentage of the total additional exposure dose.）

21-8

9.9×10-5

Table 8. Additional exposure dose per unit concentration of radioactive cesiumin each scenario (1-6 years old)
(mSv/year) / (Bq/kg)
External

Internal exposure

Internal exposure

Internal exposure

exposure(food ingestion)(soil ingestion)(dust inhalation)

2.5×10-5

8.7×10-6

7.6×10-9

7.2×10-10

3.4×10-5

74.4%

25.6%

0.0%

0.0%

100.0%

Cropland1.2×10-4

1.2×10-5

3.6×10-8

1.2×10-8

1.3×10-4(vegetable)

90.9%

9.0%

0.0%

0.0%

100.0%

Cropland1.2×10-4-

3.5×10-8

1.1×10-8

1.2×10-4(flower)

100.0%

-

0.0%

0.0%

100.0%

7.5×10-5

8.5×10-6

2.2×10-8

7.3×10-9

8.3×10-5

89.8%

10.2%

0.0%

0.0%

100.0%

Scenario
Paddy

Orchard
Pasture1.7×10(milk cow)

96.4%

-4

6.4×10-6

5.2×10

3.6%

-8

0.0%

1.7×10-8

0.0%

1.8×10-4
100.0%

Pasture1.3×10-4-

3.9×10(beef cattle)

100.0%

-

0.0%

0.0%

100.0%

Managed1.4×10-5-

9.8×10-11

1.4×10-9

1.4×10-5

Forest100.0%

-

0.0%

0.0%

100.0%

4.1×10-4

2.3×10-6

5.9×10-9

1.9×10-9

4.1×10-4

99.4%

0.6%

0.0%

0.0%

100.0%

3.3×10-5-

1.0×10-8

3.2×10-9

3.3×10-5

100.0%

-

0.0%

0.0%

100.0%

Residence

Park

-8

Total

1.3×10-8（The lower row shows the percentage of the total additional exposure dose.）22

1.3×10-4

Table 9. Additional exposure dose per unit concentration of radioactive cesiumin each scenario (7-14 years old)
(mSv/year) / (Bq/kg)
External

Internal exposure

Internal exposure

Internal exposure

exposure(food ingestion)(soil ingestion)(dust inhalation)

2.1×10-5

1.3×10-5

4.8×10-9

4.9×10-10

3.4×10-5

62.9%

37.0%

0.0%

0.0%

100.0%

Cropland

1.0×10-4

1.8×10-5

2.2×10-8

7.9×10-9

1.2×10-4(vegetable)

84.6%

15.4%

0.0%

0.0%

100.0%

Cropland

1.0×10-4-

2.2×10-8

7.9×10-9

1.0×10-4(flower)

100.0%

-

0.0%

0.0%

100.0%

6.3×10-5

5.6×10-6

1.4×10-8

5.0×10-9

6.9×10-5

91.8%

8.1%

0.0%

0.0%

100.0%

Scenario

Paddy

Orchard
Pasture1.5×10(milk cow)

93.9%

-4

9.4×10-6

3.2×10

6.0%

-8

0.0%

1.2×10-8

0.0%

1.6×10-4
100.0%

Pasture1.1×10-4-

2.4×10(beef cattle)

100.0%

-

0.0%

0.0%

100.0%

Managed1.2×10-5-

6.1×10-11

9.9×10-10

1.2×10-5

Forest100.0%

-

0.0%

0.0%

100.0%

2.6×10-4

3.7×10-6

2.2×10-9

1.3×10-9

2.6×10-4

98.6%

1.4%

0.0%

0.0%

100.0%

2.6×10-5-

5.7×10-9

2.0×10-9

2.6×10-5

100.0%

-

0.0%

0.0%

100.0%

Residence

Park

-8

Total

8.6×10-9（The lower row shows the percentage of the total additional exposure dose.）23

1.1×10-4

Table 10. Additional exposure dose per unit concentration of radioactive cesiumin each scenario (15-19 years old)
(mSv/year) / (Bq/kg)
External

Internal exposure

Internal exposure Internal exposure

exposure(food ingestion)(soil ingestion)(dust inhalation)

2.0×10-5

2.1×10-5

2.1×10-9

5.8×10-10

4.1×10-5

48.5%

51.5%

0.0%

0.0%

100.0%

Cropland9.3×10-5

2.4×10-5

9.7×10-9

9.4×10-9

1.2×10-4(vegetable)

79.5%

20.5%

0.0%

0.0%

100.0%

Cropland9.3×10-5-

9.6×10-9

9.4×10-9

9.3×10-5(flower)

100.0%

-

0.0%

0.0%

100.0%

5.9×10-5

6.6×10-6

6.1×10-9

5.9×10-9

6.5×10-5

89.9%

10.0%

0.0%

0.0%

100.0%

Scenario

Paddy

Orchard
Pasture1.4×10(milk cow)

96.5%

-4

4.8×10-6

1.4×10

3.4%

-8

0.0%

1.4×10-8

0.0%

1.4×10-4
100.0%

Pasture1.0×10-4-

1.0×10(beef cattle)

100.0%

-

0.0%

0.0%

100.0%

Managed1.1×10-5-

2.7×10-11

1.2×10-9

1.1×10-5

Forest100.0%

-

0.0%

0.0%

100.0%

2.4×10-4

4.8×10-6

9.6×10-10

1.6×10-9

2.5×10-4

98.0%

2.0%

0.0%

0.0%

100.0%

2.3×10-5-

2.4×10-9

2.3×10-9

2.3×10-5

100.0%

-

0.0%

0.0%

100.0%

Residence

Park

-8

Total

1.0×10-8（The lower row shows the percentage of the total additional exposure dose.）24

1.0×10-4

4.2. Result of uncertainty analysis
In order to analyze the effect of the uncertainty in the parameter values, the additional exposure
doses per unit concentration of radioactive cesium were calculated using conservative values, andthe results are shown in Tables 11-14. The calculated additional exposure doses were highest for
the Residence scenario. The 1-6 years old age group received the highest exposure doses of
5.0×10-4 (mSv/year)/(Bq/kg). Comparing the calculated total dose results using the conservative
parameters with those calculated using the average or standard values, it was found that theincrease in the additional exposure dose was up to a factor of 3.6 times greater in the Paddy
scenario for adults. The ratio of the calculated dose using the average or standard parameter values
to the calculated dose using the conservative parameter values did not differ greatly depending on
the age group. Note that in the Managed Forest scenario, all parameters in the standard andconservative calculation methods have the same values.

25Table 11. Results of the uncertainty analysis of parameter values (Adult)（mSv/year）/（Bq/kg）
Ratio

Scenario

Calculation

External

Internal

methodexposure

exposure

Conservative
Total

total
dose/Standard
total doseStandard

1.9×10-5

1.5×10-5

3.4×10-5

Conservative

6.8×10-5

5.3×10-5

1.2×10-4

CroplandStandard

9.1×10-5

2.8×10-5

1.2×10-4(vegetable)

Conservative

1.1×10-4

1.0×10-4

2.2×10-4

CroplandStandard

9.1×10-5

1.9×10-8

9.1×10-5(flower)

Conservative

1.1×10-4

2.3×10-8

1.1×10-4

Standard

5.7×10-5

9.9×10-6

6.7×10-5

Conservative

8.3×10-5

6.2×10-5

1.4×10-4

PastureStandard

1.3×10-4

3.0×10-6

1.4×10-4(milk cow)

Conservative

2.4×10-4

2.7×10-5

2.7×10-4

PastureStandard

9.9×10-5

2.1×10-8

9.9×10-5(beef cattle)

Conservative

1.8×10-4

3.8×10-8

1.8×10-4

ManagedStandard

1.1×10-5

1.3×10-9

1.1×10-5

ForestConservative

1.1×10-5

1.3×10-9

1.1×10-5

Standard

2.6×10-4

6.4×10-6

2.7×10-4

Conservative

3.8×10-4

6.4×10-6

3.9×10-4

Standard

1.9×10-5

4.1×10-9

1.9×10-5

Conservative

5.5×10-5

1.2×10-8

5.5×10-5

Paddy

OrchardResidence

Park

3.6

1.8

1.2

2.1

2.0

1.8

1.0

1.5

2.9

（In terms of calculation methods, calculations using average or standard parameter values were
designated as "standard", while calculations using parameter values that take variability into
account were designated as "conservative".）

26

Table 12. Results of the uncertainty analysis of parameter values (1-6 years old)
（mSv/year）/（Bq/kg）
Ratio

Scenario

Calculation

External

Internal

methodexposure

exposure

Conservative
Total

total
dose/Standard
total doseStandard

2.5×10-5

8.7×10-6

3.4×10-5

Conservative

8.8×10-5

2.6×10-5

1.1×10-4

CroplandStandard

1.2×10-4

1.2×10-5

1.3×10-4(vegetable)

Conservative

1.5×10-4

3.7×10-5

1.9×10-4

CroplandStandard

1.2×10-4

4.7×10-8

1.2×10-4(flower)

Conservative

1.4×10-4

5.4×10-8

1.4×10-4

Standard

7.5×10-5

8.5×10-6

8.3×10-5

Conservative

1.1×10-4

3.4×10-5

1.4×10-4

PastureStandard

1.7×10-4

6.5×10-6

1.8×10-4(milk cow)

Conservative

3.2×10-4

3.8×10-5

3.5×10-4

PastureStandard

1.3×10-4

5.1×10-8

1.3×10-4(beef cattle)

Conservative

2.3×10-4

9.3×10-8

2.3×10-4

ManagedStandard

1.4×10-5

1.5×10-9

1.4×10-5

ForestConservative

1.4×10-5

1.5×10-9

1.4×10-5

Standard

4.1×10-4

2.4×10-6

4.1×10-4

Conservative

5.0×10-4

2.4×10-6

5.0×10-4

Standard

3.3×10-5

1.3×10-8

3.3×10-5

Conservative

7.2×10-5

2.9×10-8

7.2×10-5

Paddy

OrchardResidence

Park

3.4

1.4

1.2

1.7

2.0

1.8

1.0

1.2

2.2

（In terms of calculation methods, calculations using average or standard parameter values were
designated as "standard", while calculations using parameter values that take variability into
account were designated as "conservative".）27

Table 13. Results of the uncertainty analysis of parameter values (7-14 years old)
（mSv/year）/（Bq/kg）
Ratio

Scenario

Calculation

External

Internal

methodexposure

exposure

Conservative
Total

total
dose/Standard
total doseStandard

2.1×10-5

1.3×10-5

3.4×10-5

Conservative

7.5×10-5

3.8×10-5

1.1×10-4

CroplandStandard

1.0×10-4

1.8×10-5

1.2×10-4(vegetable)

Conservative

1.3×10-4

5.6×10-5

1.8×10-4

CroplandStandard

1.0×10-4

3.0×10-8

1.0×10-4(flower)

Conservative

1.2×10-4

3.5×10-8

1.2×10-4

Standard

6.3×10-5

5.6×10-6

6.9×10-5

Conservative

9.2×10-5

2.5×10-5

1.2×10-4

PastureStandard

1.5×10-4

9.4×10-6

1.6×10-4(milk cow)

Conservative

2.7×10-4

4.4×10-5

3.1×10-4

PastureStandard

1.1×10-4

3.3×10-8

1.1×10-4(beef cattle)

Conservative

2.0×10-4

6.0×10-8

2.0×10-4

ManagedStandard

1.2×10-5

1.0×10-9

1.2×10-5

ForestConservative

1.2×10-5

1.0×10-9

1.2×10-5

Standard

2.6×10-4

3.7×10-6

2.6×10-4

Conservative

3.4×10-4

3.7×10-6

3.4×10-4

Standard

2.6×10-5

7.8×10-9

2.6×10-5

Conservative

7.1×10-5

2.1×10-8

7.1×10-5

Paddy

OrchardResidence

Park

3.3

1.5

1.2

1.7

2.0

1.8

1.0

1.3

2.7

（In terms of calculation methods, calculations using average or standard parameter values were
designated as "standard", while calculations using parameter values that take variability into
account were designated as "conservative".）28

Table 14. Results of the uncertainty analysis of parameter values (15-19 years old)
（mSv/year）/（Bq/kg）
Ratio

Scenario

Calculation

External

Internal

methodexposure

exposure

Conservative
Total

total
dose/Standard
total doseStandard

2.0×10-5

2.1×10-5

4.1×10-5

Conservative

7.0×10-5

6.4×10-5

1.3×10-4

CroplandStandard

9.3×10-5

2.4×10-5

1.2×10-4(vegetable)

Conservative

1.2×10-4

7.9×10-5

2.0×10-4

CroplandStandard

9.3×10-5

1.9×10-8

9.3×10-5(flower)

Conservative

1.1×10-4

2.2×10-8

1.1×10-4

Standard

5.9×10-5

6.6×10-6

6.5×10-5

Conservative

8.5×10-5

3.5×10-5

1.2×10-4

PastureStandard

1.4×10-4

4.9×10-6

1.4×10-4(milk cow)

Conservative

2.5×10-4

3.4×10-5

2.8×10-4

PastureStandard

1.0×10-4

2.1×10-8

1.0×10-4(beef cattle)

Conservative

1.8×10-4

3.8×10-8

1.8×10-4

ManagedStandard

1.1×10-5

1.2×10-9

1.1×10-5

ForestConservative

1.1×10-5

1.2×10-9

1.1×10-5

Standard

2.4×10-4

4.8×10-6

2.5×10-4

Conservative

3.1×10-4

4.8×10-6

3.2×10-4

Standard

2.3×10-5

4.7×10-9

2.3×10-5

Conservative

5.8×10-5

1.2×10-8

5.8×10-5

Paddy

OrchardResidence

Park

3.3

1.7

1.2

1.8

2.0

1.8

1.0

1.3

2.5

（In terms of calculation methods, calculations using average or standard parameter values were
designated as "standard", while calculations using parameter values that take variability into
account were designated as "conservative".）29

5. Methods for Case Studies
The additional exposure dose per unit concentration of radioactive cesium (mSv/year)/(Bq/kg)
calculated in 3.4 was multiplied by "the cesium concentration in the topsoil of the former TSS"or "the cesium concentration estimated from the air dose rate of the former TSS," and the
additional exposure dose (mSv/year) was assessed as the case studies. Furthermore, we compared
the calculated additional exposure dose with the long-term goal (1 mSv/year).
5.1. Assessment method of additional exposure dose by using the actual radioactive cesium
concentration measured at the former TSS.
Case study calculations were done by multiplying the standard additional exposure dose per unit
concentration of radioactive cesium shown in 3.4.1 and the conservative additional exposure dose
per unit concentration of radioactive cesium shown in 3.4.2 by the measured values of cesium137 concentration in the topsoil of the actual former TSS. In the standard case assessment, theaverage value of the measured values was used. In the conservative case assessment, themaximum value of the measured value was used. The measured values of radioactive cesium
concentration in the topsoil of the former TSSs used for the calculation are shown in Table 15. Inorder to assess the former TSSs in various situations, the TSSs of the three areas, A, B and C,
were selected, which differ in their assumed land-use and areas where they are located. For theassumed land-use, interviews were conducted with the municipalities where the former TSSs arelocated. Although the date of measurement of radioactive cesium concentration at each TSS isdifferent, all values were assessed as of June 2022.
Soil sampling was done within 5 cm depth from the surface. Soil sampling points for the TSS
of A were selected by dividing the entire TSS into three subdivisions so that each subdivision was
no larger than 1,000 m2. Five points were selected at the center and four corners of eachsubdivision. The soil sampling points for the TSSs of B and C were the same some areas where
the soil was stored. If the area of the plot where the soil was stored did not exceed 20 m x 20 m,
the center and four corners of the TSS were used as soil sampling points. If the area exceeded 20
m x 20 m, the plot was divided into meshes of about 10 m in addition to the center and four
corners, and the center and four corners of each mesh were used as soil sampling points. The
concentration of cesium-137 in the soil was measured with a germanium semiconductor detector.
The selection of soil sampling sites described above differs from the method in the Ministry of
the Environment's guidelines 2.
The concentration of cesium-137 in the topsoil of the TSS of A was higher than that of the TSSof B or C (Table 15). The very low Cs-137 concentrations in TSS B and C are probably due tothese sites being levelled before the TSS was created.

30

Table 15. Basic information and measurement results of the former temporary storage sitewhere actual measurement of cesium-137 concentration in soil was conducted

Assumed land-use

Number ofconcentration of 137Cs

Area size

sites where[Bq/kg]2

soil samples[m ]were taken
TSS A

Agricultural land
(excluding pasture)

Locationmaximum

averageArea

2.3×103

11

636

160

Hamadori

TSS B

Managed Forest

7.5×103

400

38

6

Nakadori

TSS C

Buildings, parks, etc.

1.0×103

38

13

4

Aizu

（The mean value was calculated by excluding values below the detection limit.）

5.2 Assessment method of additional exposure dose using measured value of air dose rate
in TSS
In order to confirm the representativeness of the case studies described in section 5.1,
questionnaire surveys were carried out for 29 municipalities (including the sites of 794 TSSs)
from among the municipalities in ICSA in Fukushima Prefecture. As a result, values of the air
dose rate at a large number of TSS were obtained.
The survey period was from February 16th to March 31th, 2022. The survey items are themeasurement date and the air dose rate at the position of 1 m height from the ground of the TSS
measured by the municipality after the restoration work was completed (the measurement resultof (5) in Figure 6). However, if the municipality did not measure air dose rates after the restoration
work was completed, air dose rates after the removal of the removed soil (the measurement resultof (3) in Figure 6) were answered instead. Many municipalities use the air dose rates instead of
the radioactive cesium concentrations in the topsoil to determine the presence or absence ofcontamination. When the measurement lasted several days, the data from the last day was used.
In cases where the measurement date at a certain TSS was unknown, the most recent data available
from other TSS sites in the same municipality were used.
The probability distribution of the additional exposure dose for the survey sites was estimatedby multiplying the cesium 137 concentration in the surface soil converted from the air dose rateof each TSS site by the additional exposure dose per unit concentration of the radioactive cesium
calculated in Section 3.4. Equations (C1) and (C2) in Appendix C were used to convert air dose
rates to cesium 137 concentrations in topsoil. The estimated probability distribution for the survey
sites was compared with the results for the case studies in Section 5.1.

31

6. Assessed Results of Case Studies
6.1. Assessed Results of additional exposure dose calculated from the measured radioactive
cesium concentration in three actual TSSs

The calculation results for the additional exposure dose using the cesium-137 concentration
measured in the topsoil of the actual TSSs are shown in Tables 16-19.
•

In the calculations using the average and standard parameter values, the greatest
additional exposure dose, 2.1×10-2 mSv/year, was calculated for TSS A for the Cropland(vegetable) scenario and the 1-6 years old age group.

•

In the calculations using the conservative parameter values, the greatest additional
exposure dose, 1.4×10-1 mSv/year, was calculated for TSS A for the Cropland(vegetable) scenario and adults.

As these values are below 1 mSv/year, the sites of TSS A, B and C can be used safely. Other
former TSS sites having the same or lower concentrations of radioactive Cs and the same land
uses as TSS sites A, B and C should also be safe.
Table 16. Additional exposure dose by using cesium-137 concentration in the topsoil of theactual former TSS (Adult)（mSv/year）
TSS

Calculation

External

Internal

methodexposure

exposureStandard

3.1×10-3

2.4×10-3

5.5×10-3

Conservative

4.3×10-2

3.4×10-2

7.7×10-2

CroplandStandard

1.5×10-2

4.5×10-3

1.9×10-2(vegetable)

Conservative

7.2×10-2

6.6×10-2

1.4×10-1

CroplandStandard

1.5×10-2

3.1×10-6

1.5×10-2(flower)

Conservative

6.7×10-2

1.4×10-5

6.7×10-2

Standard

9.2×10-3

1.6×10-3

1.1×10-2

Conservative

5.3×10-2

3.9×10-2

9.2×10-2

ManagedStandard

7.3×10-5

8.4×10-9

7.3×10-5

ForestConservative

4.2×10-4

4.8×10-8

4.2×10-4

Standard

1.6×10-3

3.8×10-5

1.6×10-3

Conservative

4.9×10-3

8.3×10-5

5.0×10-3

Standard

1.1×10-4

2.5×10-8

1.1×10-4

Conservative

7.1×10-4

1.5×10-7

7.1×10-4

Scenario

Paddy

TSS A

OrchardTSS B

Residence
TSS C
Park

Total

（In terms of calculation methods, calculations using average or standard parameter values were
designated as "standard", while calculations using parameter values that take variability into
account were designated as "conservative".）32

Table 17. Additional exposure dose by using cesium-137 concentration in the topsoil of theactual former TSS (1-6 years old)
（mSv/year）
TSS

Calculation

External

Internal

methodexposure

exposureStandard

4.0×10-3

1.4×10-3

5.4×10-3

Conservative

5.6×10-2

1.6×10-2

7.3×10-2

CroplandStandard

1.9×10-2

1.9×10-3

2.1×10-2(vegetable)

Conservative

9.4×10-2

2.4×10-2

1.2×10-1

CroplandStandard

1.9×10-2

7.5×10-6

1.9×10-2(flower)

Conservative

8.7×10-2

3.5×10-5

8.7×10-2

Standard

1.2×10-2

1.4×10-3

1.3×10-2

Conservative

6.9×10-2

2.1×10-2

9.0×10-2

Standard

9.5×10-5

1.0×10-8

9.5×10-5

Conservative

5.5×10-4

5.9×10-8

5.5×10-4

Standard

2.4×10-3

1.4×10-5

2.5×10-3

Conservative

6.4×10-3

3.0×10-5

6.4×10-3

Standard

2.0×10-4

7.9×10-8

2.0×10-4

Conservative

9.3×10-4

3.7×10-7

9.3×10-4

Scenario

Paddy

TSS A

OrchardTSS BManaged Forest

Residence
TSS C
Park

Total

（In terms of calculation methods, calculations using average or standard parameter values were
designated as "standard", while calculations using parameter values that take variability into
account were designated as "conservative".）33

Table 18. Additional exposure dose by using cesium-137 concentration in the topsoil of theactual former TSS (7-14 years old)
（mSv/year）
TSS

Calculation

External

Internal

methodexposure

exposureStandard

3.4×10-3

2.0×10-3

5.5×10-3

Conservative

4.8×10-2

2.4×10-2

7.2×10-2

CroplandStandard

1.6×10-2

2.9×10-3

1.9×10-2(vegetable)

Conservative

8.0×10-2

3.5×10-2

1.2×10-1

CroplandStandard

1.6×10-2

4.8×10-6

1.6×10-2(flower)

Conservative

7.4×10-2

2.2×10-5

7.4×10-2

Standard

1.0×10-2

9.0×10-4

1.1×10-2

Conservative

5.8×10-2

1.6×10-2

7.4×10-2

Standard

8.1×10-5

7.0×10-9

8.1×10-5

Conservative

4.6×10-4

4.0×10-8

4.6×10-4

Standard

1.6×10-3

2.2×10-5

1.6×10-3

Conservative

4.4×10-3

4.7×10-5

4.4×10-3

Standard

1.6×10-4

4.7×10-8

1.6×10-4

Conservative

9.1×10-4

2.7×10-7

9.1×10-4

Scenario

Paddy

TSS A

OrchardTSS BManaged Forest

Residence
TSS C
Park

Total

（In terms of calculation methods, calculations using average or standard parameter values were
designated as "standard", while calculations using parameter values that take variability into
account were designated as "conservative".）34

Table 19. Additional exposure dose by using cesium-137 concentration in the topsoil of theactual former TSS (15-19 years old)
（mSv/year）
TSS

Calculation

External

Internal

methodexposure

exposureStandard

3.2×10-3

3.4×10-3

6.6×10-3

Conservative

4.4×10-2

4.1×10-2

8.5×10-2

CroplandStandard

1.5×10-2

3.9×10-3

1.9×10-2(vegetable)

Conservative

7.4×10-2

5.0×10-2

1.2×10-1

CroplandStandard

1.5×10-2

3.0×10-6

1.5×10-2(flower)

Conservative

6.8×10-2

1.4×10-5

6.8×10-2

Standard

9.4×10-3

1.1×10-3

1.0×10-2

Conservative

5.4×10-2

2.2×10-2

7.6×10-2

Standard

7.5×10-5

8.0×10-9

7.5×10-5

Conservative

4.3×10-4

4.6×10-8

4.3×10-4

Standard

1.4×10-3

2.9×10-5

1.5×10-3

Conservative

4.0×10-3

6.2×10-5

4.1×10-3

Standard

1.4×10-4

2.8×10-8

1.4×10-4

Conservative

7.4×10-4

1.5×10-7

7.4×10-4

Scenario

Paddy

TSS A

OrchardTSS BManaged Forest

Residence
TSS C
Park

Total

（In terms of calculation methods, calculations using average or standard parameter values were
designated as "standard", while calculations using parameter values that take variability into
account were designated as "conservative".）35

6.2．Assessment results of additional exposure dose using measured value of air dose rate
in site of TSS
As a result of the questionnaire to municipalities, 23 municipalities responded, and the values of
the air dose rate (the measurement result of (5) in Figure 6) at the sites of 571 former TSSs wereobtained. Of these 571, measurements were carried out just after the removal of soil at the sitesof 138 former TSSs (the measurement result of (3) in Figure 6). The average and maximum values(minus the air dose rate based on the natural nuclides) of the measured air dose rates were 0.07
µSv/h and 0.31 µSv/h, respectively. The probability distribution of the air dose rates at the TSS isshown in Figure 9.
The concentration of cesium-137 in the topsoil was estimated from the air dose rates in the 571
former TSSs using equations (C1) and (C2) in Appendix C, and the estimated average value was
353 Bq/kg and the estimated maximum value was 1,434 Bq/kg. The additional exposure dose ateach site was calculated from the estimated cesium-137 concentration, as follows:•

In the calculations using the average and standard parameter values (cesium-137
concentration is the average value), the expectation value of additional exposure dose,
9.4×10-2 mSv/year, was calculated for the Residence scenario and the adult.

•

In the calculations using the average and standard parameter values (cesium-137
concentration is the maximum value), the greatest additional exposure dose, 5.9×10-1
mSv/year, was calculated for the Residence scenario and the 1-6 years old age group.

•

In the calculations using the conservative parameter values (cesium-137 concentrationis the maximum value), the greatest additional exposure dose, 7.1×10-1 mSv/year, wasfor the Residence scenario and the 1-6 years old age group.

The average and maximum values of the additional exposure dose for each age group in eachsite after TSS are shown in Tables 20-23.
The probability distribution of the additional exposure dose for adults is shown in Figures 1018. This shows the probability distribution using standard parameters and the probability
distribution conservative parameter values. The results for TSS A, B and C have also been added
to the figures. In the distribution of the additional exposure dose estimated from the survey air
dose rates, it was found that the TSS A is located on the higher dose range side from near thecenter, and conversely, the TSS B and C are located on the lower dose range side.
The average of the measured air dose rate (minus the air dose rate based on the natural nuclides)
at TSS A was 0.06 µSv/h, and the cesium-137 concentration in the topsoil estimated using thisvalue was 313 Bq/kg. The average of the measured cesium-137 concentration in the topsoil at
TSS A was 160 Bq/kg, and the estimated value was about twice the measured value. This suggeststhat the calculations using equations (C1) and (C2) are conservative.

36

40%
40

Number of TSS [%]30%
30* Minus the air dose rate based on the natural nuclides

20%
20

10%
10

0%
0
0

1

0.05

2

0.10

3

0.15

4

0.20

5

0.25 60.30 70.35

Air dose rate [μSv/h]

Figure 9. The probability distribution of the measured air dose rates at the TSS

37

Table 20. Additional exposure dose (adults) using cesium-137 concentration estimated from air
dose rate(mSv/year)
Scenario

Estimated cesium-137 concentration

Calculation
methodAverage (353 Bq/kg)

Maximum (1,434 Bq/kg)

Standard

1.2×10-2

4.9×10-2

Conservative

4.3×10-2

1.7×10-1

CroplandStandard

4.2×10-2

1.7×10-1(vegetable)

Conservative

7.7×10-2

3.1×10-1

CroplandStandard

3.2×10-2

1.3×10-1(flower)

Conservative

3.7×10-2

1.5×10-1

Standard

2.4×10-2

9.7×10-2

Conservative

5.1×10-2

2.1×10-1

PastureStandard

4.8×10-2

1.9×10-1(milk cow)

Conservative

9.5×10-2

3.9×10-1

PastureStandard

3.5×10-2

1.4×10-1(beef cattle)

Conservative

6.3×10-2

2.6×10-1

ManagedStandard

3.9×10-2

1.6×10-2

ForestConservative

3.9×10-2

1.6×10-2

Standard

9.4×10-2

3.8×10-1

Conservative

1.4×10-2

5.6×10-1

Standard

6.8×10-2

2.7×10-2

Conservative

2.0×10-2

7.9×10-2

Paddy

OrchardResidencePark（In terms of calculation methods, calculations using average or standard parameter values were
designated as "standard", while calculations using parameter values that take variability into
account were designated as "conservative".）38

Table 21. Additional exposure dose (1-6 years old) using cesium-137 concentration estimatedfrom air dose rate
(mSv/year)
Scenario

Estimated cesium-137 concentration

Calculation
methodAverage (353 Bq/kg)

Maximum (1,434 Bq/kg)

Standard

1.2×10-2

4.9×10-2

Conservative

4.0×10-2

1.6×10-1

CroplandStandard

4.6×10-2

1.9×10-1(vegetable)

Conservative

6.5×10-2

2.7×10-1

CroplandStandard

4.2×10-2

1.7×10-1(flower)

Conservative

4.8×10-2

2.0×10-1

Standard

2.9×10-2

1.2×10-1

Conservative

5.0×10-2

2.0×10-1

PastureStandard

6.3×10-2

2.6×10-1(milk cow)

Conservative

1.3×10-1

5.1×10-1

PastureStandard

4.5×10-2

1.8×10-1(beef cattle)

Conservative

8.2×10-2

3.3×10-1

ManagedStandard

5.0×10-3

2.0×10-2

ForestConservative

5.0×10-3

2.0×10-2

Standard

1.4×10-1

5.9×10-1

Conservative

1.8×10-1

7.1×10-1

Standard

1.2×10-2

4.8×10-2

Conservative

2.5×10-2

1.0×10-1

Paddy

OrchardResidencePark（In terms of calculation methods, calculations using average or standard parameter values were
designated as "standard", while calculations using parameter values that take variability into
account were designated as "conservative".）

39

Table 22. Additional exposure dose (7-14 years old) using cesium-137 concentration estimatedfrom air dose rate
(mSv/year)
Scenario

Estimated cesium-137 concentration

Calculation
methodAverage (353 Bq/kg)

Maximum (1,434 Bq/kg)

Standard

1.2×10-2

4.9×10-2

Conservative

4.0×10-2

1.6×10-1

CroplandStandard

4.2×10-2

1.7×10-1(vegetable)

Conservative

6.4×10-2

2.6×10-1

CroplandStandard

3.5×10-2

1.4×10-1(flower)

Conservative

4.1×10-2

1.7×10-1

Standard

2.4×10-2

9.9×10-2

Conservative

4.1×10-2

1.7×10-1

PastureStandard

5.5×10-2

2.2×10-1(milk cow)

Conservative

1.1×10-1

4.5×10-1

PastureStandard

3.9×10-2

1.6×10-1(beef cattle)

Conservative

7.0×10-2

2.8×10-1

ManagedStandard

4.3×10-3

1.7×10-2

ForestConservative

4.3×10-3

1.7×10-2

Standard

9.3×10-2

3.8×10-1

Conservative

1.2×10-1

4.9×10-1

Standard

9.1×10-3

3.7×10-2

Conservative

2.5×10-2

1.0×10-1

Paddy

OrchardResidencePark（In terms of calculation methods, calculations using average or standard parameter values were
designated as "standard", while calculations using parameter values that take variability into
account were designated as "conservative".）40

Table 23. Additional exposure dose (15-19 years old) using cesium-137 concentration estimatedfrom air dose rate
(mSv/year)
Scenario

Estimated cesium-137 concentration

Calculation
methodAverage (353 Bq/kg)

Maximum (1,434 Bq/kg)

Standard

1.5×10-2

5.9×10-2

Conservative

4.7×10-2

1.9×10-1

CroplandStandard

4.1×10-2

1.7×10-1(vegetable)

Conservative

6.9×10-2

2.8×10-1

CroplandStandard

3.3×10-2

1.3×10-1(flower)

Conservative

3.8×10-2

1.5×10-1

Standard

2.3×10-2

9.4×10-2

Conservative

4.2×10-2

1.7×10-1

PastureStandard

5.0×10-2

2.0×10-1(milk cow)

Conservative

1.0×10-1

4.1×10-1

PastureStandard

3.6×10-2

1.4×10-1(beef cattle)

Conservative

6.5×10-2

2.6×10-1

ManagedStandard

4.0×10-3

1.6×10-2

ForestConservative

4.0×10-3

1.6×10-2

Standard

8.7×10-2

3.5×10-1

Conservative

1.1×10-1

4.6×10-1

Standard

8.1×10-3

3.3×10-2

Conservative

2.0×10-2

8.3×10-2

Paddy

OrchardResidencePark（In terms of calculation methods, calculations using average or standard parameter values were
designated as "standard", while calculations using parameter values that take variability into
account were designated as "conservative".）

41

0
0%

20
20%

40
40%

60
60%

Conservative
畑（野菜）（保守的）5.0
1.0E-03～
1.0
5.0E-04～
5.0×10-1
1.0E-04～
1.0×10-1
5.0E-05～
5.0×10-2
1.0E-05～
1.0×10-2
5.0E-06～
5.0×10-3
1.0E-06～
1.0×10-3
5.0E-07～
5.0×10-4
5.0E-07未満
0

畑（野菜）（標準的）Standard

TSS A, Conservative
TSS A, Standard

Additional exposure dose [mSv/y]

水田（保守的）Conservative
Standard
水田（標準的）TSS A, Conservative
TSS A, Standard

Additional exposure dose [mSv/y]

5.0
1.0E-03～
1.0
5.0E-04～
5.0×10-1
1.0E-04～
1.0×10-1
5.0E-05～
5.0×10-2
1.0E-05～
1.0×10-2
5.0E-06～
5.0×10-3
1.0E-06～
1.0×10-3
5.0E-07～
5.0×10-4
5.0E-07未満
0

80
80%

0%
0

Number of TSS [%]Figure 10. Additional exposure dose using estimated 137Cs(Cropland (vegetable) scenario (Adult))

20%
20

40%
40

60%
60

Conservative
樹園地（保守的）Standard
樹園地（標準的）

5.0
1.0E-03～
1.0
5.0E-04～
5.0×10-1
1.0E-04～
1.0×10-1
5.0E-05～
5.0×10-2
1.0E-05～
1.0×10-2
5.0E-06～
5.0×10-3
1.0E-06～
1.0×10-3
5.0E-07～
5.0×10-4
5.0E-07未満
0

TSS A, Conservative
TSS A, Standard

Additional exposure dose [mSv/y]

TSS A, Conservative
TSS A, Standard

Additional exposure dose [mSv/y]Conservative
畑（花卉）（保守的）Standard
畑（花卉）（標準的）

0%
0

80%
80

Figure 11. Additional exposure dose using estimated 137Cs(Paddy scenario (Adult))

5.0
1.0E-03～
1.0
5.0E-04～
5.0×10-1
1.0E-04～
1.0×10-1
5.0E-05～
5.0×10-2
1.0E-05～
1.0×10-2
5.0E-06～
5.0×10-3
1.0E-06～
1.0×10-3
5.0E-07～
5.0×10-4
5.0E-07未満
0

20%
40%
60%
20
40
60
Number of TSS [%]

0
0%

80%
80

Number of TSS [%]

20
20%

40
40%

60
60%

80
80%

Number of TSS [%]Figure 12. Additional exposure dose using estimated 137Cs Figure 13. Additional exposure dose using estimated 137Cs

5.0
1.0E-03～
1.0
5.0E-04～
5.0×10-1
1.0E-04～
1.0×10-1
5.0E-05～
5.0×10-2
1.0E-05～
1.0×10-2
5.0E-06～
5.0×10-3
1.0E-06～
1.0×10-3
5.0E-07～
5.0×10-4
5.0E-07未満
0(Orchard scenario (Adult))

Conservative
牧草地（乳牛）（保守的）Standard
牧草地（乳牛）（標準的）Additional exposure dose [mSv/y]

Additional exposure dose [mSv/y](Cropland (flower) scenario (Adult))

0
0%

20
40
60
20%
40%
60%
Number of TSS [%]80
80%

Figure 14. Additional exposure dose using estimated 137Cs

5.0
1.0E-03～
1.0
5.0E-04～
5.0×10-1
1.0E-04～
1.0×10-1
5.0E-05～
5.0×10-2
1.0E-05～
1.0×10-2
5.0E-06～
5.0×10-3
1.0E-06～
1.0×10-3
5.0E-07～
5.0×10-4
5.0E-07未満
0Conservative
牧草地（肉牛）（保守的）Standard
牧草地（肉牛）（標準的）

0
0%

20
40
60
20%
40%
60%
Number of TSS [%]80
80%

Figure 15. Additional exposure dose using estimated 137Cs(Pasture (milk cow) scenario (Adult))(Pasture (beef cattle) scenario (Adult))

42

0
0%

20
40
60
20%
40%
60%
Number of TSS [%]80
80%

Figure 16. Additional exposure dose using estimated 137Cs

TSS C, Conservative

Additional exposure dose [mSv/y]

TSS C, Standard

20
40
60
20%
40%
60%
Number of TSS [%]TSS C, Conservative

Conservative
住宅（保守的）Standard
住宅（標準的）

0
0%

20
40
60
20%
40%
60%
Number of TSS [%]80
80%(Residence scenario (Adult))

Conservative
公園（保守的）Standard
公園（標準的）00%

5.0
1.0E-03～
1.0
5.0E-04～
5.0×10-1
1.0E-04～
1.0×10-1
5.0E-05～
5.0×10-2
1.0E-05～
1.0×10-2
5.0E-06～
5.0×10-3
1.0E-06～
1.0×10-3
5.0E-07～
5.0×10-4
5.0E-07未満
0

Figure 17. Additional exposure dose using estimated 137Cs(Managed Forest scenario (Adult))

5.0
1.0E-03～
1.0
5.0E-04～
5.0×10-1
1.0E-04～
1.0×10-1
5.0E-05～
5.0×10-2
1.0E-05～
1.0×10-2
5.0E-06～
5.0×10-3
1.0E-06～
1.0×10-3
5.0E-07～
5.0×10-4
5.0E-07未満
0TSS C, Standard

Conservative
森林（保守的）Standard
森林（標準的）

Additional exposure dose [mSv/y]

TSS B, Standard and Conservative

Additional exposure dose [mSv/y]

5.0
1.0E-03～
1.0
5.0E-04～
5.0×10-1
1.0E-04～
1.0×10-1
5.0E-05～
5.0×10-2
1.0E-05～
1.0×10-2
5.0E-06～
5.0×10-3
1.0E-06～
1.0×10-3
5.0E-07～
5.0×10-4
5.0E-07未満
0

80
80%

Figure 18. Additional exposure dose using estimated 137Cs(Park scenario (Adult))

43

7. Conclusions
The additional exposure dose per unit concentration of radioactive cesium in the soil (1 Bq/kg)
was calculated for possible land uses at the former TSS. The results of the calculations using thestandard data showed that the largest potential doses would be calculated for the Residence
scenario and the 1 to 6 years old age group.
As described above, by using a unit concentration of radioactive cesium in soil, which can bescaled using the actual soil contamination level, the method can be used to estimate the additional
exposure dose according to the various land uses that could occur in the future.
Case study calculations were performed to calculate the exposure dose for three TSS sites, A,
B and C, based on measured data on cesium concentrations in soil. Further calculations weremade using measured data on the air dose at TSS first to estimate cesium concentrations in soil
and second to calculate the exposure doses at those sites. For all scenarios considered, theexpected doses are well below 1 mSv/year. In addition, the dose values obtained using
conservative parameter values were also below 1 mSv/year for all studied TSSs. This means that
there is very low probability that any individual from the potentially exposed population would
receive an annual dose above the long-term goal. It should be noted that the assessment results
are very cautious because multiple parameter values are set conservatively.
The above results can be provided to the people and should effectively assist those managing theformer TSSs and those who have concerns over the use of the former TSS.
In addition, since the assessment method in this study is general and can be widely used, it canbe expected that the present assessment method would be highly applicable to dose assessment
for sites other than the sites of former TSSs.
Acknowledgement
We would like to express our gratitude to Mr. T. Inoue, Central Research Institute of Electric Power
Industry, Mr. N. Nomura, Fukui university of Technology, Mr. G. Bruno, IAEA, Mr. D.G. Bennett,
IAEA, and to Mr. R. Avila, Mr. D. Bugai, Mr. R. Kemp and Ms. S. Mobbs, independent experts(IAEA invited), for their advice in conducting this study. The study was conducted with the supportof the IAEA. The views expressed in this report are those of the Fukushima Prefectural Centre forEnvironmental Creation and do not necessarily reflect the views of the IAEA or the independent
experts.
Reference
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Daiichi Nuclear Power Station
http://josen.env.go.jp/archive/decontamination_project_report/ (Accessed 2022-9-1)

442) Ministry of the Environment, Decontamination-related Guidelines, Second Edition, May 2013 (revised
March 2008)
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Survey Areas
https://www.pref.fukushima.lg.jp/sec/16045d/tiikisitei20200316.html#:~:text=%E6%94%BE%E5%B0%84%E6%80%A7%E7%89%A9%E8%B3%AA%E6%
B1%9A%E6%9F%93%E5%AF%BE%E5%87%A6%E7%89%B9%E5%88%A5,%E6%9F%93%E3%82%92%E5%AE%9F%E6%96%BD%E3%81%97%E3%81%BE%E3%81%97%E3%81%9F%E3%80%82(Accessed 2022-9-1)
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https://www.pref.fukushima.lg.jp/site/portal/jyokyodojyotou.html (Accessed 2022-9-1)
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https://www.pref.fukushima.lg.jp/site/portal/ps-drinkingwater-monitoring.html (Accessed 2022-9-1)
13) Sugimura, et al., Analysis of Asian characteristics in the utilization of forest ecosystem services,
Proceedings of the 2010 Comprehensive Research Promotion Fund for Environmental Studies.
https://www.env.go.jp/policy/kenkyu/suishin/kadai/syuryo_report/h22/h22_suishin_report.html (Accessed2022-9-1)
14) Daiki Satoh, et al, Age-dependent dose conversion coefficients for external exposure to radioactive
cesium in soil, Journal of Nuclear Science and Technology Volume 53, 2016 - Issue 1, p.69-81.
15) ICRP, Age-dependent Doses to the Members of the Public from Intake of Radionuclides - Part 5
Compilation of Ingestion and Inhalation Coefficients, ICRP PUBLICATION 72 (1996)4516) IAEA, Generic Models for Use in Assessing the Impact of Discharges of Radioactive Substances to theEnvironment, Safety Reports Series No.19 (2001)17) Atomic Energy Society of Japan Standard Safety Assessment Methodology for Shallow Underground
Trench Disposal: 2013 (2014)18) IAEA, Handbook of Parameter Values for the Prediction of Radionuclide Transfer in Terrestrial andFreshwater Environments, Technical Reports Series No. 472 (2010)19) Nuclear Emergency Response Headquarters, Report of the Government of Japan to the IAEA
Ministerial Conference on Nuclear Safety - Accident at TEPCO's Fukushima Nuclear Power Station (2011)https://www.kantei.go.jp/jp/topics/2011/iaea_houkokusho.html (Accessed 2022-9-1)
20) Shiozawa, et al., Concentration and advection rate of radioactive cesium by depth in paddy field soils
in Fukushima Prefecture, Japan, RADIOISOTOPES, 60, 323-328 (2011).
21) Kato, et al., Depth distribution of 137Cs, 134Cs, and 131I in soil profile after Fukushima Dai-ichi Nuclear
Power Plant Accident, Journal of Environmental Radioactivity, Volume 111, Pages 59-64 (2012).
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46

Appendix A
Parameter (average and standard values) for the dose assessment
Table A1. Parameter for the dose assessment for all scenarios
No.

Parameter

Symbol

Unit

Value

Basis
The ratio of cesium-134 to cesium-

134Cs

①

-

Radionuclide
𝐶𝑎 (𝑖)

concentration

Fukushima Daiichi Nuclear Power

Bq/kgDW

137Cs②

137 present at the time of the

Plant accident was set to 1:1 and-physical attenuation was taken into
account in the calculations.

③

Shielding(screening)

𝑆𝑆 (𝑖)(outside)-

1-6
years old
factors for external
7-14⑥
exposure (134Cs)
years old
15-19⑦
years old
conversion

3.4×10-10

Sv/h
𝐷𝐶𝐹,𝐸𝑋𝑇 (𝑖)⑬conversion

Bq/kgDW⑰

weight buffer depth of 1 g/cm2 ofwere reported by Satoh et al. (2016) for
different ages. To obtain the dose

9.8×10-11

conversion factors in units of Bq/kg

1.3×10-10 (Sv/h per Bq/kgDW), the density of
1.1×10-10

soil ⑫ and the depth of soil to besampled (0.05 m) were multiplied by

1.0×10-10 the above factors.
-

kgDW/m3

1,600

US NRC「Regulatory Guide 1.109.
Revision 1」(1977)

1.9×10-8

Adult

1-6
⑭ factors for Internal
years old
7-14
⑮ exposure by ingestion
years old
(134Cs)15-19⑯
years old

2.7×10-10

per

1-6
Dose
conversion⑨
years old
factors for external
7-14⑩
exposure (137Cs)
years old
15-19⑪
years old
⑫ Density of soil in former TSS

exposure (mSv/h per kBq/m2) for a

2.9×10-10 cesium-134 and cesium-137 in soil

Adult

⑧

Dose

Safety Assessment Method for Near

2.7×10-10 Dose conversion factors for external

Adult
Dose

1

Surface Disposal : 2016, 2018④⑤

Atomic Energy Society of Japan,

factor

1.6×10-8
1.4×10-8
1.9×10-8
𝐷𝐶𝐹,𝐼𝑁𝐺 (𝑖)

Sv/Bq

Adult

Dose
conversion
1-6⑱ factors for Internal
years old
7-14
⑲ exposure by ingestion
years old
(137Cs)15-19⑳
years old

The values for adults, 1, 10, and 15

1.3×10-8 years old listed in the above document
1.2×10-8
1.0×10-8
1.3×10-8

47

ICRP publ.72(1996)

were used, respectively.

㉒㉓

4.2×10-4

Adult㉑

Soil intake per hour㉔

1-6
years old
7-14
years old
15-19
years old

1.7×10-3
𝑀𝑠

kgDW/hThe daily intake of soil ㉕-㉘ was

1.3×10-3 divided by 24 hours.
4.2×10-4
U.S. EPA, Exposure Factors

Adult

㉕

10

Handbook (2011), 2017, Chapter 5
revised.
Values for 12 year olds through adults

1-6
years
old

㉖
Daily intake of soil

40
-

㉗

used for the adults and 15-19 years

mgDW/day7-14
years old

listed in the above document wereold category. Values for 1-2 year olds
30

listed in the above document wereused for the 1-6 year old
category.Values for ages 6-12 years

15-19
years old㉘

10

described in the above document wereused for the 7-14 year old category.

Concentration factor of specific㉙ activity in the fine fraction (soil

𝑓𝑐,𝑠

-

2

IAEA SRS No.44, 2005

intake)㉚
Doseconversion

6.6×10-9

Adult

1-6
factors for Internal years old
7-14
by㉜ exposure
years oldinhalation (134Cs)
15-19㉝
years old

7.3×10-9

㉛

㉞
Dose

conversion

Adult

5.3×10-9

𝐷𝐶𝐹,𝐼𝑁𝐻 (𝑖)

Sv/Bq

1-6
factors for Internal years old
7-14
by㊱ exposure
years oldinhalation (137Cs)
15-19㊲
years old

ICRP publ.72(1996)

4.6×10-9 The values for adults, 1, 10, and 15
5.4×10-9 years old listed in the above document
3.7×10-9 were used, respectively.

㉟

4.4×10-9
4.6×10-9
Safety Assessment Method for Near

㊳ Breathing rate

𝐵𝐴

m3/h

1.2

Surface

Disposal:

2016,

AtomicEnergy Society of Japan , 2018㊴ Airborne dust concentration𝑑𝑅

kgDW/m3

𝑓𝑐,𝑑-5.0×10-7 IAEA SRS No.44 (2005)

Concentration factor of specific㊵ activity in the fine fraction(inhalation soil)

48

4

IAEA SRS No.44 (2005)

Table A2. Parameter for the dose assessment for Paddy scenario
No.

Parameter

Symbol

Unit

Value

Basis
Annual working hours for rice cultivation①

External exposure time andSoil ingestion time𝑡𝑠

𝑡𝑠,𝑖𝑛𝑔h/year183③

multiplied by the percentage ofworking hours at the former of TSS④.210 h/year×0.75=183 h/year

Based on the results of a survey conductedby the Decontamination Division of② Area of the former TSS

-

m2

8,511

Fukushima Prefecture, the average area offormer TSSs in the prefecture, where theoriginal land use was paddy fields, was set
at 8,511 m2.

From

the

Ministryof Agriculture,

Forestry and Fisheries' "Statistical SurveyofAgricultural

Management

Management

Statistics_

by Type ofFarming in 2019", we calculated the③

Annual working hours for ricecultivation-h/year210

working hours per person by area
category by dividing the working hours
by the total number of persons in rice
farming. The value for the area category
to which the area of the former temporarystorage area ② corresponds was used as
the average annual working hours.

The percentage of working hours in paddy
fields was obtained from the ‘working
hours by operation’ (i.e the different types④

Percentage of annual hours
worked in the former TSS

-

-

0.75

of work performed) in rice cultivationfrom the "Agricultural Management
Statistics Survey_Agricultural Production
Costs in 2019" by the Ministry ofAgriculture, Forestry and Fisheries.

49

From the National Health and Nutrition
Adult

⑤

54

Survey (2040) of the Ministry of Health,Labour and Welfare, the average daily
intake of rice for each age group was

1-6⑥
Annual riceconsumption⑦

35

years old

multiplied by 365 to obtain the annual
intake of rice. Furthermore, as this value

𝑀𝑓

FWkg/year

7-14

is the weight of the cooked rice, it was
61

years old

assumed to be the weight after cooking,multiplied by 0.5. Rice intake for adults
was taken as the average for those aged 20
and over. For age groups other than adults,

15-19

⑧

78

years old

the average value for the relevant age
group was used.

Transfer factor of radionuclide⑨ i from soil to agricultural

Bq/kgFW
𝑇𝑅,𝑓 (𝑖)product

per

0.04

IAEA SRS No19, 2001

Bq/kgDW
Safety Assessment Method for Near

⑩ Market dilution factor of food

𝐺𝑓

-

0.5

Surface Disposal: 2016, Atomic Energy
Society of Japan, 2018
Annual working hours for ricecultivation ③ were multiplied by thepercentage of annual hours worked in the⑪ Dust inhalation time

𝑡𝑠,𝑖𝑛ℎh/year53

former TSS ④ and the percentage ofannual working hours related to ricecultivation that are potentially dusty ⑫.
210 h/year×0.75×0.29=53 h/year
From the statistical data of the MAFF, we

Percentage of annual working⑫ hours related to rice cultivation

obtained the percentage of working hours--

that are potentially dusty

0.29

when the paddy fields were dry from theworking hours by operation in rice
farming.

50

Table A3. Parameter for the dose assessment for Cropland (vegetable) scenario
No.

Parameter

SymbolExternal exposure time,𝑡𝑠① Soil ingestion time and𝑡𝑠,𝑖𝑛𝑔Dust inhalation time

𝑡𝑠,𝑖𝑛ℎ

Unit

Value

Basis
Annual working hours for vegetable cultivation③

h/year858

multiplied by the percentage of working hours at
the former of TSS④.
1,112 h/year×0.73=858 h/year
Based on the results of a survey conducted by the
Decontamination② Area of the former TSS

-

m2

5,333

DivisionofFukushima

Prefecture, the average area of former TSSs in theprefecture, where the original land use wascropland, was set at 5,333 m2.
From the Ministry of Agriculture, Forestry and
Fisheries' "Statistical Survey of Agricultural
Management _ Management Statistics by Type ofFarming in 2019", we calculated the working③

Annual working time for
agricultural production-

h/year

1,112

hours per person by area category by dividing theworking hours by the total number of persons invegetable farming. The value for the area category
to which the area of the former of TSS ②
corresponds was used as the average annual
working hours.
From the statistical data of MAFF, the percentageof working hours in the field was obtained from

Percentage of annual④ hours worked in the

-

-

0.73

former TSS

the working hours of cucumbers by operation.
(Among the vegetables produced in Fukushima
Prefecture, cucumbers have the largest area undercultivation.)
From the National Health and Nutrition Survey in

Adult

⑤

102

2019 of the Ministry of Health, Labour andWelfare, the average daily intake of vegetable for⑥

Annual⑧

consumption

47years oldvegetable⑦

each age group was multiplied by 365 to obtain the

1-6

𝑀𝑓

annual intake of vegetable. The weight of cooked
vegetables was used conservatively, without

kgFW/year

taking into account the water content, as there are

7-14

88

years oldmany different methods of cooking. Vegetableintake for adults was taken as the average for those
aged 20 and over. For age groups other than adults,

15-19

89

years old

the average value for the relevant age group was
used.

51

Transfer factor of⑨ radionuclide i from soil

Bq/kgFW
𝑇𝑅,𝑓 (𝑖)to agricultural product⑩Market dilution factor of
food

per

0.04

IAEA SRS No19, 2001

Bq/kgDW
Safety Assessment Method for Near Surface
𝐺𝑓

-

0.5

Disposal: 2016, Atomic Energy Society of Japan ,
2018

52

Table A4. Parameter for the dose assessment for Cropland (flower) scenario
No.

Parameter

SymbolExternal exposure time,𝑡𝑠① Soil ingestion time and𝑡𝑠,𝑖𝑛𝑔Dust inhalation time

𝑡𝑠,𝑖𝑛ℎ

Unit

Value

Basis
Annual working hours for flower cultivationh/year852③ multiplied by the percentage of working
hours at the former of TSS④.
1,119 h/year×0.76=852 h/year
Based on the results of a survey conducted by
the Decontamination Division of Fukushima② Area of the former TSS

-

m2

5,333

Prefecture, the average area of former TSSs in
the prefecture, where the original land use wascropland, was set at 5,333 m2.
From the Ministry of Agriculture, Forestry
andFisheries'"Statistical

Surveyof

Agricultural Management _ Management
Statistics by Type of Farming in 2019", weAnnual working time
③ for agricultural

calculated the working hours per person by-h/year

1,119

production

area category by dividing the working hours
by the total number of persons in flower
farming. The value for the area category towhich the area of the former of TSS ②
corresponds was used as the average annual
working hours.
The percentage of working hours in the field
was obtained from the working hours forchrysanthemum cultivation by type of workfrom the Ministry of Agriculture, Forestry andPercentage of annual④ hours worked in the

Fisheries'
-

-

0.76

former TSS"Agricultural

Management

Statistics Survey_2007 Management Statistics
by Item". The area of cut branches is thelargest of the flowers produced in Fukushima
Prefecture, but as labour hours by operation
are not clear, the area of chrysanthemums, thesecond largest crop, was selected.

53

Table A5. Parameter for the dose assessment for Orchard scenario
No.

Parameter

SymbolExternal exposure time,𝑡𝑠① Soil ingestion time and𝑡𝑠,𝑖𝑛𝑔Dust inhalation time

𝑡𝑠,𝑖𝑛ℎ

Unit

Value

Basis
Annual working hours for fruit cultivation ③h/year540

multiplied by the percentage of working hours at
the former of TSS④
597 h/year×0.90=540 h/year
Based on the results of a survey conducted by the
Decontamination② Area of the former TSS

-

m2

5,333

DivisionofFukushima

Prefecture, the average area of former TSSs in theprefecture, where the original land use wascropland, was set at 5,333 m2.
From the Ministry of Agriculture, Forestry and
Fisheries' "Statistical Survey of Agricultural
Management _ Management Statistics by Type ofFarming in 2019", we calculated the working③

Annual working time for
agricultural production-

h/year597

hours per person by area category by dividing theworking hours by the total number of persons infruit farming. The value for the area category towhich the area of the former of TSS (2)corresponds was used as the average annual
working hours.
From the statistical data of MAFF, the percentage

Percentage of annual④ hours worked in theof working hours in the vineyard was obtained
-

-

0.90

former TSS

from the working hours of peaches by operation.
*Among the fruits produced in Fukushima
Prefecture, peaches have the largest cropping area.

Adult

⑤

From the National Health and Nutrition Survey in

1-6⑥
Annual intake
⑦

37
34

years old
7-14

of fruits

𝑀𝑓

kgFW/year

Welfare, the average daily intake of fruit for each27

years old24

years old
Transfer factor of⑨ radionuclide i from soil
to fruit

age group was multiplied by 365 to obtain theannual intake of fruit.

15-19

⑧

2019 of the Ministry of Health, Labour and

Bq/kgFW
𝑇𝑅,𝑓 (𝑖)

per

0.04

Bq/kgDW

54

IAEA SRS No19, 2001

⑩Market dilution factor offood

Atomic𝐺𝑓-

0.5

EnergyofJapan,

SafetyAssessment Method for Near Surface Disposal :2016, 201855

SocietyTable A6. Parameter for the dose assessment for Pasture (milk cow) scenario
No

Parameter

Symbol

Unit

Value

Basis

.
From the Ministry of Agriculture, Forestry and
Fisheries'"Statistical

Surveyof

Agricultural

External exposureManagement _ Management Statistics by Type oftime,

Farming in 2019", the working hours per person were

Soil 𝑡𝑠① ingestion time and 𝑡𝑠,𝑖𝑛𝑔
Dusth/year

1,244

inhalation 𝑡𝑠,𝑖𝑛ℎcalculated by dividing the working hours by the total
number of people in each category for raising milkcows. The exposure time is defined as the value of thetimenumber of milk cows in the number of cows category
to which the number of milk cows (2) corresponds.

②-

cows raisedhead④ Annualintake ofmilk
products⑥

41.7

average number of milk cows per household raised in
Fukushima Prefecture.

Adult

③

⑤

From the statistical data of MAFF, we selected the

Number of milk

1-6
years
old
7-14
years
old
15-19
years
old

23
From the National Health and Nutrition Survey in52
𝑀𝑓

2019 of the Ministry of Health, Labour and Welfare,

kgFW/year

the average daily intake of milk for each age group was

92

multiplied by 365 to obtain the annual intake of milk.
36

IAEA SRS No19, 2001
In Fukushima Prefecture, measures to suppress
absorption of radioactive cesium by fertilization withTransfer factor of⑦ radionuclide i

Bq/kgDW
𝑇𝑅,𝑝 (𝑖)from soil to grassper1

Bq/kgDW

exchangeable

potassium

Fukushima

Prefecture's

areencouraged"Guidelines

byfor

Decontamination and Technical Measures Concerning
Measures against Radioactive Cesium in Agricultural
Crops," but the transfer coefficient on the left does nottake these measures into account.

⑧

Livestock feedintake𝑀𝑔

kgDW/day

16

𝑓𝑟

-

0.12

IAEA TRS No364, 1994

Market dilution⑨ factor of feed

Annual pasture production⑪ was divided by Annual
requirement of feed (pasture)⑩.

(grass)56

The feed intake per cow⑧ and the number of dairy

Annual⑩ requirement of-

kgDW/year

243,528

cows② were calculated as follows.
16 kgDW/day × 42 × 365 day

feed (pasture)= 243,528 kgDW/year
The area available for pasture seeding⑫ and the⑪annual pasture yields⑮ and the Moisture percentage

Annual pasture-production

kgDW/year

29,741of pasture ⑯ were used as follows.
54,142 m2×3.37 kgFW/m2 ×(1-0.837)= 29,741 kgDW/year⑫

Area available for
pasture seeding-m2

54,142Difference between the area of the former TSS ⑬
and the area of the cattle barn ⑭.
Based on the results of a survey conducted by the⑬

Area of the former
TSS

Decontamination Division of Fukushima Prefecture,-m2

54,371the average area of former TSSs in the prefecture,
where the original land use was pasture, was set at54,371 m2.
According to the "Grassland Development andImprovement Project Plan Design Standards" (2021)
by the Japan Grassland and Livestock Seed

⑭ Area of barn-

m2

Association, the area required per dairy cow between

229

16 and 24 months of age is 5.5 m2. This was multipliedby 41.7 cows, which is the number of dairy cows perhousehold②

in dairy farms in Fukushima

Prefecture.
Calculated based on the national average of yields per⑮

1,000 m2 of grass in the "Crop Survey 2020 (Regular

Annual pasture-yieldskgFW/m2

3.37

Crops, Forage Crops, and Handicraft Crops)" (2020)of the Ministry of Agriculture, Forestry and Fisheries
of Japan.
The average value of 83.7 % was used for Italian

Moisture⑯ percentage of

-

-

0.837

leaves is considered to be 84.6 % and 82.8 %,pasturerespectively, according to Yamashita, et al. (1968).

Transfer⑰ fromryegrass, since the moisture percentage of stems andfactorfeed

to 𝑇𝐴𝑀 (𝑖)day/kgFW

0.01

-

0.5

IAEA SRS No19, 2001

livestock products⑱

Market dilution
factor of food

𝐺𝑓Atomic Energy Society of Japan, Safety Assessment
Method for Near Surface Disposal: 2016, 201857

Table A7. Parameter for the dose assessment for Pasture (beef cattle) scenario
No.

Parameter

Symbol

Unit

Value

Basis
From the Ministry of Agriculture, Forestry and
Fisheries' "Statistical Survey of Agricultural
Management _ Management Statistics by Type ofFarming in 2019", the working hours per person

External exposure time,𝑡𝑠① Soil ingestion time and𝑡𝑠,𝑖𝑛𝑔Dust inhalation time

𝑡𝑠,𝑖𝑛ℎh/year928

were calculated by dividing the working hours by
the total number of people in each category forraising beef cattle. The exposure time is defined as
the value of the number of beef cattle in thenumber of cattle category to which the number ofbeef cattle ② corresponds.

②

Number of beef cattle
raisedFrom the statistical data of MAFF, we selected the
-

head

28.9

average number of beef cattle per household
raised in Fukushima Prefecture.

Table A8. Parameter for the dose assessment for Managed Forest scenario
No.

Parameter

Symbol

Unit

Value

Basis
Labor hours per person per area size were obtained from the
Ministry of Agriculture, Forestry and Fisheries' "Survey ofForestry

Management

Statistics_Reporton

Forestry

Management Statistics in 2008," based on the number ofExternal

workers per management unit by area size and labor hours for

exposure time,𝑡𝑠① Soil ingestion

𝑡𝑠,𝑖𝑛𝑔time and Dust

𝑡𝑠,𝑖𝑛ℎforestry, material production (logging, etc.), and otherh/year313

operations. The average area of the temporary storage sites
where the original land use was forest was 118 a. However,since there is no area classification that matches this, the values

inhalation time

between 2,000 and 5,000 a in the above statistical data wereused.
(Even taking into account the physical attenuation ofradioactive cesium, the most conservative result is theassessment assuming logging.)
Based on the results of a survey conducted by the②

Area of theformer TSS-

m2

11,775

Decontamination Division of Fukushima Prefecture, theaverage area of temporary storage sites in the prefecture wasset at 11,775 m2.

58

Table A9. Parameter for the dose assessment for Residence scenario
No.

Parameter

③

Unit

Value

1-6
External

years old

exposure

7-14

6,998
𝑡𝑠

The annual time spent at home ⑤ to ⑧
minus the annual activity time related to theh/year5,315

time (indoor) years old

kitchen garden ⑩ to ⑬ was used as theindoor external exposure time.

15-19

④

Basis

5,778

Adult

①
②

Symbol

5,315

years old

From
Adult

⑤

5,920

the

NHK

Broadcasting

CultureResearch Institute's National Survey on
Living Time (2020), we calculated the annual
amount of time spent at home by age, gender,and occupation by multiplying the average

1-6

⑥

7,140

years old

time spent at home per day on weekdays,
Saturdays, and Sundays by the number ofweekdays, Saturdays, and Sundays (national
holidays are counted as Sundays) in FY2020.

7-14

⑦

5,400

years old
Annual-home time

In the adult age group, the value for females
in their 40s, which has the largest value
among the categories of males and females inh/yeartheir 40s and above, was used. (This isbecause it is known that the average age of
people in Fukushima Prefecture is 49.4 years
old according to the National Institute ofPopulation and Social Security Research

15-19

⑧

5,400

years old

"Demographic Data Book (2021 edition)").
For the age groups 7-14 and 15-19, the values
for teenage males were used because they
were larger when compared to the values forteenage males and females. To account forvariation among years, rounding up to thenearest 1 was performed.

⑨

This is based on the Nuclear Safety

Shielding (screening)
factor (inside)

𝑆𝑆 (𝑖)-

0.4

Commission's "Disaster Prevention Measuresfor Nuclear Facilities" (June 1980).

59

From Takatori et al. "FY 2008 National Land
Policy Related Research Support Project:
Adult

⑩

142

Report on Research Results Calculation and
Visualization of Workload for Landscape

External

Management for Appropriate Management of
1-6

exposure⑪ time,

Soil

years

142

old

ingestion
time

National Land - Targeting Eight Central Japan

andPrefectures", it is the average annual work
hours for home gardens by age group. For
adults, we used values for people in their 40s

𝑡𝑠

Dust

7-14

𝑡𝑠,𝑖𝑛𝑔⑫ inhalation

years

𝑡𝑠,𝑖𝑛ℎtime

oldh/year(because the average age in Fukushima
85

Prefecture is known to be 49.4 years
according to the National Institute of(Outdoor,

Population and Social Security Research's

kitchen

Demographic Data Book (2021 edition)). The

garden)average age is 49.4 years old. For the age

15-19
years

⑬

85

group 1-6 years old, as there is nocorresponding age group, it is assumed thatold

the children are accompanied by an adult andthe value is taken as 40s.
From the National Health and Nutrition
Adult

⑭

Annualyears oldvegetable

7-14

47
𝑀𝑓

of vegetable for each age group was
multiplied by 365 to obtain the annual intake

kgFW/year
88

consumption years oldof vegetable. Vegetable intake for adults was
taken as the average for those aged 20 andover. For age groups other than adults, the

15-19

⑰

Survey in 2019 of the Ministry of Health,Labour and Welfare, the average daily intake

1-6

⑮

⑯

102

89

years old

average value for the relevant age group wasused.

Transfer factor of

Bq/㎏ FW⑱ radionuclide i from soil 𝑇𝑅,𝑓 (𝑖)to agricultural product⑲

Market dilution factor
of foodper

0.04

IAEA SRS No19, 2001

Bq/㎏ DW
Atomic Energy Society of Japan, Safety
𝐺𝑓

-

0.1

Assessment

Methodfor

Shallow

Underground Trench Disposal: 2013 (2014).

60

Table A10. Parameter for the dose assessment for Park scenario
No.

Parameter

Symbol

Unit

Value

Basis
From the Ministry of Land, Infrastructure,
Transport and Tourism's 2014 Survey of Urban

Adult

①

180

Park Use (2015), the average daily time spent incity parks by age group on weekdays and holidays
was multiplied by the number of days visited toobtain the annual time spent in parks. The numberof days of visit was calculated on the assumption② External
exposurethat the average frequency of visit was 2-3 times a

1-6

240

years oldweek on weekends and once a weekday. For thetime, Soil𝑡𝑠,𝑖𝑛𝑔time and③ inhalation

adult category, the exposure time was set using the𝑡𝑠

ingestion

Dustweek, so the respondents visited the park twice ah/yearvalue for adults (19-64 years). For the 1-6 age
group, the values are those before school age. For

𝑡𝑠,𝑖𝑛ℎ7-14

220

years oldthe 7-14 age group, we used the value for the upperprimary schools students (grades 4-6), who havetime

the greatest annual time in preschool among thelower primary schools students (grades 1-3), upperprimary schools students (grades 4-6), and juniorhigh and high school students and others (ages 12-

④

15-19

210

years old18). For the 15-19 age group, the values are thoseof junior high and high school students and others(12-18 years). To account for variation among
years, rounding up to the nearest 1 was performed.

61

Appendix B
Method of setting conservative parameter values
External exposure time(𝒕𝒔 ), Soil ingestion time in former TSS (𝒕𝒔,𝒊𝒏𝒈), Dust inhalation timein former TSS (𝒕𝒔,𝒊𝒏𝒉)
The following were considered for each scenario. The soil ingestion time (𝑡𝑠,𝑖𝑛𝑔 ) and the dust
inhalation time in former TSS (𝑡𝑠,𝑖𝑛ℎ ) are linked to the external exposure time⁡(𝑡𝑠 ), and thesethree parameters have the same value except for the Paddy and Residence scenarios.
Paddy
The working hours in the former TSS per person for each area size category were calculated
based on the total annual working hours (average), the total number of people (average) and theratio of working hours by task (average) for each area size category in the statistical data of the
Ministry of Agriculture, Forestry and Fisheries 1, 2, and used as the external exposure time and thesoil ingestion time in the Paddy scenario. The dust inhalation time was defined as the external
exposure time and the soil ingestion time multiplied by the ratio (average value) of the time when
the paddy field was dry (time when dust could be generated).
Of the working hours per worker per area size category calculated as above, the values for the
300,000-500,000 m2 category, that is the longest working hours in the largest TSS area size of
363,000 m2 or less were used conservatively. The formulas for deriving the parameter values are
as follows.
Paddy（𝑡𝑠 , 𝑡𝑠,𝑖𝑛𝑔 ）: External exposure time and soil ingestion time in the Paddy scenario
Paddy（𝑡𝑠 , 𝑡𝑠,𝑖𝑛𝑔 ）= total annual working hours ÷ total number of people × Percentage of timespent in paddy fields out of the total time spent on rice cultivation
Paddy（𝑡𝑠,𝑖𝑛ℎ ）: Dust inhalation time in the Paddy scenario
Paddy（𝑡𝑠,𝑖𝑛ℎ ）= total annual working hours ÷ total number of people × Percentage of time spentin paddy fields out of the total time spent on rice cultivation × Percentage oftime that paddy fields are dry per year
Cropland (vegetable and flower) and Orchard
The working hours in the former TSS per person for each area category were calculated basedon the total annual working hours (average), the total number of people (average), and the ratioof working hours by work (average) for each area category in the statistical data of the Ministryof Agriculture, Forestry and Fisheries 1, 3, and the external exposure time, the soil ingestion time
and the dust inhalation time in the Cropland (vegetables and flowers) and Orchard scenarios were
used.
62

Of the working hours per worker per area size category calculated as above, the values for thearea size category (the values of 100,000 to 150,000 m2 for the Cropland (vegetable) scenario,
30,000 m2 or more for the Cropland (flower) scenario, and 30,000 to 50,000 m 2 for the Orchard
scenario), that is the longest working hours in the largest TSS area size of 363,000 m2 or less wereused conservatively. The formula for deriving the parameter values is as follows.
Cropland and Orchard（𝑡𝑠 , 𝑡𝑠,𝑖𝑛𝑔 , 𝑡𝑠,𝑖𝑛ℎ ）: External exposure time, etc. in Cropland and Orchard
scenarios
Cropland and Orchard（𝑡𝑠 , 𝑡𝑠,𝑖𝑛𝑔 , 𝑡𝑠,𝑖𝑛ℎ ）= total annual working hours ÷ total number of people
× Percentage of time spent in the field growing crops
Pasture (milk cow and beef cattle)
The working hours per person in the former TSS for each head number category were calculated
based on the total working hours (average) and the total number of persons (average) for eachhead number category in the statistical data 1 provided by the Ministry of Agriculture, Forestry
and Fisheries, and used as the external exposure time, the soil ingestion time and the dust
inhalation time in the Pasture (milk cow and beef cattle) scenario. Since the percentage of working
hours in pastures out of total working hours is unknown, it was assumed that the workers werealways in pastures during working hours.
Of the labor hours per person for each head number category calculated as above, the values forthe head number category (the values of over 200 head for the Pasture (milk cow) scenario andover 500 head for the Pasture (beef cattle) scenario), that is the longest working hours in thehighest head (over 200 head or less for the Pasture (milk cow) scenario and over 500 head or lessfor the Pasture (beef cattle) scenario*) were used conservatively. The formula for deriving theparameter values is as follows.
Pasture（𝑡𝑠 , 𝑡𝑠,𝑖𝑛𝑔 , 𝑡𝑠,𝑖𝑛ℎ ）: External exposure time, etc. in Pasture (milk cow and beef cattle)
scenarios
Pasture（𝑡𝑠 , 𝑡𝑠,𝑖𝑛𝑔 , 𝑡𝑠,𝑖𝑛ℎ ）= total annual working hours ÷ total number of people
Managed Forest
The working hours per person in the former TSS for each area size category were calculated,based on the total working hours and the total number of people involved in forest growing,
logging, and other works for each area size category in the statistical data provided by the Ministryof Agriculture, Forestry and Fisheries 4, and used as the external exposure time, the soil ingestion
time and the dust inhalation time in the Managed Forest scenario. Since the percentage of working
hours in forest out of total working hours is unknown, it was assumed that the workers were63
* It is known that there are some dairy cattle farms with more than 200 head of dairy cattle and beef cattle farms with more than 500
head of beef cattle in Fukushima Prefecture5).

always in forest during working hours.
Of the annual per capita labor hours per area size category calculated as above, the longest percapita labor hours in the area size category below 363,000 m2 (the maximum TSS area) were usedas the conservative exposure hours. However, the smallest area category in the statistical data of
the Ministry of Agriculture, Forestry and Fisheries 31 is between 200,000 ~ 500,000 m2, resulting
in the same values for the standard and conservative parameters.
Managed Forest（𝑡𝑠 , 𝑡𝑠,𝑖𝑛𝑔 , 𝑡𝑠,𝑖𝑛ℎ ）: External exposure time, etc. in Managed Forest scenario
Managed Forest（𝑡𝑠 , 𝑡𝑠,𝑖𝑛𝑔 , 𝑡𝑠,𝑖𝑛ℎ ）= total annual working hours ÷ total number of people
Residence
Although there are two exposure areas in the residence, indoor and outdoor, we thought that a
conservative value for the indoor area, which accounts for the majority of the exposure time,
would be sufficient to consider the uncertainties in the overall Residence scenario.
The annual time spent at home was calculated from the average daily time spent at home on
weekdays, Saturdays, Sundays and public holidays for each age, gender, and occupation in thestatistical data of the NHK Broadcasting Culture Research Institute 6, less the annual activity time(average) related to home vegetable gardening (survey by Takatori et al.7), and the value was usedas the indoor external exposure time in the Residence scenario. Since the statistical data of the
NHK Broadcasting Culture Research Institute showed the mean and standard deviation of thetime spent at home per day, the value obtained by adding the mean value and standard deviation
value was used as the conservative exposure time. In the adult age categories, for the values
showed by the statistical data for males and females in their twenties and above, the value of
females in their seventies with a large value of the sum of the mean and standard deviation values
was used as conservative exposure time. The values used for the following groups were also thecorresponding values from the same statistical data. For the age groups of 7-14 and 15-19 years
old, the values for teenage males and females with the highest value of the sum of the mean andstandard deviation values were used as conservative exposure time. For the age group of 1-6 years
old, it was assumed that they always spend time with their parents, and the mean value of thehousewife's home time plus the standard deviation value was used as a conservative exposure
time. However, for adults and the age group 1-6 years old, the sum of the mean and standard
deviation values exceeded 8,760 hours, which is the total time spent at home per year, so 8,760
hours was used as a conservative annual time spent at home. The formulas for deriving theparameter values are as follows.
Residence（𝑡𝑠 ）: Indoor external exposure time in Residence scenario
Residence（𝑡𝑠 ）= Annual time spent at home on weekday, Saturday, Sunday, and public
64holiday - Annual activity time in the kitchen garden
Annual time spent at home on weekday = time spent at home per weekday × number of weekdays
per year
Annual time spent at home on Saturday = time spent at home per day on Saturday
× number of Saturdays per year
Annual time spent at home on Sunday and public holiday= Time spent at home per day on Sundays × Number of Sundays and public holidays per year
*The soil ingestion and the dust inhalation were assumed not to occur indoors for the assessmentin the present study.
Park
The annual time spent in the park was calculated from the average time spent in the park on
weekdays, Saturdays and Sundays and public holidays for each age group and the frequency ofvisits to the park in the statistical data of the Ministry of Land, Infrastructure, Transport andTourism 8, and was used as the external exposure time, the soil ingestion time and the dust
inhalation time in the Park scenario.
The Ministry of Land, Infrastructure, Transport and Tourism's statistical data indicates that there
is a certain percentage of each age group that visits the park almost every day, so we calculated
the annual time spent in the park based on the assumption that they visit the park every day, which
are these conservative values. For the adult age group, the time was set using the value for adults(elderly) value showed by the statistical data. The values used for the following groups were also
the corresponding values from the same statistical data. For the age group of 1-6 years old, thevalue before school age was used as a conservative exposure time. For the age group of 7-14 years
old, among the lower elementary school students (grades 1-3), upper elementary school students(grades 4-6), and middle school and high school students, etc. (ages 12-18), the value for theupper elementary school students (grades 4-6), who have the largest annual time in school, wasused as a conservative exposure time. For the age group of 15-19 years old, the value for juniorhigh school students, high school students, etc. (12-18 years old) and adults (19-64 years old),which has the maximum annual time in school, was used as a conservative exposure time. The
formulas for deriving the parameter values are as follows.
Park（𝑡𝑠 , 𝑡𝑠,𝑖𝑛𝑔 , 𝑡𝑠,𝑖𝑛ℎ ）: External exposure time, etc. in Park scenarioPark（𝑡𝑠 , 𝑡𝑠,𝑖𝑛𝑔 , 𝑡𝑠,𝑖𝑛ℎ ）= Annual time spent in preschool on weekdays + Annual time spent inpreschool on holidays

65Annual time spent in preschool on weekdays = time spent in preschool per day on weekdays x
number of weekdays per year
Annual time spent at home on holidays = Time spent at school per day on holidays × Number ofSaturdays, Sundays, and holidays per year
Annual amount of food intake（𝑴𝒇 ）The annual intake of food for each age group in the Paddy, Cropland (vegetables), Orchard andPasture (milk cow) scenarios was calculated from the average daily intake by food type for eachage group in the statistical data 9 of the Ministry of Health, Labor and Welfare. The intake of ricefor the Paddy scenario, vegetables for the Cropland (vegetable) scenarios, fruits for the Orchard
scenario, and milk for the Pasture (milk cow) scenario were chosen. For the rice, the intake wasset at one-half 10 the value in the statistical data, considering that it was the weight of rice after
cooking. Since the statistical data 9 of the Ministry of Health, Labor and Welfare (MHLW) shows
the mean and standard deviation values, the sum of the mean and standard deviation values wasused as a conservative food intake. For adults, conservative food intake values were defined using
the value for the age group in which the sum of the mean and standard deviation values was thelargest (20-29 years for rice and milk cow, 70-79 years for vegetables and fruits). For age groups
other than adults, conservative food intake was defined as the sum of the mean and standard
deviation values for ages 1-6 years old, 7-14 years old, and 15-19 years old, respectively. The
formulas for deriving the parameter values are as follows.
Paddy（𝑀𝑓 ）: annual food intake in Paddy scenario
Paddy（𝑀𝑓 ）= daily rice Intake × 365 ÷ 2
Other than paddy（𝑀𝑓 ）: annual food intake for Cropland (vegetables), Orchard, and Pasture(milk cow) scenarios
Other than paddy（𝑀𝑓 ）= daily intake × 365
Market dilution factor of food（𝑮𝒇 ）For the market dilution factor（𝐺𝑓 ）in the Paddy, Cropland (vegetables), Orchard, and Pasture(milk cow) scenarios, although the AESJ standard 11 recommends that the market dilution factorof the crop which is considered in the internal exposure model for ingestion from food anddrinking water is 0.5, the present study used 1 for the conservative case based on the assumptionthat all the specific food consumed in a year originated from the TSS sites.
Market dilution factor of feed（𝒇𝒓 ）With respect to the conservative external exposure time in the Pasture (milk cow) scenario, the66number of is over 200. When the amount of grass intake per day per cow is 16 kgDW 12, a total
dry weight of grass of 1,168,000 kg is required per year for 200 cows. The area where grass canbe cultivated in the TSS is the area subtracting the area of the barn. In the cattle barn, since thearea required for each dairy cow aged 16-24 months is 5.5 m2 13, 1,100 m2 are required for 200
dairy cows. Therefore, the maximum area of the site of the TSS is 363,000 m2, so that the area inwhich grass can be sown is 361,900 m2.
The average annual yield per unit area of grass is 3.54 kg FW/m2 at the maximum according to
the FY2014-FY2019 statistical data 14, 15, 16, 17, 18, 19, 20 of the Ministry of Agriculture, Forestry and
Fisheries. In the case of Italian ryegrass, it is revealed by Yamashita, et al. 21 that the water content
of the stem and leaf sheath is 84.6 % and the leaf blade is 82.8 %. Therefore, by considering that
83.7 %, which is the average value of these two values, is the water content of the grass, theannual average yield per unit area of the grass was calculated as 0.58 kg DW/m2.
When the average annual yield of grass is 0.58 kgDW/m2, the total annual yield for a pasturearea of 361,900 m2 will be 208,824 kgDW. This is 18% of 1,168,000 kg which is the annual
required amount of grass to feed 200 cows, so the conservative value for the market dilution factor
for grass was set at 0.18.
Reference
1)

Ministryof Agriculture,

Forestry

andFisheries,

Surveyof Agricultural

Management

Statistics_Management Statistics by Farming Type in 2019https://www.e-stat.go.jp/statsearch/files?page=1&layout=datalist&toukei=00500201&tstat=000001013460&cycle=7&year=20190&
month=0&tclass1=000001150647&tclass2=000001156387&tclass3=000001156388 (Accessed 2022-9-1)
2)

Ministryof Agriculture,

Forestry

andFisheries,

Surveyof Agricultural

Management

Statistics_Production Cost of Agricultural Products in 2019https://www.e-stat.go.jp/statsearch/files?page=1&layout=datalist&toukei=00500201&tstat=000001013460&cycle=7&year=20190&
month=0&tclass1=000001013651&tclass2=000001019774&tclass3=000001152427 (Accessed 2022-9-1)
3) Ministry of Agriculture, Forestry and Fisheries, Survey of Agricultural Management_Management
Statistics by Commodity in 2007https://www.e-stat.go.jp/statsearch/files?page=1&layout=datalist&toukei=00500201&tstat=000001013460&cycle=7&year=20070&
month=0&tclass1=000001013649&tclass2=000001020117&tclass3=000001034993 (Accessed 2022-9-1)
4) Ministry of Agriculture, Forestry and Fisheries, Survey of Forestry Management Statistics_Report on
Survey of Forestry Management Statistics, 2018https://www.maff.go.jp/j/tokei/kouhyou/rinkei/#r (Accessed 2022-9-1)
5) Ministry of Agriculture, Forestry and Fisheries, Livestock Production Statistics 2021_Livestock67

Production Statistics 2021
https://www.e-stat.go.jp/statsearch/files?page=1&layout=datalist&toukei=00500222&tstat=000001015614&cycle=7&year=20210&
month=0&tclass1=000001020206&tclass2=000001161726 (Accessed 2022-9-1)
6) NHK Broadcasting Culture Research Institute, National Living Time Survey (2020)
https://www.nhk.or.jp/bunken/yoron-jikan/ (Accessed 2022-9-1)
7) Takatori, et al., FY 2008 Research Report of the Research Support Project for National Land Policy
Calculation and Visualization of Scenic Area Management Workload for Appropriate Land Management:
A Case Study of Eight Prefectures in the Chubu Region.
https://www.mlit.go.jp/kokudoseisaku/kokudoseisaku_fr1_000048.html (Accessed 2022-9-1)
8) Ministry of Land, Infrastructure, Transport and Tourism, 2014 Survey of Urban Park Usage
https://www.mlit.go.jp/toshi/park/toshi_parkgreen_tk_000039.html (Accessed 2022-9-1)
9) Ministry of Health, Labour and Welfare, National Health and Nutrition Examination Survey (2019)https://www.mhlw.go.jp/bunya/kenkou/kenkou_eiyou_chousa.html (Accessed 2022-9-1)
10) Ogawa, Study on Cooking Characteristics of Sekihan (2nd Report): Investigation of Cooking
Conditions of Sekihan, Journal of Home Economics of Japan, Vol.46 No.6 531～537 (1995)
11) General Atomic Energy Society of Japan, Standard of the Atomic Energy Society of Japan Safety
Assessment Methodology for Shallow Underground Disposal: 201612) IAEA, Handbook of Parameter Values for the Prediction of Radionuclide Transfer in Temperate
Environments, Technical Report Series 364, Technical Reports Series No.364 (1994)
13) Japan Grassland and Livestock Seeds Association, Planning and Design Standards for Grassland
Development and Improvement Projects (2021)
14) Ministry of Agriculture, Forestry and Fisheries, Crop Survey_2020 Crop statistics (common crops, feedcrops, industrial crops) (2020)
https://www.e-stat.go.jp/statsearch/files?page=1&layout=datalist&toukei=00500215&tstat=000001013427&cycle=7&year=20200&
month=0&tclass1=000001032288&tclass2=000001032753&tclass3=000001150347 (Accessed 2022-9-1)
15) Ministry of Agriculture, Forestry and Fisheries, Crop Survey_2019 Crop statistics (common crops, feedcrops, industrial crops) (2019)https://www.e-stat.go.jp/statsearch/files?page=1&layout=datalist&toukei=00500215&tstat=000001013427&cycle=7&year=20190&
month=0&tclass1=000001032288&tclass2=000001032753&tclass3=000001137506 (Accessed 2022-9-1)
16) Ministry of Agriculture, Forestry and Fisheries, Crop Survey_2018 Crop statistics (common crops, feedcrops, industrial crops) (2018)https://www.e-stat.go.jp/statsearch/files?page=1&layout=datalist&toukei=00500215&tstat=000001013427&cycle=7&year=20180&
month=0&tclass1=000001032288&tclass2=000001032753&tclass3=000001125936 (Accessed 2022-9-1)

6817) Ministry of Agriculture, Forestry and Fisheries, Crop Survey_2017 Crop statistics (common crops, feedcrops, industrial crops) (2017)https://www.e-stat.go.jp/statsearch/files?page=1&layout=datalist&toukei=00500215&tstat=000001013427&cycle=7&year=20170&
month=0&tclass1=000001032288&tclass2=000001032753&tclass3=000001112815 (Accessed 2022-9-1)
18) Ministry of Agriculture, Forestry and Fisheries, Crop Survey_2016 Crop statistics (common crops, feedcrops, industrial crops) (2016)
https://www.e-stat.go.jp/statsearch/files?page=1&layout=datalist&toukei=00500215&tstat=000001013427&cycle=7&year=20160&
month=0&tclass1=000001032288&tclass2=000001032753&tclass3=000001095996 (Accessed 2022-9-1)
19) Ministry of Agriculture, Forestry and Fisheries, Crop Survey_2015 Crop statistics (common crops, feedcrops, industrial crops) (2015)
https://www.e-stat.go.jp/statsearch/files?page=1&layout=datalist&toukei=00500215&tstat=000001013427&cycle=7&year=20150&
month=0&tclass1=000001032288&tclass2=000001032753&tclass3=000001068075（Accessed 2022-9-1）20) Ministry of Agriculture, Forestry and Fisheries, Crop Survey_2014 Crop statistics (common crops, feedcrops, industrial crops) (2014)
https://www.e-stat.go.jp/statsearch/files?page=1&layout=datalist&toukei=00500215&tstat=000001013427&cycle=7&year=20140&
month=0&tclass1=000001032288&tclass2=000001032753&tclass3=000001068111 (Accessed 2022-9-1)
21) Yamashita, et al., Drying Characteristics of Pasture Grasses (Part 1) - Drying Rate by Site and Cut
Length, Journal of the Japanese Society of Agricultural Machinery and Food Engineers, Volume 30 Issue 1
Pages 24-28,41 (1968)

69

Appendix C
Conversion method from air dose rate in the former TSS
to cesium-137 concentration in topsoil
To estimate the cesium-137-derived air dose rate in the former TSS, the cesium-137 derived air
dose rate was calculated from the air dose rate in the former TSS and the ratio of cesium-137 tocesium-134 at the time t since the accident, as shown in Equation (C1). The cesium-137
concentration was then calculated by dividing the cesium-137 derived air dose rate by theconversion factor from the cesium-137 concentration in soil to the air dose rate, as in Equation(C2). In the present study, it was assumed that the relaxation mass depth β becomes 1 g/cm2 forthe distribution of cesium on the site of the TSS. From the report of Satoh et al. 1, the conversion
factor of cesium-137 in soil to the air dose rate for β = 1 was set to 2.11×10-6 mSv/h per kBq/m2.
The coefficient was multiplied by the soil density of 1.6 gDW/cm3 2 and soil depth of 5.0 cm toobtain the conversion factor of 1.7×10-10 (Sv/h)/(Bq/kgDW).

𝐷137 (𝑡) = (𝐷(𝑡) − 𝐷𝐵𝐺 )𝐷

𝐶𝑠137 (𝑡) = 𝐷 137

𝑡
1
2
𝑡
𝑡
1 𝑇1341𝑘( )+( )𝑇137
2
2( )𝑇137= (𝐷(𝑡) − 𝐷𝐵𝐺 )1𝑡1( )𝑇134
𝑘 2 𝑡 +1
1( )𝑇137
2

(𝑡)

(C1)

(C2)

𝐶𝐹,𝐴𝐷𝑅In Eq. (C1), when D(t) is less than DBG, Cs137=0. The parameters shown in Eqs. (C1) and (C2) are
as follows.
𝐷137 (𝑡)：Air dose rate calculated based on Cesium-137 at the position of 1 m height from theground level when time is t [Sv/h]
𝐶𝑠137 (𝑡)：Concentration of Cesium-137 in soil［Bq/kgDW］
𝐷(𝑡)：Air dose rate at time t obtained by questionnaire survey [Sv/h]
𝐷𝐵𝐺 ：Air dose rate based on the natural nuclides (The value of municipalities reported by Andoet al.3) [Sv/h]𝑘：Ratio of air dose rates of Cesium-134 to Cesium-137 at the same concentration, which is 2.7［-］
𝑡：Elapsed time from accident occurrence (March 15, 2011)［y］
𝑇134：Half life of Cesium-134, which is 2.0648 y 4
𝑇137：Half life of Cesium-137, which is 30.1671 y 4
𝐷𝐶𝐹,𝐴𝐷𝑅 ：Conversion factor to air dose rate from Cesium-137 concentration in soil, which is
1.7×10-10 (Sv/h)/(Bq/kgDW)
70

Reference
1) Daiki Satoh, et al, Age-dependent dose conversion coefficients for external exposure to radioactive
cesium in soil, Journal of Nuclear Science and Technology Volume 53, 2016 - Issue 1, p.69-81.
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effluents for the purpose of evaluating compliance with 10 CFR Part 50, Appendix I, (Regulatory Guide
1.109. Revision 1), (1977)
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Traveling Survey Measurements Using KURAMA-II, Nippon Genshiryoku Gakkai Wabun Ronbunshi, Vol.
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71