Report on “Radiation Disaster Recovery Studies”

Course: Radioactivity Environmental Protection Course
Name: Yasushi Nabae

I. Regarding “Radiation Disaster Recovery Studies”
In the Phoenix Leading Program, I learned radiation disaster medical treatment, environmental radiation
measurement and risk communication in addition to specialized research. These subjects are essential knowledge
and skills as experts in radiation disasters. I made use of the knowledge and examined the present situation, issues,and possible future issues, the policy of reconstruction after the Great East Japan Earthquake.

1) Reconstruction situation and its issues
I visited and interviewed the Reconstruction Agency in order to know the progress and issues of reconstruction. Mr.
Tamura, assistant counselor, responded to my interview. He is in charge of subsidies. The subsidy is a budget to be
distributed from the Reconstruction Agency to prefecture governments. The amount of the subsidy and the progressof reconstruction are closely linked, which is the reason why I interviewed him.
The reconstruction of the Great East Japan Earthquake is being advanced mainly by prefecture governments.
Based on the Great East Japan Earthquake Disaster Reconstruction Basic Law, the Reconstruction Agency has
1)created a 5-basic policy . “1. Support for Evacuees” is physical and mental care, support for reconstruction of life.
“2. Housing Reconstruction & Community Development”
is rebuilding of houses, reconstruction of medical care andnursing care, infrastructure improvement. “3. Reviving
Industry & Livelihoods” is regeneration of industries andoccupations, promotion of tourism, restoration of sales
route of marine processed goods, and reconstruction ofagriculture.

“4.

Revitalizing

andReconstructing

Fukushima” is decommissioning of nuclear reactor,
removalofradioactive

materials,

termination ofevacuation instructions and return. “5. Creation of a new
Tohoku” is the spread and development of people, knowhow owned by companies, universities, NPOs and privatecompanies in affected areas.

Fig. 1 Results of Surveys of Marine Fishery Products
in Fukushima Prefecture.
<Reconstruction Agency, Eliminating Negative Reputation Impact,
pp11-12, April, 2017>

"1.

Supportfor

Evacuees","2.

Housing

Reconstruction & Community Development" and “5.
Creation of a new Tohoku” are carried out as planned.
In April 2011, the number of temporary housing
residences was a maximum of approximately 124,000
units,

butinDecember

2016

itdecreasedtoapproximately 45,000 units, the relocation to permanent
housing is steadily advanced. However, “3. Reviving
Industry & Livelihoods” is not sufficiently advanced.
The Great East Japan Earthquake had a huge impact on
the fishery. The accumulation of rubble in the fishingground, the loss of the fishing boat, the collapse of theTable 1 Economic situation of Miyake Island<Toshiaki Sakuma, http://miyake-furusato.net/files/uploads/.pdf Access 17 Jun 2017>(a) Population change by census
Number1995
0-19 age836
20-59 age
1,878
60-74 age990
75 age over
350

2005
484
1,294
822
589

2016
271
1,111
654
583

(b) Change in tourists
Year
Tourist1999
79,2502015
36,0001986
78,701(c) Changes in farm products and marin products
thousand Yen
1998
2011
Farm Products
Marin Products

343,005
304,960

2013

218,000
172,005

256,733
152,358

fishing port and the collapse of the marine processing
facility occurred. Restoration and reconstruction have been strongly advanced in the fishery industry, and rubble offishing grounds has been removed. More than 90% of fishing boats are restored. 98% of the fishing port became
usable. 91% of marine processing facilities have been resumed. However, the sales of marine products are only
30% compared with the situation before Fukushima accident.
2)

Fig.1 shows the results of survey of marine products in Fukushima prefecture . The green line in the Fig.1
shows Excess ratio = (the number of samples exceeding the standard limit (100Bq/kg)) / (the total number ofsamples). From April to June, 2011 soon after the disaster, the percentage of excess ratio was 57.1 %. This
percentage has continued to decline, and has fallen to 0 % since April, 2015. Seafood exceeding the standard value
has not been detected for about two years, but Fukushima prefecture has continued the trial operation yet. The
reason is due to the reputation impact. I think that the 30% reduction of the sales of marine products in the all areaof Tohoku is due to the reputation impact.
After the earthquake, the supply of marine products from the Tohoku region decreased, therefore the area ofsupplier for marine products changed from the Tohoku region to other regions. In addition, sales of marine productsin the Tohoku region decreased due to the reputation impact. To restore sales, it is necessary to stop polluted waterfrom Fukushima Daiichi Nuclear Power Plant (FDNPP) by "4. Reconstruction and revitalization of Fukushima". I
think that the preconception must be gone away from theJapanfeeling of citizens.
4)

Tohoku . A recovery trend is observed. However, the trend
is smaller compared with Japan (232.5%). According to the

Ratio to 2010

Fig.2 shows the number of foreign tourists in Japan andanalysis by the Reconstruction Agency, there is a reputation
Tohokuimpact at abroad, and its impact is still present.
In order to analyze the progress of reconstruction, I

2010

2011

2012

2013

2014

2015

attempted to classify each application into hardware andFig.2 Number of foreign guests for sightseeing.

software categories. Hardware category includes rubble< Reconstruction Agency, Reconstruction situation and efforts fromthe Great East Japan Earthquake, pp8-9, January 2017 >treatment, rebuilding of houses, reconstruction of medical care and nursing care, infrastructure improvement.
Software category includes return of residents, development of sales channels, restoration of tourism, improvementof reputation impact. Commitments of the hardware are construction and civil engineering, and the contracts are
signed to progress as planned. Commitments of the software are related to the awareness of citizens, therefore
reconstructions often do not progress as planned. In the future, many budgets should be used for reconstruction ofsoftware. I think that the most important thing is the heart of the reconstruction.

2) Precedent case
The Fukushima accident was the greatest disaster in Japan. Although the scale of accident is different, I will
introduce the precedent case that will be helpful for future issues. It is a volcanic eruption in Miyake Island in 2000.
In this case, long-term evacuation and impact by ejection are similar to Fukushima accident. Miyake Island is about
200 km far from Tokyo. Islanders are around 2,000 people. Miyake Island erupted in 2000, and all islanders were
evacuated from the island. The evacuation periods became more than four years. In 2005, the evacuation order wascanceled and the islanders were able to return to Miyake Island. However, some issues occurred. Table 1 shows the5)changes in the economic situation of Miyake Island . 20 % of islanders did not return, they settled down in an
evacuation place. Tourists were anxious about the influence of volcanic gases, and the number decreased. The
farmer decreased, and the farm products decreased, too. The victim was evacuated for a long term. The influenceon health with the volcanic gases is worried. There is still a no-entry area.

3) Future issue in the Great East Japan Earthquake Disaster
Miyake Island is much smaller than Fukushima. However, Miyake Island eruption is an important precedent casebecause there are many similarities with the Fukushima accident. The future problem of the Great East Japan
Earthquake may already have occurred in Miyake Island. I think that the following things will be an issue in thedisaster area of the East Japan great earthquake disaster. In Miyake Island, the population of 20 - 59 years old in2016 is 1,111 people, but this number includes about 40% of civil servants and their families. The reconstruction
plan of the Great East Japan Earthquake will end in 2020, the population of the Tohoku region will decrease greatly
at that time. Many families with children moved to areas outside the Tohoku region. In the future, the elderly will
move to their children’s house, the population will further decrease. When the reconstruction plan is over, thevictim will not be able to receive sufficient support. As a result, the number of people receiving welfare protection
will increase. From the present situation of Miyake island, we should learn the issue that will occur in the future at
Tohoku.

References
1) Reconstruction Agency, Reconstruction situation and efforts from the Great East Japan Earthquake, pp2-13,
January 2017.
2) Reconstruction Agency, Elimination Negative Reputation Impact, pp11-12, April 2017.
3) MLIT HP, https://wwwtb.mlit.go.jp/tohoku/chikoushin/18chikoushin/ks-chikoushin18-07.pdf, Access 17
Jun 2017.

4) Reconstruction Agency, Elimination Negative Reputation Impact, pp8-9, April 2017.
5) Toshiaki Sakuma, http://miyake-furusato.net/files/uploads/.pdf Access 17 Jun 2017.

II. Summary of Doctoral Thesis
Title: Studies on Migration Pathway from the Japan Sea to the Sea of Okhotsk of Radioactive Cesium Derived fromthe Fukushima Daiichi Nuclear Power Plant.

1) Introduction
In the reconstruction situation of the Great East Japan Earthquake, there are steady policies and delayed policies.
There is a possibility that a part of policies are delayed by the reputation impact. Equally, tourists had decreased
due to reputation impact in Miyake island's precedent case. Risk Communication is important to reduce thereputation impact. In addition it is important that the stakeholders share the correct information. Unfortunately,
consumers do not properly understand the radioactivity in the ocean. Sales of marine processed goods in Tohoku
have not been recovered by the reputation impact. This is the reason why I investigated the radioactivity of ocean toprovide the information to the stakeholders. Because the information in the Japan Sea and the Sea of Okhotsk isparticularly less, I selected the places as the research sea areas. I think that the migration pathway of radioactive
materials and the concentration of radioactive cesium in the seabed soil are useful as information to be shared bystakeholders and such study will contribute to the reduction of the reputation impact. I also believe that theinvestigation on the radioactivity in the environment will contribute to radiation protection.

2) Purpose of the study5) 6) 7)In the accident of FDNPP that occurred in 2011, a large amount ofradioactive materials was released into the environment. The radioactive
materials were migrated in the environment and were taken up in organisms,
causing external radiation exposure and internal radiation exposure. To
clarify the migration pathway is important for Phoenix leader education
program for Renaissance from Radiation Disaster, and radiochemistry can

Soya

Sep.2015
Ishikari Bay

SakataJul. 2015

Kamo

Aug. 2016

Cs specific to accident at nuclear power plant was detected from theFeb. 2015
Feb. 2016

Agano River offing
FDNPP

contribute.
134

Notsuke

NaoetsuAug. 2016seabed soil of Ishikari Bay at Hokkaido. Many measurements and research
have been reported on the diffusion situation and the migration pathway of

Fig.3 Sea areas of radioactive survey.

radioactive materials in the Tohoku region and the Pacific Ocean. However,I do not know the study on the radioactive material migration pathway in the Japan Sea and the Sea of Okhotsk.
Radioactive materials derived from FDNPP were not detected from farms in Hokkaido, so I could not to think that
it is via the atmosphere. Therefore, the purpose of this study is to clarify the migration pathway of FDNPP derived
radioactive materials from Fukushima to the Ishikari Bay and from the Ishikari Bay forth.

3) ExperimentTotal of 43 seabed soils were collected in the Sea areas of Fig.

120
St11
100

Ratio[%]

3 to clarify the migration pathway of radioactive cesium. The
seabed soil was dried and radioactivity was measured with a Ge

St12

80

St13
St17

60

semiconductor detector. Measurement time was from 80,000

St40
40

3

seconds to 600,000 seconds, and 100 or 2000 cm of seabed

20

soil was measured. Radioactive cesium may not be adsorbed

0

St44

Clay-Silt(< 75 µm)

Fine sand(75 - 250 µm)

Medium sand(250 - 850 µm)

Coarse sand(850 - 2000 µm)

depending on the type of seabed soil even if it moves in the sea.
Fig.4 Grain size distribution of seabed soilin which 134Cs was detected.

Therefore, the grain size distribution of seabed soil wasinvestigated. Sieves were used for grain size analysis and theseabed soil was classified into Coarse sand, Medium sand, Fine sand and Clay - Silt, and the ratio was measured.
To clarify that radioactive cesium is migrating and diffusing by ocean current, a simulation was performed for theconcentration of134

Cs in the seabed soil using the advection diffusion equation.

4) Results and discussion

where

134

Cs was detected. Fig. 4 shows the results of classificationof seabed soil in which
134

Concentration[Bq/kg]

In seabed soils other than Naoetsu offing, there were seabed soils
134

Cs was detected. In the seabed soil whereCs was detected, it is found that the ratio of Clay-Silt and Finesand is high. However, in seabed soil where134

Cs was not detected,

it is found that Clay - Silt, Fine sand ratio was low. On the other
hand,

134

Cs was not detected even at the point where Clay - Silt ratio

10

4
2
R² = 0.81557

0137

Cs. The concentration ofconcentration of

134

137

10

20
30
Clay-Silt[%]

40

Fig.5 Relationship between Clay-Silt ratio
and 134Cs, 137Cs concentration in thesoils at Sakata and Kamo.

offing and Kamo offing close to the distance and the concentrations
Cs andR² = 0.85346

0Fig. 5 shows the relation between the ratio of Clay-Silt in Sakata
134

134Cs

6

was high at the Naoetsu offing.

of

137Cs

8

Cs is higher than theCs because of global fallout. There was a high correlation between the concentration of

Clay-Silt having the smallest grain size and the concentration of radioactive cesium. In general, radioactive cesium
is easily adsorbed to Clay-Silt. Therefore, it is suggested that Clay-Silt of seabed soil also adsorbs more radioactive
cesium.
Fig. 6 shows the relationship between the values of1000

Cs concentration is the highest

Cs concentration

decreased, and a phenomenon similar to advection /diffusion was observed. However, because134

Cs was not101

detected from the seabed soil of Naoetsu offing and the

0.1

Tsushima warm current flows to east at the Naoetsu

0.01

offing, the source of the outflow in the Japan Sea was

Notsuke Strait

134

Soya Strait

the migration distance increased, the100

134Cs(simulation
360STEP)134Cs(measured value)
系列1

Ishikari Bay

and the migration distance in the sampling sea areas. As

134Cs [Bq/kg]

134

Sakata Offing
Kamo Offing
Agano River Mouth

the points where the

Naoetsu offing ND(<0.09)
The concentration was corrected at March 11, 2011.
-200

0
200 400
600 800 1000 1200 1400
Migration Distance from Agano River mouth [km]Fig.6

134Cs concentration

vs migration distance.

limited to the area east than Naoetsu. Simulation was calculated on the134

Cs concentration in the seabed soil. Fig.6

shows measured values and simulation values, and similar decreasing trends were observed in these values.
Because the simulation is calculated by ocean current, it was suggested that the water mass including

134

C migrated

by ocean current. Measurement values are lower than the simulation values in the Soya Strait and the Notsuke Strait.
I think that the reason is that Tsushima warm current is divided, a part of it becomes Soya warm current, theOkhotsk surface low salinity water etc. mix.

5) Conclusion
A part of the radioactive cesium derived from Fukushima Daiichi Nuclear Power Plant flowed out into the Japan
Sea from the region east than Naoetsu, and migrated to Notsuke Strait by the Tsushima warm current and the Soyawarm current.

References
5) Nabae, Y., Miyashita, S., Nakashima, S.: Observation of radiocesium in seabed soil at the Notsuke Strait of
the southern Sea of Okhotsk derived from the Fukushima Daiichi Nuclear Power Plant, Radiation Safety
Management, 15, 9 - 15 (2016).
6) Nabae, Y., Miyashita, S., Nakashima, S.: Observation of radioactive cesium in seabed soil at the Soya Strait
derived from the Fukushima Daiichi Nuclear Power Plant, Radiation Safety Management, 16, 8-12 (2016).
7) Nabae, Y., Tsujimoto, M., Miyashita, S., Nakashima, S.: Distribution of radioactive cesium from the
Fukushima Daiichi Nuclear Power Plant in seabed soil from the Niigata Prefecture and Yamagata
Prefecture offings, in preparation.