August 21, 2012
Results of the Nuclide Analysis of Plutonium 238, 239+240
and 241 (Second Survey) by MEXT
The results of nuclide analysis of plutonium 238, 239+240 and 241 were compiled as follows, in
the course of the second survey on distribution of radioactive substances pertaining to the accident at
TEPCO’s Fukushima Dai-ichi Nuclear Power Station that had been conducted from December 6,
2011.
1. Objective of the survey
In the survey conducted in June 2011 (hereafter referred to as “first soil survey”) MEXT
collected soil samples at around 2,200 points(*1) within approximately 100km from the TEPCO’s
Fukushima Dai-ichi Nuclear Power Station (hereafter referred to as “Fukushima Dai-ichi NPS”),
and conducted nuclide analysis of plutonium 238 and 239+240(*2) for soil samples taken at 100
points within 80km from the Fukushima Dai-ichi NPS (see “Results of the Nuclide Analysis of
Plutonium and Strontium by MEXT” (announced on September 30, 2011) for details.)
As a result, the amounts of deposition of plutonium 238 and 239+240 for each of the survey
points were within the measurement value range that was measured around the country before the
occurrence of the accident at Fukushima Dai-ichi NPS. However, the effects of plutonium released
by the accident at Fukushima Dai-ichi NPS were detected in some of the samples. Therefore, an
additional survey was required to confirm the detailed distribution situation of the plutonium 238
and 239+240 that were released by the accident at Fukushima Dai-ichi NPS.
So in this survey (hereafter referred to as “second soil survey”) a new nuclide analysis was
conducted for soil samples that were collected from the areas within 80-100km from the
Fukushima Dai-ichi NPS that were not included as the survey target in the first soil survey in order
to grasp the detailed distribution situation of plutonium 238 and 239+240 (one of the representative
alpha-emitting nuclides), and a new nuclide analysis was conducted for soil samples that were
collected from the survey area where plutonium 238 and 239+240 were detected in the first soil
survey.
Moreover, Plutonium 241 was included for analysis in this survey in consideration of the fact
that the amount estimated to have been released in the estimated value for the amount of
radioactive materials that had been released from the Fukushima Dai-ichi NPS as announced by the
Nuclear and Industrial Safety Agency (NISA) (announced on October 20, 2011) was 63 times the
amount of Plutonium 238, although the conversion factor is smaller by a factor of 10 in comparison
with plutonium 238 and 239+240 for evaluation of exposure.
Furthermore, the measurement results for plutonium 238, 239+240 and 241 have been compiled
through verification of the validity of the results of the measurement, taking into account the
opinions of experts in the relevant field as with the first soil survey.
*1 In the first soil survey, one point was selected as the survey point from a 2×2km grid for
inhabitable land in the area within 80km from the Fukushima Dai-ichi NPS, and one
point was selected as the survey point from a 10×10km grid in the area within
80-100km from the Fukushima Dai-ichi NPS and in western Fukushima prefecture,
which was outside this range. Also, a U-8 container was used to collect soil samples
5cm from the surface at 5 locations of a 3×3m grid at each survey point.
*2 As the alpha-ray energy emitted from plutonium 239 and that emitted from 240 is almost
the same, these amounts cannot be distinguished through the regular analysis method
for alpha-ray emitting nuclides. Therefore, the analysis is conducted for the total of
these two nuclides.
2. Details of the survey
○Samples that were analyzed in this survey:
(i) Analysis of plutonium 238 and 239+240 (62 points: 62 samples)
Of the soil samples collected in the first soil survey (collection date: first period—June 6 to
June 14, second period—June 27 to July 8), the following soil samples where nuclide analysis
was not conducted were analyzed:
- Soil samples that were collected from areas within 80-100km from the Fukushima Dai-ichi
NPS.
- Soil samples that were collected from grids adjoining the grid where plutonium 238 and
239+240 that were thought to have originated from the accident at Fukushima Dai-ichi NPS
accident were detected in the first soil survey (54 samples).
(ii) Analysis of plutonium 241 (62 points: 62 samples)
Since plutonium 241 only releases low-energy beta-rays, it is difficult to lower the detection
limit, and accurate measurement for this is difficult.
Therefore, in this survey we have analyzed plutonium 241 mainly by reusing the samples
where plutonium 238 and 239+240 had been detected in the first soil survey. Through
obtaining the ratio of the deposition amount of plutonium 238, 239+240 and 241, it was
considered whether the deposition amount can be estimated for points where plutonium 241
was not analyzed based on this ratio. In view of this, after being analyzed for plutonium 238
and 239+240, the following samples (samples that had been measured for plutonium in the first
soil survey and samples that had been newly measured for plutonium in this survey) were
analyzed:
- Samples that had been analyzed for plutonium 238 and 239+240, where plutonium 238 and
239+240 were detected in the first soil survey (54 samples).
- Samples that had been analyzed for plutonium 238 and 239+240 for soil samples that had
been newly analyzed for plutonium 238 and 239+240 in this survey and collected from the
areas within 80-100km from the Fukushima Dai-ichi NPS (8 samples).
○Entity of conducting nuclide analysis: Japan Chemical Analysis Center
○Targets: The amounts of deposition on the ground surface per unit area of plutonium 238,
239+240 and 241 (Bq/m2)
○Survey method:
(i) Plutonium 238 and 239+240
Regarding plutonium 238 and 239+240, radiochemical analysis was conducted for 50g of each
of the collected soil samples, using silicon semiconductor detectors to measure alpha-rays. The
measurement was carried out for nearly 20 hours. The detection limit was set at around 0.5
Bq/m2 both for plutonium 238 and plutonium 239+240.
(ii) Plutonium 241
Regarding plutonium 241, through re-using the sample (electrodeposited plate) that was used
to measure the alpha-rays for plutonium 238 and 239+240, and after chemically separating it, a
liquid scintillation counter was used to measure the beta-rays for plutonium 241. The
measurement was carried out for nearly 500 minutes. The detection limit was set at around
50Bq/m2 for plutonium 241. (Note that in this survey, the detection limit may become higher
due to the fact that samples used to measure alpha-rays for plutonium 238 and 239+240 were
reused for analyzing plutonium 241.)
3. Results of the survey
○ The results of the nuclide analysis in this survey are shown in Attachments 1 and 2 (Attachment
1: nuclide analysis results for plutonium 238 and 239+240, Attachment 2: nuclide analysis
results for plutonium 241).
○ Also, in order to confirm the distribution of plutonium 238 and 239+240, Attachment 3 is the
soil concentration map which is added to the nuclide analysis results of the plutonium 238 and
239+240 conducted in the first and second soil survey and by Fukushima prefecture
*3 This map indicates the distribution of the radiation amount per unit area near the soil surface.
The description “soil concentration map” has been used for convenience to make it easier to
understand.
○ In preparing the soil concentration map, it was prepared under the following conditions:
(i) Regarding the measurement results of the first soil survey, land plots with certain free space
and free from disturbances were selected in the 2011 Strategic Funds for the Promotion of
Science and Technology, entitled “Establishment of the Base for Taking Measures for
Environmental Impact of Radioactive Substances — Study on Distribution of Radioactive
Substances” and the results of the nuclide analysis conducted on soil samples that were
collected by MEXT from between June 6 to July 8 were used.
(ii) Regarding the measurement results of the survey conducted by Fukushima prefecture,
bettering order to grasp of the change in the deposition amount of plutonium in the soil within
the prefecture both prior and after the occurrence of the accident at Fukushima Dai-ichi NPS.
Soil samples were collected at points where past survey results were available, and the
deposition amount could be compared (55 points) during the periods of June 13-14, 2011, and
August 10-October 13, 2011, and the results of the nuclide analysis (the deposition amount of
plutonium 238 and 239+240) that was conducted were used (see “Results of the Radiation
Monitoring of Soil in Fukushima Prefecture” (announced on April 6, 2012) for details).
(iii) Regarding the preparation of the soil concentration map, in order to grasp the details of the
deposition of plutonium 238 and 239+240, the results of the second soil survey and of the
survey conducted by Fukushima prefecture were adjusted in consideration of the half-life
period (plutonium 238: 87.7 years, plutonium 239: 2.411×104 years, plutonium 240: 6564
years) as of June 14, 2011—the base date for the first survey’s soil concentration map for
plutonium 238 and 239+240—and were included in the map.
4. Consideration
4.1 Overall consideration
○From the results of the first soil survey and for this soil survey, although there were limits in the
number of points surveyed, we were able to confirm the overall distribution of plutonium 238
and 239+240 in the areas within 100km from the Fukushima Dai-ichi NPS.
○For the point where the largest deposition amounts of plutonium 238 and 239+240 were detected
in this survey, we calculated possible inhalation exposure caused by resuspension from the soil
and accumulated external exposure from the soil supposing that a person stays there for 50 years
(hereinafter referred to as the “accumulated effective dose over 50 years”), based on the Generic
Assessment Procedures for Determining Protective Actions During a Reactor Accident proposed
by IAEA.*4 As a result, it was confirmed that the accumulated effective doses over 50 years for
these points were considerably smaller than the doses at the locations where the largest
deposition amounts of cesium 134 or 137 were detected. This result was the same as that of the
first soil survey.
*4: Method to assess exposure levels described in IAEA-TECDOC-955, 1162
Presuming that a radioactive nuclide deposited on the ground stays on that spot, this
method defines the procedures to assess accumulated effective doses for a certain
period of time after the nuclide is deposited on the ground surface (for the first month,
for the second month, and for 50 years). The effective doses thus obtained include
external exposure doses and committed doses caused by the inhalation of resuspended
radioactive nuclides. In the calculation of accumulated effective doses, consideration
was given to the effects of radionuclide decay, nuclear transmutation, and weathering.
Furthermore, in order to assess inhalation exposure caused by resuspended radioactive
nuclides on the safer side, 10-6/m was adopted as the resuspension factor, which is
larger than the value actually measured at the time of the nuclear accident.
(Reference 1)
Accumulated effective doses over 50 years at points where the largest deposition amounts of
plutonium 238 and 239+240 were detected in this survey
(i) Plutonium 238 (11 Bq/m2):
0.071mSv
(The estimated effective dose over 50 years for the highest value (4.0 Bq/m2) in the first
soil survey: 0.027mSv)
(ii) Plutonium 239+240 (19 Bq/m2): 0.16mSv
(The estimated effective dose over 50 years for the highest value (15 Bq/m2) in the first
soil survey: 0.12mSv)
(iii) Plutonium 241 (150 Bq/m2):
0.029mSv
(Reference 2)
Accumulated effective doses over 50 years at points where the largest deposition amounts of
cesium 134 and 137 were detected in this survey
(v) Cesium 134 (1.4×107Bq/m2): 71mSv
(vi) Cesium 137 (1.5×107Bq/m2): 2.0Sv (2,000mSv)
○Compared with the accumulated effective doses over 50 years of cesium 134 and 137, those of
plutonium 238, 239+240 and 241 were very small, which was the same as with the first soil
survey. Therefore, when assessing exposure doses or implementing decontamination measures in
the future, we should continue on as before while focusing attention on deposition amounts of
cesium 134 and 137.
4.2 Consideration of the results of plutonium 238 and plutonium 239+240 measurement
○In the first soil survey, the ratio of deposition amounts of plutonium 238 (half-life: 87.7 years)
against those of plutonium 239+240 (plutonium 239 half-life: 2.41×104 years; plutonium 240
half-life: 6,564 years) that were monitored in a nationwide survey from FY1999 to FY2009 was
around 0.031 (national average). However, the ratios were around 0.33 to 2.2 at five points
where plutonium 238 and plutonium 239+240 were both detected in the first soil survey. These
higher ratios observed after the accident suggest that plutonium were newly deposited at these
five points due to the accident.
At one point where plutonium 239+240 were not detectable but plutonium 238 was detected in
the first soil survey, the deposition amount of plutonium 238 (0.57Bq/m2) was larger than the
detection limit for plutonium 239+240 (around 0.5Bq/m2), which suggests that plutonium was
newly deposited by the accident at Fukushima Dai-ichi NPS.
○On the other hand, with regard to this survey’s results, we calculated the ratios of deposition
amounts of plutonium 238 against those of plutonium 239+240. The calculation results were
0.030 to 2.5, and in several places we confirmed points where ratios of deposition amounts of
plutonium 238 against those of plutonium 239+240 were larger than the ratio that was measured
in the nation-wide survey before the accident from FY1999 to FY2009 (Average value: 0.031,
Minimum value: 0.012, Maximum value: 0.120).
○Therefore, for this survey result, in order to confirm that plutonium 238 and plutonium 239+240
had been newly deposited with the accident at Fukushima Dai-ichi NPS, we have assumed the
ratios of deposition amounts of plutonium 238 against those of plutonium 239+240 that were
measured in a nationwide survey from FY1999 to FY2009 (hereafter “Pu-238/Pu-239+240
before the accident”) as forming a lognormal distribution, and judged the spots (10 spots) where
the ratio deviated from the Pu238/Pu239+240 before the accident as suggesting a possibility that
plutonium 238 and plutonium 239+240 had been newly deposited with the accident at
Fukushima Dai-ichi NPS (see Attachment 4 for details).
○The deposition amounts of plutonium 238 and plutonium 239+240 had been confirmed in this
survey, and all spots—except for the value of deposition amount of plutonium 238 that was
detected at one spot—have been within the level of the range of the measurement value for
plutonium 238 and plutonium 239+240 that had been measured in the nation-wide survey from
FY1999 to FY2009 before the accident (range for the effects caused by past atmospheric nuclear
tests*6). Moreover, the deposition amount of plutonium 238 at the one spot in this survey where it
exceeded the maximum value for the deposition amount of plutonium 238 measured before the
accident was about 1.4 times the maximum value for the deposition amount of plutonium 238
measured before the accident.
*6: plutonium 238: detection limit – 8.0Bq/ m2 (average value: 1.0Bq/m2), plutonium
239+240: detection limit – 220Bq/m2 (average value: 16Bq/m2)
4.3 Consideration of the results of plutonium 241
○ For this survey:
- The samples used to measure plutonium 238 and 239+240 were re-used to analyze
plutonium 241.
- The amount of soil samples (50g) that were used to measure plutonium 238 and 239+240
was too small for detecting plutonium 241 in a significant way.
Due to this, the detection limit for plutonium 241 failed to come down, and only 3 samples
contained plutonium 241 measured above the detection limit.
○ Due to this, we were unable to confirm precisely the rate of deposition of plutonium 238,
239+240 and 241, which were the objects of this investigation.
○ Moreover, of the soil samples (6 samples) where plutonium 238 or plutonium 238 and 239+240
were detected in the first soil survey, plutonium 241 was detected in 3 samples. However, these
samples all had the same estimated value trend for the released amount ratio for plutonium 238,
239+240 and 241 (the estimated value for the released amount of plutonium 241 by NISA is
larger than that for plutonium 238 and 239+240 by a factor of 10.) Thus, it was confirmed that
the deposition amount ratio for plutonium 241 is greater than that for plutonium 238 and
239+240.
(Reference 3)
Ratios between plutonium 241 and plutonium 238 and 239+240, which had been deposited in
the soil (3 samples)
- Amount of plutonium 241 deposited / amount of plutonium 238 deposited: 38-76 (Average:
57)
- Amount of plutonium 241 deposited / amount of plutonium 239+240 deposited: 71-85
(Average: 78)
(Reference 4)
Ratios between plutonium 241 and plutonium 238 and 239+240 that had been deposited in the
soil (3 samples)
- Estimated value for the released amount of plutonium 241 deposited / Estimated released
amount of plutonium 238: 63
- Estimated value for the released amount of plutonium 241 deposited / Estimated released
amount of plutonium 239+240: 188
5. Future plans
○ From the first soil survey and in this survey, we have been able to confirm the distribution of
plutonium 238 and 239+240 in the north-western direction from the Fukushima Dai-ichi NPS. In
order to elaborate the soil concentration map of plutonium 238 and 239+240, we are planning to
collect new samples from centering on areas around survey points where plutonium 238 and
239+240 that are thought to have been derived from the accident have been detected, and where
a high deposition amount of cesium 137, etc. has been found, and to conduct nuclide analysis of
these in the survey for FY2012.
○ Also in the survey for FY2012, in order to continue obtaining the deposition ratio of plutonium
238, 239+240 and 241, we will collect from the areas around the points where plutonium 238
and 239+240 had been detected in the first soil survey and for this survey roughly 100g of new
soil samples, which is double the amount (50g) that was used in this survey, and to conduct
nuclide analysis on this.
＜Contact point＞
Emergency Operation Center, MEXT
Kato （Extension 4604、4605）
TEL：03−5253−4111（Representative）
Nuclide Analysis Results of Pu- 238 and Pu-(239+240)（Second Soil Survey）
№
Prefecture
Address of
Sampling Point
Fukushima
Aizu
Wakamatsu
City
Latitude
Longitude
2
2
Pu-238(Bq/m )
Pu-239+240(Bq/m )
Not Detectable
Not Detectable
(Lower detection limit：1.4)
(Lower detection limit：1.4)
1.0
Pu-238/Pu(239+240)
Attachment 1
Estimated effective dose over 50 years using
the conversion factor of IAEA-TEC-DOC1162 (mSv)
Pu-238
Pu-(239+240)
ー
ー
ー
6.6
0.16
6.9E-03
5.6E-02
16
ー
ー
1.3E-01
0.81
ー
ー
6.9E-03
37.467139
140.011417
2
37.603028
140.785278
3
37.607583
140.766556
4
37.609750
140.731111
5
37.625389
140.810528
0.81
12
0.067
5.4E-03
1.0E-01
6
37.628806
140.773111
0.69
2.0
0.35
4.5E-03
1.7E-02
7
37.644583
140.808778
0.23
4.8E-03
2.7E-02
ー
ー
ー
7.4
ー
ー
6.3E-02
0.62
ー
ー
5.3E-03
ー
ー
ー
ー
ー
1.3E-02
ー
ー
ー
ー
ー
ー
ー
ー
9.4E-03
ー
ー
ー
ー
ー
2.5E-02
ー
ー
ー
7.5
ー
ー
6.4E-02
1.6
0.28
2.9E-03
1.3E-02
1.6
ー
ー
1.4E-02
ー
ー
ー
ー
ー
4.5E-03
ー
ー
ー
ー
ー
3.0E-03
ー
ー
ー
1.6
ー
ー
1.4E-02
0.98
ー
ー
8.3E-03
1.4
ー
ー
1.2E-02
ー
ー
ー
ー
ー
ー
1
8
Fukushima
Iitate
Village
9
37.664222
37.690611
10
37.704250
140.732806
140.733944
140.713139
11
37.715694
140.694722
12
37.720194
140.720972
13
37.746778
140.713889
14
37.735528
140.697833
15
37.255472
140.711583
37.126667
140.843778
17
37.086111
140.962778
18
37.048306
140.792806
19
37.414611
140.944611
20
37.389833
140.957083
37.396806
140.999056
22
37.409667
140.997111
23
37.411694
141.005806
37.351611
140.892583
37.307806
140.823028
16
Fukushima
21
Fukushima
Iwaki City
Okuma
Town
24
Fukushima
Kawauchi
Village
25
26
Fukushima
Koriyama
City
37.343694
140.330111
27
Fukushima
Shimogou
Town
37.303278
139.930806
28
Fukushima
Soma
City
37.796167
140.914639
37.724000
140.662417
37.744139
140.656972
37.710561
140.650105
29
30
31
Fukushima
Date City
Not Detectable
(Lower detection limit：0.87)
Not Detectable
(Lower detection limit：0.77)
0.73
3.2
Not Detectable
Not Detectable
(Lower detection limit：1.3)
(Lower detection limit：1.3)
Not Detectable
(Lower detection limit：0.64)
Not Detectable
(Lower detection limit：0.61)
Not Detectable
Not Detectable
(Lower detection limit：0.72)
(Lower detection limit：0.72)
Not Detectable
(Lower detection limit：0.59)
1.6
Not Detectable
Not Detectable
(Lower detection limit：1.5)
(Lower detection limit：0.73)
Not Detectable
Not Detectable
(Lower detection limit：1.4)
(Lower detection limit：1.4)
Not Detectable
(Lower detection limit：0.70)
1.1
Not Detectable
Not Detectable
(Lower detection limit：0.62)
(Lower detection limit：0.55)
Not Detectable
(Lower detection limit：1.5)
3.0
Not Detectable
Not Detectable
(Lower detection limit：0.41)
(Lower detection limit：0.41)
Not Detectable
(Lower detection limit：0.97)
0.44
Not Detectable
(Lower detection limit：1.5)
Not Detectable
Not Detectable
(Lower detection limit：1.2)
(Lower detection limit：1.2)
Not Detectable
(Lower detection limit：1.1)
0.52
Not Detectable
Not Detectable
(Lower detection limit：1.2)
(Lower detection limit：1.2)
Not Detectable
(Lower detection limit：0.33)
0.35
Not Detectable
Not Detectable
(Lower detection limit：1.4)
(Lower detection limit：1.4)
Not Detectable
(Lower detection limit：0.74)
Not Detectable
(Lower detection limit：1.6)
Not Detectable
(Lower detection limit：0.86)
Not Detectable
Not Detectable
(Lower detection limit：0.53)
(Lower detection limit：0.53)
Not Detectable
Not Detectable
(Lower detection limit：0.62)
(Lower detection limit：0.62)
Nuclide Analysis Results of Pu- 238 and Pu-(239+240)（Second Soil Survey）
№
Prefecture
Address of
Sampling Point
Latitude
Longitude
32
Fukushima
Tamura City
37.458139
140.718333
33
Fukushima
Tomioka
Town
37.372306
140.990667
34
37.542806
140.815583
35
37.537765
140.780232
36
37.556833
140.789722
37
37.566826
140.802109
38
37.579306
140.774472
39
37.569333
Fukushima
Namie Town
140.738972
37.596806
140.738222
41
37.465778
140.906417
42
37.470556
140.933111
43
37.476972
140.983583
44
37.485028
140.942972
45
37.489556
140.963306
46
37.476833
141.007472
40
2
Pu-238(Bq/m )
Not Detectable
(Lower detection limit：1.2)
2
Pu-239+240(Bq/m )
10
Not Detectable
Not Detectable
(Lower detection limit：1.6)
(Lower detection limit：1.6)
Not Detectable
Not Detectable
(Lower detection limit：1.6)
(Lower detection limit：1.6)
0.39
13
Pu-238/Pu(239+240)
Attachment 1
Estimated effective dose over 50 years using
the conversion factor of IAEA-TEC-DOC1162 (mSv)
Pu-238
Pu-(239+240)
ー
ー
8.5E-02
ー
ー
ー
ー
ー
ー
0.030
2.6E-03
1.1E-01
ー
ー
ー
Not Detectable
Not Detectable
(Lower detection limit：0.65)
(Lower detection limit：0.65)
3.9
1.8
2.2
2.6E-02
1.5E-02
1.1
6.0
0.18
7.2E-03
5.1E-02
2.0
ー
ー
1.7E-02
13
ー
ー
1.1E-01
2.6
ー
ー
2.2E-02
4.3
2.5
7.1E-02
3.6E-02
ー
ー
ー
3.0
ー
ー
2.6E-02
8.8
ー
ー
7.5E-02
0.52
ー
ー
4.5E-03
ー
ー
ー
16
ー
ー
1.4E-01
0.56
ー
ー
4.8E-03
3.3
ー
ー
2.8E-02
3.9
ー
ー
3.4E-02
Not Detectable
(Lower detection limit：1.3)
Not Detectable
(Lower detection limit：0.89)
Not Detectable
(Lower detection limit：0.62)
11
Not Detectable
Not Detectable
(Lower detection limit：0.62)
(Lower detection limit：0.62)
Not Detectable
(Lower detection limit：1.2)
Not Detectable
(Lower detection limit：0.59)
Not Detectable
(Lower detection limit：0.57)
Not Detectable
Not Detectable
(Lower detection limit：0.36)
(Lower detection limit：0.36)
47
Fukushima
Naraha
Town
37.297361
140.974333
48
Fukushima
Hanawa
Town
36.906033
140.365857
37.447444
141.009000
37.454111
140.981167
51
37.432167
140.989222
52
37.665556
140.893167
0.79
6.4
0.12
5.2E-03
5.4E-02
37.666028
140.869667
0.64
3.0
0.21
4.2E-03
2.6E-02
37.632139
140.948861
ー
ー
ー
37.632861
140.855028
49
50
Fukushima
53
Fukushima
54
Futaba
Town
Minami
Soma
City
55
56
Fukushima
Yabuki
Town
37.155750
140.329972
57
Miyagi
Kawaseki
Town
38.206412
140.582149
58
Miyagi
Shiraishi
City
37.924333
140.599361
59
Miyagi
Sendai
City
38.213333
140.866278
60
Miyagi
Shichikakusyu
Town
38.018030
140.369096
61
Ibaraki
Hitachi City
36.678556
140.623111
62
Tochigi
Nasu Town
37.043333
140.088056
Not Detectable
(Lower detection limit：1.4)
Not Detectable
(Lower detection limit：0.92)
Not Detectable
(Lower detection limit：0.78)
Not Detectable
(Lower detection limit：1.6)
Not Detectable
Not Detectable
(Lower detection limit：1.3)
(Lower detection limit：1.3)
0.89
19
0.047
5.9E-03
1.6E-01
2.9
ー
ー
2.4E-02
ー
ー
ー
ー
ー
2.2E-02
ー
ー
ー
ー
ー
3.0E-02
ー
ー
ー
ー
ー
8.0E-03
Not Detectable
(Lower detection limit：1.3)
Not Detectable
Not Detectable
(Lower detection limit：0.59)
(Lower detection limit：0.59)
Not Detectable
(Lower detection limit：0.99)
2.6
Not Detectable
Not Detectable
(Lower detection limit：1.5)
(Lower detection limit：1.5)
Not Detectable
(Lower detection limit：0.73)
3.5
Not Detectable
Not Detectable
(Lower detection limit：1.1)
(Lower detection limit：1.1)
Not Detectable
(Lower detection limit：1.3)
0.94
Nuclide Analysis Results of Plutonium 241 （Second Soil Survey）
No.
1
Prefecture
Address of
Sampling Point
Fukushima
Aizu
Wakamatsu
City
2
Fukushima
3
Fukushima
4
Fukushima
5
Fukushima
6
Fukushima
7
Fukushima
8
Fukushima
9
Fukushima
Iitate
Village
Inawashiro
Town
Okuma
Town
Ootama
Village
Katsurao
Village
Latitude
Longitude
37.467139
37.628806
140.773111
37.664028
140.721028
37.690611
140.733944
37.722528
140.688139
37.612056
140.139139
37.414556
140.912639
37.408972
140.959083
37.396806
140.999056
37.538139
140.368750
37.537222
140.701444
37.369583
140.736250
37.331111
140.884028
37.276972
140.809722
37.631861
140.633750
37.662639
140.608444
11
Fukushima
12
Fukushima
13
Fukushima
14
Fukushima
15
Fukushima
16
Fukushima
17
Fukushima
Kori Town
37.858639
140.506028
18
Fukushima
Samegawa Village
37.042111
140.506972
19
Fukushima
Shimogou Town
37.303278
139.930806
20
Fukushima
Sirakawa City
37.146472
140.243750
21
Fukushima
Soma City
37.796167
140.914639
22
Fukushima
Tanakura Town
36.989667
140.278083
23
Fukushima
37.458139
140.718333
24
Fukushima
37.460000
140.638333
25
Fukushima
37.424972
140.817028
26
Fukushima
37.358889
140.935111
27
Fukushima
28
Fukushima
29
Fukushima
30
Fukushima
31
Fukushima
Tamura City
Tomioka Town
Nakajima Village
37.359278
141.009972
37.337528
141.015750
37.146111
140.356389
37.560528
140.823806
37.596056
140.754111
Namie Town
32
Fukushima
37.520778
140.852694
33
Fukushima
37.489556
140.963306
34
Fukushima
37.310500
140.968722
35
Fukushima
37.298250
140.990778
36
Fukushima
37.258444
140.997583
37
Fukushima
36.956528
140.440000
36.906033
140.365857
37.242889
140.569639
Naraha Town
Hanawa Town
38
Fukushima
39
Fukushima
Hirata Village
(Reference) The deposition amount of Pu-238, Pu-239/240
for each sample (Bq/m2)
Pu-238
Pu-(239 ＋240)
Not Detectable
Not Detectable
(Lower detection limit：65)
(Lower detection limit：1.4)
(Lower detection limit：1.4)
Not Detectable
Not Detectable
0.88
ー
140.011417
Fukushima
Kawamata
Town
Estimated effective dose over 50
years for Pu-241 using the
conversion factor of IAEA-TECDOC-1162 (mSv)
Not Detectable
10
Kawauchi
Village
Deposition amount of
Pu -241(Bq/m2)
Attachment 2
(Lower detection limit：28)
Not Detectable
(Lower detection limit：110)
Not Detectable
(Lower detection limit：120)
Not Detectable
(Lower detection limit：57)
Not Detectable
(Lower detection limit：98)
Not Detectable
(Lower detection limit：170)
Not Detectable
(Lower detection limit：94)
Not Detectable
(Lower detection limit：140)
Not Detectable
(Lower detection limit：130)
Not Detectable
(Lower detection limit：67)
Not Detectable
(Lower detection limit：89)
Not Detectable
(Lower detection limit：59)
Not Detectable
(Lower detection limit：72)
Not Detectable
(Lower detection limit：80)
Not Detectable
(Lower detection limit：46)
Not Detectable
(Lower detection limit：110)
Not Detectable
(Lower detection limit：100)
Not Detectable
(Lower detection limit：44)
Not Detectable
(Lower detection limit：130)
Not Detectable
(Lower detection limit：43)
Not Detectable
(Lower detection limit：29)
Not Detectable
(Lower detection limit：120)
Not Detectable
(Lower detection limit：37)
Not Detectable
(Lower detection limit：89)
Not Detectable
(Lower detection limit：33)
Not Detectable
(Lower detection limit：34)
Not Detectable
(Lower detection limit：45)
Not Detectable
(Lower detection limit：38)
ー
ー
0.77
0.60
ー
Not Detectable
(Lower detection limit：1.3)
0.82
7.6
Not Detectable
(Lower detection limit：0.98)
Not Detectable
(Lower detection limit：1.4)
Not Detectable
(Lower detection limit：0.47)
Not Detectable
(Lower detection limit：1.4)
Not Detectable
(Lower detection limit：1.3)
Not Detectable
(Lower detection limit：0.68)
Not Detectable
(Lower detection limit：0.22)
Not Detectable
(Lower detection limit：1.3)
Not Detectable
(Lower detection limit：0.75)
Not Detectable
(Lower detection limit：0.40)
Not Detectable
(Lower detection limit：0.92)
Not Detectable
(Lower detection limit：1.1)
Not Detectable
(Lower detection limit：1.0)
Not Detectable
(Lower detection limit：0.74)
Not Detectable
(Lower detection limit：0.91)
Not Detectable
(Lower detection limit：0.64)
Not Detectable
(Lower detection limit：0.88)
Not Detectable
(Lower detection limit：0.61)
Not Detectable
(Lower detection limit：1.1)
Not Detectable
(Lower detection limit：0.89)
Not Detectable
(Lower detection limit：0.47)
Not Detectable
(Lower detection limit：1.1)
Not Detectable
(Lower detection limit：1.5)
Not Detectable
(Lower detection limit：0.57)
2.3
2.9
ー
ー
ー
ー
ー
ー
ー
ー
ー
ー
ー
ー
ー
ー
ー
ー
ー
ー
ー
ー
ー
ー
ー
ー
ー
130
2.5E-02
150
2.9E-02
Not Detectable
(Lower detection limit：87)
Not Detectable
(Lower detection limit：35)
Not Detectable
(Lower detection limit：74)
Not Detectable
(Lower detection limit：97)
Not Detectable
(Lower detection limit：76)
Not Detectable
(Lower detection limit：39)
Not Detectable
(Lower detection limit：140)
Not Detectable
(Lower detection limit：29)
(Lower detection limit：0.44)
ー
ー
ー
ー
ー
ー
ー
ー
2.5
1.7
3.1
1.7
1.9
1.3
1.7
1.4
1.6
1.5
3.8
2.2
1.5
1.6
6.4
0.71
0.54
11
0.63
1.8
7.0
0.80
0.83
0.69
1.8
4.0
1.8
Not Detectable
(Lower detection limit：0.44)
Not Detectable
(Lower detection limit：1.0)
Not Detectable
(Lower detection limit：0.74)
Not Detectable
(Lower detection limit：0.97)
Not Detectable
(Lower detection limit：0.76)
Not Detectable
(Lower detection limit：0.49)
Not Detectable
(Lower detection limit：1.4)
Not Detectable
(Lower detection limit：0.82)
3.1
6.5
1.7
4.0
1.5
0.48
16
0.82
Nuclide Analysis Results of Plutonium 241 （Second Soil Survey）
No.
Prefecture
40
Fukushima
41
Fukushima
42
Fukushima
43
Fukushima
44
Fukushima
45
Fukushima
46
Fukushima
47
Fukushima
Address of
Sampling Point
Hirono Town
Fukushima City
Futaba Town
48
Fukushima
Minami
Soma
City
49
Fukushima
Miharu Town
Latitude
Longitude
37.239222
140.911722
37.203722
140.989806
37.214056
140.941639
37.781944
140.490361
37.436194
140.995917
37.461306
141.009861
37.426083
140.973861
37.560111
140.927806
37.665556
140.893167
37.425694
140.486306
50
Fukushima
Motomiya City
37.522861
140.411583
51
Miyagi
Iwanuma City
38.106972
140.876861
52
Miyagi
Kawaseki
Town
38.206412
140.582149
53
Miyagi
Shiroishi City
37.924333
140.599361
54
Miyagi
Sendai City
Miyagi
Shichikakusyu
Town
55
56
38.213330
140.866278
38.004861
140.462444
38.041822
140.298463
57
Miyagi
Murata
Town
38.087961
140.741531
58
Miyagi
Watari Town
38.026111
140.852222
59
Ibaraki
Kitaibaraki City
36.776194
140.720444
60
Ibaraki
Takahagi City
36.707583
140.718639
61
Ibaraki
Hitachi City
36.678556
140.623111
62
Tochigi
Nasu Town
37.043333
140.088056
Deposition amount of
Pu -241(Bq/m2)
Not Detectable
(Lower detection limit：90)
Not Detectable
(Lower detection limit：110)
Not Detectable
(Lower detection limit：48)
Not Detectable
(Lower detection limit：120)
Not Detectable
(Lower detection limit：53)
Estimated effective dose over 50
years for Pu-241 using the
conversion factor of IAEA-TECDOC-1162 (mSv)
ー
ー
ー
ー
ー
Attachment 2
(Reference) The deposition amount of Pu-238, Pu-239/240
for each sample (Bq/m2)
Pu-238
Pu-(239 ＋240)
Not Detectable
(Lower detection limit：0.91)
Not Detectable
(Lower detection limit：1.1)
Not Detectable
(Lower detection limit：1.4)
Not Detectable
(Lower detection limit：1.2)
Not Detectable
(Lower detection limit：0.53)
0.57
3.5
2.5
4.8
1.5
5.2
Not Detectable
(Lower detection limit：0.48)
0.66
44
8.3E-03
Not Detectable
(Lower detection limit：52)
Not Detectable
(Lower detection limit：42)
Not Detectable
(Lower detection limit：91)
Not Detectable
(Lower detection limit：46)
Not Detectable
(Lower detection limit：29)
Not Detectable
(Lower detection limit：47)
Not Detectable
ー
0.55
ー
Not Detectable
(Lower detection limit：0.42)
Not Detectable
(Lower detection limit：0.92)
Not Detectable
(Lower detection limit：1.2)
Not Detectable
(Lower detection limit：0.74)
Not Detectable
(Lower detection limit：0.79)
Not Detectable
Not Detectable
(Lower detection limit：0.59)
(Lower detection limit：0.59)
(Lower detection limit：51)
Not Detectable
(Lower detection limit：150)
Not Detectable
(Lower detection limit：62)
Not Detectable
(Lower detection limit：32)
Not Detectable
(Lower detection limit：22)
Not Detectable
(Lower detection limit：100)
Not Detectable
(Lower detection limit：43)
Not Detectable
(Lower detection limit：97)
Not Detectable
(Lower detection limit：42)
Not Detectable
(Lower detection limit：54)
Not Detectable
(Lower detection limit：32)
ー
ー
ー
ー
ー
ー
ー
ー
ー
ー
ー
ー
ー
ー
ー
Not Detectable
(Lower detection limit：1.1)
Not Detectable
(Lower detection limit：1.5)
Not Detectable
(Lower detection limit：0.47)
Not Detectable
(Lower detection limit：0.78)
Not Detectable
(Lower detection limit：1.1)
Not Detectable
(Lower detection limit：0.64)
Not Detectable
(Lower detection limit：0.97)
Not Detectable
(Lower detection limit：1.4)
Not Detectable
(Lower detection limit：1.1)
Not Detectable
(Lower detection limit：1.3)
15
2.9
10
0.44
0.95
1.6
Not Detectable
(Lower detection limit：1.5)
0.93
3.5
6.9
4.3
2.4
9.2
Not Detectable
(Lower detection limit：1.1)
0.94
Attachment 3
Nuclide Analysis Results of Pu-238 and Pu-(239+240) (Second Soil Survey)
ＮＤ
Legend
Deposition amounts of Pu-238
and Pu-(239+240) (Bq/m2)
(As of June 14, 2011) 平成23年6月14日時点
Survey points
MEXT
First
survey
Fukushima MEXT
pref. survey second
survey
Pu-238 and Pu-(239+240) were detected
Or only Pu-238 was detected (derived from the accident)
(None)
Pu-238 and Pu-(239+240) were detected
Either only Pu-(239+240) were detected, or none were
detected
Upper: Measured value of Pu-238
Lower: Measured value of Pu-(239+240)
Planned
evacuation
areas
Emergency
evacuation
preparation areas
Terminated on September 30, 2011
Habitable
Non-habitable
(2km×2km)
(2km×2km)
(10km×10km)
Fukushima Dai-ichi NPS
※ This map includes the values for the results of the first soil survey conducted by MEXT in the previous year (announced on September 30, 2011), as well as the survey conducted by Fukushima prefecture (announced on April 6, 2012)
that has been adjusted in consideration of the physical reduction as of June 14, 2011, in addition to the results for the second soil survey conducted by MEXT.
※We assumed that the ratios of deposition amounts of Pu-238 and Pu-(239+240) that were measured for 11 years in a nation-wide survey from FY1999 to FY2009 form a lognormal distribution,
and deduced the spot where the ratio for the deposition amount of Pu-238 against Pu-(239+240) was higher than 0.053, suggesting the strong possibility that the Pu-238 was derived from the Fukushima Dai-ichi NPS. We marked the spot by a circle on the map.
Relation Between Pu-238 and Pu-(239+240) Confirmed So Far in a Nationwide Survey
Attachment 4
○ In order to confirm the ratio of deposition amounts of Pu-238 against those of Pu-(239+240) that were measured before the accident (hereafter “Pu-238/Pu(239+240) before the accident”) at Fukushima Dai-ichi NPS, the distribution situation of the ratios for the samples (159 samples) where Pu-238 and Pu(239+240) were detected in the environmental radioactivity monitoring survey from FY1999 to FY2009 were confirmed.
○ As a result, it was confirmed that the Pu-238 and Pu(239+240) that were deposited in the soil through atmospheric nuclear tests, etc. before the
accident at Fukushima Dai-ichi NPS did not form a lognormal distribution, but the distribution was close to that of a lognormal distribution.
○ Moreover, it was also confirmed from the results of the first soil survey that the amounts of Pu-238/Pu-(239+240) at the points where they had been
newly deposited due to the accident at Fukushima Dai-ichi NPP were larger than those of Pu-238/Pu-(239+240) before the accident.
○ Therefore, we made the assumption in this survey that the Pu-238/Pu-(239+240) before the accident formed a lognormal distribution, and that at any point
with a ratio deviating from the Pu-238/Pu-(239+240) before the accident, there is a high possibility that Pu-238 and Pu-(239+240) had been newly
deposited by the accident at Fukushima Dai-ichi NPS.
* When seen from a statistical point of view, in a case where the ratio exceeded the maximum value for Pu-238/Pu-(239+240) within the range that includes around 95% of the
Pu-238/Pu-(239+240) that was measured before the accident (“Average value of Pu-238/Pu-(239+240) before the accident + twice the standard deviation” (=0.053)), it was
assumed that there was a high possibility that Pu-238/Pu-(239+240) had originated from the accident at Fukushima Dai-ichi NPS.
Frequency
Frequency
Lognormal distribution
For points where Pu-238/Pu(239+240) exceeded 0.053, it
was assumed that there was a
high possibility that they had
originated from the accident
at Fukushima Dai-ichi NPS
Results of the environmental radioactivity monitoring survey from
FY1999 to FY2009