2016-07 – TEPCO – Fukushima Daiichi – Evaluation of the exposure dose of workers at the Fukushima Daiichi Nuclear Power Station

2016-07 - TEPCO - Fukushima Daiichi - Evaluation of the exposure dose of workers at the Fukushima Daiichi Nuclear Power Station

Leave a Reply

Your email address will not be published. Required fields are marked *

Attachment
Exposure Dose Distribution
1. Effective Dose from External Exposure
Table 1 shows the distribution of external exposure dose of workers who were involved in radiation
work at the Fukushima Daiichi Nuclear Power Station in the past three months.
Table 1. External Exposure Dose
・The values of the exposure dose and the number of the workers in the table above are subject to change, because there are times when APD
data are replaced with monthly dose data measured by integral dosimeters. Or dose data of workers who wore only an integral dosimeter (ex.,
workers who entered only the Main Anti-earthquake Building) need to be updated in the table after the publication of the data.
2. Sum of External and Internal Exposure Dose (Effective Dose)
Table 2 shows the distribution of cumulative exposure dose of workers who were involved in radiation
work at Fukushima Daiichi in the five years, starting from April 1, 2016. Table 3 shows the distribution of
cumulative exposure dose in the fiscal year of 2016. The tables show the data in two different periods of
time, from April 1, 2016 to June 30, 2016 and from April 1, 2016 to July 31, 2016 for comparison.
Table 2. Cumulative Exposure Dose in the Five Years
TEPCO’s
Employees Contractors Total
TEPCO’s
Employees Contractors Total
TEPCO’s
Employees Contractors Total
Above 100 0 0 0 0 0 0 0 0 0
75-100 0 0 0 0 0 0 0 0 0
50-75 0 0 0 0 0 0 0 0 0
20-50 0 6 6 0 11 11 0 5 5
10-20 0 61 61 0 145 145 0 84 84
5-10 0 328 328 4 467 471 4 139 143
1-5 142 2014 2156 180 2448 2628 38 434 472
1 or less 1164 7901 9065 1238 7766 9004 74 -135 -61
Total 1306 10310 11616 1422 10837 12259 116 527 643
Maximum (mSv) 4.90 32.46 32.46 6.22 33.23 33.23 – – –
Average (mSv) 0.40 0.97 0.91 0.44 1.22 1.13 – – –
Dose Ranges (mSv)
April 2016 – June 2016 April 2016 – July 2016 Difference
・The values of the exposure dose and the number of the workers in the table above are subject to change, because there are times when APD
data are replaced with monthly dose data measured by integral dosimeters. Or dose data of workers who wore only an integral dosimeter (ex.,
workers who entered only the Main Anti-earthquake Building) need to be updated in the table after the publication of the data.
・No significant internal exposure has been reported since October 2011.
TEPCO’s
Employees Contractors Total
TEPCO’s
Employees Contractors Total
TEPCO’s
Employees Contractors Total
Above 100 0 0 0 0 0 0 0 0 0
75-100 0 0 0 0 0 0 0 0 0
50-75 0 0 0 0 0 0 0 0 0
20-50 0 0 0 0 0 0 0 0 0
10-20 0 0 0 0 6 6 0 2 2
5-10 0 19 19 0 56 56 0 70 70
1-5 9 651 660 26 833 859 11 735 746
1 or less 1128 7748 8876 1166 7928 9094 1020 7749 8769
Total 1137 8418 9555 1192 8823 10015 1031 8556 9587
Maximum (mSv) 2.50 9.70 9.70 2.00 13.81 13.81 1.92 10.42 10.42
Average (mSv) 0.14 0.32 0.30 0.16 0.41 0.38 0.10 0.37 0.34
Dose Ranges (mSv)
May 2016 June 2016 July 2016
Table 3. Cumulative Exposure Dose in the Fiscal Year of 2016
・The values of the exposure dose and the number of the workers in the table above are subject to change, because there are times when APD
data are replaced with monthly dose data measured by integral dosimeters. Or dose data of workers who wore only an integral dosimeter (ex.,
workers who entered only the Main Anti-earthquake Building) need to be updated in the table after the publication of the data.
3. Sum of External and Internal Exposure Dose of Workers Exposed to Especially High Radiation (Effective Dose)
Table 4 shows the distribution of cumulative exposure dose of workers exposed to especially high
radiation.*1
Table 4. Cumulative Exposure Dose (workers exposed to especially high radiation)
(From October 2015, TEPCO Holdings has opted not to report to the Labour Standards Inspection Office about workers exposed to especially
high radiation.)
*1. Workers exposed to especially high radiation means workers who are involved in operations in which they could be exposed to the
emergency exposure dose limit (100mSv), which is stipulated in “Ordinance on Prevention of Ionizing Radiation Hazards, Chapter 7.” In more
detail, they are workers engaged in the work to maintain the function of the cooling facility to cool down the reactor facility or the spent fuel
tank in the reactor facility, the steam turbine and its related facilities or the surrounding area where the radiation doses exceed 0.1mSv/h. Or
they are workers who would engage in keeping running the function to control or prevent the release of a large number of radioactive materials
should it be likely to occur due to malfunction or damage of the reactor facility.
So far workers who have worked as “workers exposed to especially high radiation” are all TEPCO employees.
*2. The number of “workers exposed to especially high radiation” each month is the number of the workers who reported working as such
workers in a given month and were engaged in that work. The figures in the cumulative data during the period from March 2011 to September
2015 in Table 4 above include the numbers of workers who have been reported to work as “workers exposed to especially high radiation” at
least once.
*3. The values of the exposure dose and the number of the workers in the table above are subject to change, because there are times when APD
TEPCO’s
Employees Contractors Total
TEPCO’s
Employees Contractors Total
TEPCO’s
Employees Contractors Total
Above 100 0 0 0 0 0 0 0 0 0
75-100 0 0 0 0 0 0 0 0 0
50-75 0 0 0 0 0 0 0 0 0
20-50 0 6 6 0 11 11 0 5 5
10-20 0 61 61 0 145 145 0 84 84
5-10 0 328 328 4 467 471 4 139 143
1-5 142 2014 2156 180 2448 2628 38 434 472
1 or less 1164 7901 9065 1238 7766 9004 74 -135 -61
Total 1306 10310 11616 1422 10837 12259 116 527 643
Maximum (mSv) 4.90 32.46 32.46 6.22 33.23 33.23 – – –
Average (mSv) 0.40 0.97 0.91 0.44 1.22 1.13 – – –
April 2016 – July 2016 Difference
Dose Ranges (mSv)
April 2016 – June 2016
Above 100
75-100
50-75
20-50
10-20
5-10
1-5
1 or less
Total
Maximum (mSv)
Average (mSv)
102.69
36.49
Dose Ranges (mSv)
129
51
1203
145
1
191
233
267
186
March 2011 – September 2015
data are replaced with monthly dose data measured by integral dosimeters. Or the dose data of workers who wore only an integral dosimeter
(ex., workers who entered only the Main Anti-earthquake Building) need to be updated in the table after the publication of the data.
*4. The figure shown in the dose range, “Above 100mSv,” in the cumulative data during the period from March 2011 to September 2015 is the
figure when the March 2011 data of the internal exposure dose were reevaluated in July 2013.
4. Equivalent Dose
Table 5 and Table 6 show equivalent dose to the skin and the lens of the eyes of the workers, respectively,
who were involved in radiation work at the Fukushima Daiichi Nuclear Power Station in the past three
months.
Table 5. Equivalent Dose to the Skin
・The values of the exposure dose and the number of the workers in the table above are subject to change, because there are times when APD
data are replaced with monthly dose data measured by integral dosimeters. Or the dose data of workers who wore only an integral dosimeter
(ex., workers who entered only the Main Anti-earthquake Building) need to be updated in the table after the publication of the data.
・Equivalent dose is a measure of the radiation dose to organs and tissues, and the equivalent dose limit to the skin is 500mSv/year (the
emergency exposure dose limit is 1Sv).
・Equivalent dose to the skin is measured at a depth of 70 micrometers from the skin surface. When the equivalent dose is measured with a
dosimeter other than the one put on around the chest and the abdomen, for example, a finger dosimeter, the maximum measurement value is
counted as the equivalent dose.
Table 6. Equivalent Dose to the Lens of the Eyes
TEPCO’s
Employees Contractors Total
TEPCO’s
Employees Contractors Total
TEPCO’s
Employees Contractors Total
Above 500 0 0 0 0 0 0 0 0 0
300-500 0 0 0 0 0 0 0 0 0
250-300 0 0 0 0 0 0 0 0 0
200-250 0 0 0 0 0 0 0 0 0
150-200 0 0 0 0 0 0 0 0 0
100-150 0 0 0 0 0 0 0 0 0
75-100 0 0 0 0 0 0 0 0 0
50-75 0 0 0 0 0 0 0 0 0
20-50 0 7 7 0 5 5 0 0 0
10-20 0 9 9 0 23 23 0 17 17
5-10 4 79 83 0 166 166 0 115 115
1-5 10 996 1006 37 1158 1195 11 871 882
1 or less 1123 7327 8450 1155 7471 8626 1020 7553 8573
Total 1137 8418 9555 1192 8823 10015 1031 8556 9587
Maximum (mSv) 5.70 33.00 33.00 4.50 40.70 40.70 1.92 16.38 16.38
Average (mSv) 0.16 0.51 0.47 0.18 0.64 0.58 0.10 0.47 0.43
Dose Ranges (mSv)
May 2016 June 2016 July 2016
TEPCO’s
Employees Contractors Total
TEPCO’s
Employees Contractors Total
TEPCO’s
Employees Contractors Total
Above 150 0 0 0 0 0 0 0 0 0
100-150 0 0 0 0 0 0 0 0 0
75-100 0 0 0 0 0 0 0 0 0
50-75 0 0 0 0 0 0 0 0 0
20-50 0 0 0 0 0 0 0 0 0
10-20 0 1 1 0 15 15 0 17 17
5-10 0 42 42 0 115 115 0 115 115
1-5 9 819 828 28 996 1024 11 871 882
1 or less 1128 7556 8684 1164 7697 8861 1020 7553 8573
Total 1137 8418 9555 1192 8823 10015 1031 8556 9587
Maximum (mSv) 2.50 11.90 11.90 2.00 13.81 13.81 1.92 16.38 16.38
Average (mSv) 0.14 0.40 0.37 0.16 0.51 0.47 0.10 0.47 0.43
Dose Ranges (mSv)
May 2016 June 2016 July 2016
・The values of the exposure dose and the number of the workers in the table above are subject to change, because there are times when APD
data are replaced with monthly dose data measured by integral dosimeters. Or the dose data of workers who wore only an integral dosimeter
(ex., workers who entered only the Main Anti-earthquake Building) need to be updated in the table after the publication of the data.
・Equivalent dose is a measure of the radiation dose to organs and tissues, and the equivalent dose limit to the lens of the eye is 150mSv/year
(the emergency exposure dose limit is 300mSv).
・The equivalent dose to the lens of the eyes is measured at a depth of 70 micrometers from the skin surface using a dosimeter put on around
the chest or the abdomen, and thus the shielding effect of face masks is not taken into consideration.
5. Cumulative Equivalent Dose
Table 7 and Table 8 show the distribution of cumulative equivalent dose to the skins and the lens of the
eyes of the workers, respectively, who were involved in radiation work at the Fukushima Daiichi Nuclear
Power Station during two different periods of time, from April 1, 2016 to June 30, 2016 and from April 1,
2016 to July 31, 2016 for comparison.
Table 7. Equivalent Dose to the Skin
・The values of the exposure dose and the number of the workers in the table above are subject to change, because there are times when APD
data are replaced with monthly dose data measured by integral dosimeters. Or the dose data of workers who wore only an integral dosimeter
(ex., workers who entered only the Main Anti-earthquake Building) need to be updated in the table after the publication of the data.
Table 8. Equivalent Dose to the Lens of the Eyes
TEPCO’s
Employees Contractors Total
TEPCO’s
Employees Contractors Total
TEPCO’s
Employees Contractors Total
Above 500 0 0 0 0 0 0 0 0 0
300-500 0 0 0 0 0 0 0 0 0
250-300 0 0 0 0 0 0 0 0 0
200-250 0 0 0 0 0 0 0 0 0
150-200 0 0 0 0 0 0 0 0 0
100-150 0 2 2 0 2 2 0 0 0
75-100 0 3 3 0 4 4 0 1 1
50-75 0 2 2 0 2 2 0 0 0
20-50 0 48 48 0 99 99 0 51 51
10-20 0 247 247 1 333 334 1 86 87
5-10 8 585 593 10 688 698 2 103 105
1-5 145 2175 2320 182 2497 2679 37 322 359
1 or less 1153 7248 8401 1229 7212 8441 76 -36 40
Total 1306 10310 11616 1422 10837 12259 116 527 643
Maximum (mSv) 9.70 104.70 104.70 11.62 105.47 105.47 – – –
Average (mSv) 0.45 1.58 1.45 0.48 1.88 1.72 – – –
Dose Ranges (mSv)
April 2016 – June 2016 April 2016 – July 2016 Difference
TEPCO’s
Employees Contractors Total
TEPCO’s
Employees Contractors Total
TEPCO’s
Employees Contractors Total
Above 150 0 0 0 0 0 0 0 0 0
100-150 0 0 0 0 0 0 0 0 0
75-100 0 0 0 0 0 0 0 0 0
50-75 0 0 0 0 0 0 0 0 0
20-50 0 23 23 0 60 60 0 37 37
10-20 0 147 147 0 245 245 0 98 98
5-10 1 446 447 4 584 588 3 138 141
1-5 146 2106 2252 182 2462 2644 36 356 392
1 or less 1159 7588 8747 1236 7486 8722 77 -102 -25
Total 1306 10310 11616 1422 10837 12259 116 527 643
Maximum (mSv) 5.30 36.50 36.50 6.22 44.68 44.68 – – –
Average (mSv) 0.41 1.23 1.14 0.45 1.54 1.42 – – –
April 2016 – July 2016 Difference
Dose Ranges (mSv)
April 2016 – June 2016
・The values of the exposure dose and the number of the workers in the table above are subject to change, because there are times when APD
data are replaced with monthly dose data measured by integral dosimeters. Or the dose data of workers who wore only an integral dosimeter
(ex., workers who entered only the Main Anti-earthquake Building) need to be updated in the table after the publication of the data.
End