Ministry of Health, Labour and Welfare

Ministry of Health, Labour and Welfare

In Focus: Radiation Protection at Works Relating to TEPCO's Fukushima Daiichi Nuclear Power Plant Accident

Exposure Dose Distribution of the Workers at Fukushima Daiichi Nuclear Power Plant

Updated on 30 Aug 2024

1. Radiation Exposure Dose Distributions

(1)The distribution of external exposure dose of the workers during the last 3 months
(Numbers of workers who entered each area every month)
Effective dose (E) mSv May-2024 June-2024 July-2024
TEPCO Contractors Total TEPCO Contractors Total TEPCO Contractors Total
100<E 0 0 0 0 0 0 0 0 0
75<E≤100 0 0 0 0 0 0 0 0 0
50<E≤75 0 0 0 0 0 0 0 0 0
20<E≤50 0 0 0 0 0 0 0 0 0
10<E≤20 0 0 0 0 0 0 0 0 0
5<E≤10 0 17 17 0 28 28 0 43 43
1<E≤5 8 354 362 18 529 547 16 433 449
E≤1 971 6162 7133 1024 6201 7225 923 6298 7221
Total 979 6533 7512 1042 6758 7800 939 6774 7713
Maximum(mSv) 4.20 7.20 7.20 3.80 7.70 7.70 4.10 8.11 8.11
Average(mSv) 0.08 0.22 0.20 0.08 0.31 0.28 0.08 0.27 0.25

(*)Exposure doses and the number of workers are subject to change due to the replacement of accumulated doses measured using PAD with monthly doses measured using an integrating dosimeter and the reflection of values for workers wearing only an integrating dosimeter (e.g., workers working only within a seismically isolated building).

(2)Combined Cumulative Effective Dose from April 2021 (Internal and External)
Effective dose (E) mSv April 2021 - June 2024 April 2021 - July 2024 Difference
TEPCO Contractors Total TEPCO Contractors Total TEPCO Contractors Total
100<E 0 0 0 0 0 0 0 0 0
75<E≤100 0 0 0 0 0 0 0 0 0
50<E≤75 0 14 14 0 19 19 0 5 5
20<E≤50 27 1112 1139 27 1142 1169 0 30 30
10<E≤20 58 1751 1809 61 1771 1832 3 20 23
5<E≤10 118 1557 1675 120 1585 1705 2 28 30
1<E≤5 364 2687 3051 365 2740 3105 1 53 54
E≤1 1253 8237 9490 1271 8335 9606 18 98 116
Total 1820 15358 17178 1844 15592 17436 24 234 258
Maximum(mSv) 31.72 55.82 55.82 32.02 57.62 57.62 - - -
Average(mSv) 1.85 5.07 4.73 1.86 5.11 4.77 - - -

(*) Exposure doses and the number of workers are subject to change due to the replacement of accumulated doses measured using PAD with monthly doses measured using an integrating dosimeter and the reflection of values for workers wearing only an integrating dosimeter (e.g., workers working only within a seismically isolated building).

(3) Combined Cumulative Effective Dose from April 2024
Effective dose (E) mSv April 2024 - June 2024 April 2024 - July 2024 Difference
TEPCO Contractors Total TEPCO Contractors Total TEPCO Contractors Total
100<E 0 0 0 0 0 0 0 0 0
75<E≤100 0 0 0 0 0 0 0 0 0
50<E≤75 0 0 0 0 0 0 0 0 0
20<E≤50 0 0 0 0 0 0 0 0 0
10<E≤20 0 28 28 0 49 49 0 21 21
5<E≤10 2 210 212 4 341 345 2 131 133
1<E≤5 55 961 1016 75 1266 1341 20 305 325
E≤1 1147 6479 7626 1172 6468 7640 25 -11 14
Total 1204 7678 8882 1251 8124 9375 47 446 493
Maximum(mSv) 5.80 13.60 13.60 6.28 15.05 15.05 - - -
Average(mSv) 0.19 0.67 0.60 0.24 0.86 0.77 - - -
(*)
Exposure doses and the number of workers are subject to change due to the replacement of accumulated dosesmeasured using PAD with monthly doses measured using an integrating dosimeter and the reflection of values for workers wearing only an integrating dosimeter (e.g., workers working only within a seismically isolated building).
(4) Distribution of sum of external exposure dose and internal exposure dose of workers engaged in specified high-dose work*
(Specified high-dose work has not been performed since October 2015.)
Effective dose (E) mSv March 2011- September 2015
100<E 1
75<E≤100 191
50<E≤75 233
20<E≤50 267
10<E≤20 186
5<E≤10 129
1<E≤5 145
E≤1 51
Total 1203
Maximum(mSv) 102.69
Average(mSv) 36.49

(As specified high-dose work has not been performed since October 2015, the table shows the data up to September 2015.)

(*)
Workers engaged in work to which dose limit (100 mSv) during emergency work is applied in line with Article 7 of the Ordinance on Prevention of Ionizing Radiation Hazards.
Specifically, these workers are those who are engaged in work to maintain the functions of a nuclear reactor facility or spent fuel storage pool, or in work to maintain functions to suppress or prevent the possible release of a large amount of radioactive materials due to a failure of or damage to the nuclear reactor facility at a location around the nuclear reactor facility, steam turbine, or accessory facility where hourly dose may exceed 0.1 mSv.
It should be noted that only TEPCO employees have so far been engaged in specified high-dose work.
(*)
The number of workers engaged in specified high-dose work is that of workers who were registered as such at least once during the period between March 2011 and September 2015.
(*)
Exposure doses and the number of workers are subject to change due to the replacement of accumulated doses measured using PAD with monthly doses measured using an integrating dosimeter and the reflection of values for workers wearing only an integrating dosimeter (e.g., workers working only within a seismically isolated building).
(*)
The results of re-evaluating committed doses in March 2011 reveal that maximum cumulative effective doses for the period between March 2011 and September 2015 exceeded 100.
Archives