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 Jul 2025

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 April-2025 May-2025 June-2025
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 18 18 0 24 24 0 9 9
1<E≤5 13 517 530 5 398 403 2 395 397
E≤1 997 5978 6975 988 6155 7143 1041 6373 7414
Total 1010 6513 7523 993 6577 7570 1043 6777 7820
Maximum(mSv) 1.70 9.90 9.90 2.60 7.40 7.40 1.16 7.51 7.51
Average(mSv) 0.06 0.28 0.25 0.05 0.24 0.22 0.05 0.21 0.19

(*)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 - May 2025 April 2021 - June 2025 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 0 134 134 0 144 144 0 10 10
20<E≤50 38 1396 1434 38 1436 1474 0 40 40
10<E≤20 74 2010 2084 77 1991 2068 3 -19 -16
5<E≤10 139 1772 1911 139 1797 1936 0 25 25
1<E≤5 388 2939 3327 389 2936 3325 1 -3 -2
E≤1 1292 9225 10517 1367 9343 10710 75 118 193
Total 1931 17476 19407 2010 17647 19657 79 171 250
Maximum(mSv) 36.92 70.06 70.06 37.26 72.37 72.37 - - -
Average(mSv) 2.16 5.72 5.37 2.11 5.75 5.38 - - -

(*) 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 2025
Effective dose (E) mSv April 2025 - May 2025 April 2025 - June 2025 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 6 6 0 19 19 0 13 13
5<E≤10 0 99 99 0 190 190 0 91 91
1<E≤5 20 819 839 44 1042 1086 24 223 247
E≤1 1094 6248 7342 1189 6437 7626 95 189 284
Total 1114 7172 8286 1233 7688 8921 119 516 635
Maximum(mSv) 3.80 11.70 11.70 3.88 12.68 12.68 - - -
Average(mSv) 0.10 0.48 0.43 0.14 0.63 0.56 - - -
(*)
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).
(4) Distribution of sum of external exposure dose and internal exposure dose of workers engaged in specified high-dose work (Effective Dose)
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.
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