May 30, 2025 | Status of Radiation Exposure | TEPCO Fukushima Daiichi NPP

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

Updated on 30 May 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	February-2025			March-2025			April-2025
Effective dose (E) mSv	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	1	1	0	2	2	0	1	1
5<E≤10	0	91	91	0	76	76	0	18	18
1<E≤5	6	604	610	17	602	619	13	526	539
E≤1	982	6347	7329	985	6174	7159	997	5968	6965
Total	988	7043	8031	1002	6854	7856	1010	6513	7523
Maximum(mSv)	2.70	10.30	10.30	3.60	10.80	10.80	1.80	10.64	10.64
Average(mSv)	0.06	0.38	0.34	0.08	0.36	0.33	0.07	0.28	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 - March 2025			April 2021 - April 2025			Difference
Effective dose (E) mSv	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	118	118	0	126	126	0	8	8
20<E≤50	35	1337	1372	38	1369	1407	3	32	35
10<E≤20	72	2003	2075	70	2014	2084	-2	11	9
5<E≤10	142	1761	1903	143	1760	1903	1	-1	0
1<E≤5	379	2899	3278	386	2922	3308	7	23	30
E≤1	1297	8997	10294	1290	9115	10405	-7	118	111
Total	1925	17115	19040	1927	17306	19233	2	191	193
Maximum(mSv)	35.22	66.62	66.62	36.64	68.21	68.21	-	-	-
Average(mSv)	2.11	5.64	5.29	2.14	5.69	5.33	-	-	-

(*) 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
Effective dose (E) mSv	TEPCO	Contractors	Total
100<E	0	0	0
75<E≤100	0	0	0
50<E≤75	0	0	0
20<E≤50	0	0	0
10<E≤20	0	1	1
5<E≤10	0	18	18
1<E≤5	13	526	539
E≤1	997	5968	6965
Total	1010	6513	7523
Maximum(mSv)	1.80	10.64	10.64
Average(mSv)	0.07	0.28	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).

(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.