Apr 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 Apr 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	January-2025			February-2025			March-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	0	0	0	1	1	0	7	7
5<E≤10	0	34	34	0	91	91	0	67	67
1<E≤5	13	481	494	6	604	610	20	637	657
E≤1	985	6391	7376	982	6347	7329	982	6143	7125
Total	998	6906	7904	988	7043	8031	1002	6854	7856
Maximum(mSv)	4.50	10.00	10.00	2.70	10.30	10.30	3.85	11.86	11.86
Average(mSv)	0.08	0.28	0.25	0.06	0.38	0.34	0.09	0.37	0.33

(*)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).

(2)Combined Cumulative Effective Dose from April 2021 (Internal and External)
Effective dose (E) mSv	April 2021 - February 2025			April 2021 - March 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	108	108	0	118	118	0	10	10
20<E≤50	33	1299	1332	35	1340	1375	2	41	43
10<E≤20	70	1942	2012	72	2004	2076	2	62	64
5<E≤10	138	1766	1904	142	1758	1900	4	-8	-4
1<E≤5	385	2920	3305	383	2910	3293	-2	-10	-12
E≤1	1295	8943	10238	1293	8985	10278	-2	42	40
Total	1921	16978	18899	1925	17115	19040	4	137	141
Maximum(mSv)	34.92	66.22	66.22	35.25	66.69	66.69	-	-	-
Average(mSv)	2.07	5.54	5.19	2.12	5.65	5.29	-	-	-

(*) 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 - February 2025			April 2024 - March 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	0	0	0	0	0	0	0	0
20<E≤50	0	0	0	0	0	0	0	0	0
10<E≤20	3	635	638	4	813	817	1	178	179
5<E≤10	36	996	1032	46	987	1033	10	-9	1
1<E≤5	168	2016	2184	169	2090	2259	1	74	75
E≤1	1189	6651	7840	1191	6609	7800	2	-42	-40
Total	1396	10298	11694	1410	10499	11909	14	201	215
Maximum(mSv)	11.30	16.60	16.60	11.50	16.82	16.82	-	-	-
Average(mSv)	0.61	2.07	1.89	0.67	2.27	2.08	-	-	-

(*): 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*
(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.