Feb 28, 2025 | Status of Radiation Exposure | TEPCO Fukushima Daiichi NPP

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

Updated on 28 Feb 2025

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	November-2024			December-2024			January-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	3	3	0	0	0	0	2	2
5<E≤10	1	81	82	0	58	58	1	37	38
1<E≤5	17	501	518	19	412	431	15	510	525
E≤1	1034	6318	7352	997	6489	7486	982	6357	7339
Total	1052	6903	7955	1016	6959	7975	998	6906	7904
Maximum(mSv)	5.10	10.90	10.90	2.20	9.30	9.30	5.20	11.32	11.32
Average(mSv)	0.09	0.35	0.31	0.08	0.28	0.25	0.08	0.28	0.26

(*)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 - December 2024			April 2021 - January 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	88	88	0	102	102	0	14	14
20<E≤50	31	1226	1257	31	1260	1291	0	34	34
10<E≤20	68	1899	1967	70	1913	1983	2	14	16
5<E≤10	130	1697	1827	134	1717	1851	4	20	24
1<E≤5	379	2867	3246	388	2912	3300	9	45	54
E≤1	1298	8828	10126	1288	8876	10164	-10	48	38
Total	1906	16605	18511	1911	16780	18691	5	175	180
Maximum(mSv)	34.42	63.92	63.92	34.56	65.47	65.47	-	-	-
Average(mSv)	2.02	5.39	5.04	2.06	5.45	5.10	-	-	-

(*) 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 - December 2024			April 2024 - January 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	2	414	416	2	523	525	0	109	109
5<E≤10	25	812	837	35	862	897	10	50	60
1<E≤5	154	1830	1984	165	1967	2132	11	137	148
E≤1	1196	6694	7890	1182	6667	7849	-14	-27	-41
Total	1377	9750	11127	1384	10019	11403	7	269	276
Maximum(mSv)	10.80	16.40	16.40	10.94	16.41	16.41	-	-	-
Average(mSv)	0.52	1.71	1.57	0.58	1.86	1.71	-	-	-

(*): 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.