Jan 31, 2025 | Status of Radiation Exposure | TEPCO Fukushima Daiichi NPP

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

Updated on 31 Jan 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	October-2024			November-2024			December-2024
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	3	3	0	0	0
5<E≤10	0	62	62	1	81	82	0	61	61
1<E≤5	16	554	570	17	501	518	21	446	467
E≤1	1022	6289	7311	1034	6318	7352	995	6452	7447
Total	1038	6905	7943	1052	6903	7955	1016	6959	7975
Maximum(mSv)	4.10	9.90	9.90	5.10	10.90	10.90	2.35	9.70	9.70
Average(mSv)	0.09	0.34	0.31	0.09	0.35	0.31	0.09	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 - November 2024			April 2021 - December 2024			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	73	73	0	89	89	0	16	16
20<E≤50	30	1217	1247	31	1231	1262	1	14	15
10<E≤20	69	1860	1929	68	1898	1966	-1	38	37
5<E≤10	125	1670	1795	130	1697	1827	5	27	32
1<E≤5	374	2842	3216	383	2876	3259	9	34	43
E≤1	1305	8718	10023	1294	8814	10108	-11	96	85
Total	1903	16380	18283	1906	16605	18511	3	225	228
Maximum(mSv)	33.32	62.52	62.52	34.57	63.98	63.98	-	-	-
Average(mSv)	1.98	5.35	5.00	2.02	5.39	5.04	-	-	-

(*) 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 - November 2024			April 2024 - December 2024			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	0	332	332	2	425	427	2	93	95
5<E≤10	22	717	739	25	809	834	3	92	95
1<E≤5	140	1742	1882	157	1877	2034	17	135	152
E≤1	1205	6622	7827	1193	6639	7832	-12	17	5
Total	1367	9413	10780	1377	9750	11127	10	337	347
Maximum(mSv)	10.00	16.40	16.40	10.95	16.46	16.46	-	-	-
Average(mSv)	0.46	1.57	1.43	0.52	1.72	1.57	-	-	-

(*): 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.