May 31, 2022 | Status of Radiation Exposure | TEPCO Fukushima Daiichi NPP

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

Updated on 31 May 2022

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	February-2022			March-2022			April-2022
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	8	8	0	3	3	0	0	0
5<E≤10	0	43	43	0	37	37	0	5	5
1<E≤5	20	708	728	32	670	702	35	405	440
E≤1	877	5106	5983	969	5150	6119	988	5190	6178
Total	897	5865	6762	1001	5860	6861	1023	5600	6623
Maximum(mSv)	4.43	12.70	12.70	3.77	11.20	11.20	4.53	5.84	5.84
Average(mSv)	0.11	0.46	0.41	0.13	0.43	0.39	0.14	0.27	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 2022			April 2021 - April 2022			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	3	3	0	3	3
10<E≤20	7	836	843	13	912	925	6	76	82
5<E≤10	59	925	984	63	946	1009	4	21	25
1<E≤5	209	2247	2456	231	2267	2498	22	20	42
E≤1	1083	4771	5854	1067	4938	6005	-16	167	151
Total	1358	8779	10137	1374	9066	10440	16	287	303
Maximum(mSv)	13.10	17.46	17.46	15.91	20.82	20.82	-	-	-
Average(mSv)	0.85	2.77	2.51	0.95	2.85	2.60	-	-	-

(*) 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 2022
Effective dose (E)	April 2022
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	0	0
5<E≤10	0	5	5
1<E≤5	35	405	440
E≤1	988	5190	6178
Total	1023	5600	6623
Maximum(mSv)	4.53	5.84	5.84
Average(mSv)	0.14	0.27	0.25

(*): 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.
(*): Workers engaged in specified high-dose work in each month is the number of workers registered as workers engaged in specified high-dose work in that month.
However, the total of March 2011 to September 2015 includes workers released from specified high-dose work.
(*): 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.