June 30, 2022 | Status of Radiation Exposure | TEPCO Fukushima Daiichi NPP

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

Updated on 30 June 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	March-2022			April-2022			May-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	3	3	0	0	0	0	0	0
5<E≤10	0	37	37	0	4	4	0	0	0
1<E≤5	32	670	702	35	398	433	10	341	351
E≤1	969	5150	6119	988	5198	6186	980	5346	6326
Total	1001	5860	6861	1023	5600	6623	990	5687	6677
Maximum(mSv)	3.77	11.20	11.20	4.53	5.90	5.90	2.78	4.96	4.96
Average(mSv)	0.13	0.43	0.39	0.14	0.28	0.26	0.08	0.23	0.21

(*)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 - April 2022			April 2021 - May 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	3	3	0	12	12	0	9	9
10<E≤20	13	912	925	18	964	982	5	52	57
5<E≤10	63	949	1012	66	954	1020	3	5	8
1<E≤5	232	2267	2499	239	2289	2528	7	22	29
E≤1	1066	4935	6001	1064	5109	6173	-2	174	172
Total	1374	9066	10440	1387	9328	10715	13	262	275
Maximum(mSv)	15.95	20.71	20.71	16.44	22.70	22.70	-	-	-
Average(mSv)	0.95	2.85	2.60	1.00	2.91	2.67	-	-	-

(*) 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) mSv	April 2022			April 2022 - May 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	0	0	0	0	0
10<E≤20	0	0	0	0	0	0	0	0	0
5<E≤10	0	4	4	1	28	29	1	24	25
1<E≤5	35	398	433	66	835	901	31	437	468
E≤1	988	5198	6186	1034	5411	6445	46	213	259
Total	1023	5600	6623	1101	6274	7375	78	674	752
Maximum(mSv)	4.53	5.90	5.90	6.11	7.90	7.90	-	-	-
Average(mSv)	0.14	0.28	0.26	0.21	0.46	0.42	-	-	-

(*): 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.