@inproceedings{oai:repo.qst.go.jp:00054361,
 author = {Kurihara, Osamu and Kanai, Katsuta and Nakagawa, Takahiro and Takada, Chie and Momose, Takumaro and Furuta, Sadaaki and 栗原 治},
 book = {NIRS Symposium on Reconstruction of Early Internal Dose in the TEPCO Fukushima Daiichi Nuclear Power Station Accident : Proceedings},
 issue = {NIRS-M-252},
 month = {Dec},
 note = {Japan Atomic Energy Agency (JAEA) performed internal dose measurements of employees involved in the Fukushima Daiichi nuclear power station accident. Nuclear Fuel Cycle Engineering Laboratories (NFCEL), one of the JAEA's core centers, examined 560 of these employees by direct (in vivo) measurements during the period from April 20 to August 5 in 2011. These measurements consisted of whole-body counting for radiocesium and thyroid counting for radioiodine. The whole-body counting was conducted with two types of whole-body counters (WBCs): a standing-type WBC with two large NaI(Tl) detectors (FastscanTM, Canberra Inc.) and a chair-type WBC with HPGe detectors (GC5021, Canberra Inc.) installed in a shielded chamber made of 20-cm-thick steel. The thyroid counting was mainly performed using one of the two HPGe detectors equipped with the chair-type WBC. The subjects examined in this work were divided into two groups: Group 1 was the first 39 subjects who were measured up to June 17, 2011 and Group 2 was the remaining 521 subjects who were measured on and after June 18, 2011. We validated the performance of our direct measurements by comparing measurement results of the Group 1 subjects using two different methods (e.g., the standing-type WBC vs. the chair-type WBC). Tentative internal dose estimates of the subjects of Group 1 were also performed based on the assumption of a single intake scenario on either March 12, when the first hydrogen explosion occurred at the station or the first day of work after the accident. It was found that the contribution of 131I to the total internal dose greatly exceeded those of 134Cs and 137Cs, the other major nuclides detected in the measurements. The maximum committed effective dose (CED) was found in a male subject whose thyroid content of 131I was 9760 Bq on May 23, 2011; the CED of this subject was estimated to be 600 mSv including a small contribution of 134Cs and 137Cs. The typical minimum detectable activity for 131I in the present thyroid counting was 10 Bq for a counting time of 10 min, making it difficult to identify a residual thyroid content corresponding to a CED of 20 mSv for the subjects of Group 2.},
 pages = {13--25},
 publisher = {National Institute of Radiological Sciences},
 title = {Direct measurements of employees involved in the Fukushima Daiichi nuclear power station accident for internal dose estimates: JAEA's experiences},
 volume = {1},
 year = {2012}
}