https://doi.org/10.1051/epjconf/201715308010
Investigation of Main Radiation Source above Shield Plug of Unit 3 at Fukushima Daiichi Nuclear Power Station
1 Nuclear Regulation Authority, 1-9-9, Roppongi, Minato-ku, Tokyo, Japan 106-8450
2 High Energy Accelerator Research Organization, 1-1, Oho, Tsukuba-shi, Ibaraki, Japan 305-0801
* Corresponding Author: hideo.hirayama@kek.jp
Published online: 25 September 2017
Pulse height distributions were measured using a CdZnTe detector inside a lead collimator to investigate main source producing high dose rates above the shield plugs of Unit 3 at Fukushima Daiichi Nuclear Power Station. It was confirmed that low energy photons are dominant. Concentrations of Cs-137 under 60 cm concrete of the shield plug were estimated to be between 8.1E+9 and 5.7E+10 Bq/cm2 from the measured peak count rate of 0.662 MeV photons. If Cs-137 was distributed on the surfaces of the gaps with radius 6m and with the averaged concentration of 5 points, 2.6E+10 Bq/cm2, total amount of Cs-137 is estimated to be 30 PBq.
Key words: Unit 3 / Fukushima Daiichi / CdZnTe / pulse height distribution / EGS5
© The Authors, published by EDP Sciences, 2017
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
