Investigation of Main Radiation Source above Shield Plug of Unit 3 at Fukushima Daiichi Nuclear Power Station

• Main Authors: Hiratama Hideo, Kondo Kenjiro, Suzuki Seishiro, Tanimura Yoshihiko, Iwanaga Kohei, Nagata Hiroshi
• Format: Article
• Language: English
• Published: EDP Sciences 2017-01-01
• Series: EPJ Web of Conferences
• Subjects: Unit 3; Fukushima Daiichi; CdZnTe; pulse height distribution; EGS5
• Online Access: https://doi.org/10.1051/epjconf/201715308010

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.