Development of gamma camera for survey of contamination distribution; Performance demonstration of gamma camera based on survey of contamination on operating floor of the Fukushima Daiichi Nuclear Power Plant Unit 2 reactor building by -eyeII

Kanayama, Fumihiko ; Okada, Takashi ; Fukushima, Mineo ; Yoshimoto, Katsunobu*; Hanyu, Toshinori; Kawanobe, Takayuki

For planning of removing fuels and debris from the Unit 2 reactor building, TEPCO has already started to measure dose rate over the floor by remotely operated vehicle. Because the measured data were widely distributed in the range of several decades to one thousand mSv/h, it is necessary for TEPCO to survey of contamination distribution on operation floor 2 for more detail planning. JAEA estimated sensitivity of developed gamma camera system named "-eye II" in consistency with actual radiation condition, and carried a demonstration experiment at Fukushima Daiichi N.P.P. to confirm a strength of jamming by back ground dose. Then, JAEA surveyed contamination distribution of operating floor using -eye II. At the result of survey, it was found that, - main radiation source in survey area was located on upper reactor well, - western floor in survey area was lower the margin of capacity of -eye II, -there was a highly contaminated spot on the floor near the opened BOP.