Speaker
Mr
hiroshi ITO
(Chiba University)
Description
Radioisotope have been emitted around Japan by a nuclear accident at the Fukushima No. 1 nuclear power plant in March 2011. A problem is the contaminated water including the atomic nucleus which relatively has a long half-life time such as 90Sr, 137Cs generated from 235U used for nuclear fuel in particular. Particular, since 90Sr has a long biological half-life time (49 years), it is dangerous to cause internal exposure. Therefore, real-time 90Sr counter is required. It is relatively easy to identify a nucleus emitting gamma ray. But it is more difficult to identify a nucleus emitting pure beta ray such as 90Sr. Typically, measurement of a radioactivity absolute value of 90Sr takes a month at least to give a result. At first, we aim to identify 90Sr/137Cs by threshold type Cherenkov detection. It needs radiator which has less than 1.0492 of refractive index for identification 2.28 MeV of maximum kinematic energy of beta ray from 90Sr and 1.17 MeV of maximum kinematic energy of beta ray from 137Cs. Recent, The material satisfying this request does not exist expect the silica aerogel. We produced prototype and evaluated performance. We achieved 103 of Sr/Cs detection efficiency ratio, 10-3 Hz/ Bq of 90Sr sensitivity at one minute.
Primary author
Mr
hiroshi ITO
(Chiba University)
Co-authors
Mr
Daisuke Kumogoshi
(Chiba University)
Mr
Hideyuki Kawai
(Chiba University)
Mr
Keiichi Mase
(Chiba University)
Mr
Makoto Tabata
(Chiba University)
Mr
Satoshi Kodama
(Chiba University)
Mr
Shutaro Iijima
(Chiba University)
Mr
Soorim Han
(Chiba University)
