Development of realtime 90Sr counter used in low rate radioactive

Because of the disaster of Fukushima No.1 nuclear power plant in 2011, a large amount of radioactive substance (including ⁹⁰Sr and ¹³⁷Cs) was released into the Japanese coast of the Pacific Ocean. ⁹⁰Sr can be more dangerous than ¹³⁷Cs. Since ⁹⁰Sr does not emit γ rays, it is very difficult to measure its radioactivity. We have made threshold-type Cherenkov counter using silica aerogel with a refractive index n~1.04, the size of 10cm * 30cm. And now, We propose a 50cm * 200cm size detector. The test shows we can make the large type detector.