Development of elemental technology for alpha-ray dust monitor for in-situ measurement of radioactive aerosol in dismantling and decommissioning

Tsubota, Yoichi   ; Honda, Fumiya; Nakagawa, Takahiro ; Kawasaki, Takashi ; Tamakuma, Yuki*; Tokonami, Shinji*; Momose, Takumaro  

A large number of radioactive aerosols, especially alpha particles, are expected to be generated during fuel debris retrieval on Fukushima - Daiichi (1F) site and decommissioning of nuclear fuel cycle facilities. In the case of conventional alpha dust monitor, silicon surface barrier detector (SSBD) is often used as a detector which has not so high limit of count rates. Moreover, SSBD is not suitable for high humidity environment. In this work, we developed a prototype of alpha dust monitor aiming at an in-situ measurement of high concentration of airborne alpha particles. Approx. 20M cpm of counting rate was achieved which was more than 10 times higher compared to a conventional alpha dust monitor using SSBD. For follow-up test, counting rate of prototype alpha dust monitor was smoothly followed with respect to the airborne concentration of alpha particles.