Development of an alpha dust monitor using a GPS scintillator plate

Morishita, Yuki   ; Kaneko, Junichi* ; Higuchi, Mikio*; Izaki, Kenji ; Yajima, Tatsuo*; Matsuura, Mitsugu*; Tamura, Ken; Torii, Tatsuo  

A dust monitor with a silicon surface barrier detector (SSBD) is introduced at a nuclear fuel facility to detect airborne contamination of Pu and Pu released by past accidents. However, an SSBD frequently produces false alarms, especially in a room with high humidity. We developed an alpha-particle spectrometer based on a cerium-doped GdSiO (GPS) scintillator plate and a photomultiplier tube (PMT). The energy resolution for 5.5-MeV alpha particles was 11.9% 0.2% of the FWHM. The efficiency was 92%, and it had a uniform sensitivity. By applying an energy window, the count-rate of the Rn progeny decreased by 77%. The GPS scintillator plate was able to measure the alpha spectrum even though the GPS scintillator got wet.