Identification procedure of natural radon (Rn) using electrostatic collection method

Nakamura, Masahiko; Matsuda, Makoto  ; Nakanoya, Takamitsu  ; Kabumoto, Hiroshi  ; Kutsukake, Kenichi ; Otokawa, Yoshinori  ; Asozu, Takuhiro  ; Ishii, Tetsuro  ; Asai, Masato  ; Okura, Takehisa 

Alpha rays (0.06 Bq/cm) were detected on the first basement passage of the Tandem Accelerator Facility. We attempted to identify the alpha-emitting nuclide with surveying this area. We found a crack of concrete at the detected spot. We inferred that radon may seep out of the crack from several phenomena observed in the survey of this area. Furthermore, we identified all nuclides emitting rays at the crack as Naturally Occurring Radioactive Materials, (NORM: K, Bi, Ac and so on) by in-situ -ray measurement. Radon is not easy to be collected and detected by its nature of noble gas. We have developed a convenient electrostatic collection method: after collection of the radon decay product (Po) using a Teflon sheet charged electrostatically, we have measured alpha rays and rays from this sheet. We concluded the leakage of radon from the soil caused a high counting-rate of alpha rays. The paper describes our survey works and identification procedures in detail.