ＧＭサーベイメータを用いた直接測定法における低エネルギーβ線放出核種による表面汚染の検出について

概要

論文の詳細を見る
For a direct measurement method using a GM survey-meter, the detection efficiency and detection limit against surface contamination with nuclides emitting β-rays on a polyethylene-coated paper were examined. Three nuclides, 14C, 35S and 32P were used as a source. The detection efficiency against 14C, 35S and 32P at the place of 5.0 mm distance from the detection face of the survey-meter was approximately 1.4, 1.9 and 34.5%, respectively. Although the detection efficiency obtained for 32P was the same as the value showed in the instruction manual, that of 14C was smaller than that of the instruction manual. It is considered that such a difference in detection efficiency between 32P and 14C is ascribed to difference in source efficiency. Furthermore the detection limit against 14C, 35S and 32P at the distance of 5.0 mm was about 3.6, 2.6 and 0.2 Bq/cm2, respectively. Hence it appears that the direct measurement method using the GM survey-meter is useful to check the surface contamination with 14C or 35S in a controlled area since the surface contamination density limit in a controlled area is 40 Bq/cm2.