Evaluation of γ-ray Effects on a β-ray Survey Meter with a Plastic Scintillation Sensor

The demand for radiation measuring instruments increased after the Fukushima Daiichi Nuclear Power Plant accident in 2011. Plastic scintillation survey meters have recently been developed to meet these needs as an alternative to the Geiger–Müller (GM) survey meters long used for detecting β-rays. Although manufacturers’ catalog data are available for plastic scintillation survey meters, there are few reports evaluating their in-situ performance, especially how γ-rays affect the plastic scintillation survey meters intended for β-ray detection. In this study, we experimentally evaluated the effect of γ-rays on plastic scintillation survey meters by comparing them with GM survey meters. We found that, when γ-rays other than those of low energy were measured with a plastic scintillation survey meter, the detection ratio compared to the NaI(Tl) scintillation survey meter exceeded 4%. The counts on the plastic scintillation survey meters were comparable to those on the GM survey meters. We concluded that if contamination is monitored using β-ray survey meters, it is necessary to evaluate the results of β-ray contamination measurements considering the effects of γ-rays by using in parallel γ-ray survey meters, such as NaI(Tl) scintillation survey meters. What are the main findings? • The effect of γ-rays in the plastic scintillation survey meters for β-rays is fundamentally the same as in the GM survey meters. • γ-ray counts in β-ray survey meters compared to the NaI(Tl) scintillation survey meter exceed 4% for the Na-22 and Ba-133 sources. What is the implication of the main finding? • The effect of γ-rays in the plastic scintillation survey meters compared to the GM survey meters is visualized. • The importance of using β-ray survey meters in conjunction with γ-ray meters to assess β-ray contamination was confirmed.