Characteristics and verification of a car-borne survey system for dose rates in air: KURAMA-II

The car-borne survey system KURAMA-II, developed by the Kyoto University Research Reactor Institute, has been used for air dose rate mapping after the Fukushima Dai-ichi Nuclear Power Plant accident. KURAMA-II consists of a CsI(Tl) scintillation detector, a GPS device, and a control device for data processing. The dose rates monitored by KURAMA-II are based on the G(E) function (spectrum-dose conversion operator), which can precisely calculate dose rates from measured pulse-height distribution even if the energy spectrum changes significantly. The characteristics of KURAMA-II have been investigated with particular consideration to the reliability of the calculated G(E) function, dose rate dependence, statistical fluctuation, angular dependence, and energy dependence. The results indicate that 100 units of KURAMA-II systems have acceptable quality for mass monitoring of dose rates in the environment. - Highlights: • KURAMA-II is a car-borne survey system developed by Kyoto University. • A spectrum-dose conversion operator for KURAMA-II was calculated and examined. • We examined the radiation characteristics of KURAMA-II such as energy dependence. • KURAMA-II has acceptable quality for environmental mass dose rate monitoring