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

Tsuda, Shuichi  ; Yoshida, Tadayoshi ; Tsutsumi, Masahiro; Saito, Kimiaki  

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 Daiichi Nuclear Power Plant accident. The KURAMA-II consists of a CsI(Tl) scintillation detector, a GPS device, and a control device for data processing. The dose rates monitored by the KURAMA-II are based on the G(E) function (spectrum-dose conversion operator), which can precisely calculate dose rate from the measured pulse-height distribution even if the energy spectrum changes significantly. The characteristics of the 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 dose rates in the environment.