Determination of Parameters for an Equation to Obtain Natural Background Radiation Using KURAMA-II Loaded with C12137-01 CsI(Tl) Detector

Abstract

We measured count rates and air dose rates at 11 measurement points little affected by the influ ence of the Fukushima Dai-ichi nuclear power plant accident to obtain parameters for a background equation applying KURAMA - II loaded with the high sensitivity CsI （ Tl ） detector, C12137 - 01. It was found that the sensitivity of KURAMA - II loaded with C12137 - 01 was about 10 times or more for background measurement, compared with KURAMA - II loaded with the standard CsI （ Tl ） detector, C12137. The background equation for the energy range of 1400 - 2000 keV was determined to be y （ µSv / h ）＝ 0.062 x （ cps ） . We evaluated background air dose rates using KURAMA - II loaded with C12137 - 01 for 71 municipalities and compared them with the results of a previous study of using KURAMA - II loaded with C12137. Evaluated background air dose rates in this study were almost equal to those in the previous study. We confirmed that the background equation evaluated in this study was applicable for KURAMA - II loaded with C12137 - 01.