Mobile radiation measurement system by multiple small gamma-ray detectors for radioisotope detection and identification supporting responders in the field of nuclear detection and nuclear security

核検知と核セキュリティの現場対応者を支援する放射性核種の検出と核種判定のための複数の小型ガンマ線検出器による携帯型放射線測定システム

木村 祥紀  ; 山口 知輝 

Kimura, Yoshiki; Yamaguchi, Tomoki

Rapid and precise detection or identification of artificial radioisotopes is one of the challenging issues in the field of nuclear detection and nuclear security. Although many handheld instruments capable of automated radioisotope detection and identification using small gamma-ray detectors have been recently employed in the field of nuclear security, the performance of such instruments is suffered from the limitation on cost of their detectors in many cases due to limited efficiency or limited energy resolution of the small size detectors. In this paper, a mobile radiation measurement system using multiple small gamma-ray detectors for radioisotope detection and identification has been proposed. The performance of the proposed mobile system for radioisotope identification has been tested for measured gamma-ray spectra of artificial radioisotopes and nuclear materials by CZT detector and CsI(Tl) detector. By analyzing the combined spectrum to be output by the proposed system, significant improvements in the minimum detection time for peaks from radioisotopes and lower detection limits for nuclear materials have been confirmed, comparing to the spectra measured by individual detectors. The authors have also discussed the optimization of detector combinations in terms of detector cost and improvement of sensitivity performance by performing simulations for several types of gamma-ray detectors.