Study of possibility of clearance measurement for covered cables and control panels by detection simulation

Namekawa, Masakazu*; Shimada, Taro ; Takeda, Seiji 

Detector responses in the measurement of composite material change according to combination of measuring time, density deference, accumulated condition and radiation source position. It may impact clearance decision unlike measurement of target objects made from a single material such as metal scraps. And also, it is necessary to confirm that radionuclides such as Zn-65, Sb-125 activated in the covered cables are able to be detected in measurement system. In order to evaluate possibility of clearance measurement by the conventional method of measurement and evaluation, we constructed simulation models of measurement systems using plastic scintillation and portable Ge detectors, and simulation of detector response was carried out by PHITS code. Calculation results indicated that measurement of clearance levels of target nuclides is possible in measurement system of covered cables bundled with about 100kg. On the other hand, clearance judgement may be difficult in the case of measurements of control panels which have large housings without segmentation by using the portable Ge detector at once. Multiple measuring with changing position of the detector is required for the case.