Development of a practical conversion factor for evaluating radioactivity in mixed metal and plastic clearance objects.

In clearance measurements involving a single material type, a conversion factor was applied to convert measurement results to activity based on an assumed uniform density. However, this factor has been found to underestimate activity in material mixtures. In this study, we proposed a method to identify the location with the lowest detection sensitivity (minimum location) in a mixture and evaluated its applicability to the conversion factor.

Influence of conversion factors on the radioactivity evaluation of clearance objects consisting of several materials.

Control panel waste generated from nuclear power plants is a new candidate for clearance under Japan's amended regulations. In the radioactivity evaluation, a simplified conversion factor for density and source location conditions has been used, assuming that it applies to unmixed materials such as metals. To investigate its applicability to control panels consisting of metal and organic materials, we examined the application of the conventional conversion factor by simulations of radiation measurements for a point source in a control panel.

Path-Planning System for Radioisotope Identification Devices Using 4π Gamma Imaging Based on Random Forest Analysis.

We developed a path-planning system for radiation source identification devices using 4π gamma imaging. The estimated source location and activity were calculated by an integrated simulation model by using 4π gamma images at multiple measurement positions. Using these calculated values, a prediction model to estimate the probability of identification at the next measurement position was created by via random forest analysis.

Evaluation of the detection limit of net count in peak for the energy spectrum of CZT detector.

Pulse shape processing techniques have been used to improve the energy spectrum of the cadmium zinc telluride (CZT) detector, however, quantitative evaluation of the improvement, to determine whether it is acceptable to the related stakeholders, is required. In this study, the detection limit of net count in the full-energy absorption peak according to ISO 11929-1:2019 was selected to quantitatively evaluate the improvement of the characteristics of net count in the peak in the energy spectrum.