The gamma dose rate analysis method for the maintenance of China initiative accelerator driven subcritical system based on the voxelized algorithm

Gamma dose rate analysis is the important issue for the maintenance of China initiative accelerator driven subcritical system (CiADS), which has direct impact on the nuclear radiation protection and the safe working environment for operators. However, the gamma radiation assessment in CiADS facility is the complex and challenge task, since there are a lot of complicated geometries with large amount of high order curve surfaces that are difficult to describe in the simulation process. Additionally, the shielding design in maintenance scenario has the requirement of high efficient calculation with acceptable accuracy. In this context, the point kernel method and the model simplification procedure by means of the voxelized model description have been adopted in the dose rate analysis for the purpose of obtaining the required flexible and diverse features, where the complex three dimensional geometries constructed by computer aided design (CAD) tools can be automatically converted to the approximate voxelized structure, and the radiation sources with arbitrary shapes are sampled based on the basic units in the conversion model. Furthermore, the CAD geometry optimization method has been verified in considering the volume deviation between the original CAD structure and the voxelized model. The feasibility and applicability of the dose rate analysis method have been tested in comparison with the FLUKA code, where all the numerical simulation results demonstrate that the proposed assessment method has the potential in meeting the design requirements during the maintenance of CiADS facility.