Weight values for MCNP calculations based on Recursive Monte-Carlo method

MCNP calculations for deep penetration (shielding) problems are challenging. For optimizing the calculation, weight window (WW) variance reduction techniques are used. The current MCNP weight window generator (WWG) has the limitation of producing zero weight parameters for regions located far from the source. To solve this, several adaptive methods are applied, and one of them is the reduced density method, which requires vast experience, more computational time, and multiple iterations to achieve an optimal set of weights. Therefore, the present study focuses on the development of optimal sets of weights based on the TRAWEI (RMC) code. To verify the performance of the developed program, two test cases of single shield material (heavy concrete and standard concrete) were created with the same cylindrical geometry. Three different simulations were made for each test case. For the heavy concrete case, the calculation efficiency using TRAWEI weights is significantly improved compared to other simulations (analog MCNP and MCNP-WWs). Similarly, for the standard concrete case, TRAWEI generated weights require one more iteration to achieve the optimal weights for the precise calculation. In short, it can be concluded that the TRAWEI weight window generator is user-friendly, can generate the optimal weight window values in a single run with minimal computational cost, and is a good choice for densely shielded geometries. The developed method significantly contributes to dosimetry calculations and can be used in future decommissioning studies. In the future, this program will be tested for real-case geometries.