Comparison of deterministic and stochastic methods for external gamma dose rate calculation in the decommissioning of nuclear power plants

Highlights: • The selection of the best calculation code is important in radiation protection. • Broder's formula is a good choice for simple geometries with multilayer shields. • The differences between the VISIPLAN and MCNP is mainly caused by Build-up factor. • If the geometry is more complex, use a Monte Carlo code, for example MCNP. - Abstract: Calculations for individual scenarios are carried out for optimization of radiation protection, waste management, decommissioning planning, management of disposal facilities, and others. Comparative study of various calculation codes for different geometries with multilayer shields was performed. Reference geometries are models of the most frequently used waste packages in the decommissioning of nuclear power plants (NPP) in Slovakia. As representatives of deterministic calculation codes were chosen Visiplan, Microshield and Mercurad. Stochastic codes were represented by MCNP code. The impact of different build-up factor (BUF) selection in deterministic codes was evaluated. Experimental measurements with different multilayer shields were performed and compared to the results obtained by MCNP calculations. The percentage deviation between experiment and MCNP calculations was ±20% for every shielding configuration. Analysis of the differences between results was made. Recommendations for choosing of the most suitable calculation code for given application are formulated in this study.