The RBMK-1500 spent nuclear fuel (SNF) composition determine the radiation characteristics of the CONSTOR and CASTOR containers, where SNF from Ignalina NPP (Lithuania) is temporarily stored now. The extension of containers storage time depends on the knowledge of the characteristics of SNF and resulting dose rates. The fuel containers safety assessment can be performed using powerful modelling tools. Modelling of nuclide composition and it axial distribution along the fuel channel is done using the Monteburns code systems. MCNP5 code was used for the evaluation of radiation shielding and the surface dose rate of the CASTOR cask taking into account the heterogeneity of the different burnup of SNF assemblies’ distribution. The simulation results confirm that neutron flux distribution is extremely sensitive to the fuel burnup and influence the neutron dose rate calculation results. The modelling results are compared with existing experimental data of the representative container leading to satisfactory agreement. This result proves the validation of calculation methodology for the radiation shielding safety assessment of CASTOR and similar containers used for the storage of RBMK-1500 SNF. |
