Development of innovative neutron and gamma calculation schemes – A new pathway for generating MCNP geometry.

Within Framatome DTIPLN-F team, MCNP 5 is used over a large spectrum of application in radiation protection, particularly in cases where statistical convergence is challenging. ADVANTG (code using the CADIS method) is used for speeding up the calculations. MCNP 6.2 offers a new feature to describe geometries via unstructured meshes. This new pathway could simplify the work consisting of preparating the MCNP geometry decks, but the use of ADVANTG on such geometries is currently impossible. By subscribing to R&D efforts to improve calculation tools within the team, the mission consisted in the development of a Python library: RPTK, allowing in particular the use of ADVANTG as a technique for reducing the variance on MCNP 6.2 calculation models using unstructured meshes. The study of unstructured meshes format in compliance with MCNP 6.2 syntax enabled the creation of a tool for the writing of input geometry datasets. Studies via sensitivity analyses were then carried to set the recommendation uses for this tool, eventually validated. The development and further use of a convergence method for MCNP 6.2 transport calculation using unstructured meshes was put under test successfully for the calculation of the distributions of neutron fluxes on the vessel internals of a CP0 reactor design (Fessenheim). Thanks to this work, the RPTK module was eventually put under production by the end of 2019, allowing engineers to use this new pathway to perform MCNP propagation analyses.