Description of new correlations and databases for fuel performance codes to be applied to Am bearing fuels

In this deliverable, we outline the correlations and data that have been transferred to models suitable for fuel performance codes (TRANSURANUS, GERMINAL) for the simulation of Am-bearing oxide fuels. This is based on the information provided in the open literature in addition to the results obtained in Work Package 4 of the PATRICIA project. The objective was to derive advanced laws for thermal mechanical properties, based on both experimental and lower-length data in order to improve the accuracy and physical basis of the fuel performance codes (FPCs) for safety analyses. The safety-relevant oxide fuel properties implemented include: (i) advanced models for the melting (solidus) temperature of Am-bearing fuels implemented in TRANSURANUS; (ii) state-of-the-art and advanced models for the thermal conductivity of Am-bearing fuels implemented in both the FPCs; (iii) heat capacity models for MOX fuels extended to account for the fuel Am content; and (iv) a more mechanistic model for oxide fuel creep in TRANSURANUS. The first two properties benefited from the developments in WP4 based on atomic-scale and CALPHAD simulations. For what concerns the cladding properties, dedicated correlations for the MYRRHA cladding steel (DIN 1.4970, of the 15-15Ti steels family) were implemented in TRANSURANUS and used for MYRRHA simulations. More precisely, the models considered target the thermal and irradiation-induced creep, void swelling and time-to-rupture, applicable to ranges relevant for the current MYRRHA core design. For what concerns thermo-physical properties of the LBE coolant, advanced correlations are also implemented in TRANSURANUS. On the one hand, the thermal conductivity, specific heat, density and viscosity correspond to the recommendations provided by the latest NEA Handbook. On the other hand, the heat transfer coefficient between cladding and coolant is modelled in TRANSURANUS via the Ushakov correlation as a standard. Other correlations suitable for LBE, from Subbotin and Kazimi Carelli, have also been implemented in the TRANSURANUS code for a sensitivity analysis. Finally, it should be mentioned that the modelling improvements of the SCIANTIX module, coupled with the TRANSURANUS and GERMINAL codes for a more mechanistic description of inert gas behaviour and fuel microstructure evolution, are outlined separately in the Deliverable 5.2.