A 2-D CORRELATION TO EVALUATE FUEL-CLADDING GAP THERMAL CONDUCTANCE IN MIXED OXIDE FUEL ELEMENTS FOR SODIUM-COOLED FAST REACTORS

摘要

The paper defines a parameterization for thefuel-cladding gap thermal conductance in a SodiumCooled Fast Reactor. This collaboration took place withinthe EU-funded ESFR-SMART project.This requires use of predictive codes that have beenvalidated where possible against experimental data. Thisstudy relied on 7 fuel performance codes thus providingconfidence in the recommended correlation.A single pin model for both the inner and outer fuel wasbuilt. The fuel was burned for 2100 Effective Full PowerDays, with the axial power distribution varying over time.This paper presents a comparison between the codes’results and a 2-D correlation for the heat conductancewith respect to fuel burn-up and fuel rating. The fuel isbroken down into nodes with specific fuel rating andburn-up, leading to the gap conductance expressed as afunction of nodal fuel rating and burn-up. Data was thencompiled for all the nodes, for both fissile and fertileregions, for both inner and outer fuel for all 7 codes. A2D fit was applied to the data thus obtained.The results obtained show a general increase of heat conductance with fuel rating and burn-up, from 0.22 at 0 burn-up and 10kW. m~(-1) to 0.45 W. cm~(-2).K~(-1) at 0 burn-up and 50 kW. m~(-1) and to 1.00 W.cm~(-2).K~(-1) at 150 GWd.t~(-1) and 50 kW. m~(-1). Some spread between codes has been noted and appears to be consistent with the spread published earlier by several code developers.Sensitivity to various modelling assumptions is under investigation. This is aided by the use of numerous fuel performance codes which enables a wide ranging and thorough sensitivity analysis.