Analysis of thermal-hydraulic behavior in a fast reactor fuel subassembly with porous blockages

A single-phase transient subchannel analysis code ASFRE-III has been improved to assess the coolant thermal-hydraulic behavior in a large-scale wire-wrapped LMFR fuel pin bundle under local porous blockage conditions. A Porous blockage model and three-dimensional fuel-pin heat conduction model were incorporated in the code. Further, ASFRE-III was parallelized to put in practice the simulation of the actual-sized fuel subassembly. Code validation was made using out-of-pile experiment data in sodium with wire-wrapped pin bundles and agreement between experiment and calculation was good. ASFRE-III was applied to the analysis of a 217-pin bundle under various blockage conditions. Discussions were made on the influence of blockage characteristics, e.g., blockage formation, blockage porosity and heat conduction in a fuel pin, on the thermal hydraulics in the fuel pin bundle. 17 refs., 14 figs., 1 tab.