For the conversion of high performance research reactors to low enrichment Uranium fuel, U-Mo alloy based fuels in monolithic form were proposed. These plate-type fuels consist of a high uranium density, low enrichment uranium (LEU) foil contained within a diffusion barrier, and encapsulated within a cladding. To benchmark this new design, effects of various geometrical and operational variables on irradiation performance have been evaluated. In this work, the effects of mechanical constraints on the thermo-mechanical behavior of a plate were studied. To evaluate these effects, a selected plate from RERTR-12 experiments (Plate L1P756) was simulated. Four distinct cases which represent four distinct welding conditions were considered. Evaluation of the stress-strain fields in the fuel elements revealed that mechanical constraints may impact the plate’s performance. These constraints include (a) inlet side, (b) outlet side, (c) both inlet and outlet sides; and finally, (d) entire long edges. Results of these cases were then compared with the ideal case. The peak stress-strain magnitudes, displacement, stress and strain profiles on the fuel elements are evaluated to make a comparative assessment. The results indicated that the cases with constraints on “inlet side only” and “outlet side only” yielded lower cladding strains compared with other cases. The difference on the displacement profiles on the fuel foil was not significant. Peak stresses on the foil did not change considerably. These results imply that the mechanical constraints effects peak cladding strains, while it does not cause significant effects on the fuel behavior.

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