Size Effects on Thermo-Mechanical Performance of U-10Mo Monolithic Fuel Plates

Abstract

Monolithic fuel is a fuel form that is considered for the conversion of high performance research reactors. This plate-type fuel consists of a high density U-Mo fuel in monolithic form that is sandwiched between zirconium diffusion barriers, and encapsulated in an aluminum cladding. To date, large number of plates have been irradiated with satisfactory perforamce. The program is now moving into the qualification phase, a predecessor to the timely conversion of the target reactors. It must be shown that the fuel system meets the safety standards and performs well in reactor. The requirement to satisfactory irradiation performance under normal operating conditions is primarily demonstrated by a successful testing. Since each reactor employs distinct fuel plate geometries for various consideration with unique plate design features and attributes, a single “generic” plate geometry capturing all of the extremities is not achievable. Furthermore, testing all these geometric and irradiation parameters on a large size plate is not practical. Therefore, a smaller, “down-scaled” versions of fuel plates, are often employed for experimental purposes. This limitation consequently requires much more cautious performance evaluations, as thermal and mechanical response of a plate with certain geometry may not be representative for a plate with a different geometry. To investigate if plate size has any effects on irradiation performance, the plates with various geometric dimensions were parametrically evaluated. In particular, length and width of the plates were varied between the bounding values. Temperature, deformation, stress values were comparatively evaluated. The results have indicated that effects of geometric ratios and plate size variations in length and width directions are insignificant. However, wider plates could become more prone to a warping-type deformation, if there are nonlinearities.