Effects of UMo irradiation creep on the thermo-mechanical behavior in monolithic UMo/Al fuel plates

The in-pile thermo-mechanical behavior in monolithic fuel plates is simulated by 3D FE (three-dimensional finite element) method, using different creep coefficients for UMo fuel foils. The obtained results indicate that the thickness increments of fuel foil can be deeply affected by the UMo creep coefficient. The obtained results with a UMo creep coefficient of 2000 x 10(-22) mm(3)/MPa can agree very well with the post-irradiation measurements for the thickness variation of U-10Mo fuel foil, if the creep behavior of Al alloy cladding is considered in the 3D FE simulation. The UMo creep coefficient is identified to be 1000 x 10(-22) mm(3)/MPa when the creep behavior of Al alloy cladding is not involved in the FE simulation. Both of these cases demonstrate that the creep coefficient is underestimated in the reference. The maximum Mises stresses in the cladding decrease remarkably with the UMo creep coefficient. With an increase of UMo creep coefficient from 10 x 10(-22) mm(3) /MPa to 2000 x 10(-22 )mm(3)/MPa, the first principal stresses in the fuel foil and the interfacial normal stresses decrease by about 91%. It is concluded that the creep coefficient for UMo foils is intensively related to the service life of UMo/Al fuel plates. The fabrication technique and element composition should be properly designed for UMo foils to acquire an optimized in-pile creep performance. (C) 2019 Elsevier B.V. All rights reserved.