Numerical Simulation for Mechanical Behavior of U10Mo Monolithic Miniplates for Research and Test Reactors

Abstract

This article presents assessment of the mechanical behavior of U-10wt% Mo (U10Mo) alloy based monolithic fuel plates subject to irradiation. Monolithic, plate-type fuel is a new fuel form being developed for research and test reactors to achieve higher uranium densities within the reactor core to allow the use of low-enriched uranium fuel in high-performance reactors. Identification of the stress/strain characteristics is important for understanding the in-reactor performance of these plate-type fuels. For this work, three distinct cases were considered: (1) fabrication induced residual stresses (2) thermal cycling of fabricated plates; and finally (3) transient mechanical behavior under actual operating conditions. Because the temperatures approach the melting temperature of the cladding during the fabrication and thermal cycling, high temperature material properties were incorporated to improve the accuracy. Once residual stress fields due to fabrication process were identified, solution was used as initial state for the subsequent simulations. For thermal cycling simulation, elasto-plastic material model with thermal creep was constructed and residual stresses caused by the fabrication process were included. For in-service simulation, coupled fluid-thermal-structural interaction was considered.First, temperature field on the plates was calculated and this field was used to compute the thermal stresses. For time dependent mechanical behavior, thermal creep of cladding, volumetric swelling and fission induced creep of the fuel foil were considered. The analysis showed that the stresses evolve very rapidly in the reactor. While swelling of the foil increases the stress of the foil, irradiation induced creep causes stress relaxation.

Accelerated fission rate irradiation design, pre-irradiation characterization, and adaptation of conventional PIE methods for U-10Mo and U-17Mo

“…Constant mechanical values were inserted into existing BISON solid mechanics models, including the Young's modulus (84 GPa) (Rest et al, 2006) and Poisson ratio (.35) (Ozaltun et al, 2011). Although the Young's modulus used for BISON simulations is several gigapascals lower than measured for the actual preirradiated fuel (Section 4.1.3), the variation is not expected to change the results because of the mathematics relevant to the present simulations.…”

Deformation and damage of nuclear power station fuel elements under cyclic loading

“…6 These approaches have been used recently in different investigations. [7][8][9][10] The influence of pressure pulsation on creep-damage processes can be described by a simplified but very effective approach containing an average of the resulting strain growth and damage accumulation curves. For the case of cyclic variation of stress, the approach that averages the resulting creep strain curves has been used.…”

Evaluation of U10Mo Fuel Plate Irradiation Behavior via Numerical and Experimental Benchmarking

“…A non-linear coupled thermal-mechanical model was developed using C3D8RT elements, consistent with previous modeling techniques of fuel mini-plates [24][25][26]. Dimensions of the miniplate are shown in in Fig.…”