Uranium Oxide Fuel Pellet Shape Optimization Of Numerical Simulation

This article puts forward some kinds of optimized models for the problemthat nuclear fuel rods are easy to split and have short lifespan when UO₂is inthe process of nuclear reaction. And these models are put forward from theaspect of shortening the radial distance. The article also use MSC.Marc tocarry out the pressure modeling process to confirm that pellet model meet thedemand that relative density is1after UO₂powder is tyrannized. And then, weuse ANSYS to direct numerical simulation of the process of nodulizing andprocessing of the pellets. We can arrive at the best model by comparing thedistribution of its temperature field, stress field and strain.By computational analysis, we can find that when nuclear fuel rods intraditional cylinder is heated in the temperature of1750℃, there will be smallarea in the core of the pellets with the temperature of20℃after8hours ofnodulizing, which means nodulizing is incomplete. However, the shallowsaucer-shaped pellets with a hole in the bottom and the pellets with a chamferin the junction of side face and back surface can reach the temperature ofapproximately800℃, which have a significantimprove as before. When theinternal heat q_v=1×10⁷Btu/h·ft³, and the temperature of the pellets’ corereaches2000℃,traditional cylinder UO₂nuclear fuel rod operates12hoursthe temperature of surface is just578.56℃.After improvement, temperature ofthe disc with shallow and the pellets can be1075.58℃and1078.26℃,respectively. And the operation time extends to14hours, optimization effect isobvious, through equivalent heat stress analysis about several pellet models.The thermal stress of the surface of traditional cylinder pellet is above158MPa. Beyond the breaking strength of UO₂ceramic material, this is150MPa.Then the surface of the pellet starts craze, and after the improvement, thermalstress of both the disc with shallow and the surface of pellet are in the scope,so the purpose of this optimization can be achieved and extend the service life of the pellet, which is significant to development of nuclear industy.