Assessment of Design Safety Limits for Fuel Cladding Based on Benchmark Tests

The PFBR core, which is highly enriched, is very compact due to neutronic considerations. The gap provided for coolant flow is so less that deformation of the clad will disturb the coolable geometry, which may lead to severe damage to the core. If adjacent pins balloon at the same axial level (coherent ballooning) they may touch each other impeding a proper flow of the coolant. To make the reactor commercial, studies are being made to exploit the D9 material at high burn up, longer cycle life and high temperature operations. The Design Safety Limits (DSLs) for fuel clad are given based on rupture. It is necessary to experimentally investigate and confirm the available margin at all category events, and to know at what conditions, the strain within the clad will affect the coolable geometry. Out of pile tests have been conducted with single fuel pin at high temperature and high pressure, to study the material behavior, to quantify and evaluate the available margin for the PFBR clad tube under various category events. The experimental facility has been indigenously developed to simulate the various category events. High sensitivity X-ray radiography method is deployed to measure the deformation of the specimen.