ThO2-Based Fuels For PHWRs - Fabrication Characterization and Test Irradiation'

Abstract

A research and development programme covering fabrication, property evaluation and irradiation-testing of ThO₂-UO₂ and ThO₂-PuO₂ fuels for PHWR is being pursued since the last five years in BARC, Bombay. The conventional "powder-pellet" route using MgO or NbzOa dopant is found to produce high density (≥96% T.D.) pellets at relatively low sintering temperatures (≤1773K)- Thermal conductivity and hot hardness data have been generated for these pellets, A 6-pin cluster containing 5 pins of zircaloy 2 clad ThO₂-4%PuO₂ fuel has been successfully irradiated to ~18 MWd/kg in CIRUS reactor. "Pellet-impregnation" technique has been explored for preparation of ThO₂-UO₂ (≤2% U) pellets, Sol-gel microsphere pelletisation (SGMP) process, adapting the external gelation of thorium (EGT) route of KFA, FRG for preparation of gel microspheres from heavy metal nitrate solutions, has been developed for production of high density ThO₂-UO₂ and ThO₂-CeO₂ (Ce for simulation of Pu) pellets with improved microstructure.