TRU Deep-Burn in MHR Fueled with Diluted Kernel TRISO

As an alternative to TRU transmutation in fast reactors based on repeated reprocessing of spent fuels, the deep-burn (DB) in graphite-moderated MHR (Modular Helium Reactor) is under investigation. In the DB concept, an ultra high burnup is pursued without costly repeated reprocessing and re-fabrication of spent TRU fuels. The spent fuel of DB-MHR is either fed synergistically into fast reactors or directly disposed of in a repository. In MHRs, a ceramic-coated particle fuel (TRISO) is used. A recent study on the deep-burn shows that the fuel burnup can be as high as 58% with a four-batch fuel management in a prismatic MHR core. Kim and Noh showed that the kernel size should be minimized to enhance the fuel burnup through reduced fuel self shielding effects. In this paper, a new kernel concept, a carbon-diluted kernel, is introduced to reduce the self shielding of the TRU fuel and the DB capability of an MHR core is evaluated with the MCCARD code