Gas Pressure Buildup in a Coated Fuel Particle of Deep Burn-High Temperature Reactors

The deep burn-high temperature reactor (DB-HTR) was conceived to convert the transuranic (TRU) radionuclides, recovered from spent light water reactor (LWR) fuel, into shorter-lived fission products (FPs). It can reduce the long-term storage requirements for the high-level waste generated from currently operating nuclear power plants. The DB-HTR fuel uses a tri-isotropic (TRISO) coated fuel particle (CFP) which consists of a kernel, low-density pyrocarbon as a buffer, inner high-density pyrocarbon (IPyC), silicon carbide (SiC), and outer high-density pyrocarbon (OPyC). The kernel produces free oxygen and various toxic fission gases during the heat generation through the fission of nuclear materials in it. CO gas is generated through the interaction of the free oxygen with carbon atoms of the inner region of the coating layers. The CO and fission gases gather in the void volume in the kernel and buffer of an intact TRISO CFP. The pressure buildup in the volume should be estimated since it is one of factors deteriorating CFP integrity. This study describes the gas pressure buildup in the void volume in a CFP of 450 and 600 MWth block-type DB-HTRs