Uranium Nitride as LWR TRISO Fuel: Thermodynamic Modeling of U-C-N and Thermomechanics
A new concept for light water reactor (LWR) nuclear fuel has recently been proposed that utilizes pellets of tristructural isotropic (TRISO) fuel particles embedded in a SiC or zirconium alloy matrix, replacing sintered urania pellets. The fuel is considered significantly more accident tolerant than urania as the SiC matrix or coated/protected zirconium alloy and TRISO particles would be highly resistant to oxidation and fission product release under beyond-design-basis accident conditions. As is well understood, failed fuel rods release gaseous and volatile fission products, and that is greatly exacerbated as urania oxidizes from UO 2+x to higher oxidations states in failed fuel pin with resulting expansion, loss of integrity, and significant further release of fission products.