This study performs a comprehensive comparative neutronic analysis of uranium nitride (UN) and uranium monocarbide (UC) as high-density, high-thermal-conductivity, accident-tolerant fuel candidates against conventional uranium dioxide (UO2) fuel for the VVER-1200 reactor, using OpenMC Monte Carlo simulations with ENDF/B-VIII.1 nuclear data. A detailed model was developed, accounting for varying fuel assembly enrichments and burnable absorber configurations. The analysis encompassed the burnup-induced fission product, including uranium and plutonium actinides and neutron poisons. In addition, the study investigated the reactivity response to key operational parameters such as fuel and moderator temperatures, boron concentration, and void fraction, and evaluated the key fission product inventories. The results indicate that UN and UC achieve extended fuel cycle lengths and enhanced 239Pu breeding compared to UO2, due to their superior heavy metal density and thermal conductivity. While these advanced fuels present slightly higher concentrations of neutron poisons such as 135Xe and 149Sm due to increased fission rates, they maintain favorable negative reactivity coefficients across varying fuel temperatures, moderator temperatures, and void fractions, maintaining a comparable radiological burden. Overall, UN and UC present promising neutronic and safety characteristics for the VVER-1200, contributing to improved safety margins and fuel cycle economics.
Al-Lawdhaeai et al. (Thu,) studied this question.