Design Options of Control Rod for Low Enriched Uranium Fueled NIRR-1 Using Monte Carlo N-Particle Code

Design Options of Control Rod for Low Enriched Uranium Fueled NIRR-1 Using Monte Carlo N-Particle Code

NIRR-1 like other Commercial MNSRs has single control rod performing all safety functions. Feasibility studies have shown that UO₂ fuel enriched to 12.5% can be used for the conversion of MNSRs to LEU. However, this conversion would require modification to the single control rod to maintain same safety margins as the current HEU core. Consequently, the MCNP Code was used to design 3 variants of control rod for proposed LEU Core. Since the main objective of conversion is simply to propose replacing the existing HEU core, the control rods were designed to fit into the existing core configuration. Neutronics calculations for the third case indicate that the shutdown margin and safety reactivity factor are equal to or greater than the data for the current HEU core.