Measurement of k_∞ and Relative Reaction Rates in an H₂O-Moderated UO₂-PuO₂ Particulate Fueled Lattice

The neutron multiplication factor, k_∞, and relative reaction rates have been measured at room temperature in the Physical Constants Testing Reactor (PCTR) for a water-moderated lattice fueled with Zircaloy-clad UO₂-PuO₂ fuel rods. The plutonium content in different sets of fuel rods ranged from 0.9 to 2.5 wt% PuO₂ in UO₂. These experiments provide neutronics data for uniform lattices of mixed-oxide fuels which contain plutonium oxide distributed throughout the uranium oxide as finite-sized particles. The PuO₂ particle sizes in different sets of fuel rods ranged between 0 and 328 µm in diameter. Knowledge of the effect that plutonium particle size has on neutron multiplication is important for the economic utilization of plutonium. An experiment-theory correlation provides a basis for assessing the adequacy of calculational techniques.