SPECTRAL SHIFT CONTROL REACTOR BASIC PHYSICS PROGRAM. EXPONENTIAL EXPERIMENTS AT ELEVATED TEMPERATURES ON LATTICES MODERATED BY D$sub 2$O-H$sub 2$O MIXTURES

Abstract

Summarized here are the results of exponential experiments conducted at elevated temperatures on rod lattices of slightly-enriched UO2 moderated by D2O-H2O mixtures. The fuel rods, 4%-enriched UO2 swaged in stainless steel, were 0.476-inch OD by 0. 016-inch wall. The non-moderator-to-moderator volume ratio was 1. 006. The two moderator compositions studied were light water {0% DjO) and a D2O-H2O mixture containing 81.5 mole % D2O. The experimental facility and techniques are described. Material buckling values derived from radial and axial flux measurements are summarized below. 0% D2O

Spectral Shift Control Reactor Basic Physics Program: Measurement and Analysis of Uniform Lattices of Slightly Enriched UO₂ Moderated by D₂O-H₂O Mixtures

“…Since this limit was 76.5% for the 4.02%-enriched fuel at M/W = 1.0, the range was extended to about 90% by including several exponential experments . Boric acid was added to the moderator in several of the crit- 4,5 ical assemblies to permit some separation of k and leakage-dependent CO properties.…”

Neutron absorption profile in a reactor moderated by different mixtures of light and heavy waters

“…Earlier studies of the mixed heavy/light water moderator of nuclear reactors showed that the neutron spectrum in a reactor is hardened as the percentage of heavy water in its moderator increases (Wehmeyer et al, 1962;Barrett et al, 1962;Tochihara et al, 1998;Nagy et al, 2014). An earlier work of the authors (Nagy et al, 2014) on the neutronic behavior of a nuclear reactor moderated by different mixtures of heavy/light waters showed that the total mass of control rods needed to attain criticality in reactor did not linearly decrease with increase of the heavy water percentage in moderator.…”