PDP MEASUREMENTS OF COOLANT VOID REACTIVITY COEFFICIENTS

摘要

Measurements in the Process Development Pile (PDP) determined the effect on reactivity of removing all D20 coolant from pressure tube fuel assemblies consisting of four concentric uranium metal tubes ranging in outer diameter from 1.06 to 3.08 in. and immersed in D20 moderator. At a triangular lattice pitch of 9.33 in. between the centers of the fuel assemblies, the measured increase in the multiplication constant of an infinite lattice was 2.8％. This result confirmed earlier calculations and exponential experiments which indicated that this type lattice of nested uranium metal tubes would be unstable in a boiling-D20-cooled power reactor.