Relationships between Reactivity Changes, Buckling Changes, and Periods in a Heavy Water Reactor

Period-reactivity relationships were measured in the PDP, a large D₂O-moderated reactor fueled with natural uranium. When compared with calculated relationships based on various delayed neutron parameters, the measured relationships were found to correspond almost exactly to those predicted from the delayed neutron parameters measured by Keepin for fission neutrons and by Bernstein for photoneutrons. Satisfactory agreement was also observed between values of the migration area obtained from a measured reactivity-buckling relationship and those obtained as the sum of the separately measured values of the thermal diffusion area and the neutron age.