Abstract: Apparatus comprising a seal connector is disclosed for sealingly connecting flow channels in the core support plate with flow channels in fuel assemblies for use in a spectral shift pressurized water nuclear reactor. Spectral shift is obtained by displacing a portion of the light water in the core with deuterium oxide or a combination of deuterium oxide and light water or various gases such as helium during the initial state of reactor operation to harden the nuclear spectrum and thereby reduce excess reactivity and increase the production of fissile materials. The seal connectors provide a sealed flow channel for introducing the deuterium oxide into the core during the early stages of reactor operation and for reintroducing the light water into the core during the later stages of reactor operation.

Abstract: Apparatus is disclosed for introducing a low neutron moderating fluid into the reactor vessel of a spectral shift pressurized water nuclear reactor and for distributing the moderating fluid through the lower core support plate into the fuel assemblies in the core.