Tritium Production in Secondary Neutron Sources in Pressurized Water Reactors

Currently there are large uncertainties associated with the source of tritium in a Pressurized Water Reactor (PWR) Reactor Coolant System (RCS). The measured amount of tritium in the coolant cannot be separated out empirically into its individual sources. Therefore, all sources of tritium in the RCS of a PWR must be understood theoretically. One potential source of tritium in the RCS is due to tritium production in secondary sources. Neutron sources provide a flux of neutrons that are used to support reactor startup. Primary startup neutron source rods made of ²⁵²Cf are inserted into the reactor during the first cycle of a new nuclear reactor. The primary neutron sources are used to produce enough neutrons through spontaneous fission to create a sufficient neutron flux to be seen by the ex-core neutron detectors and facilitate reactor startup. Antimony-Beryllium secondary startup neutron sources are also inserted in the first reactor cycle to provide a neutron source for startups in future cycles. The Beryllium in the secondary sources is a source of tritium when irradiated in a neutron flux. This paper will discuss tritium produced within the secondary sources.