Transport theory calculations were used to determine the feasibility of monitoring the fuel loading to initial criticality of the Clinch River Breeder Reactor (CRBR) with a detector in a cavity outside the reactor vessel. Such monitoring of the CRBR with an ex-vessel detector will be different from monitoring of previous LMFBRs, where in-vessel detectors were used. The feasibility of ex-vessel monitoring will depend mainly on two criteria: (1) sensitivity - will there be enough counts to obtain adequate counting statistics; and (2) interpretability - will the count rate obtained during the initial fuel loading sequence be sufficient to determine the neutron multiplication or reactivity. Satisfying these criteria will assure that the reactor can be loaded safely to initial criticality. The sensitivity criterion can be satisfied by inserting an additional neutron source (one much more intense than the inherent neutron source of the fuel subassemblies) into the core center and using ex-vessel detectors with high sensitivity, such as multiple BF/sub 3/ counters mounted in a graphite moderator block. These calculations were used to determine the intensity of the additional source required to produce adequate counting rates at the ex-vessel detectors
