Calculation of the antineutrino source term during CANDU reactor startup

The lack of charge and small mass of the antineutrino ensures an extremely low interaction probability with all matter, effectively making the particle impossible to shield. Since differing antineutrino energy spectra are produced by each fissionable isotope, the antineutrino flux will also change as a function of burn-up. Lawrence Livermore National Laboratory and Sandia National Laboratory are preparing a 4 cubic meter detector to be deployed at the CANDU reactor at Point Lepreau Generating Station in New Brunswick, Canada. The purpose of this research was to model a CANDU core for normal and atypical operation to analyze changes in antineutrino emission and explore the effectiveness of using antineutrino detectors at detecting these changes. A computational model was created using the TRITON module from the SCALE6.1 code package coupled with Python for a single bundle and full refueled core models. Dependence of the antineutrino rate on power and bundle replacement was analyzed, with a 10% change in power causing a 10% change in antineutrino rate, and the CANDU detector effectively measuring a 10% decrease in power within 9 h of collection time. Bundle refueling was shown to only slightly modify the antineutrino rate, requiring a target volume more than 20 times larger than the present detector to effectively identify the change due to the bundles refueled over a one week period. Diversion of 15% or more of the total amount of bundles can be effectively measured by the CANDU detector within a one month counting period.

► SCALE6.1 accurately simulates the irregular pin geometries in the CANDU fuel bundle.
► At typical antineutrino detector standoff distances, the CANDU core is a point source.
► A 10% change in reactor power causes a resulting 10% change in the antineutrino production rate.
► Typical CANDU refueling processes lead to only slight changes in the antineutrino production rate.
► A 4 m3 detector cannot detect changes in core composition from refueling operations.