Description
Antineutrinos are an unavoidable byproduct of the fission process. The kton-scale KamLAND experiment has demonstrated the capability to detect reactor antineutrinos at few-hundred-km range. But to detect or rule out the existence of a single small reactor over many km for nonproliferation reasons requires a much larger detector. However, if the detector is so large that a considerable fraction of photons generated by particle interactions are absorbed before reaching a light sensor, it becomes impractical to construct. Gadolinium-doped water-Cherenkov detection medium has been proposed for very large reactor monitoring detectors. Even though Cherenkov emission produces relatively few photons per unit of deposited energy, the high optical transparency of Gd-doped water makes it promising for the largest of far-field detectors. Using a detailed Monte Carlo simulation, we estimate the reactor discovery potential of large-volume Gd-doped water-Cherenkov detectors for nuclear nonproliferation applications. We include realistic background models for the worldwide reactor flux, geo-neutrinos, cosmogenic fast neutrons, and detector-associated backgrounds in the simulation. We determine the dwell-time required to detect a small 50-MWt reactor at a variety of stand-off distances, as a function of detector size. We highlight that at present, PMT dark rate and event reconstruction algorithms are the limiting factors to extending reactor discovery and exclusion applications beyond ~50-kt fiducial mass.
LLNL-ABS-832009. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
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