Background Radiation Studies for Future, above Ground Antineutrino Detectors

We will describe an assembly of radiation detectors that quantifies the gamma, muon, and fast and thermal neutron fluxes present at potential above ground antineutrino detector sites. Antineutrino detectors show great promise for reactor safeguards applications, due to their ability to monitor thermal power and/or fissile content. One of the major technical challenges that this safeguard application faces is the ability to distinguish signals from antineutrinos originating in a reactor core from noise due to background created by terrestrial and cosmogenic radiation. To date, antineutrino experiments have increased the signal to noise in their detectors by surrounding the experiments with significant shielding and placing them underground. For the safeguards agency, this is less than optimal, as it increases the overall size of the device and limits the range of possible deployment locations. Placing reactor monitoring antineutrino detectors at, or near, the surface would greatly increase the range of possible deployment locations. In order to investigate designs that would allow this, we must understand the backgrounds found above ground that can mimic the antineutrino signal so that these can be easily identified, separated, and subtracted rather than shielded. The design, construction, calibration, and results from the deployment of this background measurement system at a variety of sites will be presented.