Reactor Background Measurements at HFIR in Support of the PROSPECT-II Experiment*

Nuclear reactors are the brightest man-made source of neutrinos and have been actively studied in recent decades to investigate neutrino oscillations and further our understanding of the underlying decay processes in a fission reactor. The High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory is an 85 MW highly enriched Uranium reactor with a compact core that is ideal for studying reactor antineutrinos. The Precision Oscillation and Spectrum (PROSPECT) experiment, a ton scale liquid scintillator measurement of the antineutrino spectrum at HFIR, was designed to test for short baseline oscillations. A proposed upgrade to the experiment, PROSPECT-II, would operate at the same HFIR location. This talk gives an overview of background measurements made this year at HFIR to better understand the directionality of the reactor correlated gamma backgrounds in the PROSPECT location at the experimental hall. Also detailed are measurements made in a well shielded low background portion of the experiment hall in order to test the feasibility of future neutrino experiments.