Title: Monitoring of Reactors for IAEA and other Reactor Safeguards Regimes

Abstract: Reactor antineutrino detection has matured to the point where it is feasible to stably monitor plutonium content and reactor power using a high statistics (hundreds or thousands of counts per day) cubic meter scale antineutrino detector at a standoff of a few tens of meters. Our Lawrence Livermore National Laboratory/Sandia National Laboratories collaboration has deployed a detector to demonstrate this capability at a 3.4 GWt pressurized water reactor in Southern California, operating 25 meters from the core center, and acquiring data over an approximate one year period. Such monitoring may be useful for nonintrusively tracking power output and plutonium buildup in nuclear reactors, providing the earliest possible measurement of the amount of plutonium in the reactor core. We present our antineutrino event sample, and show that the fast short-term changes and slow long term changes in antineutrino rate are respectively consistent with known changes in reactor power through outages and with the expected long-term systematic decline in rate induced by ingrowth of plutonium as the reactor proceeds through its cycle. We estimate the attainable precision of the method, and discuss the benefits this technology may have for the International Atomic Energy Agency (IAEA) safeguards regime.