Recent Results from a Test of Reactor Monitoring with a Cubic Meter Scale Antineutrino Detector

Lawrence Livermore National Laboratory and Sandia National Laboratories have jointly built, deployed and operated an antineutrino detector at the San Onofre Nuclear Generating Station (SONGS) Unit 2 reactor. The detector has been taking data since late 2003, with full instrumentation of 4 cells and 0.64 tons of target mass since August 2004. The overall aim of this research is to provide an additional bulk accountancy tool to the safeguards community, which complements the containment and surveillance and item accountancy techniques which now prevail in reactor safeguards regimes. The main goal of this deployment is to demonstrate that antineutrino detectors are relatively simple to build and operate, and that they can be used to monitor the power and fissile content of a nearby reactor core in real time, by measuring the flux and energy spectrum of antineutrinos emanating from the reactor. Here we present preliminary results related to power monitoring precision, and evidence for sensitivity to the core fissile content, using only the antineutrino signal. Our experience shows that antineutrino detectors can be operated for years at a time, with minimal intervention, in a self-calibrated mode, and can be non-intrusive to reactor operations. Initial results from this detector were presented in a 2004 INMM paper1. Here we present significant new data from the detector, taken over a one year period from summer 2005 to summer 2006, Cycle 13 of the SONGS Unit 2 reactor. This recent data set demonstrates that the antineutrino signal responds to changes in fissile content and can precisely monitor reactor power. It also shows that the detector can operate stably for a year or longer with minimal intervention and with no impact on reactor operations. These findings are key considerations for assessing the utility of the detector for safeguards regimes.