Detecting Neutrons Outside of Reactor Shielding: Prospects for Stand-Off Reactor Monitoring

摘要

There is considerable interest in the nuclear safeguards community to develop instruments and techniques for the purposes of detecting undeclared nuclear material and activities. This paper discusses a potential option for detecting the establishment of nuclear fuel cycle activities from their process emanations, by large-area neutron detectors placed at 10 to 100 m stand-off distances outside reactor shielding. It is shown that with commercially available large area neutron detector technology, neutrons can be detected outside reactor shielding; their correlation with reactor power and changes in fissile isotopic composition of the reactor core are currently being investigated. The method promises to provide information complementary to existing reactor monitoring by detecting antineutrinos emitted by the reactor, also to monitor reactor power and changes in isotopic composition. The technique with neutron detection possesses some significant advantages, such as providing signal to background ratio in the detection count rate that can be orders of magnitude greater than is presently available with antineutrino detection. The required neutron detector technology is also considerably more compact and economical than current antineutrino detector implementations. The presentation will demonstrate the neutron detection method with data acquired in proximity to heavy water reactors in Canada.