Real-Time Fiber Optic Neutron Spectrometer

Advanced nuclear reactor designs have been proposed for the efficient production of electricity and hydrogen, in order to meet future energy needs. These systems will require improved neutron sensors for adequate design and subcomponent evaluation, and for safe reactor operation. These new sensors must outperform present fission chamber detectors and wire dosimetry, with higher signal-to-noise ratios and faster response times. This project will develop fiber-optic sensors and interrogation systems for the reliable real-time monitoring of neutron flux, as well as fluence and energy distribution, in multiple locations near or inside the reactor core. Phase I demonstrated the feasibility of a fiber-optic neutron spectrometer. Combinations of four sensor types were identified, each with a unique response to neutron flux in two energy ranges. The first type showed very high sensitivity to thermal neutrons with no sign of saturation or reduced sensitivity at fluence levels up to 2.56 x1017 n/cm2. In Phase II, neutron probes with improved energy resolution will be developed for high-temperature operation. A system for rapidly analyzing and displaying neutron probe information will be tested in a research nuclear reactor. Commercial Applications and Other Benefits as described by the awardee: Miniature fiber-optic neutron probes could be distributed widely within nuclear reactors to help ensure uniform fuel depletion. The probes could help validate computer models for activities, such as control rod rotations, which can quickly alter neutron intensities and energies. To minimize clean-up costs of aging nuclear reactors, a network of these neutron probes could provide early warning of fast neutron leaks. Finally, neutron spectrometers could be used to more accurately monitor structural neutron damage and predict embrittlement.