Real-Time Fiber Optic Neutron Spectrometer

Improved neutron dosimetry is needed to assure the safety of nuclear power plants. However, real-time spectrometers for measuring neutron dose at specific energy levels do not exist. Instead, the current state of the art relies on some type of installed neutron absorber, which must be physically removed and analyzed to obtain the energy-level specific dose. The removal process typically requires the reactor to be shut down and, therefore, is costly and performed only infrequently. If a real-time spectrometer could be constructed that allowed energy-level specific measurements, then model predictions could be verified, and a more accurate assessment of reactor vessel health could be made. This project will develop a real-time, fiber-optic neutron spectrometer that can discriminate between neutron energy levels. The spectrometer will be able to be used independently, or integrated with other high-temperature pressure/temperature sensors under development. Phase I will involve a basic study into the effects of neutrons of selected energies on optical material properties of interest. In particular, dosimeter performance and design requirements will be identified, materials will be selected, and radiation testing will be conducted to verify the ability to distinguish between neutron-material interactions at selected energy levels. Phase II will focus on the implementation of a stand-alone neutron spectrometer with improved energy resolution. Commercial Applications and Other Benefits as described by the awardee: The need for nuclear power is expected to increase as electric vehicles demand more power generation, and dependence on foreign oil and environmentally-destructive fuels become more politically undesirable. The real-time dosimeters should have application to existing and emerging nuclear reactors, particularly gas reactors and fast reactors where neutron energies are considerably higher than in light water reactors. These dosimeters will improve reactor safety through lifetime, structural health monitoring, and will reduce cost by eliminating the need for removal and analysis of installed dosimeters.