Eu:LiCaAlF 6 Fiber-Coupled Detector Design for Neutron Monitoring in a Zero-Power Reactor

This study evaluates the neutron measurement and discrimination capabilities of a Eu:LiCaAlF6scintillator before and after coupling it to an optical fiber, and introduces a miniature Eu:LiCaAlF6fiber-coupled detector for reactor neutron measurement. Comprehensive Geant4 simulations were performed, and the results show that thinner scintillators effectively suppress high-energy gamma responses, thus improving the high n/γ discrimination capability. Experimental measurements were performed using a 0.8-mm-thick scintillator, both before and after its coupling to a 30-cm-long plastic optical fiber, in response to a252Cf neutron source and gamma sources. The detector exhibited a distinct peak response to thermal neutrons in both configurations, with an equivalent 1456 keV electron energy response. A miniature fiber-optic neutron detector was designed for monitoring the neutron flux in a zero-power research reactor. It featured a 0.6 mm × 0.6 mm × 0.6 mm Eu:LiCaAlF6scintillator coupled to a 1 m long quartz optical fiber with a 600 μm core diameter. The relative variation in neutron flux within the zero-power reactor was measured online during control rod movement. This measurement system was deemed to be adaptable for the measurement of thermal neutron flux up to 108n/cm2/s. Future research should focus on employing in-core extended optical fibers and detector arrays for internal, multi-point monitoring, with the aim of evaluating the system's long-term stability and reliability during continuous reactor operation to enable practical deployment.