Fabrication and testing of a 5-node micro-pocket fission detector array for real-time, spatial, iron-wire port neutron-flux monitoring

Highlights: •A flexible array of 5 MPFDs was fabricated and deployed within a flux wire port. •Neutron-induced pulses were observed on all MPFD channels. •Stable device operation was achieved with a 100 V applied bias. •Linear response to reactor power was observed on 4 of 5 detector channels. •Improvements to the MPFD design are recommended. -- Abstract: Micro-Pocket Fission Detectors (MPFDs) can be used to monitor a neutron flux within the core of a nuclear reactor. When assembled into an array, MPFDs can be used to simultaneously monitor the neutron flux at multiple locations within the reactor. One permutation of the MPFD is designed to be deployed into an iron wire flux port, typical for most research and commercial reactors. A single 5-node MPFD array was fabricated at deployed into a dry flux port within the central thimble of the Kansas State University TRIGA Mk. II research nuclear reactor. The sensitivity of each MPFD node at operating voltages of +50 V, +100 V, and +200 V was observed and an optimal operating voltage of +100 V was identified. No cross-talk was observed between instrument channels during real-time neutron flux measurement. Linear power tracking and real-time response to reactor power were both observed between 10 kWth and 100 kWth reactor power.