Development and evaluation of a list mode neutron coincidence collar for spatial response measurements of fresh fuel assemblies

Development of a Neutron List Mode Collar (LMCL) and a List Mode Response Matrix Analysis Concept

“…Simulation results show spatial variation of the neutron count rates from fresh LEU fuel assemblies and indicate that this method could be used for change detection. Spatial response was also empirically demonstrated using the new collar and is summarized here and published in full in a separate journal article [3].…”

“…The prevalent neutron counting systems are composed of multiple 3 He detectors coupled to a series of power and signal processing electronics (i.e., power supply, preamplifier/amplifier/discriminator board, and derandomizer board housed in an electronics junction box), which in turn supplies neutron pulse train data to a shift register. The shift register processes the pulse data and, when combined with software, reports the total detected neutron counts and neutron coincidence rates.…”

“…The shift register processes the pulse data and, when combined with software, reports the total detected neutron counts and neutron coincidence rates. Currently, only a processed report of the combined raw data over all 3 He detectors, in terms of the neutron counting rate (i.e., singles and doubles), is reported from the shift register. In this work, the model JCC-71 Neutron Coincidence Collar detector was upgraded by retrofitting this standard uranium neutron collar detector with new electronics that enable list mode data acquisition.…”

“…Traditional neutron counting electronics for IAEA NDA neutron counting systems employ preamplifier-shaper networks that output transistortransistor logic (TTL) pulses in response to a detected neutron event. A typical counting channel comprises several 3 He gas-filled proportional counters that are grouped together and serviced by a single preamplifier. The logical outputs of all the amplifiers are summed to create a single pulse train for the system.…”

“…. Measured doubles count rate (doubles per second) as a function of channel number (i.e., the measured doubles count rate response across all 18 3 He detector channels for a 252 Cf source positioned near detector 3 [1].…”