Citation:
G. Long, M. Watson, M. Ruch, “Applying Normalization Methods to Advanced Experimental Fuel Counter Measurements for Fissile Mass Quantification in Unirradiated Fuel”, INMM25: Advancing Nuclear Materials Management for a Safer Tomorrow, August 24–28, 2025. Washington, DC.
Abstract:
The Advanced Experimental Fuel Counter (AEFC) is a nondestructive assay instrument developed for performing neutron coincidence counting measurements of used research reactor fuel assemblies for fissile mass quantification. Previous AEFC deployments have resulted in the development and validation of total (Singles) and correlated (Doubles) neutron count rate calibration curves for specific fuel assembly geometries; however, due to the AEFC’s sensitivity to each campaign’s operational conditions, these calibration curves are only directly applicable to AEFC measurements of fuel assemblies with those specific geometries. Due to a lack of well-characterized used fuel assemblies available to serve as calibration standards, it would be advantageous to develop a technique that extends the use of previously developed and validated calibration curves to different fuel geometries. A new normalization technique was developed to correct measurements of a generalized fuel assembly to reflect the operational conditions in which previous AEFC calibration curves were developed. Our team conducted a series of AEFC measurements at Los Alamos National Laboratory on a set of fresh, low enriched, pin-type fuel assemblies containing between 25 and 350 grams of fissile mass. Here we discuss the results of applying the generalized normalization method to these fresh fuel assembly measurements such that their fissile mass could be estimated using a calibration curve developed for plate-type fuels. The fissile mass estimates for each fuel assembly were found to be in agreement with the known fissile mass content within estimated total (stochastic and systematic) uncertainties when applying the calibration curves to the normalized neutron Doubles rates. Applying the calibration curves to normalized measurements of unirradiated fuel serves as a step towards generalizing the prediction of fissile mass from used fuel measurements. This could extend the deployment capabilities of the AEFC to new facilities without the need to complete separate measurement campaigns for calibration curve development.