Year
2017
Abstract
A novel nondestructive assay (NDA) instrument has been designed by a team at LosAlamos National Laboratory (LANL) which utilizes the differential die-away (DDA) technique toassay a spent fuel assembly (SFA). The DDA instrument incorporates a deuterium-tritium (DT)neutron generator in a housing with 12 He-3 detectors which surround the SFA being measured.This instrument was developed through the Spent Fuel NDA project as part of an effort to achievethe following technical goals more easily and efficiently than in the past: (1) verify the initialenrichment, burnup, and cooling time of facility declaration; (2) detect the diversion orreplacement of pins, (3) estimate the plutonium mass, (4) estimate decay heat, and (5) determinethe reactivity of spent fuel assemblies. This paper will include an overview of the design of theDDA instrument as well as some initial results from simulations, calibration experiments, andfresh fuel measurements performed at LANL.A series of tests have been performed utilizing the DDA instrument to measure fresh fuelassembliesin water to simulate the environmental conditions of a cooling pond at a nuclear facility.These tests involved assaying a pressurized water reactor (PWR)-like assembly with multipleconfigurations of fuel rods containing depleted uranium (DU), low enriched uranium (LEU), andLEU with burnable poisons (Gd). The different configurations provide varying enrichments andasymmetries. The tests illustrate the capabilities of the DDA instrument as well as help validatethe models used in its design.