Total Plutonium Content Determination in Pressurized-Water Reactor Spent Fuel with the Differential Die-Away Self-Interrogation Instrument

摘要

The Differential Die-away Self-Interrogation (DDSI) technique for nondestructive spent fuel assay is studied as a part of the Next Generation Safeguards Initiative project. DDSI is a passive neutron coincidence counting technique that utilizes neutrons primarily from spontaneous fission in an assayed spent fuel assembly (SFA) to preferentially interrogate its fissile material content. Previously, we have demonstrated by means of high fidelity neutron transport simulations the ability of the DDSI instrument to evaluate SFA multiplication with relatively high accuracy. Applying a recently developed concept that correlates SFA multiplication and passive neutron count rate with total plutonium content in the SFA and first tested in simulation space with the differential die-away instrument, we also demonstrate in this paper that with the DDSI instrument the total elemental plutonium content can be determined with a similarly high accuracy. The results are tested against 44 simulated SFAs from Spent Fuel Library 2a with varying initial enrichment, burnup, and cooling time. Total Pu content is determined with a standard deviation of 2.1%, discounting possible real life measurement errors, with respect to its true content as defined in the simulation input files.