Axial and azimuthal gamma scanning of nuclear fuel - implications for spent fuel characterization

• A project to research the application of non-destructive assay (NDA) to spent fuel assemblies is underway among a team comprised of the European Commission, DG Energy, Directorate Nuclear Safeguards; the Swedish Nuclear Fuel and Waste Management Company; Uppsala University, The University of Michigan, Los Alamos National Laboratory, Lawrence Livermore National Laboratory and Oak Ridge National Laboratory that collaboratively are advancing some of the goals of the Next Generation Safeguards Initiative’s Spent Fuel (NGSI-SF) Project. The NGSI–SF team is working to achieve the following technical goals more easily and efficiently using nondestructive assay measurements of spent fuel assemblies in order to improve both international safeguards and repository safety: (1) verify the initial enrichment, burnup, and cooling time of facility declaration; (2) detect the diversion or replacement of pins, (3) estimate the plutonium mass, (4) estimate the decay heat, and (5) determine the reactivity of spent fuel assemblies. The measured neutron, gamma-ray and heat signatures from spent fuel assemblies, as well as simulations, will be combined in advancement of the technical goals.This current study focuses primarily on the application of time stamped list mode data acquisition applied in the context of a fixed collimator that allowed a thin axial portion of the fuel to be observed as the fuel assembly moved vertically past the collimator. Measurements were performed at the Central Interim Storage Facility for Spent Nuclear Fuel (which is abbreviated using the Swedish acronym: Clab) in Sweden, in 2013 and 2014. In total, 50 spent nuclear fuel assemblies were measured in detail, 25 BWR and 25 PWR assemblies.In this context, time stamped list mode data acquisition have not previously been used for gamma-ray spectroscopy measurements of used nuclear fuel measurements. We compare it to the more typical fixed-axial location pulse height analysis approach. The flexibility of analyzing data from time stamped list mode measurements enables research into questions of how beneficial axially resolved information is for each of the varied research goals; in particular the current research is an initial step toward comparing the benefit of several fixed axial measurements vs. scanning an entire assembly.

Ämnesord

NATURVETENSKAP  -- Fysik -- Subatomär fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Subatomic Physics (hsv//eng)

Nyckelord

nuclear fuel

gamma radiation detection

characterization

encapsulation

geological disposal

safeguards

Fysik med inriktning mot tillämpad kärnfysik

Physics with specialization in Applied Nuclear Physics

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