Delayed Gamma-Ray Spectroscopy for Non-Destructive Assay of Nuclear Materials

Ludewigt, Bernhard¹  Mozin, Vladimir¹  Campbell, Luke²  Favalli, Andrea³  Alan W. Hunt  Reedy, Edward T.E.⁴  Seipel, Heather⁴ 

[1] Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States);Pacific Northwest National Lab. (PNNL), Richland, WA (United States);Los Alamos National Lab. (LANL), Los Alamos, NM (United States);Idaho National Lab. (INL), Idaho Falls, ID (United States)

关键词: SPENT FUELS;    MIXED OXIDE FUELS;    FISSION PRODUCTS;    RADIOACTIVE WASTES;    THERMAL NEUTRONS;    PHOTOFISSION;    NEUTRON REACTIONS;    GAMMA SPECTROSCOPY;    PLUTONIUM 241 TARGET;    DELAYED GAMMA RADIATION;    PLUTONIUM 239 TARGET;    URANIUM 235 TARGET;    HIGH-PURITY GE DETECTORS;    LANTHANUM BROMIDES;    RADIOACTIVE WASTE STORAGE;    COMPARATIVE EVALUATIONS;    FISSION FRAGMENTS;    FISSION;    REPROCESSING;    COMPUTERIZED SIMULATION;    COMPUTER CODES;    GAMMA SPECTRA;    VERIFICATION;    YIELDS;    ARMS CONTROL;    ENERGY DEPENDENCE;    TIME DEPENDENCE;    BENCHMARKS;    INVENTORIES;    NATIONAL SECURITY;    SPENT FUEL STORAGE;    RADIOACTIVE WASTE DISPOSAL;    CHEMICAL COMPOSITION;    ISOTOPE RATIO;    SPECTRA UNFOLDING;   

DOI  :  10.2172/1236370
RP-ID  :  LBNL--184622
PID  :  OSTI ID: 1236370
Others  :  Other: ir:184622
Others  :  TRN: US1600261

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来源: SciTech Connect

【 摘 要 】

High-??energy, beta-delayed gamma-??ray spectroscopy is a potential, non-??destructive assay techniques for the independent verification of declared quantities of special nuclear materials at key stages of the fuel cycle and for directly assaying nuclear material inventories for spent fuel handling, interim storage, reprocessing facilities, repository sites, and final disposal. Other potential applications include determination of MOX fuel composition, characterization of nuclear waste packages, and challenges in homeland security and arms control verification. Experimental measurements were performed to evaluate fission fragment yields, to test methods for determining isotopic fractions, and to benchmark the modeling code package. Experimental measurement campaigns were carried out at the IAC using a photo-??neutron source and at OSU using a thermal neutron beam from the TRIGA reactor to characterize the emission of high-??energy delayed gamma rays from ²³⁵U, ²³⁹Pu, and ²⁴¹Pu targets following neutron induced fission. Data were collected for pure and combined targets for several irradiation/spectroscopy cycle times ranging from 10/10 seconds to 15/30 minutes.The delayed gamma-ray signature of ²⁴¹Pu, a significant fissile constituent in spent fuel, was measured and compared to ²³⁹Pu. The ²⁴¹Pu/²³⁹Pu ratios varied between 0.5 and 1.2 for ten prominent lines in the 2700-??3600 keV energy range. Such significant differences in relative peak intensities make it possible to determine relative fractions of these isotopes in a mixed sample. A method for determining fission product yields by fitting the energy and time dependence of the delayed gamma-??ray emission was developed and demonstrated on a limited ²³⁵U data set. De-??convolution methods for determining fissile fractions were developed and tested on the experimental data. The use of high count-??rate LaBr₃ detectors was investigated as a potential alternative to HPGe detectors. Modeling capabilities were added to an existing framework and codes were adapted as needed for analyzing experiments and assessing application-??specific assay concepts. A de-??convolution analysis of the delayed gamma-??ray response spectra modeled for spent fuel assemblies was performed using the same method that was applied to the experimental spectra.