TIME-SPECTRAL ANALYSIS ALGORITHMS FOR LEAD SLOWING-DOWN SPECTROSCOPY OF SPENT FUEL
Nondestructively determining the plutonium content in spent fuel assemblies continues to be a considerable challenge in the safeguarding of nuclear fuel cycles. Motivating needs for such measurements include quantifying material input at a reprocessing facility, determining the shipper-receiver difference, and recovering continuity of knowledge. A nondestructive assay (NDA) technology that could provide timely (tens of minutes), independent (no operator-declared information), and direct measurement of Pu mass that improves upon the uncertainty of today’s confirmatory methods would be a major step forward for spent fuel materials accountability. Lead slowing-down spectroscopy (LSDS) is one potential fuel assay technique; previous work has indicated promise of the method for specific fuel types and assay assumptions. In this work, the focus is the assay of pressurized water reactor assemblies over a wide burnup range, under the following assumptions: a) No a priori information (e.g. initial loading or burnup) is available about the assembly, and b) No pre-existing calibration generated from the measurement of many similar assemblies is available. The technical emphasis of this paper is the development of time-spectral analysis algorithms for LSDS that can extract as much isotopic information as possible from the complex, but content-rich assay signal. The key advancement described here is a mathematical relationship to account for self-shielding created by the fissile isotopes and the effects of neutron-absorbing fission and activation products. This formulation utilizes the known energy-dependent cross-sections from key isotopes, but leaves their mass as free variables. Multi-parameter regression analysis is used to directly calculate not only the mass of fissile isotopes in the fuel assembly (e.g. Pu-239, U-235 and Pu-241), but also the mass of key absorbing isotopes such as Pu-240 and U-238. Preliminary results, using a first-order self-shielding relationship, indicate that LSDS has the potential to directly measure total Pu with less than 5% average relative error, over a burnup range from 0 to 60 GWd/MTU. Assay of U-235 and U-238 is also possible, though with higher uncertainties. Deficiencies in the self-shielding model and methods to improve that formulation are described, along with application of the method to a wider range of fuel types and burnups.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 990589
- Report Number(s):
- PNNL-SA-66875; AF5835000; TRN: US1007345
- Resource Relation:
- Conference: Proceedings of the 50th Annual Meeting of the Institute of Nuclear Materials Management
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
ALGORITHMS
BURNUP
CALIBRATION
COMPUTER CALCULATIONS
CROSS SECTIONS
FISSION
NONDESTRUCTIVE ANALYSIS
NUCLEAR FUELS
NUCLEAR MATERIALS MANAGEMENT
PLUTONIUM
PWR TYPE REACTORS
REGRESSION ANALYSIS
REPROCESSING
SAFEGUARDS
SELF-SHIELDING
SHIPPER-RECEIVER DIFFERENCES
SLOWING-DOWN
SPECTROSCOPY
SPENT FUELS