Sensitivity of the simulation of passive neutron emission from UF6 cylinders to the uncertainties in both 19F(α,n) energy spectrum and thick target yield of 234U in UF6
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of Texas, Austin, TX (United States)
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Interest in safeguards verification measurements using passive thermal neutron counting to assay 235U content in large 30B UF6 canisters has grown in recent years. Here, the prohibitively high cost and impracticality of using reference 30B calibration cylinders extensively will likely make accurate simulations of increasing interest. Accuracy of the simulated response will define the confidence in the predicted response and the extent to which simulations can reasonably be relied upon. With 234U driven 19F(α, n) reactions being the main neutron source in low enriched UF6 the uncertainties of the 19F(α, n) energy spectrum and the thick target yield of 234U in UF6 propagate into the uncertainty in the predicted response and represent a major influence of basic nuclear data. Here sensitivity of the simulated total (Singles) and coincidence (Doubles) count rates are assessed for the Passive Neutron Enrichment Meter using six potential 19F(α, n) neutron energy spectra over a range of enrichments and material distributions. The results indicate that variations in the Singles and Doubles due to simulated (α, n) neutron spectrum are less than 1.5% for this set of simulated neutron spectra, with dependence varying inversely with enrichment. Singles uncertainty is only slightly less than that of the thick target 19F(α, n) yield corresponding to the primary neutron source, whereas the 19F(α, n) yield dependence of the Doubles is reduced by the non-negligible 238U(SF) coincident neutron emissions. Based on available thick target 19F(α, n) yield estimates the uncertainty is on the order of 5%, establishing this as the main nuclear data limitation when simulating thermal neutron detectors response for 30B UF6 storage cylinders. Based on these findings, it appears that the measurement and evaluation of the thick target 19F(α, n) yield for uranium hexafluoride is due.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA), Office of Nonproliferation and Verification Research and Development (NA-22); USDOE
- Grant/Contract Number:
- 89233218CNA000001
- OSTI ID:
- 1787295
- Alternate ID(s):
- OSTI ID: 1788092
- Report Number(s):
- LA-UR-21-20862; TRN: US2210440
- Journal Information:
- Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 1009; ISSN 0168-9002
- Publisher:
- ElsevierCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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