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Title: Analysis of an Indirect Neutron Signature for Enhanced UF6 Cylinder Verification

Abstract

The International Atomic Energy Agency (IAEA) currently uses handheld gamma-ray spectrometers combined with ultrasonic wall-thickness gauges to verify the declared enrichment of uranium hexafluoride (UF6) cylinders. The current method provides relatively low accuracy for the assay of 235U enrichment, especially for natural and depleted UF6. Furthermore, the current method provides no capability to assay the absolute mass of 235U in the cylinder due to the localized instrument geometry and limited penetration of the 186-keV gamma-ray signature from 235U. Also, the current verification process is a time-consuming component of on-site inspections at uranium enrichment plants. Toward the goal of a more-capable cylinder assay method, the Pacific Northwest National Laboratory has developed the hybrid enrichment verification array (HEVA). HEVA measures both the traditional 186-keV direct signature and a non-traditional, high-energy neutron-induced signature (HEVANT). HEVANT enables full-volume assay of UF6 cylinders by exploiting the relatively larger mean free paths of the neutrons emitted from the UF6. In this work, Monte Carlo modeling is used as the basis for characterizing HEVANT in terms of the individual contributions to HEVANT from nuclides and hardware components. Monte Carlo modeling is also used to quantify the intrinsic efficiency of HEVA for neutron detection in a cylinder-assay geometry.more » Modeling predictions are validated against neutron-induced gamma-ray spectra from laboratory measurements and a relatively large population of Type 30B cylinders spanning a range of enrichments. Implications of the analysis and findings on the viability of HEVA for cylinder verification are discussed, such as the resistance of the HEVANT signature to manipulation by the nearby placement of neutron-conversion materials.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1339798
Report Number(s):
PNNL-SA-121713
Journal ID: ISSN 0168-9002; DN4001030
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment; Journal Volume: 846
Country of Publication:
United States
Language:
English
Subject:
uranium hexafluoride; uranium enrichment; nondestructive assay; Monte Carlo; neutron measurements; nuclear safeguards

Citation Formats

Kulisek, Jonathan A., McDonald, Benjamin S., Smith, Leon E., Zalavadia, Mital A., and Webster, Jennifer B. Analysis of an Indirect Neutron Signature for Enhanced UF6 Cylinder Verification. United States: N. p., 2017. Web. doi:10.1016/j.nima.2016.12.003.
Kulisek, Jonathan A., McDonald, Benjamin S., Smith, Leon E., Zalavadia, Mital A., & Webster, Jennifer B. Analysis of an Indirect Neutron Signature for Enhanced UF6 Cylinder Verification. United States. doi:10.1016/j.nima.2016.12.003.
Kulisek, Jonathan A., McDonald, Benjamin S., Smith, Leon E., Zalavadia, Mital A., and Webster, Jennifer B. Tue . "Analysis of an Indirect Neutron Signature for Enhanced UF6 Cylinder Verification". United States. doi:10.1016/j.nima.2016.12.003.
@article{osti_1339798,
title = {Analysis of an Indirect Neutron Signature for Enhanced UF6 Cylinder Verification},
author = {Kulisek, Jonathan A. and McDonald, Benjamin S. and Smith, Leon E. and Zalavadia, Mital A. and Webster, Jennifer B.},
abstractNote = {The International Atomic Energy Agency (IAEA) currently uses handheld gamma-ray spectrometers combined with ultrasonic wall-thickness gauges to verify the declared enrichment of uranium hexafluoride (UF6) cylinders. The current method provides relatively low accuracy for the assay of 235U enrichment, especially for natural and depleted UF6. Furthermore, the current method provides no capability to assay the absolute mass of 235U in the cylinder due to the localized instrument geometry and limited penetration of the 186-keV gamma-ray signature from 235U. Also, the current verification process is a time-consuming component of on-site inspections at uranium enrichment plants. Toward the goal of a more-capable cylinder assay method, the Pacific Northwest National Laboratory has developed the hybrid enrichment verification array (HEVA). HEVA measures both the traditional 186-keV direct signature and a non-traditional, high-energy neutron-induced signature (HEVANT). HEVANT enables full-volume assay of UF6 cylinders by exploiting the relatively larger mean free paths of the neutrons emitted from the UF6. In this work, Monte Carlo modeling is used as the basis for characterizing HEVANT in terms of the individual contributions to HEVANT from nuclides and hardware components. Monte Carlo modeling is also used to quantify the intrinsic efficiency of HEVA for neutron detection in a cylinder-assay geometry. Modeling predictions are validated against neutron-induced gamma-ray spectra from laboratory measurements and a relatively large population of Type 30B cylinders spanning a range of enrichments. Implications of the analysis and findings on the viability of HEVA for cylinder verification are discussed, such as the resistance of the HEVANT signature to manipulation by the nearby placement of neutron-conversion materials.},
doi = {10.1016/j.nima.2016.12.003},
journal = {Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment},
number = ,
volume = 846,
place = {United States},
year = {Tue Feb 21 00:00:00 EST 2017},
month = {Tue Feb 21 00:00:00 EST 2017}
}