Measurements of UF$sub 6$ cylinders with portable instruments

Walton, R.B.; Reilly, T.D.; Parker, Jane; Menzel, J.H.; Marshall, E.D.; Fields, L.W.

doi:10.2172/4449384

Cited by 5 publications

(15 citation statements)

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“…The neutron production rate from 238 U is relatively stable for cylinders in the enrichment range studied here (up to 5% 235 U), as the total mass of 238 U changes by less than 5% over that range. These results for relative contributions and total production rate are consistent with previous calculations and measurement results [Reilly 1991;Walton 1974;Reilly 1974]. Previous studies have indicated that the linearity of the neutron production rate will not be preserved for enrichments greater than 20% due to neutron multiplication with 235 U fission.…”

Section: Non-traditional High-energy Gamma Rays As Indirect Measure Ofsupporting

confidence: 91%

“…Neutron-based signatures are attractive because of the high penetrability of neutrons from the interior of the cylinder volume to the outside wall. The fraction of neutrons escaping the cylinder wall ranged from 0.80 to 0.90 in previous studies [Walton 1974], with weak dependence on the cylinder enrichment and fill level. Berndt [2010]also discusses the impact of fill volume and the configuration of the UF 6 within the cylinder on neutron signatures .…”

Section: Non-traditional High-energy Gamma Rays As Indirect Measure Ofmentioning

confidence: 73%

“…While the resolution of mediumresolution scintillators (e.g., NaI(Tl) and LaBr 3 (Ce)) is inferior to that of high-purity germanium (HPGe), it is still adequate to accurately quantify the net number of counts in the 186-keV peak-if we can realize sufficiently robust methods for subtracting a widely varying continuum. For example, previous work by other groups has shown that NaI-based 186-keV peak analysis, using a collimated handheld device and measurements at a single location on the cylinder, can achieve approximately 5% uncertainty for product cylinders [Walton 1974;Dias 2008]. An underlying assumption of this work is that a fixed-geometry instrument that utilizes an array of medium-resolution scintillator spectrometers can reduce systematic uncertainties due to background variations and UF 6 heterogeneity in the cylinder.…”

Section: Traditional Enrichment Meter Methods Using 186-kev Peak Asmentioning

confidence: 94%

“…235 U Walton [1974] and Reilly [1974] previously studied the potential use of total neutron count rate as a means of determining UF 6 enrichment but this signature is not currently used in IAEA verification measurements. Neutron-based signatures are attractive because of the high penetrability of neutrons from the interior of the cylinder volume to the outside wall.…”

Section: Non-traditional High-energy Gamma Rays As Indirect Measure Ofmentioning

confidence: 99%

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Hybrid Enrichment Assay Methods for a UF6 Cylinder Verification Station: FY10 Progress Report

Smith¹,

Jordan²,

Orton³

et al. 2010

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SummaryPacific Northwest National Laboratory (PNNL) is developing the concept of an automated UF 6 cylinder verification station that would be located at key measurement points to positively identify each cylinder, measure its mass and enrichment, store the collected data in a secure database, and maintain continuity of knowledge on measured cylinders until the arrival of International Atomic Energy Agency (IAEA) inspectors. At the center of this unattended system is a hybrid enrichment assay technique that combines the traditional enrichment-meter method (based on the 186-keV peak from 235 U) with nontraditional neutron-induced high-energy gamma-ray signatures (spawned primarily by 234 U alpha emissions and 19 F(α,n) reactions). Previous work by PNNL provided proof-of-principle for the nontraditional signatures to support accurate, full-volume interrogation of the cylinder enrichment, thereby reducing the systematic uncertainties in enrichment assay due to UF 6 heterogeneity and providing greater sensitivity to material substitution scenarios [Smith 2009;Smith In press].The work described here builds on that preliminary evaluation of the non-traditional signatures, but focuses on a prototype field system utilizing NaI(Tl) and LaBr 3 (Ce) spectrometers, and enrichment analysis algorithms that integrate the traditional and non-traditional signatures. Results for the assay of Type-30B cylinders ranging from 0.2 to 4.95 wt% 235 U, at an AREVA fuel fabrication plant in Richland, WA, are described for the following enrichment analysis methods: 1) traditional enrichment meter signature (186-keV peak) as calculated using a square-wave convolute (SWC) algorithm; 2) nontraditional high-energy gamma-ray signature that provides neutron detection without neutron detectors and 3) hybrid algorithm that merges the traditional and non-traditional signatures. Uncertainties for each method, relative to the declared enrichment for each cylinder, are calculated and compared to the uncertainties from an attended HPGe verification station at AREVA, and the IAEA's uncertainty target values for feed, tail and product cylinders. Table 1 provides a summary of those results below. Traditional NaI (SWC method) 3.5 7.9 13Non-Traditional NaI 3.7 4.9 32Hybrid NaI (simple average) 2.5 4.6 9.71 The target uncertainties are estimated from the combination of systematic and random errors given in Kuhn and should be used only to set the scale of the target uncertainties.iv A summary of the major findings from the field measurements and subsequent analysis follows:• Traditional enrichment-meter assay using specially collimated NaI spectrometers and a SquareWave-Convolute algorithm can achieve uncertainties comparable to HPGe and LaBr for product, natural and depleted cylinders.• Non-traditional signatures measured using NaI spectrometers enable interrogation of the entire cylinder volume and accurate measurement of absolute 235 U mass in product, natural and depleted cylinders.• A hybrid enrichment assay method can achieve lower uncertainties than e...

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Section: Non-traditional High-energy Gamma Rays As Indirect Measure Ofsupporting

confidence: 91%

Section: Non-traditional High-energy Gamma Rays As Indirect Measure Ofmentioning

confidence: 73%

Section: Traditional Enrichment Meter Methods Using 186-kev Peak Asmentioning

confidence: 94%

Section: Non-traditional High-energy Gamma Rays As Indirect Measure Ofmentioning

confidence: 99%

See 2 more Smart Citations

Hybrid Enrichment Assay Methods for a UF6 Cylinder Verification Station: FY10 Progress Report

Smith¹,

Jordan²,

Orton³

et al. 2010

View full text Add to dashboard Cite

show abstract

“…While the resolution of medium-resolution scintillators (e.g., NaI(Tl) and LaBr (Ce)) is far inferior to that of HPGe, it is still adequate to quantify the net number of counts in the 185-keV peak. For example, previous work by other groups has shown that NaI-based 185-keV peak analysis, using a collimated handheld device and measurements at a single location on the cylinder can achieve approximately 5% uncertainty for product cylinders [5], [6].…”

Section: A Traditional Enrichment Meter Methods Using 185-kev Peak Asmentioning

confidence: 99%

Signatures and Methods for the Automated Nondestructive Assay of ${\rm UF}_{6}$ Cylinders at Uranium Enrichment Plants

Smith

Mace

Misner

et al. 2010

IEEE Trans. Nucl. Sci.

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International Atomic Energy Agency (IAEA) inspectors currently perform periodic inspections at uranium enrichment plants to verify UF 6 cylinder enrichment declarations. Measurements are typically performed with handheld high-resolution sensors on a sampling of cylinders taken to be representative of the facility's entire cylinder inventory. These measurements are time-consuming, expensive, and assay only a small fraction of the total cylinder volume. An automated nondestructive assay system capable of providing enrichment measurements over the full volume of the cylinder could improve upon current verification practices in terms of manpower and assay accuracy. The 185-keV emission from U-235 is utilized in today's cylinder measurements, but augmenting this "traditional" signature with more-penetrating "non-traditional" signatures could help to achieve full-volume assay in an automated system. This paper describes the study of non-traditional signatures that include neutrons produced by F-19 ( n) reactions (spawned primarily from U-234 alpha emission) and the high-energy gamma rays (extending up to 8 MeV) induced by those neutrons when they interact in the cylinder wall and nearby materials. The potential of these non-traditional signatures and assay methods for automated cylinder verification is explored using field measurements on a small population of cylinders ranging from 2.0% to 5% in U-235 enrichment. The standard deviation of the non-traditional high-energy gamma-ray assay approach was 4.7% relative to the declared cylinder enrichments; the standard deviation of the traditional enrichment meter approach using a well-collimated high-resolution spectrometer was 4.3%. The prospect of using the non-traditional high-energy gamma-ray signature in concert with the traditional 185-keV signature to reduce the uncertainty of automated cylinder assay is discussed.Index Terms-Gamma-ray spectroscopy, neutron measurements, nondestructive assay, nuclear fuel cycle safeguards, uranium enrichment assay.

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Performance assessment of a 500 mm3 CZT and a 2x2 inch LaBr3(Ce) detectors for the determination of the uranium enrichment using the enrichment-meter method and calibration standards for safeguards applications

Meleshenkovskii

Pauly

Labeau

2020

Applied Radiation and Isotopes

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Determination of the uranium enrichment is an important safeguards verification task, routinely carried out using non-destructive assay methods. The enrichment-meter method is one of the most widely used passive nondestructive X-and gamma-ray based methods used for such tasks. Among its advantages is the highly constrained physical nature of its underlying formalism, allowing it to be used with high-resolution HPGe detectors, as well as with low-resolution NaI detectors. Due to attractive features and spectroscopic performance, CdZnTe and LaBr 3 (Ce) detectors raised interest in their application to such tasks as well. However, their spectroscopic performance is different to that of the traditional detectors in many ways. Application of the enrichment-meter method requires determination of the net peak areas corresponding to 235 U signature photopeaks. The latter requires an adequate algorithm to select the region-of-interest boundaries, which may be sensitive to asymmetrical photopeaks of CZT detectors. In this paper we conduct a performance assessment of a 500 mm 3 CZT detector of a quasihemispherical design and a 2 � 2 inch LaBr 3 (Ce) scintillator with the enrichment-meter method using a set of certified uranium standards with enrichment degrees from 0.31% to 4.46% of 235 U atomic abundance. We investigate the impact of different methods used for net peak area determination, statistical quality of acquired spectra and size of region-of-interest boundaries on accuracy and uncertainty. We propose an algorithm for symmetrical/asymmetrical region-of-interest boundaries determination and make recommendations on the best combinations of the region-of-interest size and method used for the net peak area determination for each of the detectors. The underlying routines of the algorithm and analysis procedures are described in detail and results are presented.

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Measurements of UF$sub 6$ cylinders with portable instruments

Cited by 5 publications

References 0 publications

Hybrid Enrichment Assay Methods for a UF6 Cylinder Verification Station: FY10 Progress Report

Hybrid Enrichment Assay Methods for a UF6 Cylinder Verification Station: FY10 Progress Report

Signatures and Methods for the Automated Nondestructive Assay of ${\rm UF}_{6}$ Cylinders at Uranium Enrichment Plants

Performance assessment of a 500 mm3 CZT and a 2x2 inch LaBr3(Ce) detectors for the determination of the uranium enrichment using the enrichment-meter method and calibration standards for safeguards applications

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Measurements of UF$sub 6$ cylinders with portable instruments

Cited by 5 publications

References 0 publications

Hybrid Enrichment Assay Methods for a UF6 Cylinder Verification Station: FY10 Progress Report

Hybrid Enrichment Assay Methods for a UF6 Cylinder Verification Station: FY10 Progress Report

Signatures and Methods for the Automated Nondestructive Assay of ${\rm UF}_{6}$ Cylinders at Uranium Enrichment Plants

Performance assessment of a 500 mm3 CZT and a 2x2 inch LaBr3(Ce) detectors for the determination of the uranium enrichment using the enrichment-meter method and calibration standards for safeguards applications

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Product

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About

Performance assessment of a 500 mm3 CZT and a 2x2 inch LaBr3(Ce) detectors for the determination of the uranium enrichment using the enrichment-meter method and calibration standards for safeguards applications