Measured F(α,n) Yield from <sup>234</sup>U in Uranium Hexafluoride

Miller, Katherine; Swinhoe, Martyn T; Croft, Stuart; Tamura, Takayuki; Aiuchi, Shun; Kawai, Akio; Iwamoto, Tomonori

doi:10.13182/nse12-43

Cited by 12 publications

(5 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is believed that rather than being sensitive to energy spectrum, the factor limiting accuracy of simulations is likely to be the thick target (α,n) yield. The uncertainty in the yield is reported as being 576 ± 7.3% , 474 ± 4.4% (Miller et al 2014), 503 ± ~4% (Kulisek et al 2017; uncertainty estimated by Croft et al 2020), and 507 ± ~1.1% (Croft et al 2020).…”

Section: Discussionmentioning

confidence: 99%

(α,n) nuclear data scoping study

Smith

Brown

Romano

et al. 2020

Self Cite

View full text Add to dashboard Cite

Neutrons from the (a,n) reaction are an important component of nondestructive assay techniques to determine enriched uranium and other actinide inventories in a variety of critical points in the nuclear fuel cycle. However, uncertainties in the cross section, total neutron yield and neutron spectrum, and gamma emissions from these reactions, such as 19 F(a,n) and 17,18 O(a,n), introduce large uncertainties in the determination of mass of actinides of interest and can represent several significant quantities in unaccounted material in certain facility processes. Calculations and measurements depend on accurate nuclear data; however, much of the relevant data in use today was measured in the 1980s and earlier and has not been updated. Thus, the current uncertainties in the cross sections and neutron emission spectra are unacceptably large. This report documents the results of a scoping study of (α,n) reaction data that considered the current state of the data and recommends areas of improvement. It also addresses the codes use to calculate the (a,n) neutron and gamma source terms and recommends code improvements to support required analysis.

show abstract

Section: Discussionmentioning

confidence: 99%

(α,n) nuclear data scoping study

Smith

Brown

Romano

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…For example, it has been stated that typical variation of the wall thickness (~ 0.5 mm) from the nominal value easily leads to an enrichment error of 6% [60]. Furthermore, the mean free path for the dominant -ray at 185.7 keV from 235 U is only ~ 2 mm [62] due to self-absorption, which makes this technique unfavorable for assaying the inner volume of the UF 6 cylinder and unable to detect certain diversion scenarios [63]. A recent report [61] studied -ray spectroscopy on UF 6 cylinders, with correction for attenuation of the 235 U -ray due to the cylinder wall.…”

Section: Gamma-ray Spectroscopymentioning

confidence: 99%

“…However, also similar to -ray spectroscopy, neutron spectroscopy is not a direct measurement for the fissile U-isotope, 235 U -of particular interest in nuclear material safeguards. Because very few neutrons are generated directly from 235 U in UF 6 [63], most neutron counting measurements are based on indirect passive neutron emissions to determine the 235 U enrichment [62,63,65,66]. The neutrons are primarily from 234 U and 238 U -bombardment of fluorine through the 19 F(, n) 22 Na reaction, as well as spontaneous fission in 238 U [63,65].…”

Section: Neutron Spectroscopymentioning

confidence: 99%

“…Compared to -ray spectroscopy, the advantage of neutron spectroscopy is the much longer mean free path of neutrons in UF 6 (~ 600 mm) [62] which, in turn, offer an assay that is sensitive to nearly the entire volume of the cylinder. Reported uncertainty in passive neutron-counting measurements was 5.2% RSD for a batch of UF 6 cylinders with 235 U enrichment ranging from 2.0% to 5.0% [64].…”

Section: Neutron Spectroscopymentioning

confidence: 99%

See 1 more Smart Citation

Scoping study to expedite development of a field deployable and portable instrument for UF6 enrichment assay

Chan¹,

Valentine²,

Russo³

2017

View full text Add to dashboard Cite

The primary objective of the present study is to identity the most promising, viable technologies that are likely to culminate in an expedited development of the next-generation, field-deployable instrument for providing rapid, accurate, and precise enrichment assay of uranium hexafluoride (UF 6 ). UF 6 is typically involved, and is arguably the most important uranium compound, in uranium enrichment processes. As the first line of defense against proliferation, accurate analytical techniques to determine the uranium isotopic distribution in UF 6 are critical for materials verification, accounting, and safeguards at enrichment plants. As nuclear fuel cycle technology becomes more prevalent around the world, international nuclear safeguards and interest in UF 6 enrichment assay has been growing.At present, laboratory-based mass spectrometry (MS), which offers the highest attainable analytical accuracy and precision, is the technique of choice for the analysis of stable and longlived isotopes. Currently, the International Atomic Energy Agency (IAEA) monitors the production of enriched UF 6 at declared facilities by collecting a small amount (between 1 to 10 g) of gaseous UF 6 into a sample bottle, which is then shipped under chain of custody to a central laboratory (IAEA's Nuclear Materials Analysis Laboratory) for high-precision isotopic assay by MS. The logistics are cumbersome and new shipping regulations are making it more difficult to transport UF 6 . Furthermore, the analysis is costly, and results are not available for some time after sample collection. Hence, the IAEA is challenged to develop effective safeguards approaches at enrichment plants. In-field isotopic analysis of UF 6 has the potential to substantially reduce the time, logistics and expense of sample handling. However, current laboratory-based MS techniques require too much infrastructure and operator expertise for field deployment and operation. As outlined in the IAEA Department of Safeguards Long-Term R&D Plan, 2012-2023, one of the IAEA long-term R&D needs is to "develop tools and techniques to enable timely, potentially real-time, detection of HEU (Highly Enriched Uranium) production in LEU (Lowly Enriched Uranium) enrichment facilities" (Milestone 5.2). iv measurements that do not require the stated high accuracy or precision of the ITVs to which it was compared).The list presented below summarizes the outcome of the present study, and groups all reviewed techniques into "recommended", "promising", or "not recommended"; the "benchmark" techniques are also included and labeled as such. The list is presented in a highly abridged way such that only the final recommendations are given. The performance of a technique in the seven evaluation metrics and its ranking are summarized in Table 6.1, whereas short discussion and comments on the recommendation can be found in Section 6.2 of this report. Furthermore, comprehensive and in-depth reviews on the scientific principle of each technique, its instrument option, its limitations and main gaps betwe...

show abstract

“…The F(α,n) reaction is the focus of on-going research in part because it is an important source of neutrons in the nuclear fuel cycle which can be exploited to assay nuclear materials, especially uranium in the form of UF6 [1,2]. At the present time there remains some considerable uncertainty (of the order of 720%) in the thick target integrated over angle (α,n) yield from 19 F (100% natural abundance) and its compounds as discussed in [3,4].…”

Section: Introductionmentioning

confidence: 99%