Confirmatory measurements of UF/sub 6/ using the neutron self-interrogation method

Conference · Tue Jan 01 04:00:00 EST 1985 · J. Nucl. Mater. Manage.; (United States)

OSTI ID:5483031

Stewart, J E; Ensslin, N; Menlove, H O; Cowder, L R; Polk, P J

A passive neutron counting method has been developed for measurement of the /sup 235/U mass in Model 5A cylinders of UF/sub 6/. The unique neutronic properties of UF/sub 6/ containing highly enriched uranium (HEU) permit /sup 235/U assay using only passive neutron counting. The sample effectively assays itself by self-interrogation. Shipped from enrichment plants and received at fuel fabrication and conversion facilities, 5A UF/sub 6/ cylinders hold up to approx. =17 kg of /sup 235/U each. Field measurements at the Portsmouth Gaseous Diffusion Plant (GDP) showed an average assay accuracy of 6.8% (1sigma) for 44 cylinders with enrichments from 6 to 98% and with a range of fill heights. Further measurements on 38 cylinders containing 97%-enriched material yielded an accuracy of 2.8% (1sigma). Typical counting times for these measurements were less than 5 min. An in-plant instrument for receipts confirmation measurements of 5A UF/sub 6/ cylinders has been developed for the Savannah River Plant. The Receipts Assay Monitor (RAM) is currently being tested and calibrated. It is designed to confirm declared fissile mass in all incoming 5A cylinders containing HEU in the form of UF/sub 6/. One of the computer-controlled features is a removable cadmium liner for the sample cavity. The liner allows a sample fill-height correction, which significantly improves assay accuracy.

• Research Organization: Los Alamos National Lab., Los Alamos, NM 87544
• OSTI ID: 5483031
• Report Number(s): CONF-850765-
• Conference Information: Journal Name: J. Nucl. Mater. Manage.; (United States) Journal Volume: 14:3
• Country of Publication: United States
• Language: English

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