[en] A criteria that a sample of highly enriched uranium (HEU) had come from a weapons stockpile and not newly produced in an enrichment plant is to show that the HEU had been produced a significant time in the past. The time since the HEU has produced in an enrichment plant is defined as the age of the HEU in this paper. The HEU age is determined by measuring quantitatively the daughter products ²³⁰Th and ²³¹Pa of ²³⁴U and ²³⁵U, respectively, by first chemical separation of the thorium and protactinium and then conducting alpha spectrometry of the daughter products

[en] In early March 1994, eight highly enriched uranium (HEU) samples were collected from materials stored at the Ulba Metallurgical Plant in Oskamen (Ust Kamenogorsk), Kazakhstan. While at the plant site, portions of four samples were dissolved and analyzed by mass spectrograph at the Ulba analytical laboratory by Ulba analysts. Three of these mass spectrograph solutions and the eight HEU samples were subsequently delivered to the Y-12 Plant for complete chemical and isotopic analyses. Chemical forms of the eight samples were uranium metal chips, U0₂ powder, uranium/beryllium oxide powder, and uranium/beryllium alloy rods. All were declared by the Ulba plant to have a uranium assay of ∼90 wt % ²³⁵U. The uranium/beryllium powder and alloy samples were also declared to range from about 8 to 28 wt % uranium. The chemical and uranium isotopic analyses done at the Y-12 Plant confirm the Ulba plant declarations. All samples appear to have been enriched using some reprocessed uranium, probably from recovery of uranium from plutonium production reactors. As a result, all samples contain some ²³⁶U and ²³²U and have small but measurable quantities of plutonium. This plutonium could be the result of either contamination carried over from the enrichment process or cross-contamination from weapons material. It is not the result of direct reactor exposure. Neither the ²³²U nor the plutonium concentrations are sufficiently high to provide a significant industrial health hazard. Both are well within established or proposed acceptance criteria for storage at Y-12. The trace metal analyses showed that, with the exception of beryllium, there are no trace metals in any of these HEU samples that pose a significant health hazard

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[en] The necessity of accounting for the correlation of experimental uncertainties when determining calculational uncertainty in criticality predictions is demonstrated in this paper. An example of constructing the correlation matrix for the experimental uncertainties of the experiments with highly enriched uranium solutions performed and evaluated at the Institute of Physics and Power Engineering, Russian Federation, is presented. A conclusion is drawn with regard to the significant influence of the correlations on the average calculation-experiment deviation and the deviation uncertainty

[en] The SCALE 6.1 code system includes a multigroup (MG) method for three-dimensional (3D) sensitivity analyses via the Tools for Sensitivity and Uncertainty Analysis Methodology Implementation (TSUNAMI), and the upcoming release of SCALE 6.2 will feature the system's first implementation of continuous-energy (CE) sensitivity methods. Detailed information regarding the CE TSUNAMI-3D eigenvalue sensitivity methods is provided in a companion paper. This work compares the results of TSUNAMI-3D calculations using the traditional MG approach to the new CE CLUTCH method in SCALE 6.2. The systems examined in this study include combinations of fast, thermal, and mixed spectra with metal, compound, and solution material forms. The primary fissile species include low-enriched uranium, intermediate-enriched uranium, high-enriched uranium, plutonium, and mixed uranium and plutonium. This broad range of systems expands the experience base with the CE CLUTCH method, identifies best practices for using the code, and provides generic user guidance for utilizing this new capability. Additionally, the study demonstrates the accuracy and usefulness of the CE CLUTCH method, especially for systems for which MG methods perform poorly. (authors)

[en] This report describes the activities necessary to support the numerous transportation tasks involved with the successful completion of the mini-plate MP-1 and future MP experiments for the U.S. High Performance Research Reactor HEU to LEU conversion program. It includes information about the general activities necessary to implement equipment, operational processes, and safety basis changes required at the shipping facility and receipt facilities to support the shipments.

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[en] In summer 2005, the United States loosened restrictions on the export of bomb-grade, highly-enriched uranium (HEU) to five countries (Canada, Belgium, France, Germany, and the Netherlands) for use as targets to produce medical isotopes. The new law represents a step backward from the quarter-century U.S. effort to phase out commerce in bomb-grade uranium to reduce risks of nuclear proliferation and terrorism. This paper first investigates the actors behind this change -- including foreign producers of medical isotopes, their U.S.-based lobbyists, supportive sectors of the American medical community, and the lawmakers who spearheaded efforts on Capitol Hill -- and their motivations. Second, it explores the dramatic and complicated legislative process that led to this weakening of export controls. Third, it projects the likely consequences in the short and long run for U.S. HEU exports, risks of nuclear terrorism, and the production of medical isotopes in the United States and elsewhere - assuming the new law remains in place. Finally, the paper examines prospects for additional changes in U.S. HEU export control law, either to further loosen restrictions on export of HEU for targets and/or fuel, restore previous controls, or adopt new strategies to phase out HEU commerce. (author)

[en] With large uranium stockpiles, particularly in the form of HEU, continuing to be the dominant factor in the world uranium market, buyers should be able to enter into attractive long-term commitments for the future. Nevertheless, producers are now able to see forward with some degree of certainty and are expected to meet their planned levels of production and demand. (author)