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Planning the HEU to LEU Transition for the NBSR

Description: A study has been carried out to understand how the NIST research reactor (NBSR) might be converted from using high-enriched uranium (HEU) to using low-enriched uranium (LEU) fuel. An LEU fuel design had previously been determined which provides an equilibrium core with the desirable fuel cycle length—a very important parameter for maintaining the experimental, scientific program supported by the NBSR. In the present study two options for getting to the equilibrium state are considered. One option starts with the loading of an entire core of fresh fuel. This was determined to be unacceptable. The other option makes use of the current fuel management scheme wherein four fresh fuel elements are loaded at the beginning of each cycle. However, it is shown that without some alterations to the fuel cycle, none of the transition cores containing both HEU and LEU fuel have sufficient excess reactivity to enable reactor operation for the required amount of time. It was determined that operating the first mixed cycle for a sufficiently reduced length of time provides the excess reactivity which enables subsequent transition cycles to be run for the desired number of days.
Date: October 24, 2011
Creator: Hanson, A.L. & Diamond, D.
Partner: UNT Libraries Government Documents Department

Conversion and Blending Facility highly enriched uranium to low enriched uranium as metal. Revision 1

Description: The mission of this Conversion and Blending Facility (CBF) will be to blend surplus HEU metal and alloy with depleted uranium metal to produce an LEU product. The primary emphasis of this blending operation will be to destroy the weapons capability of large, surplus stockpiles of HEU. The blended LEU product can only be made weapons capable again by the uranium enrichment process. The blended LEU will be produced as a waste suitable for storage or disposal.
Date: July 5, 1995
Partner: UNT Libraries Government Documents Department

Conversion and Blending Facility highly enriched uranium to low enriched uranium as uranyl nitrate hexahydrate. Revision 1

Description: This Conversion and Blending Facility (CBF) will have two missions: (1) convert HEU materials to pure HEU uranyl nitrate (UNH) and (2) blend pure HEU UNH with depleted and natural UNH to produce HEU UNH crystals. The primary emphasis of this blending operation will be to destroy the weapons capability of large, surplus stockpiles of HEU. The blended LEU product can only be made weapons capable again by the uranium enrichment process. To the extent practical, the chemical and isotopic concentrations of blended LEU product will be held within the specifications required for LWR fuel. Such blended LEU product will be offered to the United States Enrichment Corporation (USEC) to be sold as feed material to the commercial nuclear industry. Otherwise, blended LEU Will be produced as a waste suitable for storage or disposal.
Date: July 5, 1995
Partner: UNT Libraries Government Documents Department

Source modulation-correlation measurement for fissile mass flow in gas or liquid fissile streams

Description: The method of monitoring fissile mass flow on all three legs of a blending point, where the input is high-enriched uranium (HEU) and low-enriched uranium (LEU) and the product is PEU, can yield the fissile stream velocity and, with calibration, the [sup235]U content. The product of velocity and content integrated over the pipe gives the fissile mass flow in each leg. Also, the ratio of fissile contents in each pipe: HEU/LEU, HEU/PEU, and PEU/LEU, are obtained. By modulating the source on the input HEU pipe differently from that on the output pipe, the HEU gas can be tracked through the blend point. This method can be useful for monitoring flow velocity, fissile content, and fissile mass flow in HEU blenddown of UF[sub 6] if the pressures are high enough to contain some of the induced fission products. This method can also be used to monitor transfer of fissile liquids and other gases and liquids that emit radiation delayed from particle capture. These preliminary experiments with the Oak Ridge apparatus show that the method will work and the modeling is adequate.
Date: September 1, 1996
Creator: Mihalczo, J.T.; March-Leuba, J.A.; Valentine, T.E.; Abston, R.A.; Mattingly, J.K. & Mullens, J.A.
Partner: UNT Libraries Government Documents Department

Converting {sup 99}Mo production from high- to low-enriched uranium

Description: This paper discusses efforts towards LEU substitution in two HEU targets. One type is the Cintichem target, a closed cylinder with a thin coating of uranium dioxide electroplated ion the inside wall. To successfully increase the amount of uranium per target, we are developing a target that uses LEU metal foil. Uranium surface preparation is discussed.
Date: September 1, 1997
Creator: Vandegrift, G.F.; Conner, C.J.; Sedlet, J. & Wygmans, D.G.
Partner: UNT Libraries Government Documents Department

The Development of Mobile Melt-Dilute Technology for the Treatment of Former Soviet Union Research Reactor Fuel

Description: On-site application of the MMD process offers an economical method for converting weapons usable Former Soviet Union (FSU) High Enriched Uranium (HEU) research reactor fuel to a safe and secure Low Enriched Uranium (LEU) ingot. The objective of the MMD Project is to develop the mobile melt and dilute technology in preparation for active equipment deployment in the Newly Independent States (NIS) of the FSU.
Date: October 9, 2003
Creator: Adams, T.
Partner: UNT Libraries Government Documents Department

HEU to LEU conversion and blending facility: Metal blending alternative to produce LEU oxide for disposal

Description: US DOE is examining options for disposing of surplus weapons-usable fissile materials and storage of all weapons-usable fissile materials. The nuclear material is converted to a form more proliferation- resistant than the original form. Blending HEU (highly enriched uranium) with less-enriched uranium to form LEU has been proposed as a disposition option. Five technologies are being assessed for blending HEU. This document provides data to be used in environmental impact analysis for the HEU-LEU disposition option that uses metal blending with an oxide waste product. It is divided into: mission and assumptions, conversion and blending facility descriptions, process descriptions and requirements, resource needs, employment needs, waste and emissions from plant, hazards discussion, and intersite transportation.
Date: September 1, 1995
Partner: UNT Libraries Government Documents Department

Analysis of HEU samples from the ULBA Metallurgical Plant

Description: 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, U0{sub 2} powder, uranium/beryllium oxide powder, and uranium/beryllium alloy rods. All were declared by the Ulba plant to have a uranium assay of {approximately}90 wt % {sup 235}U. 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 {sup 236}U and {sup 232}U 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 {sup 232}U 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.
Date: May 1, 1995
Creator: Gift, E.H.
Partner: UNT Libraries Government Documents Department

HEU age determination

Description: 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 {sup 230}Th and {sup 231}Pa of {sup 234}U and {sup 235}U, respectively, by first chemical separation of the thorium and protactinium and then conducting alpha spectrometry of the daughter products.
Date: December 31, 1994
Creator: Moorthy, A.R. & Kato, W.Y.
Partner: UNT Libraries Government Documents Department

Estimated Critical Conditions for UO(Sub 2)F(Sub 2)-H(Sub 2)O Systems in Fully Water-Reflected Spherical Geometry

Description: The purpose of this report is to document reference calculations performed using the SCALE-4.0 code system to determine the critical parameters of UO{sub 2}F{sub 2}-H{sub 2}O spheres. The calculations are an extension of those documented in ORNL/CSD/TM-284. Specifically, the data for low-enriched UO{sub 2}F{sub 2}-H{sub 2}O spheres have been extended to highly enriched uranium. These calculations, together with those reported in ORNL/CSD/TM-284, provide a consistent set of critical parameters (k{sub {infinity}}, volume, mass, mass of water) for UO{sub 2}F{sub 2} and water over the full range of enrichment and moderation ratio.
Date: January 1, 1992
Creator: Jordan, W.C.
Partner: UNT Libraries Government Documents Department

Evaluation of Two Solid Forms for Shipping Enriched Uranium

Description: Because of the possibility of an enriched uranium spill in transit, a program has been initiated to develop safer methods of shipment. This report compares uranium on resin with conversion to unpurified UO3, and provides information needed to judge the relative merits of the processes to produce these two solid forms.
Date: August 26, 2002
Creator: Wilds, G.W.
Partner: UNT Libraries Government Documents Department

Transient analysis for the tajoura critical facility with IRT-2M HEU fuel and IRT-4M leu fuel : ANL independent verification results.

Description: Calculations have been performed for postulated transients in the Critical Facility at the Tajoura Nuclear Research Center (TNRC) in Libya. These calculations have been performed at the request of staff of the Renewable Energy and Water Desalinization Research Center (REWDRC) who are performing similar calculations. The transients considered were established during a working meeting between ANL and REWDRC staff on October 1-2, 2005 and subsequent email correspondence. Calculations were performed for the current high-enriched uranium (HEU) core and the proposed low-enriched uranium (LEU) core. These calculations have been performed independently from those being performed by REWDRC and serve as one step in the verification process.
Date: December 2, 2005
Creator: Garner, P. L. & Hanan, N. A.
Partner: UNT Libraries Government Documents Department

Neutron Radiography Reactor Reactivity -- Focused Lessons Learned

Description: As part of the Global Threat Reduction Initiative, the Neutron Radiography Reactor (NRAD) at the Idaho National Laboratory (INL) was converted from using highly enriched uranium (HEU) to low enriched uranium (LEU) fuel. After the conversion, NRAD resumed operations and is meeting operational requirements. Radiography image quality and the number of images that can be produced in a given time frame match pre-conversion capabilities. However, following the conversion, NRAD’s excess reactivity with the LEU fuel was less than it had been with the HEU fuel. Although some differences between model predictions and actual performance are to be expected, the lack of flexibility in NRAD’s safety documentation prevented adjusting the reactivity by adding more fuel, until the safety documentation could be modified. To aid future reactor conversions, a reactivity-focused Lessons Learned meeting was held. This report summarizes the findings of the lessons learned meeting and addresses specific questions posed by DOE regarding NRAD’s conversion and reactivity.
Date: November 1, 2010
Creator: Woolstenhulme, Eric; Damiana, Randal; Schreck, Kenneth; Phillips, Ann Marie & Hewit, Dana
Partner: UNT Libraries Government Documents Department

LEU conversion status of US research reactors, September 1996

Description: This paper summarizes the conversion status of research and test reactors in the United States from the use of fuels containing highly- enriched uranium (HEU, greater than or equal to 20%) to the use of fuels containing low-enriched uranium (LEU, < 20%). Estimates of the uranium densities required for conversion are made for reactors with power levels greater than or equal to 1 MW that are not currently involved in the LEU conversion process.
Date: October 7, 1996
Creator: Matos, J.E.
Partner: UNT Libraries Government Documents Department

Low enrichment fuel conversion for Iowa State University. Final report

Description: The UTR-10 research and teaching reactor at Iowa State University (ISU) has been converted from high-enriched fuel (HEU) to low- enriched fuel (LEU) under Grant No. DE-FG702-87ER75360 from the Department of Energy (DOE). The original contract period was August 1, 1987 to July 31, 1989. The contract was extended to February 28, 1991 without additional funding. Because of delays in receiving the LEU fuel and the requirement for disassembly of the HEU assemblies, the contract was renewed first through May 31, 1992, then through May 31, 1993 with additional funding, and then again through July 31, 1994 with no additional funding. In mid-August the BMI cask was delivered to Iowa State. Preparations are underway to ship the HEU fuel when NRC license amendments for the cask are approved.
Date: October 17, 1996
Creator: Bullen, D.B. & Wendt, S.E.
Partner: UNT Libraries Government Documents Department

Results of active well coincidence counter cross-calibration measurements at Argonne National Laboratory-West.

Description: Nondestructive Assay (NDA) of Nuclear Materials (NM) is a common tool used by inspectors involved in Material Protection, Control and Accounting (MPC&amp;A) programs, both domestically and internationally. NDA is generally used to quantify the properties of NM, usually by determining the mass or enrichment of materials such as U-235 or Pu-240. For the NDA of Highly Enriched Uranium (HEU) metal, powder or scrap samples, Active Well Coincidence Counter (AWCC) NDA systems are routinely used. These systems bombard samples with neutrons, inducing fission events. The fissile mass of the sample is determined based upon the number of coincidence neutrons detected. To obtain accurate quantitative measurements using AWCC systems it is necessary to calibrate the instruments using physical standards representative of the unknown sample to be measured. During international inspections it is both expensive and difficult to obtain the large number of physical standards necessary to accurately assay the wide range of NM present at multiple sites. To address this issue, a cross-calibration method has been developed by Los Alamos National Laboratory (LANL) allowing the transfer of calibration parameters measured to field inspection systems without the need for physical standards. Argonne National Laboratory-West (ANLW) routinely uses AWCC systems as part of its MPC&amp;A program to verify the fissile mass of HEU items of various enrichments. In addition, ANLW is involved in a MPC&amp;A program initiated by the U.S. Department of Energy (DOE) to provide AWCC system support to Russia. Approximately 25 AWCCs have been delivered to Russia through this program. Before shipment to Russia, the AWCC systems measured reference standards at LANL. The results of these measurements are included in Appendix II and III. Using this data, a study of the cross calibration technique using low enriched uranium was performed by the Moscow State Engineering Physics Institute (MEPhI) with encouraging results. The ...
Date: October 22, 2002
Creator: Jensen, B. A.; Sanders, J.; Wenz, T. & R., Buchheit.
Partner: UNT Libraries Government Documents Department

Analyses for conversion of the Georgia Tech Research Reactor from HEU to LEU fuel

Description: This document presents information concerning: analyses for conversion of the Georgia Tech Research Reactor from HEU to LEU; changes to technical specifications mandated by the conversion of the GTRR to low enrichment fuel; changes in the Safety Analysis Report mandated by the conversion of the GTRR to low enrichment fuel; and copies of all changed pages of the SAR and the technical specifications.
Date: September 1, 1992
Creator: Matos, J.E.; Mo, S.C. & Woodruff, W.L.
Partner: UNT Libraries Government Documents Department

Progress in dissolving modified LEU Cintichem targets

Description: A process is under development to use low-enriched uranium (LEU) metal targets for production of {sup 99}Mo. The first step is to dissolve the irradiated foil. In past work, this has been done by heating a closed (sealed) vessel containing the foil and a solution of nitric and sulfuric acids. In this work, the authors have demonstrated that (1) the dissolver solution can contain nitric acid alone, (2) uranium dioxide is also dissolved by nitric acid alone, and (3) barrier metals of Cu, Fe, or Ni on the U foil are also dissolved by nitric acid. Changes to the dissolver design and operation needed to accommodate the uranium foil are discussed, including (1) simple operations that are easy to do in a remote-maintenance facility, (2) heat removal from the irradiated LEU foil, and (3) cold trap operation with high dissolver pressures.
Date: December 31, 1996
Creator: Leonard, R.A.; Chen, L.; Mertz, C.J. & Vandegrift, G.F.
Partner: UNT Libraries Government Documents Department

Development and processing of LEU targets for {sup 99}Mo production

Description: Most of the world`s supply of {sup 99m}Tc for medical purposes is currently produced from the decay of {sup 99}Mo derived from the fissioning of high-enriched uranium (HEU). Substantial progress has been made in developing targets and chemical processes for producing {sup 99}Mo using low-enriched uranium (LEU). Target development has been focused on a uranium-metal foil target as a replacement for the coated-UO{sub 2} Cintichem-type target. Although the first designs were not successful because of ion mixing-induced bonding of the uranium foil to the target tubes, recent irradiations of modified targets have proven successful. Only minor modifications of the Cintichem chemical process are required for the uranium-metal foil targets. A demonstration using prototypically irradiated targets is anticipated in February 1997. Progress has also been made in basic dissolution of both uranium-metal foil and aluminum-clad U{sub 3}Si{sub 2} dispersion fuel targets.
Date: April 1, 1997
Creator: Snelgrove, J.L.; Vandegrift, G.F. & Hofman, G.L.
Partner: UNT Libraries Government Documents Department

Progress in chemical treatment of LEU targets by the modified Cintichem process

Description: Presented here are recent experimental results on tests of a modified Cintichem process for producing {sup 99}Mo from low enriched uranium (LEU). Studies were focused in three areas: (1) testing the effects on {sup 99}Mo recovery and purity of dissolving LEU foil in nitric acid alone, rather than in the sulfuric/nitric acid mixture currently used, (2) measuring decontamination factors for radionuclide impurities in each purification step, and (3) testing the effects on processing of adding barrier materials to the LEU metal-foil target. The experimental results show that switching from dissolving the target in the sulfuric/nitric mixture to using nitric acid alone should cause no significant difference in {sup 99}Mo product yield or purity. Further, the results show that overall decontamination factors for gamma emitters in the LEU-target processing are high enough to meet the purity requirements for the {sup 99}Mo product. The results also show that the selected barrier materials, Cu, Fe, and Ni, do not interfere with {sup 99}Mo recovery and can be removed during chemical processing of the LEU target.
Date: December 31, 1996
Creator: Wu, D.; Landsberger, S. & Vandegrift, G.F.
Partner: UNT Libraries Government Documents Department

HEU to LEU Conversion and Blending Facility: UF{sub 6} blending alternative to produce LEU UF{sub 6} for commercial use

Description: US DOE is examining options for disposing of surplus weapons-usable fissile materials and storage of all weapons-usable fissile materials; the nuclear material will be converted to a form more proliferation- resistant than the original form. Examining options for increasing the proliferation resistance of highly enriched uranium (HEU) is part of this effort. Five technologies for blending HEU will be assessed; blending as UF{sub 6} to produce a UF{sub 6} product for commercial use is one of them. This document provides data to be used in the environmental impact analysis for the UF{sub 6} blending HEU disposition option. Resource needs, employment needs, waste and emissions from plant, hazards, accident scenarios, and intersite transportation are discussed.
Date: September 1, 1995
Partner: UNT Libraries Government Documents Department

U.S. transparency monitoring of HEU oxide conversion and blending to LEU hexafluoride at three Russian blending plants

Description: The down-blending of Russian highly enriched uranium (HEU) takes place at three Russian gaseous centrifuge enrichment plants. The fluorination of HEU oxide and down-blending of HEU hexafluoride began in 1994, and shipments of low enriched uranium (LEU) hexafluoride product to the United States Enrichment Corporation (USEC) began in 1995 US transparency monitoring under the HEU Purchase Agreement began in 1996 and includes a permanent monitoring presence US transparency monitoring at these facilities is intended to provide confidence that HEU is received and down-blended to LEU for shipment to USEC The monitoring begins with observation of the receipt of HEU oxide shipments, including confirmation of enrichment using US nondestructive assay equipment The feeding of HEU oxide to the fluorination process and the withdrawal of HEU hexafluoride are monitored Monitoring is also conducted where the blending takes place and where shipping cylinders are filled with LEU product. A series of process and material accountancy documents are provided to US monitors.
Date: July 27, 1998
Creator: Leich, D.
Partner: UNT Libraries Government Documents Department

Conversion and Blending Facility highly enriched uranium to low enriched uranium as oxide. Revision 1

Description: This Conversion and Blending Facility (CBF) will have two missions: (1) convert HEU materials into pure HEU oxide and (2) blend the pure HEU oxide with depleted and natural uranium oxide to produce an LWR grade LEU product. The primary emphasis of this blending operation will be to destroy the weapons capability of large, surplus stockpiles of HEU. The blended LEU product can only be made weapons capable again by the uranium enrichment process. To the extent practical, the chemical and isotopic concentrations of blended LEU product will be held within the specifications required for LWR fuel. Such blended LEU product will be offered to the United States Enrichment Corporation (USEC) to be sold as feed material to the commercial nuclear industry. Otherwise, blended LEU will be produced as a waste suitable for storage or disposal.
Date: July 5, 1995
Partner: UNT Libraries Government Documents Department