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ALTERATION OF U(VI)-PHASES UNDER OXIDIZING CONDITIONS

Description: Uranium-(VI) phases are the primary alteration products of the UO{sub 2} in spent nuclear fuel and the UO{sub 2+x}, in natural uranium deposits. The U(VI)-phases generally form sheet structures of edge-sharing UO{sub 2}{sup 2+} polyhedra. The complexity of these structures offers numerous possibilities for coupled-substitutions of trace metals and radionuclides. The incorporation of radionuclides into U(VI)-structures provides a potential barrier to their release and transport in a geologic repository that experiences oxidizing conditions. In this study, we have used natural samples of UO{sub 2+x}, to study the U(VI)-phases that form during alteration and to determine the fate of the associated trace elements.
Date: February 21, 2006
Creator: Deditius, A.P.; Utsunomiya, S. & Ewing, R.C.
Partner: UNT Libraries Government Documents Department

Fuel Rod Cooling in Natural Uranium Reactors

Description: An analysis is presented of the transfer of heat from a cylindrical fuel rod surrounded by a fast flowing coolant in an annular duct, with maximum power output limited by fuel rod temperatures, coolant pressure drop and pumping power requirements. A method is also presented for comparing and evaluating various liquid and gaseous coolants within these limitations. The report also shows and discusses some calculated results obtained for the systems considred in the study of natural U reactors for the production of Pu and useful power (NAA-SR-137).
Date: January 28, 1952
Creator: Trilling, C.A.
Partner: UNT Libraries Government Documents Department

Civilian Power Reactor Program. Part 1. Summary of Technical and Economic Status as of 1959

Description: The current technical and economic status for each reactor concept in the Civilian Power Reactor Program is summarized. The individual techical status reports which present detailed information will be published by AEC as TID-8518. Included in this summary are: power costs for various reactor types versus coal- fired plants; construction schedule for heavy-water natural-U reactors; and annual program costs. (T.R.H.)
Date: January 1, 1960
Partner: UNT Libraries Government Documents Department

Plutonium Production Using Natural Uranium From the Front-End of the Nuclear Fuel Cycle

Description: This report explores the potential for producing weapons-grade plutonium using conventional industrial resources, oxides of natural uranium (namely UO{sub 3}), and either heavy water or reactor-grade graphite. Using established codes and data for nuclear analysis, it is demonstrated that physics-based reactor models capable of producing kilogram quantities of weapons-grade plutonium can be readily conceived. The basic assumptions and analysis approach are discussed together with the results of the analysis.
Date: August 29, 2002
Creator: Parks, C.V.
Partner: UNT Libraries Government Documents Department

Empirical Prediction of Dimensional Stability of Natural Uranium Fuel Elements

Description: Since a theoretical mechanism to explain the change in dimensions of fuel elements during irradiation has not been proven to date, an empirical approach was evaluated. This report details results of a study, by multiple correlation techniques, of the dimensional behavior of 956 fuel elements that were divided into six different groups representing different heat treatments.
Date: February 14, 2003
Creator: LeGeros, J.P.
Partner: UNT Libraries Government Documents Department

Environmental assessment: Transfer of normal and low-enriched uranium billets to the United Kingdom, Hanford Site, Richland, Washington

Description: Under the auspices of an agreement between the U.S. and the United Kingdom, the U.S. Department of Energy (DOE) has an opportunity to transfer approximately 710,000 kilograms (1,562,000 pounds) of unneeded normal and low-enriched uranium (LEU) to the United Kingdom; thus, reducing long-term surveillance and maintenance burdens at the Hanford Site. The material, in the form of billets, is controlled by DOE`s Defense Programs, and is presently stored as surplus material in the 300 Area of the Hanford Site. The United Kingdom has expressed a need for the billets. The surplus uranium billets are currently stored in wooden shipping containers in secured facilities in the 300 Area at the Hanford Site (the 303-B and 303-G storage facilities). There are 482 billets at an enrichment level (based on uranium-235 content) of 0.71 weight-percent. This enrichment level is normal uranium; that is, uranium having 0.711 as the percentage by weight of uranium-235 as occurring in nature. There are 3,242 billets at an enrichment level of 0.95 weight-percent (i.e., low-enriched uranium). This inventory represents a total of approximately 532 curies. The facilities are routinely monitored. The dose rate on contact of a uranium billet is approximately 8 millirem per hour. The dose rate on contact of a wooden shipping container containing 4 billets is approximately 4 millirem per hour. The dose rate at the exterior of the storage facilities is indistinguishable from background levels.
Date: November 1, 1995
Partner: UNT Libraries Government Documents Department

Application of the SCALE TSUNAMI Tools for the Validation of Criticality Safety Calculations Involving 233U

Description: The Radiochemical Development Facility at Oak Ridge National Laboratory has been storing solid materials containing 233U for decades. Preparations are under way to process these materials into a form that is inherently safe from a nuclear criticality safety perspective. This will be accomplished by down-blending the {sup 233}U materials with depleted or natural uranium. At the request of the U.S. Department of Energy, a study has been performed using the SCALE sensitivity and uncertainty analysis tools to demonstrate how these tools could be used to validate nuclear criticality safety calculations of selected process and storage configurations. ISOTEK nuclear criticality safety staff provided four models that are representative of the criticality safety calculations for which validation will be needed. The SCALE TSUNAMI-1D and TSUNAMI-3D sequences were used to generate energy-dependent k{sub eff} sensitivity profiles for each nuclide and reaction present in the four safety analysis models, also referred to as the applications, and in a large set of critical experiments. The SCALE TSUNAMI-IP module was used together with the sensitivity profiles and the cross-section uncertainty data contained in the SCALE covariance data files to propagate the cross-section uncertainties ({Delta}{sigma}/{sigma}) to k{sub eff} uncertainties ({Delta}k/k) for each application model. The SCALE TSUNAMI-IP module was also used to evaluate the similarity of each of the 672 critical experiments with each application. Results of the uncertainty analysis and similarity assessment are presented in this report. A total of 142 experiments were judged to be similar to application 1, and 68 experiments were judged to be similar to application 2. None of the 672 experiments were judged to be adequately similar to applications 3 and 4. Discussion of the uncertainty analysis and similarity assessment is provided for each of the four applications. Example upper subcritical limits (USLs) were generated for application 1 based on trending ...
Date: February 1, 2009
Creator: Mueller, Don; Rearden, Bradley T & Hollenbach, Daniel F
Partner: UNT Libraries Government Documents Department

FUEL ELEMENTS CONFERENCE, PARIS, NOVEMBER 18-23, 1957

Description: Papers are presented in the following major categories: applied metallurgical research, natural-uranium metallic fuel elements, enriched-uranium metallic fuel elements, nonmetallic fuel elements, corrosion of U alloys, irradiation effects on U, its alloys, and its compounds, and Pu fuel elements. (M.H.R.)
Date: October 31, 1958
Partner: UNT Libraries Government Documents Department

Fuel Temperature Coefficient of Reactivity

Description: A method for measuring the fuel temperature coefficient of reactivity in a heterogeneous nuclear reactor is presented. The method, which is used during normal operation, requires that calibrated control rods be oscillated in a special way at a high reactor power level. The value of the fuel temperature coefficient of reactivity is found from the measured flux responses to these oscillations. Application of the method in a Savannah River reactor charged with natural uranium is discussed.
Date: July 31, 2001
Creator: Loewe, W.E.
Partner: UNT Libraries Government Documents Department

ANL pre analysis of the SHEBA/CERES experiments.

Description: The French and British nuclear programs have prepared a series of natural uranium oxide fuel samples spiked with small amounts of the individual fission products which makeup a large fraction of the total neutron absorption by fission products in spent nuclear fuel. Both programs have utilized these samples in experimental reactors and have inferred the worth of the individual fission products. These results have been used to validate the cross sections used in criticality safety calculations. These measurements constitute a major element in support of spent fuel burnup credit in these countries.
Date: May 5, 2000
Creator: Palmiotti, G.; Smith, M.; Klann, R.; Fujita, E. & Imel, G.
Partner: UNT Libraries Government Documents Department

Plutonium and Uranium Atom Ratios and Activity Levels in Cochiti Lake Bottom Sediments Provided by Pueblo de Cochiti

Description: Historical operations at the Los Alamos National Laboratory have contaminated stream sediments with plutonium and other radionuclides. A small portion of these contaminated sediments has been carried by floods into the Rio Grande drainage system, eventually to be trapped by Cochiti Lake located on Pueblo de Cochiti lands approximately 8 km downstream of the Laboratory. In this study, lake bottom sediment samples provided by the Pueblo de Cochiti were analyzed by thermal ionization mass spectrometry to determine plutonium and uranium activity levels and isotopic atom ratios. This specialized analytical method allows us to take isotopic fingerprints of radionuclides found in the sediment and to determine how much plutonium and uranium came from the Laboratory and how much was deposited by worldwide fallout or is natural. Two distinct types of samples were processed: segments of a continuous vertical core of the entire accumulated sediment sequence and other samples from across the lake bottom at the water/sediment interface. Based on measurement of the {sup 240}Pu/{sup 239}Pu atom ratio, Laboratory-derived plutonium is present in eight of nine samples at the core site. On a depth-weighted basis, approximately one-half of the {sup 239}Pu and {sup 240}Pu came from early operations at the Laboratory; the remaining plutonium came from fallout dispersed by above-ground nuclear tests. In contrast to the core site, the samples from the other locations showed little or no evidence of Laboratory-derived plutonium, with more than 90 percent of the plutonium attributable to fallout. The overall amount of plutonium in all the samples is of the same magnitude as other reservoirs in the region. The net increase in plutonium over upstream reservoirs unaffected by Laboratory activities is a maximum of 0.014 pCi/g or 3.5 times. All of the samples reflect natural uranium compositions. Laboratory-derived uranium is not identifiable, presumably because the sediment contains ...
Date: May 1, 1999
Creator: Gallaher, B.M.; Efurd, D.W.; Rokop, D.J. & Benjamin, T.M.
Partner: UNT Libraries Government Documents Department

Isotopic signatures: An important tool in today`s world

Description: High-sensitivity/high-accuracy actinide measurement techniques developed to support weapons diagnostic capabilities at the Los Alamos National Laboratory are now being used for environmental monitoring. The measurement techniques used are Thermal Ionization Mass Spectrometry (TIMS), Alpha Spectrometry(AS), and High Resolution Gamma Spectrometry(HRGS). These techniques are used to address a wide variety of actinide inventory issues: Environmental surveillance, site characterizations, food chain member determination, sedimentary records of activities, and treaty compliance concerns. As little as 10 femtograms of plutonium can be detected in samples and isotopic signatures determined on samples containing sub-100 femtogram amounts. Uranium, present in all environmental samples, can generally yield isotopic signatures of anthropogenic origin when present at the 40 picogam/gram level. Solid samples (soils, sediments, fauna, and tissue) can range from a few particles to several kilograms in size. Water samples can range from a few milliliters to as much as 200 liters.
Date: December 1, 1995
Creator: Rokop, D.J.; Efurd, D.W.; Benjamin, T.M.; Cappis, J.H.; Chamberlin, J.W.; Poths, H. et al.
Partner: UNT Libraries Government Documents Department

HEAVY-WATER-MODERATED POWER REACTORS ENGINEERING AND ECONOMIC EVALUATIONS. VOLUME I. SUMMARY REPORT

Description: Capital investments and the cost of power were estimated for 21 heavy- water-moderated, natural-uraniumfueled power-reactor plants, ranging in capacity from 100 to 460 Mw(e). Comparisons were made of hot- and coldmoderator reactors and of the relative merits of pressuretube and pressure-vessel designs. Reactors cooled with liquid D/sub 2/O, boiling D/sub 2/O, /sub 2/O steam, and helium were evalunted. A cold-moderator pressure-tube reactor cooled with boiling D/sub 2/O shows the most economic promise of the D/sub 2/Omoderated reactor systems studied to date. Reactors of this type have sufficient reactivity to permit satisfactory fuel exposures, but the development of additional technology is a prerequisite for optimum designs. At capacities of 300 and 400 Mw(e), the estimated power costs from the current designs of boiling-D/sub 2/O pressure-tabe reactor plants are 11.3 and 9.8 mills/kwh, respectively. From liquid-D/sub 2/-cooled concepts of comparable capacities the indicated power costs are 7 to 20% higher. With an active development program, a power cost of 8.0 to 8.5 mills/kwh may be attained in a 300 Mw(e) boiling-D/sub 2/O reactor plant within the next decade. (auth)
Date: June 1, 1960
Partner: UNT Libraries Government Documents Department

HEAVY-WATER-MODERATED POWER REACTORS ENGINEERING AND ECONOMIC EVALUATIONS. VOLUME II. ENGINEERING STUDIES AND TECHNICAL DATA

Description: The results of preliminary design and evaluation studies of various concepts of a power reactor that is moderated by heavy water and fueled with natural uranium are presented. Twenty-nine conceptal designs were developed for reactors ranging in capacity from 100 Mwe to 460 Mwe. Resigns were prepared for hot- and cold-moderator reac tors of the pressure vessel type, with liquid D/sub 2/O, boiling D/sub 2/O, E/sub 2/O steam, and helium as coolants. Also studied were cold-moderator pressure tube reactors cooled with liquid D/sub 2/O and boiling D/sub 2/O. The repont includes the results of engineering studies of the reactor systems, electrical generation facilities, and auxiliary equipment. (auth)
Date: December 1, 1960
Partner: UNT Libraries Government Documents Department

Radiochronological Age of a Uranium Metal Sample from an Abandoned Facility

Description: A piece of scrap uranium metal bar buried in the dirt floor of an old, abandoned metal rolling mill was analyzed using multi-collector inductively coupled plasma mass spectroscopy (MC-ICP-MS). The mill rolled uranium rods in the 1940s and 1950s. Samples of the contaminated dirt in which the bar was buried were also analyzed. The isotopic composition of uranium in the bar and dirt samples were both the same as natural uranium, though a few samples of dirt also contained recycled uranium; likely a result of contamination with other material rolled at the mill. The time elapsed since the uranium metal bar was last purified can be determined by the in-growth of the isotope {sup 230}Th from the decay of {sup 234}U, assuming that only uranium isotopes were present in the bar after purification. The age of the metal bar was determined to be 61 years at the time of this analysis and corresponds to a purification date of July 1950 {+-} 1.5 years.
Date: March 16, 2012
Creator: Meyers, L A; Williams, R W; Glover, S E; LaMont, S P; Stalcup, A M & Spitz, H B
Partner: UNT Libraries Government Documents Department

Australian Nuclear Science & Technology Organization (ANSTO) Interdicted Samples 24-Hour Report

Description: Categorization is complete. Samples 11-3-1 (NSR-F-270409-01) and 11-3-2 (NSR-F-270409-02) are depleted uranium powders of moderate purity ({approx}65-80 % U). The uranium feed stocks for 11-3-1 and 11-3-2 have both experienced a neutron flux (as demonstrated by the presence of {sup 232}U). Sample 11-3-3 is indistinguishable from a natural uranium ore concentrate of moderate purity ({approx}70-80% U). Two anomalous objects (11-3-1-4 and 11-3-2-5) were found in the material during aliquoting. These objects might be valuable for route attribution.
Date: January 27, 2011
Creator: Kristo, M J; Hutcheon, I D; Grant, P M; Borg, L E; Sharp, M A; Moody, K J et al.
Partner: UNT Libraries Government Documents Department

In-Situ Safeguards Verification of Low Burn-up Pressurized Water Reactor Spent Fuel Assemblies

Description: A novel in-situ gross defect verification method for light water reactor spent fuel assemblies was developed and investigated by a Monte Carlo study. This particular method is particularly effective for old pressurized water reactor spent fuel assemblies that have natural uranium in their upper fuel zones. Currently there is no method or instrument that does verification of this type of spent fuel assemblies without moving the spent fuel assemblies from their storage positions. The proposed method uses a tiny neutron detector and a detector guiding system to collect neutron signals inside PWR spent fuel assemblies through guide tubes present in PWR assemblies. The data obtained in such a manner are used for gross defect verification of spent fuel assemblies. The method uses 'calibration curves' which show the expected neutron counts inside one of the guide tubes of spent fuel assemblies as a function of fuel burn-up. By examining the measured data in the 'calibration curves', the consistency of the operator's declaration is verified.
Date: April 16, 2008
Creator: Ham, Y S; Sitaraman, S; Park, I; Kim, J & Ahn, G
Partner: UNT Libraries Government Documents Department

Initial Design Calculations for a Detection System that will Observe Resonant Excitation of the 680 keV state in 238U

Description: We present calculations and design considerations for a detection system that could be used to observe nuclear resonance fluorescence in {sup 238}U. This is intended as part of an experiment in which a nearly monochromatic beam of light incident on a thin foil of natural uranium resonantly populates the state at 680 keV in {sup 238}U. The beam of light is generated via Compton upscattering of laser light incident on a beam of relativistic electrons. This light source has excellent energy and angular resolution. In the current design study we suppose photons emitted following de-excitation of excited nuclei to be observed by a segmented array of BGO crystals. Monte Carlo calculations are used to inform estimates for the design and performance of this detector system. We find that each detector in this array should be shielded by about 2 cm of lead. The signal to background ratio for each of the BGO crystals is larger than ten. The probability that a single detector observes a resonant photon during a single pulse of the light source is near unity.
Date: January 26, 2007
Creator: Pruet, J. & Hagmann, C.
Partner: UNT Libraries Government Documents Department

Benchmarks for GADRAS performance validation.

Description: The performance of the Gamma Detector Response and Analysis Software (GADRAS) was validated by comparing GADRAS model results to experimental measurements for a series of benchmark sources. Sources for the benchmark include a plutonium metal sphere, bare and shielded in polyethylene, plutonium oxide in cans, a highly enriched uranium sphere, bare and shielded in polyethylene, a depleted uranium shell and spheres, and a natural uranium sphere. The benchmark experimental data were previously acquired and consist of careful collection of background and calibration source spectra along with the source spectra. The calibration data were fit with GADRAS to determine response functions for the detector in each experiment. A one-dimensional model (pie chart) was constructed for each source based on the dimensions of the benchmark source. The GADRAS code made a forward calculation from each model to predict the radiation spectrum for the detector used in the benchmark experiment. The comparisons between the GADRAS calculation and the experimental measurements are excellent, validating that GADRAS can correctly predict the radiation spectra for these well-defined benchmark sources.
Date: September 1, 2009
Creator: Mattingly, John K.; Mitchell, Dean James & Rhykerd, Charles L., Jr.
Partner: UNT Libraries Government Documents Department

Second interlaboratory comparison study for the analysis of 239Pu in synthetic urine at the microBq (-100 aCi) level by mass spectrometry

Description: As a follow up to the initial 1998 intercomparison study, a second study was initiated in 2001 as part of the ongoing evaluation of the capabilities of various ultra-sensitive methods to analyze {sup 239}Pu in urine samples. The initial study was sponsored by the Department of Energy, Office of International Health Programs to evaluate and validate new technologies that may supersede the existing fission tract analysis (FTA) method for the analysis of {sup 239}Pu in urine at the {micro}Bq/l level. The ultra-sensitive techniques evaluated in the second study included accelerator mass spectrometry (AMS) by LLNL, thermal ionization mass spectrometry (TIMS) by LANL and FTA by the University of Utah. Only the results for the mass spectrometric methods will be presented. For the second study, the testing levels were approximately 4, 9, 29 and 56 {micro}Bq of {sup 239}Pu per liter of synthetic urine. Each test sample also contained {sup 240}Pu at a {sup 240}Pu/{sup 239}Pu atom ratio of {approx}0.15 and natural uranium at a concentration of 50 {micro}Bq/ml. From the results of the two studies, it can be inferred that the best performance at the {micro}Bq level is more laboratory specific than method specific. The second study demonstrated that LANL-TIMS and LLNL-AMS had essentially the same quantification level for both isotopes. Study results for bias and precision and acceptable performance compared to ANSI N13.30 and ANSI N42.22 have been compiled.
Date: January 28, 2005
Creator: McCurdy, D; Lin, Z; Inn, K W; Bell III, R; Wagner, S; Efurd, D W et al.
Partner: UNT Libraries Government Documents Department