70 Matching Results

Search Results

Advanced search parameters have been applied.

Non-evaluation applications for covariance matrices

Description: The possibility for application of covariance matrix techniques to a variety of common research problems other than formal data evaluation are demonstrated by means of several examples. These examples deal with such matters as fitting spectral data, deriving uncertainty estimates for results calculated from experimental data, obtaining the best values for plurally-measured quantities, and methods for analysis of cross section errors based on properties of the experiment. The examples deal with realistic situations encountered in the laboratory, and they are treated in sufficient detail to enable a careful reader to extrapolate the methods to related problems.
Date: May 1, 1982
Creator: Smith, D.L.
Partner: UNT Libraries Government Documents Department

Lithium corrosion/mass transfer test facility

Description: Liquid lithium is a leading candidate as a tritium breeding material for fusion reactors because of its good breeding and heat-transfer characteristics. This paper describes a new experimental facility for investigating the corrosion/mass transfer/deposition mechanisms at characteristic velocities and system temperatures. This test facility, which is constructed of ferritic/martensitic steel (Fe-9Cr-1Mo), simulates conditions projected for a liquid metal heat transport system. The test facility will provide test velocities to 0.5 m/s, and temperatures to 550/degree/C, and system ..delta..T's up to 150/degree/C. The corrosion test region simulates the blanket region with a low inlet temperature and a higher (..delta..T /approximately/ 150/degree/C) outlet temperature. Test specimens in the deposition region provide a measure of the deposition processes that will occur in a heat exchanger as the liquid metal is cooled (..delta..T /approximately/ 150/degree/C). In addition to temperature and flow control, the facility provides for control and monitoring of impurities in the liquid.
Date: February 1, 1988
Creator: Smith, D.L.; Chopra, O.K. & Hull, A.B.
Partner: UNT Libraries Government Documents Department

Microstructural examination of fast-neutron irradiated Li/sub 2/O

Description: Scanning Electron Microscopy examinations of fast-neutron irradiated Li/sub 2/O at 608 to 625/sup 0/C to 1 and 3 at. % /sup 6/Li burnups have been performed. Of particular interests are the helium bubble morphologies and their relationships to the reported tritium/helium retentions and swelling in Li/sub 2/O. Possible defect trapping of tritium is suggested, along with discussions of two other phenomena (microcracking, swelling) on the performance of an Li/sub 2/O fusion reactor blanket.
Date: October 1, 1984
Creator: Liu, Y.Y.; Mattas, R.F.; Smith, D.L. & Porter, D.L.
Partner: UNT Libraries Government Documents Department

Nuclear data uncertainties: I, Basic concepts of probability

Description: Some basic concepts of probability theory are presented from a nuclear-data perspective, in order to provide a foundation for thorough understanding of the role of uncertainties in nuclear data research. Topics included in this report are: events, event spaces, calculus of events, randomness, random variables, random-variable distributions, intuitive and axiomatic probability, calculus of probability, conditional probability and independence, probability distributions, binomial and multinomial probability, Poisson and interval probability, normal probability, the relationships existing between these probability laws, and Bayes' theorem. This treatment emphasizes the practical application of basic mathematical concepts to nuclear data research, and it includes numerous simple examples. 34 refs.
Date: December 1, 1988
Creator: Smith, D.L.
Partner: UNT Libraries Government Documents Department

Fast-neutron-spectrum measurements for the thick-target /sup 9/Be(d,n)/sup 10/B reaction at E/sub d/ = 7 MeV

Description: Spectra of neutrons with energies greater than or equal to 800 keV which are emitted from a metallic beryllium target that is thick enough to completely stop 7-MeV incident deuterons are measured using organic scintillators and the pulse-beam time-of-flight method. Data are acquired for twenty different emission angles in the laboratory over the range 0 to 155 degrees. The resulting information on the energy-angle detail of neutron emission is then employed in calculations which are performed in order to examine certain effects of the anisotropic neutron production on typical measurements of integral fast-neutron reaction cross sections. 28 refs.
Date: April 1, 1985
Creator: Smith, D.L.; Meadows, J.W. & Guenther, P.T.
Partner: UNT Libraries Government Documents Department

Influence of temperature and lithium purity on corrosion of ferrous alloys in a flowing lithium environment

Description: Corrosion data have been obtained on ferritic HT-9 and Fe-9Cr-1Mo steel and austenitic Type 316 stainless steel in a flowing lithium environment at temperatures between 372 and 538/sup 0/C. The corrosion behavior is evaluated by measurements of weight loss as a function of time and temperature. A metallographic characterization of materials exposed to a flowing lithium environment is presented.
Date: March 1, 1986
Creator: Chopra, O.K. & Smith, D.L.
Partner: UNT Libraries Government Documents Department

Modeling of liquid-metal corrosion/deposition in a fusion reactor blanket

Description: A model has been developed for the investigation of the liquid-metal corrosion and the corrosion product transport in a liquid-metal-cooled fusion reactor blanket. The model describes the two-dimensional transport of wall material in the liquid-metal flow and is based on the following assumptions: (1) parallel flow in a straight circular tube; (2) transport of wall material perpendicular to the flow direction by diffusion and turbulent exchange; in flow direction by the flow motion only; (3) magnetic field causes uniform velocity profile with thin boundary layer and suppresses turbulent mass exchange; and (4) liquid metal at the interface is saturated with wall material. A computer code based on this model has been used to analyze the corrosion of ferritic steel by lithium lead and the deposition of wall material in the cooler part of a loop. Three cases have been investigated: (1) ANL forced convection corrosion experiment (without magnetic field); (2) corrosion in the MARS liquid-metal-cooled blanket (with magnetic field); and (3) deposition of wall material in the corrosion product cleanup system of the MARS blanket loop.
Date: April 1, 1984
Creator: Malang, S. & Smith, D.L.
Partner: UNT Libraries Government Documents Department

Strength, ductility, and ductile-brittle transition temperature for MFR (magnetic fusion reactor) candidate vanadium alloys

Description: The dependence of the yield strength, tensile strength, elongation, and reduction in area on temperature for the V-15Ti-7.5Cr, V-20Ti, V-15Cr-5Ti, V-12Cr-5Ti, V-10Cr-5Ti, and V-3Ti-1Si alloys was determined from tensile tests at temperatures ranging from 25 to 700/sup 0/C. The strength of the alloys increased with an increase of the combined Cr and Ti concentration. The total elongation for the alloys ranged between 20% and 38%. The reduction in area ranged from 30% to 90%. The DBTT, which was determined from the temperature dependence of the reduction in area, was less than 25/sup 0/C for the V-15Ti-7.5Cr, V-20Ti, and V-3Ti-1Si alloys. The DBTT for the V-10Cr-5Ti, V-12Cr-5Ti, and V-15Cr-5Ti alloys was also less than 25/sup 0/C if these alloys were annealed to reduce the hydrogen concentration prior to the tensile test. If these latter alloys were not annealed prior to the tensile test, the DBTT ranged from 40/sup 0/C to 90/sup 0/C and the DBTT increased with an increase of the Cr concentration. A Cr/Ti concentration ratio of 0 to 0.5 in these alloys was found to cause the alloys to be less susceptible to hydrogen embrittlement. 14 refs., 4 figs., 3 tabs.
Date: September 1, 1987
Creator: Loomis, B.A.; Lee, R.H.; Smith, D.L. & Peterson, J.R.
Partner: UNT Libraries Government Documents Department

Vanadium-base alloys for fusion reactor applications

Description: Vanadium-base alloys offer potentially significant advantages over other candidate alloys as a structural material for fusion reactor first wall/blanket applications. Although the data base is more limited than that for the other leading candidate structural materials, viz., austenitic and ferritic steels, vanadium-base alloys exhibit several properties that make them particularly attractive for the fusion reactor environment. This paper presents a review of the structural material requirements, a summary of the materials data base for selected vanadium-base alloys, and a comparison of projected performance characteristics compared to other candidate alloys. Also, critical research and development (R and D) needs are defined.
Date: October 1, 1984
Creator: Smith, D.L.; Loomis, B.A. & Diercks, D.R.
Partner: UNT Libraries Government Documents Department

Investigation of the influence of the neutron spectrum in determinations of integral cross-section ratios

Description: Ratio measurements are routinely employed in studies of neutron interaction processes in order to generate new differential cross-section data or to test existing differential cross-section information through examination of the corresponding response in integral neutron spectra. Interpretation of such data requires that careful attention be given to details of the neutron spectra involved in these measurements. Two specific tasks are undertaken in the present investigation: (1) Using perturbation theory, a formula is derived which permits one to relate the ratio measured in a realistic quasimonoenergetic spectrum to the desired pure monoenergetic ratio. This expression involves only the lowest-order moments of the neutron energy distribution and corresponding parameters which serve to characterize the energy dependence of the differential cross sections, quantities which can generally be estimated with reasonable precision from the uncorrected data or from auxiliary information. (2) Using covariance methods, a general formalism is developed for calculating the uncertainty of a measured integral cross-section ratio which involves an arbitrary neutron spectrum. This formalism is employed to further examine the conditions which influence the sensitivity of such measured ratios to details of the neutron spectra and to their uncertainties. Several numerical examples are presented in this report in order to illustrate these principles, and some general conclusion are drawn concerning the development and testing of neutron cross-section data by means of ratio experiments. 16 refs., 1 fig., 4 tabs.
Date: November 1, 1987
Creator: Smith, D.L.
Partner: UNT Libraries Government Documents Department

Partitioning of hydrogen in the vanadium-lithium-hydrogen system at elevated temperatures

Description: Equilibrium concentrations of hydrogen in vanadium-base alloys exposed to flowing lithium at temperatures from 350 to 550/degree/C in a forced-circulation loop were measured by residual gas analysis and the vacuum fusion method. Residual gas analysis and removal of material from the surface allowed a determination of the spatial hydrogen distribution in the alloys. These experimental results were compared with calculated thermodynamic distribution coefficients for hydrogen in the vanadium/lithium system. Small amounts of other solutes in the molten lithium and in the alloys affected the solubility, diffusivity, and resultant distribution of hydrogen. Thermodynamic calculations demonstrated the importance of major alloying elements to the partitioning of hydrogen. 12 refs., 5 figs., 2 tabs.
Date: September 1, 1988
Creator: Hull, A.B.; Chopra, O.K.; Loomis, B.A. & Smith, D.L.
Partner: UNT Libraries Government Documents Department

Stress-corrosion cracking susceptibility of V-15Cr-5Ti in pressurized water at 288/sup 0/C

Description: The stress-corrosion cracking susceptibility of V-15Cr-5Ti in pressurized water at 288/sup 0/C has been evaluated by means of constant extension rate tensile (CERT) tests in a refreshed autoclave system. The test environments included high-purity water as well as water containing SO/sub 4//sup 2 -/ and NO/sub 3//sup -/ impurities at a concentration of 10 wppM. Strain rates from 1 x 10/sup -6/ to 5 x 10/sup -8/ s/sup -1/ were employed, and dissolved oxygen levels ranged from <0.005 to 7.9 wppM. Test times were from 3.2 to 619 h. No stress corrosion cracking was observed under any of the test conditions. These results were analyzed using measured electrochemical potentials, available Pourbaix diagram information, and the observed oxidation behavior. 7 refs., 5 figs., 1 tab.
Date: July 1, 1987
Creator: Diercks, D.R. & Smith, D.L.
Partner: UNT Libraries Government Documents Department

Neutron source investigations in support of the cross section program at the Argonne Fast-Neutron Generator

Description: Experimental methods related to the production of neutrons for cross section studies at the Argonne Fast-Neutron Generator are reviewed. Target assemblies commonly employed in these measurements are described, and some of the relevant physical properties of the neutron source reactions are discussed. Various measurements have been performed to ascertain knowledge about these source reaction that is required for cross section data analysis purposes. Some results from these studies are presented, and a few specific examples of neutron-source-related corrections to cross section data are provided. 16 figures, 3 tables.
Date: May 1, 1980
Creator: Meadows, J.W. & Smith, D.L.
Partner: UNT Libraries Government Documents Department

Evaluated nuclear-data file for niobium

Description: A comprehensive evaluated nuclear-data file for elemental niobium is provided in the ENDF/B format. This file, extending over the energy range 10/sup -11/-20 MeV, is suitable for comprehensive neutronic calculations, particulary those dealing with fusion-energy systems. It also provides dosimetry information. Attention is given to the internal consistancy of the file, energy balance, and the quantitative specification of uncertainties. Comparisons are made with experimental data and previous evaluated files. The results of integral tests are described and remaining outstanding problem areas are cited. 107 refs.
Date: March 1, 1985
Creator: Smith, A.B.; Smith, D.L. & Howerton, R.J.
Partner: UNT Libraries Government Documents Department

Tokamak power systems studies, FY 1985

Description: The Tokamak Power System Studies (TPSS) at ANL in FY-1985 were devoted to exploring innovative design concepts which have the potential for making substantial improvements in the tokamak as a commercial power reactor. Major objectives of this work included improved reactor economics, improved environmental and safety features, and the exploration of a wide range of reactor plant outputs with emphasis on reduced plant sizes compared to STARFIRE. The activities concentrated on three areas: plasma engineering, impurity control, and blanket/first wall/shield technology. 205 refs., 125 figs., 107 tabs.
Date: December 1985
Creator: Baker, C. C.; Brooks, J. N.; Ehst, D. A.; Smith, D. L. & Sze, D. K.
Partner: UNT Libraries Government Documents Department

Corrosion behavior of vanadium alloys in flowing lithium

Description: Corrosion data are presented for several vanadium alloys exposed to flowing lithium at 427, 482, and 538/sup 0/C. The corrosion behavior is evaluated by weight change measurements. Metallographic results and data on the nonmetallic element transfer in lithium-exposed specimens are also presented. The influence of alloy composition and exposure conditions on the corrosion behavior of vanadium alloys is discussed. 6 refs., 9 figs., 2 tabs.
Date: August 1, 1987
Creator: Chopra, O.K. & Smith, D.L.
Partner: UNT Libraries Government Documents Department

INTOR first wall/blanket/shield activity

Description: The main emphasis of the INTOR first wall/blanket/shield (FWBS) during this period has been upon the tritium breeding issues. The objective is to develop a FWBS concept which produces the tritium requirement for INTOR operation and uses a small fraction of the first wall surface area. The FWBS is constrained by the dimensions of the reference design and the protection criteria required for different reactor components. The blanket extrapolation to commercial power reactor conditions and the proper temperature for power extraction have been sacrificed to achieve the highest possible local tritium breeding ratio (TBR). In addition, several other factors that have been considered in the blanket survey study include safety, reliability, lifetime fluence, number of burn cycles, simplicity, cost, and development issues. The implications of different tritium supply scenarios were discussed from the cost and availability for INTOR conditions. A wide variety of blanket options was explored in a preliminary way to determine feasibility and to see if they can satisfy the INTOR conditions. This survey and related issues are summarized in this report. Also discussed are material design requirements, thermal hydraulic considerations, structure analyses, tritium permeation through the first wall into the coolant, and tritium inventory.
Date: January 1, 1986
Creator: Gohar, Y.; Billone, M.C.; Cha, Y.S.; Finn, P.A.; Hassanein, A.M.; Liu, Y.Y. et al.
Partner: UNT Libraries Government Documents Department

Analysis of the October 5, 1979 lithium spill and fire in the Lithium Processing Test Loop

Description: On October 5, 1979, the Lithium Processing Test Loop (LPTL) developed a lithium leak in the electromagnetic (EM) pump channel, which damaged the pump, its surrounding support structure, and the underlying floor pan. A thorough analysis of the causes and consequences of the pump failure was conducted by personnel from CEN and several other ANL divisions. Metallurgical analyses of the elliptical pump channel and adjacent piping revealed that there was a significant buildup of iron-rich crystallites and other solid material in the region of the current-carrying bus bars (region of high magnetic field), which may have resulted in a flow restriction that contributed to the deterioration of the channel walls. The location of the failure was in a region of high residual stress (due to cold work produced during channel fabrication); this failure is typical of other cold work/stress-related failures encountered in components operated in forced-circulation lithium loops. Another important result was the isolation of crystals of a compound characterized as Li/sub x/CrN/sub y/. Compounds of this type are believed to be responsible for much of the Fe, Cr, and Ni mass transfer encountered in lithium loops constructed of stainless steel. The importance of nitrogen in the mass-transfer mechanism has long been suspected, but the existence of stable ternary Li-M-N compounds (M = Fe, Cr, Ni) had not previously been verified.
Date: December 1, 1981
Creator: Maroni, V.A.; Beatty, R.A.; Brown, H.L.; Coleman, L.F.; Foose, R.M.; McPheeters, C.C. et al.
Partner: UNT Libraries Government Documents Department

Compilation and evaluation of 14-MeV neutron-activation cross sections for nuclear technology applications. Set I

Description: Available 14-MeV experimental neutron activation cross sections are compiled and evaluated for the following reactions of interest for nuclear-energy technology applications: /sup 27/Al(n,p)/sup 27/Mg, Si(n,X)/sup 28/Al, Ti(n,X)/sup 46/Sc, Ti(n,X)/sup 47/Sc, Ti(n,X)/sup 48/Sc, /sup 51/V(n,p)/sup 51/Ti, /sup 51/V(n,..cap alpha..)/sup 48/Sc, Cr(n,X)/sup 52/V, /sup 55/Mn(n,..cap alpha..)/sup 52/V, /sup 55/Mn(n,2n)/sup 54/Mn, Fe(n,X)/sup 54/Mn, /sup 54/Fe(n,..cap alpha..)/sup 51/Cr, /sup 59/Co(n,p)/sup 59/Fe, /sup 59/Co(n,..cap alpha..)/sup 56/Mn, /sup 59/Co(n,2n)/sup 58/Co, /sup 65/Cu(n,p)/sup 65/Ni, Zn(n,X)/sup 64/Cu, /sup 64/Zn(n,2n)/sup 63/Zn, /sup 113/In(n,n')/sup 113m/In, /sup 115/In(n,n') /sup 115m/In. The compiled values are listed and plotted for reference without adjustments. From these collected results those values for which adequate supplementary information on nuclear constants, standards and experimental errors is provided are selected for use in reaction-by-reaction evaluations. These data are adjusted as needed to account for recent revisions in the nuclear constants and cross section standards. The adjusted results are subsequently transformed to equivalent cross sections at 14.7 MeV for the evaluation process. The evaluations are performed utilizing a least-squares method which considers correlations between the experimental data. 440 refs., 41 figs., 46 tabs.
Date: April 1, 1985
Creator: Evain, B.P.; Smith, D.L. & Lucchese, P.
Partner: UNT Libraries Government Documents Department

Covariances for neutron cross sections calculated using a regional model based on local-model fits to experimental data

Description: We suggest a procedure for estimating uncertainties in neutron cross sections calculated with a nuclear model descriptive of a specific mass region. It applies standard error propagation techniques, using a model-parameter covariance matrix. Generally, available codes do not generate covariance information in conjunction with their fitting algorithms. Therefore, we resort to estimating a relative covariance matrix a posteriori from a statistical examination of the scatter of elemental parameter values about the regional representation. We numerically demonstrate our method by considering an optical-statistical model analysis of a body of total and elastic scattering data for the light fission-fragment mass region. In this example, strong uncertainty correlations emerge and they conspire to reduce estimated errors to some 50% of those obtained from a naive uncorrelated summation in quadrature. 37 references.
Date: November 1, 1983
Creator: Smith, D.L. & Guenther, P.T.
Partner: UNT Libraries Government Documents Department

Covariance matrices and applications to the field of nuclear data

Description: A student's introduction to covariance error analysis and least-squares evaluation of data is provided. It is shown that the basic formulas used in error propagation can be derived from a consideration of the geometry of curvilinear coordinates. Procedures for deriving covariances for scaler and vector functions of several variables are presented. Proper methods for reporting experimental errors and for deriving covariance matrices from these errors are indicated. The generalized least-squares method for evaluating experimental data is described. Finally, the use of least-squares techniques in data fitting applications is discussed. Specific examples of the various procedures are presented to clarify the concepts.
Date: November 1, 1981
Creator: Smith, D.L.
Partner: UNT Libraries Government Documents Department

Heat-flow reconnaissance of the Gulf Coastal Plain

Description: Most of the 46 new values of heat flow determined for the Gulf Coastal Plain are in the low to normal range, but heat-flow values averaging 1.8 heat-flow unit (HFU) were obtained in Claiborne, Ouachita, and Union parishes, Louisiana. Moreover, a zone of relatively high heat-flow values and steep thermal gradients (35 to 46/sup 0/C/km) extends from northern Louisiana into southwestern Mississippi. Also near Pensacola, Florida, temperatures of 50/sup 0/C at 1-km depth have been extrapolated from thermal gradients. Future development of low-grade geothermal resources may be warranted in these areas.
Date: April 1, 1982
Creator: Smith, D.L. & Shannon, S.S. Jr.
Partner: UNT Libraries Government Documents Department

Application of high temperature ceramic superconductors (CSC) to commercial tokamak reactors

Description: Ceramic superconductors operating near liquid nitrogen temperature may experience higher heating rates without losing stability, compared to conventional superconductors. This will permit cable design with less stabilizer, reducing fabrication costs for large fusion magnets. Magnet performance is studied for different operating current densities in the superconductor, and cost benefits to commercial tokamak reactors are estimated. It appears that 10 kA . cm/sup -2/ (at 77 K and approx.10 T) is a target current density which must be achieved in order for the ceramic superconductors to compete with conventional materials. At current densities around 50 kA . cm/sup -2/ most potential benefits have already been gained, as magnet structural steel begins to dominate the cost at this point. For a steady state reactor reductions of approx.7% are forecast for the overall capital cost of the power plant in the best case. An additional approx.3% cost saving is possible for pulsed tokamaks. 9 refs., 4 figs., 8 tabs.
Date: October 1, 1987
Creator: Ehst, D.A.; Kim, S.; Gohar, Y.; Turner, L.; Smith, D.L. & Mattas, R.
Partner: UNT Libraries Government Documents Department

Experimental method for investigating helium effects in irradiated vanadium

Description: Analyses have been performed which indicate that an effective method for experimentally investigating helium effects in neutron irradiated vanadium base alloys can be developed. The experimental procedure involves only modest modifications to existing procedures currently used for irradiation testing of vanadium-base alloys in the FFTF reactor. Helium is generated in the vanadium alloy by decay of tritium which is either preinjected or generated within the test capsule. Calculations indicate that nearly constant He/dpa ratios of desired magnitude can be attained by proper selection of experimental parameters. The proposed method could have a major impact on the development of vanadium base alloys for fusion reactor applications. 8 refs., 4 figs.
Date: October 1, 1987
Creator: Smith, D.L.; Matsui, H.; Greenwood, L. & Loomis, B.
Partner: UNT Libraries Government Documents Department