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Measurement and Basic Physics Committee of the US cross-section evaluation working group. Annual report 1996

Description: The Cross-Section Evaluation Working Group (CSEWG) is a long-standing committee charged with the responsibility for organizing and overseeing the U.S. cross-section evaluation effort. It`s main product is the official U.S. evaluated nuclear data file, ENDF. The current version of this file is Version VI. All evaluations included in ENDF are reviewed and approved by CSEWG and issued by the U.S. Nuclear Data Center, Brookhaven National Laboratory. CSEWG is comprised of volunteers from the U.S. nuclear data community who possess expertise in evaluation methodologies and who collectively have been responsible for producing most of the evaluations included in ENDF. In 1992 CSEWG added the Measurements Committee to its list of standing committees and subcommittees. This action was based on a recognition of the importance of experimental data in the evaluation process as well as the realization that measurement activities in the U.S. were declining at an alarming rate and needed all possible encouragement to avoid the loss of this resource. The mission of the Committee is to maintain a network of experimentalists in the U.S. that would provide needed encouragement to the national nuclear data measurement effort through improved communication and facilitation of collaborative activities. In 1994, an additional charge was added to the responsibilities of this Committee, namely, to serve as an interface between the more applied interests represented in CSEWG and the basic nuclear science community. This annual report is the second such document issued by the Committee. It contains voluntary contributions from eleven laboratories in the U.S. which have been prepared by members of the Committee and submitted to the Chairman for compilation and editing. It is hoped that the information provided here on the work that is going on at the reporting laboratories will prove interesting and stimulating to the readers.
Date: November 1, 1996
Creator: Smith, D.L. & McLane, V.
Partner: UNT Libraries Government Documents Department

Minutes of the coordination workshop on DOE nuclear data program services via the internet

Description: This workshop was convened to explore what is currently being done in the area of data dissemination via the Internet and to examine ways that future activities in this area within the U.S. nuclear data programs can be better coordinated. Overview talks on the current status, from both the national and international perspectives, were provided. Following these, there were presentations on specific activities in the area of Internet data dissemination which are taking place at seven different institutions. Institutions represented at this meeting were asked to provide written summaries of their programs before the meeting. The talks included actual demonstrations of the electronic methodologies which are under development at these laboratories, and they highlighted the richness and creativity of these programs. This information proved to be very useful in the ensuing general discussions. The main issues that were addressed at this meeting were: (i) how to adapt to rapid evolution of data management and dissemination technologies, (ii) how to provide outside users with some sense of unity in the U.S. nuclear data program and to develop consistent, user-friendly ways to access data without discouraging individual initiatives and the richness which comes from diversity, (iii) how to maintain quality control over the information and services provided, (iv) how to progress in a era of very restrictive budgets, (v) how to effectively merge the nuclear structure and nuclear reaction data dissemination activities while at the same time recognizing and respecting their inherent differences, (vi) how to organize the stewardship of nuclear data and the processes of nuclear data dissemination in an efficient, technically advanced and yet cost effective manner, and (vii) how the data processing tasks should be allocated between server and client computers.
Date: November 1, 1996
Creator: Smith, D.L. & Dunford, C.L.
Partner: UNT Libraries Government Documents Department

The effect of laser welding process parameters on the mechanical and microstructural properties of V-4CR-4TI structural materials.

Description: V-Cr-Ti alloys are among the leading candidate materials for the frost wall and other structural materials applications in fusion power reactors because of several important advantages including inherently low irradiation-induced activity, good mechanical properties, good compatibility with lithium, high thermal conductivity and good resistance to irradiation-induced swelling and damage [1]. However, weldability of these alloys in general must be demonstrated, and laser welding, specifically, must be developed. Laser welding is considered to be an attractive process for construction of a reactor due to its high penetrating power and potential flexibility. This paper reports on a systematic study which was conducted to examine the use of a pulsed Nd:YAG laser to weld sheet materials of V-Cr-Ti alloys and to characterize the microstructural and mechanical properties of the resulting joints. Deep penetration and defect-free welds were achieved under an optimal combination of laser parameters including focal length of lens, pulse energy, pulse repetition rate, beam travel speed, and shielding gas arrangement. The key for defect-free welds was found to be the stabilization of the keyhole and providing an escape path for the gas trapped in the weld. An innovative method was developed to obtain deep penetration and oxygen contamination free welds. Oxygen and nitrogen uptake were reduced to levels only a few ppm higher than the base metal by design and development of an environmental control box. The effort directed at developing an acceptable postwelding heat treatment showed that five passes of a diffuse laser beam over the welded region softened the weld material, especially in the root region of the weld.
Date: November 12, 1999
Creator: Reed, C. B.; Natesan, K.; Xu, Z. & Smith, D. L.
Partner: UNT Libraries Government Documents Department

Nuclear data needs for non-intrusive inspection.

Description: Various nuclear-based techniques are being explored for use in non-intrusive inspection. Their development is motivated by the need to prevent the proliferation of nuclear weapons, to thwart trafficking in illicit narcotics, to stop the transport of explosives by terrorist organizations, to characterize nuclear waste, and to deal with various other societal concerns. Non-intrusive methods are sought in order to optimize inspection speed, to minimize damage to packages and containers, to satisfy environmental, health and safety requirements, to adhere to legal requirements, and to avoid inconveniencing the innocent. These inspection techniques can be grouped into two major categories: active and passive. They almost always require the use of highly penetrating radiation and therefore are generally limited to neutrons and gamma rays. Although x-rays are widely employed for these purposes, their use does not constitute nuclear technology and therefore is not discussed here. This paper examines briefly the basic concepts associated with nuclear inspection and investigates the related nuclear data needs. These needs are illustrated by considering four of the methods currently being developed and tested.
Date: November 29, 2000
Creator: Smith, D. L. & Michlich, B. J.
Partner: UNT Libraries Government Documents Department

Tensile and impact properties of V-4Cr-4Ti alloy heats 832665 and 832864.

Description: Two large heats of V-4Cr-4Ti alloy were produced in the United States in the past few years. The first, 832665, was a 500 kg heat procured by the U.S. Department of Energy for basic fusion structural materials research. The second, 832864, was a 1300 kg heat procured by General Atomics for the DIII-D radiative divertor upgrade. Both heats were produced by Oremet-Wah Chang (previously Teledyne Wah Chang of Albany). Tensile properties up to 800 C and Charpy V-notch impact properties down to liquid nitrogen temperature were measured for both heats. The product forms tested for both heats were rolled sheets annealed at 1000 C for 1 h in vacuum. Testing results show the behavior of the two heats to be similar and the reduction of strengths with temperature to be insignificant up to at least 750 C. Ductility of both materials is good in the test temperature range. Impact properties for both heats are excellent--no brittle failures at temperatures above -150 C. Compared to the data for previous smaller laboratory heats of 15-50 kg, the results show that scale-up of vanadium alloy ingot production to sizes useful for reactor blanket design can be successfully achieved as long as reasonable process control is implemented.
Date: November 8, 1999
Creator: Bray, T. S.; Tsai, H.; Nowicki, L. J.; Billone, M. C.; Smith, D. L.; Johnson, W. R. et al.
Partner: UNT Libraries Government Documents Department

A compilation of information on the {sup 31}P(p,{alpha}){sup 28}Si reaction and properties of excited levels in the compound nucleus {sup 32}S

Description: This report documents a survey of the literature, and provides a compilation of data contained therein, for the {sup 31}P(p,{alpha}){sup 28}Si reaction. Attention is paid here to resonance states in the compound-nuclear system {sup 32}S formed by {sup 31}P + p, with emphasis on the alpha-particle decay channels, {sup 28}Si + {alpha} which populate specific levels in {sup 28}Si. The energy region near the proton separation energy for {sup 32}S is especially important in this context for applications in nuclear astrophysics. Properties of the excited states in {sup 28}Si are also considered. Summaries of all the located references are provided and numerical data contained in them are compiled in EXFOR format where applicable.
Date: November 1, 1997
Creator: Miller, R.E. & Smith, D.L.
Partner: UNT Libraries Government Documents Department

Performance limits of fusion first-wall structural materials.

Description: Key features of fusion energy relate primarily to potential advantages associated with safety and environmental considerations and the near endless supply of fuel. However, it is generally concluded that high performance fusion power systems will be required in order to be economically competitive with other energy options. As in most energy systems, structural materials operating limits pose a primary constraint to the performance of fusion power systems. It is also recognized that for the case of fusion power, the first-wall/blanket system will have a dominant impact on both the economic and safety/environmental attractiveness of fusion energy. The first-wall blanket structure is particularly critical since it must maintain high integrity at relatively high temperatures during exposure to high radiation levels, high surface heat fluxes, and significant primary stresses. The performance limits of the first-wall/blanket structure will be dependent on the structural material properties, the coolant/breeder system, and the specific design configuration. Key factors associated with high performance structural materials include (1) high temperature operation, (2) a large operating temperature window, and (3) a long operating lifetime. High temperature operation is necessary to provide for high power conversion efficiency. As discussed later, low-pressure coolant systems provide significant advantages. A large operating temperature window is necessary to accommodate high surface heating and high power density. The operating temperature range for the structure must include the temperature gradient through the first wall and the coolant system AT required for efficient energy conversion. This later requirement is dependent on the coolant/breeder operating temperature limits. A long operating lifetime of the structure is important to improve system availability and to minimize waste disposition.
Date: November 12, 1999
Creator: Smith, D. L.; Majumdar, S.; Billone, M. & Mattas, R. F.
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

Some comments on resolution and the analysis and interpretation of experimental results from differential neutron measurements

Description: Effects of finite resolution in differential neutron measurements are examined. General procedures for deriving the experimental resolution functions from a knowledge of the experimental parameters are presented. Problems encountered in the comparison of different data sets, when the measured cross section is known to fluctuate with energy, are discussed. The objective is to encourage closer attention to the matter of resolution by experimenters, evaluators and users of neutron nuclear data.
Date: November 1, 1979
Creator: Smith, D.L.
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

Neutronics of a D-Li neutron source: An overview

Description: The importance of having a high energy (14 MeV) neutron source for fusion materials testing is widely recognized. The availability of a test volume with easy accessibility, with a radiation environment similar to the one expected for a fusion reactor, and with dimensions large enough to accommodate several small samples or a small blanket mock-up are requirements impossible to meet with the existing reactors and irradiation facilities. A D-Li neutron source meets the above mentioned requirements and can be built today with well known technology. This paper describes some relevant topics related to beam target configuration, neutron flux spectrum, and nuclear responses for a D-Li neutron source. The target-beam configuration is analyzed for different beam cross sectional areas and trade-offs between the area of the beam and related quantities such as available volume for testing, peak fluxes, and flux or nuclear responses gradient are presented. The conclusion is that the D-Li neutron source has the necessary characteristics to be the option of choice for IFMIF.
Date: November 1, 1993
Creator: Gomes, I. C. & Smith, D. L.
Partner: UNT Libraries Government Documents Department

D-D tokamak reactor studies

Description: A tokamak D-D reactor design, utilizing the advantages of a deuterium-fueled reactor but with parameters not unnecessarily extended from existing D-T designs, is presented. Studies leading to the choice of a design and initial studies of the design are described. The studies are in the areas of plasma engineering, first-wall/blanket/shield design, magnet design, and tritium/fuel/vacuum requirements. Conclusions concerning D-D tokamak reactors are stated.
Date: November 1, 1980
Creator: Evans, K.E. Jr.; Baker, C.C.; Brooks, J.N.; Ehst, D.A.; Finn, P.A.; Jung, J. et al.
Partner: UNT Libraries Government Documents Department

Least-squares method for deriving reaction differential-cross-section information from measurements performed in diverse neutron fields

Description: A generalized least-squares algorithm which refiens a prior multi-group energy-differential neutron-reaction cross-section evaluation by addition of new experimental data is described. Complete covariance information for the prior evaluation and for the new experimentla information is required in this procedure. The result is a revised best-estimate multi-group cross-section evaluation with complete covariance information. The algorithm tests the consistency of the ew and apriori information, and it readily indicates whether the new data significantly improve the knowledge of the differential cross section. These new data need not be specific differential cross sections. Therefore, the experimenter is not limited to measurements which involve only conventional monoenergetic techniques. This opportunity suggests exploration of diverse new experimental methods, e.g., ones which can exploit the high yield and favorable neutron-energy ranges offered by certain unconventional neutron sources which have received little past attention. This method is demonstratedby the detailed analysis of several hypothetical numerical examples. The understanding of the method's potential and limitations which has emerged from the present investigation is discussed.
Date: November 1, 1982
Creator: Smith, D.L.
Partner: UNT Libraries Government Documents Department

An evaluated neutronic data file for bismuth

Description: A comprehensive evaluated neutronic data file for bismuth, extending from 10{sup {minus}5} eV to 20.0 MeV, is described. The experimental database, the application of the theoretical models, and the evaluation rationale are outlined. Attention is given to uncertainty specification, and comparisons are made with the prior ENDF/B-V evaluation. The corresponding numerical file, in ENDF/B-VI format, has been transmitted to the National Nuclear Data Center, Brookhaven National Laboratory. 106 refs., 10 figs., 6 tabs.
Date: November 1, 1989
Creator: Guenther, P.T.; Lawson, R.D.; Meadows, J.W.; Smith, A.B.; Smith, D.L.; Sugimoto, M. (Argonne National Lab., IL (USA)) et al.
Partner: UNT Libraries Government Documents Department

An evaluation of the Nb-93(n,n prime )Nb-93m dosimeter reaction for ENDF/B-VI

Description: The Nb-93(n,n{prime})Nb-93m reaction plays an important role in nuclear energy applications. Because of its low threshold energy and relatively long half-life, it is a desirable reaction for long-term neutron fluence dosimetry in nuclear fission reactors. An evaluation of the differential cross section for this reaction was completed in 1985 by this laboratory as part of a comprehensive effort involving all neutron cross sections for niobium. The objective was to provide input for ENDF/B-VI. It was difficult to produce a reliable evaluation for this reaction in 1985 because the information available then was sparse and quite uncertain. In fact, that evaluation was based entirely on nuclear model calculations. The evaluated cross sections below 0.7 MeV were derived from calculations carried out in this laboratory, while the higher energy values were obtained from the work of Strohmaier and co-workers. In 1985 there was only one published experimental differential cross section value to consider for this reaction. Even the half-life of Nb-93m was in serious doubt. During the five years between the completion of the earlier evaluation and the finalization of ENDF/B-VI there have been some significant improvements and additions to the experimental database for this reaction. Also, new model calculations have been performed. Therefore, it was considered worthwhile to produce a new evaluation of Nb-93(n,n{prime})Nb-93m for ENDF/B-VI which would supplant the one that had been completed in 1985.
Date: November 1, 1990
Creator: Smith, D.L. & Geraldo, L.P.
Partner: UNT Libraries Government Documents Department