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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

A new method for fast neutron dosimetry with a circulating liquid

Description: A new approach to fast-neutron dosimetry is described. It involves circulating a liquid with dissolved chemicals between a localized neutron field and a remote area where neutron-induced radioactivities are measured continuously. This approach employs reactions which generate relatively short-lived radioactive byproducts. Sensitivity to the neutron energy spectrum is achieved by choosing several reactions with differing thresholds. Neutron field strengths and their time variations can be derived from experimental data using the known radioactive-decay properties, cross sections, detector efficiencies, liquid flow rates and composition of the liquid. The concept has been demonstrated by measurements which utilized an aqueous solution of yttrium chloride hexahydrate, a 14-MeV neutron generator and Ge gamma-ray detectors. The {sup 16}O(n,p){sup 16}N, {sup 37}Cl(n,p){sup 37}S and {sup 89}Y(n,n{prime}){sup 89m}Y activation reactions served as dosimeters.
Date: October 1, 1996
Creator: Smith, D.L.; Ikeda, Y.; Uno, Y. & Maekawa, F.
Partner: UNT Libraries Government Documents Department

Explosives detection studies using Fast-Neutron Transmission Spectroscopy

Description: Fast-Neutron Transmission Spectroscopy (FNTS) is being investigated for detection of explosives in luggage or air cargo. We present here the principle results of a two-year study of a few-view tomographic FNTS system using the Monte Carlo radiation transport code MCNP to simulate neutron transmission through simple luggage phantoms and Receiver Operator Characteristic (ROC) curves to determine system performance. Elemental distributions along projections through the interrogated object are obtained by analyzing MCNP generated neutron transmission data. Transmission data for few (3-5) angles and relatively coarse resolution ({approximately}2 cm) are used to create a tomographic reconstruction of elemental distributions within the object. The elemental unfolding and tomographic reconstruction algorithms and the concept of transmission-derived cross sections for use in elemental analysis have been validated by application to experimental data. Elemental distributions are combined in an explosives detection algorithm to provide an indication of the presence or absence of explosives. The algorithm in current use, termed the ``equivalent explosive`` algorithm, determines the quantity of explosive that can be formed using the measured amount of the constituent elements in each pixel. Reconstruction and explosives detection algorithms have been applied to a series of randomly packed suitcases to generated ROC that describe system performance in terms of the probability of detection and of false alarms. System studies have been performed to study the operational characteristics and limitations of a FNTS system, and to determine the system`s sensitivity to several important parameters such as neutron source reaction and incident particle energy, flight path length, and the position of the interrogated object.
Date: December 1996
Creator: Fink, C. L.; Micklich, B. J.; Sagalovsky, L.; Smith, D. L. & Yule, T. J.
Partner: UNT Libraries Government Documents Department

The fabrication of a vanadium-stainless steel test section for MHD testing of insulator coatings in flowing lithium

Description: To test the magnetohydrodynamic (MHD) pressure drop reduction performance of candidate insulator coatings for the ITER Vanadium/Lithium Breeding Blanket, a test section comprised of a V- 4Cr-4Ti liner inside a stainless steel pipe was designed and fabricated. Theoretically, the MHD pressure drop reduction benefit resulting, from an electrically insulating coating on a vanadium- lined pipe is identical to the benefit derived from an insulated pipe fabricated of vanadium alone. A duplex test section design consisting of a V alloy liner encased in a SS pressure boundary provided protection for vanadium from atmospheric contamination during operation at high temperature and obviated any potential problems with vanadium welding while also minimizing the amount of V alloy material required. From the MHD and insulator coating- point of view, the test section outer SS wall and inner V alloy liner can be modeled simply as a wall having a sandwich construction. Two 52.3 mm OD x 2.9 m long V-alloy tubes were fabricated by Century Tubes from 64 mm x 200 mm x 1245 mm extrusions produced by Teledyne Wah Chang. The test section`s duplex structure was subsequently fabricated at Century Tubes by drawing down a SS pipe (2 inch schedule 10) over one of the 53.2 mm diameter V tubes.
Date: December 31, 1996
Creator: Reed, C.B.; Mattas, R.F.; Smith, D.L.; Chung, H.; Tsai, H.-C.; Morgan, G.D. et al.
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

Radiography studies with gamma rays produced by 14-MeV fusion neutrons

Description: Oxygen contained in pure water has been activated via the {sup 16}O(n, p){sup 16}N reaction using 14-MeV neutrons produced at a neutron generator with the {sup 3}H(d,n){sup 4}He source. Photons of 6.129 and 7.115 MeV, generated by the decay of 7.13-second {sup 16}N, were then used to demonstrate the feasibility of employing highly penetrating, nearly monoenergetic gamma rays for radiography studies of thick, dense objects composed of elements with medium to relatively high atomic numbers. A simple radiography apparatus was constructed by circulating water continuously between a position near the target of the neutron generator and a remote location where photon transmission measurements were conducted. A sodium iodide scintillator was employed to detect the photons. Pulses equivalent to photon energies smaller than 2.506 MeV (corresponding to the cascade sum of 1.333- and 1.173-MeV gamma rays from the decay of 5.271-year {sup 60}Co) were rejected by the electronics settings in order to reduce background and improve the signal-to-noise (S/N) ratio. Respectable S/N ratios on the order of 20-to-1 were achieved with this setup. Most of the background (N) could be attributed to ambient environmental radiation and cosmic-ray interactions with the lead shielding and detector. Four representative objects were examined by photon radiography in this study. This demonstrated how such - interesting features as hidden holes and discontinuities in atomic number could be easily identified from observed variations in the intensity of transmitted photons. Some advantages of this technique are described, and potential applications are suggested for a future scenario where fusion reactors are used to generate electric power and very intense sources of high-energy photons from {sup 16}N decay are continuously available as a byproduct of the reactor cooling process.
Date: December 1996
Creator: Smith, D. L.; Ikeda, Yujiro & Uno, Yoshitomo
Partner: UNT Libraries Government Documents Department

Development and testing ov danadium alloys for fusion applications

Description: V base alloys have advantages for fusion reactor first-wall and blanket structure. To screen candidate alloys and optimize a V-base alloy, physical and mechanical properties of V-Ti, V-Cr-Ti, and V-Ti- Si alloys were studied before and after irradiation in Li environment in fast fission reactors. V-4Cr-4Ti containing 500-1000 wppM Si and <1000 wppM O+N+C was investigated as the most promising alloy, and more testing is being done. Major results of the work are presented in this paper. The reference V-4Cr-4Ti had the most attractive combination of the mechanical and physical properties that are prerequisite for first-wall and blanket structures: good thermal creep, good tensile strength/ductility, high impact energy, excellent resistance to swelling, and very low ductile-brittle transition temperature before and after irradiation. The alloy was highly resistant to irradiation-induced embrittlement in Li at 420-600 C, and the effects of dynamically charged He on swelling and mechanical properties were insignificant. However, several important issues remain unresolved: welding, low-temperature irradiation, He effect at high dose and high He concentration, irradiation creep, and irradiation performance in air or He. Initial results of investigation of some of these issues are also given.
Date: October 1, 1996
Creator: Chung, H.M.; Loomis, B.A. & Smith, D.L.
Partner: UNT Libraries Government Documents Department

Contraband detection using high-energy gamma rays from {sup 16}O*

Description: High-energy monoenergetic gamma rays (6.13 and 7.12 MeV) from the decay of excited states of the {sup 16}O* nucleus are highly penetrating and thus offer potential for non-intrusive inspection of loaded containers for narcotics, explosives, and other contraband items. These excited states can be produced by irradiation of water with 14-MeV neutrons from a DT neutron generator or through the {sup 19}F(p,{alpha}){sup 16}O* reaction. Resonances in {sup 19}F(p,{alpha}){sup 16}O* at proton energies between 340 keV and 2 MeV allow use of a low-energy accelerator to provide a compact, portable gamma source of reasonable intensity. The present work provides estimates of gamma source parameters and suggests how various types of contraband could be detected. Gamma rays can be used to perform transmission or emission radiography of containers or other objects. Through the use of ({gamma}, n) and ({gamma}, fission) reactions, this technique is also capable of detecting special nuclear materials such as deuterium, lithium, beryllium, uranium, and plutonium. Analytic and Monte Carlo techniques are used to model empty and loaded container inspection for accelerator-produced gamma, radioisotope, and x-ray sources.
Date: December 1, 1996
Creator: Micklich, B.J.; Fink, C.L.; Sagalovsky, L. & Smith, D.L.
Partner: UNT Libraries Government Documents Department

Helium behavior in vanadium-based alloys irradiated in the dynamic helium charging experiments

Description: Helium effect of neutron irradiated vanadium alloys, containing titanium, has been studied using Dynamic Helium Charging Experiment (DHCE) in FFTF. Cavity formation was observed only in pure vanadium irradiated at 430 to 600 C and in V-5Ti irradiated at 600 C. No apparent cavity formation was obtained in V-3Ti-1Si and V-4Cr-4Ti. The precipitation of titanium oxide in V-5Ti, V-3Ti-1Si and V-4Cr-4Ti occurred in all irradiation conditions in this study and the precipitates of Ti{sub 5}Si{sub 3} only appeared in V-3Ti-1Si irradiated at 600 C up to 15 dpa with helium generation rate of 4 appmHe/dpa. It is suggested that titanium oxide plays an important role for suppression of cavity formation and swelling from early stage of irradiation. Detail characterization of precipitates and He effect for neutron damages in vanadium alloys are discussed here.
Date: December 31, 1996
Creator: Fukumoto, K.; Matsui, H.; Chung, H.M.; Gazda, J. & Smith, D.L.
Partner: UNT Libraries Government Documents Department

Properties of vanadium-base alloys irradiated in the dynamic helium charging experiment

Description: One property of vanadium-base alloys that is not well understood in terms of their potential use as fusion reactor structural materials is the effect of simultaneous generation of helium and neutron damage. In the present Dynamic Helium Charging Experiment (DHCE), helium was produced uniformly in the specimen at linear rates of {approx} 0.4 to 4.2 appm helium/dpa by the decay of tritium during irradiation to 18--31 dpa at 425--600 C in Li-filled capsules in a sodium-cooled fast reactor. This paper presents results of postirradiation examination and tests of microstructure and mechanical properties of V-5Ti, V-3Ti-1Si, V-8Cr-6Ti, and V-4Cr-4Ti (the latter alloy has been identified as the most promising candidate vanadium alloy). Effects of helium on tensile strength and ductility were insignificant after irradiation and testing at > 420 C. However, postirradiation ductilities at < 250 C were higher than those of the non-DHCE specimens (< 0.1 appm helium), whereas strengths were lower, indicating that different types of hardening centers are produced during DHCE and non-DHCE irradiation. Ductile-brittle transition behavior of the DHCE specimens was also determined from bend tests and fracture appearance of transmission electron microscopy (TEM) disks and broken tensile specimens. No brittle behavior was observed at temperatures > {minus}150 C in DHCE specimens. Predominantly brittle-cleavage fracture morphologies were observed only at {minus}196 C in some specimens that were irradiated to 31 dpa at 425 C during the DHCE. For the helium generation rates in this experiment ({approx} 0.4--4.2 appm He/dpa), grain-boundary coalescence of helium microcavities was negligible and intergranular fracture was not observed.
Date: February 1, 1996
Creator: Chung, H.M.; Loomis, B.A. & Smith, D.L.
Partner: UNT Libraries Government Documents Department

Some guidelines for the evaluation of nuclear data

Description: Modern data evaluation methodology draws upon basic principles from statistics. It differs from earlier ad hoc approaches which are completely subjective (e.g., eye guides to data) or are objective in a limited sense (e.g., combinations of reported data by a simple least-squares procedure without regard to correlations in the data errors or a careful scrutiny of the data included in the evaluation). In addition to utilizing more rigorous mathematical procedures, modern evaluation methodology involves taking great care to insure that the data which are being evaluated are equivalent to what has been assumed in the evaluation model and that the values are consistent with respect to the use of standards and other fundamental physical parameters. This short memorandum cannot substitute for more comprehensive treatments o the subject such as can be found in the listed references. The intent here is to provide an overview of the topic and to impress upon the reader that the evaluation of data of any sort is not a straightforward enterprise. Certainly evaluations cannot be carried out automatically with computer codes without considerable intervention on the part of the evaluator.
Date: March 20, 1996
Creator: Smith, D.L.
Partner: UNT Libraries Government Documents Department