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An Investigation of Positrons Interacting With Solid Argon, Krypton and Xenon

Description: With this article we intend to shed some light on all the important characteristics of the up-to-date most efficient positron moderators, the rare gas solids. We stress on the importance of the impurities in the performance of the solid rare gas moderators. The impurity factor is linked with the crystalline changes to explain the effect of annealing, and demonstrate the role of impurities in the endurance. Significant increase in the low energy positron yield is observed after repeated anneals.… more
Date: October 1, 1996
Creator: Petkov, M. P.; Roellig, L. O.; Troev, T. D. & Lynn, K. G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Split-target neutronics and the MLNSC spallation target system

Description: The Manuel Lujan, Jr., Neutron Scattering Center (MLNSC) at the Los Alamos National Laboratory is one of four operating Short-Pulse Spallation Sources worldwide. The MLNSC target system (composed of targets, moderators, and reflectors) was first installed in 1985. The target system employs a split tungsten spallation target with a void space in between (the flux-trap gap); this target system will be upgraded in 1998. The ability to efficiently split a spallation target allowed us to introduce t… more
Date: December 31, 1996
Creator: Russell, G. J.; Ferguson, P. D.; Pitcher, E. J. & Court, J. D.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Workshop: Research and development plans for high power spallation neutron testing at BNL

Description: This report consists of vugraphs from presentations at the meeting. The papers covered the following topics: (1) APS as a proton source; (2) target status for NSNS (National Spallation Neutron Source); (3) spallation neutron source in Japan; (4) liquid LiBi flow loop; and (5) research and development plans for high power tests at the AGS.
Date: August 5, 1996
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Radiation shielding and patient organ dose study for an accelerator- based BNCT Facility at LBNL

Description: This study considers the radiation safety aspects of several designs discussed in a previous report of an accelerator-based source of neutrons, based on the [sup 7]Li(p,n) reaction, for a Boron Neutron Capture Therapy (BNCT) Facility at Lawrence Berkeley National Laboratory (LBNL). determines the optimal radiation shield thicknesses for the patient treatment room. Since this is an experimental facility no moderator or reflector is considered in the bulk wall shield design. This will allow the f… more
Date: October 1996
Creator: Costes, S. V.; Vujic, J. & Donahue, R. J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Criticality safety of low-density storage arrays

Description: This note proposes a straightforward and simple method for the criticality safety analysis of fissionable materials configured into large arrays of standard containers. While criticality-safe storage limits have been well-established for standard containers--even under flooded conditions, it is also necessary to rule out the potential for criticality arising from neutronic interactions among multiple containers that might build up over long distances in a large array. Traditionally, the array p… more
Date: May 1, 1996
Creator: Bauer, T.H.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Development of a standard for the moderator temperature coefficient of reactivity in water-moderated power reactors

Description: The moderator temperature coefficient of reactivity (MTC) is an important parameter in safety analyses for thermal reactors. A positive MTC can exacerbate the severity of heatup transients, while a negative MTC can worsen the severity of cooldown transients. In particular, a strongly negative MTC is the major determinate of the severity of the steamline-break accident for pressurized water reactors (PWRs). Conversely, positive and negative MTCs can mitigate the severity of cooldown and heatup t… more
Date: February 1, 1996
Creator: Mosteller, R.D.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Spallation neutron source target station issues

Description: In many areas of physics, materials and nuclear engineering, it is extremely valuable to have a very intense source of neutrons so that the structure and function of materials can be studied. One facility proposed for this purpose is the National Spallation Neutron Source (NSNS). This facility will consist of two parts: (1) a high-energy ({approximately}1 GeV) and high powered ({approximately} 1 MW) proton accelerator, and (2) a target station which converts the protons to low-energy ({le} 2 eV… more
Date: October 1, 1996
Creator: Gabriel, T.A.; Barnes, J.N. & Charlton, L.A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Experimental critical parameters of plutonium metal cylinders flooded with water

Description: Forty-nine critical configurations are reported for experiments involving arrays of 3 kg plutonium metal cylinders moderated and reflected by water. Thirty-four of these describe systems assembled in the laboratory, while 15 others are derived critical parameters inferred from 46 subcritical cases. The arrays included 2x2xN, N = 2, 3, 4, and 5, in one program and 3x3x3 configurations in a later study. All were three-dimensional, nearly square arrays with equal horizontal lattice spacings but a … more
Date: July 1, 1996
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Neutron science opportunities at pulsed spallation neutron sources

Description: Using the IPNS Upgrade plan developed at Argonne National Laboratory as a worked example of the design of a pulsed spallation neutron source, this paper explores some of the scientific applications of an advanced facility for materials science studies and the instrumentation for those purposes.
Date: December 31, 1996
Creator: Carpenter, J.M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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A Workshop on Methods for Neutron Scattering Instrument Design. Introduction and Summary

Description: The future of neutron and x-ray scattering instrument development and international cooperation was the focus of the workshop on ``Methods for Neutron Scattering Instrument Design`` September 23-25 at the E.O. Lawrence Berkeley National Laboratory. These proceedings are a collection of a portion of the invited and contributed presentations.
Date: December 31, 1996
Creator: Hjelm, Rex P.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Characteristics of long-pulse and short-pulse spallation-source targets

Description: Generation of sharp neutron pulses is the desired output of a pulsed spallation neutron source (PSNS). These pulses should be approximately 10 {mu}s. wide at half maximum, and preserve as much of the original flux as possible. A proposed PSNS has been designed to operate at an average proton beam power of 5 MW. The PSNS consists of a heavy metal target, surrounded by a reflector, and a selection of moderators. The moderators are connected to beam tubes in which the neutrons are transported to t… more
Date: March 1, 1996
Creator: Ludewig, H.; Todosow, M. & Powell, J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Design studies for a high-resolution, transportable neutron radiography/radioscopy system

Description: A preliminary design has been developed for a high-resolution, transportable neutron radiology system (TNRS) concept. The primary system requirement is taken to be a thermal neutron flux of 10[sup 6] n/(cm[sup 2]-sec) with a L/D ratio of 100. The approach is to use an accelerator-driven neutron source, with a radiofrequency quadrupole (RFQ) as the primary accelerator component. Initial concepts for all of the major components of the system have been developed,and selected key parts have been ex… more
Date: September 30, 1996
Creator: Gillespie, G.H.; Micklich, B.J. & McMichael, G.E.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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