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Nondestructive assay of fissile material samples in support of nuclear safeguards

Description: From nuclear science symposium; San Francisco, California, USA (14 Nov 1973). Samples of fissile material can be assayed by bombarding with 300- to 600- keV neutrons and counting delayed neutrons from fission. Interrogating neutron energy selection is based upon considerations of sample penetrability and insensitivity of response to nonfissile isotopes. Significant cost savings in nuclear safeguards and quality control are possible. (auth)
Date: January 1, 1973
Creator: Evans, A.E. Jr.
Partner: UNT Libraries Government Documents Department

Influence of materials and counting-rate effects on /sup 3/He neutron spectrometry

Description: The high energy resolution of the Cuttler-Shalev /sup 3/He neutron spectrometer causes spectral measurements with this instrument to be strongly susceptible to artifacts caused by the presence of scattering or absorbing materials in or near the detector or the source, and to false peaks generated by pileup coincidences of the rather long-risetime pulses from the detector. These effects are particularly important when pulse-height distributions vary over several orders of magnitude in count rate versus channel. A commercial pile-up elimination circuit greatly improves but does not eliminate the pileup problem. Previously reported spurious peaks in the pulse-height distributions from monoenergetic neutron sources have been determined to be due to the influence of the iron in the detector wall. 6 references, 9 figures.
Date: January 1, 1984
Creator: Evans, A.E.
Partner: UNT Libraries Government Documents Department

Little Boy neutron spectrum below 1 MeV

Description: A high-resolution /sup 3/He ionization chamber of the type development by Cuttler and Shalev was used to study the neutron spectrum from the Little Boy mockup. Measurements were made at distances of 0.75 and 2.0 m and at angles of 0/sup 0/, 45/sup 0/, and 90/sup 0/ with respect to the axis of the assembly, which was operated at power levels from 8.6 to 450 mW. Detector efficiency as a function of energy as well as parameters for correction of pulse-height distributions for proton-recoil and wall effects were determined from a set of response functions for monoenergetic neutrons measured at the Los Alamos 3.75-MeV Van de Graaff Accelerator Facility. Pulse-shape discrimination was used to separate /sup 3/He-recoil pulses from the pulse-height distribution. The spectrum was found to be highly structured, with peaks corresponding to minima in the total neutron cross section of iron. In particular, 15% of the neutrons above the epithermal peak in energy were found to be in the 24-keV iron window. Lesser peaks out to 700 keV are also attributable to filtering action of the weapon's heavy iron casing. Data taken using experimental proton-recoil proportional counters are compared with the high-resolution spectra.
Date: January 1, 1984
Creator: Evans, A.E.
Partner: UNT Libraries Government Documents Department

Observations on /sup 3/He neutron spectrometry

Description: The energy resolution of a /sup 3/He ionization chamber, which varies from 13 keV FWHM at 0 keV to approximately 30 keV at 1 MeV, allows abservation of false peaks due to the presence of scattering or absorbing materials and due to accidental near-coincidences of the rather long-risetime detector pulses. Pulse-risetime distributions depend on the neutron beam's angle of incidence to the detector axis; ability to separate /sup 3/He-recoil pulses from full-energy /sup 3/He(n,p) pulses diminishes for neutrons of energy greater than 1.5 MeV and incident normal to the detector axis. When high-energy neutrons are present, measurement at a grazing angle is recommended.
Date: January 1, 1985
Creator: Evans, A.E.
Partner: UNT Libraries Government Documents Department

DNA replication and the repair of DNA strand breaks in nuclei of Physarum polycephalum. Terminal report, August 1, 1978-March 31, 1980

Description: Nuclei isolated from Physarum are able to replicate approximately 15% of the total genome in a manner which is qualitatively similar to the DNA replication process occurring in the intact organism. Such nuclei, however, are defective in the joining of Okazaki intermediates in vitro. Two DNA polymerase species, isolated from nuclei or intact plasmodia of this organism, can be separated by sucrose density gradient centrifugation. Total DNA polymerase activity is low in nuclei isolated during mitosis. A heat-stable glycoprotein material present in aqueous nuclear extracts stimulates DNA synthesis in well-washed nuclei. A sub-nuclear preparation active in DNA synthesis in vitro has been obtained from isolated nuclei of Physarum. Radiation-induced DNA double-strand breaks are rejoined in intact plasmodia and isolated nuclei of Physarum in a cell cycle-dependent manner. This phenomenon does not appear to be due to an intrinsic difference in nuclear DNA endonuclease activity at different times of the mitotic cycle. DNA strand breaks and repair induced by the carcinogen 4-nitroquinoline-1-oxide is similar in several respects to that resulting from exposure of the organism to ionizing radiation. Temperature sensitive strains of Physarum have been constructed and preliminary genetical and biochemical characterizations have been carried out. Two of the strains appear to be conditionally defective in DNA metabolism. An isogenic ploidal series of amoebae has been prepared and characterized as to uv and ionizing radiation sensitivity (in terms of cell survival). There is a direct relationship between ploidy and resistance to uv whereas ploidal change does not appear to affect the response to ionizing radiation.
Date: January 1, 1980
Creator: Brewer, E.N. & Evans, T.E.
Partner: UNT Libraries Government Documents Department

Parental and children's experiences and adjustment in maternal versus joint custody families

Description: This research project assessed the advantages and disadvantages of two types of post divorce arrangements by comparing joint custody families to mother custody families. Several categories of variables were used in making this comparison including the parent child relationship, the interparental relationship, mechanics of alternations, similarities/dissimilarities of home environment, characteristics, of children, and social demographic variables.
Date: May 1991
Creator: Rockwell-Evans, Kim E. (Kim Evonne)
Partner: UNT Libraries

Use of design automation in nuclear-waste-management applications at the Radioactive Waste Management Complex of the Idaho National Engineering Laboratory

Description: This paper describes how the Waste Programs Division of EG and G is using computer aided design (CAD) and Design Automation to support present waste disposal operations and forecast near- and distant-term environmental effects. Specifically, support for disposal operations involves development of a two-dimensional graphic representation of the Radioactive Waste Management Complex (RWMC); support for environmental trend forecasting involves development of a three-dimensional graphic representation and environmental data base.
Date: January 1, 1981
Creator: Evans, D.E. & Reno, H.W.
Partner: UNT Libraries Government Documents Department

High resolution fast neutron spectrometry without time-of-flight

Description: Performance tests of a spectrometer tube of the type developed by Cuttler and Shalev show that the measurement of fast neutron spectra with this device can be made with an energy resolution previously obtainable only in large time-of-flight facilities. In preliminary tests, resolutions of 16.4 keV for thermal neutrons and 30.9 keV for 1-MeV neutrons were obtained. A broad-window pulse-shape discrimination (PSD) system is used to remove from pulse-height distributions most of the continua due to /sup 3/He-recoil events, noise, and wall effect. Use of PSD improved the energy resolution to 12.9 keV for thermal neutrons and 29.2 keV for 1-MeV neutrons. The detector is a viable tool for neutron research at nominally equipped accelerator laboratories.
Date: January 1, 1978
Creator: Evans, A.E. & Brandenberger, J.D.
Partner: UNT Libraries Government Documents Department

The influence of pressure on solute retention in liquid chromatography

Description: In this investigation, multiple on-column detectors are utilized to measure the retention of model solutes directly on a packed, capillary column. The absolute pressure on the column is controlled using a restrictor at the column exit, while the pressure gradient and volumetric flowrate are maintained constant. Measurements obtained under reversed-phase conditions indicate that the local capacity factor changes considerably with local pressure under typical operating conditions. These results are somewhat surprising since the mobile-phase solvents used for liquid chromatography are generally considered to be incompressible.
Date: January 1, 1991
Creator: McGuffin, V.L. & Evans, C.E.
Partner: UNT Libraries Government Documents Department

Effect of particle size and stabilizing additives on the combustion properties of magnesium slurry

Description: Report presenting an experimental investigation using a 1 7/8-inch diameter burner to determine the effects of particle size and stabilizing additives on the combustion performance of magnesium-hydrocarbon slurry fuels. Results regarding an evaluation of the sampling method, blow-out velocity, and combustion efficiency are provided.
Date: January 14, 1953
Creator: Lord, Albert M. & Evans, Vernida E.
Partner: UNT Libraries Government Documents Department

Relationships Between Attitudes Toward Children, Knowledge of Child Development Content, and Designated Variables

Description: The teaching of understandings and techniques concerning the care of children is certainly an important part of the homemaking teacher's job, but research by Bettelheim has pointed out that the underlying attitudes of parents often influence how well they put their knowledge into practice.
Date: August 1961
Creator: Pritchett, Karen Rohne
Partner: UNT Libraries

MODELING OF COUPLED EDGE STOCHASTIC AND CORE RESONANT MAGNETIC FIELD EFFECTS IN DIVERTED TOKAMAKS

Description: Attaining the highest performance in poloidally diverted tokamaks requires resonant magnetic perturbation coils to avoid core instabilities (locked, resistive wall and neoclassical tearing modes). These coils also perturb the pedestal and edge region, causing varying degrees of stochasticity with remnant islands. The effects of the DIII-D locked mode control coil on the edge and core of Ohmic plasmas are modeled with the field line integration code TRIP3D and compared with experimental measurements. Without detailed profile analysis and field line integration, it is difficult to establish whether a given response is due to a ''core mode'' or an ''edge stochastic boundary.'' In diverted Ohmic plasmas, the boundary stochastic layer displays many characteristics associated with such layers in non-diverted tokamaks. Comparison with stochastic boundary results from non-diverted tokamaks indicates that a significant difference in diverted tokamaks is a ''focusing'' of the magnetic field line loss into the vicinity of the divertor.
Date: June 1, 2002
Creator: EVANS, T.E. & MOYER, R.A.
Partner: UNT Libraries Government Documents Department

Little Boy neutron spectrum below 3 MeV

Description: The leakage neutron spectrum from the Little Boy replica has been measured from 12 keV to 3 MeV using a high-resolution /sup 3/He ionization chamber, and from 1 keV to 3 MeV using proton-recoil proportional counters. The /sup 3/He-spectrometer measurements were made at distances of 0.75 and 2.0 m from the active center and at angles of 0/sup 0/, 45/sup 0/, and 90/sup 0/ with respect to the axis of the assembly. Proton-recoil measurments were made at 90/sup 0/ to the assembly axis at distances of 0.75 and 2.0 m, with a shielded measurement made at 2.0 m to estimate background due to scattering. The /sup 3/He spectrometer was calibrated at Los Alamos using monoenergetic /sup 7/Li(p,n)/sup 7/Be neutrons to generate a family of response functions. The proton-recoil counters were calibrated at Argonne by studying the capture of thermal neutrons by nitrogen in the counters, by observation of the 24-keV neutron resonance in iron, and by relating to the known hydrogen content of the counters. The neutron spectrum from Little Boy was found to be highly structured, with peaks corresponding to minima in the iron total neutron cross section. In particular, influence of the 24-keV iron window was evident in both sets of spectra. The measurements provide information for dosimetry calculations and also a valuable intercomparison of neutron spectrometry using the two different detector types. Spectra measured with both detectors are in essential agreement. 8 references, 7 figures, 2 tables.
Date: January 1, 1984
Creator: Evans, A.E.; Bennett, E.F. & Yule, T.J.
Partner: UNT Libraries Government Documents Department

Thermal Conductivity of 14 Metals and Alloys Up to 1100 Degrees Fahrenheit

Description: Memorandum presenting a determination of the thermal conductivity of 14 metals and alloys in temperatures ranges with a maximum of 1100 degrees Fahrenheit. Some of the metals included steels, high-temperature alloys, molybdenum disilicide, aluminum alloys, brass, and silver. A comparison method was used to obtain the results in which the thermal conductivity of the test sample was compared with the conductivity of high-purity lead.
Date: March 2, 1951
Creator: Evans, Jerry E., Jr.
Partner: UNT Libraries Government Documents Department

DIII-D Research Operations annual report to the US Department of Energy, October 1, 1990--September 30, 1991. Magnetic Fusion Research Program

Description: This report discusses the following topics on Doublet-3 research operations: DIII-D Program Overview; Boundary Plasma Research Program/Scientific Progress; Radio Frequency Heating and Current Drive; Core Physics; DIII-D Operations; Program Development; Support Services; ITER Contributions; Burning Plasma Experiment Contributions; and Collaborative Efforts.
Date: March 1, 1992
Creator: Simonen, T. C. & Evans, T. E.
Partner: UNT Libraries Government Documents Department

The influence of pressure on solute retention in liquid chromatography

Description: In this investigation, multiple on-column detectors are utilized to measure the retention of model solutes directly on a packed, capillary column. The absolute pressure on the column is controlled using a restrictor at the column exit, while the pressure gradient and volumetric flowrate are maintained constant. Measurements obtained under reversed-phase conditions indicate that the local capacity factor changes considerably with local pressure under typical operating conditions. These results are somewhat surprising since the mobile-phase solvents used for liquid chromatography are generally considered to be incompressible.
Date: December 31, 1991
Creator: McGuffin, V. L. & Evans, C. E.
Partner: UNT Libraries Government Documents Department

Numerical Modelling of the Nonlinear ELM Cycle in Tokamaks

Description: A numerical model of the nonlinear evolution of edge localized modes (ELMs) in tokmaks is presented. In the model discussed here it is assumed that thermoelectric currents flow in short connection length flux tubes, initially established by error fields or other non-axisymmetric magnetic perturbations. Magnetic perturbations resulting from the currents are incorporated into the magnetic topology. The predictions are compared to measurements at the DIII-D tokamak. Excellent agreement between the calculated magnetic structures on the vessel wall and camera observations during an ELM cycle is shown. The ELM collapse process is discussed.
Date: June 2, 2009
Creator: Wingen, A; Evans, T E; Lasnier, C J & Spatschek, K H
Partner: UNT Libraries Government Documents Department

Impurity penetration and transport during VH-mode on DIII-D

Description: A new modeling effort is made in order to understand the observed relatively low levels of impurity contamination during the VH-mode phase on DIII-D, as compared to those observed during the H-mode phase of selected discharges. The key element is the inclusion of the real 2-D flux surface geometry in the prediction of impurity penetration of sputtered atoms through the scrape-off layer into the core plasma. Of the elements which determine the impurity content in the plasma: sputtering yield, penetration, and core transport, the penetration through the scrape-off layer is found to be the most determinative factor. The low impurity content in VH-mode is attributed to the development of a scrape-off layer with higher density and temperature properties than those normally obtained in H-mode.
Date: May 1, 1992
Creator: Lippmann, S.I.; Evans, T.E.; Jackson, G.L. & West, W.P.
Partner: UNT Libraries Government Documents Department

DIII-D Research Operations annual report to the US Department of Energy, October 1, 1990--September 30, 1991

Description: This report discusses the following topics on Doublet-3 research operations: DIII-D Program Overview; Boundary Plasma Research Program/Scientific Progress; Radio Frequency Heating and Current Drive; Core Physics; DIII-D Operations; Program Development; Support Services; ITER Contributions; Burning Plasma Experiment Contributions; and Collaborative Efforts.
Date: March 1, 1992
Creator: Simonen, T.C. & Evans, T.E. (eds.)
Partner: UNT Libraries Government Documents Department