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Positron lifetime and Doppler broadening techniques applied to irradiation-damaged silver (open access)

Positron lifetime and Doppler broadening techniques applied to irradiation-damaged silver

Positron lifetime and Doppler broadening measurements have been used to study defect production resulting from room temperature irradiation of pure silver by D-T fusion neutrons or energetic protons. Use of the positron annihilation analysis has established that the surviving defects from both irradiations have the same dose dependence and that defect concentration can be quantitatively measured and compared to damage models. The relative merit of the lifetime and Doppler broadening measurements in arriving at these conclusions is discussed in this report along with some practical aspects of the measurements. In the proton damaged samples the trapping rate approaches saturation, a circumstance which could be misinterpreted if a less extensive data set containing only Doppler broadening data were available. Some remarks about the analysis of positron data and general conclusions about the defect structure are given. 3 figures.
Date: July 27, 1981
Creator: Howell, R.H.
System: The UNT Digital Library
Molecular potentials and relaxation dynamics (open access)

Molecular potentials and relaxation dynamics

The use of empirical pseudopotentials, in evaluating interatomic potentials, provides an inexpensive and convenient method for obtaining highly accurate potential curves and permits the modeling of core-valence correlation, and the inclusion of relativistic effects when these are significant. As an example, recent calculations of the chi/sup 1/..sigma../sup +/ and a/sup 3/..sigma../sup +/ states of LiH, NaH, KH, RbH, and CsH and the chi/sup 2/..sigma../sup +/ states of their anions are discussed. Pseudopotentials, including core polarization terms, have been used to replace the core electrons, and this has been coupled with the development of compact, highly-optimized basis sets for the corresponding one- and two-electron atoms. Comparisons of the neutral potential curves with experiment and other ab initio calculations show good agreement (within 1000 cm/sup -1/ over most of the potential curves) with the difference curves being considerably more accurate.
Date: March 27, 1981
Creator: Karo, A.M.
System: The UNT Digital Library
Overview of coal conversion (open access)

Overview of coal conversion

The structure of coal and the processes of coal gasification and coal liquefaction are reviewed. While coal conversion technology is not likely to provide a significant amount of synthetic fuel within the next several years, there is a clear interest both in government and private sectors in the development of this technology to hedge against ever-diminishing petroleum supplies, especially from foreign sources. It is evident from this rather cursory survey that there is some old technology that is highly reliable; new technology is being developed but is not ready for commercialization at the present state of development. The area of coal conversion is ripe for exploration both on the applied and basic research levels. A great deal more must be understood about the reactions of coal, the reactions of coal products, and the physics and chemistry involved in the various stages of coal conversion processes in order to make this technology economically viable.
Date: March 27, 1981
Creator: Clark, B. R.
System: The UNT Digital Library
Pressure measurements of nonplanar stress waves (open access)

Pressure measurements of nonplanar stress waves

A useful gage has been developed for measuring pressure of nonplanar or obliquely incident stress waves. The measurements made with these gages are not as precise as direct strain gage measurements, but are very good considering the conditions under which these gages are used. We feel a need to further develop our ability to measure nonplanar stress waves in the 0 to 10 kbar range. Carbon or ytterbium will probably be chosen for the sensing element.
Date: February 27, 1981
Creator: Carlson, G.H. & Charest, J.A.
System: The UNT Digital Library
Effects of Pressure and Temperature on the Thermal Properties of a Salt and a Quartz Monzonite (open access)

Effects of Pressure and Temperature on the Thermal Properties of a Salt and a Quartz Monzonite

Measurements have been made of thermal conductivity, diffusivity, and linear expansion as a function of temperature (to 573 K) and hydrostatic pressure (to 50 MPa) on two rocks, Avery Island domal salt and Climax Stock quartz monzonite. For Avery Island salt the thermal properties do not show any pressure dependence and are approximately the same values as for single crystal halite at 0.1 MPa. The lack of pressure dependence is attributed to the high symmetry of halite (cubic) and to its low strength, both of which inhibit brittle fracturing. For Climax Stock quartz monzonite no pressure dependence of thermal diffusivity has been resolved, but conductivity does show a drop of approximately 10% with decreasing pressure from 50 to 3 MPa. The pressure dependence is not measurably altered by heating the rock to as high as 473 K under 50 MPa. Our measurements so far on the thermal conductivity of quartz monzonite vs temperature and pressure are in agreement with predictions of the Walsh and Decker (1966) model of thermal conductivity vs crack porosity based on independent measurements of crack porosity vs temperature and pressure for the same quartz monzonite. Heating to temperatures greater than 473 K at 50 MPa, or …
Date: March 27, 1981
Creator: Durham, W. B. & Abey, A. E.
System: The UNT Digital Library
Category I structures program. [PWR; BWR] (open access)

Category I structures program. [PWR; BWR]

The objective of the Category I Structure Program is to supply experimental and analytical information needed to assess the structural capacity of Category I structures (excluding the reactor cntainment building). Because the shear wall is a principal element of a Category I structure, and because relatively little experimental information is available on the shear walls, it was selected as the test element for the experimental program. The large load capacities of shear walls in Category I structures dictates that the experimental tests be conducted on small size shear wall structures that incorporates the general construction details and characteristics of as-built shear walls.
Date: October 27, 1981
Creator: Endebrock, E.G. & Dove, R.C.
System: The UNT Digital Library