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4,161 Matching Results
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Excitation of giant resonances in pion charge-exchange reactions
The theory for excitation of electric giant isovector resonances in pion charge-exchange reactions is discussed. A comparison between the theoretical and the recent experimental results is made. 18 references.
Date:
January 1, 1983
Creator:
Auerbach, N.
Object Type:
Article
System:
The UNT Digital Library
Role of environment
Radiological assessments rely heavily on the use of mathematical models to predict the dose to man resulting from the environmental transport and subsequent human uptake of radionuclides released from nuclear activities. The paper discusses some problems in the use of these models based on the requirement that uptake and transfer coefficients for specific radionuclides and organisms be systematically determined in situ. Due to the lack of availability of these coefficients, reliance on generic default values causes uncertainties related to the variability of the environmental and experimental methodologies. (ACR)
Date:
January 1, 1983
Creator:
Auerbach, S.I.
Object Type:
Article
System:
The UNT Digital Library
Measurements of uranium holdup in an operating gaseous diffusion enrichment plant
Holdup of nuclear material in process equipment is one of the major sources of uncertainty in materials balances, particularly for high-throughput facilities with large equipment and extensive piping, such as gaseous diffusion uranium-enrichment plants. Locating and measuring the holdup while the plant is operating is a challenging problem because of background from the process material and the neighboring equipment. This paper reports NDA measurements performed at the Goodyear Atomic Gaseous Diffusion Plant, Portsmouth, Ohio, on enrichment equipment at the higher enrichment and (>10% /sup 235/U isotopic abundance) of the cascade. Both neutron and gamma-ray measurements were made to locate anomalously large deposits in converters and compressors and, within the limitations of the techniques, to quantify the amount of the deposit.
Date:
January 1, 1983
Creator:
Augustson, R.H.; Walton, R.B.; Harris, R.; Harbarger, W.; Hicks, J.; Timmons, G. et al.
Object Type:
Article
System:
The UNT Digital Library
Dependence of ion beam mixing on projectile mass
Ion beam mixing in Pt-Si bilayered samples was measured during irradiation with projectiles ranging in mass from 4 amu (He) to 131 amu (Xe) at 10/sup 0/K, 300/sup 0/K and 373/sup 0/K. Using deposited damage energy as a basis for comparing the different irradiations, it was found that the heavier ions were more efficient than the lighter ones for inducing mixing. Moreover, it was observed that the mixing was essentially independent of temperature below 373/sup 0/K. These results are interpreted on the basis that the mixing is caused by the stimulated motion of defects during the cooling phase of energetic cascades.
Date:
November 1, 1983
Creator:
Averback, R. S.; Thompson, L. J. & Rehn, L. E.
Object Type:
Article
System:
The UNT Digital Library
Performance of the new cryogenic vacuum system at the Bevatron
A cryogenically cooled liner has been installed within the Bevatron to achieve 10/sup -10/ torr vacuum. Features and performance of this liner are described including achieved pressures, residual gas composition, cryo heat loads, leak rates through moving and static seals, and cool-down and warm-up times.
Date:
March 1, 1983
Creator:
Avery, R. T.; Henderson, T. F.; Kennedy, K. D.; Meneghetti, J. R. & Alonso, J. R.
Object Type:
Article
System:
The UNT Digital Library
Thermal problems on high flux beam lines
Wiggler and undulator magnets can provide very intense photon flux densities to beam line components. This paper addresses some thermal/materials consequences due to such impingement. The LBL/Exxon/SSRL hybrid-wiggler Beam Line VI now nearing operation will be able to provide up to approx. 7 kW of total photon power at planned SPEAR operating conditions. The first masks are located at 6.5 meters from the source and may receive a peak power density (transverse to the beam) exceeding 20 kW/cm/sup 2/. Significantly, this heat transfer rate exceeds that radiated from the sun's surface (7 kW/cm/sup 2/) and is comparable to that of welding torches. Clearing, cooling and configuration are of critical importance. Configurations for the first fixed mask, the movable mask, and the pivot mask on this beam line are presented together with considerations of thermal stress fatigue and of heat transfer by conduction to water-cooling circuits. Some preliminary information on heating of crystals and mirrors is also presented.
Date:
September 1, 1983
Creator:
Avery, R.T.
Object Type:
Article
System:
The UNT Digital Library
Reactions between /sup 58/Ni nuclei at 15. 1 MeV/u
This study was motivated by reports of the observation of ternary events in Kr- and Xe-induced reactions corresponding to the fast fission, or splitting, of projectile like products. The first of these reports, by Olmi et al., emphasized indirect evidence obtained from inclusive data from the reaction /sup 86/Kr + /sup 166/Er at 12.1 MeV/u. It was argued that the observed drift to low-Z products as a function of increasing energy loss could not be accounted for by charged-particle evaporation since the observed yield of charged particles was too low. It was concluded that the distribution of projectile fragments reflected an admixture of ternary events. More direct evidence for this hypothesis was presented by measurements of both projectile fragments, which indicated that relatively little energy loss is involved in the first step of the reaction and little charge transfer takes place prior to fission. The present study was intended to determine if such three-body events also occur in reactions with lighter projectiles to establish the extent of charge transfer and energy loss in the first step of the reaction. Results and preliminary conclusions are presented for reactions between /sup 58/Ni nuclei at 15.1 MeV/u and /sup 58/Ni reactions with mylar. …
Date:
January 1, 1983
Creator:
Awes, T. C.; Ferguson, R. L.; Novotny, R.; Obenshain, F. E.; Plasil, F.; Rauch, V. et al.
Object Type:
Article
System:
The UNT Digital Library
Applications of Bonner sphere detectors in neutron field dosimetry
The theory of neutron moderation and spectroscopy are briefly reviewed, and moderators that are useful for Bonner sphere spectrometers are discussed. The choice of the neutron detector for a Bonner sphere spectrometer is examined. Spectral deconvolution methods are briefly reviewed, including derivative, parametric, quadrature, and Monte Carlo methods. Calibration is then discussed. (LEW)
Date:
September 1, 1983
Creator:
Awschalom, M. & Sanna, R.S.
Object Type:
Report
System:
The UNT Digital Library
New look at displacement factor and point of measurement corrections in ionization chamber dosimetry
A new technique is presented for determination of the effective point of measurement when cavity ionization chambers are used to measure the absorbed dose due to ionizing radiation in a dense medium. An algorithm is derived relating the effective point of measurement to the displacement correction factor. This algorithm relates variations of the displacement factor to the radiation field gradient. The technique is applied to derive the magnitudes of the corrections for several chambers in a p(66)Be(49) neutron therapy beam. 30 references, 4 figures, 1 table.
Date:
January 1, 1983
Creator:
Awschalom, M.; Rosenberg, I. & Ten Haken, R.K.
Object Type:
Report
System:
The UNT Digital Library
Dynamical limitations to heavy-ion fusion
In spite of the many attempts to synthesize superheavy elements in recent years, these efforts have not yet been successful. Recent improved theoretical models of heavy-ion fusion reactions suggest that the formation of super-heavy elements is hindered by the dynamics of the process. Several recent experiments lend support to these theories. The necessity of an excess radial velocity (extra push) over the Coulomb barrier in order to induce fusion is observed experimentally as predicted by the theory. So is a new reaction mechanism, called quasi-fission which tend to exhaust the part of the reaction cross section, which would otherwise lead to fusion. The present study shows that the angular distribution of fragments from quasi-fission processes are very sensitive to the occurrence of this reaction mechanism. A slight modification of one parameter in the theory demanded by the observation of quasi-fission for lighter projectiles via the angular distributions, has the consequence of posing even more-stringent limitations on heavy-ion-fusion reactions. This reduces even further the possibility for synthesizing and identifying superheavy elements in heavy-ion-fusion reactions.
Date:
January 1, 1983
Creator:
Back, B.B.
Object Type:
Article
System:
The UNT Digital Library
Quasi-fission
Recent experimental and theoretical investigations have led to the characterization of a new reaction mechanism called quasi-fission. This process is characterized by the emergence of fission-like fragments, which do not originate from the fission decay of a compound nucleus formed by heavy-ion fusion, but rather from the break up of a short-lived intermediate complex. The occurrence of quasi-fission processes appear to be limited to heavy reaction systems and/or large angular momenta, although the present work demonstrates that such reactions occur for somewhat lighter projectiles than previously believed. It is thus shown that measurements of fragment angular distributions provide a signature for quasifission by being sensitive to whether or not a compound nucleus was formed during the reaction. From an analysis of such data it is concluded that the possibilities for synthesizing super-heavy elements in the range Z=112-116 are reduced considerably over previous estimates.
Date:
January 1, 1983
Creator:
Back, B.B.
Object Type:
Article
System:
The UNT Digital Library
CRRIS: a methodology for assessing the impact of airborne radionuclide releases
The Computerized Radiological Risk Investigation System (CRRIS) consists of six fully integrated computer codes which calculate environmental transport and resulting doses and risks to individuals or populations exposed to atmospheric radionuclide releases. The individual codes may be used alone for various assessment applications or may be run as a system. This presentation provides an overview and introduction to this system of computer codes and their use in conducting nuclear assessments. Radionuclides are handled by CRRIS either in terms of the released radionuclides or in terms of exposure radionuclides which consist of both the released nuclides and all (or a subset of) the decay daughters that grow in during environmental transport. The capability of CRRIS to handle radionuclide chains is accomplished through PRIMUS which serves as a preprocessor by accessing a library of radionuclide decay data and sets up matricies of decay constants which are used by the other CRRIS codes in all calculations involving transport and decay. PRIMUS may also be run independently by the user to define the decay chains, radionuclide decay constants, and branching ratios.
Date:
January 1, 1983
Creator:
Baes, C. F., III & Miller, C. W.
Object Type:
Article
System:
The UNT Digital Library
Effect of water in salt repositories. Final report
Additional results confirm that during most of the consolidation of polycrystalline salt in brine, the previously proposed rate expression applies. The final consolidation, however, proceeds at a lower rate than predicted. The presence of clay hastens the consolidation process but does not greatly affect the previously observed relationship between permeability and void fraction. Studies of the migration of brine within polycrystalline salt specimens under stress indicate that the principal effect is the exclusion of brine as a result of consolidation, a process that evidently can proceed to completion. No clear effect of a temperature gradient could be identified. A previously reported linear increase with time of the reciprocal permeability of salt-crystal interfaces to brine was confirmed, though the rate of increase appears more nearly proportional to the product of sigma ..delta..P rather than sigma ..delta..P/sup 2/ (sigma is the uniaxial stress normal to the interface and ..delta..P is the hydraulic pressure drop). The new results suggest that a limiting permeability may be reached. A model for the permeability of salt-crystal interfaces to brine is developed that is reasonably consistent with the present results and may be used to predict the permeability of bedded salt. More measurements are needed, however, to …
Date:
September 1, 1983
Creator:
Baes, C. F., Jr.; Gilpatrick, L. O.; Kitts, F. G.; Bronstein, H. R. & Shor, A. J.
Object Type:
Report
System:
The UNT Digital Library
Detectors for CBA
We discuss some current approaches to a large solid angle detector. An alternative approach for utilizing the high rate of events at CBA is to design special purpose detectors for specific physics goals which can be pursued within a limited solid angle. In many cases this will be the only way to proceed, and then high luminosity has a different significance. The total rate in the restricted acceptance is less likely to be a problem, while the need for high luminosity to obtain sufficient data is obvious. Eight such experiments from studies carried out in the community are surveyed. Such experiments could be run on their own or in combination with others at the same intersection, or even with a large solid angle detector, if a window can be provided in the larger facility. The small solid angle detector would provide the trigger and special information, while the facility would provide back-up information on the rest of the event. We consider some possibilities of refurbishing existing detectors for use at CBA. This discussion is motivated by the fact that there is a growing number of powerful detectors at colliding beam machines around the world. Their builders have invested considerable amounts …
Date:
May 1, 1983
Creator:
Baggett, N.; Gordon, H. A.; Palmer, R. B. & Tannenbaum, M. J. (eds.)
Object Type:
Report
System:
The UNT Digital Library
CBA main magnet power supply ripple reduction
The preliminary results of a development program to minimize beam perturbation resulting from ripple current generated by the CBA Main Magnet Power Supply are presented. The assessment of the magnitude and causes of the ripple generated led to a modification of the SCR Gate Driver and the addition of a bandpass amplifier correction loop which gave significant improvement. A description of the changes made and the results obtained are included. A second design approach was developed in which the timing of the SCR gate pulses is directly determined by a VCO. The results reported with this VCO Loop indicate superior performance particularly at frequencies below 60 Hz. A shunt transistor regulator design is proposed to minimize higher SCR switching frequency harmonics.
Date:
January 1, 1983
Creator:
Bagley, G. & Edwards, R.J.
Object Type:
Article
System:
The UNT Digital Library
SP-100 power system, the present status and assessment of power conditioning and control technologies. Technical information report
The objective of this task was to establish and evaluate what PCC technologies need to be developed and what impact the availability and development of PCC technologies will have on Ground Demonstration Development Decision.
Date:
November 1, 1983
Creator:
Bahrami, K. A.
Object Type:
Report
System:
The UNT Digital Library
Modeling and simulation of energy-removal system for superconducting magnets
The Large Coil Test Facility at the Oak Ridge National Laboratory employs six D shaped superconducting coils. The coil current ranges from 10 to 20 kA. The protection scheme of these coils requires the coil current to be interrupted. This interruption will generate high-voltage transients in the coil. To prevent destruction of the coil isolation, these transients have to be reduced. Two types of suppressor networks, one a varistor and the other an R-C network, were reviewed. Then each suppressor circuit was simulated to determine the effectiveness of each suppressor. The modelling used the Super Sceptre computer program to simulate these transients.
Date:
January 1, 1983
Creator:
Bailey, J. M.; Googe, J. M. & Wood, R. J.
Object Type:
Article
System:
The UNT Digital Library
Wet Storage Integrity Update
This report includes information from various studies performed under the Wet Storage Task of the Spent Fuel Integrity Project of the Commercial Spent Fuel Management (CSFM) Program at Pacific Northwest Laboratory. An overview of recent developments in the technology of wet storage of spent water reactor fuel is presented. Licensee Event Reports pertaining to spent fuel pools and the associated performance of spent fuel and storage components during wet storage are discussed. The current status of fuel that was examined under the CSFM Program is described. Assessments of the effect of boric acid in spent fuel pool water on the corrosion and stress corrosion cracking of stainless steel and the stress corrosion cracking of stainless steel piping containing stagnant water at spent fuel pools are discussed. A list of pertinent publications is included. 84 references, 21 figures, 11 tables.
Date:
September 1, 1983
Creator:
Bailey, W. J. & Johnson, A. B., (Jr.)
Object Type:
Report
System:
The UNT Digital Library
Pacific Northwest Laboratory annual report for 1982 to the DOE Office of the Assistant Secretary for Environmental Protection, Safety and Emergency Preparedness. Part 5. Environmental and occupational protection, assessment, and engineering
Part 5 of the 1982 Annual Report to the Department of Energy's Office of Environmental Protection, Safety and Emergency Preparedness presents Pacific Northwest Laboratory's progress on work performed for the Office of Environmental Programs, Office of Operational Safety, and the Office of Nuclear Safety. The report is in three sections, introduced by blue divider pages, corresponding to the program elements: Technology Impacts, Environmental and Safety Engineering, Operational and Environmental Safety. In each section, articles describe progress made during FY 1982 on individual projects, as identified by the Field Task Proposal/Agreement. Authors of these articles represent a broad spectrum of capabilities derived from various segments of the Laboratory, reflecting the interdisciplinary nature of the work.
Date:
February 1, 1983
Creator:
Bair, W.J.
Object Type:
Report
System:
The UNT Digital Library
Picosecond pulse-conductivity technique applied to study excess-electron reactions in hydrocarbon mixtures
To measure electron reactions on a picosecond timescale the investigators developed a picosecond pulse-conductivity technique, which makes use of the electron fine-structure pulses of our LINAC (pulse width 25 vs FWHM) to produce excess electrons and now detects changes in sample conductance under optimum conditions with an instrumental response of 18 ps. This resolution is in agreement with a theoretical estimate. This technique has been successfully applied to study excess electron reactions in solvents covering a mobility range from 0.24 to 100 cm/sup 2/V/sup -1/s/sup -1/; extension to lower mobility liquids seem possible.
Date:
January 1, 1983
Creator:
Bakale, G. & Beck, G.
Object Type:
Article
System:
The UNT Digital Library
Role of magnetic reconnection phenomena in the reversed-field pinch
The reversed-field pinch (RFP), an axisymmetric toroidal magnetic confinement experiment, has physics rich in the area commonly called field line reconnection or merging. This paper reviews the topics where reconnection plays a vital role: (a) RFP formation and the phenomenon of self-reversal, (b) RFP sustainment in which the RFP configuration has been shown to be capable of maintaining itself for times much longer than earlier predictions from classical resistive MHD theory, (c) steady state current drive in which dynamo action and associated reconnection processes give rise to the possibility of sustaining the configuration indefinitely by means of low frequency ac modulation of the toroidal and poloidal magnetic fields, (d) the effects of reconnection on the formation and evolution of the magnetic surfaces which are intimately related to the plasma containment properties. It appears that all phases of the RFP operation are intimately related to the reconnection and field regeneration processes similar to those encountered in space and astrophysics.
Date:
January 1, 1983
Creator:
Baker, D. A.
Object Type:
Article
System:
The UNT Digital Library
Population dose commitments due to radioactive releases from nuclear power plant sites in 1980
Population radiation dose commitments have been estimated from reported radionuclide releases from commercial power reactors operating during 1980. In addition doses derived from the shutdown reactors at the Three Mile Island site were included. Fifty-year dose commitments from a one-year exposure were calculated from both liquid and atmospheric releases for four population groups (infant, child, teen-ager and adult) residing between 2 and 80 km from each site. This report tabulates the results of these calculations, showing the dose commitments for both liquid and airborne pathways for each age group and organ. Also included for each site is a histogram showing the fraction of the total population within 2 to 80 km around each site receiving various average dose commitments from the airborne pathways. The total dose commitment from both liquid and airborne pathways ranged from a high of 40 person-rem to a low of 0.02 person-rem with an arithmetic mean of 4 person-rem. The total population dose for all sites was estimated at 180 person-rem for the 96 million people considered at risk.
Date:
August 1, 1983
Creator:
Baker, D. A. & Peloquin, R. A.
Object Type:
Report
System:
The UNT Digital Library
Magnetoresistance, electrical conductivity, and Hall effect of glassy carbon
These properties of glassy carbon heat treated for three hours between 1200 and 2700/sup 0/C were measured from 3 to 300/sup 0/K in magnetic fields up to 5 tesla. The magnetoresistance was generally negative and saturated with reciprocal temperature, but still increased as a function of magnetic field. The maximum negative magnetoresistance measured was 2.2% for 2700/sup 0/C material. Several models based on the negative magnetoresistance being proportional to the square of the magnetic moment were attempted; the best fit was obtained for the simplest model combining Curie and Pauli paramagnetism for heat treatments above 1600/sup 0/C. Positive magnetoresistance was found only in less than 1600/sup 0/C treated glassy carbon. The electrical conductivity, of the order of 200 (ohm-cm)/sup -1/ at room temperature, can be empirically written as sigma = A + Bexp(-CT/sup -1/4) - DT/sup -1/2. The Hall coefficient was independent of magnetic field, insensitive to temperature, but was a strong function of heat treatment temperature, crossing over from negative to positive at about 1700/sup 0/C and ranging from -0.048 to 0.126 cm/sup 3//coul. The idea of one-dimensional filaments in glassy carbon suggested by the electrical conductivity is compatible with the present consensus view of the microstructure.
Date:
February 1, 1983
Creator:
Baker, D.F.
Object Type:
Report
System:
The UNT Digital Library
Particle and field signatures of substorms in the near magnetotail
The near-earth magnetotail (10 less than or equal to r less than or equal to 20 R/sub E/) portion of the terrestrial magnetosphere is very likely the region in which magnetospheric substorms are initiated and it is in this location that substorm-related magnetic reconnection appears to occur. An observational advantage compared to other astrophysical regions is that the near magnetotail can be nearly continuously monitored by spacecraft that are relatively fixed in location. Observations of magnetic fields and plasma distribution functions in the neartail reveal a very regular and predictable sequence of variation in association with substorms. These data, considered in a global context, provide very strong evidence for the neutral line substorm model and, thus, for the regular occurrence of magnetic reconnection in the near-earth magnetotail during substorms.
Date:
January 1, 1983
Creator:
Baker, D.N.
Object Type:
Article
System:
The UNT Digital Library