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Energy Dependence of Complete and Incomplete Fusion in the /sup 28/Si + /sup 12/C Reaction
To study possible entrance channel effects in certain heavy-ion reactions and to investigate the dependence of such processes on heavier projectiles, measurements involving a pulsed /sup 28/Si beam and /sup 12/C target were performed using the ANL ATLAS facility. TOF measurements at /sup 28/Si bombarding energies of 11.0, 14.3, and 16.1 MeVu were carried out to establish the total evaporation residue cross section behavior for complete and incomplete fusion. 4 figs., 1 tab.
Date:
January 1, 1988
Creator:
Mateja, J. F.; Vineyard, M. F.; Kovar, D. G.; Beck, C.; Henderson, D. J.; Janssens, R. V. F. et al.
Object Type:
Article
System:
The UNT Digital Library
Overview of the SDI (Strategic Defense Initiative) Program in short wavelength chemical lasers
Advanced chemical lasers promise to be effective space-based weapons against responsive threats. In this program, we are developing both CW and pulsed concepts for achieving this goal. Certain approaches may also be appropriate as ground-based weapons and fusion drivers. 12 refs., 1 fig., 5 tabs.
Date:
January 1, 1988
Creator:
Jones, C.R.
Object Type:
Article
System:
The UNT Digital Library
High-resolution neutron transmission measurements on /sup 235/U, /sup 239/Pu, and /sup 238/U
High-resolution transmission measurements have been made on three sample thicknesses of both /sup 235/U and /sup 239/Pu at liquid nitrogen temperature and also on three of /sup 238/U at room temperature using neutrons from the water-moderated ORELA target. The data on /sup 235/U and /sup 239/Pu from 1 to 10,000 eV were obtained using /sup 6/Li glass scintillation detectors at 17.909-and 80.394-m flight paths. The /sup 238/U data from 1 to 100 keV were obtained using a new NE 110 proton-recoil scintillation detector at a 210.558-m flight path.
Date:
January 1, 1988
Creator:
Harvey, J.A.; Hill, N.W.; Perey, F.G.; Tweed, G.L. & Leal, L.
Object Type:
Article
System:
The UNT Digital Library
Pulsed CO sub 2 laser processing of thin ion-implanted silicon layers
We show that extremely shallow ({approx lt} 800 {Angstrom}) melt depths can be easily obtained by irradiating a thin heavily doped silicon layer with a CO{sub 2} laser pulse. Since the absorption of the CO{sub 2} laser pulse is dominated by free-carrier transitions, the beam heating occurs primarily in the thin degenerately doped film. For CO{sub 2} pulse-energy densities exceeding a threshold value, surface melting occurs and the reflectivity of the incident laser pulse increases abruptly to about 90%. This large increase in the reflectivity acts like a switch to reflect almost all of the energy in the remainder of the pulse, thereby greatly reducing the amount of energy available to drive the melt front to deeper depths in the material. Transmission electron microscopy shows no extended defects in the near-surface region after laser irradiation, and van der Pauw electrical measurements verify that 100% of the implanted arsenic dopant is electrically active. 8 refs., 3 figs., 1 tab.
Date:
January 1, 1988
Creator:
James, R.B. (Sandia National Labs., Livermore, CA (United States)) & Christie, W.H. (Oak Ridge National Lab., TN (United States))
Object Type:
Article
System:
The UNT Digital Library
Experimental and analytical studies of passive shutdown heat removal from advanced LMRs (liquid metal reactors)
A facility designed and constructed to demonstrate the viability of natural convection passive heat removal systems as a key feature of innovative LMR Shutdown Heat Removal (SHR) systems is in operation at Argonne National Laboratory (ANL). This Natural Convection Shutdown Heat Removal Test Facility (NSTF) has investigated the heat transfer performance of the GE/PRISM passive design. This initial series of experiments simulates the air-side geometry of the PRISM Radiant Reactor Vessel Auxiliary Cooling System (RVACS). The NSTF operates in either a uniform heat flux mode and a uniform temperature mode at the air/guard vessel interface. Analysis of the RVACS performance data indicates excellent agreement with pretest analytical predictions. Correlation analysis presents the heat transfer data in a form suitable for use in LMR design and verification of analytical studies.
Date:
January 1, 1988
Creator:
Pedersen, D.; Heineman, J.; Stewart, R.; Anderson, T.; Lottes, P. & Tessier, J.
Object Type:
Article
System:
The UNT Digital Library
Performance of the Los Alamos expanding telescope
An expanding telescope can produce a very low divergence particle beam, provided that the beam optics have sufficient quality in order not to introduce large aberrations. Even as late as two years ago there were no theoretical beamline codes, and little experimental work that could describe the third-order aberrations introduced by an expanding telescope. A project was undertaken at Los Alamos National Laboratory to perform these calculations, and to build a telescope to confirm the predictions. It was installed at Argonne National Laboratory during the summer of 1987 and tested in a 50 MeV H/sup /-// beam. The telescope consisted of a singlet eyepiece and triplet objective lens with a twenty times magnification. It performed to the design specifications of twenty-five micro-radians beam divergence with a parallel beam focus. The measured geometric aberrations were found to be in agreement with the computer calculations.
Date:
January 1, 1988
Creator:
Dombeck, T.W.
Object Type:
Article
System:
The UNT Digital Library
ACE: AMY CDC (Central Drift Chamber) Fast Track Finder
The central drift chamber (CDC) of the AMY detector at the TRISTAN e/sup /+//e/sup /-// collider features its fine granularity and multi-band structure. The tracking software named ACE which makes the most of these features shows an excellent performance for reconstruction of high multiplicity events with highly collimated jets. The obtained reconstruction efficiency is 97% for the particles coming from within 5 cm of the primary vertex with p/sub t/ /approx gt/ 500 MeVc in the simulated hadronic events. The processing time is on average less than 300 ms per hadronic event (simulated or real) on a FACOM M-382 computer. 3 refs., 5 figs.
Date:
January 1, 1988
Creator:
Mori, T.
Object Type:
Article
System:
The UNT Digital Library
Application of artificial intelligence to melter control: Realtime process advisor for the scale melter facility
The Defense Waste Processing Facility (DWPF) at the Savannah River Plant (SRP) is currently under construction and when completed will process high-level radioactive waste into a borosilicate glass wasteform. This facility will consist of numerous batch chemical processing steps as well as the continuous operation of a joule-heated melter and its off-gas treatment system. A realtime process advisor system based on Artificial Intelligence (AI) techniques has been developed and is currently in use at the semiworks facility, which is operating a 2/3 scale of the DWPF joule-heated melter. The melter advisor system interfaces to the existing data collection and control system and monitors current operations of this facility. The advisor then provides advice to operators and engineers when it identifies process problems. The current system is capable of identifying process problems such as feed system pluggages and thermocouple failures and providing recommended actions. The system also provides facilities normally with distributed control systems. These include the ability to display process flowsheets, monitor alarm conditions, and check the status of process interlocks. 7 figs.
Date:
January 1, 1988
Creator:
Edwards, Jr, R E
Object Type:
Article
System:
The UNT Digital Library
Covariance analysis of n + 7Li data for ENDF/B-VI
A new covariance analysis of n/plus//sup 7/Li experimental data has been completed for Version VI of ENDFB. The analysis basically updates our 1981 work for ENDFB-V.2 to include new data that has become available since that time and to incorporate cross correlations between different experiments. The bulk of the new measured data consists of some 10 new (or newly revised) tritium-production measurements involving about 70 new data points. The new analysis results in only small changes in the previous evaluation of the tritium-production cross section but significantly reduces the magnitudes of uncertainties due to the more extensive and accurate data base that was used.
Date:
January 1, 1988
Creator:
Young, P.G.
Object Type:
Article
System:
The UNT Digital Library
A theoretical prediction of critical heat flux in forced convection boiling during power transients
In this paper, a theoretical prediction of critical heat flux (CHF) during power transients in forced convective boiling is presented. The analysis is restricted to the departure from nucleate boiling (DNB) type of CHF at low qualities. The developed theory is compared with the experimental data available in the literature. The agreement is favorable. The results are discussed in terms of the various parameters affecting the transient CHF. This new model also is compared with the semi-empirical transient CHF model in the literature.
Date:
January 1, 1988
Creator:
Pasamehmetoglu, K.O.; Nelson, R.A. & Gunnerson, F.S.
Object Type:
Article
System:
The UNT Digital Library
Nuclear-data evaluation based on direct and indirect measurements with general correlations
Optimum procedures for the statistical improvement, or updating, of an existing nuclear-data evaluation are reviewed and redeveloped from first principles, consistently employing a minimum-variance viewpoint. A set of equations is derived which provides improved values of the data and their covariances, taking into account information from supplementary measurements and allowing for general correlations among all measurements. The minimum-variance solutions thus obtained, which we call the method of ''partitioned least squares,'' are found to be equivalent to a method suggested by Yu. V. Linnik and applied by a number of authors to the analysis of fission-reactor integral experiments; however, up to now, the partitioned-least-squares formulae have not found widespread use in the field of basic data evaluation. This approach is shown to give the same results as the more commonly applied Normal equations, but with reduced matrix inversion requirements. Examples are provided to indicate potential areas of application. 10 refs.
Date:
January 1, 1988
Creator:
Muir, D.W.
Object Type:
Article
System:
The UNT Digital Library
Root cause analysis at the Savannah River Plant
Events (or near misses) provide important information about ways to improve plant performance. Any particular event may have several /open quotes/root causes/close quotes/ that need correcting to prevent recurrence of the event and, thereby, improve the safety of the plant. Also, by reviewing a large number of events, one can identify cause trends or /open quotes/generic concerns./close quotes/ A method has been developed at Savannah River Plant (SRP) to systematically evaluate events, identify their root causes, record the root causes, and analyze the root cause trends. By providing a systematic method to identify correctable root causes, the system helps the event investigator ask the right questions during the investigation. It also provides an independent safety analysis group and management with statistics indicating existing and developing trouble spots. 3 refs., 4 figs.
Date:
January 1, 1988
Creator:
Paradies, M & Busch, D
Object Type:
Article
System:
The UNT Digital Library
A subregion block iteration to 3-D finite element modeling of subsurface flow
A subregion block iteration (SBI) technique has been developed in conjunction with finite element approximations of saturated-unsaturated flow equations. The proposed SBI technique is implemented in a three-dimensional finite element saturated-unsaturated flow model. The model is verified with a nonlinear diffusion equation having an analytical solution. It is then applied to a burial trench problem. It is not possible to solve this field problem using the direct elimination finite element method. The SBI technique provides significant improvement over models based on direct band solution methods in both central processing unit (CPU) storage and CPU time. 5 refs., 2 figs.
Date:
January 1, 1988
Creator:
Yeh, G.T.
Object Type:
Article
System:
The UNT Digital Library
Microscopy and Elemental Analysis in Tissue Samples Using Computed Microtomography With Synchrotron X-Rays
The initial development shows that CMT using synchrotron x-rays can be developed to ..mu..m spatial resolution and perhaps even better. This creates a new microscopy technique which is of special interest in morphological studies of tissues, since no chemical preparation or slicing of the sample is necessary. The combination of CMT with spatial resolution in the ..mu..m range and elemental mapping with sensitivity in the ppM range results in a new tool for elemental mapping at the cellular level. 7 refs., 1 fig.
Date:
January 1, 1988
Creator:
Spanne, P. & Rivers, M. L.
Object Type:
Article
System:
The UNT Digital Library
Costs of nuclear waste glassmaking at Savannah River
Recently developed reference schedules for processing high-level nuclear wastes into solid glass froms at Savannah River provide bases for economic evaluations of potential improvements of glass melter design and operation. Greater melter output is achieved through increases in capacity and attainment and possible higher glass waste loadings. The economic evaluation indicates only minor beneficial impacts on total waste disposal costs for melter outputs greater than current reference values. In contrast, cost impacts are detrimentally large for outputs less than reference values, providing important incentives for development to ensure the reference output. The limits on cost benefits for greater-than-reference output are not intrinsic to on melter feed specified to control radiation and heat loads of the product glass waste form. 14 ref., 3 figs., 1 tab.
Date:
January 1, 1988
Creator:
McDonell, W R; Thomas, S D & Goodlett, C B
Object Type:
Article
System:
The UNT Digital Library
Some fundamental aspects of the optical potential for the interaction of fast neutrons with cobalt
Differential elastic- and inelastic-scattering cross sections, measured from approx.1.5 to 10.0 MeV, are interpreted in terms of spherical-optical-statistical (OM) and coupled-channels models. A successful description of the differential elastic scattering below 10 MeV and the total cross section to 20.0 MeV is achieved using the spherical OM with energy-dependent strengths and geometries. These energy dependencies are large below approx.7.0 MeV, but become smaller and similar to those reported for /open quotes/global/close quotes/ potentials at higher energies. This change in the energy dependence of the parameters probably marks the onset of the Fermi surface anomaly approx.19 MeV above the Fermi energy. Inelastic scattering to the levels below 1.8 MeV displays a forward-peaked behavior. This nonstatistical component is interpreted using the weak-coupling model in which the f/sub 7/2 proton hole is coupled to the 2/sup /plus// state in /sup 60/Ni. This model provides an explanation of the unusual energy dependence and relatively small radius found for the imaginary OM potential. The coupling also contributes to the large value of this potential. The real spherical OM potential derived from the neutron-scattering results is extrapolated to bound energies by using the dispersion relationship and the method of moments. The resulting real-potential strength and radius …
Date:
January 1, 1988
Creator:
Smith, A. B. & Lawson, R. D.
Object Type:
Article
System:
The UNT Digital Library
High-fidelity in isotope ratio measurements for resonance ionization mass spectrometry
Calculations are performed to gauge the effect of the convolution of atomic spectral characteristics with laser sources upon isotope ratio measurements by Resonance Ionization Mass Spectrometry (RIMS). Comparison with experimental data is included. 7 refs., 3 figs.
Date:
January 1, 1988
Creator:
Miller, C. M.; Fearey, B. L.; Palmer, B. A. & Nogar, N. S.
Object Type:
Article
System:
The UNT Digital Library
Remote reactor repair: GTA (gas tungsten Arc) weld cracking caused by entrapped helium
A repair patch was welded to the wall of a nuclear reactor tank using remotely controlled thirty-foot long robot arms. Further repair was halted when gas tungsten arc (GTA) welds joining type 304L stainless steel patches to the 304 stainless steel wall developed toe cracks in the heat-affected zone (HAZ). The role of helium in cracking was investigated using material with entrapped helium from tritium decay. As a result of this investigation, and of an extensive array of diagnostic tests performed on reactor tank wall material, helium embrittlement was shown to be the cause of the toe cracks.
Date:
January 1, 1988
Creator:
Kanne, W. R., Jr.
Object Type:
Article
System:
The UNT Digital Library
Static magnetic ordering of CeCu/sub 2. 1/Si/sub 2/ found by muon spin relaxation
Zero- and longitudinal-field muon spin relaxation measurements on a poly-crystal sample of a heavy-fermion superconductor CeCu/sub 2.1/Si/sub 2/ (T/sub c/ = 0.7 K) have revealed an onset of static magnetic ordering below T )approximately) 0.8 K. The line shapes of the observed spectra in zero field indicate a wide distribution of static random local fields at muon sites, suggesting that the ordering is either spin glass or incommensurate spin-density-wave state. The observed width of the random local field at T = 0.05 K corresponds to a small averaged static moment of the order of 0.1 ..mu../sub B/ per formula unit.
Date:
January 1, 1988
Creator:
Uemura, Y. J.; Kossler, W. J.; Yu, X. H.; Schone, H. E.; Kempton, J. R.; Stronach, C. E. et al.
Object Type:
Article
System:
The UNT Digital Library
Prediction of the migration of radionuclides to the boundary of a shallow land burial trench
A general model which predicts the source term, radionuclide release rate, as a function of water flow, container degradation rate, waste form leach rate, and radionuclide migration rate from a low-level waste shallow land burial treach is being developed. This paper discusses modeling radionuclide migration, one component of the source term. Simulations of radionuclide transport from a generic shallow land burial trench have been performed for a range of water flow rates, dispersivity values, and distribution coefficients. For the modeling assumptions used and the range of parameters tested, the water flow rate plays the major role in redistributing radionuclides within the trench, except in the case of extremely high dispersion. Dispersion was always found to play significant role in determining transport. This was particularly apparent upstream from the source. Sorption decreased the magnitude of the radionuclide concentration and had the apparent effect of reducing the velocity with which the radionuclides were transported. Diffusion was found to be unimportant in determining radionuclide transport. 12 refs., 8 figs., 2 tabs.
Date:
January 1, 1988
Creator:
Sullivan, T.M.
Object Type:
Article
System:
The UNT Digital Library
Freely expanding detonation products: Scaling of rate processes
Using the Los Alamos reactive hydrodynamics code KIVA, calculations have been made to simulate the free expansion of cylinders of detonation products into a high vacuum. The emphasis of this paper is on the scaling of rate processes with cylinder size and initial conditions as a function of position in the expanding mass. The processes considered include diffusion, unimolecular decomposition, biomolecular radical reactions, and vibrational relaxation. The calculations also give time-dependent velocity fields; schlieren images; and profiles of density, pressure, and temperature. Many features of the calculations can be compared with experimental observations, including time-delayed schlieren and shadowgraph snapshots, time-dependent absorption spectra, and time-of-arrival profiles of molecular species. Some unexpected insights, such as the effect of the equation of state on the shape of the expanding plume and the effect of position on the rate of quenching, are discussed. These calculations are being used to interpret the available experimental data and to design future experiments. 6 refs., 13 figs.
Date:
January 1, 1988
Creator:
Greiner, N. R.
Object Type:
Article
System:
The UNT Digital Library
Explosions and other uncontrolled chemical reactions at non-reactor nuclear facilities of the Savannah River Plant
This paper describes five energetic reactions (explosions) that have occurred at the Savannah River Plant non-reactor nuclear facilities. 1 fig.
Date:
January 1, 1988
Creator:
Durant, W. S.; Gray, L. W.; Wallace, R. M. & Yau, W. W. F.
Object Type:
Article
System:
The UNT Digital Library
Status of fission yield data
In this paper we summarize the current status of the recent US evaluation for 34 fissioning nuclides at one or more neutron incident energies and for spontaneous fission. Currently there are 50 yields sets, and for each we have independent and cumulative yields and uncertainties for approximately 1100 fission products. When finalized the recommended data will become part of Version VI of the US ENDF/B. Other major evaluations in progress that are included in a recently formed IAEA Coordinated Research Program are also summarized. In a second part we review two empirical models in use to estimate independent yields. Comparison of model estimates with measured data is presented, including a comparison with some recent data obtained from Lohengrin (Cf-249 T). 18 refs., 13 figs., 3 tabs.
Date:
January 1, 1988
Creator:
England, T. R. & Blachot, J.
Object Type:
Article
System:
The UNT Digital Library
A program to obtain reliable photoabsorption cross sections
A program to obtain reliable photoabsorption cross sections for a broad range of elements has been initiated at Lawrence Livermore National Laboratory. Using well-characterized samples, absolute measurements have been made with overall uncertainties of /+-/10% or less over energy ranges from about 50 eV to several keV, at several synchrotron radiation facilities. More than a dozen elements have been investigated and other measurements are being planned for elements beryllium (Z-4) through uranium (Z-92). Among the interesting phenomena observed are the resonances/enhancements which seem to accompany virtually every inner shell threshold. Specific examples discussed in this paper include carbon, nickel and uranium. Comparison with theory and existing data compilations/data bases indicate the need for substantial theoretical and compilation improvements. 24 refs., 6 figs.
Date:
January 1, 1988
Creator:
Del Grande, N.K. & Tirsell, K.G.
Object Type:
Article
System:
The UNT Digital Library