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Active neutron technique for detecting attempted special nuclear material diversion

Description: The identification of special nuclear material (SNM) diversion is necessary if SNM inventory control is to be maintained at nuclear facilities. (Special nuclear materials are defined for this purpose as either /sup 235/U of /sup 239/Pu.) Direct SNM identification by the detection of natural decay or fission radiation is inadequate if the SNM is concealed by appropriate shielding. The active neutron interrogation technique described combines direct SNM identification by delayed fission neutron (DFN) detection with implied SNM detection by the identification of materials capable of shielding SNM from direct detection. This technique is being developed for application in an unattended material/equipment portal through which items such as electronic instruments, packages, tool boxes, etc., will pass. The volume of this portal will be 41-cm wide, 53-cm high and 76-cm deep. The objective of this technique is to identify an attempted diversion of at least 20 grams of SNM with a measurement time of 30 seconds.
Date: January 1, 1979
Creator: Smith, G.W. & Rice, L.G. III
Partner: UNT Libraries Government Documents Department

Advanced uranium enrichment technologies

Description: The Advanced Gas Centrifuge and Atomic Vapor Laser Isotope Separation methods are described. The status and potential of the technologies are summarized, the programs outlined, and the economic incentives are noted. How the advanced technologies, once demonstrated, might be deployed so that SWV costs in the 1990s can be significantly reduced is described.
Date: March 10, 1983
Creator: Merriman, R.
Partner: UNT Libraries Government Documents Department

Cascade design considerations for cascades composed of stages with large separation factors

Description: The unit cost of product from ideal and nonideal cascades are calculated and compared for a given separation task, that of producing reactor grade uranium containing 3.2% U-235 from normal feed containing 0.72% U-235, under the assumption that the total cascade costs are directly proportional to the total inter-stage flow of the cascade. For the examples chosen, in which the stage separation factors are in the range 2 < ..cap alpha.. < 5 and the resulting cascades contain from four to six stages, the desired product can be obtained at a lower unit cost from a nonideal cascade. However, the unit cost of product from the optimum nonideal cascade is only about one percent less than the unit cost of product from an ideal cascade. In general, this difference in the unit cost of product from nonideal and ideal cascades will be larger for larger values of the stage separation factors and fewer stages in the cascades than considered here; on the other hand, the difference will be smaller for smaller values of the stage separation factors and larger numbers of stages in the cascades, becoming negligible in the case of a close separation.
Date: February 1, 1978
Creator: Von Halle, E.
Partner: UNT Libraries Government Documents Department

Supralinearity of peak 5 and peak 6 in TLD-700

Description: Track Theory has been applied to an earlier suggestion, that the supralinearity of TLD&#x27;s at high gamma-ray doses is due to pre-existing 1-hit and 2-hit trap structures, to calculate high-LET response. Measured /sup 60/Co responses for peaks 5 and 6 in LiF(TLD-700) were decomposed to yield parameters characterizing each peak as a 2-component c-hit mixture. One value of trap radius was assigned to each 2-component representation, different for peak 5 and for peak 6, to calculate their responses for H, He, C, O, and Ne bombardments. Calculations reproduce experimental features of the heavy-ion response of TLD-700, and provide means of connecting the gamma and high-LET responses in thermoluminescent dosimeters.
Date: January 1, 1980
Creator: Waligorski, M P.R. & Katz, R
Partner: UNT Libraries Government Documents Department

Analysis of homogeneous U233 and U235 critical assemblies with ENDF/B-IV data (AWBA development program)

Description: Thirty-two U233 and U235 homogeneous aqueous critical experiments were analyzed with ENDF/B-IV data. Calculated eigenvalues for both fuel types increased by nearly 2 percent over the range of hydrogen/uranium atomic ratio covered (from 2106 to 27.1). This is attributed mostly to an underprediction of fast leakage, with some contribution from the fission and capture resonance integrals of ENDF/B-IV U235. Eigenvalue sensitivities to several nuclear data changes were examined. Values of the thermal criticality parameter constraint K2 for U233 and U235 were derived from the Gwin-Magnuson critical experiments at the zero leakage limit.
Date: October 1, 1977
Creator: Ullo, J.J. & Hardy, J. Jr.
Partner: UNT Libraries Government Documents Department

Validation of the atmospheric transport model: comparison of observed krypton-85 concentrations with those computed using a Gaussian plume model

Description: Thirty monthly average /sup 85/Kr concentrations measured at 13 sampling locations between 25 and 150 km from a quasi-continuous point source were used in a validation study of the Atmospheric Transport Model for Toxic Substances (ATM-TOX). Although the computed values tended to overestimate, more than 60% of them fell within a factor of 2 of the observed concentrations.
Date: January 1, 1982
Creator: Raridon, R.J. & Murphy, B.D.
Partner: UNT Libraries Government Documents Department

Atomic vapor laser isotope separation using resonance ionization

Description: Atomic vapor laser isotope separation (AVLIS) is a general and powerful technique. A major present application to the enrichment of uranium for light-water power-reactor fuel has been under development for over 10 years. In June 1985, the Department of Energy announced the selection of AVLIS as the technology to meet the nation's future need for enriched uranium. Resonance photoionization is the heart of the AVLIS process. We discuss those fundamental atomic parameters that are necessary for describing isotope-selective resonant multistep photoionization along with the measurement techniques that we use. We illustrate the methodology adopted with examples of other elements that are under study in our program.
Date: September 1, 1986
Creator: Comaskey, B.; Crane, J.; Erbert, G.; Haynam, C.; Johnson, M.; Morris, J. et al.
Partner: UNT Libraries Government Documents Department

Very elongated nuclei near A = 194

Description: A {gamma}-ray cascade in {sup 191}Hg of 12 members with average energy spacing 37 keV and Q{sub t} {equals} 18(3)eb was reported by Moore, and coworkers in 1989. This was the first report of very elongated nuclei (superdeformation) in this mass region. Since then, some 25 {gamma}-ray cascades have been observed in 11 (slightly neutron deficient) Hg, Pb and Tl nuclei. The bands have similar dynamic moments-of-inertia. Some nuclei exhibit multiple bands, and the backbending phenomena has been observed. Level spins can be obtained from comparison of transition energies to rotational model formulas. Selected bands (in different nuclei) have equal transition energies (within 0.1%). Alignment in integer multiples of {h bar} has been observed. Properties of these bands will be described. 27 refs., 3 figs.
Date: October 1, 1990
Creator: Becker, J.A.; Henry, E.A.; Yates, S.W.; Wang, T.F.; Kuhnert, A. (Lawrence Livermore National Lab., CA (USA)); Brinkman, M.J. et al.
Partner: UNT Libraries Government Documents Department

(Coordinated research programs in nuclear medicine)

Description: The traveler visited the Clinic for Nuclear Medicine at the University of Bonn, West Germany, to review, organize, and plan collaborative studies. He also met with the editorial board of the journal NucCompact -- European/American Communications in Nuclear Medicine, on which he serves as US editor. He also visited colleagues at the Cyclotron Research Center (CRC) at the University of Liege, Belgium, to coordinate clinical applications of the ultrashort-lived iridium-191m radionuclide obtained from the osmium-190/iridium-191m generator system. The traveler planned and coordinated continuing collaboration with colleagues at the CRC for further applications of this generator system. He also visited the University of Metz, Metz, France, to organize a three-center project for the synthesis and evaluation of various receptor-specific cerebral imaging agents, involving the Oak Ridge National Laboratory (ORNL), CRC, and the University of Metz.
Date: October 3, 1990
Creator: Knapp, F.F. Jr.
Partner: UNT Libraries Government Documents Department

Critical dimensions of systems containing /sup 235/U, /sup 239/Pu, and /sup 233/U: 1986 Revision

Description: This report is primarily a compilation of critical data obtained from experiments performed in a number of laboratories during the period of 1945 through 1985. It supplements the Nuclear Safety Guide (Report TID-7016 (Rev. 2)) in presenting critical data on which recommendations of the Guide are based. It must be emphasized that this report gives critical data without safety factors, so it is no substitute for the Guide or for the related document, The American National Standard for Nuclear Criticality Safety in Operations with Fissionable Materials Outside Reactors. Critical measurements with materials of interest in desired configurations yield information of greatest usefulness and accuracy. Where it is not feasible to obtain the desired critical data, for example, as a result of safety restrictions, subcritical data may be directly applicable, and in some cases may be extrapolated to approximate critical conditions. Critical conditions also may be approximated from the distribution of neutrons introduced into a subcritical assembly. These ''exponential experiments'' may be the only alternative where the quantity of material required is too great for a critical experiment. Calculated extensions of experimental data are included to show the nature of trends, not to substitute for results of experiments. They should be used with caution. A fundamental aim of this document is to illustrate relationships among critical data. The compilation and correlation of data for this purpose, from many measurements in a number of laboratories, require a certain amount of normalization or reduction to common terms. Frequently, for example, the effects of variations in geometry or density must be removed to show trends in data. The manner in which these alterations may be made is discussed in the early section Relations for Conversion to Standard Conditions. 195 refs.
Date: July 1, 1987
Creator: Paxton, H.C. & Pruvost, N.L.
Partner: UNT Libraries Government Documents Department

The file of evaluated decay data in ENDF/B

Description: One important application of nuclear decay data is the Evaluated Nuclear Data File/B, the base of evaluated nuclear data used in reactor research and technology activities within the US. This report discusses the decay data file.
Date: January 1, 1991
Creator: Reich, C.W. (Idaho National Engineering Lab., Idaho Falls, ID (USA)) & England, T.R. (Los Alamos National Lab., NM (USA))
Partner: UNT Libraries Government Documents Department

Development of chemical isolation and concentration techniques for Tc-99 analysis by resin-bead mass spectrometry

Description: A novel, highly sensitive, isotope-dilution analytical technique for the determination of technetium-99 has been developed around single ion-exchange bead mass spectrometry. Mass spectrometry is much more sensitive than direct counting for the low-energy, low-specific activity, Tc-99 isotope. Further, the point source provided by a single ion-exchange bead leads to a greater signal-to-noise ratio in the mass spectrometric measurement than does conventional application of a solution to the source filament. Recent results indicate a sensitivity greater than 0.1 picogram. Isolation of technetium from the samples occurs after addition of Tc-97 as a yield tracer. A combination of ion-exchange chromatography and ion-association solvent extraction provides decontamination from the potential interferences, Mo-97 and Ru-99. Subsequently, the technetium is loaded onto a pair of anion-exchange beads (diameter approx. 0.3 mm). The noncritical isolation and bead-loading scheme typically concentrates the technetium in the sample by a factor of about a million with overall recoveries exceeding 50%. A variety of environmental samples from the Savannah River Plant (SRP) has been analyzed by this method.
Date: January 1, 1979
Creator: Anderson, T.J.
Partner: UNT Libraries Government Documents Department

Comparison of effects of pulsed Ruby laser and pulsed electron beam annealing of /sup 75/AS/sup +/ implanted silicon

Description: Ion-backscattering, ion-channeling, and transmission electron microscopy (TEM) were used to study a series of ion implanted silicon samples that were annealed with either a pulsed laser or a pulsed electron beam. Single crystal ((001) orientation) silicon samples were implanted with either 35 or 100 keV /sup 75/As/sup +/ to a dose of approx. 1 x 10/sup 16/ As/cm/sup 2/ and subsequently annealed with either a Q-switched pulsed Ruby laser or the electron beam generator. A series of energy densities was used in both cases to optimize results. It was determined from backscattering that the as-implanted profiles were redistributed in essentially the same manner for both types of anneals, indicating that melting and rapid recrystallization has occurred. For the 35 keV /sup 75/As/sup +/ implanted samples the two techniques produced equivalent anneals with no remaining damage as indicated by channeling and TEM. However, for the 100 keV implants the anneal was not uniform across the sample in the electron beam case and the channeling minimum yields for the major axes ((110), (111), and (100)) were higher than the laser annealed results. In both cases, the As substitutionality (97 to 99%) and minimum yields are better than results obtained from conventional thermal annealing.
Date: December 1, 1978
Creator: Wilson, S.R.; Appleton, B.R.; White, C.W. & Narayan, J.
Partner: UNT Libraries Government Documents Department

Experimental criticality specifications, update through 1979. Informal report

Description: A table of contents for LA-7170-MS is provided, and publications of criticality specifications that appeared in 1978 and 1979 are listed. The table was omitted from the original document. An abstract of the original report appeared in Energy Research Abstracts, Volume 3: 43410.
Date: February 1, 1980
Creator: Paxton, H.C. (comp.)
Partner: UNT Libraries Government Documents Department

Application of evaluated fission-product delayed-neutron precursor data in reactor kinetics calculations

Description: Evaluated fission-product yield and decay data have been used to describe 105 delayed neutron precursors explicitly in point reactor kinetics calculations. Results calculated for /sup 235/U thermal fission show that rod-drop reactivity values obtained from kinetics calculations with 6-group precursor data are considerably higher than those calculated with explicit delayed-neutron precursor data. The calculated kinetics associated with positive reactivity steps are significantly different.
Date: January 1, 1985
Creator: Perry, R.T.; Wilson, W.B.; England, T.R. & Brady, M.C.
Partner: UNT Libraries Government Documents Department

Nuclear transitions induced by atomic excitations

Description: In the two-step pumping scheme for a gamma-ray laser, an essential step is that of exciting the nucleus from a long-lived storage isomer to a nearby short-lived state that then decays to the upper lasing level. An experiment is in progress to induce this transfer by first exciting the atomic electrons with uv photons. The incident photons couple well to the electrons, which then couple via a virtual photon to the nucleus. As a test case, excitation of the /sup 235/U nucleus is being sought, using a high-brightness uv laser. The excited nuclear state, having a 26-minute half-life, decays by internal converison, resulting in emission of an atomic electron. A pulsed infrared laser produces an atomic beam of /sup 235/U which is then bombarded by the uv laser beam. Ions are collected, and conversion electrons are detected by a channel elctron multiplier. In preliminary experiments, an upper limit of 7 x 10/sup -5/ has been obtained for the probability of exciting a /sup 235/U atom in the uv beam for one picosecond at an intensity of about 10/sup 15/W/cm/sup 2/. Experiments with higher sensitivities and at higher uv beam intensities are underway. 6 refs., 1 fig.
Date: January 1, 1988
Creator: Dyer, P.L.; Bounds, J.A.; Haight, R.C. & Luk, T.S.
Partner: UNT Libraries Government Documents Department

Predicted changes of the internal conversion rates in /sup 119/Sn due to admixtures of lower multipole order

Description: One conceivable basis for interlevel transfer from a long-lived isomer to a graser state might be to alter the multipolarity of the transfer step. As an example, in the case of /sup 119/Sn any mechanism that introduces angular momentum to admix M3 radiation into the normally M4 transition from the 89.6 keV, 11/2/sup -/ level to the 23.9 keV, 3/2/sup +/ state could greatly shorten its normal 293 day half-life. We have calculated the K-shell internal conversion rate for the 89.6 keV level in /sup 119/Sn for small admixtures of M3 radiation using Moszkowski formulas for the radiative transition rates and tabulated values of the internal conversion coefficients. We find that even very small admistures of lower multipole order can produce very large changes in the internal conversion coefficient. This offers the basis for a simple and definitive test of the hypothesized mechanism for creating population inversion by introducing angular momentum. 4 refs., 1 fig.
Date: January 1, 1985
Creator: Wender, S.A.; Baldwin, G.C.; Talbert, W.L. & Reiss, H.R.
Partner: UNT Libraries Government Documents Department

Kinetics of stimulated Moessbauer emission in neutron-pumped krypton-83

Description: Using an idealized kinetic model for a gamma-ray laser system pumped by a spatially uniform delta-function burst of fast neutrons, a computer study has been made of the growth, decay, and attenuation of resonant 9.3-keV recoil-less gamma radiation from /sup 83/Kr, as a function of neutron-burst intensity, gamma-ray linebreadth, temperature, dilution of krypton in a beryllium host, and nonresonant absorption coefficient of the host. The isomer is formed by neutron capture in a 40-eV resonance, and the 144-ns transition lifetime is short in comparison with the time for neutrons to moderate. The kinetic behavior of this system is therefore determined largely by the time dependence of the neutron spectrum and only slightly by the reciprocal linebreadth of the graser transition. Because the lower state is stable, inversion is rapidly lost, so that, for observable gain, an unrealistically high source intensity is needed. Use of a beryllium host, which increases the Debye temperature, is negated by its parasitic absorption. Although this transition is unsuitable for a graser, these findings help to illustrate useful properties of nuclear isomers and solid hosts for which stimulated emission might be observable.
Date: November 1, 1977
Creator: Baldwin, G.C. & McNeil, L.E.
Partner: UNT Libraries Government Documents Department

Nuclear fission and nuclear safeguards: Common technologies and challenges

Description: Nuclear fission and nuclear safeguards have much in common, including the basic physical phenomena and technologies involved as well as the commitments and challenges posed by expanding nuclear programs in many countries around the world. The unique characteristics of the fission process -- such as prompt and delayed neutron and gamma ray emission -- not only provide the means of sustaining and controlling the fission chain reaction, but also provide unique ''signatures'' that are essential to quantitative measurement and effective safeguarding of key nuclear materials (notably /sup 239/Pu and /sup 235/U) against theft, loss, or diversion. In this paper, we trace briefly the historical emergence of safeguards as an essential component of the expansion of the nuclear enterprise worldwide. We then survey the major categories of passive and active nondestructive assay techniques that are currently in use or under development for rapid, accurate measurement and verification of safe-guarded nuclear materials in the many forms in which they occur throughout the nuclear fuel cycle. 23 refs., 14 figs.
Date: January 1, 1989
Creator: Keepin, G.R.
Partner: UNT Libraries Government Documents Department

Nuclear isomer separation

Description: We report experiments on selective photoionization of atoms containing isomeric nuclei of /sup 197/Hg. Other isomer separation techniques and their limitations are discussed.
Date: January 1, 1985
Creator: Dyer, P.
Partner: UNT Libraries Government Documents Department

Validation of aggregate delayed neutron spectra calculated from precursor data

Description: An extensive reference library of delayed neutron data has been compiled which contains fission yields and branchings, delayed neutron emission probabilities, and spectra for 271 precursors. These data have been used to calculate the aggregate behavior of delayed neutrons following a fission event in 43 fissioning systems. Least-squares techniques were used to produce fitted decay constants and abundances in the conventional six-group formalism from these calculated activity curves. A consistent set of six-group spectra have also been calculated for each of the fissioning systems. Recent measurements at the University of Lowell have produced measured energy spectra for delayed neutrons following the thermal fission (T) of {sup 235}U and {sup 239}Pu, and the fast fission (F) of {sup 238}U. These measured spectra provide data that may be used to validate the precursor data base and the fitted six-group data. This summary presents results of this validation effort. Both the individual precursor data and the six-group data have been used to calculate aggregate equilibrium spectra for {sup 235}U(T), {sup 238}U(F), and {sup 239}Pu(T) via summation techniques. The important precursors in each case are identified, and the status of their data reviewed. 8 refs., 3 figs., 3 tabs.
Date: January 1, 1989
Creator: Brady, M. C.; England, T. R. & ,
Partner: UNT Libraries Government Documents Department

Real-time fluid flow model for control of solidification

Description: The Atomic Vapor Laser Isotope Separation (AVLIS) process is an advanced uranium enrichment technology being developed by the Lawrence Livermore National Laboratory. This process is designed to increase the concentration of /sup 235/U in uranium from 0.7% as found in nature to approximately 3% as required for light water nuclear reactor fuel. Separation is accomplished by vaporizing uranium, selectively ionizing /sup 235/U atoms and electromagnetically collecting these ions. The electromagnetic collector system utilizes resistance heaters to maintain a temperature range defined by the melting point of the metal product and tails collected and the materials compatibility limits between the liquid metal and the structure. If temperatures are not within these bounds, metal freezing or structural damage may occur which disrupts the process. Additionally, inappropriate heater usage could result in heater burn-out or overheating.
Date: July 1, 1985
Creator: Kraftick, K. & Sholl, P.
Partner: UNT Libraries Government Documents Department