122 Matching Results

Search Results

Advanced search parameters have been applied.

Progress, status, and plans for the HRIBF project

Description: Over the last three years, the Holifield accelerator system has been reconfigured into a first-generation radioactive ion beam facility, the HRIBF, a national user facility for RIB research. The construction and reconfiguration have been completed and the equipment commissioning and beam development phases have started. The progress to date, the present status, and future plans will be given. The special problems connected with the production and acceleration of RIBs will be discussed.
Date: December 31, 1995
Creator: Auble, R.L.; Alton, G.D. & Bailey, J.D
Partner: UNT Libraries Government Documents Department

Target designs for the Brookhaven National Laboratory 5-MW pulsed spallation neutron source

Description: A feasibility study of a compact high power density target for a spallation neutron source was under-taken. The target arrangement consists primarily of heavy metal, with appropriate cooling passages. A high intensity proton beam of intermediate energy is directed at the target, where it interacts with the heavy metal nuclei. The subsequent spallation reactions produce several neutrons per proton resulting in an intense neutron source. The proton beam is assumed to havean energy of 5 MW, and to be cyclic with a repetition rate of 10Hz and 50Hz. The study was divided into two broad sections. First, an analysis of preliminary target designs was undertaken to ensure the overall feasibility of the concepts involved in the design and eventual construction of such a high power density target. Second, two proposed target designs, based on the first set of analyses, are investigated in more detail. Special care is taken to ensure that the neutron fluxes in the moderator are at the desired level no material compatibility problems exist,and the target is able to operate in a reliable and safe manner. Several target materials, coolant types, and target arrangements are investigated in the first section. The second section concentrates on a single target material and geometric arrangement. However, several structural material choices continue to be investigated with the aim of minimizing the effects of structural heating, and associated thermally induced stresses. In the final section the conclusions of this preliminary study are summarized.
Date: March 1, 1996
Creator: Ludewig, H.; Todosow, M. & Powell, J.R.
Partner: UNT Libraries Government Documents Department

An advanced ISOL facility based on ATLAS.

Description: The Argonne concept for an accelerator complex for efficiently producing high-quality radioactive beams from ion source energy up to 6-15 MeV/u is described. The Isotope-Separator-On-Line (ISOL) method is used. A high-power driver accelerator produces radionuclides in a target that is closely coupled to an ion source and mass separator. By using a driver accelerator which can deliver a variety of beams and energies the radionuclide production mechanisms can be chosen to optimize yields for the species of interest. To effectively utilize the high beam power of the driver two-step target/ion source geometries are proposed (1) Neutron production with intermediate energy deuterons on a primary target to produce neutron-rich fission products in a secondary {sup 238}U target, and (2) Fragmentation of neutron-rich heavy ion rich fission products in a secondary beams such as {sup 18}O in a target/catcher geometry. Heavy ion beams with total energies in the 1-10 GcV range are also available for radionuclide production via high-energy spallation reactions. At the present time R and D is in progress to develop superconducting resonator structures for a driver linac to cover the energy range up to 100 MeV per nucleon for heavy ions and 200 MeV for protons. The post accelerator scheme is based on using existing ISOL-type 1+ ion source technology followed by CW Radio Frequency Quadruple (RFQ) accelerators and superconducting linacs including the present ATLAS accelerator. A full-scale prototype of the first-stage RFQ has been successfully tested with RF at full design voltage and tests with ion beams are in progress. A benchmark beam, {sup 132}Sn {at} 7 MeV/u, requires two stripping stages, one a gas stripper at very low velocity after the first RFQ section, and one a foil stripper at higher velocity after a superconducting-linac injector.
Date: February 24, 1999
Creator: Nolen, J. A.
Partner: UNT Libraries Government Documents Department

Beta and gamma decay heat measurements between 0.1s-50,000s for neutron fission of {sup 235}U, {sup 238}U and {sup 239}Pu. Progress report, March 1, 1993--January 31, 1994

Description: Decay heat measurements following the fast fission of {sup 238}U are well underway. The He-jet system and spectrometers were moved to the 1 MW research reactor to gain sufficient fast neutron flux for these measurements. On the Van de Graaff accelerator, the He-jet capillary has been shortened so that beta and gamma measurements following the thermal neutron fission of {sup 235}U could be made down to delay times near 0.1 s. Gamma-ray response functions are now well characterized for gamma energies up to 1.5 MeV for our large Nal spectrometer. Such response functions out to high energies are needed to extract energy distributions of our measured gamma spectra. The response function unfolding program, FERD-PC, has been operated successfully with trial spectra. Comparisons of individual fission products for {sup 235}U(n{sub th}f) with ENDF/B-VI at short delay times suggest several improvements to the data base particularly in production probabilities. The new data acquisition and data analysis systems have arrived and will soon be brought on line extending considerably the capabilities of our research group.
Date: June 1, 1994
Creator: Schier, W. A. & Couchell, G. P.
Partner: UNT Libraries Government Documents Department

The effective (n,2n) cross section for U-238

Description: Neptunium-237 is currently produced in the Hanford reactors at a rate of approximately .003 gms/MWD via the following reactions: (a) U{sup 238} (n,2n) U{sup 237}{sup {beta}}{yields} Np{sup 237}. (b) U{sup 235} (n,{gamma}) U{sup 236} (n,{gamma}) U{sup 237}{sup {beta}}{yields} Np{sup 237}. In order to calculate the buildup of Np{sup 237} via reaction (a), which accounts for the greater share of the formation of Np{sup 237}, the n,2n cross section for U{sup 238} must be known. An old value quoted by Arnold of 5.2 millifermis for an {open_quotes}effective{close_quotes} 2200 m/s value is not large enough to account for the observed Np{sup 237} yield by about a factor of two. Recent n,2n cross section measurements for U{sup 238} permit a newer calculation and the result is 11.2 mF, effective 2200 m/s value.
Date: January 9, 1959
Creator: Nilson, R.
Partner: UNT Libraries Government Documents Department

Compton Backscattering Concept for the Production of Molybdenum-99

Description: The medical isotope Molybdenum-99 is presently used for 80-85% of all nuclear medicine procedures and is produced by irradiating highly enriched uranium U-235 targets in NRU reactors. It was recently proposed that an electron linac be used for the production of 99Mo via photo-fission of a natural uranium target coming from the excitation of the giant dipole resonance around 15 MeV. The photons can be produced using the braking radiation (“bremsstrahlung”) spectrum of an electron beam impinged on a high Z material. In this paper we present an alternate concept for the production of 99Mo which is also based on photo-fission of U-238, but where the ~15 MeV gamma-rays are produced by Compton backscattering of laser photons from relativistic electrons. We assume a laser wavelength of 330 nm, resulting in 485 MeV electron beam energy, and 10 mA of average current. Because the induced energy spread on the electron beam is a few percent, one may recover most of the electron beam energy, which substantially increases the efficiency of the system. The accelerator concept, based on a three-pass recirculation system with energy recovery, is described and efficiency estimates are presented.
Date: May 1, 2009
Creator: L. Merminga, G.A. Krafft
Partner: UNT Libraries Government Documents Department

Shielding analysis and design of the KIPT experimental neutron source facility of Ukraine.

Description: Argonne National Laboratory (ANL) of USA and Kharkov Institute of Physics and Technology (KIPT) of Ukraine have been collaborating on the conceptual design development of an experimental neutron source facility based on the use of an electron accelerator driven subcritical (ADS) facility [1]. The facility uses the existing electron accelerators of KIPT in Ukraine. The neutron source of the sub-critical assembly is generated from the interaction of 100 KW electron beam with a natural uranium target. The electron beam has a uniform spatial distribution and the electron energy in the range of 100 to 200 MeV, [2]. The main functions of the facility are the production of medical isotopes and the support of the Ukraine nuclear power industry. Reactor physics experiments and material performance characterization will also be carried out. The subcritical assembly is driven by neutrons generated by the electron beam interactions with the target material. A fraction of these neutrons has an energy above 50 MeV generated through the photo nuclear interactions. This neutron fraction is very small and it has an insignificant contribution to the subcritical assembly performance. However, these high energy neutrons are difficult to shield and they can be slowed down only through the inelastic scattering with heavy isotopes. Therefore the shielding design of this facility is more challenging relative to fission reactors. To attenuate these high energy neutrons, heavy metals (tungsten, iron, etc.) should be used. To reduce the construction cost, heavy concrete with 4.8 g/cm{sup 3} density is selected as a shielding material. The iron weight fraction in this concrete is about 0.6. The shape and thickness of the heavy concrete shield are defined to reduce the biological dose equivalent outside the shield to an acceptable level during operation. At the same time, special attention was give to reduce the total shield mass ...
Date: October 31, 2008
Creator: Zhong, Z.; Gohar, M. Y. A.; Naberezhnev, D. & Duo, J.
Partner: UNT Libraries Government Documents Department

Physics design of a cold neutron source for KIPT neutron source facility.

Description: Argonne National Laboratory (ANL) of USA and Kharkov Institute of Physics and Technology (KIPT) of Ukraine have been collaborating on the conceptual design development of a neutron source facility. It is based on the use of an electron accelerator driven subcritical (ADS) facility with low enriched uranium fuel, using the existing electron accelerators at KIPT of Ukraine [1]. The neutron source of the subcritical assembly is generated from the interaction of 100-KW electron beam, which has a uniform spatial distribution and the electron energy in the range of 100 to 200 MeV, with a natural uranium target [2]. The main functions of the facility are the production of medical isotopes and the support of the Ukraine nuclear power industry. Neutron beam experiments and material studies are also included. Over the past two-three decades, structures with characteristic lengths of 100 {angstrom} and correspondingly smaller vibrational energies have become increasingly important for both science and technology [3]. The characteristic dimensions of the microstructures can be well matched by neutrons with longer vibrational wavelength and lower energy. In the accelerator-driven subcritical facility, most of the neutrons are generated from fission reactions with energy in the MeV range. They are slowed down to the meV energy range through scattering reactions in the moderator and reflector materials. However, the fraction of neutrons with energies less than 5 meV in a normal moderator spectrum is very low because of up-scattering caused by the thermal motion of moderator or reflector molecules. In order to obtain neutrons with energy less than 5 meV, cryogenically cooled moderators 'cold neutron sources' should be used to slow down the neutrons. These cold moderators shift the neutron energy spectrum down because the thermal motion of moderator molecules as well as the up-scattering is very small, which provides large gains in intensity of ...
Date: February 17, 2009
Creator: Zhong, Z.; Gohar, Y. & Kellogg, R.
Partner: UNT Libraries Government Documents Department

150-m measurement of 0. 880- to 100. 0-keV neutron transmissions through four samples of /sup 238/U

Description: In order to study the /sup 238/U + n total cross section, neutron transmissions through 0.076-, 0.254-, 1.080-, and 3.620-cm-thick samples of isotopically enriched /sup 238/U have been measured from 0.880 to 100.0 keV using a time-of-flight technique over a path length of 150 meters with the ORELA pulsed source and a 13-mm-thick Li-glass detector. The measurement is described in detail and both a listing and figures of the resulting transmissions are given. An absolute energy scale accurate to 2 parts in 10,000 was established.
Date: October 1, 1977
Creator: Olsen, D. K.; de Saussure, G.; Perez, R. B.; Difilippo, F. C.; Ingle, R. W. & Weaver, H.
Partner: UNT Libraries Government Documents Department

Assessment of some optical model potentials in predicting neutron cross sections

Description: Optical model potential parameters play an important role in the evaluation of nuclear data for applied purposes. The IAEA Coordinated Research Program on {open_quotes}Reference Input Parameter Library for Evaluation of Nuclear Data for Application in Nuclear Technology{close_quotes} aims to release a reference input file of various types of parameters for the evaluation of nuclear cross sections using nuclear model codes. Included in the parameter files are a collection of optical model potentials that are available in the literature to evaluate these cross sections. As part of this research program we assess the applicability of these potentials over a range of target mass and projectile energy.
Date: March 1, 1998
Creator: Kumar, A.; Young, P.G. & Chadwick, M.B.
Partner: UNT Libraries Government Documents Department

Neutron scattering from elemental uranium and thorium

Description: Differential neutron-scattering cross sections of elemental uranium and thorium are measured from {approx} 4.5 to 10.0 MeV in steps of {approx} 0.5 MeV. Forty or more differential values are obtained at each incident energy, distributed between {approx} 17{degree} and 160{degree}. Scattered-neutron resolutions are carefully defined to encompass contributions from the first four members of the ground-state rotational band (0{sup 2} g.s., 2{sup +}, 4{sup +} and 6{sup +} states). The experimental results are interpreted in the context of coupled-channels rotational models, and comparisons made with the respective ENDF/B-VI evaluated files. These comparisons suggest some modifications of the ENDF/B-VI {sup 238}U and {sup 232}Th evaluations.
Date: January 1, 1995
Creator: Smith, A.B. & Chiba, S.
Partner: UNT Libraries Government Documents Department

Influence of the incident particle energy on the fission product mass distribution.

Description: For {sup 238}U targets and the five elements considered here, the best yields of neutron-rich isotopes are obtained from neutrons in the 2-20 MeV range. High energy beams of neutrons, protons, and deuterons have comparable integral yields per element to neutrons below 20 MeV, but the distributions are peaked at lower neutron numbers. This is presumably due to a higher neutron multiplicity in the pre-equilibrium stage and/or the compound nucleus/fission stage. For {sup 235}U targets there are high yields predicted especially for thermal neutrons, and also for the fast neutron spectrum. For the high energy neutrons, protons, and deuterons {sup 235}U has no advantage over {sup 238}U. A detailed comparison of the relative advantages of {sup 235}U and {sup 238}U for radioactive beam applications is beyond the scope of this study and will be addressed in the future. The present work is the first step of a more detailed analysis of various possible one- and two-step target geometry calculated with the LAHET code system. It is intended to serve as a guide in choosing geometry and beams for future studies. It is desirable to extend this study to higher beam energies, e.g. 200 to 1000 MeV, but at this time there is very little data against which to benchmark the analysis. Additional data would also permit comparisons of isotope yields beyond the tails of the distributions presented here, to even more neutron rich isotopes.
Date: August 26, 1998
Creator: Gomes, I. C.
Partner: UNT Libraries Government Documents Department

Results from the Argonne, Los Alamos, JAERI collaboration

Description: Four sample packets containing elemental Ti, Fe, Ni, Cu, Nb, Ag, Eu, Tb and Hf have been irradiated in three distinct accelerator neutron fields, at Argonne National Laboratory and Los Alamos National Laboratory, USA, and Japan Atomic Energy Research Institute, Tokai, Japan. The acquired experimental data include differential cross sections and integral cross sections for the continuum neutron spectrum produced by 7-MeV deuterons incident on thick Be-metal target. The U-238(n,f) cross section was also measured at 10.3 MeV as a consistency check on the experimental technique. This the third progress report on a project which has been carried out under the auspices of an IAEA Coordinated Research Program entitled ``Activation Cross Sections for the Generation Of Long-lived Radionuclides of Importance in Fusion Reactor Technology``. The present report provides the latest results from this work. Comparison is made between the 14.7-MeV cross-section values obtained from the separate investigations at Argonne and JAERI. Generally, good agreement observed within the experimental errors when consistent sample parameters, radioactivity decay data and reference cross values are employed. A comparison is also made between the experimental results and those derived from calculations using a nuclear model. Experimental neutron information on the Be(d,n) neutron spectrum was incorporated in the comparisons for the integral results. The agreement is satisfactory considering the various uncertainties that are involved.
Date: July 1, 1993
Creator: Meadows, J.; Smith, D.; Greenwood, L.; Haight, R.; Ikeda, Y. & Konno, C.
Partner: UNT Libraries Government Documents Department

SUR, a program to generate error covariance files

Description: Covariance matrices were calculated for the $sup 238$U, $sup 241$Pu, and $sup 239$Pu fission cross sections and for the $sub 23$$sub 8$ $sup 240$Pu, $sup 241$Pu, and $sup 239$Pu capture cross sections. A computer program was written which uses the evaluated ENDF/B data files and the measured or evaluated (from other evaluations) cross sections for the calculation of the uncertainty files. An effort has been made to make the output of the program consistent with the ENDF/B error files format. A user's manual for the present code and references utilized in the covariance matrix calculations are given. (auth)
Date: March 1, 1976
Creator: Difilippo, F.C.
Partner: UNT Libraries Government Documents Department

Delayed neutron yield of $sup 238$U and $sup 241$Pu

Description: The total delayed neutron yield for $sup 238$U and $sup 241$Pu were observed as a function of the incident neutron energy. The measurements extend from 2.5 to 5 MeV for $sup 238$U and from 0.15 to 5 MeV for $sup 241$Pu. The average ratio of the $sup 241$Pu delayed neutron yield to that of $sup 238$U is 0.292 +- 0.022.
Date: January 1, 1976
Creator: Meadows, J.W.
Partner: UNT Libraries Government Documents Department

Comparison of measured and calculated /sup 238/U capture self-indication ratios from 4 to 10 keV

Description: From 4 keV to 149 keV the /sup 238/U cross sections are represented in ENDF/B-V by unresolved-resonance parameters (URP). The purpose of this representation is to enable the calculation of resonance self-protection as a function of temperature and dilution. Since the URPs are not defined unambiguously by the cross-section data, it is important that the unresolved representation be tested with appropriate experiments, such as capture self-indication ratio (SIR) measurements. In this paper we compare /sup 238/U capture SIR measurements in the 4- to 10-keV energy range with calculations done with ENDF/B-V and with recently published resolved resonance parameters.
Date: January 1, 1983
Creator: Perez, R.B.; de Saussure, G.; Yang, J.T.; Munoz-Cobos, J.L. & Todd, J.H.
Partner: UNT Libraries Government Documents Department

Evaluation of the /sup 238/U neutron cross sections for incident neutron energies up to 4 keV

Description: This report describes an evaluation of the /sup 238/U cross sections below 4 keV. Recent measurements and reanalyses of older data are discussed. Evaluated resonance parameters are obtained for 164 s-wave and 280 p-wave levels. The capture widths of the first three s-wave levels are significantly lower than in the ENDF/B-IV evaluation. The s-wave strength function above 1.5 keV is sytematically larger than in ENDF/B-IV. Statistical and systematic uncertainties are evaluated for the resonance parameters and for the smooth backgrounds. The statistical distributions of the resonance parameters are compared with theoretically expected distributions.
Date: January 1, 1978
Creator: de Saussure, G.; Olsen, D.K.; Perez, R.B. & Difilippo, F.C.
Partner: UNT Libraries Government Documents Department

High-intensity, thin-target He-jet production source

Description: A thin-target He-jet system suited to the production and rapid transport of non-volatile radioactive species has been successfully operated with proton beam intensities of up to 700 {mu}A. The system consists of a water-cooled, thin-target chamber, capillary gas transport system, moving tape/Ge detection system, and an aerosol generator/gas recirculator. The yields for a wide variety of uranium fission and deep spallation products have been measured and robust operation of the system demonstrated for several weeks. He-jet transport and collection efficiencies ranged between 15 and 25% with collection rates of 10{sup 7} to 10{sup 8} atoms/sec/isotope. The high-intensity, thin-target He-jet approach represents a robust production source for nonvolatile radioactive heavy ion beams.
Date: December 31, 1996
Creator: Bai, Y.; Vieira, D.J.; Wouters, J.M.; Butler, G.W.; Rosenauer, Dk; Loebner, K.E.G. et al.
Partner: UNT Libraries Government Documents Department

The simultaneous evaluation of the standards and other cross sections of importance for technology

Description: The simultaneous evaluation of the cross sections of {sup 6}Li(n,{alpha}), {sup 6}Li(n,n), {sup 10}B(n,{alpha}{sub 0}), {sup 10}B(n,{alpha}{sup 1}), {sup 10}B(n,n), {sup 197}Au(n,{gamma}), {sup 238}U(n,{gamma}), {sup 235}U(n,f), {sup 239}Pu(n,f), and {sup 238}U(n,f) and the thermal constants was part of the evaluation of these data for ENDF/B-VI The FORTRAN codes and the data files used for the simultaneous evaluation are documented in the present report. Corrections for some data reported in the literature and the addition of several new data sets results in negligible changes except for the fission cross sections where minor changes occur relative to the evaluation for ENDF/B-VI.
Date: September 1, 1997
Creator: Poenitz, W.P. & Aumeier, S.E.
Partner: UNT Libraries Government Documents Department

High energy resolution measurement of the /sup 238/U neutron capture yield in the energy region between 1 and 100 keV

Description: A measurement of the /sup 238/U neutron capture yield was performed at the 150 meter flight-path of the ORELA facility on two /sup 238/U samples (0.01224 and 0.0031 atomsbarn). The capture yeild data were normalized by Moxon's small resonance method. The energy resolution achieved in this measurement frequently resulted in doublet and triplet splittings of what appeared to be single resonance in previous measurements. This resolution should allow extension of the resolved resonance energy region in /sup 238/U from the present 4-keV limit up to 15 or 20 keV incident neutron energy. Some 200 small resonances of the (/sup 238/U /plus/ n) compound nucleus have been observed which had not been detected in transmission measurement, in the energy range from 250 eV to 10 keV.
Date: January 1, 1988
Creator: Machlin, R.L.; Perez, R.B.; de Saussure, G. & Ingle, R.W.
Partner: UNT Libraries Government Documents Department

0. 9 a Gev /sup 238/U on /sup 238/U collisions in the LBL streamer chamber. Appendix A

Description: Charged particle exclusive data for high multiplicity U on U events are reported. Analyses are based on comparison with Cugnon's intranuclear cascade model, and the explosion-evaporation simulation of Fai and Randrup. The azimuthal structure of the observed events shows evidence of collective flow. The widely used flow angle methodology proves to be relatively insensitive to collective effects under the conditions of the present experiment. An isotropic pattern of ejectile emission is not reached at maximum multiplicity. 18 refs., 4 figs.
Date: January 1, 1984
Creator: Fung, S.Y.; Beavis, D.; Gorn, W.; Keane, D.; Liu, Y.M.; Poe, R.T. et al.
Partner: UNT Libraries Government Documents Department

Resolved resonance parameters for uranium 238 from 4 to 6 keV

Description: Neutron widths for 145 resonances from 4 to 6 keV are reported from a least-squares shape analysis of the ORELA 150-m, 4-sample /sup 238/U transmission data. The resultant s-wave strength function from 4 to 6 keV is found to be substantially smaller than that from 0 to 4 keV.
Date: January 1, 1982
Creator: Olsen, D.K. & Meszaros, P.S.
Partner: UNT Libraries Government Documents Department