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in subjects: "Fast Neutrons"

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Sensitivity of primary knock-on atom spectra and displacement per atom cross sections to different secondary neutron energy and angular distributions and ''in-group'' weighting schemes

The sensitivity of primary knock-on atom (PKA) spectra and displacement per atom (DPA) cross sections to different secondary neutron energy and angular distributions and ''in-group'' weighting schemes is investigated. It is shown that the sensitivity of the PKA spectra and DPA cross sections for the (n,n' unresolved) and (n,2n) reactions in Fe to different angular distributions and the same secondary neutron spectrum is reasonably large (approximately 15%), whereas the … more

Date: January 1, 1978

Creator: Gabriel, T. A. & Bishop, B. L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Radiation standards and calibrations. FY-1981 annual report

The research program encompasses: reviewing calibration standards, regulations, and handbooks; assuring that calibration procedures used are in agreement with technically accepted methods; maintaining basic radioactive sources and instruments that serve as radiological standards; and providing traceability to the National Bureau of Standards where possible. In addition, major efforts are being expended to upgrade the 318 calibration facility. This report focuses on major accomplishments during … more

Date: July 1, 1982

Creator: Roberson, P. L.; Yoder, R. C.; Fox, R. A.; Hooker, C. D.; Hogan, R. T.; Holbrook, K. L. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

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 s… more

Date: January 1, 1988

Creator: Harvey, J.A.; Hill, N.W.; Perey, F.G.; Tweed, G.L. & Leal, L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Dosimetry measurements external to a 10 kiloliter liquid-air vessel containing a D-T neutron source. [14 MeV neutrons]

To determine the radiation attenuation characteristics of liquid air (109 g/cm/sup 2/ thick) for 14 MeV neutrons from a central D-T source in a 10 kL vessel, radiation dose measurements were made using a large tissue-equivalent ion chamber external to the vessel. The shielding characteristics of steel spherical shells were also investigated. Experimental results were analyzed and compared with TARTNP Monte Carlo code calculations. Degradation of the ion chamber's response to high-energy neutron… more

Date: October 10, 1977

Creator: Tripler, D. J.; Goldberg, E. & Farley, W. E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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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… more

Date: January 1, 1988

Creator: Smith, A. B. & Lawson, R. D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Energy-averaged neutron cross sections of fast-reactor structural materials

The status of energy-averaged cross sections of fast-reactor structural materials is outlined with emphasis on U.S. data programs in the neutron-energy range 1-10 MeV. Areas of outstanding accomplishment and significant uncertainty are noted with recommendations for future efforts. Attention is primarily given to the main constituents of stainless steel (e.g., Fe, Ni, and Cr) and, secondarily, to alternate structural materials (e.g., V, Ti, Nb, Mo, Zr). Generally, the mass regions of interest a… more

Date: February 1, 1978

Creator: Smith, A.; McKnight, R. & Smith, D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Evaluation of resonance parameters for neutron interaction with iron isotopes for energies up to 400 keV

The evaluation of the resolved resonance parameters of iron isotopes 54, 56, and 57 in the neutron energy region below 400 keV is documented. Estimates of the uncertainties in the resonance parameters and correlation between the partial widths GAMMA/sub n/ and GAMMA/sub ..gamma../ are given when significant. Some details about the procedures used to evaluate the resonance parameters, their uncertainties, and correlations are reported. This evaluation was performed for the general-purpose file o… more

Date: September 1, 1980

Creator: Perey, C.M. & Perey, F.G.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Experimental evaluation of the differential die-away pulsed-neutron technique for the fissile assay of hot irradiated fuel waste

Hot irradiated fuel waste packages containing self neutron sources up to 10/sup 7/ n/s may be assayed successfully with a 25-mg /sup 239/Pu detection sensitivity using a differential die-away fissile assay system based on a Sandia-designed 14-MeV neutron generator. With a minor design change, our system can accommodate contact gamma dose rates up to 10/sup 4/ R/h with no loss of fissile assay sensitivity.

Date: January 1, 1982

Creator: Caldwell, J.T. & Kunz, W.E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Calculation of /sup 59/Co neutron cross sections between 3 and 50 MeV

Knowledge of the /sup 59/Co(n,p), (n,..cap alpha..), and (n,xn) cross sections up to 50 MeV are necessary to satisfy priority dosimetry data needs of the FMIT facility. Since experimental data extend only to 25 MeV in the case of (n,xn) reactions (and lower energies for the others), these cross sections as well as those from competing reactions were calculated for neutron energies between 3 and 50 MeV. Neutron optical parameters were determined that were valid from several hundreds of keV to 50… more

Date: January 1, 1980

Creator: Arthur, E. D.; Young, P. G. & Matthes, W. K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Fast-neutron total and scattering cross sections of /sup 58/Ni

Neutron total cross sections of /sup 58/Ni were measured at 25 keV intervals from 0.9 to 4.5 MeV with 50 to 100 keV resolutions. Attention was given to self-shielding corrections to the observed total cross sections. Differential elastic- and inelastic-scattering cross sections were measured at 50 keV intervals from 1.35 to 4.0 MeV with 50 to 100 keV resolutions. Inelastic excitation of levels at 1.458 +- 0.009, 2.462 +- 0.010, 2.791 +- 0.015, 2.927 +- 0.012 and 3.059 +- 0.025 MeV was observed.… more

Date: September 1, 1981

Creator: Jorgensen, C. B.; Guenther, P. T.; Smith, A. B. & Whalen, J. F.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Calculational methods used to obtain evaluated data above 3 MeV

Calculational methods used to provide evaluated neutron data for nuclei between A = 19 and 220 at incident energies above several MeV range from empirical techniques based on cross-section systematics to sophisticated nuclear-model codes that describe the major mechanisms governing neutron reactions in this mass and energy range. Examples of empirical approaches are given along with discussion concerning regions of applicability and accuracies that can be expected. The application of more sophi… more

Date: January 1, 1980

Creator: Arthur, E. D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Neutron cross section measurements at ORELA

ORELA (Oak Ridge Electron Linear Accelerator) has been for the last decade the most powerful and useful pulsed neutron time-of-flight facility in the world, particularly in the broad midrange of neutron energies (10 eV to 1 MeV). This position will be enhanced with the addition of a pulse narrowing prebuncher, recently installed and now under test. Neutron capture, fission, scattering, and total cross sections are measured by members of the Physics and Engineering Physics Divisions of ORNL, and… more

Date: January 1, 1979

Creator: Dabbs, J. W. T.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Evaluation of different polymers for fast neutron personnel dosimetry using electrochemical etching

There is considerable optimism for the enhancement by electrochemical etching of fast neutron-induced recoil tracks in polycarbonate for the purpose of personnel dosimetry. The threshold energy, however, is rather high. A desirable improvement would be to lower this energy below 1 MeV. With this objective in mind, we have commenced an investigation of cellulose acetate, triacetate, and acetobutyrate in addition to polycarbonate. These cellulose derivatives are chemically more reactive and physi… more

Date: January 1, 1977

Creator: Gammage, R.B. & Cotter, S.J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Fast-neutron and photon doses determined with proportional counters and ionization chambers

A /sup 60/Co teletherapy source has recently been coupled to an existing source of fast neutrons. These sources may be operated to provide precise and controlled mixtures of photons and neutrons. In this work we report the application of paired miniature proportional counters to n/..gamma.. dose separation. Graphite- and A150 plastic-walled proportional counters were employed. Results are compared to dose values deduced from a cnventional A150 plastic ionization chamber and a neutron insensitiv… more

Date: January 1, 1981

Creator: DeLuca Jr., P. M.; Higgins, P. D.; Schell, M. C. & Pearson, D. W.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Design and safety report for HOBBIE capsules. A series of Zircaloy creepdown irradiation tests

The design and safety features of a series of irradiation experiments designed to study the in-reactor creepdown behavior of Zircaloy tubing typical of LWR fuel cladding are presented.

Date: December 1, 1977

Creator: Thoms, K.R. & van der Kaa, T.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Evaluated fast neutron cross sections of uranium-238. [0. 045 to 20. 0 MeV]

An evaluated fast neutron data file of /sup 238/U is presented in the ENDF/B format. The incident energy range extends from 0.045 to 20.0 MeV. The content consists of: (1) neutron total cross sections, (2) fission cross sections, neutron emission spectra and associated properties, (4) neutron radiative-capture cross sections, (5) (n;2n') and (n;3n') processes, and (6) photon-production cross sections and spectra. The methodology of the file derivation is outlined. File content is graphically il… more

Date: October 1, 1977

Creator: Poenitz, W.; Pennington, E.; Smith, A. & Howerton, R.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

ORELA measurements to meet fusion energy neutron cross section needs. [2 to 80 MeV]

Major neutron cross section measurements made at the Oak Ridge Electron Linear Accelerator (ORELA) that are useful to the fusion energy program are reviewed. Cross sections for production of gamma rays with energies 0.3 < E/sub ..gamma../ < 10.5 MeV were measured as a function of neutron energy over the range 0.1 < E/sub n/ < 20.0 MeV for Li, C, N, O, F, Na, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Nb, Mo, Ag, Sn, Ta, W, Au, Pb, and Th. Neutron emission cross sections have been measured f… more

Date: January 1, 1980

Creator: Larson, D.C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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ORNL irradiation creep facility

A machine was developed at ORNL to measure the rates of elongation observed under irradiation in stressed materials. The source of radiation is a beam of 60 MeV alpha particles from the Oak Ridge Isochronous Cyclotron (ORIC). This choice allows experiments to be performed which simulate the effects of fast neutrons. A brief review of irradiation creep and experimental constraints associated with each measurement technique is given. Factors are presented which lead to the experimental choices ma… more

Date: September 1, 1980

Creator: Reiley, T. C.; Auble, R. L.; Beckers, R. M.; Bloom, E. E.; Duncan, M. G.; Saltmarsh, M. J. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Study of optical model parameters for high energy neutron cross sections from 5 to 50 MeV in the mass-140 region

A study of the neutron optical potential on nuclei near mass-140 was begun to extend the energy range and improve the precision of previous neutron total cross section measurements. The extended energy range of this measurement reveals maxima and minima in the total cross section that are evidence of the nuclear Ramsauer effect. A 100-MeV linear accelerator is used to produce a continuum of neutron energies from a Ta-Be conversion target. A 250-meter flight path is used to measure neutron energ… more

Date: May 8, 1980

Creator: Phillips, T.W.; Camarda, H.S. & White, R.M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Application of A150-plastic equivalent gases in microdosimetric measurements

Neutron dosimetry measurements with ionization chambers, for the most part, employ tissue equivalent plastic-walled cavities (Shonka A150) filled with either air or a methane-base tissue-like gas. The atomic composition of TE-gas and A150 plastic are not matched and are quite dissimilar from muscle. Awschalom and Attix (1980) have partially resolved the problem by formulating a novel A150-plastic equivalent gas. This establishes a homogeneous wall-gas cavity dosimeter for neutron measurements a… more

Date: January 1, 1981

Creator: DeLuca, P.M. Jr.; Higgins, P.D.; Pearson, D.W.; Schell, M. & Attix, F.H.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Evaluation of neutron cross sections to 40 MeV for /sup 54/ /sup 56/Fe

Cross sections for neutron-induced reactions on /sup 54/ /sup 56/Fe were calculated by employing several nuclear models: optical, Hauser-Feshbach, preequilibrium and DWBA - in the energy range between 3 and 40 MeV. As a prelude to the calculations, the necessary input parameters were determined or verified through analysis of a large body of experimental data for both neutron- and proton-induced reactions in this mass and energy region. This technique also led to cross sections in which the sim… more

Date: January 1, 1980

Creator: Arthur, E. D. & Young, P. G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Small-angle neutron scattering from voids in neutron irradiated type 304 stainless steel. [E > 0. 1 MeV]

Preliminary small-angle neutron scattering results designed to investigate the structure of voids in neutron-irradiated polycrystalline annealed type 304 stainless steel were obtained. Specimens were subjected to irradiation at 400/sup 0/C to a fluence of 1.6 x 10/sup 23/ n/cm/sup 2/ (E > 0.1 MeV). Void interference effects were seen for voids having an average diameter of about 290 A. The distribution was ''gas-like''with an exclusion distance of 307 A. 1 figure, 1 table. (RWR)

Date: September 1, 1977

Creator: Child, H.R. & Spooner, S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Radiobiology of pions at LAMPF

Recent radiobiology data for pion beams used in therapy are presented. The biological systems used were cultured cells suspended in gelatin and intestinal crypt assay. The importance of fast neutrons from pion stars in large treatment volumes is discussed. The data for compensating the depth dose distribution to produce uniform cell killing across the peak region are presented. The changes in biological effectiveness with peak width for pion beams (unlike heavy ions) are small because of fast n… more

Date: January 1, 1982

Creator: Raju, M.R. & Tokita, N.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Post-irradiation recovery of growth in Zircaloy. [Fast neutron irradiation]

The previously reported model for fast neutron induced growth in Zircaloy has been modified to predict post-irradiation recovery of the growth. The predicted results are compared to growth recovery data obtained by Adamson. Agreement is good if the binding energy between vacancies and depleted zones is reduced from the in-pile value of 1.1 eV to a post-irradiation value of 1.0 eV. Such a reduction is reasonable.

Date: December 1977

Creator: Dollins, C. C.

Item Type: Report

Partner: UNT Libraries Government Documents Department