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Neutron Cross Section Uncertainties in the Thermal and Resonance Regions

Description: In the 'Atlas of Neutron Resonances', special care was expended to ensure that the resonance parameter information reproduces the various measured thermal cross sections, as well as the infinite dilute resonance integrals for Z = 1-100. In contrast, the uncertainties of the recommended quantities do not match those generated from the uncertainties of the resonance parameters. To address this problem, the present study was initiated to achieve consistency for 15 actinides and 21 structural and coolant moderator materials. This is realized by assigning uncertainties to the parameters of the negative-energy resonances and changing, if necessary, significantly the uncertainties of the low-lying positive-energy resonances. The influence of correlations between parameters on the derived uncertainties is examined and discussed.
Date: June 24, 2008
Creator: Mughabghab,S.F. & Oblozinsky, P.
Partner: UNT Libraries Government Documents Department

Thermal neutron cross sections and resonance integrals for the 1994 handbook of chemistry and physics

Description: A re-evaluation of all thermal neutron cross sections and neutron resonance integrals has been performed, utilizing the previous database of the ``Barn Book`` and all of the more recently published experiments. Only significant changes or previously undetermined values are recorded in this report. The source for each value is also recorded in the accompanying table.
Date: December 31, 1994
Creator: Holden, N.E.
Partner: UNT Libraries Government Documents Department

Neutron total and capture cross section measurements and resonance parameter analysis of tungsten from 0.01 eV to 200 eV

Description: Natural tungsten metal was measured using neutron time-of-flight spectroscopy at the Rensselaer Polytechnic Institute (RPI) Gaerttner Laboratory linear accelerator to determine the tungsten resonance parameters. Three separate measurements were performed: transmission, capture, and self-indication. Previous measurements did not employ all three experiment types and used less sophisticated methods. The current work improves on the published tungsten data base and reduces resonance parameter uncertainties.
Date: June 15, 1998
Creator: Werner, C.J.; Block, R.C.; Slovacek, R.E.; Overberg, M.E.; Moretti, B.E.; Burke, J.A. et al.
Partner: UNT Libraries Government Documents Department

Introduction to the Theory and Analysis of Resolved (and Unresolved) Neutron Resonances via SAMMY

Description: Neutron cross-section data are important for two purposes: First, they provide insight into the nature of matter, increasing our understanding of fundamental physics. Second, they are needed for practical applications (e.g., for calculating when and how a reactor will become critical, or how much shielding is needed for storage of nuclear materials, or for medical applications). Neutron cross section data in the resolved-resonance region are generally obtained by time-of-flight experiments, which must be carefully analyzed if they are to be properly understood and utilized. In this report, important features of the analysis process are discussed, with emphasis on the particular techniques used in the analysis code SAMMY. Other features of the code are also described; these include such topics as calculation of group cross sections (including covariance matrices), generation and fitting of integral quantities, and extensions into the unresolved-resonance region and higher-energy regions.
Date: March 13, 2000
Creator: Larson, N.
Partner: UNT Libraries Government Documents Department

A SIMPLE FORMULA FOR COMPUTING FISSION PRODUCT THERMAL CROSS SECTIONS AND RESONANCE INTEGRALS

Description: A simple formula for computing fission product thermal cross sections and resonance integrals as a function of exposure is presented. Results determined by this formula agreed with those of previously published calculations to within four per cent. The formula was used in calculating the effective cross section and resonance integral as functions of fuel-processing cycle time in fluid-fueled reactors. (auth)
Date: April 1, 1960
Creator: Nestor, C W
Partner: UNT Libraries Government Documents Department

2007 Nuclear Data Review

Description: The results of a review and evaluation of neutron and non-neutron nuclear data published in the scientific literature are presented. The status of new chemical elements is examined. Data on revised values for the isotopic composition of the elements are reviewed and recommended values are presented. Half-lives of very long-lived nuclides are presented, including double beta decay, double electron capture, long-lived alpha decay and long-lived beta decay. Data from new measurements on the very heavy elements (trans-meitnerium elements) are discussed and tabulated. The first observation of the radioactive decay mode of the free neutron is discussed. New measurements that have expanded the neutron drip line for magnesium and aluminum are discussed. Data on recent neutron cross-section and resonance integral measurements are also discussed.
Date: May 5, 2008
Creator: Holden,N.E.
Partner: UNT Libraries Government Documents Department

Nuclear Data Resources for Capture gamma-Ray Spectroscopy and Related Topics

Description: Nuclear reaction data play an important role in nuclear reactor, medical, and fundamental science and national security applications. The wealth of information is stored in internally adopted ENDF-6 and EXFOR formats. We present a complete calculation of resonance integrals, Westcott factors, thermal and Maxwellian-averaged cross sections for Z = 1-100 using evaluated nuclear reaction data. The addition of newly-evaluated neutron reaction libraries, and improvements in data processing techniques allows us to calculate nuclear industry and astrophysics parameters, and provide additional insights on all currently available neutron-induced reaction data. Nuclear reaction calculations will be discussed and an overview of the latest reaction data developments will be given.
Date: August 18, 2011
Creator: Pritychenko, B. & Pritychenko,B.
Partner: UNT Libraries Government Documents Department

Hafnium Resonance Parameter Analysis Using Neutron Capture and Transmission Experiments

Description: The focus of this work is to determine the resonance parameters for stable hafnium isotopes in the 0.005 - 200 eV region, with special emphasis on the overlapping {sup 176}Hf and {sup 178}Hf resonances near 8 eV. Accurate hafnium cross sections and resonance parameters are needed in order to quantify the effects of hafnium found in zirconium, a metal commonly used in reactors. The accuracy of the cross sections and the corresponding resonance parameters used in current nuclear analysis tools are rapidly becoming the limiting factor in reducing the overall uncertainty on reactor physics calculations. Experiments measuring neutron capture and transmission are routinely performed at the Rensselaer Polytechnic Institute (RPI) LINAC using the time-of flight technique. {sup 6}Li glass scintillation detectors were used for transmission experiments at flight path lengths of 15 and 25 m, respectively. Capture experiments were performed using a sixteen section NaI multiplicity detector at a flight path length of 25 m. These experiments utilized several thicknesses of metallic and isotope-enriched liquid Hf samples. The liquid Hf samples were designed to provide information on the {sup 176}Hf and {sup 178}Hf contributions to the 8 eV doublet without saturation. Data analyses were performed using the R-matrix Bayesian code SAMMY. A combined capture and transmission data analysis yielded resonance parameters for all hafnium isotopes from 0.005 - 200 eV. Additionally, resonance integrals were calculated, along with errors for each hafnium isotope, using the NJOY and INTER codes. The isotopic resonance integrals calculated were significantly different than previous values. The {sup 176}Hf resonance integral, based on this work, is approximately 73% higher than the ENDF/B-VI value. This is due primarily to the changes to resonance parameters in the 8 eV resonance, the neutron width presented in this work is more than twice that of the previous value. The calculated elemental ...
Date: February 6, 2007
Creator: Trbovich, M J; Barry, D P; Slovacek, R E; Danon, Y; Block, R C; Francis, N C et al.
Partner: UNT Libraries Government Documents Department

Neutron Resonance Parameters of 238U and the Calculated Cross Sections from the Reich-Moore Analysis of Experimental Data in the Neutron Energy Range from 0 keV to 20 keV

Description: The neutron resonance parameters of {sup 238}U were obtained from a SAMMY analysis of high-resolution neutron transmission measurements and high-resolution capture cross section measurements performed at the Oak Ridge Electron Linear Accelerator (ORELA) in the years 1970-1990, and from more recent transmission and capture cross section measurements performed at the Geel Linear Accelerator (GELINA). Compared with previous evaluations, the energy range for this resonance analysis was extended from 10 to 20 keV, taking advantage of the high resolution of the most recent ORELA transmission measurements. The experimental database and the method of analysis are described in this report. The neutron transmissions and the capture cross sections calculated with the resonance parameters are compared with the experimental data. A description is given of the statistical properties of the resonance parameters and of the recommended values of the average parameters. The new evaluation results in a slight decrease of the effective capture resonance integral and improves the prediction of integral thermal benchmarks by 70 pcm to 200 pcm.
Date: December 5, 2005
Creator: Derrien, H
Partner: UNT Libraries Government Documents Department

1559/RE: A CODE TO COMPUTE RESONANCE INTEGRALS IN MIXTURES

Description: The computer program 1559/RE is an experimental IBM-704 code in FORTRAN language for computing the resonance integrals of isotopes in mixtures in the presence of hydrogenic moderation. There may be up to four isotopes, each with no more than 75 resolved resonance levels. Doppler broadening and interference scattering are included No estimate is made of contributions from unresolved resonances. Typical running times are 30 min (with no Doppler broadening) to 90 min (with Doppler broadening) for problems involving 67 levels and unit lethargy widths. Input and theory are discussed, and a typical listing is given. (auth)
Date: May 1, 1963
Creator: Kelber, C.N.
Partner: UNT Libraries Government Documents Department

2002 REVIEW OF NEUTRON AND NON NEUTRON NUCLEAR DATA.

Description: Review articles are in preparation for the 2003 edition of the CRC's Handbook of Chemistry and Physics dealing with both non-neutron and neutron nuclear data. Highlights include: withdrawal of the claim for discovery of element 118; new measurements of isotopic abundances have led to changes for many elements; a new set of recommended standards for calibration of {gamma}-ray energies have been published for many nuclides; new half-life measurements reported for very short lived isotopes, many long-lived nuclides and {beta}{beta} decay measurements for quasi-stable nuclides; a new reassessment of spontaneous fission (sf) half-lives for ground state nuclides, distinguishing half-lives from sf decay and cluster decay half-lives and the new cluster-fission decay; charged particle cross sections, (n,p) and (n,{alpha}) measurements for thermal neutrons incident on light nuclides; new thermal (n,{gamma}) cross sections and neutron resonance integrals measured. Details are presented.
Date: August 18, 2002
Creator: HOLDEN,N.E.
Partner: UNT Libraries Government Documents Department

Overview of recent U235 neutron cross section evaluation work

Description: This report is an overview (through 1997) of the U235 neutron cross section evaluation work at Oak Ridge National Laboratory (ORNL), AEA Technology (Harwell) and Lockheed Martin Corp.-Schenectady (LMS), which has influenced, or appeared in, ENDF/B-VI through Release 5. The discussion is restricted to the thermal and resolved resonance regions, apart from some questions about the unresolved region which still need investigation. The important role which benchmark testing has played will be touched on.
Date: October 1, 1998
Creator: Lubitz, C.
Partner: UNT Libraries Government Documents Department

Neutron and nuclear data revised for the 1997/98 handbook of chemistry and physics

Description: The 1997/98 Handbook of Chemistry and Physics will contain revised nuclear data information dealing with scattering and absorption properties of neutrons. All of these nuclear data were recently reevaluated. The 2,200 meter per second neutron cross sections and the neutron resonance integrals evaluation was performed in conjunction with the 1997 KAPL Wall-Chart of the Nuclides to insure consistency in the recommended values in the Handbook and on the Chart. The 2,200 meters per second neutron cross sections presented in the Handbook correspond to room temperature neutrons, 20.43 C, or a thermal neutron energy of 0.0253 electron volts, (eV). Neutron resonance integrals are defined over the energy range from 0.5 eV up to 0.1 {times} 10{sup 6} eV. They are averaged over a flux spectrum with a 1/E shape. Evaluated experimental data are derived from either a direct measurement or from 1/E spectrum averaged resonance parameter information. Resonance integrals are presented for neutron capture, charged particle or neutron fission reactions. Thermal neutron scattering is used for the investigation of the static and dynamic properties of condensed matter and it requires a knowledge of neutron scattering lengths. The Handbook presents bound atom neutron coherent scattering lengths in units of fentometers. Stellar slow neutron capture processes occur in a thermal neutron spectrum with temperatures approximately 30 keV. 30 keV Maxwellian averaged neutron cross sections for astrophysical applications are a new parameter presented in the 78th edition of the Handbook. No new parameters will be added to the Table of Isotopes` nuclear information but revised values will be provided for parameters of all known nuclides of the 112 chemical elements.
Date: July 1, 1997
Creator: Holden, N.E.
Partner: UNT Libraries Government Documents Department

Integral data analysis for resonance parameters determination

Description: Neutron time-of-flight experiments have long been used to determine resonance parameters. Those resonance parameters have then been used in calculations of integral quantities such as Maxwellian averages or resonance integrals, and results of those calculations in turn have been used as a criterion for acceptability of the resonance analysis. However, the calculations were inadequate because covariances on the parameter values were not included in the calculations. In this report an effort to correct for that deficiency is documented: (1) the R-matrix analysis code SAMMY has been modified to include integral quantities of importance, (2) directly within the resonance parameter analysis, and (3) to determine the best fit to both differential (microscopic) and integral (macroscopic) data simultaneously. This modification was implemented because it is expected to have an impact on the intermediate-energy range that is important for criticality safety applications.
Date: September 1, 1997
Creator: Larson, N.M.; Leal, L.C. & Derrien, H.
Partner: UNT Libraries Government Documents Department

A PROGRAM OF RESEARCH AND CALCULATIONS OF RESONANCE ABSORPTION. Final Report

Description: A direct numerical integration of the integral equation for the average collision density in the absorber was previously suggested in a discussion of resonance absorption. The implementation of this program is considered. The method of calculation, comparison with experimental data, and the computer code developed are described. The method of integration, computation of cross sections, selection of mesh size, integration interval, outside correction, the Dancoff correction, and unresolved resonances are discussed. Resonance integrals for U/sup 235/ and Th2/sup >/s3>s/sup 2/ were calculated and compared with experiment. (M.C.G.)
Date: August 28, 1961
Creator: Nordheim, L.W.
Partner: UNT Libraries Government Documents Department

FY2012 summary of tasks completed on PROTEUS-thermal work.

Description: PROTEUS is a suite of the neutronics codes, both old and new, that can be used within the SHARP codes being developed under the NEAMS program. Discussion here is focused on updates and verification and validation activities of the SHARP neutronics code, DeCART, for application to thermal reactor analysis. As part of the development of SHARP tools, the different versions of the DeCART code created for PWR, BWR, and VHTR analysis were integrated. Verification and validation tests for the integrated version were started, and the generation of cross section libraries based on the subgroup method was revisited for the targeted reactor types. The DeCART code has been reorganized in preparation for an efficient integration of the different versions for PWR, BWR, and VHTR analysis. In DeCART, the old-fashioned common blocks and header files have been replaced by advanced memory structures. However, the changing of variable names was minimized in order to limit problems with the code integration. Since the remaining stability problems of DeCART were mostly caused by the CMFD methodology and modules, significant work was performed to determine whether they could be replaced by more stable methods and routines. The cross section library is a key element to obtain accurate solutions. Thus, the procedure for generating cross section libraries was revisited to provide libraries tailored for the targeted reactor types. To improve accuracy in the cross section library, an attempt was made to replace the CENTRM code by the MCNP Monte Carlo code as a tool obtaining reference resonance integrals. The use of the Monte Carlo code allows us to minimize problems or approximations that CENTRM introduces since the accuracy of the subgroup data is limited by that of the reference solutions. The use of MCNP requires an additional set of libraries without resonance cross sections so that reference ...
Date: June 6, 2012
Creator: Lee, C.H. & Smith, M.A. (Nuclear Engineering Division)
Partner: UNT Libraries Government Documents Department

Neutron cross sections for uranium-235 (ENDF/B-IV Release 3)

Description: The resonance parameters in ENDF6 (Release 2) U235 were adjusted to make the average capture and fission cross sections below 900 eV agree with selected differential capture and fission measurements. The measurements chosen were the higher of the credible capture measurements and the lower of the fission results, yielding a higher epithermal alpha. In addition, the 2200 m/s cross sections were adjusted to obtain agreement with the integral value of K1. As a result, criticality calculations for thermal benchmarks, and agreement with a variety of integral parameters, are improved.
Date: September 1, 1996
Creator: Lubitz, C. R.
Partner: UNT Libraries Government Documents Department