Download or read book Energy Measurement of Prompt Fission Neutrons in 239Pu n F for Incident Neutron Energies from 1 to 200 MeV written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental campaign was started in 2002 in the framework of a collaboration belween CEA-DAM and the Los Alamos National Laboratory to measure the prompt fission neutron spectra (PFNS) for incident neutron energies from 1 to 200 MeV with consistent error uncertainties over the whole energy range. The prompt neutron spectra in {sup 235,238}U(n, f) and 237Np(n, f) have been already studied successfully. A first attempt to characterize the prompt neutrons emitted during the fission of the 239Pu was done in 2007. This contribution will focus on the results obtained during the final experiment to measure the PFNS in 239Pu(n, f) performed in 2008. Prompt fission neutron spectra in the neutron-induced fission of 239Pu have been measured for incident neutron energies from 1 to 200 MeV at the Los Alamos Neutron Science Center. Mean energies obtained from the spectra are discussed and compared to theoretical model calculation.
Download or read book Event by Event Study of Prompt Neutrons from 239Pu written by and published by . This book was released on 2010 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: Employing a recently developed Monte Carlo model, we study the fission of 24°Pu induced by neutrons with energies from thermal to just below the threshold for second chance fission. Current measurements of the mean number of prompt neutrons emitted in fission, together with less accurate measurements of the neutron energy spectra, place remarkably fine constraints on predictions of microscopic calculations. In particular, the total excitation energy of the nascent fragments must be specified to within 1 MeV to avoid disagreement with measurements of the mean neutron multiplicity. The combination of the Monte Carlo fission model with a statistical likelihood analysis also presents a powerful tool for the evaluation of fission neutron data. Of particular importance is the fission spectrum, which plays a key role in determining reactor criticality. We show that our approach can be used to develop an estimate of the fission spectrum with uncertainties several times smaller than current experimental uncertainties for outgoing neutron energies of less than 2 MeV.
Download or read book Measurements of the Average Number of Prompt Neutrons Emitted Per Fission of 239Pu and 235U 0 005 EV to 10 MeV written by and published by . This book was released on 1978 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Measurements of the average number of prompt neutrons .nu. bar/sub p/(E) emitted in neutron-induced fission of 235U and 239Pu relative to .nu. bar/sub p/ for spontaneous fission of 252Cf were made over an incident neutron energy range from 0.005 eV to 10 MeV. The incident neutrons were generated in pulses at the Oak Ridge Electron Linear Accelerator, and their energies, defined by time-of-flight methods. The samples were contained in fission chambers located in a large liquid scintillator. Fissions in the samples were identified by the simultaneous detection of prompt fission gamma rays in the scintillator and a pulse from the fission chamber. Fission neutrons were identified by the detection of the prompt gamma-ray cascade resulting from neutron absorption in gadolinium loaded in the liquid scintillator. The value of .nu. bar/sub p/(E) for 239Pu at 0.0253 eV agrees with the value given in EDNF/B-IV, whereas the corresponding value for 235U is about 0.7% larger than that given in ENDF/B-IV. 4 figures, 4 tables.
Download or read book Event by event Evaluation of the Prompt Fission Neutron Spectrum from 239Pu n F written by and published by . This book was released on 2011 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have developed an improved evaluation method for the spectrum of neutrons emitted in fission of 239Pu induced by incident neutrons with energies up to 20 MeV. The v covariance data, including incident energy correlations introduced by the v evaluation method, were used to fix the input parameters in our event-by-event model of fission, FREYA, by applying formal statistical methods. Formal estimates of uncertainties in the evaluation were developed by randomly sampling model inputs and calculating likelihood functions based on agreement with the evaluated v. Our approach is able to employ a greater variety of fission measurements than the relatively coarse spectral data alone. It also allows the study of numerous fission observables for more accurate model validation. The combination of an event-by-event Monte Carlo fission model with a statistical-likelihood analysis is thus a powerful tool for evaluation of fission-neutron data. Our empirical model FREYA follows the complete fission event from birth of the excited fragments through their decay via neutron emission until the fragment excitation energy is below the neutron separation energy when neutron emission can no longer occur. The most recent version of FREYA incorporates pre-equilibrium neutron emission, the emission of the first neutron before equilibrium is reached in the compound nucleus, and multi-chance fission, neutron evaporation prior to fission when the incident neutron energy is above the neutron separation energy. Energy, momentum, charge and mass number are conserved throughout the fission process. The best available values of fragment masses and total kinetic energies are used as inputs to FREYA. We fit three parameters that are not well under control from previous measurements: the shift in the total fragment kinetic energy; the energy scale of the asymptotic level density parameter, controlling the fragment 'temperature' for neutron evaporation; and the relative excitation of the light and heavy fragments, governing the number and energy of neutrons emitted from each fragment. The latter two parameters are assumed to be independent of the incident neutron energy while the first varies with incident energy. We describe our method and the subsequent spectral evaluation and present the results of several standard validation calculations that test our new evaluation. These benchmarks include critical assemblies, sensitive to criticality in fast systems; pulsed sphere measurements testing the spectra at incident neutron energies of 14 MeV; and other tests.
Download or read book Event by event Study of Prompt Neutrons from 239Pu n F written by and published by . This book was released on 2009 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: Employing a recently developed Monte-Carlo model, we study the fission of 24°Pu induced by neutrons with energies from thermal to just below the threshold for second chance fission. Current measurements of the mean number of prompt neutrons emitted in fission, together with less accurate measurements of the neutron energy spectra, place remarkably fine constraints on predictions of microscopic calculations. In particular, the total excitation energy of the nascent fragments must be specified to within 1MeV to avoid disagreement with measurements of the mean neutron multiplicity. The combination of the Monte-Carlo fission model with a statistical likelihood analysis also presents a powerful tool for the evaluation of fission neutron data. Of particular importance is the fission spectrum, which plays a key role in determining reactor criticality. We show that our approach can be used to develop an estimate of the fission spectrum with uncertainties several times smaller than current experimental uncertainties for outgoing neutron energies of less than 2 MeV.
Download or read book Nuclear Fission written by Patrick Talou and published by Springer Nature. This book was released on 2023-01-01 with total page 487 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides advanced students and postdocs, as well as current practitioners of any field of nuclear physics involving fission an understanding of the nuclear fission process. Key topics covered are: fission cross sections, fission fragment yields, neutron and gamma emission from fission and key nuclear technologies and applications where fission plays an important role. It addresses both fundamental aspects of the fission process and fission-based technologies including combining quantitative and microscopic modeling.
Download or read book Fission Neutrons written by Nikolay Kornilov and published by Springer. This book was released on 2014-07-25 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt: Although the fission of heavy nuclei was discovered over 75 years ago, many problems and questions still remain to be addressed and answered. The reader will be presented with an old, but persistent problem of this field: The contradiction between Prompt Fission Neutron (PFN) spectra measured with differential (microscopic) experiments and integral (macroscopic and benchmark) experiments (the Micro-Macro problem). The difference in average energy is rather small ~3% but it is stable and we cannot explain the difference due to experimental uncertainties. Can we measure the PFN spectrum with high accuracy? How may we compare results of different experiments to provide better accuracy? Are our traditional theoretical models correct? What can be done to solve the Micro-Macro problem in future? These questions are discussed in this monograph for the reader. The current work will be of interest to graduate students and researchers, particularly those working in nuclear and neutron physics.
Download or read book The Two plate Method of Measuring Fast Neutron Energy Spectra when the Direction of the Incident Neutrons Cannot be Determined written by John E. Evans and published by . This book was released on 1952 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurement of Neutron Flux and Spectra for Physical and Biological Applications written by National Committee on Radiation Protection and Measurements (U.S.) and published by . This book was released on 1960 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Summary of Neutron Measurement Methods written by Herman Lunden Miller and published by . This book was released on 1962 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1976 with total page 612 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurement of the Average Multiplicity Prompt fission neutrons from 238 u n F and 235 u n F from 0 7 to 200 MeV written by and published by . This book was released on 2004 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Prompt-fission-neutron multiplicities were measured at a 'white' neutron source for the fission of 238U and 235U up to 200 MeV. The data are of great importance in the connection of accelerator-coupled nuclear reactor systems incinerating actinides, with uranium considered as a prototype actinide. We report that the fission induced by 200 MeV neutrons produces (almost equal to)10 more prompt neutrons than the fission induced by reactor neutrons. In conclusion, new data on {bar {nu}}{sub p} are reported with errors {
Download or read book The Effect of Prompt Neutrons on the Direction and Time of Flight of Fission Fragments written by R. W. Lide and published by . This book was released on 1962 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurement of Neutron Flux and Spectra for Physical and Biological Applications written by National Committee on Radiation Protection and Measurements (U.S.) and published by . This book was released on 1960 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurement of the Average Number of Prompt Neutrons Emitted Per Fission of sup 233 U Relative to sup 252 Cf for the Energy Region 500 EV to 10 MeV and Below 0 3 EV written by and published by . This book was released on 1981 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The energy dependence of the average number of prompt fission neutrons emitted per fission, anti .nu./sub p/(E), has been measured for /sup 233/U relative to anti .nu./sub p/ for /sup 252/Cf over the neutron energy ranges 500 eV to 10 MeV and below 0.3 eV. A large Gd-loaded liquid scintillator was used to detect neutrons and the samples of /sup 233/U and /sup 252/Cf were contained in fission chambers. The present results for anti .nu./sub p/(E) for /sup 233/U are in accord with the experimental results of Boldeman and the evaluated results of Lemmel in the thermal energy range, but in the neutron energy region between 100 keV and 1 MeV the present data are 1% or more larger than other experimental values.
Download or read book Measurement of the Average Number of Prompt Neutrons Emitted Per Fission of 235U Relative to 252Cf for the Energy Region 500 EV to 10 MeV written by and published by . This book was released on 1980 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The average number of prompt neutrons emitted per fission .nu./sub p/-bar(E), was measured for 235U relative to .nu./sub p/-bar for the spontaneous fission of 252Cf over the neutron energy range from 500 eV to 10 MeV. The samples of 235U and 252Cf were contained in fission chambers located in the center of a large liquid scintillator. Fission neutrons were detected by the large liquid scintillator. The present values of .nu./sub p/-bar(E) for 235U are about 0.8% larger than those measured by Boldeman. In earlier work with the present system, it was noted that Boldeman's value of .nu./sub p/-bar(E) for thermal energy neutrons was about 0.8% lower than obtained at ORELA. It is suggested that the thickness of the fission foil used in Boldeman's experiment may cause some of the discrepancy between his and the present values of .nu./sub p/-bar(E). For the energy region up to 700 keV, the present values of .nu./sub p/-bar(E) for 235U agree, within the uncertainty, with those given in ENDF/B-V. Above 1 MeV the present results for .nu./sub p/-bar(E) range about the ENDF/B-V values with differences up to 1.3%. 6 figures, 1 table.
Download or read book Energies of the Delayed Neutrons from U235 Fission Products written by and published by . This book was released on 1946 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt:
