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 22 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Evaluation and Uncertainty Quantification of the Prompt Fission Neutron Spectrum of 239Pu written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 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 Evaluating the 239Pu Prompt Fission Neutron Spectrum Induced by Thermal to 30 MeV Neutrons written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a new evaluation of the 239Pu prompt fission neutron spectrum (PFNS) induced by thermal to 30 MeV neutrons. Compared to the ENDF/B-VII. 1 evaluation, this one includes recently published experimental data as well as an improved and extended model description to predict PFNS. For instance, the pre-equilibrium neutron emission component to the PFNS is considered and the incident energy dependence of model parameters is parametrized more realistically. Experimental and model parameter uncertainties and covariances are estimated in detail. Also, evaluated covariances are provided between all PFNS at different incident neutron energies. In conclusion, selected evaluation results and first benchmark calculations using this evaluation are briefly discussed.

Download or read book Evaluation of the 239Pu Prompt Fission Neutron Spectrum Induced by Neutrons of 500 KeV and Associated Covariances written by and published by . This book was released on 2015 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present evaluations of the prompt fission neutron spectrum (PFNS) of 239Pu induced by 500 keV neutrons, and associated covariances. In a previous evaluation by Talou et al. 2010, surprisingly low evaluated uncertainties were obtained, partly due to simplifying assumptions in the quantification of uncertainties from experiment and model. Therefore, special emphasis is placed here on a thorough uncertainty quantification of experimental data and of the Los Alamos model predicted values entering the evaluation. In addition, the Los Alamos model was extended and an evaluation technique was employed that takes into account the qualitative differences between normalized model predicted values and experimental shape data. These improvements lead to changes in the evaluated PFNS and overall larger evaluated uncertainties than in the previous work. However, these evaluated uncertainties are still smaller than those obtained in a statistical analysis using experimental information only, due to strong model correlations. Hence, suggestions to estimate model defect uncertainties are presented, which lead to more reasonable evaluated uncertainties. The calculated keff of selected criticality benchmarks obtained with these new evaluations agree with each other within their uncertainties despite the different approaches to estimate model defect uncertainties. The keff one standard deviations overlap with some of those obtained using ENDF/B-VII. 1, albeit their mean values are further away from unity. Spectral indexes for the Jezebel critical assembly calculated with the newly evaluated PFNS agree with the experimental data for selected (n, [gamma]) and (n, f) reactions, and show improvements for high-energy threshold (n,2n) reactions compared to ENDF/B-VII. 1.

Download or read book Ratio of Capture to Fission in Pu 239 at Kev Neutron Energies written by and published by . This book was released on 1967 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nuclear Data and Measurements Series written by and published by . This book was released on 1986 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The prompt-fission-neutron spectrum resulting from 239Pu fission induced by 0.55 MeV incident neutrons is measured from 1.0 to 10.0 MeV relative to that of 235U fission induced by the same incident-energy neutrons. The measurements employ the time-of-flight technique. Energy-dependent ratios of the two spectra are deduced from the measured values over the energy range 1.0 to 10.0 MeV. The experimentally-derived ratio results are compared with those calculated from ENDF/B-V, revision-2, and with results of recent microscopic measurements. Using the ENDF/B-V 235U Watt parameters for the 235U spectrum, the experimental measurements imply a ratio of average fission-spectrum energies of 239Pu/235U = 1.045 +- 0.003, compared to the value 1.046 calculated from ENDF/B-V, revision 2. 12 refs., 2 figs., 2 tabs.

Download or read book Prompt fission neutron Spectra of 233U 235U 239Pu and 24 Pu Relative to that of 252Cf 550 and 850 KeV written by and published by . This book was released on 1979 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The prompt-neutron-induced-fission spectra of 233U, 235U, 239Pu, and 24°Pu are measured relative to the prompt-spontaneous-fission-neutron spectrum of 252Cf. The fission of 233U, 235U, and 239Pu is induced by approx. = 550-keV neutrons, and that of 24°Pu, by approx. = 850-keV neutrons. The emitted fission neutrons are observed over the energy range less than or equal to 0.5 to 10.0 MeV by use of time-of-flight techniques. Analysis of the measured values indicates that the average-fission-neutron energies are -123 +- 30 (233U), -157 +- 24 (235U), -76 +- 29 (239Pu), and -46 +- 29 (24°Pu) keV relative to the energy for 252Cf. The experimental results are compared with those of ENDF/B-V, and a simple behavior of average-prompt-fission-neutron energies is suggested.

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 The Need for Precise and Well documented Experimental Data on Prompt Fission Neutron Spectra from Neutron induced Fission of 239Pu written by and published by . This book was released on 2016 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: The spectrum of neutrons emitted promptly after 239Pu(n, f)--a so-called prompt fission neutron spectrum (PFNS)--is a quantity of high interest, for instance, for reactor physics and global security. However, there are only few experimental data sets available that are suitable for evaluations. In addition, some of those data sets differ by more than their 1-[sigma] uncertainty boundaries. We present the results of MCNP studies indicating that these differences are partly caused by underestimated multiple scattering contributions, over-corrected background, and inconsistent deconvolution methods. A detailed uncertainty quantification for suitable experimental data was undertaken including these effects, and test-evaluations were performed with the improved uncertainty information. The test-evaluations illustrate that the inadequately estimated effects and detailed uncertainty quantification have an impact on the evaluated PFNS and associated uncertainties as well as the neutron multiplicity of selected critical assemblies. A summary of data and documentation needs to improve the quality of the experimental database is provided based on the results of simulations and test-evaluations. Furthermore, given the possibly substantial distortion of the PFNS by multiple scattering and background effects, special care should be taken to reduce these effects in future measurements, e.g., by measuring the 239Pu PFNS as a ratio to either the 235U or 252Cf PFNS.

Download or read book Recent Improvements in the Calculation of Prompt Fission Neutron Spectra written by and published by . This book was released on 1988 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Three tropics have been considered in the refinement and improvement of our original calculations of prompt fission neutron spectra. These are an improved calculation of the prompt fission neutron spectrum N(E) from the spontaneous fission of 252Cf, a complete calculation of the prompt fission neutron spectrum matrix N(E, E/sub n/) from the neutron-induced fission of 235U, at incident neutron energies ranging from 0 to 15 MeV, and an assessment of the scission neutron component of the prompt fission neutron spectrum. Preliminary results will be presented and compared with experimental measurements and an evaluation. A suggestion has been made for new integral cross-section measurements.

Download or read book Prompt fission Neutron Spectra of 233U 235U 239Pu and 240Pu Relative to that of 252Cf written by A. Smith and published by . This book was released on 1979 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Prompt Fission Neutron Spectrum written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: After a brief introduction concerning nuclear data, prompt fission neutron spectrum (PFNS) evaluations and the limited PFNS covariance data in the ENDF/B-VII library, and the important fact that cross section uncertainties ~ PFNS uncertainties, the author presents background information on the PFNS (experimental data, theoretical models, data evaluation, uncertainty quantification) and discusses the impact on certain well-known critical assemblies with regard to integral quantities, sensitivity analysis, and uncertainty propagation. He sketches recent and ongoing research and concludes with some final thoughts.

Download or read book Prompt Fission Neutron Spectra and Anti Nu P written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Methods used to obtain the evaluated prompt fisson neutron spectrum N(E) and the average prompt neutron multiplicity anti .nu./sub p/ are reviewed. The relative influence of experimental data; interpolated, extrapolated, and fitted experimental data; systematics; and nuclear theory are considered for the cases where (a) abundant experimental data exist, (b) some experimental data exist, and (c) no experimental data exist. The Maxwellian and Watt distributions, and the determination of the parameters of these distributions by data fitting, are described and compared to recent new theoretical work on the calculation of N(E). Similarly, various expressions for anti .gamma./sub p/ that have been obtained by data fitting and systematics are described and compared to recent new theoretical work. Complications in the evaluation of N(E) and anti .gamma./sub p/ due to the onset of multiple-chance fission and the interrelationships between N(E), anti .gamma delta./sub p/ and the multiple-chance fission cross section are discussed using the example of the fission of 235U. Some statistics and comments are given on the evaluations of N(E) and anti .gamma./sub p/ contained in ENDF/B-V, and a number of concluding recommendations are made for future evaluation work.

Download or read book ERDA Energy Research Abstracts written by United States. Energy Research and Development Administration and published by . This book was released on 1977 with total page 646 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book ERDA Energy Research Abstracts written by United States. Energy Research and Development Administration. Technical Information Center and published by . This book was released on 1977 with total page 1682 pages. Available in PDF, EPUB and Kindle. Book excerpt: