Download or read book Study of Calculated and Measured Time Dependent Delayed Neutron Yields TX for Calculating Delayed Neutron Yields MATINV for Matrix Inversion in FORTRAN for LSI II Minicomputer written by and published by . This book was released on 1980 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Time-dependent delayed neutron emission is of interest in reactor design, reactor dynamics, and nuclear physics studies. The delayed neutrons from neutron-induced fission of 232U, 237Np, 238Pu, 241Am, /sup 242m/Am, 245Cm, and 249Cf were studied for the first time. The delayed neutron emission from 232Th, 233U, 235U, 238U, 239Pu, 241Pu, and 242Pu were measured as well. The data were used to develop an empirical expression for the total delayed neutron yield. The expression gives accurate results for a large variety of nuclides from 232Th to 252Cf. The data measuring the decay of delayed neutrons with time were used to derive another empirical expression predicting the delayed neutron emission with time. It was found that nuclides with similar mass-to-charge ratios have similar decay patterns. Thus the relative decay pattern of one nuclide can be established by any measured nuclide with a similar mass-to-charge ratio. A simple fission product yield model was developed and applied to delayed neutron precursors. It accurately predicts observed yield and decay characteristics. In conclusion, it is possible to not only estimate the total delayed neutron yield for a given nuclide but the time-dependent nature of the delayed neutrons as well. Reactors utilizing recycled fuel or burning actinides are likely to have inventories of fissioning nuclides that have not been studied until now. The delayed neutrons from these nuclides can now be incorporated so that their influence on the stability and control of reactors can be delineated. 8 figures, 39 tables.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1980 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Study of Calculated and Measured Time Dependent Delayed Neutron Yields written by Raymond Waldo and published by . This book was released on 1980 with total page 330 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book INIS Atomindex written by and published by . This book was released on 1980 with total page 1692 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Delayed Neutron Calculations Using ENDF written by and published by . This book was released on 1979 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Data from 20 fission yield sets in ENDF/B-V are used with the emission probabilities (Pn) of 105 delayed neutron precursors to calculate 6-group and total equilibrium delayed neutron yields of (anti .nu./sub d/). Results are compared with recent evaluations and selected measurements of anti .nu./sub d/. Least-squares data adjustment methods are in progress to improve agreement; preliminary results indicate significant improvement when fission yields are adjusted. 2 tables.
Download or read book Delayed Neutrons from Fissionable Isotopes of Uranium Plutonium and Thorium written by George Robert Keepin and published by . This book was released on 1957 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurements of Delayed Neutron Parameters for U 235 and Np 237 written by and published by . This book was released on 1997 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: Delayed neutrons are emitted by excited nuclei formed in beta decay of fission products called delayed neutron precursors. About 1% of the total neutrons released in fission are delayed neutrons; however, this small fraction plays an important role in nuclear reactor control. The delayed neutrons determine the time-dependent behavior of reactors, and knowledge of parameters used to predict neutron emission rate is essential for establishing reactivity worths. The delayed neutron yields, decay constants, and the absolute yield for the six-group delayed neutrons have been measured for U-235 and Np-237. This experiment has been called for in the forecast of experiments needed to support operations in the US. The bare U-235 metal assembly Godiva IV at the Los Alamos Critical Experiment Facility (LACEF) provided the source of neutrons. Godiva IV generated about 107 total fissions in the samples for the infinite and instantaneous irradiation needed to accentuate the shorter and longer-lived groups of delayed neutrons. The detection system used in the experiment consisted of 20 He-3 tubes embedded in a polyethylene cylinder. The delayed neutron activity resulting from the fast neutron-induced fission has been measured. The measured absolute yield for U-235 was determined to be 0.0163 " 0.009 neutrons/fission. This value compares very well with the well-established Keepin absolute yield of 0.0165 " 0.0005. The newly measured absolute yield value for Np-237 was 0.0126 " 0.0007, which compares well to the recently reported value of 0.0129 " 0.0004 by Saleh and Parish. The measured values for U-235 are corroborated with period (e-folding time) versus reactivity calculations.
Download or read book Evaluation and Application of Delayed Neutron Precursor Data written by Michaele Clarice Brady and published by . This book was released on 1988 with total page 564 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Delayed Neutron Data written by and published by . This book was released on 1974 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: BS>The status of delayed neutron measurements is reviewed. Emphasis is placed on the absolute yield va the energy of the neutrons cauging fission, group yields and periods, and in the delayed neutron spectra. Systematics are discussed; and an evaluated data set, based both on available measurements and on systematics arguments, is suggested for inclusion in ENDF/B-IV. Areas of delayed neutron studies which require additional measurements are outlined. (18 figures, 18 tables) (auth).
Download or read book Validation of Aggregate Delayed Neutron Spectra Calculated from Precursor Data written by and published by . This book was released on 1989 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: An extensive reference library of delayed neutron data has been compiled which contains fission yields and branchings, delayed neutron emission probabilities, and spectra for 271 precursors. These data have been used to calculate the aggregate behavior of delayed neutrons following a fission event in 43 fissioning systems. Least-squares techniques were used to produce fitted decay constants and abundances in the conventional six-group formalism from these calculated activity curves. A consistent set of six-group spectra have also been calculated for each of the fissioning systems. Recent measurements at the University of Lowell have produced measured energy spectra for delayed neutrons following the thermal fission (T) of 235U and 239Pu, and the fast fission (F) of 238U. These measured spectra provide data that may be used to validate the precursor data base and the fitted six-group data. This summary presents results of this validation effort. Both the individual precursor data and the six-group data have been used to calculate aggregate equilibrium spectra for 235U(T), 238U(F), and 239Pu(T) via summation techniques. The important precursors in each case are identified, and the status of their data reviewed. 8 refs., 3 figs., 3 tabs.
Download or read book Uncertainty Evaluation of Delayed Neutron Decay Parameters written by Jinkai Wang and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In a nuclear reactor, delayed neutrons play a critical role in sustaining a controllable chain reaction. Delayed neutron's relative yields and decay constants are very important for modeling reactivity control and have been studied for decades. Researchers have tried different experimental and numerical methods to assess these delayed neutron parameters. The reported parameter values vary widely, much more than the small statistical errors reported with these parameters. Interestingly, the reported parameters fit their individual measurement data well in spite of these differences. This dissertation focuses on evaluation of the errors and methods of delayed neutron relative yields and decay constants for thermal fission of U-235. Various numerical methods used to extract the delayed neutron parameter from the measured data, including Matrix Inverse, Levenberg-Marquardt, and Quasi-Newton methods, were studied extensively using simulated delayed neutron data. This simulated data was Poisson distributed around Keepin's theoretical data. The extraction methods produced totally different results for the same data set, and some of the above numerical methods could not even find solutions for some data sets. Further investigation found that ill-conditioned matrices in the objective function were the reason for the inconsistent results. To find a reasonable solution with small variation, a regularization parameter was introduced using a numerical method called Ridge Regression. The results from the Ridge Regression method, in terms of goodness of fit to the data, were good and often better than the other methods. Due to the introduction of a regularization number in the algorithm, the fitted result contains a small additional bias, but this method can guarantee convergence no matter how large the coefficient matrix condition number. Both saturation and pulse modes were simulated to focus on different groups. Some of the factors that affect the solution stability were investigated including initial count rate, sample flight time, initial guess values. Finally, because comparing reported delayed neutron parameters among different experiments is useless to determine if their data actually differs, methods are proposed that can be used to compare the delayed neutron data sets.
Download or read book Measurements of Delayed Neutron Yields from Thermal Neutron Induced Fission of 235U 233U 239Pu and 237Np written by S. B. Borzakov and published by . This book was released on 1998 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Comparison of Observed Delayed neutron Abundances with Calculated Fission Yields of Neutron Precursors written by P. Patzelt and published by . This book was released on 1967 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Analytical Applications for Delayed Neutrons written by and published by . This book was released on 1983 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Analytical formulations that describe the time dependence of neutron populations in nuclear materials contain delayed-neutron dependent terms. These terms are important because the delayed neutrons, even though their yields in fission are small, permit control of the fission chain reaction process. Analytical applications that use delayed neutrons range from simple problems that can be solved with the point reactor kinetics equations to complex problems that can only be solved with large codes that couple fluid calculations with the neutron dynamics. Reactor safety codes, such as SIMMER, model transients of the entire reactor core using coupled space-time neutronics and comprehensive thermal-fluid dynamics. Nondestructive delayed-neutron assay instruments are designed and modeled using a three-dimensional continuous-energy Monte Carlo code. Calculations on high-burnup spent fuels and other materials that contain a mix of uranium and plutonium isotopes require accurate and complete information on the delayed-neutron periods, yields, and energy spectra. A continuing need exists for delayed-neutron parameters for all the fissioning isotopes.
Download or read book Grande exposition de photographies l occasion du 800 me anniversaire de Tramelan written by and published by . This book was released on 1978 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Delayed Neutron Spectra Decay Group for Fissioning Systems from 227Th Through 255Fm written by and published by . This book was released on 1988 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Most applications of delayed neutrons use an approximate temporal group representation of measured aggregate data. Such data have been limited to the few fissioning nuclides that have aggregate measurements, and even these have inadequate or no spectral measurements. Improvements in the experimental techniques of isotope separation and neutron spectroscopy have made the study of delayed neutron emission from individual precursor nuclides more practical and productive over the past fifteen or so years. The quantity and quality of the delayed neutron emission probabilities and particularly the neutron emission spectra for the individual nuclides have been greatly improved. This paper will briefly review a recently completed evaluation of precursor data that comprises the largest single set of such data to date, and will also describe how the precursor data has been used to produced delayed neutron yields, halflives, and spectra in the classical six-group representation for 43 fissioning systems from 227Th to 225Fm. Comments and observations made concerning the use of more than six time groups will also be included. The application of the data in both its explicit and reduced (six temporal group representation) forms in the point reactor kinetics equations will also be discussed. Results from beta-effective calculations in a simple Godiva-type system will be presented, but the paper will concentrate on the data base and its few-group representations. 17 refs., 1 fig., 1 tab.
Download or read book Obdachlosigkeit written by and published by . This book was released on 1971 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt:
