Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
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.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
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.
Author: Publisher: ISBN: Category : Languages : en Pages : 134
Book Description
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.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
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).
![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]. PDF](https://books.google.com/books/content/images/frontcover/xDy2AQAACAAJ?fife=w80-h100)
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Author: Raymond Waldo
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Author: George Robert Keepin
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Author: R. E. Skinner
Author: Michaele Clarice Brady
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