This document is the latest in a series of compilations of fission yield data Fission yield measurements reported in the open literature and calculated charge distributions have been used to produce a recommended set of yields for the fission products The original data with reference sources, and the recommended yields axe presented in tabular form These include many nuclides which fission by neutrons at several energies These energies include thermal energies (T), fission spectrum energies (F), 14 meV High Energy (H or HE), and spontaneous fission (S), in six sets of ten each Set A includes U235T, U235F, U235HE, U238F, U238HE, Pu239T, Pu239F, Pu241T, U233T, Th232F Set B includes U233F, U233HE, U236F, Pu239H, Pu240F, Pu241F, Pu242F, Th232H, Np237F, Cf252S Set C includes U234F, U237F, Pu240H, U234HE, U236HE, Pu238F, Am241F, Am243F, Np238F, Cm242F Set D includes Th227T, Th229T, Pa231F, Am241T, Am241H, Am242MT, Cm245T, Cf249T, Cf251T, Es254T Set E includes Cf250S, Cm244S, Cm248S, Es253S, Fm254S, Fm255T, Fm256S, Np237H, U232T, U238S Set F includes Cm243T, Cm246S, Cm243F, Cm244F, Cm246F, Cm248F, Pu242H, Np237T, Pu240T, and Pu242T to complete fission product yield evaluations for 60 fissioning systems in all This report also serves as the primary documentation for the second evaluation of yields in ENDF/B-VImore » released in 1993« less

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Evaluation and compilation of fission product yields 1993

Survey of short-lived fission products obtained using the isotope-separator-on-line facility at Studsvik

The absolute fission yields of 46 fission products in 238U (99.9997 at.%), 46 fission products in 237Np, 27 fission products in 238Pu (99.21 at.%), 30 fission products in 240Pu (99.48 at.%), 30 fis...

Measurement of absolute fission yields in the fast neutron-induced fission of actinides : 238U, 237Np, 238Pu, 240Pu, 243Am, and 244Cm by track-etch-cum-gamma spectrometry

Nuclear Data Sheets for A=77

Mass yield curves in low-energy proton-induced fissions of $^{233}\mathrm{U}$, $^{235}\mathrm{U}$, $^{238}\mathrm{U}$, $^{237}\mathrm{Np}$, $^{239}\mathrm{Pu}$, $^{242}\mathrm{Pu}$, $^{244}\mathrm{Pu}$, $^{241}\mathrm{Am}$, and $^{243}\mathrm{Am}$ were measured. The full widths at half maximum (FWHM) of the heavier asymmetric peak of the mass yield curves showed a sudden dip in the region of ${A}_{f}$=240--245. The correlation between the P/V ratio and the FWHM of the asymmetric mass yield peak was obtained as a function of proton energy. The FWHM values were independent of the incident proton energy as long as the P/V ratio was larger than 10 for all the fissioning systems studied. The excitation energy dependence of the mass yield curves was investigated. It was found that the excitation energy dependence of symmetrically divided fission products was apparently different from that of asymmetrically divided ones. With a simple assumption of the two-mode hypothesis, the observed mass yield curves could be decomposed into two mass yield curves. Asymmetric mass yield peaks could be best represented by the sum of two Gaussians, and their variation could be expressed by the variation of Gaussian parameters. The peak positions of the two Gaussians were always A=133--135 and A=140--142 for all the investigated fissioning nuclides. The preference of those fragment masses is discussed in terms of both the scission-point model and the saddle-point model.

Systematic analysis of mass yield curves in low-energy fission of actinides.

Mass yields of 241Am thermal-neutron fission

Decay of 77mGe

Ranges of fission fragments produced by thermal neutron fission of 241Am

Kinetic energies and most-probable charges in fission were calculated for 235 U+n, 252 Cf and 226 Ra+p by applying the statistical model by Fong. The mass formula by Myers and Swiatecki was employed to evaluate fragment deformation energies. The most-probable scission configuration for a given mass division was obtained by maximizing the effective intrinsic excitation energy of the complementary fragments which was given as a function of their charges and deformation parameters. The general trends of the kinetic energy distribution and the charge distribution in fission could be reproduced fairly well.

Calculation of Kinetic Energy and Most-Probable Charge in Fission

Calculation of fission fragment distributions based on Fong's statistical theory was carried out for the case of 241 Am thermal neutron fission using Myers and Swiatecki's mass formula and a phenomenological level density formula, originally developed by Gilbert and extended for deformed nuclei by the present authors. The results show that Fong's statistical theory with the now attainable knowledge on mass and level density, can only account for narrow asymmetric mass peaks centred around A ≃108 and 134. The present results are in good agreement with those calculated by Ignatyuk with a microscopic approach. Other physical quantities associated with fission reaction, such as, kinetic energy distribution, charge distribution and total excitation energy distribution at scission configuration are given. Comparison was also made among various approaches for level density formulation.

Hiromichi Nakahara

Papers

Mass yields of 241Am thermal-neutron fission

Decay of 77mGe

Ranges of fission fragments produced by thermal neutron fission of 241Am

Calculation of Kinetic Energy and Most-Probable Charge in Fission

Statistical Calculation of Fission