Fine structure in the region of symmetric mass distribution for cumulative fission yields

1969 ◽  
Vol 47 (3) ◽  
pp. 275-278 ◽  
Author(s):  
K. S. Thind ◽  
R. H. Tomlinson
Keyword(s):  
Fine Structure ◽  
Yield Curve ◽  
Neutron Emission ◽  
Central Peak ◽  
Mass Region ◽  
Mass Yield ◽  
Neutron Fission ◽  
Energy Neutron ◽  
Cumulative Mass ◽  
Fission Yields

It is predicted that there should be fine structure in the cumulative mass yield curve in the symmetric mass region where major discontinuities in the neutron emission vs. mass curve exist. In the case of low-energy neutron fission of 238U, this fine structure takes the form of a pronounced depression in the region of mass 125. Under similar conditions for 232Th, the fine structure may take the form of depressions in the region of mass 110 and 125 so that the cumulative mass yield curve appears to have a central peak.

THE ABSOLUTE FISSION YIELDS OF TWENTY-EIGHT MASS CHAINS IN THE THERMAL NEUTRON FISSION OF U235

1955 ◽  
Vol 33 (11) ◽  
pp. 693-706 ◽  
Author(s):  
J. A. Petruska ◽  
H. G. Thode ◽  
R. H. Tomlinson
Keyword(s):  
Fine Structure ◽  
Isotope Dilution ◽  
Yield Curve ◽  
Mass Yield ◽  
Absolute Accuracy ◽  
Neutron Fission ◽  
Thermal Neutron Fission ◽  
The Absolute ◽  
Fission Yields ◽  
Better Than

Twenty-eight absolute fission yields totalling 78% of the heavy and 16% of the light fragments have been determined using the mass spectrometer and isotope dilution techniques. The precision of the values obtained is in most cases better than 2% and the absolute accuracy is estimated to be about 3%. Fine structure in the mass–yield curve is discussed in terms of structural preference and various chain branching mechanisms.

CUMULATIVE YIELDS OF LIGHT FRAGMENTS IN U235 THERMAL NEUTRON FISSION

1962 ◽  
Vol 40 (8) ◽  
pp. 1017-1026 ◽  
Author(s):  
H. Farrar ◽  
H. R. Fickel ◽  
R. H. Tomlinson
Keyword(s):  
Thermal Neutron ◽  
Yield Curve ◽  
Mass Spectrometric Study ◽  
Detailed Examination ◽  
Mass Region ◽  
Mass Yield ◽  
Neutron Fission ◽  
Molybdenum Isotopes ◽  
Thermal Neutron Fission ◽  
Fission Yields

A mass spectrometric study of the relative yields of the strontium, yttrium, zirconium, and molybdenum isotopes formed in the thermal neutron fission of U235 has made possible a detailed examination of structure of the light mass region of the mass–yield curve. The relative yields of this work have been normalized to 5.77% for Sr90, and when literature and extrapolated values are taken for the remaining chains, the fission yields total 100.8%.

Cumulative yields of stable and long-lived isotopes of ruthenium and palladium in neutron-induced fission

1978 ◽  
Vol 56 (10) ◽  
pp. 1340-1352 ◽  
Author(s):  
Masako Shima ◽  
H. G. Thode ◽  
R. H. Tomlinson
Keyword(s):  
Thermal Neutron ◽  
Isotope Dilution ◽  
Yield Curve ◽  
Mass Region ◽  
Mass Yield ◽  
Neutron Fission ◽  
Significant Depression ◽  
Thermal Neutron Fission ◽  
Induced Fission ◽  
Fission Yields

The relative cumulative yields of nine stable and long-lived isotopes of ruthenium and palladium (masses 101 to 110) produced in the thermal neutron fission of 233U and in the thermal and epicadmium neutron fission of 235U and 239Pu have been measured using a solid source mass spectrometer and isotope dilution techniques. Absolute yields of these isotopes for the thermal neutron fission of 233U, 235U, and 239Pu are obtained using normalization procedures. These yields provide the first experimentally determined yields of the palladium masses 105, 106, 107, 108, and 110.In the thermal fission of 233U and 235U the ruthenium isotope yields obtained are in general agreement with previously determined values, although discrepancies exist of the order of 10% at masses 103, 104, and 106 for thermal fission of 235U.A plot of the ruthenium and palladium isotope mass yields together with the previously determined yields for the cadmium and tin isotopes indicate a significant depression in the mass yield curve at masses 111 and 114 for 233U and 235U thermal fission, respectively. In the 235U epicadmium fission, yields at even mass numbers are relatively higher than those at odd numbers, resulting in a zigzag yield curve in the 101 to 110 mass region.

THE CUMULATIVE YIELDS OF THE KRYPTON AND XENON ISOTOPES PRODUCED IN THE FAST NEUTRON FISSION OF Th232

1957 ◽  
Vol 35 (8) ◽  
pp. 969-979 ◽  
Author(s):  
T. J. Kennett ◽  
H. G. Thode
Keyword(s):  
Fine Structure ◽  
Fast Neutron ◽  
Isotope Dilution ◽  
Yield Curve ◽  
Mass Yield ◽  
Neutron Fission ◽  
Xenon Isotopes ◽  
Induced Fission ◽  
The Absolute ◽  
Fission Yields

The relative fission yields for mass chains ending in stable krypton and xenon isotopes have been measured for the fast neutron-induced fission of Th232. Isotope dilution techniques were used to determine the krypton/xenon ratio to assist in obtaining the absolute fission yields for these mass chains. The absolute yields were determined by the use of two methods, both giving results which were in excellent agreement. The fine structure observed for the Th232 mass–yield curve is compared with that of heavier fissile nuclides.

THE FISSION YIELDS OF THE STABLE AND LONG-LIVED ISOTOPES OF XENON, CESIUM, AND KRYPTON IN NEUTRON FISSION OF U233

1954 ◽  
Vol 32 (8) ◽  
pp. 522-529 ◽  
Author(s):  
W. Fleming ◽  
R. H. Tomlinson ◽  
H. G. Thode
Keyword(s):  
Fine Structure ◽  
Mass Spectrometer ◽  
Yield Curve ◽  
Closed Shell ◽  
Mass Range ◽  
The Other ◽  
Mass Yield ◽  
Fission Yield ◽  
Neutron Fission ◽  
Fission Yields

The fission yields of Xe131, Xe132, Xe134, Xe136, Cs133, Cs135, Cs137, Kr83, Kr84, 10.27 year Kr85, and Kr86 in the neutron fission of U233 have been determined by mass spectrometer methods. The very pronounced fine structure in the mass yield curve in the mass range 131 to 137 found in U235 fission does not occur in the fission of U233. This disappearance of fine structure would not have been predicted by any of the mechanisms which have been suggested to explain the fine structure in U235 fission. The fission yield of the 10.27 year isomer of Kr85 relative to the other krypton isotopes is considerably higher in U233 fission than in U235 fission, indicating some fine structure in this mass range which may be related to the closed shell of 50 neutrons.

Cumulative yields of stable and long-lived isotopes of tin in neutron-induced fission

1983 ◽  
Vol 61 (11) ◽  
pp. 1490-1497 ◽  
Author(s):  
K. J. R. Rosman ◽  
J. R. De Laeter ◽  
J. W. Boldeman ◽  
H. G. Thode
Keyword(s):  
Stable Isotopes ◽  
Fine Structure ◽  
Fission Product ◽  
Mass Spectrometer ◽  
Smooth Curve ◽  
Mass Region ◽  
Neutron Fission ◽  
Source Mass ◽  
Induced Fission ◽  
Fission Yields

The relative cumulative fission yields of the six stable isotopes of tin (117Sn,118Sn, 119Sn, 120Sn, 122Sn, and 124Sn) and the long-lived isotope 126Sn have been measured in the thermal and epicadium neutron fission of 233U and 235U, and the epicadium neutron fission of 238U. Nanogram-sized fission product tin samples were extracted from irradiated uranium samples and analyzed in a solid source mass spectrometer. In each case a smooth curve can be drawn through the yield points of the seven isotopes of tin. There is, therefore, no evidence of "fine structure" in the 117 ≤ A ≤ 126 portion of the symmetric mass region.

CUMULATIVE YIELDS OF THE HEAVY FRAGMENTS IN THE THERMAL-NEUTRON FISSION OF 241Pu

1964 ◽  
Vol 42 (11) ◽  
pp. 2063-2079 ◽  
Author(s):  
H. Farrar ◽  
W. B. Clarke ◽  
H. G. Thode ◽  
R. H. Tomlinson
Keyword(s):  
Fine Structure ◽  
Thermal Neutron ◽  
Isotope Dilution ◽  
Yield Curve ◽  
Mass Spectrometric ◽  
Mass Yield ◽  
General Shape ◽  
Neutron Fission ◽  
Yield Curves ◽  
Thermal Neutron Fission

The relative yields of isotopes of xenon, cesium, barium, cerium, neodymium, and samarium formed by the thermal neutron fission of 241Pu have been obtained by mass spectrometric methods. The relative yields of the elements were normalized by means of the isotope dilution and isobaric techniques, and absolute cumulative yields were determined by summing the relative yields to 100%. The curve obtained for 241Pu is compared with other mass–yield curves. The general shape of this mass–yield curve is similar to that for 239Pu; yet the fine structure shows greater similarity to that for 235U thermal-neutron fission.

29.—Fine-structure in the Mass-yield Curve for Binary Fission—A Possible Secondary Effect

1974 ◽  
Vol 71 (4) ◽  
pp. 333-336
Author(s):  
N. Feather
Keyword(s):  
Fine Structure ◽  
Short Range ◽  
Mass Number ◽  
Yield Curve ◽  
Neutron Emission ◽  
Secondary Effect ◽  
Mass Yield ◽  
Yield Curves ◽  
Number Range ◽  
Α Particles

SynopsisThe recent suggestion (Feather 1974) that the short-range α-particles of fission are emitted predominantly from post-neutron-emission fragments in the mass-number range 140 to 145 is shown to have implications in relation to the fine-structure of the mass-yield curve. An examination of the mass-yield curves of Unik et al. (1973) discloses, in many of them, a fine-structure feature of the type predicted.

STRUCTURE IN THE MASS–YIELD DISTRIBUTION FOR U235 FISSION

1962 ◽  
Vol 40 (8) ◽  
pp. 943-953 ◽  
Author(s):  
H. Farrar ◽  
R. H. Tomlinson
Keyword(s):  
Fine Structure ◽  
Neutron Yield ◽  
Yield Curve ◽  
Detailed Examination ◽  
Mass Yield ◽  
Neutron Fission ◽  
Fission Fragments ◽  
U235 Fission ◽  
Thermal Neutron Fission ◽  
Mass Yield Distribution

Recent measurements of the cumulative yields of essentially all the mass chains in the thermal neutron fission of U235 have enabled a detailed examination of the fine structure in the mass–yield curve. It has been found that most of the structure results from a slowly changing neutron yield as a function of the mass of the primary fission fragments.

THE FISSION YIELDS OF ISOTOPES OF XENON AND KRYPTON IN THE NEUTRON FISSION OF U236 AND U238

1955 ◽  
Vol 33 (9) ◽  
pp. 541-554 ◽  
Author(s):  
R. K. Wanless ◽  
H. G. Thode
Keyword(s):  
Fine Structure ◽  
Fast Reactor ◽  
Yield Curve ◽  
Percentage Change ◽  
Fission Yield ◽  
Los Alamos ◽  
Neutron Fission ◽  
Isotopic Abundances ◽  
Fission Yields

Several uranium samples have been irradiated under various conditions in the Chalk River N.R.X. reactor and in the Los Alamos fast reactor. The fission gases, xenon and krypton, have been extracted from the irradiated material and the relative isotopic abundances determined mass spectrometrically. Fine structure in the mass – fission yield curve has been found in both the xenon and krypton mass ranges for U235 + n and U238 + n fission. It is observed that this fine structure shifts to lower masses, as predicted, for neutron fission of U238. The proportions of U235 and U238 fission that have occurred in the irradiated samples have been estimated from the percentage change in fine structure.

Sign in / Sign up

Export Citation Format

Share Document