RECENT FISSION PROCESS STUDIES WITH MONO-ENERGETIC NEUTRONS (TRIPARTITE CONFERENCE ON NUCLEAR CONSTANTS--JANUARY 10-12, 1956)
The fission cross sections of U/sup 235/, U/sup 234/, U/sup 236/, and U/ sup 238 were measured in terms of the U/sup 235/ cross section from a few kev, or the effective threshold, to 4 Mev. Monoenergetic neutrons were from the V(p,n), Li(p.n), and T(p,n) reactions produced by protons accelerated by electrostatic generators. The published cross sections of U/sup 234/ and U/sup 236/ are compared with the cross section of U/sup 235/. The results for U/sup 233/ differ somewhat from values reported in the literature. The absorption cross sections of U/sup 235/ and Fu/sup 239/ were measured at six energies in the 5 to 50 kev energy range. Neutrons from the reaction V/sup 51/(p,n)Cr/sup 51/ were used in spherical shell transmission measurements. The results show, in general, a decrease in absorption cross section with increasing energy up to about 30 kev and then a nearly constant value (up to 50 bev) of about 2.8 b for U/sup 235/ and 2.2 b for Pu/sup 239/. The variation of nu for U/sup 235/ with incident neutron energy was studied for the energy range 0 to 5 Mev. Neutrons were produced by the T(p,n) and the D(d,n) reactions. Fission neutrons were detected with a shielded recoil counter in coincidence with fission fragment pulses from an annular fission chamber placed around the recoil counter. The measurements were calibrated in terms of thermal nu by performing the experiment with essentially thermal neutrons. The results show an increase of nu of about 30% at 5 Mev. This is in fair agreement with the original prediction of this effect which was based on a phenomenological theory of evaporation of neutrons from the excited fission fragments. (auth)
- Research Organization:
- Oak Ridge National Lab., Tenn.
- DOE Contract Number:
- W-7405-ENG-26
- NSA Number:
- NSA-12-000965
- OSTI ID:
- 4329861
- Report Number(s):
- CF-56-2-106
- Resource Relation:
- Other Information: Decl. Apr. 11, 1957. Orig. Receipt Date: 31-DEC-58
- Country of Publication:
- United States
- Language:
- English
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ABSORPTION- COMMUNICATIONS- CROSS SECTIONS- ENERGY- ENERGY RANGE- INTERACTIONS- KEV RANGE- MACHINE PARTS- MEASURED VALUES- NEUTRONS- PLUTONIUM 239- SPHERES- TRANSDUCERS- URANIUM 235- VARIATIONS
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