CALCULATIONS OF NEUTRON AGE IN H$sub 2$O AND OTHER MATERIALS
The Chronos Code and the Corn Pone Code, were used to calculate neutron slowing-down and flux ages, respectively, of fission and monoenergetic sources in HiO, D20, 0, H, Be, BeO, C, oil, and diphenyl. The calculations for H20 and D20 were the most extensive and included investigations of the effects of isotropic versus anisotropic scattering in oxygen and deuterium, and the variation of age with terminal or source energy. For H/sub 2/O the assumption of anisotropic scattering in oxygen led to a slowing-down age for fission neutrons of 25.53 plus or minus 0.3 cm/sup 2/, compared to 24.57 plus or minus 0.3 cm/sup 2/ for isotropic scattering in oxygen. The anisotropy assumption did not affect the slowing-down ages for monoenergetic sources in H/sub 2/O below 3 Mev, but at 5 Mev and above the increase in age when anistropy was included became 10% or greater, although a constancy observed between 10 and 18 Mev remains unexplained. For D/sub 2/O anistropic scattering in oxygen was assunaed throughout and the effect of isotropic versus anisotropic scattering in deuterium was investigated. It appeared to have no effect on the slowing-down age for fission neutrons, the value being 111.5 cm/sup 2/ in either case. This is explained by the average energy of the fission spectrum, 2.0 Mev, being close to a crossover energy of 2.5 Mev, below which the anisotropy effect decreased the age for monoenergetic sources and above which it increased the age. A snaall admixture of H/sub 2/O lowered the age of D/sub 2/O at the rate of about 4.5% for each 1% of H/sub 2/O in the solution. The slowing-down ages for fission neutrons in Be and BeO were calculated to be 67.74 plus or minus 0.7 cm/sup 2/ and 75.50 plus or minus 1.34 cm/sup 2/, respectively, assuming isotropic scattering in beryllium in the center-of-mass system. (auth)
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- DOE Contract Number:
- W-7405-ENG-26
- NSA Number:
- NSA-15-025440
- OSTI ID:
- 4016988
- Report Number(s):
- ORNL-2639
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-61
- Country of Publication:
- United States
- Language:
- English
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