RESULTS OF THE ANALYSIS BY MONTE CARLO OF FAST-NEUTRON SHIELDING PROPERTIES OF COMPOUND CUBICAL AND SPHERICAL SHIELDS.
OAK RIDGE NATIONAL LAB TENN
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An extensive program of calculations was performed to check certain fast-neutron dose-rate measurements made at Project BREN in 1962. The response characteristic of the modified long counter was computed. Nitrogen and oxygen cross sections were reviewed and used in calculations of the transport in air of neutrons from a Godiva source to a distance of 66 gsq cm. Transport results obtained by Monte Carlo were compared with those obtained by the moments method. A spectrum at an 80-gsq cm penetration was determined. The perturbating effect of a structure on the neutron field in its neighborhood was estimated. The effect of variations of the spectrum with penetration distances on doses computed with different weight functions was also examined the Snyder-Neufeld multicollision physical dose was found to vary with distance in a way markedly different from others examined. Work was also done on importance sampling techniques, especially the exponential transform, and the sampling problem was formulated in a simplified, approximate expression to facilitate statistical interpretations. Finally, a number of shield penetration calculations were performed to compare with the measurements and to determine the effects of shield shape, shield cavity size, and source angular distributions incident on the shields. The agreement between the calculations and the measurements was within the uncertainty in the detector response characteristic. Author
- Numerical Mathematics
- Fission Reactor Physics
- Nuclear Physics and Elementary Particle Physics