SIMULATION OF FALLOUT GAMMA RADIATION FIELDS BY NONOENERGETIC PLANE ISOTROPIC SOURCES.
RADIATION RESEARCH ASSOCIATES INC FORT WORTH TEX
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Monte Carlo techniques were used in a study of the gamma radiation environment three feet in air above plane sources of moncenergetic and fission-product gamma radiation. The scattered and direct-beam fluxes were computed in each of the receiver energy intervals between 0.04 and 3.5 MeV and eighteen 10-degree receiver angle intervals between 0 degrees nadir and 18 degrees zenith. Source energies of 0.10, 0.67, and 1.25 MeV, which are representative of the gamma rays from 144 Ce, 137 Cs, and 60 Co respectively, were used in the calculations. Additional calculations were performed for source energies of 0.14, 0.25, 0.40, 0.85, 1.75, 2.50, and 3.50 MeV so that the results could be weighted with the gamma-ray spectra from fallout of various ages. Detailed comparisons of the results show that the angular distribution of the dose from a fallout field is simulated with reasonable accuracy over most angles by a plane source of 137 Cs or 60 Co and over all angles by a mixture of 144 Ce, 137 Cs, and 60 Co. The simulation of the fallout energy spectra is quite poor, however, even if combinations of the three isotopes are employed. Comparisons of the Monte Carlo data with measured data for monoenergetic plane sources show good agreement. Author
- Radioactivity, Radioactive Wastes and Fission Products