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VARIABLE INTENSITY ISOTOPIC SOURCES.
Annual summary rept. 1 Dec 64-30 Jun 65,
CATHOLIC UNIV OF AMERICA WASHINGTON D C DIV OF NUCLEAR SCIENCE AND ENGINEERING
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The feasibility is studied of isotopic radiation sources of variable output. It is possible to change the effective yields of isotopic sources which have an output dependent on the interaction of alpha or beta particles with target materials. This can be accomplished by a change in source geometry in a manner which would result in an intimate association or separation of the radiation source material and the target matrix. The capability of changing the source output could facilitate the safe handling of a source of relatively high maximum output without requiring extensive shielding. Since these sources will produce some penetrating radiation in their lowest and the highest achieveable output under conditions of variable source geometry must be considered. In a detailed investigation of possible alpha,n reactions, beryllium was determined to be the best target material while polonium-210 and plutonium-238 were the best alpha source materials. Engineering considerations applicable to heterogeneous neutron source designs are described. These include encapsulation for physical containment of polonium within the source, heat generation and heat transfer, and mechanisms of damage to stainless steel or gold windows used for containment of polonium. For variable output bremsstrahlung sources, four nuclides identified as most suitable are calcium-45, preomethium-147, strontium-90, and thulium-170.
APPROVED FOR PUBLIC RELEASE