摘要 |
633,339. Atomic piles. CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE. April 2, 1946, No. 10206. Convention date, May 1, 1940. [Class 39 (i)] Moderating masses are dispersed within a uranium pile, each mass having a dimension, representing half its thickness, which is not less than the average distance collisions of a resonance neutron within the mass and which is not large enough to reduce the intensity of flow of thermal neutrons below 1/2.7 . The masses, which may be of spherical, cubical, ellipsoidal, polyhedric, rod-like or plate-like form, are distributed so that their centres or median lines form a regular spatial network. Adjoining surfaces of adjacent masses are separated by a distance L centimetres in uraniferous material containing D grammes of uranium per cubic centimetre such that 18<LD<140. The moderating masses comprise hydrogen, deuterium, beryllium or carbon and the hydrogen or deuterium may be associated with an element, e.g. carbon or oxygen, having nearly equal diffusion cross-sections for thermal and resonance neutrons and a capture cross-section for thermal neutrons which is very small compared with that of the main moderating element. The uraniferous and moderating materials may be heated to 300-400‹ C., while the reaction is starting. Specifications 614,156 and 614,386 are referred to.
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