Methods are developed for estimating the effect on a critical assembly of fabricating it as a lattice rather than in the more simply interpreted homogeneous manner. An idealized case is discussed supposing an infinite medium in which fission, elastic scattering and absorption can occur, neutrons of only one velocity present, and the neutron m.f.p. independent of position and equal to unity with the unit of length use. (auth)

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The turnings have proved to be highly inflammable and subject to spontaneous ignition. Several experiments have been conducted at Herring-Hall-Marvin Safe Company, Hamilton, Ohio, and Baker Brothers, Inc., Toledo, Ohio, and in addition there have been a number of accidental fires, of which at least three were spontaneous. Fires of quantities ranging from several pounds to several hundred pounds have been experienced and a number of extinguishers have been tried. Records of this work are available in our files. While the work to date does not constitute an exhaustive survey of the problem, we believe that it is now safe to outline precautionary and protective measures.

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