This technical progress report details 100 Area activities for the time period of July 16 through July 22, 1946.

At the shutdown of the B Pile, 269 active tubes were discharged and ten poison columns were charged. As a result, the pile was let considerably below critical. The present test described in this report was set up to develop methods of detecting possible changes in reactivity by periodic measurements of neutron flux in the shutdown pile. The irradiation of indium foils in an empty process tube was found to provide a satisfactory method of monitoring the shutdown pile, and was sensitive than the proportional counter with was also tried. The accuracy with which the subcritical condition can be determined is roughly 20%. The uncertainty is due mostly to the irregular arrangement of metal and poison in the unit and the resulting difficulty in representing the neutron flux mathematically.

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The physics of the shutdown of the D pile on July 2 is emphasized in the operation report. The F pile shutdown and operating specifics are also discussed. Water, corrosion, and engineering are reported for the B, D, and F areas.

The present system of classifying slugs intended for canning provides for individual measurement of dimensions on first-run MZ material, but not for their individual weighing. While the total and average weights of this type of material are determined on batches of twenty, this operation is for purposes of accounting only, and no concern is normally attached to the functional aspects of varying weights. It is thought desirable to obtain information relative to this problem. Collection of such information constitutes one of the purposes of the present test. Other purposes include collection of information which will aid in: Evaluating the improvement in overall yield brought about by adoption of the MZ diameter slugs; establishment of more suitable minimum diameter limits for recovered slugs if the present ones prove unsatisfactory; and setting up inspection procedures, if indicated, to cover measurement of dimensions as well as of weights of recovered slugs. This report provides results of this test.

This paper contains a description of the apparatus and theories of the methods successfully used for determining the fast decay periods of near-critical assemblies. The methods described are: (1) the modulation method and (2) the delayed coincidence or Rossi method

Problems in extrapolation of the rate of tumor formation by strontium 89 from animal to man are addressed. Focus of this paper is on variability of latency period between different animals.