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Tests made prior to beginning operation of the 100 Areas showed that the cooling water had a tendency to deposit a film upon the slug and tubs surfaces. This film would manifest itself as an increase in the pressure drop through the tubes and its most serious affect would be the resultant decrease in the slug to water host transfer coefficient which would increase the slug surface temperature, causing greatly accelerated corrosion rates. It was thus proposed to study film formation an a production test. This report discusses this test.

In continuing studies to characterize and identify fission product activities formed in the piles and appearing in plant dissolver solutions work was done to determine whether or not long-lived isotopes of certain elements were present. Two of the elements in this category were iodine and arsenic. The iodine isotope of particular interest was I{sup 129}. Its tellurium parent has been identified but no daughter activity attributable to iodine has been observed. The arsenic activities of interest were the long-lived isotopes (16 days and 90 days) which have been produced artificially by several different nuclear reactions.

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This weekly technical progress letter details 100 Area activities for the week of May 28 through June 3, 1946.

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There is definitely a technical possibility that atomic power may gradually develop into one of the principal sources of useful power. If this expectation will prove correct, great advantages can be expected to come from the fact that the weight of the fuel is almost negligible. This feature may be particularly valuable for making power available to regions of difficult access and far from deposits of coal. It also may prove a great asset in mobile power units for example in a power plant for ship propulsion. On the negative side there are some technical limitations to be applicability of atomic power of which perhaps the most serious is the impossibility of constructing light power units; also there will be some peculiar difficulties in operating atomic plants, as for example the necessity of handling highly radioactive substances which will necessitate, at least for some considerable period, the use of specially skilled personnel for the operation. But the chief obstacle in the way of developing atomic power will be the difficulty of organizing a large scale industrial development in an internationally safe way. This presents actually problems much more difficult to solve than any of the technical developments that are necessary, …

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The twelfth meeting of the Graphite Expansion Committee was held on December 6, 1946. A summary of the meeting is as follows. Recent laboratory studies suggest that the rate of graphite expansion decreases with exposure when the samples are exposed in an air atmosphere at ambient pile temperature, through the relative effects of atmosphere and temperature are not known. These observations are in qualitative agreement with the decreased rate of vertical expansion of the piles. The neoprene seal strips at the top of the near and far sides of the F Pile were removed during November. The cork seal in back of the Third Safety Tanks at the F Pile was also removed. Current estimates predict the general rupture of Van Stone flanges after 300,000--350,000 MD of pile operation if the rate of expansion is uniform. The working model of the split gun-barrel has been completed but is being modified to provide a key to prevent the gun-barrel flange from rotating. The proposal to replace a few tubes in operating piles, as discussed last month, has been modified in favor of more extensive work at the B Pile before moving to the D or F Piles.

Recent data show that test hole samples out from the center of a bar show greater expansion rates than do samples out from the edge of a bar. The previously noticed irregularities in expansion of test hole samples are attributed to this phenomenon. For unexplained reasons, the expansion of the graphite piles is in close agreement with the smaller expansion rates shown by test hole samples rather than with the larger rates. It is recommended that the neoprene coal on the far side of the F pile be placed before the end of the year. It is recommended that the neoprene seal on the near side of the D Pile be replaced after replacement neoprene is on hand. It is recommended that the compressed cork and about 4 inches of the cement block was in back of the Third Safety Tanks at the D Pile be removed at the time of replacement of the neoprene seal, and that the resulting gap be covered with a flexible air-impermeable membrane such as rubberized canvas. Actual measurement of the length of graphite between the gun barrels of Tube 3671-B confirms the predicted end-wise expansion of the graphite as deduced from jacking tests on …

This document details technical activities in the 100, 200, 300 areas as well as activities in the chemical development, statistical studies, and Laboratories Departments for the period of October 6 through October 12, 1946. (FI)

This technical progress report summarizes work at the Hanford Engineer Works` 100 Areas, 300 Area, 200 Areas for December 15, 1946 through December 21, 1946. (JL)

Thermal reactors that have a significant fraction of fissioning occurring just above thermal energies are studied. First, the thermal neutron diffusion equation is corrected for fast fission effects. The resulting diffusion equation is shown to be equivalent to the Fermi Age equation corresponding to the same physical assumptions. Next, the one delayed neutron group kinetic equations for the corrected thermal flux are given, and the life time of the thermal neutron is corrected by the average slowing down time. (auth)

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A revised and expanded version of NNES-DC-1. The liquid thermal diffusion method for the separation of isotopes is described. The discussion includes the experimental aspects of the method, description of equipment, and the theoretical aspects of the process as applied to the design, development, and performance criteria. A short history of the liquid thermal diffusion method from 1940 to 1945 is preserted along; with a survey of relevant literature prior to 1940. The remainder of the report is concerned with theoretical aspects. (J.R.D.)

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

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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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