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.

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.

None

The chelate process for the extraction and decontamination of plutonium has been investigated. The process is designed as an alternate process for ihe Hanford type operation. The basic chemical factors have been studied and two flowsheeis have been developed and tested for recovery of plutonium. An over-all yield of plutonium in excess of 99% is reported for one flowsheet using benzene as the organic solvent and 98.5% when toluene was substituted for benzene. The general factors involved in establishing all details of the flowsheets are thoroughly discussed and decontamination studies are indicated to complete the study in the present equipment. (auth)

The effects of temperature, time and other variables on the rate and extent of reaction between UF/sub 6/ and various types, grades and particle sizes of commercial activated carbon have been studied experimentally. It is shown that both hydrolysis and reduction of the UF/sub 6/ occur, the latter more slowly than the former. Reduction leads to the formation of a mixture of fluorocarbons ranging from CF/sub 4/ to a wax-like maternial volatile only above 250 deg C. There is also evidence for the adsorption of UF/sub 6/ on an undetermined substrate. (auth)