Further data on the changes in length and weight of expanded graphite samples which were exposed in the pile in atmospheres of oxygen, carbon dioxide, and helium show that all three gases produce roughly the same shrinkage and weigh loss. This result is unexpected in that there is no precedent for such behavior in a helium atmosphere; however, it was found that water vapor had entered the helium stream by some unknown means and had condensed on the plugs at the inlet end of the tube. This opens the possibility that the graphite in the helium-filled tube was attacked by the reaction C + H{sub 2}O = CO + H{sub 2}. This experiment is to be repeated. The data are tabulated in this report. The expansion of the graphite before the experimental exposure was in all cases very nearly 0.6% per 1000 MD/CT. Both the D and the F Piles were scrammed by a power surge on April 14. Eight of the vertical rods did not drop into the D Pile. These and subsequent rod difficulties delayed the start up to such an extent that the reactivity losses associated with the build up of xenon poison and the cooling of …