Compactibility of graphite powder for high temperature reactor fuels

The compactibility of three kinds of graphite powder was investigated, and found to be good except in the case of artificial graphite. The compactibility was found impaired by purification of the powder, but restored completely or even improved above the original value by through ball milling. And it was found that the porosity V of the compacts is related to the compaction pressure P by the function log V=A-B log P, where A and B are constants The cause of these changes observed in compactibility was investigated. It was attributed to the shape of the powder particles. The graphite particles had acquired complex shapes during the purification. The high temperatures to which the powder was exposed and purified had caused recrystallization through the action of free carbon particles precipitated from the thermodecomposition of freon gas (CCI₂F₂) used for purification. These complex shaped particles disintegrated again into thin flaky particles by thorough milling. (author)