Bacon Anisotropy Factor and Crystallite Sizes Measurements on Pyrocarbon Specimens. Dragon Project Report

The use of pyrooarbon as deposited in fluidised beds for coating fuel particles is of considerable importance in the nuclear field as for example in the Dragon Reactor Experiment, When pyrooarbon is deposited on ceramic fuel particles by thermally decomposing methane or other hydrocarbon gases the resulting product is found to be more or less oriented depending on the deposition conditions [1]. Moreover it has also been found [2] that the dimensional changes of pyrooarbon under neutron irradiation depend strongly on the degree of orientation and crystallite perfection. Consequently it is of primary importance to characterise the pyrooarbon in terms of fluidising conditions, i.e., gas flow, kernel charge, deposition temperature and resulting density, crystallite size L_c, and degree of preferred orientation or BAF, This report describes crystallite size and BAF measurements currently done in Dragon by X-ray diffractometer and outlines a quick method for assessing the BAF.