An assessment of possible protective coatings for BeO and BeO based reactor fuel elements

Abstract

Beryllium oxide based reactor fuel elements may be required to operate in moist air at temperatures in the range 1000 - 1200oC. In this environment, unprotected fuel elements would lose excessive amounts of BeO as Be(OH)2. Methods of preventing this loss by means of non-reactive coatings are considered. By application of established coating principles and also criteria specific to this requirement, the most promising materials are found to be Al2O3 and MgAl2O4. MgAl2O4 would be difficult to apply to form a dense crack-free coating; Al2O3 could be applied by various methods, the best of which appear to be isostatic pressing, slip casting or spraying, and vapour deposition. It is recommended that a detailed thermal stress analysis be carried out on an Al2O3 coated fuelled BeO sphere, and that experimental work should be concentrated on isostatic coating.