Lubricants for Nuclear Reactors

Abstract

The earlier British carbon-dioxide-cooled, graphite-moderated power reactors were designed to operate without lubrication. This was necessitated by lack of knowledge of the effects of radiation and other reactor operating conditions on lubricants, and of the degree of compatibility of lubricants with reactor materials Investigations carried out over the past few years of the effects of nuclear radiation on many types of lubricant have shown that it is possible to produce materials capable of lubricating some reactor components. In order to further the development of such lubricants the U.K.A.E.A. and the nuclear manufacturing groups have co-operated in providing lubricant manufacturers with details of design and operating conditions of reactor components which it is desirable to lubricate In this paper is described the range of operating conditions which lubricants are expected to encounter in different reactors, with particular emphasis on the C02-cooled, graphite-moderated reactor. Nuclear lubricant requirements proposed by the U.K.A.E.A. to cater for many applications are also discussed With this information available it is now possible to assess realistically the types of test facility necessary for the evaluation of nuclear lubricants. Such test facilities are described. They include irradiation sources, a test rig for running under irradiation conditions, various test rigs to simulate reactor operating conditions for testing products both before and after static irradiation, and other specialized equipment The effect of radiation on both conventional and nuclear lubricants is described and the use of ‘anti-rads’ illustrated. Attention is drawn to other desirable properties of nuclear lubricants such as temperature stability, low volatility and compatibility with reactor and fuel-can materials Designers of reactor machinery have taken, and will increasingly continue to take, advantage of the developments in lubricants but, while still further advances in lubricant quality will be made, some components, particularly of the more advanced types of reactor, will probably continue of necessity to be operated without lubrication