INTRODUCTORY REMARKS

Thank you Dr. Haigh. I hope that those people at present responsible for reactor design and manufacture will take to heart the very important facts that you have stated and that the lessons learned from our present plant will provide a much higher standard of availability and reliability in future. Bearing this in mind we will now start the first Conference which deals with the scientific aspects of the corrosion of reactor steels.

A large effort has been mounted to study the fundamental mechanisms underlying these phenomena and to gain a precise knowledge of the rates at which reactions take place. This has been made necessary because of the discovery that the oxidation of reactor components in CO^ was, with the increasing operating temperatures, reaching an extent at which the reactors might have become inoperable in periods less than their design life. There is, you will appreciate, no reason to suppose that the integrity of the main pressure containment would be adversely affected in any way even in the case of those reactors which have steel pressure vessels. The walls of these pressure vessels are several inches in thickness, and are made from a relatively oxidation resistant material while in the severest cases of oxidation observed on the most susceptible steels the thickness of the oxide film has only just exceeded 1 mm. There are, however, cases in which clearance between moving components has been estimated to disappear and the build-up of oxide in interfaces and crevices has led to the failure of individual components. It should be borne in mind that most reactor structures contain a considerable amount of redundancy so that failure of a single part has no effect either on operation or safety and also that the straining effect of oxide in practice has been found to be lower than that predicted by experiment. However, any phenomenon which leads to unexpectedly high corrosion rates and consequent failures must be investigated in detail and related to