Safety principles for advanced plant

One of the criticisms of the nuclear industry is that existing designs of reactors have evolved from systems designed originally for other, usually military, applications. The logic of this line of thinking then continues - if designers had stopped to consider the need of large scale electricity generating plant specifically, then other design solutions might have been preferred. The authors do not subscribe to this argument as a reason for abandoning existing plant, but it is useful to consider the essential safety principles which should be applied when considering new designs or developments of existing designs for the 'advanced plant' which ought to be considered for the next generation. These safety principles are discussed under the following generic headings: (1) reactivity control; (2) heat removal from the core: (a) at power, (b) decay heat removal; (3) containment; and (4) materials properties. How these principles apply in practice is considered by reference to both revolutionary and evolutionary advanced designs. Revolutionary designs claim that they utilize 'inherent' or 'passive' safety features which make them benign and incapable of causing harm to people. Evolutionary designs follow a route of improvements from existing, well developed designs which incorporate many elements of 'inherent' or passive safety but rely upon the base of experience gathered in operating existing designs over several decades. The authors argue that no reactor design to date is truly inherently safe and that all must rely to a greater or lesser extent on engineered features. Application of the safety principles provides criteria against which to judge such designs. The authors believe that the evolutionary route provides the best way forward on both safety and economic grounds. (author)