Concept for the development of nuclear reactor shutdown systems

The paper discusses the development of nuclear reactor emergency shutdown systems for bringing reactors to a safe shutdown. It describes the basic principles underlying the construction of such systems, system specifications, and how they should be realized. The aims of these principles are (1) to ensure that negative reactivity is established swiftly, with the shortest possible delay, and with a high level of reliability; (2) to provide for automatic triggering and for functional independence from control circuits, process systems and any other failed active component or simultaneous undetected failure within the system itself, and from emergency conditions outside the system; and (3) to protect against common mode failures by using systems based on different operating principles by physical separation, and by using protection stages. The paper could be used to develop an IAEA standards document on the subject. 6 refs, 2 figs, 1 tab