MANAGED COMPLEXITY:AN ARCHITECTURAL PARADIGM FOR THE INTEGRATION OF DIGITAL SYSTEMS IN NUCLEAR POWER PLANTS

摘要

The author posits a two-part premise concerning digital systems in nuclear power plants: 1. The complexity of some proposed safety systems appears to be incongruous with the simplicity of the functions that are required. 2. There is much to be gained if complexity can be accepted. The concept of Managed Complexity resolves these conflicting observations. Digital technology presents opportunities for monitoring and control functions that would otherwise be impossible. But some functions are inherently simple, and do not require such sophistication or even benefit from it to any significant degree. Sophisticated functions by their nature can be difficult to implement and to verify. As the tolerable incidence of failure is reduced, it becomes more and more difficult to demonstrate that a more complicated system is sufficiently dependable even if qualitative evaluation suggests that it may be so. The most critical functions, as it turns out, are generally also the simplest and have the least to gain from complex implementation. Conversely, the functions that stand to benefit most from sophisticated implementation tend to be less directly related to plant safety. This paper explores an architectural paradigm that supports both the licensing requirements applicable to safety systems, and the high degree of flexibility and sophistication appropriate to other sorts of digital systems. The objective is to establish a global system architecture that permits full exploitation of the capabilities of advanced digital systems while minimizing the nuclear licensing considerations applicable to them.