Process and structural safety: Do we need to have hazards?

Current approaches to plant design often lead to the requirement for the engineering of complex safety systems to meet demanding safety and risk criteria. Modern safety systems are highly sophisticated but can result in significant demands on designers, operators and maintainers to understand the intricacies of a system which can be subject to extensive changes during its lifecycle. Lifecycles for some envisaged storage systems in the nuclear industry now extend to over 100 years which could give rise to very large costs for operation, modification and maintenance. Often there is a tendency to concentrate on active, mitigating or operator based safety systems rather than using process design or passive systems. Ideally safe plant design should aim to design out hazards, or design in passive safeguards, with residual risks being managed by active, mitigating or response based systems. This paper illustrates how the use of process design and structural safety concepts can significantly reduce demands upon the engineering of complex safety systems. Examples are given of how process optimisation has significant reduced hazard potential and the complexity of engineering required for safety systems. Structural engineering and design concept examples are used to illustrate how simple and elegant solutions may be found early in the design process.