The application of Defence in Depth in nuclear security

Abstract

The design of reactor facilities requires the application of the concept of defence in depth when it comes to safety and security. As a nuclear safety concept, defence in depth is well defined, and its application can rely on a broad base of guidance material. Conversely, there is no such guidance for the provision of independent levels of defence in depth in nuclear security.

The multiple barriers of the physical protection system can be seen as a form of application of the concept of defence in depth, but the layers are not independent as they all contribute to detection and/or delay functions that need to be associated to a response function. The concept of defence in depth can, and should, be applied to those functions individually but this is essentially a means to provide redundancy to each function for a specific aspect of nuclear security, and does not relate to the wide-ranging requirements of an overall defence in depth as applied in nuclear safety.

To apply the concept of defence in depth coherently in both domains of safety and security, specific objectives and essential means are proposed, commensurate with the generic objectives, across the five levels defined in the nuclear safety concept. Based on this approach, a comprehensive framework for the structure of nuclear security provisions is proposed, that opens up new opportunities for improvement in areas wider in scope than the traditional physical protection system. The underlying structure can be applicable to both physical and cyber security considerations.