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Defence in depth

What is Defence in Depth?


Defence in depth is the use of multiple barriers, systems and components to protect individuals and the environment from harm. There need to be several failures before actual harm occurs.

This is a fairly general definition of defence in depth that we can apply to any use of radiation.

Actually, we can apply this to anything harmful. We use the same approach in our cars...

The following is a definition from an early international document on defence in depth. It was probably the first official definition and resulted in the widespread adoption of this phrase.

All safety activities, whether organizational, behavioural or equipment related, are subject to layers of overlapping provisions, so that if a failure should occur, it would be compensated for or corrected without causing harm to individuals or the public at large...


  • Basic safety principles for nuclear power plants 75-INSAG-3

INSAG is the International Nuclear Safety Advisory Group