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DEFENCE IN DEPTH
Defence in depth: facilities

SAFETY LAYERS - CONTAINMENT

 

At first thought it may seem obvious that containment is a safety layer, but think about it more carefully. It doesn’t stop a criticality accident, it may not prevent high radiation levels, it may not contain all the activity.

So, when is a containment provision not a safety layer?

The simple answer is, it depends whether the confinement system would change the rating of the accident to a lower range of consequences.

“Max potential consequences” INES level for worst possible accident—no safety layers

“Max potential consequences” INES level for worst possible accident—with containment

The next page gives some examples.