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Defence in depth: facilities



We have now covered the basic rating process. We need to look at a few aspects at the start of the process before we try using the procedure and the wizard to rate events. The first one is shown here:

Excerpt from Figure 10, page 151 of the Manual

Let's look at this in the context of discovering a structural defect in a safety component.

The basic approach is explained here.

The first part of the process (steps 1 and 2) identifies the significance of the component in which the defect or leak occurred. It does this by assuming that the defect actually led to failure or the leak reached its maximum size, and then calculating what the INES rating would be.

Obviously, this is not the actual rating so the third step is to reduce the rating depending on how likely the defect was to lead to failure or to the leak getting worse.