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DEFENCE IN DEPTH
Defence in depth: reactors

WORKED EXAMPLE: SMALL LEAK OF REACTOR COOLANT

 

Summary:

  • Potential event
  • Leak in pipe—failure would have produced small LOCA
  • All safety systems fully available
  • Pipework had been omitted from surveillance programme

Scenario

You'll remember this example from before, you can read the scenario here, and click here for the page where we determined the basic rating.

It was subsequently discovered that the pipework that failed had been inadvertently omitted from the surveillance programme. This was known but had not been rectified.
Look at the flowchart below to recap, and then click on the last highlighted item on the flowchart to continue further and look at additional factors.

INES procedure (click the last highlighted flowchart item to follow the procedure)

Figure 9, page 150 of the Manual

 

Consider need to increase rating

The leak was caused by a failed interlock that was not checked by the surveillance programme. This deficiency was known before the event but had not been rectified.

Check the answer

Answer

The small leak of reactor coolant would have a final rating of Level 1.