5.28. Where it is technically feasible, the design should provide for the visual inspection of containment structures (including the tendons for prestressed concrete containments), penetrations and isolation devices.

5.29. Visual inspection of the containment envelope, including appurtenances and penetrations, should be made in conjunction with each of the tests specified in paras 5.18-5.24. Visual inspections are important for the proper monitoring of ageing effects.

Availability tests

5.30. The design should provide a capability for monitoring or testing all items of equipment in containment systems at intervals that reflect their importance to safety, or for otherwise demonstrating the necessary reliability for the containment systems individually or as a whole.

5.31. A capability for testing isolation valves during plant operation, such as by actuating them to function with a partial stroke, may contribute greatly to the assurance of the reliability of the system.