Experience with commissioning of concrete containments

The containment buildings of all Indian Pressurized Heavy Water Reactors (PHWR) are constructed from concrete and incorporate plastic liners for leak tightness. Whereas the first unit constructed in late sixties is of single containment type, the current standardized design incorporates a complete double containment (except the common base raft) extended to the access airlocks, various penetrations and pipings open to the primary containment atmosphere. Additional containment associated engineered safety features have been provided in the standardized design. The test requirements in the standardized design include proof test of primary containment, automatic fast isolation, individual leakage rate test of the various penetrations, cable seals, access airlocks, isolation devices and concrete joints, effectiveness of passive pressure suppression system, integral leakage rate tests on secondary containment, interception of leakages by secondary containment, vacuum maintenance test, tests on the other ESFs, etc. The tests carried out so far indicate leakages through the concrete joints have been found to be the most difficult to arrest. In the case of reinforced cement concrete construction, some deterioration in leakage integrity has been observed with time. However, in the prestressed cement concrete construction no such deterioration of concrete has been observed. On the other hand, due to progressive repairs there is a constant improvement in the leak rates. (author). 1 tab., 5 figs