Experience With Commissioning of Concrete Containments

Abstract

The containment building of all Indian Pressurized Heavy Water Reactors (PHWR) are constructed from concrete and incorporate plastic liners for leaktightness. Where as the first unit constructed in late sixties is of single containment type, the current standardized design incorporates a complete doubel 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 standardized design. The test requirements in standardised design include Proof test of Primary Containment, Automatic fast isolation, Individual leakage rate test of the various penetrations, cabl seals, access airlocks, isolation devices and concrete joints followed by Integrated leakage rate tests, test to ensure the effectiveness of passive pressure suppression system, Integrate 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 that of the various leakages detected during the tests, the leakages through the concrete joints have been found to be most difficult to arrest. In case of RCC construction some deterioration in leakage integrity has been observed with time. However in the PCC construction no such deterioration of concrete has been observed. On the other hand due to the progressive repairs there has a constant improvement in the leak rates.