Measurement and analysis of the leak tightness of reactor containment vessels: Experiences and results

The reactor containment vessel consisting of a reinforced concrete structure with an internal steel liner in the drywell and wetwell is designed to prevent the uncontrolled release of radioactivity to the environment. As the allowable leakage area by which this test passes is small, the containment leakage rate test is crucial not only for periodic but also for pre-operational tests. This paper presents a measurement system as well as a leakage rate analysis program for the test. The experiences for leakage examination are presented and several break holes are then identified thanks to the permeability of concrete and the localization property for gas leakage from inside to outside of the containment vessel. After repairing the leakage holes, the test is conducted and the result is satisfactory.