Experience with Hydrogen Recombiner at KKNPP

In Nuclear Power Plants, containment is the final physical barrier for the release of radioactivity into the atmosphere and its integrity needs to be ensured under all operating conditions of the plant. For severe accident scenarios in which hydrogen generation is envisaged, containment parameters depend on the Hydrogen concentration which is a balance between generation and depletion rates. To limit the hydrogen concentration to acceptable values and to ensure containment integrity during such accident scenarios, KKNPP is equipped with Passive Catalytic Hydrogen Recombiners (PCHRs) as a hydrogen mitigation system. The present paper aims at sharing the experiences on the recombiners at KKNPP. KKNPP is installed with PCHRs at different locations of the containment. PCHR has a pin type Platinum coated catalyst arranged in the form of frames in multiple layers within the casing. To ensure the operability of the system during the need of the hour, regular surveillance is carried out in every RSD. The surveillance includes testing of the catalyst as per the designer specified criteria. Currently, these PCHRs have experienced 10 years of containment atmosphere at KKNPP Unit-1 and the tests have provided sufficient data for understanding the performance of the catalyst. The test results have indicated that the functionality of the system is ensured as per the design intent and provides the confidence of its availability till its service life.