CHENNAI: The state-of-the-art design features of the Koodankulam nuclear power plant (KKNPP) ensures zero radioactivity leakage under any condition, besides making it absolutely safe even during unlikely eventualities like an earthquake, the plant’s site director has insisted. In an interaction with journalists here on Thursday against the backdrop of agitations against the plant, M Kasinath Balaji, site director of the KKNPP, said the enriched uranium-fuelled pressurised water reactors (PWRs) in the plant were placed inside a secure cylindrical structure with a dome top.“It is called the primary containment (PC), which has a wall thickness of 1.20 m and is made of reinforced pre-stressed concrete. It is lined with leak-proof steel plates on the inner surface,” he explained. To make it even more secure, the PC is covered by yet another structure called secondary containment (SC). Again, it is made of reinforced concrete and has a wall thickness of 0.60 m.“This ensures that no leakage of any radioactivity takes place under any condition. These structures also protect the reactor from any damage even in the case of a tsunami, an earthquake, an explosion or even an aeroplane crash on the building,” he assured.The site is in a very low seismic category zone. All important structures and equipment are designed to withstand even the severest earthquake. “The safe grade elevation starts at 7.5 m MSL (mean sea level), which is much above the expected tsunami levels as assessed by the Indian National Centre for Ocean Information Services. The features were tested during the 2004 tsunami,” he saidAsked about measures to keep the reactor cool at all times, Balaji explained that each reactor was provided with four redundant diesel generators. “Actually, just one is needed to keep the reactor cool under shutdown condition. However, four are installed, which are located at a higher elevation of 9 m above the MSL.”In the unlikely event of the non-availability of all four diesel generators, the passive heat removal system (PHRS) — a unique feature — would ensure cooling of the steam generator through natural cooling by air, he said.Twelve huge capacity hydro accumulators have been kept inside the reactor building. “To convert any hydrogen formed in case of any unlikely event, passive hydrogen recombiners will recombine the hydrogen back to water. This precludes the possibility of accumulation of explosive quantity of hydrogen in the containment,” Balaji explainedAlso, the reactor is cooled by way of natural circulation in the event of loss of power supply to the recirculation pumps by large capacity steam generators , he added.
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