Tsunami preparedness of Indian reactors

June 24 2011 - TI Staff

India had planned for a massive ramp up in nuclear power capacity. The country negotiated a re-entry into nuclear power by promising to cut back on military nuclear build up. As the US negotiated an agreement to allow India import nuclear plants from suppliers, it was believed that Indian orders would lift up the global nuclear industry, just as the recent surge in airplane orders from India benefited airframers. The plan was to add 25 GW by 2020 and more later. The scenario was all rosy, until the tsunami struck in Japan. 

Since then, Indian nuclear plans have been under heavy public criticism, with protests and community action slowing progress. For instance, the proposed 9,900 MW Jaitapur complex powered by Areva's EPR has been met by massive protests. The Indian prime minister Manmohan Singh recently said all new projects should incorporate lessons learned from Japan. 

And Indian engineers seem to have keenly studied the Japanese accident and are alive to what the accident means for existing as well as proposed nuclear projects. 

In Japan, onsite was available for over 30 minutes from onsite diesel generators, and normal shutdown and cooling was in progress following the earthquake. The tsunami then flooded the site, and the diesel generators and associated switchgear stopped working, creating a sequence of events including partial core meltdown.

In India, there's only one GE design at work -- in Tarapur near Mumbai. This reactor is nearly a replica of the Fukushima reactor. 

Many of the existing plants are pressurized heavy water plants inspired by the Candu design. In these, steam generators are located at a higher elevation than the reactor, and natural circulation of the primary  system water takes place through the steam generators, and  heat is  rejected to the secondary side  of the steam generators.  

In the event of coolant failure, water can be added to the secondary side of the steam generators through other sources like firefighting water system. These firefighting water systems consist of diesel driven fire fighting pumps which do not require electric power. The emergency diesel generators are located at a height of 6m, although the Japanese tsunami wave was reported to be 11m.   

The 1.2 GW Russian VVERs coming up in the state of Tamil Nadu possess passive decay heat removal systems which  take away heat from the secondary side of the steam generators through  air-cooled heat exchangers. The circulation takes place using natural convection without the need of any motive power for circulation.   

The Tarapur boiling water reactor was installed in the 1950s. GE retreated from the Indian nuclear scene following nuclear tests in 1971 but is now competing for other mega nuclear contracts following India's nuclear agreement with the US and the nuclear suppliers group.

At Tarapur, natural circulation cooling is achieved through emergency condensers located at a higher elevation to the reactor where the heat is rejected to water on the secondary side of the condenser. Water can be added to the secondary side of the emergency condenser in case of a coolant failure or a power shutdown.   

Indian officials assure that the available features are adequate for coping with design basis natural events.  "However,  with a view to enhance  safety to higher levels and build more defense, we are planning to incorporate measures such as provision of hook up arrangements  to add water  to the required safety systems of the reactors through mobile diesel-driven equipment, and additional arrangements for adding water to spent fuel pools in plants," they say.