The Koodankulam nuclear power units belong to the third generation of design evolution, whereas the Fukushima reactors belong to the first generation. Specifically, for the purpose of cooling nuclear fuel, when the reactor is shut down, there are four independent systems each with its own diesel generator (of 8MW), its own pumps and heat exchangers. Normally, one such system is adequate. Providing four systems ensures that even if there is a malfunction in one or two systems the other is available. The level of the diesel generator, its switch gear and controls are several metres higher than the highest tsunami or flood level expected at Koodankulam.

A special feature of the Koodankulam design is the provision of a Passive Cooling System for the nuclear reactor core. The water cooling the reactor transfers its heat to the water in the steam generators. Normally, steam is produced in the steam generators which then drives the turbine generator and produces electricity. After doing work in the turbine, steam condenses into water in the condenser and is pumped back to the steam generator. In an abnormal situation when no power is available to drive these pumps, the hot water in the steam generator flows up to an air-cooled heat exchanger located at a high level on the outside of the reactor building. Due to the height difference the hot water rises up and cold water flows down to the steam generator. This is called the thermo siphon effect and does not need a pump. This feature was incorporated in the Koodankulam design at the specific instance of India. Koodankulam reactors are the first such reactors to have this passive cooling feature.

A further feature in the Koodankulam design is called a ‘core catcher’. In the event of an accident where the molten nuclear fuel were to breach the reactor pressure vessel, it falls on to a matrix containing a large amount of neutron absorbing substances (such as boron). On mixing with this material, the nuclear fuel is rendered incapable of starting a nuclear chain reaction. Only the latest design provides for this safety back up system.

Many of the people living around Koodankulam are engaged in fishing activities. There are fears that the reactor might affect their means of livelihood. But in fact fishing activities at Kalpakkam and Tarapur are going on normally without any hindrance. Actually, the quality of life and standard of living has improved in the areas.

Some who oppose nuclear energy on principle say “let us use solar and wind energy”. At present solar energy costs about Rs 20 per kilo watt hour, and wind energy may cost Rs 10 k/Wh, and is available for about 20 to 25 percent of the time when enough wind blows. As against this, nuclear power stations are selling power for about Rs one and a half per unit at Tarapur, Rs 3 at Kaiga and other nuclear stations in the country. Power from Koodankulam will be well below Rs 3 per kWh. The two units of Koodankulam will supply about 1000 MW to Tamil Nadu, without the hassle of getting coal from Orissa or overseas. It is therefore in the interest of the people of Tamil Nadu to let the Koodankulam units to be put into operation at the earliest.

India has 20 nuclear reactors in operation and has trained a large number of competent personnel for operations and maintenance. While many of our units are 220 MW in size, units 3 and 4 at Tarapur are 540 MW in size. The two Tarapur units have been operating extremely well in the last two years. Koodankulam units are of 1000 MW capacity and hence scale up from Tarapur units is not expected to present any difficulties. The NPCIL has ensured that. (IPA Service)

(In answer to Questions by O.P. Sabherwal)