Director, Centre for Environmental Studies,
1. Reactors at Koodankulam:
As part of their expansion program in Nuclear Energy, the Atomic Energy Commission purpose to establish at Koodankulam a 2 x 1000MWe plant, with pressurized water-cooled reactors which like high powered racing cars are temperamental and demand constant attention. The nuclear fission occurs in 100 tonnes of Uranium Oxide fuel in 50,000 closed packed fuel rods, the Zirconium alloy tubes of half inch diameter. These fuel bundles the reactor-core sits in a thick steel pressure vessel through which cooling water is pumped at 18 tonnes per second to carry away the heat generated during nuclear fission and use it to produce steam and electricity through a turbo generator. The fuel gets yellow-hot at its core, attaining a temperature of 4100oF (2250oC) while the metal casing around the fuel is kept at 650oF (350oC) by the cooling water. If due to an accident the coolant water gets interrupted far just a few seconds the fuel temperature rises rapidly and the Zirconium casing begins to break at 1800oF (1000oC) and melts at 3370oF (1850oC). The actual danger comes when the hot fuel begins to lump together in a molten mass that can explode the containment or seep into the ground through what is known as Chinese syndrome and release massive quantities of radioactivity into the air, water and soil environment.
In order to avoid the core melt-down, the experts have provides a series of safety devices. One major line of defence is Emergency Core cooling system which Provides instantaneous water supply that keeps the core from melting. Another line of defence is the concrete containment that surrounds the core and the pressure vessel so that even during a loss-of-coolant accident, no radioactivity will escape into the outside environment. Such Engineered safety measures also fail sometimes.
2. Places to be evacuated during accident at Koodankulam:
http://envfor.nic.in/legis/hsm/gsr347.htm [ Notification on Emergency Response by Govt.of India]http://www2.oecd.org/guidingprinciples/toc_index.asp [Chemical Accidents]
http://hazmat.dot.gov/pubs/erg/erg2004.pdf [Emergency Response system,pages.270-281]
When an accident at the nuclear plant releases enormous quantities of radio-activity into the air, water and soil environment, there will be immediate fatalities and long term genetic damage among the exposed populations. All the people within the zone of influence from the reactors must be evacuated.
Evacuation must be completed within:
6 hours for 2 to 5 km
12 hours for 5 to 25 km
24 hours for 25 to 75 km
48 hours for distances beyond 75km; downwind from Koodankulam as per the British accident scenario for the 100 MW. Size-well reactor, based on a wind-sped of 5 m/sec rain-fall of 1mm per hour and neutral stability conditions of the atmosphere.
After through scrubbing and decontamination of lands equipment and residences due to radio-active pollution from an accident, people may be permitted to return to their original residences along with their cattle and other properties after about 3 weeks upto 170km, one year upto 140km, 5 years upto 115km, 10 years upto 98km and 20 years upto 77km distance from Koodankulam nuclear plant. Depending upon the weather conditions during the accident, certain places will be more affected than others. The villages, towns and cities that will be effected during an accident are indicated in the figure.
Many villages of Ramanathapuram, Tirunelveli and Kanyakumari of Tamil Nadu and
(Based on the book "Nuclear Plants- The Silent Killers" published by the author in April 1989)