Director, Centre for Environmental Studies,
I) Reactors at Kaiga: It is proposed to establish a nuclear plant (PHWR) at Kaiga in Karnataka with an initial capacity of 2 x 235 MW and an ultimate capacity of 2000 MW . In the proposed pressurized heavy water reactors the core is located in a steel vessel known as Calandria that is filled with heavy water and kept at atmospheric pressure. Low pressure heavy water is used as a coolant, permitting natural uranium as fuel. The fuel rods separated laterally by spacers consist of natural uranium dioxide pellets clad with Zircaloy. Without reactor shut down one machine inserts fuel bundle into pressure tube at one end while spent fuel bundle is discharged at the other end. As in a pressurized water reactor, the primary circuit of PHWR consists of several loops. For each loop a number of pipes emanating from individual pressure tubes feed into an outlet header that is connected to a steam generator main coolant pumps and inlet header that again feeds individual pressure tubes. The coolant temperature and void coefficients are positive. Primary shut-down is provided by vertical absorber rods immersed between the pressure tubes with secondary shut down, if necessary by injection of chemicals under pressure into the moderator. Double containment is provided for more safety.
II) Reactor Safety Problem: Although pressure tube design has positive and negative points from a safety point, the possibility of uncontained fuel melting accidents is not eliminated in this design. Even if pressure tube design precludes the chances of massive pressure vessel failure, the long length, surface area and complexity of the primary system piping results in greater possibilities for loss of coolant accidents. On-line refueling provides additional means by which loss of coolant accidents can be initiated. As the pressure tubes are exposed to the full neutron flux, they experience the consequential weakening effects. Due to deuterium-zirconium interact ion, delayed hydride-cracking occurs in the piping system. Moreover the natural uranium heavy water void co-efficient of reactivity is positive and any loss of coolant accident leads to power execursion. A loss of coolant accident coupled with scram failure leads to rapid melting of fuel and possible common mode breach of the containment. While heavy water results in large and hazardous tritium inventories, extensive use of zirconium in the core provides for a large zirconium-system reaction potential. The multi unit station design may ultimately result in common mode failures which have not been studied in depth in safety analysis in the Indian environment with considerable degree of emphasis on indigenization.
III. Alternate Sites: As practiced in some European states, Tunnels can be driven in one of the mountains on the
By siting the proposed nuclear platn at Kaiga in close proximity to a major population centre at Karwar Naval base, the nuclear experts are deliberately violating the norms even if public health and environmental safety will be in jeopardy. Even the defence forces and personnel of the “Sea-Bird” project may be adversely affected. The dense and natural forests of the tropics need not be destroyed. In case of power failure the reactors are always provided with alternate sources of energy from a few independent power generators that go into action within a few seconds or minutes. Hence the special facilities or secondary importance such as power-lines, rocky foundations and reservoir storage on kali river cannot over-ride the crucial aspects of environmental protection in Karwar district and its vicinity.
IV. Places to be evacuated during accident at Kaiga: After thorough scrubbing and decontamination of the land sand equipment due to radioactive pollution from an accident people can return to their original houses along with their cattle after one year upto 140km after 5 years upto 115km and after 20 years upto 77 km distance from the nuclear plant. Depending upon the weather conditions during the accident, certain areas will be more affected than others. The villages, towns and cities that lie within the zone of influence of an accident in the rectors at Kaiga are marked in the figure. While Karwar, Yellapur, Londa, Honavar, Kumta and Ankola of Karnataka, Chavil, Quepem and Madgoan of Goa lie within 77km. Bhatkal, Siddapur, Sirsi, Hangal, Mundgod, Kalghatgi, Haliyal, Khanapur, Hubli and Dnarwar of Karnataka and Panaji, Ponda Bicholim and Mapuca of Goa fall within 115km distance from the proposed nuclear plnt. While Bainduru, Sagar, Sorab, Haveri, Shiggaon, Savanur, Kundgol and Belgaum of Karnataka and Chandgad, Amboli and Santvadi of Maharashtra lie within 140km, Coondapur, Byadgi, Ranibennur, Shirhatti, Gadag, Nargund, Gokak and other places close by lie within 170km from Kaiga. Evacuation must be completed within 6 hours for 2 to 5km; 12 hours for 5 to 25km; 24 hours for 25 to 75km and 48 hours for distances beyond 75km from Kaiga as per the British accident scenario based on a wind speed of 5m/sec; rainfall of 1 millimeter per hour and neutral stability conditions.(This article is based on the Book "Nuclear Plants-The Silent Killers" published in April 1989)