Thursday, November 24, 2011

Strike Right Balance Between Risk and Benefit Situation for Nuclear Power: Dr Srinivasan

Dr M.R.Srinivasan, Ex Chairman, Atomic Energy Commission (AEC) and Member, Planning Commission said , “We do not strike right balance between Risk and Benefit situation. Civil society and media should join in creating awareness about Green technology such as nuclear power and help to remove fears from general masses.” Speaking at the Green Power Conference here today, Dr Srinivasan said, “Until few years ago, the Intergovernmental Panel did not include the nuclear energy in green power, but now it is considered green power. By this time unexpected negative effect from society raised doubts about it. We have crisis in our nuclear progrmme. Two reactors of 1000 MW were to start at Kudankulam Nuclear Power Plant in Tamilnadu, but local opposition has delayed the commissioning of these reactors.”

Dr Srinivasan referred to local concern which triggered after Fukushima accident in Japan, and said, “ One should remember that not a single death in Japan during this accident happened because of nuclear radiation. Persons who suffered due to radiation is not alarming and negligible. Giving brief details of Daiichi and Daiini reactors accident, he informed that the massive earth quake of 9 recorded on Richter scale followed immediately by Tsunami were main reasons.

Describing the most effective safety system at Kudankulam Nuclear Power Plant, Dr M.R.Srinivasan told that we have put number of safety measures.He said, “ This is a 3rd Generation + model where Design Safety is incorporating defence-in-depth concept. It has five barrier systems in the way of ionising radiation preventing release of radioactivity in the environment. Fuel Matrix stage prevents fission product release under fuel cladding. The Fuel cladding prevents fission product release into primary (main circulation circuit) coolant. Main Circulation circuit prevents fission product release into containment. Inner & Outer Containment System prevents fission product release in the environment. These Five tiers of engineered features and administrative measures have been provided to protect these barriers.

Giving insight of the safety features at the Kudankulam Nuclear Power Plant, Dr Srinivasan further explained that four independent safety Trains, even though one alone is sufficient for the 100% safety of the reactor, have been installed. Explaining Active system safety at each stage he talked about six stages. They are Emergency reactor shutdown, Emergency boron injection, Containment spray, High pressure safety injection, Primary system emergency and planed cool down and fuel pool cooling and Primary circuit shut down cooling .

Referring to containment system he said Double Containment Buildings have been constructed. He talked about Primary Containment designed for LOCA peak pressure of 0.4 MPa ,Passive Hydrogen re-combiners for combustible gas control inside the primary containment , Containment spray system for pressure control and Secondary Containment designed for external effects, such as missile attack, aircraft crash & shock waves.

KKNPP has a different character which Russian Designers have not done before. Its Steam generators are connected to a large number of air coolers, as seen in motor car radiator, they are located at considerable height at the outer building and the water flow without having external power. The Passive Hydrogen Recombiners, 154 in number, passively recombines the hydrogen thus maintains the volumetric hydrogen concentration in the mixture below the safe limits thereby avoid the formation of the explosive mixtures inside the containment.

Reassuring about safety features, Dr Srinivasan said, Passive1st & 2nd Stage Hydro Accumulators are real coolant controllers. The 1st Stage Hydro-accumulators ensures borated water supply to the reactor core in the event of loss of coolant where as the 2nd Stage Hydro-accumulators ensures long term flooding of reactor core with borated water at lower pressures.

“Some of the containers were breached because of molten at Fukushima, but in our system another safety feature is provided in new design, is Core Catcher. It Confines molten core within the containment boundaries in the hypothetical event of melting of the reactor core,” he added. The Passive Annulus Space, De-pressurizing & filtering System is intended for controlled removal of steam-gas mix from the annulus in case of loss of all the power. System maintains vacuum and cleaning fluid in annular space. Inter-space kept at negative pressure to reduce releases significantly, he further explained.

Safety against external events is also considered with the highest priorities. Provisions have been made for withstanding external effects involving earthquake, tsunami/storm, tidal waves, cyclones, shock waves, and fire and aircraft impact on main buildings.

Refuting the fear of tsunami and such mishaps, he said this is baseless. Kudankulam site is located far off (about 1500 km) from the tsunamigenic fault (where tsunamis originate). Thus, if there is a tsunami, it would take time and lose its energy by the time it strikes Kudankulam site. Also, till it travel to this shore, we will get at least 4 hours to prepare ourselves.Where as against this, the tsunamigenic fault was only about 130 km away at Fukushima.We have provided enormous amount of safety features in giving different levels and the transmission line are at the highest point. We have safety measures beyond extreme situations also. Variation in tidal waves also has been taken into account.

Giving details of seismicity of Indian Nuclear power Plants, he said they are in II to IV seismic zones and there is no active fault within 5 km of their area. We have maximum earth quakes in North-east part of the country. Kudankulam is in zone II earth quake intensity.

Giving examples of Us, Canada, and other countries, he said they continue with their nuclear power progrmme. Regarding closure of Nuclear Power Plants in Germany, Dr Srinivasan explained that they are buying energy from their neighbouring countries which has origin in nuclear power. Our strategy is to go to a system where utilization of Thorium can be made. We are in process of building Fast Reactors which will work within next 5 years.

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