Friday, March 18, 2011

Nuclear Power Plant Categories and Visit to Kaiga

The unfortunate incident of earthquake followed by tsunami and the aftereffect - blasts of Fukushima Daiichi nuclear power plant - brought back my memories of a visit to Kaiga Nuclear Power plant. Back in 1998, during my high school days in Sirsi, I had an opportunity to visit Kaiga plant as part of an excursion. That time, Kaiga had not started operation. One unit was ready but the other one was still under construction. (Now, there are 2 more units, constructed later). Public could go inside them. (Inside visiting is strictly prohibited to public now.) We hired a KSRTC bus and visited Kaiga, Kadra dam and came back to Sirsi, after spending sometime in Karwar beach.

There were guides to take the visitors to a tour and explain nuclear power generation process and different units - reactor, container, generator, transformer, and so on ... I can't remember in detail now but I do remember the big pipes to transport Uranium and the place where it would be split. Listening to the guide, we were scared as to what happens if anything goes wrong when in production.

Kaiga power plant produces 880 MW of power, making it the third largest Nuclear power plant in India. It is based on PHWR (Pressurized Heavy Water Reactor) technology which uses heavy water as coolant. This is more efficient in terms of fuel burning and also in terms of cooling requirements than BWR. BWR (Boiling Water Reactor), the other known technology for nuclear plants, requires demineralized light water as coolant. It requires cooling for many days even after shut down. Fukushima Daiichi nuclear power plant is based on BWR. The damage caused to the Fukushima Daiichi plant got worsened after the first blast due to pouring in of sea water, which, ofcourse, was not demineralized. The plant was not designed to handle this mineralized water coolant and hence there were subsequent blasts and damage followed by radiation leaks. Two reasons, one, BWR plants require many days of cooling even after shut down, two, shortage of light water (demineralized water) and usage of sea water for cooling were prominent for its subsequent heating.

Fortunately, out of 6 nuclear power plants in India, only Tarapur plant has 2 units of BWR and the rest are PHWR. So, damage will be less in case of any natural catastrophes. Atleast after shut down, these do not pose any threat of heating up. (Radiation leakage is ofcourse has to be taken care irrespective of types)

1 comment:

kumar_undemane said...

The delay in injection of water lead to overheating of fueel bundles in BWR at Fukushima Daichi and the explosion occurred due to water+ metal reaction which liberated hydrogen. Basic cause of explosion is Hydrogen and lack of proper containment led to the release of radiation to the public domain. Either sea water or any water introduced at an early stage might have averted the incident. But power supply was totally cut off due to Tsunami waves which hindered the supply of cooling water.