mystery, further efforts to find the root cause established that the outside of the tube, the part which was not exposed to high temperature heavy water, was also for some unexplained reason "corroded".
mystery, further efforts to find the root cause established that the outside of the tube, the part which was not exposed to high temperature heavy water, was also for some unexplained reason "corroded".
This was a stunning discovery, since the outside of the failed tube was exposed only to high temperature carbon dioxide and there had been no recorded case of a similar corrosion having been seen on the outside of any tube. It is also very hard to access this part since the space was very tiny in the annulus.
The AERB then ordered that all the tubes made out of a special alloy of zirconium-niobium be checked on the outside, to their surprise, they discovered that the contagion of the "nodular corrosion" or what in layman's language can also be described as "small pox-like" was very widespread in many of the 306 tubes.
Tubes made from the same batch and used at other Indian reactors continue to operate faithfully, without corrosion.
The needle of suspicion now pointed to the carbon dioxide, a gas known to be very stable in high radiation environments.
A further postmortem revealed that the Unit-2 which is twin of the affected reactor had also been affected by a similar leak on July 1, 2015 almost ten months before the Unit 1 had a sudden appalling failure in March 2016.
Investigations into why the Unit-2 failed were ongoing but no conclusive result had been found. This literally back-to-back failure of two fully functional nuclear reactors befuddled the engineers.
Unrelenting in trying to find out the root cause, the AERB ordered that entire assembly and not just the affected tube be safely pulled out and brought to India's foremost nuclear laboratory, the Bhabha Atomic Research Center (BARC) in Mumbai for detailed failure analysis.
It is this laboratory located at Trombay in Chembur, in Mumbai that shares geography with India's famous Bollywood Kapoor family.
In addition, since India operates another 16 similar nuclear plants, a full-fledged investigation was carried out on the coolant channels of all atomic power plants and lo-and-behold the investigating team found that the "small pox" like corrosion was confined only to the two units that operated at Kakrapar.
While this gave a sigh of relief to the NPCIL but it increased the complexity on trying to unravel the true cause of the leaks at Kakrapar.
Today, Bhardwaj says the investigators are wondering if the carbon dioxide used in Kakrapar may have been contaminated which caused the "nodular corrosion" on the outside of the pipes.
The source of the carbon dioxide was further back traced and it seems only the Kakrapar plant was sourcing its gas from a "Naptha cracking unit" and possibly it has some contamination of hydrocarbons. (MORE)
(This article has not been edited by DNA's editorial team and is auto-generated from an agency feed.)
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