A device of lower yield was used for the recent tests to avoid possible seismic damage to buildings in the neighbouring areas of the site, Chidambaram said in an interview to Doordarshan to be telecast tomorrow. India had conducted a 45 kt hydrogen bomb test on May 11.

Disclosing that there would be more breakthroughs in reactor technology, he said 500 MW pressurised heavy water reactors and fast breeder reactors were on the anvil, according to a Doordarshan press release.

Chidambaram, one of the top scientists involved in the tests, said many other technologies were being developed in the nuclear field which would be of great benefit to India. "I am sure there is going to be a number of breakthroughs".

Maintaining that all existing power plants with a total of 2,000 MW capacity wererunning "very well", he said four new nuclear plants of 220 MWs each were being built.