New Delhi, Sep 21 - Rebutting National Security Advisor M.K. Narayanan's assertions, K. Santhanam, the scientist who was involved in India's nuclear tests in 1998, Monday reiterated that the thermonuclear device exploded by India had not worked according to design expectations and showed photographs of the site that had no crater.

Santhanam, along with physicist Ashok Parthasarthi, had last week written an afrticle in The Hindu newspaper that questioned the official version that India's May 1998 nuclear tests were a success.

The NSA told a television channel in an interview that Santhanam and other scientists had ulterior motives and they were not privy to the classified information to come to that conclusion.

'He is barking up the wrong tree,' responded Santhanam at a media interaction at the Indian Women's Press Corps.

He said there were 'several inaccuracies in that statement'.

The scientist recalled that after the tests when they visited the shaft of the thermonuclear device at Pokhran in Rajasthan, it was found 'by and large undamaged'.

In contrast, the fission bomb explosion at the time which had a yield of 20-25 kiloton, left behind a large crater, he said.

He noted that there was immediate reservation among some scientists 'whether the thermonuclear device had actually worked to design expectations'.

A classified technical study report was submitted to the government towards 1998-end.

'Thereafter, a meeting was held in which scientists from DRDO and BARC participated. Despite fairly long discussions the two agencies agreed to disagree,' said Santhanam.