'Santhanam's claims over Pokhran N-tests absurd'

"There is no controversy over the yield of Pokhran-II nuclear tests. The claims are absurd," Chidambaram, who was the Chairman of the Department of Atomic Energy in 1998, said.

He was reacting to former senior DRDO scientist K Santhanam's contention that Pokhran-II tests had not met the desired objective.

Santhanam had said the thermonuclear or hydrogen bomb in May 1998 was of low yield and not the one that would meet the country's strategic objectives.

"If he has any new scientific data which has not been answered in the results of the test published by us, we will be happy to look into it," said Chidambaram, who is currently the Principal Scientific Adviser to the Union Government.
He said the results of the 1998 nuclear tests were published in great detail in international journals and it also take into account studies by several global experts.

"If he has any new scientific information which we are not aware of, it will be nice to have that data. He is a scientist, not a politician. Let him tell exactly what made him give that comment. Who are the seismologists he is referring to. We will go and look back," Chidambaram said.
Chidambaram said the scientists at Bhabha Atomic Research Centre had done a lot of measurements on site during the Pokhran-II experiments.

"They had analysed global seismic data and examined the radioactivity in the samples recovered post-shot from near the emplacement points of the nuclear devices," he said.
Emplacement point is the exact spot where the nuclear device is placed in the shaft underground and is covered by rocks to prevent radioactivity from escaping into the atmosphere.
Six months after the nuclear tests, scientists had dug out the rocks from the emplacement points and found that they had signatures of neutron-induced radioactivity, Chidambaram said.
"They (rocks from emplacement points) have signatures of neutron induced radioactivity which can come only if the 14 MeV neutrons have been generated, which means that the thermonuclear explosive device (hydrogen bomb in common parlance) had worked," the scientist explained.
"The total yield comes out as 50 (+/- 10) kilotons for the thermonuclear device, consistent with the design yield and with the seismic estimate of the total yield," he said.
Chidambaram said the scientists at Bhabha Atomic Research Centre had done a lot of measurements on site during the Pokhran-II experiments.

Chidambaram said an article in the 'New Scientist' in 1998 said that the combined yield of nuclear tests conducted by India were estimated to be about 60 kilotons.
"Roger Clarke, a seismologist at the University of Leeds, found that when the data from 125 stations -- closer to the number required by the treaty (Comprehensive Test Ban Treaty monitoring network) -- are taken into account, the estimate is nearer to 60 kilotons," he said quoting the 'New Scientist' article.
Renowned seismologist Jack Evernden "prefers the use of surface wave magnitudes to body wave magnitudes and his analysis of the May 11, 1998 seismic data is consistent with ours," the scientist said.
He said a decision to test the thermonuclear device at a controlled yield of 45 kt was taken because of the proximity of the Khetolai village at about five km from the test site to ensure that the houses suffer negligible damage.
"All the design specifications were validated by the test. Thermonuclear weapons of various yields up to around 200 kt can be confidently designed on the basis of this test," Chidambaram added.
He said some US scientists had underestimated the yield of the May 11 nuclear tests which could be traced to use of an invalid magnitude bias in their analysis.
They had reported to the US Senate that the yield of India's Pokhran-I (1974) nuclear tests was between 10 and 15 kt but used five kt as the yield as the basis to analyse the 1998 tests, Chidambaram said.
"The error was pointed out to them and they carried out the necessary corrections," he said.