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Santhanam’s disclosure that the thermonuclear (hydrogen bomb) test in 1998 failed to reach expectations was known earlier. Initial doubts emerged among weapons designers abroad whether Indian nuclear scientists could have contained the yield of the thermonuclear (TN) device at 45 kilotons (KT) in it its very first test. Scientific opinion in the West was divided on this question with skeptics claiming that this containment of the yield was very difficult in the first TN test; others urged that the passage of years and availability of open data had enabled Indian scientists to fashion a low-yield TN device; it was triggered by a fission core with a   fissile ‘blanket’ around it to provide the second stage fusion reaction. Chidambaram had initially denied that a boosted fission device had been used, but later informed that it had, indeed, been the trigger for the TN device. These technical details about the bomb design must be recollected, since doubts have surfaced regarding the occurrence of a TN explosion and its actual yield.

It was estimated in the West that around a 25 kiloton yield had accrued based on seismic data. What the author heard from privileged sources at the time was that the first-stage boosted fission trigger functioned, but the second stage fusion reaction did not occur, resulting in a low yield of 20-25 KT being recorded. This unhappy fact is now being aired by Santhanam. The scientific community has ranged itself on both sides of the argument. Some others have not taken a stand on these technical issues, preferring to highlight the irrelevance of yield considerations for providing the matrix of nuclear deterrence.

The question whether the TN device malfunctioned and its yield was far lower than the designed yield has to be satisfactorily resolved. Two sets of data exist with the DAE and DRDO. They need to be placed before a peer group from India and/or abroad to ascertain the truth, which is the accepted tradition to resolve scientific controversies. This however, may not happen. Why? The 1998 nuclear tests were conducted during the NDA regime with the BJP milking this event for its political dividends. But the successor UPA regime has remained content to let sleeping dogs lie, without trying to appreciate the strategic significance of a possibly failed TN device. Unfortunately, both the national strategic and political leadership in India are ‘babes in the wood’ as Santhanam colorfully described MK Narayanan.

Reverting to the scientific inquiry for estimating the yield of the TN device, the accepted methodologies used are seismic evaluations and radiochemical analysis. It is alleged that DRDO relied only on the seismic method (close-in acceleration), since radiochemical analysis was done by the DAE. In a PIB handout Chidambaram said, “the DRDO data had anomalies and had to be rejected.” Santhanam argues that the DRDO estimated the yield of all the five nuclear devices tested during Pokharan II. The DAE accepted all these estimates, except for the TN device, suggesting selectivity in utilizing the DRDO data. Santhanam further argues that the crater formed by the TN device was 25 meters in diameter, consistent with a 25 KT nuclear explosion; in fact, he has also said that only a small depression was formed in the shaft mouth. Chidambaram explains that the crater size depends “on the depth of burial and the rock medium around the shot point, and the rock medium and the shot point.” How did these obvious facts escape the attention of DRDO?

Coming to radiochemical analysis, which is the most reliable method available, Santhanam only quotes what other DAE scientists informed him. As stated earlier, radiochemical analysis was only carried out by the DAE. Why DRDO did not undertake this analysis is a mystery. Chidambaram informs that sharp increases in the isotopes Mn-54 and Na-22 were found in rock samples taken from the TN test site, suggesting a thermonuclear reaction occurring. Besides, the Mn-54/Ce-144 ratio was consistent with a fission-fusion reaction. Without access to the spectroscopic data, assertions in this regard can only be speculative.

There is another aspect to this matter.  The yield of the Pokharan-I device is believed to have benchmarked the yields of the Pokharan-II devices. Raja Ramanna and Chidambaram estimated its yield to be 12 kilotons in January 1975, but serious doubts emerged about this claim, with a yield as low as 2 kilotons being suggested.  Radiochemical analysis was apparently conducted, but the results were not made public. This controversy is significant since the seismological data from Pokharan-I was used to calibrate the yield of the Pokharan-II devices. Inflating the Pokharan-I yield would naturally affect the Pokharan-II test results.

This multitude of doubts, in fairness, requires an independent analysis of the TN test yield. A RTI application could be filed. It would be interesting to see if the Government denies this information on the ‘national security’ pretext.