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So unclear on the nuclear front

G Balachandran contends that the Pokhran II yield isn’t under dispute. He’s wrong, write K Santhanam & Ashok Parthasarathi.

india Updated: Nov 10, 2009 21:34 IST

G Balachandran’s article ‘Splitting atoms, not hairs’ (Sept 23) on the yield of Pokhran II’s thermonuclear (TN) device (hydrogen bomb) tested on May 11, 1998, requires several corrections and detailed comments. Balachandran wrote that there was “no confusion about the design/planned yield of 1998-TN test: it was 45 kilotons”. This is not in dispute. What is in dispute if whether the TN device actually recorded the designed yield.

The US National Security Agency and US Atomic Energy Commission (AEC) weapons laboratories placed the yield at 20-25 KiloTonnes, not 45 KT (1 KT is the energy release equal to 1,000 tonnes of TNT). Balachandran is totally unaware that apart from yield measurements made by the Defence Research and Development Organisation (DRDO) team led by Santhanam, comprehensive experimental data was collected by the Aviation Research Centre (ARC), a highly specialised science and technology agency of the government. The ARC used its state-of-the-art seismic array, tailor-made for detecting and measuring the yield of nuclear tests. Independent of both the DRDO and the Bhaba Atomic Research Centre (Barc), the ARC unambiguously established in its classified report to the government the following: 1) the yield of the TN device was substantially lower than 45 KT; 2) An atom bomb, also separately tested and the first-stage ‘trigger’ of the TN device, had a yield of 20-25 KT. Thus, the TN device yield would, at best, be 20 KT only.

APJ Abdul Kalam and R Chidambaram officially designated the DRDO to be solely responsible for all-site instrumentation for yield measurement of the Pokhran II tests. The DRDO’s instrumentation fully met international standards. Barc was fully satisfied with its performance. On no occasion did Barc express any doubts. Barc also gave the DRDO its expected ground acceleration and movement figures from the TN test to measure against. Unfortunately, measurements conclusively proved that the TN yield was substantially lower than Barc-projected pre-test figures. So Balachandran’s statement that Barc questioned the sensitivity of the DRDO instrumentation is baseless. This came up only after Santhanam questioned the yield of the TN device as an afterthought to defend the indefensible.

The DRDO’s site instrumentation included its own CORRTEX system, accelerometers, ground motion sensors and high-speed imaging systems. Recording and processing of readings from this comprehensive instrumentation package was undertaken by special DRDO computers. The CORRTEX system also gave a far lower TN yield than the Barc-claimed figure of 45 KT.

As for Balachandran’s Barc–fed contention of radiochemical (RC) method-based analysis being the most accurate method of estimating the yield of a device, the considered view of nuclear experts is that any estimation of yield made by the mass spectrometry (MS) method is far superior to the RC method. Raja Ramanna insisted that MS be used in the 1974 Pokhran I test yield analysis. The head of the RC Division in Barc gave a detailed report to Ramanna personally showing that the Pokhran I yield was lower than claimed by Barc. Ramanna had accepted the report’s scientific results — but not its politics. He admitted this to Parthasarathi in 1994. Thus, the report was quickly and quietly buried.

Why was the MS method not used by Barc in Pokhran II? Or was it used and its results again suppressed — this time by Chidambaram because they were ‘inconvenient’? Balachandran says the DRDO used only the seismic method in its yield measurements. We conclusively rebut this. He also states that “the DAE had used all six methods of nuclear yield estimation, whereas the DRDO used only one.” The methods used by Barc were 1) two seismic methods for ground acceleration and ground movement 2) CORRTEX 3) Radiochemical. That’s four methods. What about the other two? The truth is that no other methods were used. Santhanam’s team saw no Barc-CORRTEX system anywhere at the site.

The DRDO used two seismic methods, plus CORRTEX and FORRTEX. This also adds up to four methods, not six. Further, both alleged Barc seismic methods were undertaken using a 30-year-old seismic array at Gauribidanur in Karnataka, over 1,500 miles away from Pokhran. Both the DRDO’s seismic methods involved ‘close-in-field’ (right close up to the TN device-containing shaft). Balachandran then says that no critic presented any scientific argument in support of their case. This is false. As early as end-1998, Santhanam’s DRDO team presented a detailed, classified report to the government, including a telling comparative table of Barc-predicted ground acceleration and movement numbers against actually measured ones.

The NDA government and its successor the UPA blindly endorsed — and continue to endorse — the Barc claim. This attitude has seriously compromised our national security. Balachandran also conveniently ‘forgot’ to mention that Barc used data from DRDO’s instrumentation for its estimate of yield of the atom bomb. However, when the same instrumentation showed the yield of the TN device was far lower than Barc readings, he chooses to claim that the instrumentation was faulty! Barc speaks with a forked tongue.

K Santhanam was Chief Adviser (Technology), DRDO and Programme Director, Pokhran II

Ashok Parthasarathi was Science and Technology Adviser to Prime Minister Indira Gandhi

The views expressed by the authors are personal