Pokhran-II thermonuclear test, a failure

A critical analysis of the technical facts can lead to no other conclusion. BARC must learn to tell the nation the truth.

September 17, 2009 12:17 am | Updated December 17, 2016 04:21 am IST

Several inaccuracies in the claims made by BARC and in the articles published in the press, including The Hindu , on Pokhran-II need to be corrected. We have hard evidence on a purely factual basis, to inform the nation that not only was the yield of the second fusion (H-bomb) stage of the thermonuclear (TN) device tested in May 1998 was not only far below the design prediction made by the Bhabha Atomic Research Centre (BARC), but that it actually failed.

All the five nuclear tests conducted in May 1998 were undertaken through a joint BARC and Defence Research and Development Organisation (DRDO) team. A.P.J. Abdul Kalam and R. Chidambaram assigned the DRDO team the critical responsibility for all the field instrumentation to record seismic data from all the tests: this was vital in estimating the yields. The seismic sensors were placed at many points in the device shafts and out to a radius of 2.5 km. The sensors and instrumentation were calibrated several hundred times and perfected. They fully met international standards and were acknowledged to be so by BARC.

The DRDO was thus deeply involved in all the seismic measurements and was fully aware of the BARC-projected readings vis-À-vis its own measurements. One of the authors, Dr. Santhanam, was personally aware in detail from key BARC scientists of the core designs and hence the projected yields. Consequently, the reference in a report published by The Hindu on August 28 (headlined “’Fizzle’ claim for thermonuclear test refuted”) attributed to a “former senior official of the Vajpayee government” that I was “not privy to the actual weapon designs which are highly classified,” was incorrect.

The DRDO also designed and conducted numerous tests of the High Explosive (HE) Trigger of the TN test. BARC scientists witnessed these tests, took copies of test records, and expressed satisfaction with the DRDO’s work.

Over May-October 1998, DRDO produced a comprehensive report of actual seismic readings vis-À-vis values predicted by BARC, mentioning why the former showed considerably lower yields than the latter.

The DRDO report was discussed at a meeting called by National Security Adviser Brajesh Mishra in late 1998. The meeting was attended by Dr. Chidambaram and Dr. S.K. Sikka, the scientific head of the BARC team; Mr. Kalam, the Director-General of the DRDO; Dr. V.K. Aatre, the Chief Controller of the DRDO, Dr. Santhanam, and the Chiefs of the Defence Services. Despite a long discussion, largely between the DRDO and BARC, both stuck to their positions on the TN device yield. Thereafter, the NSA took a ‘voice vote’! This was highly unusual because the matter was technically very complex and the services were ill equipped to give an opinion on yields. Most surprisingly, NSA concluded saying government would stand by Dr. Chidambaram’s opinion.

Dr. Chidambaram’s claims and those in Atomic Energy Commission statement reported on September 16 under headline “No reason to doubt the yield of 1998 nuclear test: AEC” are wrong.

BARC basically argued that the geological structure of Pokhran was different from test sites elsewhere. However, the DRDO and BARC utilised the same published information in their calculations of TN device yield. BARC accepted the DRDO’s yield estimates of the fission (A) bomb, but not of the TN device, although the latter’s shaft was situated only a few hundred metres from the former’s shaft. Globally, geological structures do not change dramatically at such small separations. So BARC’s argument to “explain” a lower TN yield is untenable.

Dr. Chidambaram’s statement that “the post-shot radioactivity measurements on samples extracted from the test site showed significant activity [levels] of radioisotopes Sodium 22 and Manganese 54, both of which are byproducts of a fusion reaction rather than a pure fission [device]” is incorrect. He should indicate the exact level of activity instead of merely saying “significant activity” as the activity level determines whether a fusion reaction of the magnitude claimed by BARC actually occurred.

Dr. P.K. Iyengar, a former Chairman of the Atomic Energy Commission and a former Director of BARC, informed me that trace levels of these same isotopes were detected in Apsara, a pure fission reactor not involving any fusion at all. This is the exact opposite of Dr. Chidambaram’s claim.

Dr. Chidambaram’s statement that “from a study of this radioactivity and an estimate of the crater radius confirmed by drilling operations at positions away from the shaft, location, total yield and break-up of fission and fusion components, could be calculated” is extremely surprising. First, after the TN test, its shaft remained totally undamaged: if the fusion stage had worked, the shaft would have been totally destroyed. Secondly, the A-frame sitting astride the mouth of the shaft, with winches to lower and raise personnel, materials and so on, also remained completely intact. If the fusion stage had worked, the ‘A’ frame would also have been totally destroyed.

As for radioactivity levels, senior BARC radiochemists who undertook radio-assay of fission products in samples similarly drilled at Pokhran-I (of May 1974) told Santhanam that the yield announced to the media was substantially higher than what they had submitted to Dr. Raja Ramanna. Dr. Chidambaram must publicly substantiate any claim that it did not occur in the TN test along with justification data.

Dr. Chidambaram states: “BARC scientists worked out total yield of TN device as 50 +10 kt — consistent with design yield and seismic estimates.” However, he subsequently asserts: “BARC experts established DRDO had under-estimated yield due to faulty seismic instrumentation.” BARC cannot eat the cake and have it too.

The fission bomb yield from the DRDO’s seismic instrumentation was 25 +2 kiloton and left a crater 25 metres in diameter. If the TN device had really worked with a yield of 50 +2 kt, it should have left a crater almost 70 metres in diameter. Instead, all that happened was that sand and mud from the shaft were thrown several metres into the air and then fell back, forming a small depression in the shaft mouth. There was no crater.

This factual analysis reveals India’s decade-long, grim predicament regarding the failed TN bomb and so our Credible Minimum Deterrent (CMD). No country having undertaken only two weapon related tests of which the core TN device failed, can claim to have a CMD. This is corroborated by fact that even after 11 years the TN device has not been weaponised by BARC while the 25 kiloton fission device has been fully weaponised and operationally deployed on multiplate weapon platforms. It would be farcical to use a 3500-km range Agni-3 missile with a 25 kiloton fission warhead as the core of our CMD. Only a 150 – 350 kiloton if not megaton TN bomb can do so which we do not have.

(K. Santhanam was Project Leader, Pokhran-II. He worked as a physicist at BARC for 15 years. Later he was Chief Adviser (Technologies) in DRDO for 14 years and was then also Director General, Institute for Defence Studies and Analyses, New Delhi. Ashok Parthasarathi, the co-author of this article, was S&T Adviser to Prime Minister Indira Gandhi and deeply involved in Pokhran-I, of May.)

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