Pokhran-II Thermo-Nuclear Test: A Failure

The following is an enlarged version of an article that appeared in The Hindu (September 17, 2009). It is being reproduced here, with due acknowledgement to The Hindu, in view of the exceptional significance of the contents of the article and for the benefit of our readers. —Editor

This article’s aims are:

a) to correct inaccuracies in articles on Pokhran-II in August 28 and 30, 2009 of The Hindu.

b) to elucidate my conclusion that the yield of the second fusion (H-bomb) stage of the thermonuclear (TN) device tested in May was far below the Bhabha Atomic Research Centre (BARC)-claimed design prediction; and, actually failed; and

c) what we should do next.

All five nuclear tests in May 1998 were undertaken by a joint BARC-DRDO team. Drs A.P.J. Abdul Kalam and R. Chidambaram assigned full, critical responsibility for designing, building, operating and maintaining all field instrumentation for recording seismic data from the tests—vital in estimating yields. It included advanced seismic and fibre-optic sensors at many points in the shafts where nuclear devices were placed and to a radius of 2.5 km from the shaft axes on surface. The sensors and instruments were calibrated several hundred times and perfected. They fully met international standards of accuracy and reliability as acknowledged by BARC also.

The DRDO was thus deeply involved in all seismic (and other) measurements, and consequently fully aware of the BARC-projected readings vis-à-vis the DRDO’s actual measurements. One of the authors of this article, Dr Santhanam, was fully aware from key BARC team scientists of all information on device core designs and hence yields. Consequently, The Hindu statement attributed to a “former senior official of the Vajpayee Government” that he was “not privy to the actual weapon designs which are highly classified” was totally incorrect.

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

The Yield

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

The DRDO’s report was discussed at the National Society Adviser, Mr Brajesh Mishra’s meeting in late 1998 attended by Dr Chidrmbaram, Dr S.K. Sikka, the Scientific Head of the BARC team, Dr Kalam, the DG, DRDO, Dr V.K. Atre, the Chief Controller, DRDO, Dr Santhanam and the Chiefs of the Defence Services. Despite a long discussion, largely between the DRDO and BARC, both stuck to their respective positions regarding the TN device yield. Thereafter, an extraordinary ‘voice vote’ was taken by the NSA—highly unusual because the matter was technically highly complex and the Services were ill-equipped to give an opinion on yields. Most surprisingly the NSA concluded saying the government would stand by Dr Chidambaram’s opinion.

I now critique Dr Chidambaram’s claims as reported in The Hindu article entitled “Fizzle claim of TN test refuted”.

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

Dr Chidambaram’s statement—“the post-shot radioactivity measurements on samples extracted from the test site showed significant activity (levels) of (the) 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 stating “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, AEC, and an erstwhile Director, BARC, informed Dr Santhanam that trace levels of these same isotopes were detected in Apsara, a pure fission reactor not involving any fusion at all. This is exactly opposite of Dr Chidambaram’s claim.

Dr Chidambaram’s statement that “from a study of this radioactivity (viz. of Sodium-22 and Manganese 54) and an estimate of the crater radius confirmed by drilling operations at positions away from Ground Zero (the location of all the shafts), the total yield as well as the break-up of the fission and fusion components, could be calculated” is extremely surprising because after the TN test,

(a) its shaft remained totally undamaged; if the fusion stage had worked, the shaft would have been totally destroyed;

(b) the A-frame sitting astride the mouth of the shaft, and having winches to lower and raise personnel, materials etc., also remained completely intact. If the fusion stage had worked, the A-frame etc. would have been totally destroyed.

As for radioactivity levels, senior BARC radiochemists who undertook radio-assays of fission products in samples similarly drilled at Pokhran-I (of May 1974) told Dr 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 didn’t occur in the TN test alongwith the justification data.

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

The fission bomb yield of Pokhran-II from the DRDO’s seismic instrumentation was shown to be 25+2 kiloton and left a crater around 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 occurred after the TN device was detonated 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 our decade-long, grim predicament regarding the TN bomb. Our goal was to truly design, build in quantity and keep a contemporary, operationally usable, reliable H-bomb as the core of our Credible Minimum Deterrent (CMD).

No country acquired a credible seed of such a deterrent with just two tests, each of different type and of which the most important—the TN device—failed. This reality is extremely serious as we have two major, credible nuclear weapon states (NWS) as our inimical neighbours.

The central component of the CMD is reliable and scalable TN devices of proven performance through several live tests convertible into at least 150-300 kiloton missile-deliverable H-bombs. It would be farcical to send a Rs 200 crore Agni-3 missile 3500 km to hit Beijing with a 25 kt, or even 50 kt, pure fission warhead which is all we have today! We are far from possessing such a TN warhead. We must develop it speedily, successfully and master its missile interface. We must also upgrade our A-bomb in many respects.

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I am, therefore, extremely strongly of the carefully considered view that we must immediately lift our self-imposed moratorium on further testing, launch a major, comprehensive, sustained programme of nuclear weapon testing with sharply defined goals and time lines. That will also enable us to collect enough hard experimental data to validate a credible computer modelling and simulation capability which cannot be done with just one TN device which failed. Only that can enable us to

(a) achieve confidence to improve, diversify and optimise our first generation “hot arsenal”; and

(b) design and validate new weapons using our powerful indigenous computers—without having to undertake further field tests.

Such testing will cause major adverse international reactions. But we are particularly well positioned today to weather them.

Firstly, a USA, which has not ratified the CTBT and which cannot ratify it for the next three years due to Congressional processes, cannot pressurise us to sign the CTBT. As in 1974 and 1998 both France and Russia—possibly even the UK—will, at worst, keep mum, but may even extend support. An adverse reacting China need not bother us.

Secondly, our “clean” NSG waiver enables us to undertake unrestricted nuclear trade with all countries. Our testing will only lead to termination of the US 123 Agreement and some easily faceable civil sanctions by Congress.

So, the PM and Cabinet have to choose between: a really credible nuclear weapons programme absolutely central to our national security on a generational time-frame and continuing cooperation with the USA merely in nuclear power whose implementation has not even started and where we have far better foreign suppliers. In making a “choice” (the government really has no choice) the PM has to realise that our people have already voted in favour of total endorsement of our having nuclear weapons by the ecstatic euphoria with which they greeted the 1974 and 1998 tests.

Concurrently, the PM must immediately constitute, a high-level panel to design a compre-hensive Action Plan to achieve a genuine “CMD on topmost priority”.

Dr K. Santhanam was the Project Leader of the Pokhran-II nuclear tests of 1998. He worked as a physicist at BARC for 15 years. He received advanced training at the International Institute for Nuclear Science and Engineering in the Argonne National Laboratory, Lemont, Illinois, USA. Later, he was the Science Adviser in the Ministry of External Affairs and Chief Adviser (Techologies) in the Defence R&D Organisation (DRDO). He was also the Director General, Institute for Defence Studies and Analyses, New Delhi.

Professor Ashok Parthasarathi is a former Secretary to the Government of India in various Scientific Departments and was the Science and Technology Adviser to Prime Minister Indira Gandhi. A physicist, he was deeply involved in the Pokhran-I nuclear test of 1974.