Jeffrey LewisIndia's H Bomb Revisited

Yes, Virginia, India’s H-bomb fizzled.

K Santhanam (who was director of test site preparations for India’s 1998 nuclear tests; pictured above, handing the firing keys to the range safety officer) has admitted what everyone else has known for a long time — that India’s 1998 test of a thermonuclear device was unsuccessful:

“Based upon the seismic measurements and expert opinion from world over, it is clear that the yield in the thermonuclear device test was much lower than what was claimed. I think it is well documented and that is why I assert that India should not rush into signing the CTBT,’‘ Santhanam told [the Times of India] on Wednesday.


Sources said that Santhanam had admitted that the test was a fizzle during a discussion on CTBT organised by IDSA. Karnad also participated in the seminar. He told TOI that no country has succeeded in achieving targets with only its first test of a thermonuclear device.

“Two things are clear; that India should not sign CTBT and that it needs more thermonuclear device tests,’‘ said Santhanam.

This is a subject we have covered in some detail here at Arms Control (see The Bomb, Dmitry. The Hydrogen Bomb, 10 April 2005.)

1. Yes, India’s thermonuclear device probably probably did fizzle, looking at the seismic data.

2. Some Indian scientists, including the former chairman of India’s Atomic Energy Commission PK Iyengar and now Santhanam, keep pointing out this somewhat embarrassing fact because it is part of an argument for India to resume nuclear testing.

3. India’s evident need to resume testing to complete development of a thermonuclear device is the principal reason that I opposed a “clean” NSG exemption for India (See: Will India Test Again?, 23 June 2008 ).

Here is my original post on the subject, reproduced because I am lazy and I recall the reading list was somewhat helpful:

Did India successfully test a two-stage thermonuclear device in May 1998?

There are substantial reasons for skepticism. India claimed that it detonated three devices on 11 May 1998 at Pokhran (right)—a 43-kiloton thermonuclear explosion, a 12-kiloton fission explosion and a 0.2-kiloton fission explosion. (India then claims to have conducted low yield tests on 13 May 1998.)

Seismic analyses (particularly Wallace et al) conclude the cumulative yield for the 11 May tests was only 12-kilotons. A yield that low is probably “too small to have been a full test of a thermonuclear weapon”—suggesting the test fizzled.

The US intelligence community reportedly shares this conclusion. Govenment officials told Mark Hibbs of Nucleonics Week that analysts from Livermore’s Z Division “have now concluded that the second stage of a two-stage Indian hydrogen bomb device failed to ignite as planned.” Subsequently, “senior U.S. expert” confirmed to Hibbs that this account was correct.

Indian scientists have been quick to dispute these estimates, arguing that Western scientists have made inaccurate assumptions about the geography of the Indian test site. This argument has always struck me as unconvincing, in part because of data that has been presented from the 1974 test.

A former chairman of India’s Atomic Energy Commission, PK Iyengar, has used calculations similar to those of Wallace et al to suggest that the second stage of the two-stage thermonuclear weapon failed to ignite—“the fusion core burnt only partially, perhaps less than 10 per cent.” Iyengar, however, has an axe to grind—he wants India to resume nuclear testing.

Such failures have plagued new nuclear designers before. China’s seventh nuclear test (CHICOM 7)—and second thermonuclear weapon—also fizzled, resulting in a yield estimated at the time between 15-25 KT.

Similarly, Livermore’s first attempt at “super” also failed—resulting from what Herb York called “a simple design flaw … engendered by the novelty of the technology and by our inexperience.”


Brian Barker et al, “Monitoring Nuclear Tests,” Science 281:5385 (25 September 25, 1998) 1967-68 (subscription).

Mark Hibbs,”India May Test Again Because H-Bomb Failed, U.S. Believes,” Nucleonics Week 39:48 (26 November 1998) 1.

Mark Hibbs, “Because H-Bomb Fuel Didn’t Burn, Iyengar Pleads For Second Test,” Nucleonics Week (1 June 2000) 6.

PK Iyengar, “Nuclear Nuances,” The Times of India (22 August 2000) (full text in the comments).

SK Sikka et al,”The recent Indian Nuclear Tests: A Seismic Overview,” Current Science 79:9 (10 November 2000) 1359-1366 (draft).

Gregory van der Vink et al, “False Accusations, Undetected Tests and Implications for the CTB Treaty,” Arms Control Today 28:4 (May 1998) 7-13).

Terry C. Wallace, “The May 1998 India and Pakistan Nuclear Tests,” Seismological Research Letters 69 (September 1998) 386-393 (preprint).]

Herbert York, Making Weapons, Talking Peace: A Physicist’s Odyssey from Hiroshima to Geneva (Basic Books, 1987) 78.


  1. Jeffrey Lewis (History)

    Nuclear Nuances

    Credible Deterrent Through Testing

    By P K IYENGAR, August 2000

    (The author is former chairman of the Atomic Energy Commission)

    AFTER a long period of indecision and ambivalence regarding its nuclear preparedness, India detonated five nuclear devices in May 1998. Consequently, it declared itself a nuclear weapons country. However, it is unlikely that we will be accepted as a weapons country under the Comprehensive Test Ban Treaty (CTBT), because there is no provision for threshold states maturing to become nuclear powers.

    When Prime Minister Atal Bihari Vajpayee visits the US next month, the CTBT will certainly be one of the important issues raised by the Americans. There may be political arguments both for and against signing the CTBT, but if we have decided to follow a policy of nuclear deterrence, which will require weaponisation, then, scientifically, we have no option but to continue testing. It is the scientific case that I wish to make here.

    If one goes by the numbers for the total nuclear yield put out by the Department of Atomic Energy, which I see no reason to dispute, the yield of the thermonuclear device detonated on May 11, 1998 was around 40 kilotons. This is a rather low yield. If the yield was deliberately kept low to restrict damage to the nearby villages, then surely it would have been more sensible to test the thermonuclear device separately, and not along with the 15 kt fission device. Now, the thermonuclear device itself consisted of two parts: the fission trigger and the fusion core.

    The crucial question is not what the total yield of the device was, but what was the ratio of fission energy to fusion energy? Clearly, for a given total yield, the greater the fraction of the fusion energy, the more efficient is your thermonuclear device. In my opinion, that ratio musts have been around 1:1, and no one has so far, to my knowledge either publicly or privately, disputed that number. Therefore, by my estimate, the fusion yield could not have been more than 20 kt. Further, it seems likely that a fission `spark-plug’ was used at the centre of the fusion core, in which case the actual fusion yield would have been even less.

    Sticking to the larger number of a 20 kt fusion yield, one can easily calculate that the amount of LiD fusion material needed would be only around 400 grams or around 500 cc. This is a very small size for the fusion core, and the actual core used must certainly have been much larger. This suggests that the fusion core burnt only partially, perhaps less than 10 per cent. This can easily be checked; if the burn was only partial, there should have been a lot of tritium produced, which should have been detected after the explosions.

    In such a complex system as a two-stage thermonuclear device, getting any burn at all is a credit to the abilities of the scientists and engineers of the Bhabha Atomic Research Centre (BARC). However, a thermonuclear device that only burns partially is certainly inefficient. Logically and scientifically, the next step would be to improve the design of the device to achieve greater efficiency. This is particularly important from the point of view of a weaponisation programme.

    The government has declared a policy of maintaining a minimum nuclear deterrent. Nuclear deterrence means that we have a demonstrable nuclear capability that deters a potential adversary from attacking us. For us to have a nuclear deterrent we must weaponise. For this, we must have fusion weapons, because these are smaller, lighter, and more efficient than fission weapons. But for that deterrent to be viable, we must master all aspects of thermonuclear weapons, and demonstrate that expertise not just in one, but many thermonuclear designs, particularly those of greater efficiency.

    Whether that should include a neutron bomb or not, is not of the essence. In a neutron bomb, one establishes a thermonuclear burn by igniting only a part of the core, and making the burn propagate. This is the crux of the matter in designing an efficient thermonuclear device. One may not have a neutron bomb in one’s arsenal, but it would strengthen our abilities if we successfully tested one.

    Some people argue that we have benchmarked our computer simulations using the data from the Pokhran tests, and, therefore, further weapons can be designed based on those computer simulations. We should note that we have conducted only one thermonuclear test, and that too of low yield. It is, as mentioned before, likely that this device burnt only partially. Devices that are more efficient will have to be built. In order to weaponise, we will need missile-mountable devices, which will have a different geometry. They will also have to be of higher yield. Then these will have to be made compact, and integrated with delivery as well as command and control systems. Can our nuclear deterrent be credible if we go through this long process of weaponisation without a single additional test? The bottom line is that we just cannot hand over to the army, or deter potential aggressors with, weapons based on computer simulations.

    It is unscientific to embark on a long programme of weaponisation, and develop elaborate plans for maintaining a credible nuclear deterrent, all based on just one, low yield, thermonuclear test. When we do not do this for the Agni or Prithvi missiles, why would we want to take this risk for nuclear weapons? I am sure that the BARC scientists themselves, like their DRDO counterparts, would prefer to take a more conservative approach and test further to refine their designs and their capabilities. This is the scientific way. It would be wrong for the government to pressure the scientists to put a premature end to nuclear tests, for political expediency.

    In principle, India accepts nuclear disarmament, and hopes its problems will be solved if all countries accept non-discriminatory, global, nuclear disarmament. Yet, this is unlikely to happen, from what we see around us as well as in the `N5’ (five nuclear weapons) countries. In spite of long and friendly discussions with the US, we haven’t come to any concrete decision relating to a new status under the CTBT. If we are to maintain our independence in today’s world, it is essential for us to have a credible nuclear deterrent, and this requires us to continue testing.

  2. Cheryl Rofer (History)

    Mnhm-hmnh. As the prospect of ratifying the CTBT draws closer, we can expect to hear more of how everyone’s weapons don’t work well enough to give up testing.

    That’s not to say that I don’t believe that India’s H-bomb didn’t work as planned. The evidence is there.

    From the United States, we can expect to hear that there are hitherto undisclosed safety questions that can only be resolved by testing, although this ploy becomes less and less credible with repetition, along with the assurances that the RRW doesn’t need testing.

    Or, come to think of it, maybe it does! 😉

  3. mark hibbs

    Is this cool or what?

    I remember what happened when I wrote that article in the fall of 1998 saying in the headline that the US had concluded that the Indian “H-Bomb failed.”

    Almost overnight after the article was published I got a huge bundle of papers from BARC and DAE sent to me by diplomatic pouch from Mumbai informing me with all kinds of numbers that I was wrong.

    I gave the papers to laboratory geoscientists at several European countries and the US. One main CTBTO monitoring scientist told me explicitly: “Nope. The stuff in these papers is shitty science. They haven’t shown that you are wrong.”

    That having been said, please note however that, as PK Iyengar had made the case to me back a decade ago, once again this “news” is surfacing in India because their bomb makers want to keep testing. Some things in India are changing fast. Other things aren’t.

  4. charles meade (History)

    I got into a huge pissing match with the Indians on this issue as I was the principal author of Barker et. al. 1998 which had the yield estimates far below the Indian press releases. A number of Indian scientists tried to submit a comment to Science rebutting our analysis. We asked them to provide the in-country seismic data on which they based their analysis, but they refused. Luckily, in the end, their comment was rejected and never published.

    On a related note, I saw the other day that wikipedia has a glowing description of the Indian 1998 tests, citing the inflated yields and saying the tests were a huge technical accomplishment. See

    In the next day or so, I plan to submit a corrected analysis.

  5. mark hibbs

    Charles, I recall one of your co-authors back then explained to me in nitty-gritty detail your frustration on this with these guys. Please do correct the record for posterity.

  6. charles meade (History)

    Their arguments at the time were quite remarkable. They said that our seismic data didn’t reflect the true yield because of a complex interference pattern caused by the simultaneous tests. Under these circumstances, they said that one could only obtain the correct yield from near field data. We said, “fine, show it to us”. They refused and that was the end of their paper.

  7. Yale Simkin (History)

    The Indian argument:
    For us to have a nuclear deterrent we must weaponise. For this, we must have fusion weapons, because these are smaller, lighter, and more efficient than fission weapons.

    is a lot of hooey.

    They claim to be building a deterrent force, not a war-fighting arsenal with a counter-force capability.

    For the size and mass of their likely early-generation fusion designs, they can instead use basic fission bombs yielding in the multi-dekakiloton range – multiples of the hell weapons that incinerated Hiroshima and Nagasaki.

    That should be sufficient to deter any rational adversary. And if they aren’t rational, then you have no deterrent.

    A nice discussion of the actual yields of the Indian tests is from Carey Sublette back in 2001, here

  8. Gus (History)

    India should not sign CTBT…it will be utterly foolish esp. since chinese are bullying it with nuclear weapons and also lab testing pakistani weapons.
    VA, USA

  9. Akash (History)

    This article suggests that the BARC group may not have shared the entire weapons design with the DRDO team (Santhanam was DRDO) & that radiological analysis conducted subsequently was supportive of the BARC position.

    (Or it could always be that they “agreed to disagree” at the time but Santhanam decided to finally go public.)

  10. Jochen Schischka (History)

    Hmmm…i’m asking myself: what does this affair (potentially) tell us about pakistani nukes?

    Or north korean ones?

    Nah, those are of course much more powerful than we can reconstruct from seismic data on their testing activity…

  11. JF (History)

    Dr K Santhanam has taken charge as Director, Defence Food Research Laboratory, Mysore, wef 1 May 2000.

    Dr Santhanam obtained his PhD in Biochemistry from the Indian Institute of Science, Bangalore. After a stint in the US as a Post- Doctoral Fellow and at VP Chest Institute, University of Delhi as Reader, he joined DFRL in 1976. In 1986, he was awarded a Visiting Fellowship in the US for two years to investigate the biochemical mechanism of induction/prevention of a food contaminant-induced liver cancer. He served as Director, Defence Research Laboratory, Tezpur, from April 1994 to August 1996. Later, he served at DFRL as Additional/ Associate Director.

  12. Ashfaq (History)

    What a mess. I reckon the Indian government needs to start another weapons lab to bring BARC to heel.

    Maybe they can contract someone like Reliance to build and staff a competing lab. The private sector should be able to build a more reliable weapon than BARC.

  13. Dr Subroto Roy (History)
  14. G.Balachandran (History)

    Evidemtly CTBTO does not think much either of the CTBTO scientist that Hibbs spoke to (who probably does lot of shitty science himself). The CTBTO site lists the following as the yields of the Indian and Pakistani tests of 1998 and the Indian test of 1974.
    11 May 1998 India conducts a nuclear test (three nuclear devices) ~45 kt total thermonuclear device (?), plutonium implosion, low-yield test Shakti Pokhran Desert, India
    13 May 1998 India conducts a nuclear test (two nuclear devices) <1 kt low-yield tests Shakti Pokhran Desert, India
    18 May 1974 India tests its first explosive nuclear device ~12-15 kt plutonium implosion Smiling Buddha Rajasthan, India
    28 May 1998 Pakistan conducts a nuclear test (five nuclear devices) ~9-12 kt total HEU fission device, boosted fission device (?), 3 low-yield tests Chagai-I Ras Koh, Pakistan

  15. G.Balachandran (History)

    By the way has Dr. Meade or any of his collegues published anywhere their estimtes of the yields of the nuclear tests of any other country- China, for example, or US/Russia for that matter before those governments announced their yields, if at all, and what is their record of accuracy in their predictions?

  16. Jeffrey Lewis (History)

    The list of authors on the Science paper is pretty much an all-star team of seismologists, with a list of publications that certainly includes Russia and China, as well as others:

    Brian Barker, Michael Clark, Peter Davis, Mark Fisk, Michael Hedlin, Hans Israelsson, Vitaly Khalturin, Won-Young Kim, Keith McLaughlin, Charles Meade, John Murphy, Robert North, John Orcutt, Chris Powell, Paul G. Richards, Richard Stead, Jeffry Stevens, Frank Vernon, Terry Wallace

    There is no shame in having the first H-bomb test be disappointing — it happened to the Livermore and Haiyan. This is the the reason for supporting a test ban.

  17. Yale Simkin (History)

    G.Balachandran points out that the CBTBO posts a table of significant nuclear tests, and lists yields and presumed designs for Indian and Pakistani explosions.

    This listing should not in any way be considered as accurate. For example, it lists the outrageously misguided 1974 Indian test as ~12-~15 kilotons. It was actually much smaller, closer to 8 kilotons. Don’t use that crude table to beat up researchers doing actual science.

  18. G.Balachandran (History)

    8 ton yield for the 1974 test was not the one claimed by india. That was the estimate of the scientists who disputed the 1998 yields. If they are wrong about the earlier ones they could as well be wrong about the latter one. In any case can any of the scientists who estimated the Indian yield give any evidence of their estimating capabilities by giving their estimate of the yield of any of the tests conducted by USA/Russia/China or any other state whose yield was not announced at the time of the test and the accuracy of their estiamtes with the actual yields as when they were announced by the state conducting the test? Or is it possible they have no such example? I would certainly interested as a matter of scientific proof of their capabilities?

  19. jwy

    Forgetting for the moment the debate about yield/fizzle, does anyone have any fairly reliable estimates of the volume and mass of the Indian warhead with re-entry vehicle?

  20. Raj S (History)

    >> There is no shame in having the first H-bomb test be disappointing — it happened to the Livermore and Haiyan. This is the the reason for supporting a test ban.

    Quite the opposite – if it ‘failed’ it provides sufficient political ammunition to claim why we will not sign the CTBT and that we will test again in future.

    Using Santhanam to orchestrate this is a rather transparent ruse anyway – he’s ex-RAW, and was the site prep lead, not even part of the BARC weapons team.

    With the CTBT process where it is, this convenient ‘admission’ merely serves as a shot across the bow to underscore that India will not sign CTBT, at the very least, not under it has tested again at a time of its choosing.

    It does not really matter that it will earn us the opprobrium from various quarters – that has been par for the course for us since 1974. There are far too many countries with their fingers already in the nuclear trade pie.

  21. Rajesh Rajagopalan (History)

    What we are witnessing is the restart of the Indian debate on CTBT and its trajectory would largely depend on what happens in the U.S. Senate. In other words, a replay of the 1999 debate in India, which also centered around whether the two stage device worked as advertised. That debate ended when it became clear that the US was not going to ratify the CTBT. Incidentally, P.Chidambaram published a subsequent paper in 2002, available here. I am not competent to judge it but can someone else?

  22. Siddharth

    See also:

    ‘Update on the yield of May 11-13, 1998 Nuclear Detonations at Pokhran’ by S.K. Sikka, Falguni Roy, G.J. Nair, V.G. Kolvankar and Anil Kakodkar

    In the May issue of BARC News Letter, Sikka and Kakodkar (1) had presented preliminary results about the close-in ground motion measurements and seismic records and estimated the combined yield of May 11-13, 1998 explosions (POK2) to be around 60 kt. In a recent paper, Sikka, Roy and Nair (2) analysed the globally measured body-wave magnitudes (mb) reported by International Data Centre (IDC), Arlington, USA for 51 stations. An azimuthal plot of these mb values (see Fig.1) showed that mb values are in general smaller at the azimuths away from the north direction. This has been explained to be because of the time delays introduced by the physical separation of the two large explosions of May 11 (1 km apart in the east-west direction) with the help of synthetic seismograms for various t* values (0.3 s-0.5 s) (Fig.2). In view of this, the resultant amplitude of the two explosions is less in directions other than north-south direction. The average mb estimates of IDC (mb = 5.0) and US Geological Survey (mb = 5.2) are therefore smaller than the true mb values. After taking into account the necessary correction, a value of mb = 5.39 was obtained as the global average. The revised mb estimate gave an average combined yield of 58 ± 5 kt after taking into account the geology of Pokhran test site as calibrated by our POK1 explosion. Since then, we have obtained data from 100 more seismic stations and also carried out analysis of close-in acceleration data for yield determination. We report these results here.

    As we have stated above, both the IDC and USGS average values need to be corrected for the source geometry. This is further confirmed by the analysis of mb values from 160 station data of IDC, USGS and Kyrgyz network(KNET). Fig.3 shows a histogram plot of the azimuthal variation of mb values, averaged in 20° intervals, in the northern hemisphere (there are not enough points in the southern hemisphere). The peaking of mb values in the north direction is in agreement with the east-west alignment of our big explosions, with the shaft for the fission device located in the east direction with respect to that of the thermonuclear one. Wallace (3) reports that he did not observe any significant variation in the mb values in an azimuthal plot of USGS data. This is not surprising if one uses only USGS data because there are very few points in the north direction in these data, in fact, about 70 seismic stations lie in the narrow azimuth of 300 – 320° , which distort the plot.

    It is well known that although there is lot of uncertainity in the determination of absolute yield from seismic data alone, the relative yield between two tests can be evaluated with a much higher confidence by use of the difference in body wave magnitudes,

    D mb @ C2 log (Y1/Y2) (1)

    where Y1 and Y2 are the yields of the two explosions and C2 = 0.75 to 0.8. Fig.4 gives a comparison of the seismic wave forms for the 1974 and 1998 Indian explosions as recorded at GBA. The ratio of the amplitudes of the P waves is 4.5. A similar difference is indicated by the common seismic stations for these explosions as shown in Table 1. After making necessary corrections for the source geometry of 1998 Indian explosions, an average D mb » 0.5 is obtained. This, using equation (1), leads to a yield ratio of 4.45 between 1974 and 1998 explosions is obtained, almost the same as reported by Sikka and Kakodkar (1). Taking the yield as 12 to 13 kt for the 1974 explosion, the yield of May 11 explosions is obtained as 53-58 kt. The yield of the POK1 is based on seismic data (4,5) and rock mechanics pheno-menology calculations (6). The latter reproduced the measured cavity radius, spall velocity and the extent of the rock fracturing for this yield of the 1974 event. It may be noted that IDC shows the yield of the 1974 explosion in their data base as 10-15 kt and the same is also quoted by Norris (7).

    Fig. 5 shows the measured accelerations along with curves derived from Nevda Test Site (NTS) and from the Rio Blanco and Rulison-Gas Buggy explosions of USA, (these were peaceful nuclear explosions experiments for hydrocarbon gas reservoir simulation, all scaled to a yield of 58 kt and for the relevant depths of detonations(8). The acceleration values of our May 11, 1998 explosion are well bracketed by the Rio-Blanco-Rulison curves. This is interesting as these explosions have been carried out in sedimentary formations (shale-sandstone) away from NTS. Now the observed yields and mb values for these tests are

    Mb Y

    Rio Blanco 5.4 90 (30×3) kt

    Rulison 5.3 43

    Gas Buggy 5.1 29

    Thus, it is clear that the derived yield estimates of 60 kt for POK2 by us are surely not an over estimate.

    It is reported by Sykes and Evernden(9) that the test site dependence is very small for Rayleigh wave magnitude, Ms. This is because for explosions in hard rock at many test sites estimates of yield on using the NTS (Ms versus Y) formula have been close to the actual yields. The four Ms values of May 11 tests as reported by USGS range from 3.4 to 3.8. Our measured ones at Jodhpur, GBA and Bhopal were 3.6, 3.6 and 3.9 respectively. Assuming relation between Ms and yield of Murphy (10) for less than 100 kt

    Ms = 2.14 + 0.84 log Y (2)

    and an average value of 3.62 for Ms from the above data, a yield value of 58 kt is obtained. This is in perfect match with our reported value.

    In two recent papers, Wallace (3) and Barker et al (11) describe the capability of the International monitoring system for estimating the source parameters by fitting their findings of May 1998 nuclear explosions of India and Pakistan. They seem to claim following capabilities :

    1. It could detect, locate and identify the explosions promptly.

    2. It could estimate the yield of detected explosions from scaled spectrum even for uncalibrated regions and undetected explosions with no knowledge about source geometry.

    3. The system is capable of detecting

    multiple tests.

    For 2, Wallace used USGS average mb of 5.2 and gave a yield of 10-15 kt and Barker et al gave 9-16 kt based on IDC average mb of 5.0 for our May 11, 1998 explosions. It may be pointed out that the difference of 0.2 units in mb values will give a yield ratio of 1.8.

    Wallace (3) also uses the NTS relation for the scaled depth of burial

    d = 122 y1/3 (3)

    to estimate the yield of our 1974 explosion. The above relationship is for containment of radioactive gases. He erroneously uses it as a scaling law for formation of a subsidence crater. US publications list that subsidence craters may form from scaled depth of burial of 60 w1/3 m onwards e.g. see reference 12. His assumption that Pokhran I formed a subsidence crater is also not tenable. In fact, Pokhran I created a shallow crater. The difference between a shallow crater and a subsidence crater is that the crater radius in the latter is very nearly the same as cavity radius. For Pokhran I, the crater radius was 47 m compared to the cavity radius of 30 m. (This should be 27 m according to the formula of Terhune (13)). Our design for optimum depths for nuclear device emplacement is based on careful computer simulations taking into account the geo-physical properties of the concerned rock medium. All the five explosions of 1998 – and in fact the earlier one of 1974 – have confirmed the correctness of our emplacement design procedure.

    The assumption of Wallace (3) and Barker et al (8) that the geology of the Pokhran site was similar to that of former Soviet Shagan River site is scientifically not correct. It may be noted that Indian plate is different from the Eurasian plate The close in rock formations of an explosion determine the seismic coupling and the value of the constant C1 in the relation

    mb = C1 + C2 log Y (4)

    This was realised by the scientific community after the threshold test ban treaty, which set the maximum yield of a permitted nuclear test explosion to be 150 kt. When the former Soviet Union conducted these tests, higher mb values were measured by western seismic networks. From these, using NTS values for C1 and C2 , some American Seismologists estimated the Soviet yields to be about 300 – 500 kt. Later on joint USSR-USA calibration experiments supported the Soviet yields to be near 150 kt. This led to a procedure (called correction of site bias) of estimating true Soviet yields. This involved substracting a value of a few tenths from the observed mb values or increasing the value of C1 constant by the same amount (Stevens et al, 14). Such site biases have now been found to exist for different testing locations e.g. between eastern and western United States and between Shagan River and another former Soviet site Deglen, less than 70 kilometers away from the former. In view of the above, the value of C1 @ 4.05 derived by Sikka et al., by making the NTS mb versus Y curve pass through the POK1 point, we feel, is the correct one, which for a magnitude of 5.4 for POK2 gives a yield of 58 kt.

    It is well established that the yield of a nuclear explosion can be determined with more certainity by close-in ground motion measurements, radiochemical methods and hydrodynamic shock measurements. Without the availability of such data and surroundings of the device, it will be not just highly subjective but erroneous , as explained above, to draw firm conclusions on yields. Such data is unlikely to be available to investigators other than those involved in the test . In the context of the May 13 explosions, Barker et al have given a detection threshold of mb(Lg) of 2.5 at Nilore (NIL) in Pakistan at a distance of 740 km from the Pokhran site. Based on the yield ratio derived from equation (1) and using the yield of May 11 tests as 9-16 kt, they give the yield of May 13 explosions between 30 to 300 tons. With the actual yield of ~ 60 kt for May 11 tests, this detection limit will be ~0.1 to 1 kt very close to our announced values. Thus, while the CTBT monitoring mechanism does appear to detect high yield tests, the claims on its capability to correctly estimate the yield, to detect multiple tests and to detect low yield tests appear doubtful. To infer about the type of device itself is stretching the perception of the system capability too far, particularly if one remembers that PNE thermonuclear devices have been tested down to a yield of at least 2.3 kt (Cabriolot test, referred to in the paper by Siddons(15)).

    Authors are grateful to Dr. R. Chidambaram for many illuminating discussions.

    References :

    1. Sikka, S.K. and Kakodkar, Anil, BARC News Letter (1998), 172, 1-4.
    2. Sikka, S.K., Roy, F. and Nair, G.J. (1998), Current Science, 75, 486-491.
    3. Wallace, T.C., (1998) Seismic Research Letters.
    4. Chidambaram, R., Ramanna, R., (1975), Proc. Tech. Committee on

    Peaceful Nucl. Explosions IV (Vienna,

    IAEA) p.421.
    5. Nair, G.J. (1974), AG 224, Procurement executive, MOD, UK.
    6. Chidambaram, R., Sikka, S.K. and

    Gupta, S.C. (1985), Pramana, 24, 245.
    7. Norris, R.S. (1993), Bull. Atomic Scientists, 4 p 48-49.

    8. Holzer L. (1977) Proc. Tech. Committee on Peaceful Nucl. Explosions V (Vienna, IAEA), p.27.

    9. Sykes, L.R. and Evernden, J.F. (1982), Sci. Am. 247, 29.

    10. Murphy, J.R. (1977) , Bull. Seismol.Soc. Am. 67, 135.

    11. Barker, B. et al (1998), Science 281, 5385.

    12. Teller, E., Tally, E.K., Higgins, G.H. and

    Johnson, G.W. (1968), “The constructive

    uses of nuclear explosives”.
    13. Terhune, R.W. (1978), UCRL-52395, p.8.

    14. Stevens, J.I., Murphy, J.R. and Rimer, N. (1991), Bull. Seismol. Soc. Am.
    81, 1272.
    15. Siddons, R.A. (1972), Proc. Tech. Committee on Peaceful Nuclear Explosions III (Vienna, IAEA) p.353

    Table 1 : Difference and azimuthal correction in mb values at common stations between 1974 and 1978 Indian explosions



    Azimuthal corretion

    for mb


    D mb

    (a) + (b)
    EKA (UK) 0.3 0.1 0.4
    YKA (Canada) 0.5 0.0 0.5
    GBA (India) 0.5 0.0 0.5
    NUR (Finland) 0.2 0.2 0.4
    KEV (Ukraine) 0.4 0.0 0.4
    NB2 (Norway) 0.4 0.1 0.5
    COLA (USA) 0.6 0.0 0.6
    PMR (USA) 0.5 0.0 0.5

    The value of mbl corresponds to body wave magnitude for 1974 Indian explosion and mb2 corresponds to that of 1998 Indian explosions. The average D mb value comes to 0.5, which corresponds to a yield ratio of 4.45 between the POK2 (11 May 1998) total yield and the POK1 (18 May 1974) yield.

  23. Alex W. (History)

    “There is no shame in having the first H-bomb test be disappointing — it happened to the Livermore and Haiyan. This is the the reason for supporting a test ban.” — And it’s of note that the first Los Alamos H-bomb was an “extremely conservative” (Garwin’s words) design, more of a proof of concept than a weapon. And, of course, it’s worth noting that the first weaponized H-bomb — Castle Bravo — was successful, though of a wildly different yield than had been predicted.

    H-bombs are, in a word, hard, especially if you are trying to weaponize them or do anything creative (e.g. Livermore’s dud).

  24. Balachandran (History)

    Dr. Lewis and Dr. Simkin have lavished accolades on the non-Indian scientists who have made the estimates of the yields of the Indian tests and questioned the Indian estimates. (Dr. Iyengar, who is critical of the Indian tests does not, however, question the Indian estimates as he says- see his quote above- “If one goes by the numbers for the total nuclear yield put out by the Department of Atomic Energy, which I see no reason to dispute, the yield of the thermonuclear device detonated on May 11, 1998 was around 40 kilotons.”
    So Can Dr. lewis or Dr. Simkin- or anyone else for that matter- give me some references wherein the aforementioned scientists have made estimates of the yields of the tests conducted by others, the Chinese, for example, wherein their estimates had been afterwards authenticated by the yield data released by the state conducting the test. I think Dr. wallace did publish a paper estimating the yields of the Chinese tests but as far as I know these have never been confirmed or denied by the Chinese. Surely some Armscontrolwonk reader can give some citations which confirm the predictive power reputation of the scientists praised by Dr. Lewis and Dr. Simkin? In the absence of any such evidence one can only assign to their estimates the same degree of authenticity that one usually ascribes to the astrological predictions made in the media.

  25. charles meade (History)

    Balachandran writes….

    So Can Dr. lewis or Dr. Simkin- or anyone else for that matter- give me some references wherein the aforementioned scientists have made estimates of the yields of the tests conducted by others…

    I suggest you go to and type in

    “jr murphy” “yield estimation”

    You will get 120 references that will be a good start for your reading.

  26. Raj S (History)

    There have been claims that the Indian side did not respond when queried for specifics, beyond a point.

    The reason for that is that they work under the constraint of secrecy. They have no obligation to provide any further information, and whatever information they do present is done in the interest of scholarly output.

    Every western estimate works within the constraint of having a fraction of the data that the Indian scientists have at their disposal. On the other hand, the Indian side constrains itself by providing just as much information as it deems necessary, and no further. The motives of the two sides in questions are not identical.

    It is therefore rather easy but naive to claim ‘victory’ based on lack of response to queries; beyond a point, neither will there be responses, nor will the likes of Wallace have any access to either Indian nuclear facilities or test data.

    Any estimates on their part depend on extrapolations built around the only information they have, i.e. seismic data. None of that can replace actual data, which they neither have, nor will be accorded access. From a scientific perspective, the side with the data holds the cards.

  27. Balachandran (History)

    I thnak Dr. Meade for giving me the reference of a site which I found very useful to get an understanding of the seismic estimation of nuclear yields. However, I am a bit confused. I do understand that Indians and Americans have different interpretations of the English language- we use “s” where Americans use “z” etc- but I did not realise that the two countries have different meanings for not only letters but for words and sentences and paragraphs as well. My request was for somebody to refer me to some article/report wherein – the seismologists so eloquently praised by Dr. lewis and Dr. Simkin and now apparently Dr. Meade as well- had given their estimates of a test done by say, Chinese, when the test was done and which was validated later by the official release of the yield. Such estimates in case of others,say USSR may do as well. It was that simple. Please let me know where I can find such an estimate etc. What Dr. meade has chosen to give me a whole lot of references where the method has been explained. While I find that very useful, my original question still remains unanswered.
    So either Dr. Meade has misundertsood my query or is obfuscating. Or is my english so difficult to understand?
    In the absence of any such reference, one can only conclude that the aforementioned seismologists may have had some bonafide intentions in publishing data on India and attempting to rubbish Indian scientists or their intentions could be malafide- one can think of many possible reasons for such malafide intentions. As of this moment I have no idea as to which is their real motive.
    Perhaps some other Armscontrolwonk reader can translate my Indian english into American english and get somebody to answer my original question.

  28. Anon.

    Mr. Balachandran, your english is excellent. But, please do realise we are not your secretaries here, we’re more or less ordinary folks who have jobs and families to attend to as well as read and comment on this site. Do your own searching for the references you require, or pay someone to do it for you. The search engine Dr. Meade directed you to is a good tool for such a search.

    Raj S, the problem for the independent observer is that the side which has the data may or may not also have motives to announce false yield values. E.G. to hide flaws in the device that their deterrent very much depends on. (Note that this applies to any NWS, including the USA.) While most of the world may not care if the real yield is 20% off the announced value, for the arms control community such a details are important.

  29. charles meade (History)

    One point that needs to be emphasized to the Indian skeptics. The fact is that the US Government has invested huge amounts of money over the past 50 years to develop seismic yield estimation techniques. And for good reason. Some of this was done in direct collaboration with the National Labs at NTS, comparing seismic data with rad chem estimates. In this way, seismic data provided a quick and robust way to provide yield estimates. But the US also had a huge interest in determining the yields of foreign nuclear tests (e.g., the TTBT). And to do it correctly. And so the methodologies were refined many times over using data from many sources, classified and unclassified. In other words, these are not techniques developed by a few random “cranks”.

  30. Raj S (History)

    Anon: that’s all certainly possible, but all such allegations are at best within the realm of faith-based conjecture, and does not carry any scientific weightage.

    The side with the data remains the most credible source of information, to the extent that it provides information. Beyond a point, BARC will not provide information, and independent observers really have no authority to ask them for it. It may be a dilemma for such observers, but they have no other choice.

    To the western skeptics, as much as the US may have copious experience with seismic data evaluation, seismic data is not the sole parameter used to compute yields. No amount of guesstimations about the Pokhran Test Site using NTS data can replace the real thing. Further, the Indian side has a lot more information at its disposal than seismic data.

  31. G.Balachandran (History)

    I agree that I must end my quest now for answer to the the question that I had originally posed..
    Anon, I did not, and never did, expect anybody to act as my secretary. I only expected that professionals working on the subject- which many Armscontrolwonk readers are- to say “Hey, Balachandran, X had done exactly what you were looking for in year Y. Hear is the reference. So there. Don’t waste anymore of my time” That did not happen. And from the obfuscatory nature of many of the replies- they are good scientists, they have spent a lot of money etc- I do not think there is any reason to expect that such a reply to my query will be forthcoming.
    However, I did learn something about the scientific temper of some of the respondents.
    I thank Armscontrolwonk for its assistance in my quest.
    By the way I can think of dozens of reasons why the foreign experts could- with malafide intentions/motive- announce false yields. But that is another story.

  32. cybersurg (History)

    tsk tsk. While India’s tests were a fizzle there are some semantics involved in the word fizzle.

    I quote from an article at the following url:
    “ Consequently, a fizzle yield could be defined as a few percent of the design yield
    for an assembly system similar to Nasasagi type bomb. Thus, whether North Korean test
    was a failure would depend on its design yield. For example, if North Korea design yield
    was 20 kt as others usually did for their first tests, then a 0.5 kt could be a fizzle yield
    (because the ratio of the test yield to the design yield is 2.5% (0.5kt/20kt), which is less
    than the defined fizzle yield (say around 3%). However, if North Korea planned a yield of
    4kt, even a test yield of 0.5 kt (12.5% of designed yield) would be not a fizzle yield.
    Indeed, Chinese officials have told American nuclear experts and diplomatic officials that
    Pyongyang had informed Beijing in advance an estimated explosion yield of
    approximately 4 kilotons.12”

    I would also like to point out that the CTBT monitoring systems are not so hot – having missed India’s May 13 tests altogether. Perhaps those tests fizzled too?

    That is a comfortable conclusion as far as India is concerned. As long as the Non Proliferation Ayatollahs live in the self congratulatory environs of cloud cuckoo land – people will keep testing clandestinely. And overtly once in a while.

    And refuse to sign on the dotted line…

  33. Ashfaq (History)

    It’s highly probable that the test failed, but I do have an unresolved question.

    Wasn’t there an initial overestimate for the Soviet yields under the TTBT? From what I’ve read, it seems that dispute was resolved after the Soviets provided access to calibrate their test site.

    So why wouldn’t the Pokhran case be similar? Is there a way to get a definite answer without getting access to the test site?

  34. Ashfaq (History)

    “One point that needs to be emphasized to the Indian skeptics. The fact is that the US Government has invested huge amounts of money over the past 50 years to develop seismic yield estimation techniques.”

    This is a weak argument, because the USG invested similarly in technical means to detect test preparation. Yet it was fooled by the test team and learnt of the tests from TV. So sure, the techniques have not been developed by “cranks”, but then clearly the Pokhran test team were not amateurs either.

  35. G.Balachandran (History)

    coming to another topic, is the definition of a nuclear fizzle as being “few percent of the design yield’ a commonly accepted definition?
    Also there are a number of ways of determining the yield of a nuclear test. The three types of seismological estimates based on the body, surface and Lg waves, the radiochemical analysis, the hydrodynamic “CORRTEX” method and the ground motion estimates. Of these all except the seismological estimates require some sort of onsite presence at the test site.
    How do these estimates rate in terms of their accuracy? or at least the order in which they would be placed according to accuracy? Since from some of the responses to my earlier query, it seems many of the scientists quoted seem to have workd with classified data, as part of US government sponsored studies, have there been any publications giving the order of magnitude of the errors of the various methods, without compromising any previleged information?

  36. cybersurg (History)

    Mark Hibbs’ comment “shitty science” sums up what scientists in India are accusing each other of practising. Lest Mr Hibbs assume that he can remain personally immune to scathing comparisons of his own science let me quote a reference from Evernden in a letter to Physics Today (December 1998) as a counter point to Mr Hibbs’views

    I quote:

    “In numerous articles, most particularly one that I co wrote with Gerald Marsh and that was published in this very Magazine (August 1987 page 36) I made it perfectly clear that accurate yield estimates can be extracted from seismic data if only people will take the trouble to do the analysis properly.A note of mine in Physics and Society (October 1998, page 10) explains how to achieve accurate yield estimates of the Indian and Pakistani explosions. (India said is largest one was 43 kilotons and Pakistan said its was 18 kt; my estimates are 46 kt and 19 kt respectively) – Jack F Evernden”

    In scientific circles the need bring in irrelevant external comparisons like shit indicate a possible need to bolster feeble arguments with skatological adjectives. That is shitty science too. “Mark” your words, Mr Hibbs.

  37. Andreas Persbo

    Cybersung, perhaps you should read Marks comment one more time, slowly.

  38. cybersurg (History)

    Sorry Mr Persbo. No can do.

    Hibbs says:
    “I gave the papers to laboratory geoscientists at several European countries and the US. One main CTBTO monitoring scientist told me explicitly: “Nope. The stuff in these papers is shitty science. They haven’t shown that you are wrong.”

    This only means that Mr Hibbs claims to have got some papers, and he gave them to someone else, and they told him “You are right my friend”

    This claim is not much different from saying that Mr. Hibbs had a dream in which an angel appeared and told him the real truth. In another bygone era that would have been as credible as Mr Hibbs seems to be to some people now.

    But it’s not shitty science because its not science at all.

    Having read Mr Hibbs communication carefully yourself Mr Persbo, perhaps you should spend some time asking if is is, or is not utter trash in terms of science. What was that again about “shitty science”?

  39. Raj S (History)

    Mark Hibbs et al presume BARC wants to work with them to achieve common ground on the yield estimates. That’s surprising, considering the west has had more access to Chinese weapons labs than to BARC.

    In reality, BARC reports what it deems necessary – the yields they obtained, with just as much data as they deem sufficient to disclose.

    One needs to realize that BARC and the non-proliferation community have entirely different goals. BARC is the premier weapons lab of a de-facto nuclear power, and as such, their intentions will always be at cross-purposes with the so-called ‘independent observers’ of the non proliferation community.

    At minimum, they’ll provide just what they deem fit, and at worst, they’ll actively present data that undermines or confuses the observers, while leaving them no means to further their investigation.

    Every time some major non-proliferation/disarmament treaty comes up for review, India will just have a sock puppet say ‘look, you guys claim the yields are low, so we can’t sign until we deal with it.’ In that sense, ‘independent observers’ serve us a useful purpose.

  40. Pradeep E (History)

    “H-bombs are, in a word, hard, especially if you are trying to weaponize them or do anything creative (e.g. Livermore’s dud).

    No doubt and not addressing anyone in particular would like to comment that this is a central theme which confounds folks who for the lack of a better word, intentionally, would like to be confounded.

    The underlying tone and the declaratory triumph with which this whole series is announced lets us a read more into the attitude with which one is looking at India. Gee…we spent gazillions on doing that kind of stuff. How can it be bettered in any possible way that too with the cows and snake charmers being such distractions.

    I am sure one has heard about the anecdotal, pencil vs the ball-point pen developed for space use. An apt analogy to just point that if there’s money to soaked up, it will be soaked up.

    Too bad if the non-prol crowd cannot get data they would give a hand and a leg to get. BARC and the entire Indian weapons program operates just like that. Compartmentalized in all ways possible from the development to information dissemination. They do throw in the occasional music show, to add to the obfuscation quotient. Whats to say that what we see now is not just a part of that. But let that not stop us getting into a tizzy and talk about shitty science.

  41. Dr N K Srinivasan (History)

    The seismic data had been analysed in detail by western analysts with all their calibrations without the knowledge of depth of burial or fusion/fission ratio.This is a serious limitation,besides lack of knowledge about the geo-physical conditions at Pokhran..therefore their estimates are gross estimates with a margin of error of at least +/- 30% or worse….We have to leave it at that.If the western analysts are happy with their estimates, the estimate is good for them.But the Indian science establishment need not take them seriously at all,except for some one like Santhanam et al to quote it for their own arguments and for Indian press/media to play it up.