Sunday, June 04, 2006

On the recent piece by Dr. Bharat Karnad

In ones' haste to present a meaningful summary of things, it is easy to make a remark that might be misinterpreted.

This recent article by Dr. Bharat Karnad suffers from some such likely sources of misinterpretation.

Most notably.

The ‘Shakti’ series of tests in 1998 proved only that the miniaturized 20 kiloton (KT) fission bomb design, first tested in 1974, is militarily serviceable.

Militarily serviceable - is a strange term. This term is generally used in the context of conventional arms to suggest that the weapon can can be put into military service or even serviced under battlefield conditions. The term cannot strictly be used with nuclear weapons until a "MET" (Military Effects Test) of the weapon is carried out. A MET also includes exposure of troops to the weapon.

All the other weapon designs – the boosted fission and, especially, the thermonuclear – due to their ‘simultaneous triggering’ in Pokhran, produced confused multi-test explosion data sufficient to conclude that the fusion design, for instance, did not work because of partial thermonuclear burn – authoritatively established by crater morphology and excessive traces of lithium in the rock and soil samples extracted from the L-shaped tunnel deep underneath the Thar desert where the devices exploded.

A Fusion-boosted-Fission device is commonly mistaken referred to as a full thermonuclear device and that causes a lot of confusion. A fusion-boosted fission device relies on a fusion reaction sparked with fast neutrons from a fission primary. The fusion reaction simply serves to convert the energy lost in the fast neutron flux into slow neutrons. This increases the efficiency of the fission reaction and enables you to get more bang for the same amount of fissionable material. The intention is never to start a full burn of the fusion reaction as this may release too much energy. A thermonuclear device seeks to most efficiently spark a fusion reaction. The efficiency of the device is not measured in terms of its ability to burn the primary fission core but in terms of the conversion of hydrogen to higher elements.

It is not advisable to use both these terms in the same sentence without qualifying either. A lay reader might confuse one for the other.

The Department of Atomic Energy has repeatedly clarified that no thermonuclear device was being tested in 1998, and that only an FBF assembly was tested. The department also clarified that the FBF yeild was about 40KT and could be scaled upto 150 Kt. The department never claims to have tested a full thermonuclear device. The department has also suggested that there is no question of testing a device exceeding a certain yeild at Pokhran due to constraints on the seismic activity.

Moreover, data from just one, and that too failed, test involving the decisive thermonuclear device is simply insufficient to write a software package simulating fusion reaction, leave alone help in developing new and more innovative designs for thermonuclear warheads/weapons of different power-to-yield ratios to fit varying missile nose-cone geometries.

It is sometimes possible to produce a scaled down version of a larger device to validate key design principles. Generally speaking a test validates the following:

1) The equation of state of the material - something that tells you how the material compresses as a function of the energy released in the conversion of mass.

2) The scattering cross-sections - something that tells you the probability of a particular nuclear reaction occurs. This is something that has to be determined experimentally especially as the reactions depend on the momentum of the incident particles.

3) The reliability of the electronic fuzing systems.

All these things help design and improve computer simulations.

There is some debate on what constitutes sufficient information for simulations. It is highly improper to make a substantive statement about this.

It is incorrect to say that a failed test did not supply data useful for simulation. As long as you have an idea of what elements were produced in the nuclear reaction - there is sufficient information to make the necessary changes to the design. I can very easily term a "sub-critical" test as a "failed critical test" - that doesn't mean that the information collected in a "sub-critical" test is not useful.

I have never heard the term "power-to-yield" ratio. This is most likely a typo in the article, the concern in building warhead is "weight-to-yeild" i.e. warhead weight to warhead yeild. I have no comments on what constitutes sufficent weight to yield in an Indian nuclear warhead. I have nothing to say about missile nose cone geometries.

The article also says

Additionally, Garwin’s suggestion that the nuclear civilian energy sector worldwide be enlarged under strict IAEA supervision, is even more directly fulfilled by the India-US deal with the offer of enriched uranium-fueled 1000 MW light water reactors (LWRs) from the US (Westinghouse 1000), France (Areva) and Russia (VVER 1000) operating in a closed fuel loop, meaning, exhausted fuel bundles will be replaced periodically from international fuel fabrication centres. Should India import these LWRs with installed thermal capacity of 35,000 MW, it will expend some $50 billion, resulting in handing Washington a powerful lever to get Indian compliance with US demands in the nuclear policy realm as well as outside of it. Assuming the loss of $50 billion is absorbable by a burgeoning Indian economy, India may have to contend with the cut-off of contracted fuel, the shutdown of the imported LWRs, and the loss of 35,000 MW in the grid which could prove economically ruinous for the country.

This agrees almost completely with what I had said earlier about the third path which must be taken in the conduct of this deal. I only wish to add that Richard Garwin is one of the high priests of the non-proliferation community. His views on the nature of a global nuclear energy initiative are understandable and in my opinion irrelevant. The reality of global energy use that we are heading for is far in excess of Richard Garwin's ability to comprehend. I mean for God's sake it took 50 years for Garwin to comprehend the utility of a breeder reactor.

6 Comments:

At 5:03 AM, Blogger interestedonlooker said...

Maverick,

Karnad has mis-quoted Lithium for Tritium, apparently, in claiming that the S-II boosted fission devices did not burn fully.

 
At 5:57 AM, Blogger maverick said...

interestedonlooker,

I think Bharat Karnad may just be speaking in a confusing way. I believe his heart is in the right place.

He isn't the only one who wants a bigger bang for the buck. There are limitations at Pokhran which will have to be overcome before doing much else.

In terms of simulations - there are largely two things that can be simulated - firstly you can simulate how the particles are transported through the assembly and then secondly you have to simulate how the compression from the explosion travels through the assembly. Meshing the two things together sounds like a very complicated business - I mean you have to account for how the density changes from the explosion affect the scattering of the radioactive particles and how the release in energy from the nuclear reactions affects the density.

 
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At 12:43 AM, Blogger sudeep said...

>> The Department of Atomic Energy has repeatedly clarified that no thermonuclear device was being tested in 1998, and that only an FBF assembly was tested.

Hmm.. I dont remember hearing that ever,.. I do remember the May 13th press conf. by Vajapayee where me clarified that we tested a 'hydrogen weapon'/thermo-nuclear device.

 

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