The H-bomb issue is crucial

Questions have arisen about the authenticity of the Indian nuclear establishment's claim that a true hydrogen bomb was exploded as part of the Pokhran-II series of tests on May 11.

BUDDHI KOTA SUBBA RAO

THE success claimed in India's first hydrogen bomb test is suspect. The H-bomb success is crucial to afford India a larger role in global power play. The technical debate over the claim of Indian nuclear scientists and seismologists on India's first thermonuclear device (H-bomb) has raised questions about whether it was a deliberately made false claim or a claim made without understanding why it failed.

Immediately after the three nuclear explosions at 3-45 p.m. on May 11 at Pokhran, Prime Minister A.B. Vajpayee announced that "the tests were conducted with a fission device, a low-yield device and a thermonuclear device. The measured yields are in line with expected values." The words "expected values" are significant. The yield values of the three nuclear devices were withheld from the nation for reasons unknown. In common parlance, a fission device is a fission bomb which is also called an atom bomb; a low-yield device is a device which gives firepower equal to conventional chemical high explosives; and a thermonuclear device is a hydrogen bomb, technically known as a fusion bomb. A hydrogen bomb has vast destructive power compared with an atom bomb. What are the differences between a fission bomb and a fusion bomb and what are their basic working principles?

A FISSION bomb is made by fissioning or splitting the atom whereas a hydrogen bomb is made by fusing atoms. A fission bomb before ignition consists of a mass of fissile material (Uranium-235 or Plutonium-239) and surrounding tamper (Beryllium oxide or other reflector of neutrons). The surrounding tamper is intended ultimately to improve the neutron multiplication factor, denoted usually as 'k'.

Much of the ingenuity in a fission bomb lies in correctly calculating the value of the multiplication factor 'k'. The fissile material and the surrounding tamper material are first placed in a geometric form which allows leakage of neutrons and results in 'k' being less than one in numerical value. These materials are suddenly assembled by chemical high explosives or by other means into a more compact and less leaking geometry where 'k' substantially exceeds the numerical value of one. At the same time, the neutrons from spontaneous fission start an explosive divergent chain reaction. The rate of energy release grows exponentially to result in a fission bomb. The rate of reaction tapers off with the depletion of the fissile material.

SHANKER CHAKRAVARTY
At the Shakti-1 test site at Pokhran on May 20. The nuclear establishment's claims in respect of the yield value from the detonations on May 11 have raised questions about the nature of the device tested.

In a highly efficient fission device, a total mass of one kilogram of heavy nuclei (Uranium-235 or Plutonium-239) undergoes fission for each 17 kilotons of energy release. But in a less efficient device, 'k' is reduced below unity, primarily through the explosive disassembly of the compact geometry.

The hydrogen bomb uses the nuclear properties of deuterium and tritium (the two isotopes of hydrogen) to set up an uncontrolled, self-sustaining, thermonuclear fusion reaction, as opposed to the fission bomb in which uranium or plutonium is the principal explosive. The hydrogen bomb is thus a fusion bomb that fuses hydrogen to become helium. In a fusion reaction, the collision of two energy-rich nuclei results in a natural rearrangement of their protons and neutrons to produce two or more reaction products, together with a release of energy of an amount E given by Albert Einstein's formula E = mc2 (mass is denoted by 'm' and velocity of light by 'c'). For a hydrogen bomb reaction to become self-sustaining, a so-called critical temperature of very high magnitude (about 35 million degrees Kelvin; zero degree Kelvin is equal to minus 273 degrees Celsius must be attained; the explosion of a fission bomb generates temperatures of that magnitude.

Thus a hydrogen bomb (fusion bomb) needs a fission bomb (atom bomb) as a trigger. Once the high temperature is achieved with the help of a fission trigger, the energy release in the initial fusion reactions maintains the temperature, and the chain proceeds either until the supply of fusionable material is exhausted, or until sufficient expansion has taken place that the fusion material is cooled below the critical temperature to stop the thermonuclear fusion.

ON what basis have doubts been raised on the claimed success of India's first thermonuclear device detonated on May 11, 1998? It is on the basis of the yield value from the detonation.

The power and the consequent success of a nuclear explosion is measured from the yield which results from the explosion. The yield or total energy of a thermonuclear device, is expressed in megatons (one megaton is 1,000 kilotons and one kiloton is 1,000 tons of equivalent chemical high explosive). Submarine-launched Polaris missile warheads have a yield of about one megaton. The first publicised thermonuclear test was in the United States in 1951 and it was more like boosted fission.

The term 'boosted fission' is used because the core of a small atom bomb (fission bomb) is filled with hydrogen fuel and when the atom bomb is detonated the radiation from the exploding atom bomb is focussed for a split second on to the hydrogen fuel. The hydrogen fuel then fuses to cause a fusion reaction to raise the power of an atom bomb by as much as 10 times its original value of yield; a true hydrogen bomb, on the other hand, may be hundreds or even thousands of times as strong.

Stanislaw Ulam and Edward Teller were the fathers of the hydrogen bomb developed in the U.S. The first true hydrogen bomb detonated by the U.S. in 1952 was about 700 times more powerful than the atom bomb (of about 14.5 kilotons yield) dropped on Hiroshima. The former Soviet Union detonated its first hydrogen bomb in 1953. In October 1961, in its Arctic test site the Soviet Union exploded a 58-megaton hydrogen bomb; its father was Andrei Sakharov. The yield of that hydrogen bomb was 4,000 times more than that of the bomb dropped on Hiroshima. It was at that time the most powerful hydrogen bomb ever tested, and it used the same principle which produces nuclear reactions inside stars, including the sun. In subsequent years, however, yields of energetic fusion bombs in excess of 100 megatons were reported.

The United Kingdom exploded its first hydrogen bomb in 1957, followed by France in the early 1960s. China conducted its first hydrogen bomb test on June 17, 1967. Quite early on, China was able to explode a hydrogen bomb with a yield of six megatons.

THE story of the first Indian hydrogen bomb test is a mystery. On May 11, Indian nuclear scientists were silent on the yield from their first hydrogen bomb test, one of the three nuclear devices detonated that day. All one could go by were Prime Minister Vajpayee's words: "The measured yields are in line with the expected values."

The global network of seismometers that monitors the earth for shock waves from earthquakes and atomic blasts had picked up signals which showed that the yield on May 11 from the triple nuclear explosion was between 10 and 25 kilotons. Therefore, it appeared to experts that the first purported Indian hydrogen bomb test was a test not of a true hydrogen bomb but at best of a boosted fission device. Gregory E. Van der Vink, director of planning at the Incorporated Research Institution for Seismology, who advises the U.S. Congress and the Clinton administration, has been reported as saying: "From Monday's test (May 11, 1998) we have a seismic signal of about 5.4. We think this corresponds roughly to an explosive yield of about 10 to 25 kilotons." More or less the same yield was estimated by Japanese and British scientists. But surprisingly, Indian seismologists announced that the yield from the first Indian hydrogen bomb test was about 50 kilotons. This added to the mystery. Experts from other countries openly criticised Indian nuclear scientists and seismologists for exaggerating the yield value of the first Indian hydrogen bomb test.

The waves of hysterical joy whipped up by supporters of the Bharatiya Janata Party, describing the triple nuclear explosion a "spectacular success", contrasted with the doubts expressed by the international scientific community. This obliged the Chairman of the Atomic Energy Commission (AEC), Dr. R. Chidambaram, who is hailed as the father of India's hydrogen bomb, to address the doubts at a May 17 press conference in New Delhi along with A.P.J. Abdul Kalam, Scientific Adviser to the Defence Minister. The press conference looked like a damage control exercise. Chidambaram's attempts at the press conference to dispel the doubts on India's success spawned more doubts and questions.

Chidambaram claimed that from the three nuclear explosions, the item-by-item yield was: from the fission device 15 kilotons; from the low-yield device 0.2 kilotons; and from the thermonuclear device (comprising a fission trigger and a fusion device) 12 kilotons from the fission trigger and 45 kilotons from the fusion device. Chidambaram added that the two sub-kiloton devices exploded on May 13 gave 0.5 kilotons and 0.3 kilotons respectively.

How far was the head of India's nuclear energy establishment able to dispel the doubts? According to him, the reason for the low values recorded by international seismic sensors was the simultaneous triggering of the three devices on May 11. He meant that the simultaneous explosions resulted in interference of shock waves travelling through the earth, which in turn led to a low recording of seismic data on the global network of seismic sensors. But how is it that the shock waves had no interference at the seismic sensors located in various parts of India, such as the one in Karnataka and the one at the Bhabha Atomic Research Centre (BARC), Trombay? How can the shock waves have travelled correctly towards the Indian seismic sensors and in a different manner towards the global network of seismic sensors? Even the seismic sensor in Pakistan, about 437 km from Pokhran, recorded a low seismic value.

Chidambaram's explanation was unscientific in another respect. At the press conference, he revealed that the two shafts, one of which contained the fission device and the other the thermonuclear device, were only 1 km apart. In such a close configuration, given the simultaneous detonation of the two nuclear devices, the epicentre from which the shock waves travel will be more like from one location, and the possibility of interference of shock waves is practically nil.

If two stones thrown into a pond of still water fall simultaneously into the water an inch apart from each other, the ripples will be as if only one stone was thrown into the pond. The simultaneous detonation of two nuclear devices at a distance of 1 km, likewise, would show that there was no scope for any shock wave interference of practical value. Thus it is clear that Chidambaram, in his attempts to dispel the doubts on India's first hydrogen bomb test, used scientific jargon and came out with unscientific statements.

ABDUL KALAM, who spoke at the press conference on May 17, claimed that the nuclear tests conferred on the country "a capability to vacate nuclear threats". His remark only ended up vacating the boundary between a political statement and a scientific statement. A political statement can mean many things, but a scientific statement has only one meaning. That is the characteristic of science. Both Chidambaram and Kalam appear to have ignored this.

When a launch by the Department of Space fails, the failure is not hidden from the public. But the Department of Atomic Energy, under the veil of secrecy, is privileged to hide its failures and also to paint failures as grand successes. Such a privilege, it appears, is fully exercised in respect of India's first hydrogen bomb test. It looks like a major S&T scam.

Referring to the yield values of the five nuclear explosions by India on May 11 and 13, Ray Kidder, a former bomb designer at the Lawrence Livermore National Laboratory, in California, said: "Maybe they tried and failed." Also, Herbert York, a former arms designer and director of the Pentagon's research who once directed the Livermore Laboratory, said very small blasts made little or no sense. He added: "It is a funny thing to do at this stage" of India's atomic evolution.

There are two possibilities that fit the facts. The first is that the scientists at the DAE informed Vajpayee of the true state of the tests but the Prime Minister chose to hide the failure of the hydrogen bomb test. Alternatively, the scientists misled the Prime Minister into believing that the tests, including the hydrogen bomb test, were a grand success. Only a debate in Parliament followed by an inquiry by a Joint Committee of Parliament can resolve this issue. There should be an informed debate in Parliament on the White Paper promised by the Government on the subject.

The irony is not in making the Buddha smile a second time over the experimentation of mass destructive nuclear power in the very land of the peace-loving Buddha. The striking irony is that an utter failure of India's first thermonuclear explosion could be sold to Indians as a "spectacular success".

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