Homi Jehangir Bhabha, the scientist largely responsible for India’s atom bomb, was born in Bombay on October 30, 1909. He came from a Parsi family closely associated with the Tatas, one of the richest families in India. His father was a British-educated lawyer for the Tatas and his paternal aunt had married Sir Dorab Tata, the oldest son of the founder of the Tata industrial empire, Jamsetji N. Tata.
Bhabha grew up in an atmosphere of high culture and great privilege. In his aunt’s house could be found people like Nehru and Gandhi. He was educated in the best of the most expensive schools in Bombay. He showed great natural abilities in mathematics and he persuaded his uncle to finance studies in Cambridge. He was supposed to become an engineer, but at Cambridge he attended the lectures of Paul Dirac, one of the founders of the quantum theory, and decided to take his degree in physics. He did his Ph.D. with Ralph Fowler, who had been Dirac’s mentor. As a postdoctoral scholar he studied with the best scientists in Europe. During this time he did a calculation of the collisions of electrons with positrons—a process that bears his name and can be found in any textbook. When he was on vacation in India in 1939 the war broke out and Bhabha decided that he could not go back to England. This was a momentous choice, which led eventually to the creation of the Indian atomic bomb.
Zulfikar Ali Bhutto, the politician who organized Pakistan’s nuclear weapons program, was born on January 5, 1928, in Larkana, then part of British India but now in Pakistan. His father, Sir Shah Nawaz Bhutto, was a landowner in the Sindh. While not in the same financial league as the Tatas they were still very well-off. The family was Muslim and his father was an important political leader. Like Bhabha, Bhutto received his primary education in private schools in Bombay. Also like Bhabha, he left the Indian subcontinent to study abroad. He spent two years at the University of Southern California before transferring to Berkeley. He then went to Oxford to study law. He practiced law in Pakistan briefly before entering government. In 1957 he became the youngest member of the Pakistani delegation to the United Nations.
Six years later he became the foreign minister and angered the Americans by developing a close relationship with China. One of his friends was a nuclear engineer named Munir Ahmad Khan, who had worked extensively in the United States but took a position as a technical associate with the International Atomic Energy Agency in Vienna. This gave Khan access to classified reports and in 1965 he informed Bhutto that India was starting a serious program to build an atomic bomb. Bhutto reacted by saying, “Pakistan will fight for a thousand years. If India builds a bomb Pakistan will eat grass or leaves or even go hungry, but we will get one of our own. We have no other choice.” Munir Khan came back to Pakistan to lead the project that has by now constructed about a hundred such weapons, matching India’s supply. The two countries are like scorpions in a bottle. If one stings the other they will both die. A full-scale attack would reduce both countries to rubble.
While much has been written about the nuclear bombs of India and Pakistan, there is nothing like the collection of essays entitled Confronting the Bomb, by seven Indian and Pakistani scientists with an introduction by John Polanyi, a Nobel Laureate in chemistry. The collection has been edited by the Pakistani physicist Pervez Hoodbhoy. Born in Karachi in 1950, he went to school there and later became a junior colleague of the physicist Abdus Salam, who worked on the Pakistani bomb and is the only Pakistani to have won a Nobel Prize in any subject. Hoodbhoy took four science degrees from MIT and went on to join the faculty at the Quaid-e-Azam University in Islamabad. Apart from physics he is widely known for his courageous and outspoken struggle against Islamic extremism in Pakistan as well as his opposition to nuclear weapons.
The first essay in the book—“Scientists and India’s Nuclear Bomb”—is by the Indian physicist M.V. Ramana, who is currently at Princeton University. Among other things it gives a historical account of the Indian nuclear program.
Fission—the splitting of heavy nuclei like uranium by neutrons—was discovered in Germany at the end of 1938. The disintegrating atoms release more free neutrons, and these can in turn fission other nuclei of fissile isotopes, such as uranium-235 and plutonium-239. This can lead to a chain reaction. (Isotopes are variants of an element with different numbers of neutrons but the same number of protons. They have the same chemical properties but somewhat different masses.) Scientists throughout the world quickly saw that such a chain reaction would release a tremendous amount of energy and might be used not only to generate electricity, but also to create weapons far more destructive than any that had been built before.
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In 1948 the newly independent India passed an Atomic Energy Act and created a commission to supervise atomic energy. Bhabha was appointed chairman. In fact, Bhabha had already written to his uncle Dorab Tata’s trust in March 1944 to ask for money to begin a nuclear energy program and fund the Tata Institute of Fundamental Research in Bombay. This date is surprising, since it was over a year before the US set off its first nuclear explosions. What inspired Bhabha to make this request at that time? He envisioned a nuclear power program and believed that India should have a homegrown group of experts to run it. Did he know the details of the US program to make nuclear weapons, perhaps through his British contacts? Once the bombs were exploded in Japan, Bhabha’s intentions were clear.
I think of Bhabha as in some ways the Edward Teller of India. Teller—the Hungarian-American physicist whose work was essential to the development of the hydrogen bomb—was obsessed with the Soviet Union. Bhabha was obsessed with China. He thought that the only way to deter China was to have a nuclear arsenal and he was prepared to do anything to get one for India. He had support from Nehru, who tried to disguise the bomb program as a means of using nuclear power—including atomic explosions—for peaceful purposes. Teller also tried to persuade people that nuclear explosions were important for projects like dredging harbors.
On the average in fission something like two neutrons are produced. These neutrons can have different possible futures. The most likely is to bounce off the uranium nuclei. After a few such bounces they will either escape through the surface of the fuel element—for example, a bomb—or alternatively, cause another fission. (There is, as I will discuss later, a third possibility that leads to the manufacture of plutonium.) When the rate of escape exactly equals the rate of fission the fuel element is said to be “critical.” For a spherical fuel element such as a bomb there is then a critical radius and hence a critical volume. From the density one can find the critical mass of uranium or plutonium that makes up the fuel element. At precisely this mass there is no self-sustaining chain reaction. For this to happen one must create a supercritical mass in which the rate of fission exceeds the rate of escape.
There is a very important distinction to be made between isotopes like uranium-235, which are “fissile,” and isotopes like uranium-238, which are “fissionable.” The latter isotopes require a neutron energy above some threshold to produce fission, while the former can be fissioned by neutrons of any energy. The neutrons produced in a fission have a spectrum of energies and some are not energetic enough to fission uranium-238. Hence to make a chain reaction one needs to increase the amount of uranium-235 above the amount found in natural uranium. This enrichment is frequently done by using centrifuges. These are relatively easy to conceal compared, say, to a reactor. The first Chinese bomb used uranium but we did not know this until after the test. Most reactors require fuel that is at least 3 percent U-235, and weapons-grade uranium must be enriched to about 90 percent U-235.
In December 1953, President Eisenhower announced the Atoms for Peace program, which was intended to share peaceful nuclear research and technology with America’s allies and provided a large number of developing countries, including Iran and Pakistan, with their first reactors. One oddity of these reactors is that they were fueled by weapons-grade uranium, which was available at the time because a surplus of it was created by the US weapons program. No one thought that these countries would ever have the ability to make nuclear weapons—and the United States provided weapons-grade uranium to its Atoms for Peace clients until 1978. Many years earlier, President Truman had announced that the Russians would never have the ability to make a nuclear weapon. There is still some of this weapons-grade uranium in various countries and it needs to be watched carefully.
In August 1956, Indian scientists began operating a very small reactor at a new research facility in Trombay, known as the Atomic Energy Establishment. (It was renamed for Bhabha after his death in 1966.) This reactor burned 80 percent enriched uranium supplied by Britain. But a different path to a weapon—using plutonium instead of uranium as the fuel—was opened by a Canadian-designed reactor that first went critical in 1960.
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In a chain reaction, the neutrons emitted by fissioning nuclei must be slowed down by a moderator, such as water or graphite, in order to increase the probability of their fissioning the fissile isotope U-235. In the example of fission I gave earlier the moderator was light water. In the case of the Canadian reactor, the moderator was heavy water, in which ordinary hydrogen, a single proton, is replaced by a relatively rare isotope that also contains a neutron. Light water can capture neutrons, thus taking them out of the fission chain. Heavy water is less capable of doing this and is used in some reactors. What is crucial is that with a heavy water moderator one can use fuel with the low U-235 concentration found in natural uranium, which has a high concentration of U-238.
During the chain reaction of U-235, the U-238 that constitutes a significant portion of any reactor fuel is constantly being converted into U-239 by the absorption of neutrons. The nuclei of this new isotope are unstable; and through a process known as beta decay they become neptunium-239, yet another unstable isotope that in turn also undergoes beta decay, yielding plutonium-239, a fissile isotope that can power both reactors and weapons. Thus, by choosing a heavy water reactor that used natural uranium—which is 99.3 percent U-238—Bhabha and his colleagues maximized the amount of fissile plutonium that could be extracted from the byproducts of their supposedly peaceful energy program.
The Canadians were suspicious of the Indians’ intentions, but Bhabha refused to accept any kind of inspections. Reasoning that the Indians would get their reactors from somewhere, they decided that they need not lose the sale. Construction of the Indian heavy water reactor began in 1955 at Trombay. Some of the heavy water was supplied by the United States. Despite assurances that they would not pursue weapons, the Indians began extracting plutonium from the reactor using chemical procedures that they had also learned in the United States.
In 1962, there was a war between India and China over territory along their border in the Himalayas. Two years later, the Chinese tested their first bomb. After this, Bhabha claimed that India could produce a stockpile of fifty atomic weapons for as little as $21 million—or about $157 million in today’s dollars—a misleading extrapolation from American estimates of the cost of building a single device using proven designs and preexisting facilities. (Conservative estimates of the cost of the Indian weapons program to date are in the tens of billions of dollars.) Under the guise of a peaceful nuclear energy program, India designed a bomb and accumulated enough plutonium to set off its first test device in 1974.
In an essay entitled “Pakistan: Climbing the Nuclear Ladder,” Hoodbhoy gives an account of the history of nuclear weapons in Pakistan. I was a visiting Ford Foundation professor at the the University of Islamabad in the fall semester of 1969. I was taken to visit the first reactor to arrive in Pakistan. It was part of the Atoms for Peace program and had been built by the American Machine and Foundry Company. Abdus Salam had gone to the United States in 1965 as part of a small delegation that persuaded Edward Durrell Stone to design the campus of the Pakistan Institute of Nuclear Science and Technology. It looked more like a religious shrine than a nuclear facility.
The first Pakistani reactor had a small power output—about five megawatts as compared to the thousands of megawatts that an electricity-generating reactor produces. As with a number of other Atoms for Peace reactors, its fuel was weapons-grade enriched uranium, enriched to 93 percent. Due to the low proportion of U-238 in its fuel, this reactor was not optimal for making plutonium and the uranium enrichment route was chosen for the Pakistani nuclear weapons. The reactor was used to create isotopes for medical use and to train physicists. In 1991 the reactor was redesigned to operate with 20 percent enriched uranium, and it seems that some plutonium production now takes place on the site using the successors to this reactor. The enriched uranium still seems to be there, and there was a rather recent unsuccessful attempt by the US to take charge of it.
During my tenure in Islamabad, my host was one of Hoodbhoy’s predecessors, Riazuddin, who used only one name. His twin brother Fayyazuddin was also a professor. They struck me as wonderfully kind and unworldly. Invited to dinner at Riazuddin’s, I arrived to find myself and Fayyazuddin the only guests. Apart from serving the food, the women in the household disappeared. After the meal I was clearly expected to leave, which I did.
I was extremely surprised to learn that some years later Riazuddin headed the team of theoretical physicists that designed the first Pakistani atomic bomb. In December 1973 he accepted a fellowship at the University of Maryland and spent much time in the Library of Congress collecting all the unclassified material he could find on the design of a nuclear weapon. To make a nuclear explosion you must very rapidly create a highly supercritical mass in which the rate of fission increases exponentially. One way of doing this is to implode—squeeze down—a sphere of plutonium or uranium, thus increasing the density of the sphere, which lowers the critical mass.
Riazuddin found unclassified information about how to do this—including reports from Los Alamos on Robert Oppenheimer’s design for the first implosion device—in places like the Library of Congress. Thanks to the machinations of the Pakistani physicist A.Q. Khan—no relation to Munir—the group also got some details of the Chinese design. (The Chinese helped because of their conflict with India.) Riazuddin and his associates had already done the basic work on their implosion design, but the American and Chinese information helped them improve it. It appears as if the Chinese bomb that A.Q. Khan sold to the Libyans and very likely to the Iranians and probably traded to the North Koreans was for a Hiroshima-size nuclear weapon light enough to put on a missile.
A.Q. Khan also worked in the Netherlands from 1972 until 1975 for the Urenco Group, a commercial enriched uranium supplier, where he stole the plans for the advanced centrifuges used to produce the explosive fuel that could be used for Pakistani nuclear weapons. Khan soon established direct contact with Bhutto, who gave top priority to the creation of this facility. The Urenco design was later given to North Korea in exchange for missile technology and centrifuges based on it were found by IAEA inspectors in Libya and Iran. Although it has been denied it seems quite clear that Khan was in cahoots with the Pakistani government.
If Bhabha was the Edward Teller of the Indian program, one can make the case that Abdus Salam was his Pakistani counterpart. Having had personal dealings with both Salam and Teller, I have no doubt that Salam was the more agreeable of the two, He was born in 1926 in the Punjab in British India. His family was of the Ahmadiyya sect, which was later declared to be non-Muslim in the Pakistani constitution. He was a brilliant student and was headed for a career in the Indian Civil Service—the part devoted to railways. But for some reason this involved an eye examination, which Salam failed. He went on to study mathematics in the graduate school in Lahore and then won a scholarship to Cambridge. His Ph.D. thesis involved problems concerning infinities in quantum electrodynamics, which Freeman Dyson had left for others to solve.
He returned to Pakistan to teach but in 1957 he went to Imperial College in London. Salam was a great teacher and collaborator. He worked with Steven Weinberg on what is known as the Higgs mechanism for generating mass. Also, he did independent work on neutrinos; in 1979 he shared the Nobel Prize with Weinberg and Sheldon Glashow. Riazuddin was one of his students and Hoodbhoy also worked with him. In 1964 he founded the International Centre for Theoretical Physics in Trieste, which welcomed young physicists from developing countries. In 1972 he was called back to Pakistan by Bhutto to begin work on the bomb.
I do not know if Salam actually took part in the technical work that led to the bomb, but he did troll for unclassified literature and above all he recruited his students to work on the project. His old high school friend Munir Khan was appointed chairman of the Pakistan Atomic Energy Commission. I have heard that the money Bhutto raised to build a bomb came from Saudi Arabia and Libya, apparently on Pakistan International Airlines flights in bales filled with dollars. Thanks to A.Q. Khan, the Libyans got the Chinese design for a bomb and what might have amounted to a turnkey set of instructions to make one. But they still did not have the technical ability to produce a nuclear weapon.
On May 28, 1998, the Pakistanis exploded five atomic bombs underground. It took them many years to produce enough highly enriched uranium to do so. A massive centrifuge facility had to be built. There has been a claim that the Chinese actually tested a Pakistani bomb as early as 1990, but this is generally dismissed. Prime Minister Nawaz Sharif declared, “Today we have settled scores with India by detonating five nuclear devices of our own. We have paid them back.” By then both Salam and Bhutto had died. Salam’s remains were brought back to Pakistan from Oxford. He was buried next to his parents in an Ahmadiyya cemetery. His gravestone has now been defaced.
For many people, including myself, the most urgent question is the security of the Pakistan nuclear arsenal. This is addressed in another essay by Hoodbhoy, entitled “Post bin Laden: The Safety and Security of Pakistan’s Nuclear Arsenal.” Whatever one may think of General Pervez Musharraf, he made a serious attempt to take control of the Pakistani nuclear arsenal. In February 2000 he created something called the Strategic Plans Division, which has some 12,000 personnel and is in charge of the nuclear weapons. The problem with the security of all such entities in Pakistan is the presence of extremists.
Hoodbhoy gives an example. In 2003 Musharraf escaped two assassination attempts by military officers with extreme Muslim views. They were caught and some were sentenced to death. In May 2012 they all escaped from jail while the prison guards stood aside and displayed Taliban slogans. In Hoodbhoy’s view, there are in effect two Pakistani armies. One is devoted to defending the country’s borders and another is devoted to turning Pakistan into a country ruled by sharia law. The great concern is that this army will get hold of nuclear weapons. A relevant question is whether Pakistan has a system requiring that two or three separate officials give assent before a nuclear device can be launched. If this had been in effect in Doctor Strangelove, General Ripper would not have been able to launch his strike. Who in Pakistan has the authority to launch? Who in India or Israel for that matter?
That is, of course, part of the concern about Iran. Who, besides the Supreme Leader, could launch a bomb? From all the reports I have seen, no one outside the system knows where the Pakistani arsenal is maintained. Some of it, Hoodbhoy thinks, may be on unmarked trucks that move around cities. How can one be sure that all the drivers and guards can be trusted? Extremists respect martyrs. Could an entire city be cast as a martyr?
Reading Hoodbhoy’s book does not make for optimism about the future. Both India and Pakistan are building nuclear weapons and devoting large resources to doing so. India is apparently trying to make a hydrogen bomb and has already constructed nuclear submarines that carry missiles with nuclear warheads. The countries are so close to each other that any missile defense is impossible. Billions have been spent by the two countries, both of which have terrible problems with poverty.
The final destinies of Bhabha and Bhutto were quite different. On January 24, 1966, Air India flight 101, on which Bhabha was a passenger, crashed into Mont Blanc. Everyone on board was killed. Some conspiracy theorists believe the crash was part of a plot by the CIA to kill Bhabha before India got a bomb. Bhutto’s fate was no accident. He was arrested by the very repressive regime of General Muhammad Zia-ul-Haq and tried for treason before the Supreme Court of Pakistan in 1977. There was no evidence that he committed treason. His arrest was a purely political maneuver to get a political opponent out of the way. He was sentenced to death and hanged on April 4, 1979.
