Last changed 30 March 2001
Late in 1967 the scientific leadership at BARC led by Homi Sethna and Raja Ramanna undertook a new effort to develop nuclear explosives, one that was larger and more intense than any previous efforts. One that would lead to the successful design of a nuclear device, a device that India would successfully test.
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It is not completely clear why they decided to revive the effort and move forward at that time, but due to the convergence of a number of trends perhaps the time simply seemed ripe. China had just exploded a thermonuclear device in 1967, and had become very belligerent - moving troops into disputed areas and making threats. And India's supply of separated plutonium, necessary for anything beyond purely theoretical work, was slowly accumulating. Some researchers (like Perkovich) have concluded that the new effort was begun at the initiative of the scientists involved. Chengappa however states that Gandhi directly approved the new effort at the urging of her new secretary Parmeshwar Narain Haksar [Chengappa 2000, pg. 112], and that she specifically told Vikram Sarabhai, chairman of the IAEC, not to interfere. In any case Sarabhai did not try to stop this work when he became aware of it and appears by the spring of 1969 to have become at least a moderate supporter of the program.
That fall Rajagopala Chidambaram - then a researcher in molecular biology at BARC - was recruited by Raja Ramanna to investigate the equation of state of plutonium (how its density varies with temperature and pressure) - knowledge essential for designing an implosion bomb. Chidambaram would later become the chairman of the IAEC, and head of India's nuclear weapons program leading up to the 1998 test series.
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Other key researcher's who became involved in the project in 1967-68 include P.K. Iyengar, Ramanna's deputy, and Satinder Kumar Sikka, who would lead the development of India's hydrogen bomb in the 90s. The team would eventually grow to between fifty and seventy five scientists.
India's nuclear weapons program moved in to full swing with Raja Ramanna at the helm. As Ramanna admitted in an interview on 10 October 1997, the "Peaceful Nuclear Explosive" (PNE) program - implying an intention to develop the nuclear explosives for civilian engineering work - was simply a cover for a program aimed from the beginning to develop a weapons capability, in truth there was little if any interest in Plowshare type peaceful applications. On the other hand, there was also no involvement of the military in the development program. There was no attempt to devise a military role for the nuclear explosive, or to seek the military's input for requirements. The military's public statements on nuclear weapons at this time were far from enthusiastic - essentially mirroring Sarabhai's views - so the advocates of nuclear weapons development had little incentive to seek their collaboration.
Even with the peaceful cover story, India found it necessary to keep as a low a profile on the project as possible to avoid inevitable attempts by other nations to obstruct it by denying access to nuclear technology and knowledge.
During December 1968 - January 1969 P.K. Iyengar visited the Soviet Union with three colleagues and toured the nuclear research facilities at Dubna. He was very impressed by the plutonium fueled pulsed fast reactor he saw there. This type of reactor is an unmoderated fast neutron reactor, that is allowed to go prompt supercritical to produce an intense very short pulse of neutrons. These are all characteristics of the cores of fission bombs, the principal difference between them being that in pulsed reactors the degree of supercriticality is very slight and ordinary thermal expansion of the reactor core is sufficient to shut down the reaction, while in fission bombs the degree is very large and the core cannot expand fast enough to shut down the reaction until vast amounts of energy are released. Pulsed fast reactors provide an excellent laboratory model of fission bomb behavior, having been used for that purpose during the Manhattan Project (the famous Dragon experiments) and afterward (the Godiva, Popsy and Topsy reactors).
Recognizing this, Iyengar set about developing just such a reactor for India. The scientific leadership approved the plan in January 1969, the kick-off meeting for this reactor, called Purnima (an approximate acronym for Plutonium Reactor for Neutron Investigation in Multiplying Assemblies), took place in March 1969. Attending this meeting was Iyengar, Ramanna, Homi Sethna, and Sarabhai. Sarabhai's presence clearly indicates that with or without formal approval, the work at BARC toward weapon design now had Sarabhai's support. Chengappa indicates in fact that Sarabhai approved a one million rupee budget for Purnima (about $125,000, a figure could have covered only incidental costs - not the value of the plutonium).
Purnima was designed to use a hexagonal core of 177 stainless steel pencil shaped rods containing 18 kg of plutonium as 21.6 kg of plutonium oxide pellets (enough for three Fat Man type bombs) with a nominal average power of 1 watt. Mahadeva Srinivasan developed a sophisticated physics model for criticality calculations in 1970, and later became the reactor's chief physicist. Construction began that year when sufficient separated plutonium finally became available. Purnima went critical on 18 May 1972. With Purnima as a test bed the Indian physicists were able to refine their understanding of the physics of fast fission and fast neutrons. While not formally part of the later bomb development team Srinivasan's expertise in fast critical systems underlay the nuclear design of the device.
1970 saw expansion of the nuclear weapons program in many ways. Due to the requirements of Purnima the program needed to develop facilities and experience in handling large amounts of plutonium (developed under the supervision of P.R. Roy), and work also began on fabricating plutonium metal alloys for the eventual construction of the bomb core. To advance the development of the essential implosion system V.S. Ramamurthy also began performing numerical implosion simulations on an antiquated Soviet Besm 6 computer
Development of the technology for implosion got underway in April 1970 when Ramanna sent Pranab Rebatiranjan Dastidar, the electronics expert at BARC, to Waman Dattatreya Patwardhan at the Explosive Research and Development laboratory (ERDL) at Pune to begin work on the detonation system for the bomb. Patwardhan was well known to the BARC scientists, since he helped them with the explosives tests years before as part of SNEPP. In July nuclear physicist Dr. Basanti Dulal Nag Chaudhuri took over as science adviser to the Defense Minister, and as Director of the Defense Research and Development Organization (DRDO). The following month, he and Ramanna began working together to recruit the Terminal Ballistics Research Laboratory (TBRL), located in Chandigarh, to develop the explosive lenses for the implosion system.
During 1971 work on weapon design continued. Srinivasan working with K. Subba Rao developed models of the fission process on a nuclear bomb, and equations to predict its efficiency. Chidamabaram completed his work on the plutonium equation of state, and Ramamurthy developed computational models of the implosion, nuclear reaction, and disassembly process to predict the devices behavior. Throughout this period Ramanna and his lieutenant, P.K. Iyengar, held frequest reviews of the projects progress.
In April 1971 Nag Chaudhuri appointed Nagapattinam Sambasiva Venkatesan to Director of TBRL with specific instructions to assist in developing the nuclear device.
The 1971 Indo-Pakistani War influenced India's resolve to test a nuclear device, but in a curious and indirect way. This war developed when the bi-regional state of Pakistan, split into East and West Pakistan on either side of India, held its first national election in December 1970. The dominant party of the more populous East Pakistan won a majority of the seats in parliament, but West Pakistan, accustomed to monopolizing political and military power, responded by ignoring the election result. And on 25 March 1971 West Pakistan forces arrested the winner Mujibur Rahman, and launched a campaign brutal military repression on the Bengalis of East Pakistan. This resulted in tens of millions of refugees spilling into India, some of whom took up arms against the Pakistani government. By autumn the Indian-East Pakistani border had become something close to a combat zone, with India and Pakistan trading intense firing across the border, while armed rebels operated from safe havens in India. In late November PM Gandhi authorized Indian forces to cross the border to "pursue" Pakistani forces. Pakistan responded by a massive strike against Indian airbases in western India on 3 December, and declaring war on 4 December. India had spent months preparing for this escalation, indeed had deliberately provoked it, and launched an overwhelming 3-pronged attack into East Pakistan. Unable to hold back the Indian invasion, Pakistan attempted to counter with an attack in Kashmir, gaining several miles of territory before being halted by Indian forces. The Indian army on the other hand had surrounded Dacca, the capital of East Pakistan by 15 December, and its garrison surrendered the next day. On 17 December a cease-fire was accepted by both sides, effectively ending the war.
The war had been a crushing defeat for Pakistan, which had lost more than half its population. As the crisis developed throughout 1971 China and Pakistan had grown closer to the U.S. while India had grown closer to the Soviet Union. The keystone of the Nixon administration's foreign policy had been its reapproachment with China (announced 15 July), to place the Soviet Union between the pincers of two major opposing powers. Pakistan had played a critical role in facilitating secret negotiations with China. India had at the same time strengthened its ties to the U.S.S.R. culminating in a formal treaty of friendship on 9 August. Chinese support for Pakistan during the most extreme crisis of Pakistan's existence came to nought however. China failed to provide any significant assistance for Pakistan, such as applying pressure on India's border. The net result was that Pakistan suffered both a serious military defeat, demonstrating its inferiority to India in military terms, and a permanent irreparable loss in its strategic position by the new found independence of East Pakistan. And the much feared Pakistan-China axis had turned out to be a "paper tiger".
Unsurprisingly this did bolster India's sense of security, but it did not stem the momentum toward the testing of a nuclear device as one might have supposed.
On 30 December 1971 Sarabhai died, and Homi Sethna - already head of BARC - took his place as chairman of the IAEC. Thus the only prominent voice in Indian government counciling restraint in pursuing the nuclear option was replaced by one of its most ardent advocates.
And the hostile attitude taken toward India by the U.S. during the crisis had along lasting effect on Indian attitudes. Pres. Nixon and Sec. of State Kissinger chose to view India's actions as hostilities aimed at a U.S. ally and thus as an act hostile to the United States, rather than a case of a western-style democracy coming to the defense of a people being brutally persecuted by a military dictatorship for attempting to exercise its democratic rights. The U.S. even went so far as to dispatch an aircraft carrier battle group to the Indian Ocean in an ill-conceived, obscurely reasoned, and ineffectual attempt to pressure India. The feeling that a superpower had attempted to coerce India in affairs affecting India's vital interests became a cause celebre for advocates of the nuclear option (although they never clearly explained how a limited nuclear capability would counter U.S. pressure).
Bhabhani Sen Gupta ably described the shift in India's views toward the nuclear option in the wake of the 1971 war:
The Chinese bomb ceased to be the main argument for the Indian bomb, perhaps becasue of the Chinese inability to help Pakistan in the 1971 war and also becasue of the initiatives taken by India to normalize relations with China. The arguments for the bomb now were that without it India could not expect to be admitted to the corridors of global power, nor enjoy the status of the dominant regional power; that the bomb might quicken the process of normalizing relations with China; that it would proclaim India's independence of the Soviet Union and compel the United States to change its attitude of hostility or benign neglect.[Gupta 1983; pg. 4].
By the beginning of 1972 the basic design for India's first nuclear device was complete, and other parts of the program for developing the necessary expertise to implement the design were coming along. During that year the data from operating Purnima (starting in May) began flowing in allowing confirmation and refinement of the device's nuclear design; and the work in plutonium metallurgy reached the point where the device could be successfully fabricated.
The decision to go ahead and manufacture the device and prepare for a test was made later in the year, while Indira Gandhi was still near the peak of her post-war popularity. Early in the year PM Gandhi had seemed ambivalent about the wisdom of conducting an actual test. But by this time the internal momentum of the nuclear development program, the now well established popularity of the nuclear option among India's literate urban elite, the lack of any significant restraining counsel, and Gandhi's sense of strength all seem to have combined to make the decision one of when, not if, the test would come. The decision to move forward was made by PM Gandhi on 7 September 1972, a day in which she toured BARC on the occasion of the tenth convocation of the Indian Institute of Technology at Bombay. During this tour she was shown a wooden model of the device. Upon seeing the model she gave the scientists present verbal authorization to construct it and prepare for testing, but not to test it without explicit approval from herself.
One change made by Sethna soon after assuming the chairmanship was to split the Indian space program, then part of the Department of Atomic Energy, into a separate agency - observing quite reasonably that to have the DAE developing both nuclear explosives and missile technology would wave a red flag for observers concerned about proliferation, no matter what claims were made about the peaceful intent of both programs.