Homi Bhabha

from 'Icons from the world of science', by S.Ananthanarayanan - home page

In 1947, when India became independent, science and technology were things that belonged to another world. India was largely underdeveloped and rural, the little technology that one could see was imported, and one had to go abroad for higher education. That India, today, has risen to become a nation with a vigorous nuclear power programme and research institutes that rival the best in the world is testimony to the rare ability and vision substantially of one man.

Homi Jehangir Bhabha combined the skills of a first rate scientist with the capacity to dream and then translate dreams to reality. In nineteen short years, from 1947 to 1966, Bhabha established the Tata Institute of Fundamental Research in Mumbai, the research centre at Trombay, now known as the Bhabha Atomic Research Centre, the Centre for Advanced Research in Chennai, and the Centre for Advanced Technology at Indore. And he laid the solid foundation of a gamut of activities within the nuclear programme, from prospecting for nuclear ores to feeding electricity from fully operational nuclear power plants to the national grid.

HJ Bhabha was born in 1909 in a Parsi family of great culture and learning. He was brought up in Mumbai and educated in the European tradition, in the arts and in music, as well as in the sciences. Bhabha displayed early interest in science. By the time he was sixteen, he had studied the Special Theory of Relativity, then barely familiar even to the well educated. After school he continued at the Elphinstone College and then the Royal Institute of Science, both of which were in Mumbai. At eighteen, Bhabha left for England and joined Gonville and Caius College at Cambridge. Bhabha took his Tripos, first in Mechanical Engineering at his father’s wish, and then in Mathematics, in 1932, according to his own.

For the next seven years, while he completed his Ph.D, Bhabha had a series of fellowships, which enabled him to work with the leading physicists of the time, including Pauli and Fermi, and at the best institutes, like the Bohr Institute at Copenhagen

In 1939, Bhabha returned to India for a short break, but World War II broke out before he returned. In England, many scientists joined the war effort and basic research was not the priority. Bhabha decided to stay in India and accepted a readership at the Indian Institute of Science, Bangalore. With the help of a small grant from a Tata trust, Bhabha set up a unit to work on cosmic rays.

Bhabha had got interested in cosmic rays while at Cambridge and he ploughed into the field with enthusiasm. Cosmic rays were a mysterious radiation that seemed to come from outer space and got absorbed, to a great extent, by interaction with the upper atmosphere. It was later discovered that these were largely protons, or the positively charged particles in the nuclei of atoms, produced probably by stars and in supernova explosions. These particles interacted with atoms in the atmosphere and gave rise to ‘secondaries’ that consisted of a variety of elementary particles.

Another device for detecting cosmic rays was the ‘cloud chamber’. This was a container which would show tracks of charged particles, rather like the vapour trails that jet aircraft produce in the sky. The cloud chamber allowed the tracks to be photographed and also revealed outcome of the products of a collision, when one occurred within the chamber. As the particles were charged, they curved and deflected in magnetic and electric fields. Having such fields enabled identification of the charge on the particles by seeing which way they curved.

Bhabha soon created a formidable research facility at IISC, using innovation and improvisation where funds or equipment were wanting. But by 1944, he felt the need for a larger facility and approached the Tata trusts again. As the war appeared to be reaching an end, there was the possibility of returning to the West, but, as he wrote in a letter to JRD Tata in 1943, he could continue to stay in the country and see if suitable conditions could be created, of “doing one’s duty to one’s country and building up schools comparable with those in other lands.”

The Sir Dorab Tata Trust responded to Bhabha’s proposal and the Tata Institute of Fundamental Research was born in Bangalore in 1945. A few months later, the Institute was shifted to Mumbai, working out of a building in downtown Mumbai, the property of an aunt of Bhabha himself.

Talented persons gravitated to TIFR and Bhabha soon had a powerful team at work. By 1949, the premises grew cramped and they moved to a picturesque building near the Gateway of India. The work was in cosmic rays and soon in Mathematics too. International conferences were held and the world’s leading scientists were regular visitors. In a few years these premises again got crowded and in 1962 the Institute moved to its present location, at the southern tip of the Mumbai island.

The Institute is now a vigorous centre of committed research in a variety of frontier areas in Physics and Mathematics. It has facilities for experimental work, including those in the hill resort of Pachmarhi in Madhya Pradesh and in the gold mines at Kolar in Karnataka. A sizeable branch is at Bangalore, dedicated to research in the biological sciences

The tradition of order, organization, commitment and dedication that Bhabha inculcated into TIFR during the time he guided its affairs has survived and today, the Institute is a signpost for others to follow. The work done is of the highest order and its colloquia and seminars attract the best in the world.

A great development of the times when Bhabha started work in India, following Einstein’s celebrated E=mc2 (E is the energy, m is the mass and c is the speed of light), or the equivalence of mass and energy, and discoveries about the nuclei of atoms, was the possibility of harnessing immense energy from the splitting of atomic nuclei

The nuclei of atoms consist of positively charged protons and about the same number of electrically neutral neutrons. The act of holding together a number of such particles takes energy and it is found that the total mass of such a nucleus is a wee bit less than the total of the mass of each of the constituents – the difference being the mass which is equivalent to the binding energy. Now, in some heavier nuclei, it is found that the nucleus could be more economically packed as two smaller nuclei. Economical, that is, in the use of binding energy. If the nucleus could be split into these smaller parts, the saving in binding energy would be released. And this energy could be used to set off an explosion, or to drive a turbine in a power plant!

It is like having a pair of golf balls in a golf hole at the top of a mound. The golf balls together are in a higher energy state than when separate, on the fairway. If the balls were pushed out of the hole, using a little energy, they would roll down the slope and release a good deal more energy!

Uranium, which is about the heaviest of natural elements, has two forms of its nucleus. Both forms have 92 protons, but either 143 or 145 neutrons. As it is the protons that decide the chemical properties of an element, both forms are uranium. But the different numbers of neutrons make for slightly different ‘packaging economies’. These forms are called U235 and U238, the subscripts being the total number of particles in the nucleus, and these forms are central to the design of nuclear reactors.

Both forms of uranium are found to split up, or ‘fission’ either naturally or on being struck by a stray neutron. The natural fission is very slow, but in both cases, there is release of huge energy. The energy released by fission of one gram of uranium, for instance, is about a million times the heat obtained from burning a gram of coal, more like burning a tonne of coal! But it is the specific way that U235 breaks up, when struck by a neutron, that makes possible the nuclear ‘chain reaction’.

The way U235 breaks up can be shown like this:

In both the reactions, the products are the ‘daughter’ nuclei, plus three or two leftover neutrons. That a reaction induced by a neutron results in neutrons again has an important consequence. If just one nucleus in a mass of uranium were struck by a chance neutron, this would produce more neutrons, which, in their turn, would induce more fissions, and so on! In a fraction of a second, all the nuclei would fission and, KABOOM!

There is, of course, a threshold quantity of uranium, so that the ‘daughter’ neutrons do not get wasted and the chain is kept going. In pure uranium, which has only 0.6 per cent of U>235, this quantity is about ninety kg. But even much smaller quantities get unbearably hot and give off radiation.

Apart from this ominous scope for destruction obtained by plunging quantities of fissile material together, Enrico Fermi had also discovered the possibility of a controlled fission reaction, which could be used to generate power. In this method, portions of the fuel are not allowed to come close enough for a runaway reaction, but are kept separated by shields of lead or graphite, which absorb neutrons and slow things down. The result is only generation of heat, which could be siphoned off by a circulating coolant and used for driving turbines.

Bhabha saw at once the promise of atomic power to fuel the development of free India. It was audacious to think that a country without enough to eat and barely able to produce cement and steel for basic civil construction should dream of harnessing newborn technology as a short cut to industry and growth. But Bhabha was a visionary and his comprehension of science and its relation with life went beyond the academic.

This was the year 1947. The war was hardly over, Independence was at hand and a regular government was yet to be formed. Bhabha did not think it proper to wait. He convinced Pandit Nehru, then leader of the interim government, that despite all the political and economic priorities of a country newly free, development of atomic energy capability could not afford to be delayed. In the months that followed formal Independence and even during the turmoil of Partition, Bhabha was able to set up an independent government agency, the Atomic Energy Commission, to take on the first needs of prospecting for nuclear energy ores and funding basic research. And soon, the development of a full-fledged programme was put in the hands of a specially empowered Department of Atomic Energy, with Bhabha at its head.

The purification of nuclear materials was still a close military secret and the technology of controlling nuclear reactions for power generation had made hardly any headway. It was in 1953 that Bhabha’s team made its first gram of uranium. The power needs of countries run into thousands of millions of watts (megawatts) and a nuclear programme would have to think of plants that would use tonnes of fuel, with precise controls and meticulous safety, as every nuclear plant had the potential to transform itself into a monster of horrendous destruction.

Basic research being carried out in TIFR was soon shifted to a dedicated facility, the Atomic Energy Establishment, now known as the Bhabha Atomic Research Centre, then just outside Mumbai. The AEE soon grew into a powerhouse of research and development, with its well planned laboratories, programmes to train scientists and engineers at the best facilities in the world. There was also the Training School, which undertook recruiting fresh graduates and honing them into the experts that the explosive growth in activities would call for.

As India had scarce resources of uranium, Bhabha tailored India’s nuclear energy programme to make the best of what there was. The thrust was hence on using natural uranium, which had only 0.6% of U235, the fissile kind, in place of ‘enriched uranium’, with a better proportion of U235, used by some countries. The economics of this strategy was that by suitable methods, the natural ore could fuel a first nuclear energy programme, so long as the supply of ore lasted. This would save the time and expense of creating an ore enrichment plant. A bye-product of fission in natural uranium was plutonium, another material capable of nuclear chain reaction, which got generated by the U238 present in the fuel. By the time the U235 got used up, there would be a stockpile of plutonium for another spell of power generation.

This possibility arises from the fact that the two or more neutrons that emerge from fission of U235, are, in fact, too energetic to optimally set off fresh U235 fission reactions. They could be more effective if slowed down a bit. The reactor is thus designed to be filled with a moderator, a material that the neutrons can strike, en route to striking U235 nuclei, and get slowed down in the impact. The best moderator is heavy water, a form of water where the nuclei of the hydrogen atoms are heavier than normal hydrogen nuclei. Heavy water also acts as the coolant and serves to carry away the heat generated in the reactor to be used to generate power in turbines.

Another moderator, already present in the natural uranium fuel is U238. High-energy neutrons get slowed down when they bump off U238 nuclei, just like with heavy water. This useful function apart, when a nucleus of U238 absorbs a neutron, the product is a nucleus with 238+1=239 particles in the nucleus. This is an unstable form of uranium, which spontaneously breaks down, before long, into the element plutonium. Plutonium, like U235, also undergoes fission, with production of neutrons that could sustain a chain reaction. When the U235 is gone, then, we could continue with a plutoniusm reactor!

And then, into this plutonium reactor, if one stuffed leftover U238, one would get still more plutonium. This kind of reactor would then become a breeder, a reactor that produces more fuel than it consumes!

This was the first step in the economy of making the best of the uranium reserves in the country. But there is yet another step, which depends upon thorium, Th232, of which, happily, India has ample reserves. When thorium is irradiated with neutrons in a plutonium reactor, it gets transformed into U233, again a fissile material. Phase III of India’s atomic energy plan was to generate U233 by exposing thorium to neutrons, and this phase would last a long time, because of abundant thorium deposits discovered on the Kerala coast.

As early as 1955, at an international conference on atomic energy at Geneva, Bhabha had recognized atomic power as being the practical, long-term answer to the world’s energy needs. At that conference, Bhabha had spoken of the next development in nuclear power, nuclear fusion, as being the real holy grail. While nuclear fission is getting power out of the splitting of heavy nuclei into more economical smaller units, nuclear fusion looks to the merging of light nuclei into more complex nuclei, a process that releases even more energy! Specifically, the nuclei of heavy hydrogen, which consist of a proton and a neutron, are forced close enough together. When they are close enough, attractive, nuclear forces take over and the nuclei merge, into a nucleus of helium, two protons and two neutrons.

Like in the case of fission, in fusion too, energy has first to be supplied to overcome a barrier before energy can be tapped when the system crashes down to a low-energy condition. But in the case of fusion, this is a truly formidable energy input that is required and the only way it has been done is with the help of a fission bomb, in the hydrogen bomb. But, in 1955, Bhabha spoke of the prospects of the process being controlled and harnessed. With the huge quantity of heavy hydrogen in the oceans, mastering fusion would put to an end any concerns about energy, at any rate!

It was with this confidence and optimism that Bhabha had approached setting up India’s atomic energy plan. With the large master plan of going from heavy water reactors to breeders and then using the thorium cycle in place, Bhabha set about its unfolding in practice. Innumerable details had to be developed, mastered and implemented. A professional prospecting body, to locate where nuclear ores could be mined had to be set up. The metals had to be extracted and the content of the useful isotopes improved. The fuel material then had to be shaped and packed, for the tortuous conditions in the reactor

Reactor design was an uncharted territory, esoteric in theory and exacting in practice. High temperatures and pressures apart, there was the need to contain radiation, as well as to provide for safety, in case of mishap. Even the civil structures that housed the facilities had to be specially designed and the plants had to be located far from towns and cities. And then methods had to be devised to dispose of spent fuel

With uncanny judgment, system and method, Bhabha led and inspired his team to plan and build the wide spectrum of interlocking systems, quite unlike anything in the ‘developing world’. Apart from two research reactors that were commissioned within the Bhabha Atomic Research Centre, the plans for a full fledged reactors in Rajasthan were finalised in 1963 and for another in 1966. But the same year, when Bhabha was on his way to Vienna for a meeting, he met an untimely and tragic end when the plane he was on crashed into the Alps.

The nation was plunged into shock and the setback seemed impossible to repair. But the ultimate testimony to the organization that Bhabha had created was that the organization rolled on when he died, almost without a break. In a country where it is customary to declare holidays to mourn the passing of great men, the Department of Atomic Energy worked resolutely the day of Bhabha’s death.

Bhabha’s grand plan had marked out a clear path and the Department followed it with energy and dedication. India is now self-sufficient in most components of nuclear power. Her heavy water technology, largely indigenous, has captured export markets. Her research establishments are second to few in the world and her backbone of manpower is formidable. Nuclear power is now an important and growing part of the power plan of the country