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Nuclear reactors and rockets look like different worlds, but both depend on metals that behave well in brutal conditions. Brahm Prakash spent his career making those metals in India. This post covers his work in atomic energy and space, the chemistry problem at the heart of nuclear zirconium, and a worked example on why a trace of one element mattered so much.
Who was Brahm Prakash?
The Vikram Sarabhai Space Centre (VSSC) says he was born on 21 August 1912 in Lahore and studied chemistry, doing doctoral research at Punjab University. The biographical memoir published by the Indian National Science Academy adds that he worked with Shanti Swarup Bhatnagar on the magnetic properties of transition metal compounds, earning his first doctorate in physical chemistry in 1942.
After the war he went to the USA. At MIT he took a second doctorate, a Sc.D. in metallurgy on mineral flotation, and developed a love for thermodynamics. When he returned, Homi Bhabha chose him as metallurgist for the Atomic Energy Establishment. From 1951 to 1957 he headed the Department of Metallurgy at the Indian Institute of Science in Bangalore, building modern courses in metallurgical thermodynamics and physical metallurgy.
What did he do for India's nuclear programme?
From 1957 to 1972 he led the Metallurgy Group at Trombay, which the memoir calls the largest group there. VSSC records that his team commissioned the fuel fabrication facility for the CIRUS research reactor in 1959. The memoir adds that the first Indian fuel elements, sent to Canada for testing, performed even better than the Canadian ones, and that his group later supplied half of the first fuel charge for the Rajasthan power reactor at Kota.
He also coordinated plans for the Nuclear Fuel Complex in Hyderabad as Project Director and chaired the Uranium Corporation of India.
Why is zirconium so hard to make?
The memoir explains the problem. Zirconium alloy is used to clad uranium oxide fuel in water-cooled reactors because it absorbs few neutrons, stays strong when hot and resists corrosion. But its ore, zircon, always contains a little hafnium, and zirconium and hafnium are so alike chemically that they are very hard to separate. Hafnium, unlike zirconium, is a strong neutron absorber, so it has to come out.
Brahm Prakash and C. V. Sundaram developed two processes, one using selective vapour-phase dechlorination of zirconium tetrachloride. His 1955 paper on it at the first UN conference on peaceful uses of atomic energy in Geneva was, the memoir says, acclaimed as the first original pyrochemical approach to the problem.
Worked example: how much does a trace of hafnium matter?
Neutron absorption is measured by a cross-section in barns. The NIST neutron data table gives absorption cross-sections for slow neutrons of 0.185 barn for zirconium and 104.1 barn for hafnium. That is 104.1 / 0.185 = 563 times larger.
For a mixture, take a weighted average by atom fraction. These are sample compositions for practice:
2 hafnium atoms in every 100. 0.98 x 0.185 + 0.02 x 104.1 = 0.181 + 2.082 = 2.263 barn. That is 2.263 / 0.185 = 12.2 times pure zirconium.
1 hafnium atom in every 10,000. 0.9999 x 0.185 + 0.0001 x 104.1 = 0.18498 + 0.01041 = 0.1954 barn, only about 6 per cent above pure zirconium.
Two per cent hafnium makes the cladding absorb neutrons twelve times as strongly, which would waste neutrons the chain reaction needs. Separation has to bring hafnium down to traces.
The same weighted-average step appears whenever you calculate average atomic mass from isotopes. If that step is where your answer goes wrong, the Fermi Problem Library has worked problems with a step-by-step solver that explains the reasoning rather than printing an answer. For the reactor side, read our post on nuclear fission and fusion energy.
What did he do at the space centre?
VSSC says Satish Dhawan persuaded him to become its Director in May 1972, a post he held until November 1979. The memoir describes his task as welding several separate units at Thiruvananthapuram into one centre, and putting the Rohini sounding rocket and SLV-3 launch vehicle projects on a sound footing. When SLV-3 failed on its first flight on 19 August 1979, the memoir records that A. P. J. Abdul Kalam later recalled Brahm Prakash's reassurance: "Don't give up." The next flight succeeded a year later.
He also pushed for Indian industry to make launch vehicle hardware and special alloys. As chairman of Mishra Dhatu Nigam (MIDHANI) from 1980 to 1984, he backed the choice of maraging steel for future space vehicles, and MIDHANI later supplied the titanium for alloy gas bottles and tanks on the ASLV and PSLV rockets. Our posts on Satish Dhawan and A. P. J. Abdul Kalam cover the same years from their side.
VSSC records that he received the Padma Shri in 1961 and the Padma Bhushan in 1968, and died on 3 January 1984.
What can a student take from his way of working?
Fundamentals travel. A chemist's training in magnetism and thermodynamics became the base for nuclear and rocket metallurgy.
Solve the bottleneck. He focused on the step everything else depended on, such as hafnium removal.
Steady people matter after a failure. His calm after SLV-3 E1 kept a young team working.
Try it now: calculate the absorption cross-section for zirconium with 1 hafnium atom in every 1,000, and compare it with pure zirconium.
