Iyengar joined the Tata Institute for Fundamental Research,
Department of Atomic Energy in 1952 as a junior research scientist, undertaking a wide variety of research in
neutron scattering. He later got shifted to Atomic Energy Establishment (later renamed as Bhabha Atomic Research Centre) when it was formed in 1954. In 1956, Iyengar was trained in Canada working under
Nobel laureate in Physics Bertram Neville Brockhouse, contributing to path-breaking research on lattice dynamics in
germanium. At the DAE, he built up and headed the team of physicists and chemists that gained international recognition for their original research contributions in this field. In 1960s, he indigenously designed the PURNIMA reactor and headed the team that successfully commissioned the reactor on 18 May 1972 at
BARC.
Operation Smiling Buddha When Ramanna took over as director of
Bhabha Atomic Research Centre in 1972, the mantle of directorship of the Physics Group (PG) was handed over to Iyengar. He was one of the key scientist in the development of India's first
nuclear device. The team, under
Raja Ramanna tested the device under the code name
Smiling Buddha on 18 May 1974. Iyengar played a leading role in the
peaceful nuclear explosion at
Pokharan-I, for which he was conferred the
Padma Bhushan in 1975. ==Career with Bhabha Atomic Research Centre==