Eminent nuclear scientist PK Iyengar, former chairman of Atomic Energy Commission and a key member of the team which made possible India’s first peaceful nuclear explosion in 1974, passed away after a brief illness on Wednesday here, an official source said. He was 80.He is survived by his wife Seetha, a son and a daughter. Iyengar was renowned as a nuclear physicist with keen interest in developing indigenous experimental facilities.He was the AEC chief and secretary, Department of Atomic Energy from 1990-93, his last official position before retirement. Later, he served briefly as scientific advisor to Kerala government in 1998, an official said.A vocal opponent of the Indo-US nuclear agreement, Iyengar had been living a quiet, retired life in Mumbai’s middle-class suburb of Deonar.After graduating in physics from Trivandrum, Iyengar joined the famous Tata Institute of Fundamental Research in 1952 in Mumbai.He was engaged in the design and setting up of the country’s first fast reactor critical facility, Purnima-1, which achieved its first criticality May 18, 1972, paving the way for India’s first peaceful nuclear experiment exactly two years later, on May 18, 1974, at Pokhran.