in 1968, joining the Nuclear Physics Division at the Pakistan Institute of Nuclear Science and Technology (PINSTECH) working under Dr. Naeem Ahmad Khan. His collaboration took place with Samar Mubarakmand, Hafeez Qureshi, and he was a vital member of the group before it was discontinued in 1970. Mahmood was one of the foremost experts on civilian reactor technology and was a senior engineer at the Karachi Nuclear Power Plant (KANUPP I)— the first commercial nuclear power plant in Pakistan. He gained notability and publicity in the Pakistan Physics Society for inventing a scientific instrument, the 'SBM probe', to detect leaks in steam pipes, a problem that was affecting nuclear plants all over the world and is still used worldwide. After witnessing the Indo-Pakistani War of 1971, which saw the unconditional surrender of Pakistan in 1971, Mahmood attended the winter seminar at Multan and delivered a speech on atomic science. On 20 January 1972, the President of Pakistan, Zulfikar Ali Bhutto, approved a crash atomic weapon programme, under Munir Ahmad Khan, for the sake of "national survivor." Though, he continued his work at the KANUPP I engineering division. In the aftermath of 'Smiling Buddha', a surprise nuclear test conducted by India in May 1974, Munir Ahmad appointed Mahmood as the director of the enrichment division at PAEC, where the majority of calculations were conducted by Dr. Khalil Qureshi– a physical chemist. Mahmood analysed the gaseous diffusion, gas centrifuge, jet-nozzle and molecular laser isotope separation method for uranium-enrichment; recommending the gas centrifuge method as economical. After submitting the report, Mahmood was asked to depart to the Netherlands to interview Dr. Abdul Qadeer Khan on behalf of President Bhutto in 1974. In 1975, his proposal was approved and the work on uranium enrichment started with Mahmood as its director, a move that irked the more qualified but more difficult to manage Dr. Abdul Qadeer Khan, who had coveted the job for himself. His relations with Dr. Khan remains extremely tense and the pairs disagreed with each other and developed differences at great height. In private meetings with Munir Ahmad, Mahmood often complained and pictured him as "egomaniac". In 1976, Mahmood was removed from the enrichment division, Project-706, by Abdul Qadeer Khan, and Khan moved the enrichment division at the Engineering Research Laboratories (ERL) under military control. Eventually, Munir Ahmad removed Mahmood from other classified works and posted him back to the Karachi Nuclear