Plutonium Test: Chagai-II
From the outset, Khan focused on the indigenous development of a plutonium program as part of the fuel cycle. Despite many difficulties, Khan and PAEC successfully developed and managed the plutonium infrastructure. Khan lobbied and enlightened the importance of plutonium-tritium device and countered the scientific opposition that was led by fellow scientist Abdul Qadeer Khan, who opposed the plutonium route and favoured the uranium atomic bomb. Khan concentrated the development efforts on plutonium implosion-type fission device, in a single group of TPG, which became to known as Chagai-II. Khan countered and later abandoned the developmental efforts on uranium gun-type fission weapon, when on developing the theoretical design, a problem was discovered by TPG who put efforts to work with Qadeer Khan on gun-type in 1976.
The gun-type fission weapon is a simpler design that only had to work with uranium-235 but a possibility of weapon's chain reaction to reach the limit of fizzle level was identified; therefore, the TPG and Khan abandoned the gun design in favour of an implosion-type weapon. In 1983, a milestone was done when a joint work of scientists produced the artificial non-nuclear fission reaction at Kirana Atomic Tests Site (KATS) where the reactor-grade plutonium was used to defer the weapon to go fission. In May 1998, the success of plutonium bomb was proved when it was reported that PAEC conducted a test of a powerful plutonium device, Chagai-II, to artificially produced the nuclear fission, and this plutonium device had the largest yield of all the uranium bombs.
In 1999, Khan described the large scientific efforts and PAEC's contribution in heading up and building Pakistan's atomic bomb projec, as he stated:In 1979-80, the PAEC completed the iron-steel tunnels in Chagai region. On March 11 1983, we successfully conducted (cold) test of a working design of our first atomic bomb. That evenning, I went to General Zia with the news that Pakistan was now ready to make an atomic bomb. We conducted this cold test long before the was available for actual test. We were ahead of others..... —Munir Ahmad Khan, Statement giving to news media in 1999, source.