Satellite photographs show what appears to be the construction site for a larger nuclear reactor next to Pakistan's only plutonium production reactor, according to an analysis by experts at the Washington-based Institute for Science and International Security.
The new reactor would be a major expansion of Pakistan’s nuclear programme and could intensify the arms race in South Asia, according to the assessment, initially reported by The Washington Post and posted on the institute's website.
Analysts conclude that the diameter of the structure's metal shell suggests a very large reactor "operating in excess of 1,000 megawatts thermal," according to the report.
"Such a reactor could produce over 200kg of weapons-grade plutonium per year, assuming it operates at full power a modest 220 days per year," the technical assessment said.
"At four to five kilogrammes of plutonium per weapon, this stock would allow the production of over 40 to 50 nuclear weapons a year."
Pakistan is currently capable of producing about 10kg of plutonium a year, enough for about two warheads, The Washington Post said.
Construction of the new reactor in Khushab apparently began sometime after March 2000.
Aslam declined to say if Pakistan
was building a new reactor
The report's authors said Pakistan did not appear to be moving quickly to finish the reactor and said it might be facing shortages of reactor components or weapons production infrastructure.
A senior Pakistani official told the Washington Post that nuclear expansion was under way.
"Pakistan's nuclear programme has matured. We're now consolidating the programme with further expansions," the official was quoted as saying.
The United States said it knew about the development of a new reactor and urged Islamabad not to use it for military purposes.
Tasnim Aslam, Pakistan's foreign ministry spokeswoman, declined to say whether a new reactor was being constructed, but said that it was well known that there was a nuclear weapons programme and facilities at Khushab.
"Its coordinates are exchanged even with India under a 1988 agreement on nuclear facilities and installations. This list is exchanged every year on January 1," Aslam said.
Aslam said Pakistan was against a nuclear and conventional weapons arms race in the region.
Pakistan and its neighbour India - who have fought three wars since 1947 - both have nuclear weapons and have never signed the nuclear Non-Proliferation Treaty.