Recent satellite imagery appears to have “clearly” revealed that Pakistan has completed the external construction of its fourth reactor building at the Khushab nuclear site located 200 kilometers south of Islamabad, a think-tank here has reported.

According to an report by Institute for Science and International Security (ISIS), which has monitored and catalogued changes at the Khushab complex using commercial satellite imagery to at the site, Pakistan started the construction of the fourth reactor at the end of 2010 or early 2011.

ISIS noted that a January 2011 image showed the building, similar in layout to the the second and third reactors at the same site, early in its construction but by April 2011, the frame of the reactor building and the main reactor hall were visible.

However images from November 1, 2013 clearly show that in addition to the near-completion of the fourth reactor’s external structure, the reactor stack and four of the six auxiliary buildings also present in reactors two and three “appear complete.”

Further, ISIS noted, t wo support buildings located immediately to the west of the reactor building were still under construction but the initial section of the cooling tower row is also visible and “appears about 30 per cent complete.”

The Khushab site is dedicated to the production of plutonium for nuclear weapons, ISIS noted, and originally it consisted of a heavy water production plant and a heavy water reactor, both of which became operational in the 1990s.

However, Pakistan initiated the construction of a second heavy water reactor between the year 2000 and 2002, a third one in 2006, and the fourth one in 2011.

The report also noted that the increased capability on this site “would allow Pakistan to build a larger number of “miniaturised plutonium-based nuclear weapons in order to complement its existing arsenal of highly enriched uranium weapons.”

Recently there has been talk of Pakistan considering the use of theatre or tactical nuclear weapons as a response to any conventional military aggression from neighbours.

Pakistan has reportedly not provided any public information about these three new reactors.

Speaking to The Hindu earlier, when prior developments at Khushab had been similarly picked up by satellite imagery, Paul Brannan, Senior Analyst at ISIS, said that given that “only few nations in the world have nuclear production capability [this development at Khushab], leading to a possible doubling of plutonium output in Pakistan, is significant.”