The 50 MWt, heavy water and natural uranium research reactor at Khushab is a central element of Pakistan's program for production of plutonium and tritium for advanced compact warheads. The Khushab facility, like that at Kahuta, is not subject to IAEA inspections, but the security of the site is professed by the Pakistani government. Khushab, with a capacity variously reported at between 40 MWT to 50 MWT [and as high as 70 MWT], was "commissioned" in March 1996, and had been under construction with Chinese assistance since the mid-1980s. According to a Pakistani press report ["Pakistan's Indigenous Nuclear Reactor Starts Up," Islamabad The Nation, April 13, 1998], the Khushab plutonium production reactor had gone critical and began operating in early 1998.
Plutonium is the preferred material for building light, sophisticated warheads, since highly enriched uranium (HEU) generally results in bulkier weapons. Prior to the start-up of Khushab, Pakistan was dependent on the production of highly enriched uranium at Kahuta. The Khushab reactor provides Pakistan the ability to produce enough plutonium each year to fabricate at least one bomb, and perhaps as many as three to five bombs [depending on the efficiency of the bomb design and the reactor's actual output].The actual plutonium output of Khushab is dependent on both the thermal power level, as well as the actual operating time. Pakistan's prior history of operating the Karachi Nuclear Power Plant (KANUPP), for many years Pakistan's only working nuclear power plant, suggests that the Khushab reactor may have a rather low operating availability. According to the International Atomic Energy Agency, the KANUPP lifetime energy availability factor (as of the end of 1997) was 28.6%, one of the worst performing nuclear power plants in the world. For the period 1989-1996 KANUPP’s capacity factor (the ratio of actual electrical production versus designed power) was only 34%. Although the CANDU reactor at KANUPP is of different design than Khushab, this history suggests that Khushab may produce substantially less plutonium than its theoretical capacity.
Pakistan initially sought to produce plutonium weapons, but these plans were frustrated with the 1977 cancellation by France of the planned sale of a reprocessing plant at Chasma. As of 1995 the US Government had no indication that Pakistan had the capability to reprocess plutonium.
According to a 14 September 1996 CIA report, the China Nuclear Energy Industry Corporation sold a special industrial furnace and high-tech diagnostic equipment. It was subsequently reported that the equipment was intended for the Khushab facility. High temperature furnaces are used to mold uranium or plutonium.
Pakistan succeeded in illicitly acquiring a tritium purification and storage plant, and tritium precursor materials from two German firms.
The United States apparently obtained a commitment from China not to supply the heavy water necessary to start up this unsafeguarded plutonium production reactor. But in March 1998 it was reported that China had supplied Pakistan with far more heavy water than needed to operate the safeguarded Kanupp nuclear power reactor, suggesting that Pakistan would be able to divert heavy water from the civilian plant to the Khushab military plant. Although these concerns received considerable political attention in the late 1990s, it is evident from IKONOS satellite imagery that the Khushab complex includes a heavy water production facility.