Explanation

 March 1948

From May 28-30, 1998, Pakistan conducted up to six nuclear tests. According to a statement from the Pakistani government, the nuclear test equipment contained "uranium-235" called "weapons-grade uranium" (WGU, uranium rich in more than 90% uranium-235). The  uranium was produced at the Khan Research Laboratories (KRL), called the Kafta Plant, near Islamabad, according to a statement. Pakistan's tests remove doubts about its ability to produce nuclear weapons, but Pakistan's WGU stockpile estimates are full of significant uncertainty.