 Although the agreement had largely broken down, North Korea did not restart work on the two production size nuclear power plants that were frozen under the agreement.These plants could potentially have produced enough weapons-grade plutonium to produce several nuclear weapons per year.The Agreed Framework was successful in freezing North Korean plutonium production in Yongbyon plutonium complex for eight years from 1994 to December 2002; however, it failed to stop North Korea from developing a secret highly enriched uranium program, begun in the "mid- or late-1990s."