Countries: United States
The United States is a nuclear weapon state member of the Non-Proliferation Treaty. In January 2021, U.S. nuclear weapon stockpile was estimated to include 5,550 warheads. Of these, about 3,800 weapons are in active stockpile and about 1,750 weapons are awaiting dismantlement. The active stockpile includes 1,800 deployed warheads, assigned to strategic and non-strategic delivery systems, and an estimated 2,000 warheads in reserve.
The current stock of fissile materials in the United States is estimated to include 87.7 tonnes of plutonium and 562 tonnes of highly-enriched uranium (some of which is in irradiated naval fuel). The United States has no separated plutonium produced by a civilian program.
The United States is not producing fissile materials for weapons. Production of HEU for weapons ended in 1964. Additional HEU was produced for naval-reactor fuel through 1992. All U.S. production reactors were shut down in 1987.
The United States has a HEU stockpile estimated to be about 562 tons as of the beginning of 2020. In 2016 it declared that as of 30 September 2013 its HEU inventory was 585.6 tons, of which 499.4 tons was declared to be for "national security or non-national security programs including nuclear weapons, naval propulsion, nuclear energy, and science." The remaining 86.2 tons was composed of 41.6 tons "available for potential down-blend to low enriched uranium or, if not possible, disposal as low-level waste," and 44.6 tons in spent reactor fuel. Between September 2013 and September 2019 the United States down-blended additional 20 tons of HEU. The amount available for use had been reduced from 499.4 to about 477 tonnes, mostly by consumption in naval reactors. Of the 562 tons in the U.S. stockpile at the beginning of 2020, 82 tons of HEU is not available for military use - this includes the remaining 66 tons assigned to down-blending and in spent fuel and 16 tonnes of the 20 tonnes originally reserved for HEU fuel for research reactors.
According to the most recent official plutonium balance, in 2009 the United States measured inventory was 95.4 tons. According to U.S. INFICRC/549 declarations, since 2009 the United States disposed of additional 0.2 tons of plutonium in WIPP and lost 0.1 tons to radioactive decay. It also added 0.4 tons of research reactor plutonium transferred from abroad. Taking into account that the plutonium stock includes 7.8 tons of irradiated plutonium, the amount of separated plutonium is 87.7 tons.
Of the total amount of 87.7 tons of unirradiated plutonium, 79.7 tons are considered military stock. Even though the United States reports 49.3 tons of separated unirradited plutonium in its INFCIRC/549 declaration, most of this material is in weapons or weapon components or other weapon-origin material that retains classified attributes. Only 8.0 tons described below can be considered civilian. At the same time, none of the 49.3 tons of separated plutonium reported in INFCIRC/549 can be used for military purposes.
The United States has no separated plutonium that was produced by a civilian program. However, about 8.0 tons of plutonium can be considered civilian. As of the beginning of 2019, this material included 3 tons of plutonium at the Savannah River Site placed under IAEA safeguards, 4.6 tons of plutonium in unirradaited MOX fuel, and 0.4 tons of plutonium brought from abroad.