Countries: United States

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The United States is a nuclear weapon state member of the Non-Proliferation Treaty. In January 2017, the United States declared a stockpile of 4,018 warheads. This stockpile included about 1,700 strategic warheads deployed on missiles and strategic bombers, 150 non-strategic warheads in Europe, and approximately 2,100 warheads in reserve. Additional 2,500 warheads are awaiting dismantlement. Taking into account the warheads in the dismantlement queue, the size of the U.S. weapon arsenal is estimated to be 6,500 nuclear warheads.

The current stock of fissile materials in the United States is estimated to include 87.8 tonnes of plutonium and 574.5 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.

Highly-enriched uranium

The United States has a HEU stockpile estimated to be about 574.5 tons. 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 January 2017 the United States down-blended 11.1 tons of HEU. Of the 574.5 tons in the U.S. stockpile at the end of 2016, 95 tons of HEU is not available for military use - this includes the remaining 75.1 tons assigned to down-blending and in spent fuel as well as 20 tons of HEU that were earlier reserved for HEU fuel of research reactors.

There are several new commercial uranium enrichment facilities that are being built in the United States, none of which will be producing highly-enriched uranium.

Weapon plutonium

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 0.1 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 87.8 tons.

Of the total amount of 87.8 tons of unirradiated plutonium, 80.8 tons are considered military stock. Even though the United States reports 49.4 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 7.0 tons described below can be consdered civilian. At the same time, none of the 49.4 tons of separated plutonium reported in INFCIRC/549 can be used for military purposes.

Civilian plutonium

The United States has no separated plutonium that was produced by a civilian program. However, about 7.0 tons of plutonium can be considered civilian. As of the end of 2016, this material includes 2 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.