The International Panel on Fissile Materials has released Global Fissile Material Report 2015: Nuclear Weapon and Fissile Material Stockpiles and Production (PDF). This is the eighth Global Fissile Material Report.

The report provides updated estimates for global and national stockpiles of HEU and plutonium, the key ingredients in nuclear weapons and recent developments in military and civilian fissile material production capabilities in nuclear weapon states and in the non-weapon states.

In 2015, the global stockpile of nuclear weapons was estimated at over 15,800 weapons, with the United States and Russia together holding about 14,700 of these weapons and the other seven nuclear weapon states holding a combined total of about 1100 weapons.

The global stockpile of HEU at the end of 2014 was about 1370 ± 125 tons, enough for more than 76,000 simple, first generation fission implosion weapons. About 99 percent of this material is held by the nuclear weapon states, mostly by Russia and the United States. The large uncertainty in the HEU estimate is due to a lack of official information about Russia's historical production of HEU. The uncertainty in the size of the Russian HEU stockpile is larger than the total HEU stocks held by all other states except for the United States.

The United States, United Kingdom, Russia, France and China all stopped producing HEU for weapons, in some cases decades ago. Today, only India, Pakistan and possibly North Korea are believed to be producing HEU for weapons purposes. Russia has restarted HEU production to meet the need for reactor fuel.

In 2014, for the first time in about two decades, the global HEU stockpile stopped shrinking and remained nearly constant after Russia ended its down blending of excess HEU to low-enriched uranium for sale to the United States. The United States has about 40 tons of excess HEU remaining to be blended down, which is scheduled to be completed by 2030. Neither country has declared any additional HEU excess.

The global stockpile of separated plutonium as of the end of 2014 was about 505 ± 10 tons. Less than half of this stockpile was produced for weapons. The majority of the global plutonium stockpile is the result of civilian programs in nuclear weapon states, some of it for foreign customers. As a result, about 98 percent of all separated plutonium is stored in the nuclear weapon states.

The stockpile of separated plutonium for weapons continues to increase because of continued production in Israel, India, and Pakistan. As of late 2015, the United States and Russia have still not started verifiably disposing of the 34 tons of plutonium that each declared as excess to weapon purposes.

There are about 53 tons of plutonium owned by the non-weapon states, most of which is in storage in France and the United Kingdom, and mostly belongs to Japan.

The report features a new section "Nuclear Weapons, Fissile Materials and Transparency" updating the material presented in Global Fissile Material Report 2013: Increasing Transparency of Nuclear Warhead and Fissile Material Stocks as a Step toward Disarmament, released in October 2013.

This section includes a transparency matrix assessing progress by the nuclear weapon states on meeting their obligations under the terms of the 2010 "Action Plan on Nuclear Disarmament," to cooperate on steps to increase transparency about arsenals and fissile material stockpiles and to develop verification capabilities related to nuclear disarmament and in particular to report information that can further openness and verification.

Michael Schoeppner of Princeton's Program on Science and Global Security provided editorial assistance in preparing Global Fissile Material Report 2015.