There are over 3,700 metric tons of plutonium and highly-enriched uranium in global stockpiles, according to a recent report by the Institute for Science and International Security (ISIS).  Global Stocks  of Nuclear Explosive Materials, authored by David Albright and Kimberly Kramer, says that these materials, together with the 140 tonnes of Neptunium 237 and Americium, are enough for over 300,000 nuclear weapons. 

The report estimates that at the end of 2003, 50 countries held a total of 1,900 tonnes of HEU, with nine of those countries in possession of at least 1 tonne.  Nearly 91 percent of global HEU is in military stockpiles.  According to the report, “stocks of civil HEU are decreasing as HEU is blended down into low enriched uranium” and by 2020, “the number of countries with a kilogram of HEU could decrease from about 50 to no more than 10 or 20 countries,” due to take-back programs initiated by the United States and Russia to consolidate civil HEU stocks. 

Over the next 15 years, global stocks of separated civil plutonium will not decrease significantly.  In fact, the report says, despite the “consensus in the international community that stockpiles of separated plutonium should be minimized because they are a proliferation hazard,” currently “the amount of separated (unirradiated) civil plutonium in the world continues to increase.”  At the end of 2003, 25 countries had at least 5 tonnes of plutonium.  Problems that will lead to continued unirradiated plutonium increases “include the separation of more plutonium than can be used, delays in gaining approvals in loading MOX fuel, and the impact of unexpected events such as nuclear accidents or incidents that further delay MOX programs.”

The ISIS report also estimates the number of potential nuclear weapons Israel, India, Pakistan, and the DPRK could build from estimated fissile material stockpiles through the end of 2003.  Israel is believed to have the capability to produce around 145 nuclear weapons, whereas India and Pakistan could produce around 80 and 70 respectively.  Estimates vary for the DPRK, ranging from 3-9 weapons. 

The study also notes that “separated plutonium and both separated and irradiated HEU in [certain] countries…are of special concern because of the risk of diversion for use by terrorists.” Russia, Pakistan, and North Korea are some of the “most important to understand and secure.”  

The report provides detailed tables and charts on national and global holdings.