US details plutonium stocks

17 July 2012

The decommissioning of America's Rocky Flats facility and the disposal of resulting waste was the main factor in a four-tonne reduction in US plutonium stocks over the last 15 years.

From its pioneering nuclear energy research as well as an extensive weapons program, the USA counts over 95 tonnes of plutonium stored in various forms at nine sites across the country. The bulk of this came from Hanford, where nine reactors produced 67.4 tonnes, and from Savannah River, where five reactors made another 36.1 tonnes of plutonium.

The inventory information comes from an update to a landmark report, The United States Plutonium Balance, 1944-1996. Ordered by President Bill Clinton, that publication was aimed at demonstrating transparency. A new version released at the end of last month updated the figures to 2009, and revealed that the total amount of plutonium held in the country in all forms was 95.4 tonnes - down 4.1 tonnes on the 1996 figure.

The primary reason for the change was the complete decommissioning and clearance of the Rocky Flats complex, where nuclear weapons were made from 1952 to 1992. The transuranic wastes left over - those containing elements that are heavier than uranium, such as plutonium - have been permanently disposed of underground at the Department of Defense's Waste Isolation Pilot Plant (WIPP) in New Mexico. Those waste packages contained 3.5 tonnes of plutonium, among other unwanted radioactive materials. Another 9.2 tonnes of Rocky Flats plutonium in various forms was distributed to other sites for storage with similar stocks.

Three shipments to WIPP (460x114)
Three trucks carrying packages of military transuranic waste from Savannah River
arriving at WIPP last month

The report only covers nationally owned plutonium and so does not include that present in the used nuclear fuel of the country's nuclear power plants, past and present. The USA is essentially between firm policies on the managment of used nuclear fuel, having shelved the Yucca Mountain repository project without a successor in place. Reprocessing and recycling the plutonium in reactor fuel remains an option in the long term, as does straight disposal in its current form.

The vast majority of national plutonium belongs to the Department of Defense. Mainly stored at the Pantex assembly plant, some 43.4 tonnes of this 67.7 tonnes stockpile has been declared as 'surplus' to the needs of military programs. Thirty tonnes have been earmarked for inclusion in mixed-oxide nuclear fuel under a treaty signed with Russia, which plans to use an equivalent amount as fuel for fast-neutron reactors.

One minor factor in the US inventory is the acceptance of used research reactor fuel, samples and sources from around the country and abroad. The security-oriented Global Threat Reduction Initiative and Off-site Source Recovery Project have recovered approximately 800 sources containing more than 14 kilograms of plutonium from approximately 200 industrial, educational, government, and other facilities across the USA. These were managed at Los Alamos National Laboratory before disposal at WIPP.

Researched and written
by World Nuclear News