U.S. civilian plutonium holdings in December 2012

The United States finally submitted to IAEA the INFCIRC/549 declaration of its civilian plutonium stock. The document was published by the IAEA on April 2, 2014 as INFCIRC/549/Add.6/16. According to IAEA, the United States submitted its declaration to the Agency on March 14, 2014, much later than usual.

According to the declaration, as of 31 December 2012 the United States had 44.4 tonnes of separated plutonium described as "held elsewhere", 4.6 tonnes - in unirradiated MOX fuel, and less than 0.05 tonnes - held in the fuel fabrication process. In December 2011 these numbers were 44.7, 4.6, and 0.05 tonnes respectively.

The declaration contains the following note:

Lines 3 [4.6] and 4 [44.4] together list 49.0 metric tons of separated plutonium that has been declared as excess to national security needs. This, in addition to 7.8 metric tons of the plutonium included on lines 1 [plutonium contained in spent fuel at civil reactor sites] and 3 [plutonium contained in spent fuel held elsewhere] of Annex C, 4.5 metric tons that has been disposed to waste after termination of safeguards, and 0.2 metric tons lost to radioactive decay (both after September 1994), constitute the total of 61.5 metric tons of government owned plutonium that the United States has declared as excess to national security needs. The change in Line 4 includes the (rounded) cumulative allowance for decay and an additional 0.1 metric tons disposed to waste during 2012.
The total amount of plutonium declared excess - 61.5 tonnes - has not changed since the 2011 declaration. However, the breakdown of this number is now different. The amount of plutonium disposed of as waste increased from 4.4 to 4.5 tonnes. Also, since 1994 0.2 tonnes was lost to radioactive decay. This decay and disposal of plutonium as waste are responsible for the decrease of the amount of separated plutonium from 44.7 to 44.4 tonnes.

The actual amount of separated plutonium that is excess to security needs is therefore 49.0 tonnes - 61.5 tonnes minus 7.8 tonnes in spent fuel, 0.2 tonnes lost to decay since 1994 and 4.5 tonnes disposed as waste and lost to decay in 2012.