The United Kingdom released information about its holdings of civilian plutonium and uranium as of December 31, 2013. The report was published and an IAEA document INFCIRC/549/Add.8/17.

According to the document, as of the end of 2013 the U.K. had 118.8 (116.1 in 2012) tonnes of separated unirradiated plutonium at the reprocessing facilities, 0.8 (1.2) tonnes in unirradiated MOX fuel and 1.9 (1.9) tonnes in the MOX fuel manufacturing process. Additional 1.5 (1.0) tonnes of unirradiated plutonium is "held elsewhere." These numbers include the 4.7 tonnes of plutonium that the United Kingdom declared as excess to its national security needs. This material has been transferred to the civilian stock and placed under Euratom safeguards.

Of this total of 123.0 (120.2) tonnes, 23.4 (23.8) tonnes belonged to foreign countries. In addition, the U.K. had 0.9 tonnes of its plutonium outside of country. No material was in transit.

The total amount of separated civilian Pu in the UK is 123.0 tonnes (120.2 tonnes in 2012), the total amount of UK owned plutonium is 100.5 tonnes (97.3 in 2012). The increase of the UK owned plutonium reflects the result of a series of title swaps, performed in April 2013, in which 2,950 kg of plutonium were transferred to the UK custody. The numbers, however, does not take into account the 2014 plutonium title transfers.

In addition, the United Kingdom declared 8 tonnes of plutonium in spent fuel held at reactor sites (7 tonnes were reported in this category in 2012), 23 (24) tonnes - in spent fuel at reprocessing plants awaiting reprocessing, and less than 500 kg - in spent fuel held elsewhere.

The report also contains information about civilian HEU holdings - the United Kingdom had 1398 kg of the material, up from 1396 kg in 2012. Of this HEU, 342 kg is at fabrication plants (343 in 2012), 914 (912) kg - at laboratories and research facilities, 10 kg - irradiated HEU at civilian reactor cites, and 131 kg - irradiated HEU at other sites.