U.S. Government Accountability Office (GAO), released a report, "DOE Made Progress to Secure Vulnerable Nuclear Materials Worldwide, but Opportunities Exist to Improve Its Efforts," GAO-15-799 that evaluates the results of the initiative to secure all vulnerable nuclear materials within four years, announced by President Obama in April 2009.

The key finding of the report is that

DOE exceeded its goal for removing or disposing of 1,201 kilograms of highly enriched uranium (HEU) or plutonium by more than 400 kilograms, and it exceeded its goal of downblending [(i.e., mixing HEU with either depleted or natural uranium, or low-enriched uranium (LEU), to produce a new product that has a lower concentration of uranium-235) [...] 2,700 kilograms of HEU by an additional 2,200 kilograms. However, it missed its goal for providing physical protection upgrades at 43 buildings by 11 buildings and missed its goal of converting 34 foreign reactors to more proliferation-resistant LEU by 11 reactors.

The new goal set by DoE is "to remove or dispose of an additional 1,029 kilograms of fresh and spent HEU, as well as plutonium worldwide from 2014 to December 2019, and convert 27 foreign research reactors and medical isotope production facilities to LEU by the end of fiscal year 2019."

However, the report noted that "DOE and other U.S. agencies have not completed an inventory of U.S plutonium overseas," which limits U.S. ability to determine whether this material is adequately protected.

GTRI is said to have completed an inventory of U.S.-origin HEU in June 2013. According to the GAO report, GTRI has found that "more than 13,000 kilograms of U.S.-origin HEU remain worldwide, including 3,526 kilograms of unirradiated or fresh U.S.-origin HEU and 1,771 kilograms of irradiated U.S.-origin HEU eligible for return [as well as] 4,605 kilograms of U.S.-origin irradiated HEU [...] ineligible for return to the United States." It is not clear, however, why the amount of HEU in these categories does not add up to the total of 13,000 kg. Note also that these numbers are different from the ones provided in the NRC report on foreign HEU, released in May 2014, which concluded that "approximately 6,100 kg of that U.S.-supplied HEU presently remains in 20 countries." The discrepancy may reflect the fact that the NRC report did not include "HEU exported for purposes other than use as fuel or targets in [research and test reactors]."