The Department of Energy (DOE) should develop an early warning capability to address dropping quantities of unobligated low-enriched uranium (LEU), a trend that could jeopardize U.S. compliance with international nuclear cooperation agreements, the Government Accountability Office (GAO) said in a report released Monday.
The United States’ nuclear cooperation agreements with other countries feature peaceful use provisions barring material obtained under those deals from being used for nuclear explosive devices or other military purposes – making that material “obligated.” The material is tracked by the Nuclear Materials and Management Safeguards System (NMMSS), a database managed by the National Nuclear Security Administration that is intended to ensure U.S. compliance with those international agreements.
The U.S. as of this June has 22 such agreements for peaceful nuclear cooperation with countries such as Canada, Japan, Russia, and South Korea, as well as with the International Atomic Energy Agency.
The GAO said that from 2003-2015, DOE contractors and Nuclear Regulatory Commission-licensed facilities conducted 817 obligated nuclear material exchanges, allowing for the transfer of obligations between facilities in the U.S. without physical movement of any nuclear material. “The total amounts of nuclear material at each facility do not change, and no material is physically moved, but the conditions on the use of the material have changed,” the GAO said.
Ninety-nine percent of the obligations involved low-enriched uranium or natural uranium, and 92 percent involved obligations from Australia or Canada, key nuclear trading partners for the U.S., it said.
Congressional auditors identified two issues that could impact the agencies’ ability to monitor nuclear material inventories. The first involved some facilities carrying negative obligation balances for a long period of time, which occurs when the facility makes an exchange without having enough of that material in its own inventory to cover the move. “In certain circumstances, negative balances may place the United States at risk of noncompliance with nuclear agreements,” the GAO said.
The second issue involved the declining U.S. inventory of unobligated LEU, which could otherwise be used to correct negative obligation balances. LEU is considered a vital national security need because of its use in production of tritium, which is used in nuclear weapons development. “NMMSS does not have an early-warning monitoring capability to alert DOE when the inventory is particularly low,” the GAO said; that situation puts the U.S. at risk of not complying with its nuclear agreements.
The Department of Energy has estimated that the domestic unobligated LEU inventory will last until 2038-2041. DOE’s 2014 Tritium Readiness Subprogram Tritium Production Fuel Supply Plan noted that sources of unobligated LEU fuel have included prior LEU purchases from U.S. Enrichment Corp. (now Centrus Energy Corp.), the Depleted Uranium Enrichment Project, and obligation exchanges with the Mixed Oxide LEU Backup Inventory Project.
The inventory has declined in recent years, namely because the U.S. lost its sole supplier of the material in 2013 when the now-Centrus Energy Corp. ceased its uranium enrichment operations. Most of the LEU in the U.S. carries foreign obligations, according to the GAO report.
The GAO recommended that the NNSA and NRC clarify the conditions under which facilities can have negative obligation balances, and develop an early warning monitoring capability that will alert DOE officials of a low unobligated LEU inventory.
DOE and the NRC said they are implementing actions to address the recommendations, but “did not explicitly state whether they concur,” the GAO said.
Specifically, DOE said it will address the early warning monitoring issue by its congressionally directed biennial updates to the Tritium and Enriched Uranium Management Plan through 2060. The GAO said that while this may be sufficient for now to monitor for declining LEU inventory, in the future “more frequent monitoring may be necessary.”