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Nuclear Weapons: NNSA Should Clarify Long-Term Uranium Enrichment Mission Needs and Improve Technology Cost Estimates

GAO-18-126 Published: Feb 16, 2018. Publicly Released: Feb 16, 2018.
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Fast Facts

The National Nuclear Security Administration manages U.S.-origin enriched uranium for certain needs such as for the production of tritium, which is used in nuclear weapons. After losing its last source of U.S.-origin enriched uranium in 2013, NNSA projected that its supply would run out in 2027.

We found that NNSA has extended its supply through 2038 but it has not clearly defined longer term enriched uranium needs. We also found that NNSA's preliminary cost estimates for building a new enrichment capability are not reliable.

We recommended that NNSA clarify the scope of its mission need statement and create new cost estimates.

Uranium enrichment centrifuges demonstrated at a pilot plant in Ohio

Photo of centrifuges for uranium enrichment

Photo of centrifuges for uranium enrichment

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What GAO Found

The National Nuclear Security Administration (NNSA), a separately organized agency within the Department of Energy (DOE), is taking or plans to take four actions to extend inventories of low-enriched uranium (LEU) that is unobligated, or carries no promises or peaceful use to foreign trade partners until about 2038 to 2041. Two of the actions involve preserving supplies of LEU, and the other two involve diluting highly enriched uranium (HEU) with lower enriched forms of uranium to produce LEU. GAO reviewed these actions and found the actual costs and schedules for those taken to date generally align with estimates. NNSA and GAO have identified risks associated with two of these actions. One of these risks has been resolved; NNSA is taking steps to mitigate another, while others, such as uncertainty of future appropriations, are unresolved.

NNSA's preliminary plan for analyzing options to supply unobligated enriched uranium in the long term is inconsistent with DOE directives for the acquisition of capital assets, which state that the mission need statement should be a clear and concise description of the gap between current capabilities and the mission need. The scope of the mission need statement that NNSA has developed can be interpreted to meet two different mission needs: (1) a need for enriched uranium for multiple national security needs, including tritium, and (2) a specific need for enriched uranium to produce tritium. The DOE directives also state that mission need should be independent of and not defined by a particular solution. However, NNSA is showing preference toward a particular solution—building a new uranium enrichment capability—and the agency has not included other technology options for analysis. Without (1) revising the scope of the mission need statement to clarify the mission need it seeks to achieve and (2) adjusting the range of options it considers in the analysis of alternatives process, NNSA may not consider all options to satisfy its mission need.

Although the scope of the mission need statement is unclear, NNSA has prepared preliminary cost estimates for the two uranium enrichment technology options—the large and small centrifuge—that the agency considers to be the most feasible. However, these estimates are limited in scope and do not fully meet best practices for reliable cost estimates. Based on GAO's review of NNSA documents, NNSA appears to favor an incremental approach to reestablishing an enrichment capability that could ultimately meet all national security needs for enriched uranium. The estimates' scope is limited, however, in that they reflect only the costs of the first increment—producing LEU for tritium—and do not reflect the full costs of building a uranium enrichment facility that could meet the range of enriched uranium needs. GAO's cost guide—which provides cost estimating best practices—states that the scope of preliminary cost estimates should reflect full life-cycle costs. Also, NNSA's estimates for the two options minimally or partially met best practice characteristics for reliable cost estimates even when assessed for the more limited mission scope. For example, the estimates excluded certain costs and did not describe the calculations used. NNSA officials said that the cost estimates are preliminary and will be revised. By developing reliable cost estimates that are aligned with the revised mission need statement and consistent with best practices, NNSA will reasonably ensure that it has reliable information to make a decision about which option to select.

Why GAO Did This Study

NNSA has several mission needs for enriched uranium, including providing LEU to fuel a nuclear reactor that produces tritium—a key isotope used in nuclear weapons. NNSA has a pressing defense need for unobligated LEU to fuel this reactor, meaning the uranium, technology and equipment used to produce the LEU, must be U.S. in origin. Because the United States lost its only source of unobligated LEU production in 2013, the supply is finite.

A House Armed Services Committee report included a provision for GAO to assess NNSA's plans to manage tritium and enriched uranium. This report examines (1) the actions NNSA is taking to extend its existing LEU inventories to address near-term tritium needs; (2) the extent to which NNSA's plan to analyze long-term options for supplying enriched uranium is consistent with DOE directives; and (3) NNSA's preliminary cost estimates for long-term uranium enrichment technology options and the extent to which they meet best practices for reliable estimates. GAO analyzed NNSA plans on costs, schedules, and risks; compared them with its guide on best practices in cost estimating; and interviewed NNSA and other officials.


GAO is making two recommendations, including that NNSA revise the scope of its mission need statement and ensure that the scope of its cost estimates are aligned with the revised statement while developing estimates consistent with best practices. NNSA described actions planned and in process to address both recommendations.

Recommendations for Executive Action

Agency Affected Recommendation Status
National Nuclear Security Administration The NNSA Administrator should revise the scope of the mission need statement to clarify which mission need it seeks to achieve and, as appropriate, adjust the range of options considered in the analysis of alternatives process. (Recommendation 1)
Closed – Implemented
NNSA disagreed with our recommendation and stated that it would not revise the mission need statement to address the full range of uranium mission needs. However, NNSA has taken other actions to clarify the mission need it intends to address by incorporating all of NNSA's uranium enrichment requirements into the domestic uranium enrichment (DUE) analysis of alternatives (AOA) process. In May 2021, NNSA officials stated that NNSA had divided the DUE AOA into two phases. NNSA completed the first phase in March 2021 and has paused the process to allow time for further technology maturation to inform its cost estimates. NNSA estimated that it will undertake the second phase of the AOA in the mid-2020s and indicated that the second phase would include an adjusted range of options, narrowed based on the phase 1 analysis.
National Nuclear Security Administration The NNSA Administrator should--following clarification of the scope of the mission need statement--ensure that the agency's cost estimates for whichever options it considers going forward are aligned with the scope of the mission need that the enrichment capability is intended to fulfill and that they are developed consistent with best practices. (Recommendation 2)
NNSA disagreed with our recommendation and in June 2018 stated that its cost estimates for the options under consideration were sufficient given the early stage of the Domestic Uranium Enrichment Analysis of Alternatives (AOA) process. However, NNSA stated that it intended to produce higher fidelity estimates on the options as it goes through the AOA. In May 2021, NNSA officials stated that they had prepared initial cost ranges for the options, but that because of significant uncertainties, there was a tremendous range in the estimated costs. These officials said that the agency was extending its evaluation period and would divide the AOA into two phases. NNSA has completed the first phase of the AOA, but has paused the process to allow time for technology maturation that will inform more accurate cost estimates of the options in the future. NNSA intends to resume the AOA in the mid-2020s, at which time there will likely be updated cost estimates for us to review. We will continue monitoring the AOA process and will review the AOA once it is completed to determine whether we can close this recommendation at that time.

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