Nuclear Security Enterprise: Assessments of NNSA Major Projects

What GAO Found

The National Nuclear Security Administration (NNSA) is overseeing the design or construction of 28 major construction projects-each estimated to cost $100 million or more-that collectively are estimated to cost more than $30 billion.

Since GAO's 2023 report, cumulative cost and schedule overruns have increased for NNSA's portfolio of major projects in the execution phase (which have approved cost and schedule baselines). Specifically, as of June 2025, NNSA's cumulative cost overrun for the portfolio had increased from $2.1 billion in 2023 to $4.8 billion, and the cumulative schedule delay increased from 9 years to 30 years (see figure).

Cumulative Cost and Schedule Overruns for NNSA's Portfolio of Major Projects in Execution Phase, 2023-2025

Two of NNSA's 16 major projects in the execution phase-the Uranium Processing Facility (UPF) Main Process Building and UPF Salvage and Accountability Building at the Y-12 National Security Complex-are responsible for about 80 percent of the cumulative cost overrun and 40 percent of the cumulative schedule delay. However, seven other major projects in this phase have incurred or expect to incur a cost overrun of more than 20 percent compared with their originally approved cost baselines.

According to NNSA documents and officials, cost or schedule overruns for major projects in the execution phase were often associated with inadequate project management by NNSA's management and operating (M&O) contractors; poor performance by vendors or subcontractors overseen by M&O contractors; or increased costs of equipment, materials, or vendors.

Of the 12 NNSA major projects in the definition phase (which do not yet have cost and schedule baselines),

• eight are either on hold, implementing design changes, experiencing design challenges, or assessing the effect of these issues on their cost and schedule estimates; and
• four have identified critical technologies and have met milestones for maturing these technologies, according to project documents and officials.

Why GAO Did This Study

NNSA-a separately organized agency within the Department of Energy (DOE)-plans to invest tens of billions of dollars in major construction projects to modernize the research and production infrastructure supporting the nuclear weapons stockpile.

Senate Report 117-130, accompanying a bill for the National Defense Authorization Act for Fiscal Year 2023, includes a provision for GAO to review NNSA's major projects on a biennial basis. GAO assessed (1) the performance of NNSA's portfolio of major projects in the execution phase, and (2) the development and maturity of project designs and critical technologies for projects in the definition phase. This report also includes summaries of NNSA's 28 major projects.

GAO collected and analyzed data on NNSA's 28 major projects and interviewed officials. GAO analyzed information on cost and schedule performance for 16 projects in the execution phase. GAO also collected information on the status of design and technology maturity for 12 projects in the definition phase. GAO's review excluded major projects that did not have approved preliminary cost and schedule estimates or were not subject to certain DOE acquisition requirements.