National Nuclear Security Administration: Additional Actions Needed to Plan for Science, Technology, and Engineering Facilities and Workforce Investments (Nimble Ultra Documentary Editions)

GAO-26-107904 examines how the National Nuclear Security Administration plans for the science, technology, and engineering facilities and workforce that support stockpile stewardship and modernization. These capabilities allow NNSA to assess and sustain the nuclear weapons stockpile without relying on nuclear explosive testing and also support other nuclear-security missions. GAO reports that NNSA's July 2024 Integrated ST&E Plan identified and prioritized 46 facility investments over a 20-year period. The portfolio includes sustainment and enhancement of existing facilities as well as new construction. GAO found that NNSA collected initial workforce and programmatic investment estimates but did not fully assess those needs and had no plan to complete such an assessment at the time of the review. Cost maturity varies across the portfolio. The fiscal year 2026 budget justification contained the most detailed information for seven high-mission-importance, near-term projects, while many other proposed investments remained in early planning or involved sustainment work. GAO also found that the integrated assessment had not been regularly updated even as priorities evolved. It recommended analysis of workforce and programmatic needs and regular updates to the facility assessment; NNSA outlined planned actions addressing both recommendations. Highlights and Letter. These sections state the congressional mandate, principal findings, methodology, and recommendations. The highlights page is an overview rather than a substitute for the supporting chapters. Background. The report maps the nuclear security enterprise, describes stockpile-stewardship ST&E areas, and explains the offices and acquisition processes relevant to facility planning. Facility, workforce, and programmatic planning. GAO evaluates the 46-investment prioritization and identifies the difference between facility planning and the less-complete assessment of workforce and programmatic needs. Cost information. The report distinguishes projects with budget-level estimates from early-stage or sustainment investments whose costs are less mature. Update process, conclusions, and recommendations. GAO explains why a static integrated assessment may lose decision value as technology, mission, and congressional priorities change. Appendixes and agency comments. The investment table, estimating-framework assessment, methodology, and Department of Energy response supply the evidentiary detail behind the findings. Documentary status. A record shows what an agency received, recorded, analyzed, or asserted at a particular time. It does not by itself establish that every underlying statement is accurate or that the agency adopted every view appearing in the file. Selection and survival. This edition reproduces the released source as received. It cannot establish what related records were never created, were destroyed, remain withheld, or sit outside the releasing agency's search and release process. Redaction and reproduction. Redactions, illegible passages, blank pages, handwriting, stamps, and scanning defects are evidentiary features of the source. They are preserved. Readers should not infer missing language from surrounding text. Temporal limits. Findings, estimates, organizational names, and management responses describe the period covered by the source. Later events may change the operational picture without changing the historical value of the record. A prioritized investment is not an appropriation or construction commitment. Projects can change scope, sequence, cost, or mission priority through planning, budgeting, authorization, and appropriations.