Nuclear Weapons Sustainment: Improvements Made to Budget Estimates in Fiscal Year 2019 Joint Report, but Opportunities Remain to Enhance Completeness [open pdf - 2MB]
From the Document: "The Department of Defense (DOD) and the Department of Energy (DOE), through its National Nuclear Security Administration (NNSA), are undertaking an extensive, multifaceted effort to sustain and modernize U.S. nuclear weapons capabilities. These capabilities include the nuclear weapons stockpile; the research and production infrastructure; delivery systems; and the nuclear command, control, and communications (NC3) system. DOD and DOE estimates show that nuclear sustainment and modernization efforts are expected to cost hundreds of billions of dollars over the next decade."
Government Accountability Office: http://www.gao.gov/