WASHINGTON — The Pentagon will have to spend billions of dollars over the next five years to make emergency fixes to its nuclear weapons infrastructure, Defense Secretary Chuck Hagel will announce on Friday, after two separate Pentagon studies concluded that there are “systemic problems across the nuclear enterprise,” according to senior defense officials.

The reports are a searing indictment of how the Air Force’s and Navy’s aging nuclear weapons facilities, silos and submarine fleet have been allowed to decay since the end of the Cold War. A broad review was begun after academic cheating scandals and the dismissal of top officers for misbehavior, but it uncovered far more serious problems.

For example, while inspectors obsessed over whether every checklist and review of individual medical records was completed, they ignored huge problems, including aging blast doors over 60-year-old silos that would not seal shut and, in one case, the discovery that the crews that maintain the nation’s 450 intercontinental ballistic missiles had only a single wrench that could attach the nuclear warheads.

“They started FedExing the one tool” to three bases spread across the country, one official familiar with the contents of the reports said Thursday. No one had checked in years “to see if new tools were being made,” the official said. This was one of many maintenance problems that had “been around so long that no one reported them anymore.”