A near-disaster at a federal nuclear weapons laboratory takes a hidden toll on America’s arsenal

Repeated safety lapses hobble Los Alamos National Laboratory’s work on the cores of U.S. nuclear warheads

Part Two

Safety problems at a Los Alamos laboratory delay U.S. nuclear warhead testing and production

A facility that handles the cores of U.S. nuclear weapons has been mostly closed since 2013 over its inability to control worker safety risks

Part Three

Light penalties and lax oversight encourage weak safety culture at nuclear weapons labs

Explosions, fires, and radioactive exposures are among the workplace hazards that fail to make a serious dent in private contractor profits

Part Four

More than 30 nuclear experts inhale uranium after radiation alarms at a weapons site are switched off

Most were not told about it until months later, and other mishaps at the Nevada nuclear test site followed

Part Five

Repeated radiation warnings go unheeded at sensitive Idaho nuclear plant

The inhalation of plutonium by 16 workers is preceded and followed by other contamination incidents but the private contractor in charge suffers only a light penalty

Part Six

Nuclear weapons contractors repeatedly violate shipping rules for dangerous materials

Los Alamos laboratory’s recent mistakes in shipping plutonium were among dozens of incidents involving mislabeled or wrongly shipped materials associated with the nuclear weapons program

Senator cites Center for Public Integrity probe in questioning safety practices of weapons contractors

McCaskill letter challenges a federal agency’s commitment to safety oversight and enforcement

Los Alamos laboratory director announces he will step down

Charles McMillan, who presided over controversial missteps and higher budgets, says he will retire at year’s end

Energy undersecretary wants nuclear safety reports hidden from public

Independent watchdog agency entertained the idea

Chairman of nuclear weapons oversight agency steps down amid internal turmoil

Morale plummeted after Republican Sean Sullivan proposed to Trump that the agency — a frequent target of defense contractors — be shuttered