Navy has an extremely high bar for safety according to Navy itself, but accidents sometimes get classified for a couple of decades. It happened before, https://en.m.wikipedia.org/wiki/Hanford_Site for example.
The Hanford site is a horror show of the reality of how the US handles decommissioned nukes:
> The DOE later found water intruding into at least 14 single-shell tanks and that one of them had been leaking about 640 US gallons (2,400 l; 530 imp gal) per year into the ground since about 2010. In 2012, the DOE also discovered a leak from a double-shell tank caused by construction flaws and corrosion in the tank's bottom, and that 12 other double-shell tanks had similar construction flaws. ... Intermittent discoveries of undocumented contamination have slowed the pace and raised the cost of cleanup.
> In 2007, the Hanford site represented 60% of high-level radioactive waste by volume managed by the US Department of Energy[7] and 7–9% of all nuclear waste in the United States (the DOE manages 15% of nuclear waste in the US, with the remaining 85% being commercial spent nuclear fuel). Hanford is currently the most contaminated nuclear site in the United States and is the focus of the nation's largest environmental cleanup.
