[wideminded]

"By the time the Reagan realized it was contaminated and tried to shift location, the radioactive plume had spread too far to be quickly outrun.

“We have a multimillion-dollar radiation-detection system, but . . . it takes time to be set up and activated,” Cooper said.

In other words it wasn't turned on.

[Revelation 911]

In other words it wasn’t turned on.

……..near a faulty reactor

[Yorlik803]

First of all, you assume this regime cares about the people charged with defending it.
2nd, the Ship was named for a great American, Maybe it was a petty way of punishing it.
3rd....I bet the Capt was under orders to save money and not turn on the detection equipment.
Those poor sailors....Pray for their recovery.