Three Mile Island was nowhere near the catastrophe of Chernobyl. The area was certainly not shut down for decades.

"For more than 50 years, NASA's robotic deep space probes have carried nuclear batteries provided by the U.S. Department of Energy. Even the crewed Apollo moon landings carried nuclear powered equipment." https://www.space.com/13702-nuclear-generators-rtg-power-nasa-planetary-probes-infographic.html