How many people died or had their lifespan seriously reduced by Three Mile Island?
Based on my research? Undetectable.
No one died during the event itself and any potential increase in cancer vanished in the normal randomness of cancer.
The reason we remember Three Mile Island as a terrible catastrophe is entirely because of how the media at the time reported it.
"Workers are being exposed to so much radiation over their shifts, the safe daily dose is so much less"
Maybe, but there are ways to protect workers from radiation while working lol. No mention of that in the Times.
"Government Experts say it's safe, but these other experts have numbers about how terrible it is!"
Those other experts ignored half a dozen+ other factors and the government experts did have numbers of their own lol.
I did a paper on it like threeish years ago, the actual scientific papers couldn't find any actual damage caused by Three Mile Island, the News(using New York Times as an easily located source) insisted the sky was falling.
EDIT:
It also had a containment structure, unlike Chernobyl.
Fukushima is the fault of the Yak contractor putting the back up diesels in the basement in a tsunami zone.
At the time of the Plant construction they hadn't found any records of a Tsunami nearly that big in the region, then they found records of something smaller than what actually hit but bigger than they'd previously planned and fixed it to handle waves a bit bigger than that. Then they found records of a Tsunami about as big as what actually hit it, the plans to fix it were literally in committee when the Tsunami hit. The plant as it was still would have been fine except for the earthquake, followed by the Tsunami which STILL would have been fine except for how damaged transport infrastructure got delaying things for too long.
Fukushima was nearly fine, it was a confluence of problems any one of which wouldn't have created disaster, any two of which probably wouldn't have, and all three of which still didn't make nearly as much of a problem as people say fossil fuels are.