To put a number on it, linear no threshold models predict ~130 deaths as a result of the radiation (and are known to over-estimate lethalities at low doses).
Around 50 people a year die while clearing snow in Japan, so it's ~ twice as dangerous as shoveling snow in worst-case predictions.
LNT is not known to over-estimate lethalities at low doses. The actual situation is that the predicted deaths at low doses occur at such a low rate that the signal cannot be detected above the noise. That doesn't mean the prediction was wrong, just that it cannot be verified. It's possible (as in, consistent with evidence) that LNT under-predicts deaths at low doses.
Even if LNT would under-predict it is still a rounding error in the big picture of the tsunami disaster.
And, let's put it straight: LNT is scaremongering fiction. People who live in Ramsay, Iran, are exposed to higher level of background radiation that n what is allowed for nuclear workers. Yet, there is no elevated levels of cancer or birth defects, not is there a shorter lifespan for people living there either.
Epidemiology is a very blunt instrument. The data you mention there cannot be used to reach the conclusion you are trying to reach, since confounding effects cannot be excluded (and because the doses they receive can only be estimated, not actually measured). Yes, radiation biologists know all about those people and have judged that evidence as part of a larger picture.
The main reason is a combination of negligence by the owner of the plant and not enough enforcement of standards.
The fukushima powerplant was known to have sea wall lower then required and as such was vulnerable to a tsunami (this was known for quite a long time)
Combined with backup power in the basement (also against standards)
For an example of what happens to a reactor build according to safety requirements see the onagawa nuclear powerplant
The Chernobyl plant had known construction defects that could impair safety. These things would prevent a western plant from starting operation, but did not stop the Soviet plant from beginning operation:
They did not even have any automated safeties in place, because their philosophy was “faith in the worker” while the western philosophy is “humans are fallible”:
They then ignored their own safety procedures when operating the plant, which ultimately is what caused the disaster.
Saying that Soviet designs being in the same generation as western designs makes them equally safe/unsafe is quite wrong when you look at the details. The Chernobyl nuclear power plant was one mistake after another.
That said, the plant was designed by a country that shot down a civilian airliner that had strayed into their airspace due to a navigational error, when they knew it was a civilian airliner:
They had no regard for human life, so of course, they built things that are incredibly unsafe. There is no end of examples of them simply not caring about human life.
