Chernobyl-style designs have been known to be a less safe design for as long as they have been around. They are weapons-production reactors scaled up for power

Chernobyl-style designs have been known to be a less safe design for as long as they have been around. They are weapons-production reactors scaled up for power production, without any of the design changes to add inherent safety that were made for even 1950s-era Western designs. Chernobyl belongs in a category all by itself for that reason. TMI was certainly an economic issue, but it was never a public health concern, even in the middle of the meltdown. In fact TMI was a validation of the public safety concept of nuclear power plant containment design; despite suffering a full as-bad-as-it-gets meltdown there was only a minimal release of radioactive gases to the environment. As far as Fukushima, there were actually two different sites, Dai-ichi and Dai-ni. The Dai-ni reactors were a very slight spec bump up from the Dai-ichi reactors due to being started later. Both sites suffered the same earthquake & tsunami; all of the operational Dai-ichi reactors melted down, none of the operational Dai-ni reactors suffered damage. The disasters were beyond design basis for both. So even 40-50 years ago they were continuing to make design improvements to increase the safety margin of nuclear power to account for "unknown unknowns". Meanwhile even today coal plants pump carcinogenic exhaust directly to atmosphere and people judge it as an acceptable tradeoff because the damage is constant.