https://en.wikipedia.org/wiki/International_Nuclear_Event_Scale
One problem is that many of the accidents are put too high on the INES scale.
TMI resulted in no radiation deaths or release of any material. Yet is it a 5. By the definitions, it should be a 3. Fukishima is a 7, the same a Chernobyl! It should also be a 5 or 6. No direct deaths. They hype the 1600 deaths from "evacuation", which also seems way overstated.
On the other hand SL-1 is historically kept low at 4. It should be a 5, maybe a 6.