However, many operators didn't want to spend the money, which is why Fukushima didn't have a PAR at the time of the accident. The problem with Fukushima is that I fear we do not learn from accidents. Otherwise, Fukushima wouldn't even have been in operation at the time of the accident as it is an old reactor model well past its design life. The location was, as we have known before the accident, poorly chosen. Safety measures, such as PARs, seawalls and properly redundant power supplies were skipped or badly implemented due to the cost involved. All this was known before the accident, however neither the operator nor the national oversight took any action before it was too late.

Seems we are on a global level not very much learning from incidents. These are common (mandatory?) in Germany and colloquially named “Töpfer-Kerze” after the minister who had them installed: https://de.m.wikipedia.org/wiki/Reaktorsicherheit#T%C3%B6pfe... Klaus Töpfer was responsible for nuclear security from 1987-1994. This would have been the time to learn.