In 1971, General Electric designed, built and delivered the first, now-exploded, Mark 1 reactor at the Fukushima Daiichi nuclear plant and that design was also used for four of the other five reactors.
Whistleblower Dale Bridenbaugh, a former engineer for GE, exposed a critical flaw in the reactor design that was so bad, he recommended all Mark 1 reactors be shut
down to repair them. This didn't happen. Then, as now, profits and protection of nuclear business were put ahead of safety and the protection of people.