The word optimum only makes sense in context of limitations and assumptions, which are subject to change.

For the sake of argument, lets assume nuclear power is the safest option available given current technology.

That doesnt mean that no improvement is possible and we should reject alternative design that are even cheaper and safer poses no benefit.

Just because something is the best choice available to apple doesn't mean it is the best choice available to society.

I'm not saying the situation is inherently static. Rather, it's the most extreme case I'm aware of where the effort to reduce risk actually increases it.