[Age of Reason]

So if the Japanese reactors are so safe that even if the cores melt, they will be contained and the heat disspated by the molten core spreading out over a large but contained area, then . . . .

. . . why are the Japanese so desperate to cool the reactors down?

I mean, why risk the lives of the workers and instead just walk away and let the thing melt if there’s no harm in that?

[chimera]

Because typically in a defense-in-depth approach you want to do what you can to mitigate the effects prior to reaching another boundary of defense. If you can do reasonable things to limit the number of challenges to various layers of protection, your overall system reliability remains that much more robust.

Of course, if all else fails, you have to rely on the containment. That's why you have it. But if you can do things to avoid challenging it, and those things are reasonable to try, then you likely will make the effort.

[mvpel]

I mean, why risk the lives of the workers and instead just walk away and let the thing melt if there’s no harm in that?

There's a big distance between "no harm" and "no 'China Syndrome.'"

They have a duty and a moral obligation to limit the harm and the future expense and damage as much as possible.