The core catcher will be designed such that the fuel will be retrievable once it is safe and prudent to do so. Leaving it there to me would be equivalent to sticking your head in the sand.
Bueno, I haven't heard a single "expert" on TV mention the "core catcher". You're the only one I've read anywhere that mentions it, so I googled, and this is what I found:A popular blog post entitled "Why I am not worried a about Japan's nuclear reactors" claims that meltdown at Fukushima I would be contained, as a last resort, by the reactor's core catcher.
However a comment purporting to be from a young Japanese Atomic Energy Agency researcher claims that Fukushima I has no core catcher:
http://morgsatlarge.wordpress.co...
Fukushima I was built in 1970 and the earliest reference to core catchers that I can find is this 1978 patent.
http://www.patentstorm.us/patent...
It seems unlikely therefore that a core catcher was installed, and since they go underneath the reactor I would assume they are not easy to retrofit. Does anyone have a definitive answer?