Running that process in a power plant would not only eliminate the
danger of a core meltdown, it would also pretty much eliminate the
possibility of getting any nuclear power out of the plant.
The understanding behind your question is correct . . . Neutrons coming
out of one fission go on to get absorbed in other nuclei, and cause the
other ones to fiss. BUT . . . NOT every free neutron whizzing around in
the core material gets absorbed. Some of them enter another nucleus
and immediately get spit out. And some of them never get near another
nucleus at all. Of all the neutrons produced in one fission, only some
percentage go on to stimulate another one. So if each fission produced
only one neutron, then the whole process would completely run out of gas
in some amount if time, as the number of free neutrons dwindled and shrank.
