[AreaMan]

In a nuclear reactor, it takes large numbers of specialists and serious application of high technology to prevent reactions from running away. 'The big question we addressed was: when the uranium reached criticality, why didn't it blow up?' says Alexander Meschik of Washington University in St Louis, Missouri.

In water moderated reactors, like this one. Water temperature has an inverse coefficient of reactivity.

at least that is how it was explained to me in school. Which is why nuke boats run a little better with cold primary coolant.

[Robert A Cook PE]

See my comments on reactivity in Nbr 32 & 33.

True: Navy boats use the same principle: except Rickover classified our tech manuals so God couldn't sell the idea to the Russians.