Nuclear weapons cook off? Doesn’t seem very likely.
The danger would be that the fuel in the 16 ICBM’s would cook off in one big boom. That explosion would send the nuclear weapon material in the 64 or more warheads on top of the ICBM’s far and wide, although not in a nuclear explosion.
Fortunately since they seem to have put the fire out by flooding the dry dock there doesn't seem to have been much danger of the missile fuel exploding.