No. To make a good nuke blast is a very demanding engineering job plus lots of resources. The ultra extreme physical conditions of high temperature and pressure can not be easily created e.g. by an attack on a reactor, but rather very accurate precision engineering taking care of many calculated and simulated and tested conditions ALL met flawlessly, for a workable WARHEAD DESIGN then can seen Einstein's E=MC2 (sq) Blast. Otherwise just a nuke fuel spill and long term pollution like Fukushima, not a giant mushroom cloud.
Warheads are designed to detonate and dispense all nuke energy within single blast. Reactors are designed to dispense regulated amount of nuke energies over few decades. But for both, if just merely struck by another blast, will not be a big blast.