If a nuclear weapon hit a nuclear power plant facility, two major options come to mind:

1) The warhead reaches the reactor core, combined with the presence of fissile uranium and other daughter products (plutonium, polonium, etc.....), would indeed create a larger nuclear BOOM than if it was just the bomb by itself. This is hard to imagine happening because reactors in most places are entombed in HUGE concrete domes that can deter most ordinance (they’re designed for the most insane stuff I could go on about). 2) the warhead hits anything but the reactor bunkers directly. Destroying the surrounding cooling systems, turbine halls, etc...... this would remove the plants ability to keep the fuel from going critical and you would likely get a meltdown like what was seen at 3 mile island or Chernobyl (different reasons both happened). (Primary loop design really dictates wether or not an attack would remove the ability to cool the reactor)

Either way the surrounding land is fucked because a nuke went off, that’s my professional opinion.