Am I the only one that thinks the explosion was way to large for such a tiny bomb to cause?

You weren't placing a bomb, you placed a Fusion Pulse Charge - like the one Mr. Burke gives you to blow up Megaton in Fallout 3. That charge is designed to attach and remotely detonate a real nuclear bomb. Or reactor.

It was the reactor I believe, the bomb destabilized it.

It wasn't the bomb that caused the explosion, but the overpowered Nuclear Reactor that it blew up.

Not sure if it is the scientifically correct size of explosion for this reactor, but this is fiction.

Yes, but the reactor was off, so i guess it is a plot hole then? Also nuclear fusion tends to produce less radioactive waste then fission, even though the waste tends to be more radioactive, so the crater it leaves should be less radioactive.

Technically there shouldn't have been any explosion as nuclear reactors don't do that. They would just overheat, melt, and give off massive amounts of radiation. A nuclear reactor contains uranium fuel rods, not much more unstable plutonium

Actually i thought fusion reactors didn't use any form of plutonium or uranium. So the explosion should not have occurred at all if the reactor wasn't on, as fusion reactors are very hot.

A nuclear reactor is nothing more than a powerplant. Like any other powerplant it uses steam to power turbines that generate electricity. The only difference is they heat and vaporize the water using extremely hot rods of uranium instead of burning coal or some other fossil fuel. But the temperature of those rods will get higher and higher if not monitored and controlled. If that happens the rods will melt like any other metal, damage the containment vessel, and give off tuns of radiation. But it won't explode

One of the reasons I haven't completed the main quest in my second game is that I don't want to take out my favorite bridges and create a giant radiation storm zone in the middle of my map. In fact, if there was ever an argument for an Institute ending that would be it.

Well, we don't exactly know how the reactor or the fusion pulse charge specifically work, so I don't think we can really say it shouldn't have worked like that.

Fusion reactors don't have control rods, they use plasma to generate heat and the plasma is currently contained by magnetic field. If you disrupt the field it could explode as plasma is extremely hot, and would seek to expand out. The sun is a good example without gravity to hold it together it would blow itself apart. Some form of liquid is used to cool the reactor, and that heated fluid is used to heat water. The fusion reactor in the game is based off several test models in testing now.