I did a bit of googling and wikipedia informed me that the pressurizer is just a vertical tank of sitting coolant water that directly connects to the reactor. Then electrical heaters in this vessel raise the pressure in the pressurizer by raising the temperature (since the two are directly related). What I don't get is how is this the best way to go about it? Your $coolant$ is being heated. I read that the temperature difference between input and output of the reactor vessel is $30^o C$. Intuitively, that seems kind of poor...
But that confuses me less than the following: if the whole point of a PWR is that the coolant/moderator is pressurized so that it cannot boil, wouldn't heating it up to hundreds of degrees C in the pressurizer make it boil!?
How is it that in a PWR, heating of the water in the pressurizer increases the pressure but doesn't cause boiling, but in something like a boiling water reactor, the coolant is heated directly by the reactor which increases the pressure AND the coolant boils? What differentiates these two? Both are just cylindrical vessels with a heat source in them, yet one causes pressure increase and no boiling, while the other increases pressure and causes boiling.
I'm not too knowledgeable about this because I'm not in this industry or field, I'm just a guy who likes to read about this stuff and this part didn't make sense to me. Thanks!