So the force needed to break a reactor open would be, on its own, much more dangerous than what comes out of the reactor itself.

I suppose that for the radioactive methane (the carbon of the compound being 11c), detailed dispersion and dose calculations will probably be needed at some point. I know that in larger cities substations are located underground and next to large, tall buildings. If you have a gas release in a location like this, I could see some issues coming up, but that I all depends on how quick the gas rises and how fast it disperses into a harmless concentration. If the numbers aren’t favorable, something extra will have to be thought up and implemented to mitigate the issue.