Well, I can still beat you to it, you know
The problems there are:
1. The containment failure consequences are too complex. I'd stick with a direct loss of some population, fallout and unhappiness from Nuclear Plants. Don't overdo it.
2. Doing things such as 1 angry in a city for 5 turns sound simple, but actually require Python. It's easier to do 1 angry which will last for 10 turns on Normal speed.
3. You can only "freeze" one unit through regular XML event editing. Freezing any more units would require Python.
4. The "50% lower chance of event recurring" won't work. You can make something similar, but it won't really work too well. It's easier to set up a "higher chance of event recurring" than the opposite.