BLEVE explosions are caused by a positive feedback loop between escaping vapor combusting and then feeding more heat back into a container, causing a further rise in temperature. CO2 isn't combustible, and if it were to vent, it would lower the temperature, not raise it.
200MWh is equivalent to about 860kg of TNT. That’s a pretty big boom if your pressure vessel fails catastrophically, even without any combustion.
According to other posters, liquid CO₂ can be stored at 5 atm pressure which is trivial from an engineering POW.