You are ignoring that the plasma would ignite the O2 in the air. You are also ignoring what happens when several hundred MW of energy (at about 1,000,000C) under pressure is released instantly. Anytime you have a powerplant with enough energy to be economically viable, releasing that energy at once will be a problem. Even FF PPs can explode quite violently.
> You are ignoring that the plasma would ignite the O2 in the air.
What does this even mean?
> You are also ignoring what happens when several hundred MW of energy (at about 1,000,000C) under pressure is released instantly.
If you have a gram of hydrogen at a million degrees, it can continue putting out several hundred MW for about a fiftieth of a second.
Even if it somehow gets outside the machine with no heat loss to the structure, by the time it mixes with a few cubic meters of air it'll be down to 1000C or less.