Superconductors lose their superconductivity if they are put in a too strong a magnetic field. This includes the field generated by current passing through them. The field generated by 40 TW of electricity is insane.
That. Wasn't me...
Thus, the total fuel injection rate in ITER is going to be about 0.16 grams per second (or,
according to this source that is probably far more correct, not having done this on the back of their hand while having breakfast, 0.26 grams per second). Note that this is a complete speed of fuel injection, not the rate of the fuel burn. For that, you'll need to divide by at least two, likely more. So, to have a 386 grams burnt per second? Take ITER, upscale it at least 1000 times. Now, try to imagine that thing. It's
HUGE.
Not really. I'll admit I don't know the first thing about fusion technology however it's important to remember that not only did they shrink fusion technology to the point it fit on spaceships they, from what I understand, did it before they found Mass Effect technology.
So I can absolutely see them having 80TW of power generation in combat.
That is why Arc reactors are so revolutionary. The power density in them is insane.
Our 40TW reactor is 8,000 times more powerful then our standard Arc Reactor. So assuming it scales by volume, which the number seems to imply, that's form an Arc Reactor 2m to 3m in diameter.
Lets assume for arguments sake that the front of the Everast is 10m by 10m (which seems really small in comparison) by 888 (size of the main gun, the actual ship would be bigger) that gives her a total volume of 88,800 cubic meters.
If we assume that 5% of the ship's volume is spent on the reactor(s), reasonable in my opinion given that it's basically a ship built to fire the main gun, that gives a volume of 4,400 cubic meters.
The 40TW arc reactor, assuming a perfect sphere which it isn't, has a volume of 113 cubic meters. Double that for two reactors and it's 226 cubic meters.
That makes the Arc Reactor 19.46 times more size efficient and that's assuming a really narrow ship. Especially since they mention that on the Kilamanjaro the broadsides are 40% of the ships width.
So lets say we up use the Nimitz as the scale. A Nimitz class is 332.8m long, 76.8 m wide and 12.5m high. That's a ratio of 23% width-to-length and 4% height-to-length.
If we assume that the Everest is 900m, 888m is the length of the accelerator after all, that gives a width of 207m and a height of 36m for a total volume of 6,706,800 and a Reactor volume of 335,340 cubic meters or 1,484 times larger then the equivalent in Arc Reactor.
As a side note ITER is,
apparently anyway,
840 cubic meters so a thousand times that is 840,000 cubic meters. ~260 years and
Space Magic Eezo is more then enough to justify a top of the line military reactor been 40% the size.