Amount of Plasma [g] in nuclear fusion designs

  • #1

Summary:

What is the typical mass of the plasma (in typical working configuration) in current nuclear fusion reactor designs?

Main Question or Discussion Point

Hi everyone,
I am trying to figure out the following question:
What is the typical mass of the plasma (in typical working configuration) in current nuclear fusion reactor designs?
https://en.wikipedia.org/wiki/ITER: "...plasma volume of 840 cubic meters..."
So all I need is the plasma density. Enter the "Lawson criterion" and the "triple product"...all very interesting reads, but I couldn't find any values for, let's say: Wendelstein, ITER and a "commercially viable fusion reactor".

Reason why I'm asking: I strongly suspect the actual "working mass" of plasma in a fusion reactor to be really low as compared to, say, the amount of Uranium in a fission reactor. 840 m^3 filled with air would amount to 1071 kg. This is the amount of air roughly rushing into the core of a fusion reactor (ITER type) if push comes to shove and the core containment breaks. Very, very cold air, and lots of it, seems to be the perfect "emergency off" button build into the very design of fusion reactors - as opposed to fission reactors, two of which (in Tchernobyl and Fukushima) are currently on their (slow, but steady) way towards the center of the planet.
If m(plasma) << m(air), a "Super-Accident" in a fusion plant would be a fly's burp as compared to the same mishap in a fission reactor. Or am I completely wrong somewhere?
 
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Answers and Replies

  • #2
Drakkith
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I don't know the exact plasma density, but I know that you are correct in your understanding that the amount of plasma is very, very small. The total energy released by the plasma in the event of complete containment loss would perhaps scorch the inside of the reactor and damage some sensors. That's it.

840 m^3 filled with air would amount to 1071 kg. This is the amount of air roughly rushing into the core of a fusion reactor (ITER type) if push comes to shove and the core containment breaks. Very, very cold air, and lots of it, seems to be the perfect "emergency off" button build into the very design of fusion reactors
That's not even necessary to be honest. Any significant change in the reactor's internal conditions away from just what it needs to sustain fusion would immediately halt the reaction. You could literally just hit a big red button to turn the power off to the electromagnets and all you'd get is what I wrote above. Some light damage to the internal surface of the reactor and some damaged sensors.
 
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