ackermann t1_j05hyvx wrote on December 14, 2022 at 5:16 AM

Reply to comment by Robo-Connery in National Ignition Facility (NIF) announces net positive energy fusion experiment by Robo-Connery

Thanks! So, a basic question. Would a hypothetical large scale, commercial reactor work with a series of discrete pulses, or “shots”? Eg, fusion wouldn’t be happening continuously, but in pulses?

I imagine this would make them safer than fission reactors. If the reaction isn’t continuous, then it can’t “runaway” out of control, or melt down, right?

Robo-Connery OP t1_j06qeok wrote on December 14, 2022 at 1:56 PM

That is the design that they are working towards. Well NIF isn't really about a pathway to fusion power but if you are following a NIF-like design for power than it needs to be pulsed. It needs to be pulsed a couple of times a second before designs start to make sense (nif is about once a day).

Modern fission designs can also not melt down (search for Gen IV or gen V reactor designs), they are completely passively controlled and cooled.

In addition magnetic fusion devices can not melt down either, they might damage the machine if you turned them off (also JET makes a horrible bang if it is turned off early) but there is no risk to anyone, reaction stops the instant you turn it off.

ackermann t1_j08b62v wrote on December 14, 2022 at 8:09 PM

Cool thanks! So magnetic confinement devices do have continuous fusion then, unlike NIF style devices?

Robo-Connery OP t1_j08ddiu wrote on December 14, 2022 at 8:23 PM

The best ones are only matter of tens of seconds. ITER is meant to be 1000s but the ultimate goal is continuous operation. Nif and other icf machines are necessarily pulsed (because they are explosions).