Wasn’t the H-bomb (fusion) supposed to be way more powerful and unpredictable than the A-bomb (fission)? Kinda confused here and I’m certainly mixing bombs with energy production. But if you could give me the essential I’d appreciate it. Thank you.
In: Chemistry
Nuclear fission happens whether you want it to or not. What a fission power plant does is it works to control the rate of the fission reaction. But it doesn’t cause it. The fuel in a fission plant wants to be hot, and most of the effort and safety of a fission plant is trying to keep the fuel cool. In fact, the fuel heating the coolant is ultimately how power is generated. When safety systems fail catastrophically and a reaction is said to be in “meltdown” it literally means that the fuel rods have become so hot that they have melted. At this point, stopping a fission reactor is extremely difficult.
In a fusion reaction, the big problem that needs to be overcome is how to start the reaction and keep it going. A fusion reaction, while it can produce an extremely large amount of energy for a small amount of fuel, is very difficult to maintain. More importantly, if you put the fusion fuel on its own into a reactor, nothing will happen on its own. No reaction will happen under ambient condition, unlike a fission reactor. Most research reactors try to get the reaction going compressing and heating the fuel until it becomes a plasma. And then, maintaining the plasma takes a lot of effort as well. If any of these methods for heating or compressing fails, the reaction just stops. No explosion, no meltdown. Just the reaction stopping. This is a great inherent passive safety feature.
Long story short: most of the work in a fission reaction is in slowing down the fission reaction. Most of the work in a fusion reactor will be keeping the reaction going. If safety systems fail, a fission reactor will accelerate, but a fusion reactor will just shut down.
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