Comment by comrade1 | Hacker News Reader

Comment by comrade1 | Hacker News Reader

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Something I don't understand about fusion, doesn't it also produce radioactive waste? Does the containment system get irradiated with high-energy neutrons?

Ok, I looked it up myself: https://en.wikipedia.org/wiki/Fusion_power#Waste_management

It does produce nuclear waste, but with a short half life. The waste is more radioactive than fission waste, but will be pretty much gone in 500 years.

Since it does produce radioactive waste, could fusion also make large areas of the earth uninhabitable like fission when there's an accident?

I used to prefer fission and fusion research but seeing what happened in chernobyl and fukushima I had seconds thoughts, and now seeing how well renewables are doing I don't care for fission and fusion any longer.

Funny story, in Switzerland they release water from mountain reservoirs during the day to produce electricity and sell the surplus to France and Germany at a high price, and then at night they buy nuclear-produced electricity from France at a fraction of the cost and pump the water back up into the mountains to repeat the process the next day.

Fusion accidents are much less likely - they need to be constantly supplied with new fuel for the reaction to continue. If they get hit by an earthquake / terrorist attack / other emergency, the natural tendency of the system is to stop moving things, including the fuel, which means that the source of energy is immediately removed, and the danger with it. At worst the reactor itself may get destroyed, but containment techniques should guarantee minimal radiation escaping to the environment.

Fission on the other hand requires a large quantity of fuel just to get the chain reaction started, so if things go wrong, you'd better have a robust cooling system, because nothing is going to stop that fuel from producing lots of waste heat. The fuel melts and escapes containment, radiating surrounding groundwater and the general environment. Even without catastrophes, fission results in lots of irradiated coolants and 'spent' fuel that is still hot enough that it needs to be stored in water for years after it leaves the reactor.

There are some experimental IV generation Fission Reactors, which burn the entirety of the nuclear fuel leaving just lighter radioactive elements with shorter half-life. Regarding safety, the Molten-salt Reactor also of IV generation, allows for non catastrophic failures since if the reaction goes out of control, the salt solidifies and stops the reaction instead of exploding by the increased pressure. The downside is that reactor becomes a radioactive rock.

what I don't get is, isn't "highly radioactive" waste dangerous because it puts out so much energy? So..... maybe we should just plop that waste back into a fission reactor, then?

I think this is the point of some 'breeder' reactor designs. Much of the current waste that is in storage could actually become fuel.

Just don't fake the test data. http://news.bbc.co.uk/1/hi/world/asia-pacific/639023.stm

Think about it this way:

Lots of stuff can burn and produce heat, but you don't just put any old flammable thing into your car, you use a specific type of refined petroleum that has well known properties that you can design an engine around.

Likewise, while lots of radioactive material can put off heat that can be used to drive a turbine, by using a specific blend of U235 and U238 the whole system operates in a controlled and well understood way.

There is a program to blend in plutonium from decommissioned nuclear bombs as a fuel for reactors, but it is fairly complex and probably wouldn't be done except for security / political reasons.

There are also designs on the drawing board for something akin to a garbage incinerator, the primary purpose would be to eliminate waste, but much or all of the energy to do so would come from the waste products themselves.

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