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Bill Gates To Help China Build Traveling Wave Nuclear Reactor
First time accepted submitter BabaChazz writes "Microsoft Corp. co-founder Bill Gates says he is in discussions with China to jointly develop a new kind of nuclear reactor. During a talk at China's Ministry of Science & Technology Wednesday, the billionaire said: 'The idea is to be very low cost, very safe and generate very little waste.' Gates backs Washington-based TerraPower, which is developing a nuclear reactor that can run on depleted uranium."
There's another reason they don't get used. The 'standard' reactors require enriched fuels. The same companies that sell the reactors also supply the fuels, or the enrichment services. It's basically vendor lock-in.
The ultimate question for all reactors is what they leave behind.
They can't help leaving behind fission products (that's where they get their energy from), which isn't too much of a problem, as it takes only about 300 years for them to decay to levels of radiotoxicity of natural uranium in equilibrium with its decay products.They will leave behind some Uranium, but this can still be used in other reactors.
The problem is mainly residual Plutonium, Americium and other elements, with half-lives of several thousand or tens of thousands of years, which require hundreds of thousands of years to decay to such levels. (Because of the very damaging high energy alpha decay, rather than lower energy and much less damaging beta and gamma decays.)
On the one hand non-fissle transuranic elements capture neutrons and interfere with the chain reaction, on the other hand capturing neutrons either splits them or eventually transmutes them into fissle elements. This turns them into fission products, which we can handle with reasonable confidence. The question now is: does the travelling wave in the travelling wave reactor provide enough neutrons to transmute and split the transuranic elements it breeds, such that the reactor as a whole reaches a stable equilibrium before the end of its operating time? Conventional reactors don't, because the chain reaction is stopped for lack of neutrons long before a stable equilibrium is achieved. Most breeder reactors do, but it depends a lot on how tight the neutron economy of the particular reactor is. And afaik (correct me if you know better or have access to specifications), the neutron economy of the travelling wave reactor is rather tight and might well be possible, that the wave leaves ever more transuranics in its wake as it moves, without ever reaching an equilibrium over the whole of the reactor.
Why is reaching a stable equilibrium before the end of operation enough? In this case you can add some additional transuranics at the start of operation and still reach the same equilibrium at the end of operation. If the amount you can add at the start (and still reach equilibrium) is larger than the amount left at the end of operation, you effectively reduced the total amount. Given that, you effectively solved the long-term problem of transuranic waste, by limiting its amount and eventually burning it.
The question is, can the travelling wave reactor do that or not? (There are other options ex post, but it is always best to not let the problem exist in the first place rather than dealing with it later.)
I work at a nuclear plant, we use NT4 for our Plant Process Computer. Service pack 5 btw.