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The major advantage of fusion is that it can be sustained for a long, long, long time, after any terrestrial source of uranium or thorium will have run dry. Deu

by scythe 15y ago

The major advantage of fusion is that it can be sustained for a long, long, long time, after any terrestrial source of uranium or thorium will have run dry. Deuterium is an effectively inexhaustible resource, and as long as there are neutron fluxes there will be a source of tritium as well. Neutrons are not really more penetrating than other sorts of radiation, just differently penetrating, as they are blocked not electrostatically (by metals, as in the case of alpha/beta/gamma radiation) but by nuclear interactions (i.e. absorbed by atomic nuclei) requiring the use of different sorts of materials to block them (aka neutron modulators). It is largely a solved problem. >It's technically true, but the process is very expensive Well... yes, heavy water costs a good $600 / kg for the super-pure sort used in nuclear reactors. Still, this isn't really more expensive than plutonium or enriched uranium -- I can't get cost figures mostly because civilians like me can't buy plutonium, surprisingly. Tritium is a lot more expensive mostly due to a current lack of production and use, but it can be produced easily from lithium-6 or potentially from heavy water itself. Fusion, however, has a few significant advantages: The only radioactive product is tritium itself: a beta emitter with a short half-life which, unlike radioactive strontium and iodine, has zero potential to accumulate in biological systems and the environment is already full of the stuff thanks to cosmic rays. The reaction is not a runaway -- if the confinement somehow fails, fusion stops instantly. This is not great to harp on because nuclear fission is still one of the safest sources of energy, statistically speaking. The fuel is ubiquitous -- there are no terrorists selling heavy water a la Back to the Future; both deuterium and lithium are recovered from seawater, and doing so is far easier than recovering uranium from seawater. This means far less trade issues and no Iraq War type stuff in the interest of securing the Earth's supply of heavy water. Uranium, by contrast, is distributed unfairly throughout the Earth. The fuel is inexhaustible -- at last count, if producing tritium from deuterium can be achieved, the Earth's supply of heavy water will last for several million years. Even the most starry-eyed predictions from thorium only have around a 10000-year supply prediction. ( http://en.wikipedia.org/wiki/Energy_development#Nuclear http://en.wikipedia.org/wiki/Energy_development#Nuclear is the source here -- Wiki claims 150 billion for deuterium alone, but I'm assuming our energy usage will keep increasing)

yaakov34 15y ago
So according to you, the major advantage of fusion is that it will take us beyond the next thousand years, which is the amount of time that we can supply our needs with fission (I am not taking maximum numbers). Let Dr. Prager say that in his article, then. He won't, because it will take away any sense of urgency from supporting his research; there are hundreds of years before it becomes necessary, and there is no reason not to leave this for people in the year 2371. I think his motivation is good, in the sense that he has real scientific curiosity about this, but it's still unethical to bamboozle people with talk about "harnessing the power of the stars" and "fuel from seawater", neither of which is really the point here: the stars are irrelevant, the tritium doesn't come from seawater in any meaningful sense. Current proposals for fusion reactors are also uneconomical, which is why people invent hybrid fusion-fission economies. > This is not great to harp on because nuclear fission is still one of the safest sources of energy, statistically speaking. Then don't harp on it. With immense shielding and cooling mass that needs to get irradiated in current fusion reactor designs, the safety is oversold; and some of that mass will get activated, since you can't economically make it only of materials that won't be.

by scythe 15y ago

yaakov34 15y ago

So according to you, the major advantage of fusion is that it will take us beyond the next thousand years, which is the amount of time that we can supply our needs with fission (I am not taking maximum numbers). Let Dr. Prager say that in his article, then. He won't, because it will take away any sense of urgency from supporting his research; there are hundreds of years before it becomes necessary, and there is no reason not to leave this for people in the year 2371. I think his motivation is good, in the sense that he has real scientific curiosity about this, but it's still unethical to bamboozle people with talk about "harnessing the power of the stars" and "fuel from seawater", neither of which is really the point here: the stars are irrelevant, the tritium doesn't come from seawater in any meaningful sense. Current proposals for fusion reactors are also uneconomical, which is why people invent hybrid fusion-fission economies. > This is not great to harp on because nuclear fission is still one of the safest sources of energy, statistically speaking. Then don't harp on it. With immense shielding and cooling mass that needs to get irradiated in current fusion reactor designs, the safety is oversold; and some of that mass will get activated, since you can't economically make it only of materials that won't be.