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Under Our Feet

September 8, 2017
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Of all the alternatives to fossil fuel, nuclear power has the greatest potential to meet the rising global demand for energy, as the yield dwarfs the yield of all the others combined. It is, after all, the force that powers the  universe.

Fusion

big-bomb
A really BIG bomb

Nuclear energy is generated by the curious phenomenon that there is a slight difference between the mass of the nucleus of an atom and the sum of the masses of its parts. When two light nuclei fuse into a heavier one, or when a heavy nucleus breaks apart, that difference is converted to heat. Fusion generates much more heat than the opposite process, know as fission. It is what powers the sun and all the other stars. It is so hot, in fact, that as yet there is no way to contain it. We’ve only been able to use it to build a really big bomb. Big deal.

 

Fission

So we’re stuck with the much cooler process of fission to run our nuclear power plants. And even then there is the occasional melt-down. Moreover, when a heavy nucleus breaks apart, the components can recombine any which way. Fission, therefore, produces a wide range of byproducts, all of which are highly radioactive. So are the depleted remains of the starting material, usually uranium.

Nuclear waste is hard to dispose of safely, because it takes a while for radioactivity to decay to a harmless level. Depending on the element, we’re talking between thousands, millions and in the case of uranium, even billions of years.

So far, the best idea is to put it somewhere deep, either in water or underground. Neither of those approaches is fail-safe. Given enough time, water will work its way through anything, taking the radioactivity along for the ride. If you bury it underground, it better be in a place which is geologically stable, where the earth does NOT move. Those sites are quite rare and what there is of them will fill up soon, once the nuclear waste now temporarily stored near the power plants is carted over there. And we’ll just have to trust the geologists’ assertion that those places are an exception to the earth’s usual shiftiness and the sky won’t come a-tumbelin’ down.

Yucca-Mountain
Yucca Mountain: as stabile as they come…

Too Hot To Handle

On the other hand, the only byproduct of the fusion of hydrogen nuclei, as happens in the sun, is helium. Helium is chemically inert and useful in many ways, for example as coolant for superconductors. Much more energy, no hazardous waste, all good. Except for the containment problem.

The most heat-resistant material known has a melting point of about seven thousand degrees Fahrenheit. Impressive, but not measuring up to the millions of degrees involved in fusion.

So the focus is on technologies that keep the heat away from the walls. One widely tested approach is to cage the hot plasma in magnetic fields. There is also promise in a method invented at the Differ energy institute in the Netherlands, where the inside of the reactor wall is coated with a thin film of liquid tin and lithium. When the temperature rises, some of the liquid metal evaporates, forming a thin gas cloud, which acts like a heat shield. Conversely, if the temperature drops, the metal becomes liquid again allowing the temperature to rise.

Not So Fast…

Columbus’ egg, however, is far from boiled. In both cases, the technology involved is very complex. It will be another thirty years or so before the Differ test reactor comes online.

Columbus-egg
Columbus balancing the egg

It is a race against time. As things are, with the fossil fuels and the global warming and all, there will be no ice left by the end of the century and Houston will be even deeper under water than it is now. But if we put our minds to it, we stand a chance to win.

Lithium
Lithium

Lithium is very useful in many other ways. It makes for great rechargeable batteries, for instance. It also gives new spark to people who are chronically depressed. However, exactly because of its many uses, lithium is getting in short supply. The biggest deposits are on the west coast of South America, in the high Andes. Today, these formerly desolate plateaus are crawling with lithium prospectors.

Lithium dissolves in water, so they pump up groundwater to extract the mineral. It may come out the other end heavily polluted, but the locals don’t worry too much about it. They are among the poorest people on Earth and they see it as a chance to better their lives. Hey – they’re going to be on top of the world by the end of the century.

lithium-mine-andes
Lithium mine at Salinas Grandes, Argentina

 

(Broadcast 4:53)

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The Weekly Green is a KXCI mini-program on environmental topics from Southern Arizona and the rest of the universe. The program airs on Monday 5:55 PM, Tuesday 4:55 AM, Wednesday 9:55 AM & 5:55 PM, Thursday 7:55 PM and Saturday 9:55 AM. First airing is usually Tuesday at 5 am.
Please email inquiries, suggestions and comments to TheWeeklyGreen@KXCI.org or post them on the Weekly Green Facebook page.

TAGS
alternative energy,   bomb,   Energy,   fission,   fusion,   lithium,   nuclear,  

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