green nuclear power plants

I consider nuclear power a relatively green and safe power source. This due to the fact that power plants running on coal spew out enormous amounts of carbon dioxide during normal production, but nuclear plants only pollutes during an catastrophic event due to malfunction. Added to this is that globally 10.000 people die yearly in coal mines and there is an estimate that only in the united states some 23.000 people per year die due to air pollution from coal-fired power plants.

But reading an article in Wired the other day, really made my head spin. They painted up an picture that made a “new” (It’s not really new, first experiments was made in the 50’s. Experimental reactors where running in the 60’s!) reactor look like the holy grail in solving our energy needs.

It’s a nuclear reactor burning thorium instead of uranium or plutonium. Thorium is much more abundant than uranium and it does not need expensive enrichment. That means you can use all the thorium you mine. When using uranium in a nuclear power plant you only use one specific isotope and this is normally 3-5 % of the ore. So most of the uranium mined is useless for generating power.

You might say what about the storage of the waste from the reactor? The radioactive waste from a conventional reactor needs to be stored for 10.000+ years. And that is quite a challenge…

The neat thing is that since thorium is a lighter than uranium the waste is of a completely different nature. It “only” has to be stored for a couple of 100 years. And if that is not good enough, if we mix the waste from our current reactors in the fuel it burns up generating energy and transmutes into short lived isotopes!

Too good to bee true? Whats the catch?

First of all it is a more complicated process, the fuel get’s polluted and looses efficiency over time, so there need to be a process to remove these pollutants. But the rest of the “catches” are what normal people would call features. The fuel is harder to ignite which means it is safer, much less risk of a reactor meltdown. The waste is polluted with a uranium isotope that makes it unsuitable for nuclear weapons. And one of the biggest problems is that the nuclear industry is not interested. Why not? Well their business model is largely built on enriching uranium and selling fuel to the reactors. And thorium based reactors does not need any enriched fuel, just dig it up out of the ground, clean it and start running your reactor. Yes quite simplified, but truth is that the producers of nuclear fuel will have to find other ways of earning money.

So if these reactors was running in the 60’s how come we don’t run them today? Some cynics say it’s due to the fact that they do not produce plutonium that could be used in nuclear weapons. But this is not really true, since most commercial reactors produce an isotope of plutonium not really suitable for weapons. The real issue was time to market. In 1973 the Arab states cut off oil supply to the west. So the US decided to lower their dependency on oil, and that quick. That year, the US nuclear industry signed contracts to build a record 41 uranium based nuclear power plants. So all the money and research went into uranium based fission.

But India wen’t in another direction. Since they where developing a nuclear weapons arsenal they where outside the non-proliferation treaty and where largely excluded from trade in nuclear plant equipment and fuel. Also they lacked indigenous uranium, but have 12% of known thorium deposits in the world. So they started developing a nuclear fuel cycle using thorium. And are today running a hybrid using conventional reactors to ignite the thorium.

But these reactors still generate a large amount of regular long lived nuclear waste. The really cool reactors is called molten salt reactors (MSR). These work by pumping a molten flouride salt containing thorium and some uranium (or waste from regular reactors) through the reactor. This liquid is then continuously cleaned from radioactive pollutants. The pollutants have the nice property that when you store them for about 10 months they turn into fuel that is feed back into the reactor.

So while some people argue about the IPCC and who is right or wrong in climate gate (Sorry in Swedish) and others are discussing how to get the world united on carbon dioxide emissions (Also in Swedish), why don’t we start by solving the engineering issues with the thorium fuel  cycle and start replacing coal based electricity with green energy from thorium.

An extensive article about thorium reactors can be found in an 2006 issue of cosmos. More in depth information about thorium and thorium reactors can be found at the world nuclear association.

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