Tuesday, September 13, 2011

Molten Salt Reactors - the solution to our power question.

If you have read my blog, you know I am a proponent of nuclear power.  Before I have talked about how coal is far worse than nuclear.     But another reason is that the newest designs are far better than the current ones.

We are now using Generation 3 - the ones currently being planned are called "3+".  The next design is called Generation 4.   It is a radical change from Generation 3.  Generation 3 uses solid nuclear fuel (Uranium and/or Plutonium) physically placed together, with graphite control rods in between them to slow down the reaction.   Generation 4 takes the nuclear material (thorium)l, chops it up into small pieces, and mixes it with salt.  Then they heat up the salt so that it is molten and flows.

Put enough of the molten salt in one place and you get a reaction.  If you keep it spread out, no reaction.  Being molten, to put enough in one place, you just pour it into a small container - ideally in the shape of a ball.   Or to keep it spread out, you can pour it into a web of small, narrow tubes separated by some lead.

Best of all, they can put a refrigerator near the bottom above a drain.  With the refrigerator on, the drain is cold and the molten salt freezes into a solid plug, blocking the drain.  When you have a power failure (and/or a melt down), the refrigerator turns off, the salt plug melts, and the molten radioactive salt flow out into a safe drainage system that physically can NOT cause a melt down.

Note, a meltdown is what caused all the serious problems with nuclear plants.   

But there are some downsides.   First, it is not a very good 'breeder' plant.  So to make a lot of these plants quickly, you have to dig up and purify your fuel, instead of simply getting it for free from running the plant.  That also means you can't use it to make nuclear weapons.  Second, the plants need a lot more maintenance.  The salts can under certain circumstances form acidic gasses - some of which may be radioactive.   But as there is no heat buildup, there is never an explosion.  Just slow leaks of acidic gas, that in the worst cases might be radioactive.

But this design does negate almost all of the problems that Japan had.  Their design needed people to keep it safe and no one wanted to send people into an unsafe area.

The Molten Salt Reactor needs people to keep it working, but without people, it shuts down safely, automatically.  No water needs to be pumped to keep it safe.  Electricity is needed to keep it working, not to shut it down safely.

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