A New Class of Nuclear Reactors

prunedude tips this quote from a post at Freakonomics about Japan's nuclear crisis: "The folks over at IV Insights, the blog associated with Nathan Myhrvold's Intellectual Ventures, point out that it was the complete loss of power that disabled the cooling systems protecting the plant's reactors. Which raises the question: Is there nuclear technology that could withstand such a catastrophe? Possibly. TerraPower, an Intellectual Ventures spin-off that also boasts Bill Gates as an investor, is working on a new reactor design called a traveling wave reactor that uses fast reactor technology, rather than the light water technology used at the Fukushima Daiichi plant. The two biggest advantages of the fast reactor design is that it requires no spent fuel pools and uses cooling systems that require no power to function, meaning the loss of power from the tsunami might not have crippled a fast reactor plant so severely."

Comments

Um, don't safe reactors already exist?

[DurendalMac]

My understanding is that breeder reactors and pebble bed reactors wouldn't have had the problem that hit the plant in Japan. That and breeder reactors have the added benefit of eating nuclear waste over and over until whatever is left might make you sneeze. Maybe I'm completely off on that, but why do we need a new design on this kind of reactor unless it's relatively simple to retrofit older reactors?

CANDU

[andymadigan]

Since a CANDU (Heavy Water) reactor's fuel isn't naturally capable of going critical, couldn't that existing, tried and true design be used instead? We can fuel it with nuclear waste from American reactors, or use raw uranium ore, with no need for centrifuges or other tech that can be used to create nuclear weapons. If the cooling system fails, then you should have the backup of draining the heavy water from the reactor core, thus killing the reaction.

I'm not saying that's the only solution, I'm just saying that a known good solution that's been working for decades is probably better than a new one.

Re:Pebble bed reactor

[Anonymous Coward]

These are only the size of a shipping container and are a self contained unit. They would be a great way to bypass the NIMBYism associated with nuclear power plants. They are also much safer. If these can be bought by people with a bit of cash in the attic and installed in the countryside unknown to the neighbours we can all enjoy cheap nucular energy while everyone is blisfully oblivious to the fact that the neighbours little 'storage' container is actually a nucular power plant

It turns out that pebble beds aren't quite so maintenance free. Although the helium used as a coolant doesn't become radioactive, the graphite in the pebbles absorb radioactive metals and spread it around in graphite dust particles. Both the the AVR and HTR reactors in germany had big problems with contamination of the reactors due to this and due to the inability of the pebbles to contain radioactive isotopes.

Also, the pebble bed itself can't be instrumented so it becomes a black box resulting in unexpected hot currents of gas that can be significantly (200+K) warmer than expected. This resulted in maintenance issues in the two reactors in Germany (I don't think there is information on other experimental or production reactors using a pebble bed design). These problems might be surmountable but right now they're pretty big issues.

Some might, but some wouldn't:

[Hartree]

That's not entirely true.

For example. Amory Lovins, one of the notables of the anti-nuclear movement was asked in an interview what he thought of a truly cheap clean energy source. He said it would be a disaster. Why? Because he believes that whenever humans are given concentrated sources of power, they use it to destroy nature. Thus humans need to be limited to diffuse and limited sources of energy.

Quite often the waste and radiation questions are arguments used against nuclear power, when some of the motivation would have problems with any concentrated source of energy.

Needless to say, I disagree with that viewpoint, but it is one that can be argued and is not totally without merit.

Re:Dumb question...

[CrimsonAvenger]

Now the important part: Shutting down the reactors was by far the correct thing to do here because cooling was necessary for the daughter isotopes.
That is, the stuff we've been cooling all this time is the result of decay from before the plant was shut down.

It should perhaps be noted that I'm a former reactor plan operator. I have a clue.

Yes, cooling the daughter isotopes is exactly the issue. You generate fewer of them when you reduce output from commercial levels to self-sustaining levels.

And when you reduce power (but not shutdown completely), the decay products begin to decay down toward the new steady-state level. Which is a LOT less than steady state when you're operating at 90%+.

Every minute that goes by with the reactor operating at a reduced output is another minute you don't have to find an external power source to cool things down. And another minute farther from a core meltdown.

As was, by doing a hard shutdown immediately, the reactor was placed into a position such that the only possible way for a "good" outcome would be for the national electrical grid to stay completely intact during the next few days. There's no way that the battery back-up they had could keep cooling that plant for the next couple days by itself.

Which leaves as your only real option to try to use the reactor's output to maintain cooling while you burn through the decay products for as long as possible. After all, you can always scram the reactor later, if things don't work out.