Friday, May 17, 2013

A Boy and His Nuclear Reactor

Taylor Wilson built a fusion reactor at age 14 and remains interested in nuclear technology. So, at 19, he has presented his idea for a small reactor concept that uses molten salt to make the smaller reactor both more powerful and more efficient than their cousins.

Wilson's fission reactor operates at 600 to 700 degrees Celsius. And because the laws of thermodynamics say that high temperatures lead to high efficiencies, this reactor is 45 to 50 percent efficient.

Traditional steam turbine systems are only 30 to 35 percent efficient because their reactors run at low temperatures of about 200 to 300 degrees Celsius.

And Wilson's reactor isn't just hot, it's also powerful. Despite its small size, the reactor generates between 50 and 100 megawatts of electricity, which is enough to power anywhere from 25,000 to 100,000 homes, according to Wilson.

Okay, that’s the hot and powerful part.

And unlike traditional nuclear power plants, Wilson's miniature power plants would be buried below ground, making them a boon for security advocates.

According to Wilson, his reactor only needs to be refueled every 30 years, compared to the 18-month fuel cycle of most power plants. This means they can be sealed up underground for a long time, decreasing the risk of proliferation.

And that’s the small reactor part. Listening to Wilson at the TED conference and reading the details of his idea, I expected to find – more – that is, where this idea departs from earlier ideations of small, molten salt reactors.

For example, here is more-or-less (more, I’d say) the same thing from Transatomic Power.

Enter Transatomic’s molten salt reactor (MSR). …

The safety advantages of this project are mostly features of molten salt reactors in general. Using high boiling-point coolants like fluoride or chloride salts in place of light or heavy water negates the need to pressurize the system and instantly reduces the dangers associated with super-heated, pressurized liquids.

And the article from ExtremeTech points out that molten salt reactors have been contemplated since the 60s.

Researchers have actually had working models of the MSRs since the ’60s [even the 1950s – see here], but they’ve never been used for commercial purposes. One reason is that much of nuclear’s research capital comes from the military, and bulky MSR technology has traditionally been less desirable for submarines and aircraft carriers than their relatively slim light-water cousins. Another is that the plants require a separate facility to filter their core mixture.

So we can allow that Wilson may have some new ideas about the molten salt reactor – how to make it workable at a smaller size, maybe - but it’s hard at present to pin down what they are. Or what would cause the technology to gain traction at this particular time – which I imagine Transatomic would like to do, too.

But none of this is to say that the idea shouldn’t gain traction, or that Taylor has simply reinvented the molten wheel, or that Transtomic and Taylor shouldn’t pursue their ideas – well, to the extent that patents don’t play a role. Right now, it’s all just a curiosity. And that is the point of TED, right?

8 comments:

jimwg said...

Hurray for him!

An asides though; if this concept was so relatively simple and efficient, why haven't others like China or India ripped it long ago if not now? Just wondering.

James Greenidge
Queens NY

Anonymous said...

Molten salt reactors simply aren't economically feasible. Anyone who has worked at a nuclear reactor would understand that it is INCREDIBLY difficult to keep it running even with the simple water-steam cycle used now. To complicate that by adding an unproven molten salt cycle would be incredibly difficult and expensive. For example, think about how poor of a capacity factor a reactor like SuperPhoenix had due to it's more complicated technology. This can be solved of course, but that would cost billions more and make the plant too expensive.

When I was working at Watts Bar there were something like 50 leaks at any given time on the operating unit. If they are leaking water or steam that isn't a big deal, but leaking molten salt would be far worse. Also, the chemistry seems like it would be difficult. There are a lot of chemicals added to the water in a nuclear plant to keep if from cordoing the steel. Does anyone here know if molten salt and steel interact to form corrosion products that would be come radioactive or would slowly eat through the pipes? I've seen inch thick carbon steel corroded thorough just by plain water and boric acid does it FAR faster. Does anyone know what molten salt would do after 40 years?

Anonymous said...

Anon - molten salt or liqui metal reactors run at atmospheric pressure, rather than the 2250 psi you had to contend with at watts bar. So, the leakage issues are not comparable.

Anonymous said...

I heard Edward Teller speak any number of times and he usually mentioned the idea of underground reactors, even using the conventional LWRs of today. Containment and security are but two of the advantages of such a siting scheme. I've always had this vision of an underground nuclear plant where the plant employees would also help with harvesting a vegetable or wheat/corn/soybean farm on the land above it, maybe using once-through cooling instead of a cooling tower. Talk about zero visual impact, this would have it all over any monstrosity of a windmill farm.

Anonymous said...

It's not only the pressure that can be an issue, it's the temperature and chemistry as well. I simply don't know enough to tell you what all the issues would be, but if they were simple issues then we would have switched long ago. I did a little research and it seems like some of the test reactors were made of Hasteloy or Inconel, these are VERY expensive alloys and there have been extensive industry issues with the dissimilar metal welds between Alloy 600 and steel for example.

Anonymous said...

"molten salt or liqui metal reactors run at atmospheric pressure, rather than the 2250 psi you had to contend with at watts bar. So, the leakage issues are not comparable."

Not comparable, but not negligible either. Every sodium-cooled reactor that has operated has experienced coolant leaks, some very serious. Monju leaked tons of sodium and it caught fire in 1995, putting the reactor out of commission for 14 years.

anon2 said...

If anonymous1 had raised the potential for leaks by pointing to experience at Monju instead of experience at Watts Bar, I would not have bothered to post. But S/he asserted that MSRs "simply aren't economically feasible" without any pertinent justification (IMO).

-anon2

Engineer-Poet said...

"Monju leaked tons of sodium and it caught fire in 1995, putting the reactor out of commission for 14 years."

Not really.  The sodium leak put the reactor out of commission about as long as it would have taken to remove the broken thermocouple well and put in a pipe plug.  The cleanup didn't take very long, but authorities waited until 2000 to go for a restart.  Most of the delays were political, not technical.  Since 2010 the issue has been political refusal to budget for the necessary work.

"I did a little research and it seems like some of the test reactors were made of Hasteloy or Inconel, these are VERY expensive alloys and there have been extensive industry issues with the dissimilar metal welds between Alloy 600 and steel for example. "

The ARE ran up to 860°C using Inconel tubing.  Hastelloy-N is compatible with molten fluorides and IIRC the tellurium corrosion problem was fixed with the addition of titanium.  Someone (on Atomic Insights?) suggested that technetium, which is almost a noble metal, be used for its anti-corrosive properties.  It is somewhat ironic that "nuclear waste" could become a reactor building material.  Metal cost doesn't seem to be a terribly big matter because the power density of nuclear reactors is so high.

For higher temperatures, current alloys won't do.  I've read some papers exploring graphite.  I'd like to see this done, but it probably won't happen in the oligarchic USA.