Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Thorium Instead Of Uranium: Solution To Our Energy Woes?

wmbriggs.com

Post reply on HN
Print view View original

21–30 of 73 posts

Re: Thorium Instead Of Uranium: Solution To Our Energy Woes?

#21

Post by DanielBMarkham »

I'm a big fan of Thorium, but I'm also a big fan of nuclear in general. It just makes sense.

In fact, this is a lot like the issue of not building any oil refineries in the United States since the 1970s. While I'm sure there are good reasons for our lack of needed nuke plants, at the end of the day it looks like the system has let us all down.

I hate to sound like old cranky guy again, but frack, if you really wanted to get off oil you could do the math for how many nuke plants you'd need -- it'd be a lot! But it wouldn't be impossible, and we've known all of this for decades. It's just very frustrating. Things like the thorium ideas just make things worse because we can't even solve our problems using the old technology, much less the new stuff. It's almost like rubbing salt in the wound to see such potential and realize how improbable it will be to see the light of day (in a massive production sense). I find the state of our energy policy completely incredible, but the tech continues to look better with each passing year. Sigh.

Re: Thorium Instead Of Uranium: Solution To Our Energy Woes?

#22

Post by Retric »

terra_t wrote: post #19
Retric wrote: post #18

Earlier quoted context omitted.

We have already mined something like 100 years worth of Uranium that is just waiting around to be used in power plants. Or, if the US moved to breeder reactors we could go for something like 1000 years without mining any new uranium.

The trouble with fast breeders is that you need a huge fissile inventory to get one started. A study of the PRISM design, a modern fast breeder that uses integral reprocessing to reduce the inventory of plutonium that's sitting around, not fissioning, indicates that if we reprocessed all spent fuel in the U.S. today, we'd have enough Pu to power about 33 MWe worth of breeders, about 1/3 of the current fleet. It comes…

Over the next 40 years there is little economic reason to move to breeder reactors. However, they are a much better long term solution to waste than simply storing the stuff in the ground. Also, because the LWR to Breeder cycle spends so much time on the Breeder side of the equation a fixed number of LWR can feed a growing number of Breeder reactors over time. Thus you need to map out what happens over long time periods to get the balance correct.

Edit: If a LWR extracts 2% of total energy in 0.2% of the time, a breeder would need 10x the fuel to produce that much power and it would take 500 times as long to use up that fuel. Thus the stable ratio of LWR to breeders would be 1:50 relative to power output, but it would take ~750 LWR fuel cycles to reach that balance assuming you did not start wait for a huge stockpile to begin. (Breeders are not 100% efficient but the math is not all that far from reality.)

Re: Thorium Instead Of Uranium: Solution To Our Energy Woes?

#23

Post by sdurkin »

Retric wrote: post #16
GiraffeNecktie wrote: post #4

The short answer is that there are many entrenched interests who are not keen on the idea: Uranium mines, nuclear industry, weapons manufacturers, not to mention the oil, gas and coal lobbies, even the alternative energy suppliers like solar. Thorium would rain on all their parades.

The real answer is the R&D costs are not worth it because Uranium is still extreamly cheap. The fuel costs for a modern reactor are a small fraction of total cost. Also, fosil fuels a not going to be replaced with wind, solar, fission or fusion any time soon because they are not really portable for anything smaller than a boat.

You're both right.

"The real answer is the R&D costs are not worth it because Uranium is still extreamly cheap."

This answers why the market won't develop the technology on its own. But the government could still sponsor research as they did with uranium fission.

"The short answer is that there are many entrenched interests who are not keen on the idea..."

And this answers why the government would never fund it.

Re: Thorium Instead Of Uranium: Solution To Our Energy Woes?

#24

Post by terra_t »

Retric wrote: post #22
terra_t wrote: post #19

Earlier quoted context omitted.

The trouble with fast breeders is that you need a huge fissile inventory to get one started. A study of the PRISM design, a modern fast breeder that uses integral reprocessing to reduce the inventory of plutonium that's sitting around, not fissioning, indicates that if we reprocessed all spent fuel in the U.S. today, we'd have enough Pu to power about 33 MWe worth of breeders, about 1/3 of the current fleet. It comes…

Over the next 40 years there is little economic reason to move to breeder reactors. However, they are a much better long term solution to waste than simply storing the stuff in the ground. Also, because the LWR to Breeder cycle spends so much time on the Breeder side of the equation a fixed number of LWR can feed a growing number of Breeder reactors over time. Thus you need to map out what happens over long time peri…

And that gets us to the central problem of our energy policy.

Utilities are moving towards a short-term thinking model where they install natural gas turbine with a low capital cost and use electricity deregulation to offload the risk of volatile natural gas prices to the consumer. "Renewables" are also driven by short-term motives: making a quick buck by exploiting government subsidies.

Nuclear energy can give us a sustainable energy source the thousand-year timescale (energy-wise, breeders can certainly consume seawater U238 profitably,) but we need to be thinking on the timescale of decades, not the next quarter, to get there.

Re: Thorium Instead Of Uranium: Solution To Our Energy Woes?

#25

Post by terra_t »

ScotterC wrote: post #14
eru wrote: post #7

Earlier quoted context omitted.

No. The problem is the other way around: It _can't_ easily be converted. That's why is was not investigated in the 40s and during the cold war too much: People were interested in bombs, too.

That's true. We had two reactor options during the cold war that were choices to extend our Uranium supply. One was the Fast Breeder reactor and the other was the liquid thorium reactor. My dad worked on the Fast breeder which would use liquid sodium as a coolant to allow the reactor to operate at much higher temperatures and high neutron flux so as to burn actinides more efficiently and convert uranium into plutoniu…

Realistic breeder fuel cycles also use a mix of actinides that would be unattractive for bomb makers: you're going to start with fuel that's been through an LWR once or twice, so contamination with Pu240 and Pu241/Am241 will be high to begin with and will just get worse the more cycles you spend in a fast spectrum.

Now, hypothetically, a country like Iran could develop a fast reactor that's optimized for producing plutonium for military purposes, but practically this would be much more difficult than developing a heavy water reactor like the U.S. used at Savannah River.

The isotope which is most problematic in commercial fuel cycles would actually be Np237. It's easy to separate Np chemically from other elements, and Np237 is longer lived than other isotopes of Np, so it can be prepared in a very pure form. Np237 has a low spontaneous fission cross section and a critical mass close to pure U235 -- it would be an attractive material for primitive gun-type bombs.

Note that Np237 is produced from U235 by the chain of absorbing two neutrons, making U237, and then beta decay to Np237. A plutonium-fueled or thorium-fueled reactor isn't going to make as much of it as our current reactors do.

Re: Thorium Instead Of Uranium: Solution To Our Energy Woes?

#26

Post by edfrtghjkjh »

grandinj wrote: post #15

This is a classic case of a solution to a problem that does not exist. Firstly, Uranium is practically an insignificant cost of a nuclear power station. The price would have to go up by a factor of a 100 before it made a difference. Secondly, the supplies of uranium are currently limited because the demand is limited. The moment the price shifts up by even a little, supply will grow because several other mining locat…

True for the US with a big supply of uranium in a (relatively) friendly country to the north.

Different for say India that has lots of Thorium, no Uranium and doesn't want to go begging to Russia or spend hard currency in Canada.

Re: Thorium Instead Of Uranium: Solution To Our Energy Woes?

#27

Post by olegkikin »

Retric wrote: post #18
grandinj wrote: post #15

This is a classic case of a solution to a problem that does not exist. Firstly, Uranium is practically an insignificant cost of a nuclear power station. The price would have to go up by a factor of a 100 before it made a difference. Secondly, the supplies of uranium are currently limited because the demand is limited. The moment the price shifts up by even a little, supply will grow because several other mining locat…

We have already mined something like 100 years worth of Uranium that is just waiting around to be used in power plants. Or, if the US moved to breeder reactors we could go for something like 1000 years without mining any new uranium.

Your 100 and 1000 year assumptions are just silly. You assume energy demands will remain constant, while they are exponential.

Just think what will happen if electric cars become popular. We will need a lot of electricity.

Re: Thorium Instead Of Uranium: Solution To Our Energy Woes?

#28

Post by henrikschroder »

DanielBMarkham wrote: post #21

I'm a big fan of Thorium, but I'm also a big fan of nuclear in general. It just makes sense. In fact, this is a lot like the issue of not building any oil refineries in the United States since the 1970s. While I'm sure there are good reasons for our lack of needed nuke plants, at the end of the day it looks like the system has let us all down. I hate to sound like old cranky guy again, but frack, if you really wanted…

Nuclear power plants can't replace oil- or coal-powered plants, because nuclear plants can't adjust output over the day to fit actual usage. Nuclear power plants are great for providing the baseline power production, but you need something adjustable to handle the morning and evening peaks, like oil or coal or wind or hydro or really big batteries.

So no, you can't do the math for how many nuclear plants you would need to get off oil.

Re: Thorium Instead Of Uranium: Solution To Our Energy Woes?

#29

Post by cameldrv »

henrikschroder wrote: post #28
DanielBMarkham wrote: post #21

I'm a big fan of Thorium, but I'm also a big fan of nuclear in general. It just makes sense. In fact, this is a lot like the issue of not building any oil refineries in the United States since the 1970s. While I'm sure there are good reasons for our lack of needed nuke plants, at the end of the day it looks like the system has let us all down. I hate to sound like old cranky guy again, but frack, if you really wanted…

Nuclear power plants can't replace oil- or coal-powered plants, because nuclear plants can't adjust output over the day to fit actual usage. Nuclear power plants are great for providing the baseline power production, but you need something adjustable to handle the morning and evening peaks, like oil or coal or wind or hydro or really big batteries. So no, you can't do the math for how many nuclear plants you would ne…

Sure they can. Hybrids that charge at night, that get cheaper rates to charge when the utility sends a signal, pumped storage, only running hydroelectric during the day, running aluminum smelters at night, thermal storage, or worst case, just not using the extra electricity. There is stuff to build, but we're not going to build all of those nuke plants overnight either.

Re: Thorium Instead Of Uranium: Solution To Our Energy Woes?

#30

Post by pjscott »

ScotterC wrote: post #13
johndcook wrote: post #2

The post doesn't give a definite answer to the question in the title, but it is interesting.

It could be a plausible solution to our electricity woes to a degree. Mainly in baseload electricity supply which is about 60% of the U.S. grid. Small liquid flouride thorium reactors (LFTRs) can fit on a flatbed truck and mass manufactured. The idea is that we can connect these to existing coal plant secondary systems around the country and replace the coal boilers. Thorium is extremely abundant. We have 3000 tons o…

If we can get the cost per megawatt of capacity low enough, liquid fluoride thorium reactors could even be used for peak power. They can scale their power output up and down pretty rapidly, since they would use Brayton-cycle gas turbines for power conversion, and it's possible to continuously (or very frequently) remove xenon-135, which is a neutron poison and has traditionally made it harder to adjust the power output of nuclear reactors.
Post reply on HN