6 ms·

Nuclear's next generation

90 points by pg 17y ago

thaumaturgy 17y ago
Another newer technology to keep an eye on: plasma gasification (http://www.slate.com/id/2181083/ http://www.slate.com/id/2181083/). Although it produces paltry amounts of energy compared to nuclear facilities, it's a neat solution to the problem of waste management, capable of handling low-grade nuclear waste.
jeremyw 17y ago
One form of very high temperature reactor, the pebble bed reactor, was theorized in the 1950s and has been under development at various locations for more than a decade -- China begins commercial construction this year. PBRs are one of several inherently safe designs wherein shutoff of circulating coolant raises core temperature and natural processes serve to choke criticality. http://en.wikipedia.org/wiki/Pebble_bed_reactor http://en.wikipedia.org/wiki/Pebble_bed_reactor
- sketerpot 17y ago
  Pebble beds are also compatible with thorium, in case anybody was wondering.
- rainier 17y ago
  The pebble bed reactor has inherently safe features concerning loss of coolant, but it is not inherently safe: There are other sever accidents not known in conventional reactors, like graphite fire (as it happened in Chernobyl, too) and water ingress into the core with subsequent explosions.
Daniel_Newby 17y ago
I like the sodium fast reactor: low pressure, moderate temperature, sodium is dirt cheap, high burn-up of non-uranium/plutonium products ("waste"), and plutonium need never be separated from other reaction products. The article doesn't say, but because molten salt reactors use liquid fuel, they release the radioactive xenon gas produced by uranium fission. (In fact this is sold as a benefit, since xenon absorbs neutrons better used for the chain reaction.) Xenon is a noble gas and therefore volatile, so the reactor will need strenuous containment measures. Loss of the gas seal would result in significant radioactivity release. Helium-cooled reactors may be constrained by shortages of helium, which is rather rare and difficult to extract on Earth. You'd hope that government program managers would have worked out the logistics of this, but they tend to not see things that would get their funding cut. (Argon is plentiful but might not be a substitute because it reacts with neutrons a lot more than helium does.)
- sp332 17y ago
  > Xenon is a noble gas and therefore volatile This must be some definition of "volatile" I'm not familiar with.
  - Daniel_Newby 17y ago
    Evaporating easily. Xenon boils at -108 deg. C. Given the chance, it would tend to rapidly escape from liquid fuel at reactor temperatures.
    - elblanco 17y ago
      We're probably both thinking of "prone to explode" vs. "prone to evaporate".
  - elblanco 17y ago
    Well, if had said "nonvolatile" it would have been boring.
- sketerpot 17y ago
  In the case of liquid fluoride thorium reactors, I don't think the xenon-135 is what you need to be worrying about; worry about the fluorine gas instead! It's very reactive. Xenon, on the other hand, is chemically stable because it's a noble gas. And it's larger than helium, so it's easier to contain. Also, I'd like to point out that pebble-bed reactors, while usually cooled with helium, could also be cooled with nitrogen that we just pull out of the air. It's more reactive than helium and it forms carbon-14 when you expose it to neutron flux, but those issues are both fairly minor. I think they're going with helium now because they want to get something working as quickly as they can, and they don't want to go mucking with what works.
  - Daniel_Newby 17y ago
    They use the relatively-nonvolatile fluoride ion (F-), not the gaseous molecular fluorine (F2). Fluoride is corrosive in higher concentrations, but nowhere near as dangerous as the oxidative toxicity of fluorine gas. Re. nitrogen, the radiation would turn it into ionized nitrogen radicals. Any info on how much damage that would cause to the graphite and metals? Also, carbon-14 is preferentially concentrated into living things, so a release would provoke a political panic similar to strontium-90.
DanielBMarkham 17y ago
I'm a fan of liquid fluoride thorium reactors (LFTR). The prevalence of Thorium is a big positive and the ability to process out existing nuclear waste is a tremendous boon. We're not that far away from commercializing LFTR. It's a shame we can't find more research funds.
maksimka 17y ago
I like the idea, as long as it's very far away away from my house.
- tokenadult 17y ago
  I don't mind at all having a nuclear power plant upriver not particularly far from my home. It makes the electricity rates here noticeably less expensive than in many other parts of the country. That plant has been operating harmlessly for about four decades now. After edit: indeed, I prefer having a nuclear power plant (somewhat) nearby to having a coal-burning power plant equally upstream and nearby, and prefer both to living without inexpensive electricity.
- cmelbye 17y ago
  As the other poster said, it's better than living next to a coal burning plant. The coal burning plant would actually release more radioactive material into the environment than a nuclear power plant would.
  - earthboundkid 17y ago
    I’ve heard this before, but is there any reason to think that the issue goes beyond the fact that CO2 has a higher natural level of radiation than H2O?
    - dubcomesaveme 17y ago
      incomplete combustion\plenty of other stuff in the ground in it(heavy metals etc.). The smoke is not just CO2. Plus " sulfur dioxide (SO2) and nitrogen oxides (NOx) are the primary causes of acid rain. In the US, About 2/3 of all SO2 and 1/4 of all NOx comes from electric power generation that relies on burning fossil fuels like coal." http://www.policyalmanac.org/environment/archive/acid_rain.shtml http://www.policyalmanac.org/environment/archive/acid_rain.s... and acid rain causes a number of environmental problems.
      - bjelkeman-again 17y ago
dubcomesaveme 17y ago
u.s. nuclear reactors have always been safe: if a loss of coolant failure occurs the reaction is designed to slow down rather than speed up soviet cheronobyl style. the concern is what to do with all the junk from processing\using fuel rods and depleted uranium besides dumping it on Iraqis via munitions.
- bjelkeman-again 17y ago
  That doesn't always seem to work though: http://en.wikipedia.org/wiki/Three_Mile_Island_accident http://en.wikipedia.org/wiki/Three_Mile_Island_accident
  - dondraper 17y ago
    >In the aftermath of the accident, investigations focused on the amount of radiation released by the accident. According to the American Nuclear Society, using the official radiation emission figures, "The average radiation dose to people living within ten miles of the plant was eight millirem, and no more than 100 millirem to any single individual. Eight millirem is about equal to a chest X-ray, and 100 millirem is about a third of the average background level of radiation received by US residents in a year."[31][52] Read a bit closer
    - teeja 17y ago
      IIRC the figures on TMI (not broken down into phantom per-capita exposures but to the environment) included millions of Curies released into the environment. Some credible researchers have found evidence that figure may be 10 to 100 times too small. Not surprising; with all the money involved, the science gets 'adjusted'. The industry can afford the best PR.
      - dondraper 17y ago
        I think the per-capita exposures figure was simply to give a sense of scale not to obscure the figures. Do you have a source that backs that claim?
dmfdmf 17y ago
The current reactor designs are safe enough, let's build them now. Debating the pros and cons of advanced designs is dumb and accepts the enviros false claim that current BWR or PWR light water reactors are "unsafe". Moreover, significant real-world safety comes from operational experience on a fleet of the same or similar designs. It would be foolish to throw away 50 years of knowledge and experience on light water reactors to start over on sodium, fluoride, pebble-bed, etc.
- cheriot 17y ago
  It's also about efficiency. Nuclear power plants regularly live beyond their designed lifespan of 30-40 years. If a new reactor can be built with 45% efficiency rather that the 33% of existing light water reactors get, that alone will justify the delay.

90 points by pg 17y ago

Another newer technology to keep an eye on: plasma gasification (http://www.slate.com/id/2181083/ http://www.slate.com/id/2181083/). Although it produces paltry amounts of energy compared to nuclear facilities, it's a neat solution to the problem of waste management, capable of handling low-grade nuclear waste.

jeremyw 17y ago

One form of very high temperature reactor, the pebble bed reactor, was theorized in the 1950s and has been under development at various locations for more than a decade -- China begins commercial construction this year. PBRs are one of several inherently safe designs wherein shutoff of circulating coolant raises core temperature and natural processes serve to choke criticality. http://en.wikipedia.org/wiki/Pebble_bed_reactor http://en.wikipedia.org/wiki/Pebble_bed_reactor

sketerpot 17y ago
Pebble beds are also compatible with thorium, in case anybody was wondering.
rainier 17y ago
The pebble bed reactor has inherently safe features concerning loss of coolant, but it is not inherently safe: There are other sever accidents not known in conventional reactors, like graphite fire (as it happened in Chernobyl, too) and water ingress into the core with subsequent explosions.

Daniel_Newby 17y ago

I like the sodium fast reactor: low pressure, moderate temperature, sodium is dirt cheap, high burn-up of non-uranium/plutonium products ("waste"), and plutonium need never be separated from other reaction products. The article doesn't say, but because molten salt reactors use liquid fuel, they release the radioactive xenon gas produced by uranium fission. (In fact this is sold as a benefit, since xenon absorbs neutrons better used for the chain reaction.) Xenon is a noble gas and therefore volatile, so the reactor will need strenuous containment measures. Loss of the gas seal would result in significant radioactivity release. Helium-cooled reactors may be constrained by shortages of helium, which is rather rare and difficult to extract on Earth. You'd hope that government program managers would have worked out the logistics of this, but they tend to not see things that would get their funding cut. (Argon is plentiful but might not be a substitute because it reacts with neutrons a lot more than helium does.)

sp332 17y ago
> Xenon is a noble gas and therefore volatile This must be some definition of "volatile" I'm not familiar with.
- Daniel_Newby 17y ago
  Evaporating easily. Xenon boils at -108 deg. C. Given the chance, it would tend to rapidly escape from liquid fuel at reactor temperatures.
  - elblanco 17y ago
    We're probably both thinking of "prone to explode" vs. "prone to evaporate".
- elblanco 17y ago
  Well, if had said "nonvolatile" it would have been boring.
sketerpot 17y ago
In the case of liquid fluoride thorium reactors, I don't think the xenon-135 is what you need to be worrying about; worry about the fluorine gas instead! It's very reactive. Xenon, on the other hand, is chemically stable because it's a noble gas. And it's larger than helium, so it's easier to contain. Also, I'd like to point out that pebble-bed reactors, while usually cooled with helium, could also be cooled with nitrogen that we just pull out of the air. It's more reactive than helium and it forms carbon-14 when you expose it to neutron flux, but those issues are both fairly minor. I think they're going with helium now because they want to get something working as quickly as they can, and they don't want to go mucking with what works.
- Daniel_Newby 17y ago
  They use the relatively-nonvolatile fluoride ion (F-), not the gaseous molecular fluorine (F2). Fluoride is corrosive in higher concentrations, but nowhere near as dangerous as the oxidative toxicity of fluorine gas. Re. nitrogen, the radiation would turn it into ionized nitrogen radicals. Any info on how much damage that would cause to the graphite and metals? Also, carbon-14 is preferentially concentrated into living things, so a release would provoke a political panic similar to strontium-90.

DanielBMarkham 17y ago

I'm a fan of liquid fluoride thorium reactors (LFTR). The prevalence of Thorium is a big positive and the ability to process out existing nuclear waste is a tremendous boon. We're not that far away from commercializing LFTR. It's a shame we can't find more research funds.

maksimka 17y ago

I like the idea, as long as it's very far away away from my house.

tokenadult 17y ago
I don't mind at all having a nuclear power plant upriver not particularly far from my home. It makes the electricity rates here noticeably less expensive than in many other parts of the country. That plant has been operating harmlessly for about four decades now. After edit: indeed, I prefer having a nuclear power plant (somewhat) nearby to having a coal-burning power plant equally upstream and nearby, and prefer both to living without inexpensive electricity.
cmelbye 17y ago
As the other poster said, it's better than living next to a coal burning plant. The coal burning plant would actually release more radioactive material into the environment than a nuclear power plant would.
- earthboundkid 17y ago
  I’ve heard this before, but is there any reason to think that the issue goes beyond the fact that CO2 has a higher natural level of radiation than H2O?
  - dubcomesaveme 17y ago
    incomplete combustion\plenty of other stuff in the ground in it(heavy metals etc.). The smoke is not just CO2. Plus " sulfur dioxide (SO2) and nitrogen oxides (NOx) are the primary causes of acid rain. In the US, About 2/3 of all SO2 and 1/4 of all NOx comes from electric power generation that relies on burning fossil fuels like coal." http://www.policyalmanac.org/environment/archive/acid_rain.shtml http://www.policyalmanac.org/environment/archive/acid_rain.s... and acid rain causes a number of environmental problems.
    - bjelkeman-again 17y ago

dubcomesaveme 17y ago

u.s. nuclear reactors have always been safe: if a loss of coolant failure occurs the reaction is designed to slow down rather than speed up soviet cheronobyl style. the concern is what to do with all the junk from processing\using fuel rods and depleted uranium besides dumping it on Iraqis via munitions.

bjelkeman-again 17y ago
That doesn't always seem to work though: http://en.wikipedia.org/wiki/Three_Mile_Island_accident http://en.wikipedia.org/wiki/Three_Mile_Island_accident
- dondraper 17y ago
  >In the aftermath of the accident, investigations focused on the amount of radiation released by the accident. According to the American Nuclear Society, using the official radiation emission figures, "The average radiation dose to people living within ten miles of the plant was eight millirem, and no more than 100 millirem to any single individual. Eight millirem is about equal to a chest X-ray, and 100 millirem is about a third of the average background level of radiation received by US residents in a year."[31][52] Read a bit closer
  - teeja 17y ago
    IIRC the figures on TMI (not broken down into phantom per-capita exposures but to the environment) included millions of Curies released into the environment. Some credible researchers have found evidence that figure may be 10 to 100 times too small. Not surprising; with all the money involved, the science gets 'adjusted'. The industry can afford the best PR.
    - dondraper 17y ago
      I think the per-capita exposures figure was simply to give a sense of scale not to obscure the figures. Do you have a source that backs that claim?

dmfdmf 17y ago

The current reactor designs are safe enough, let's build them now. Debating the pros and cons of advanced designs is dumb and accepts the enviros false claim that current BWR or PWR light water reactors are "unsafe". Moreover, significant real-world safety comes from operational experience on a fleet of the same or similar designs. It would be foolish to throw away 50 years of knowledge and experience on light water reactors to start over on sodium, fluoride, pebble-bed, etc.

cheriot 17y ago
It's also about efficiency. Nuclear power plants regularly live beyond their designed lifespan of 30-40 years. If a new reactor can be built with 45% efficiency rather that the 33% of existing light water reactors get, that alone will justify the delay.