Page 1 of 2 12 LastLast
Results 1 to 20 of 29

Thread: what improvements should be made in the next generation nuclear power plants?

  1. #1

    Default what improvements should be made in the next generation nuclear power plants?

    With the concern over riding CO2, there is a renewed interest in nuclear power. While many Climate Change proponents reject nuclear power, there are some those who think that nuclear power does have a role play in reducing CO2. After all,today France produces most of its electric power from non CO2 producing sources thanks to nuclear power.

    So if there is an increase in nuclear power, or just the replacing of old existing nuclear power with new nuclear plants, what improvements should we be looking for over existing designs?

    I think these are some of the things we should be asking from new designs:

    1. Improved safety, of course. But I don't think this is actually the biggest need, most current reactor designs are safe. 3 Mile Island was the last major nuclear accident in the US, and that was 40 years ago. Despite a lot of claims, no death directly related to 3 Mile Island disaster has been proven, and there has been no major increases in cancer death deaths in the area around the site. Still, improvements can always be made .

    2. Lower cost to build - one of the biggest drawbacks to the high cost of nuclear power plant construction.

    A. Have modular where most odnrhe construction is done off-site. Current designs have a lot of their construction done onsite, which can make delays costly. Quality can also be better monitored at the factory than on a construction site.

    B. Ensure the public, especially the anti-nuclear folksz invovleved in the planning stages. While the anti-nuclear cook are never likely to approve of any nuclear plant, by giving them the opportunity to get involved in the initial design phase will make it more difficult for them to demand costly late design changes.

    3. Improve the start up and shut down times od nuclear power plants. I haven't heard anyone discuss this, but current nuclear power plants take a long time to start up and shut down. To bring power on line quickly, most companies resort to gas turbine generators which can quickly be brought online to meet peak demands, or to compensate for an unexpected loss of other generating capacity. If you could have a nuclear design that could be quickly brought online, it would help elimate the need for these fossil fuel gas turbines that otherwise still would be needed.

    4. More efficient fuel use and reduced nuclear waste - while the cost the fuel isn't really the issue, in many current designs the fuel is spent when the concentration of fissionable Ur235 drops below a certain percentage. More efficient fuel use would reduce rue amount of spent fuel that needs to be reprocessed.

    5. More flexible designs - right now, nuclear power plants are only economical in large (1000 MW+) designs. If smaller plants could be made economical, it would make nuclear power a more viable option for replace fossil fuel in smaller markets.

    Any other improvements that anyone else can think of that should be made?

  2. #2

    Default Re: what improvements should be made in the next generation nuclear power plants?

    You don't really need any improvement. The only thing that's missing is political will, that's it. Here's the thing, the high capital cost of nuclear energy is actually its biggest strength. It's a lot easier to approve spending a ton of money on individual power plants, instead of attempting to fundamentally change the power grid. Once the reactors are built, they cost pennies to operate. Everyone wants to phase out nuclear power because its the sexy thing to do in current climate change discourse. If anything, nuclear power should've been scaled up considerably since 2008.

  3. #3
    AqD's Avatar (~‾▿‾)~
    Join Date
    Dec 2007
    Location
    Home
    Posts
    10,117

    Default Re: what improvements should be made in the next generation nuclear power plants?

    But what to do with the radioactive waste?? Even reused waste has radioactivity left.

  4. #4
    Genava's Avatar Centenarius
    Join Date
    Mar 2009
    Location
    Geneva
    Posts
    888

    Default Re: what improvements should be made in the next generation nuclear power plants?

    Open Access Defenders Step Up to Save ‘Pirate Bay of Science’
    https://nerdist.com/article/open-acc...brary-genesis/

  5. #5

    Default Re: what improvements should be made in the next generation nuclear power plants?

    Quote Originally Posted by AqD View Post
    But what to do with the radioactive waste?? Even reused waste has radioactivity left.
    I would like to point out that the uranium we mine is naturally radioactive. What are we going to do about all the that naturally radioactive uranium and other material?

    A few hundred million years ago, there was a natural nuclear reactor in Africa, with no shielding or protection, and nothing was done with the wasted it produced and it ran for thousands of years. Yet life survived.


    Reducing amount of nuclear waste can be another thing to look for, and ease of reprocrssing fuel. However, I think the dangers of nuclear waste are overststated. Our society works with nasty toxic material all the time. And toxic mercury waste stays toxic forever. Lead stays toxic forever lead will still be as toxic a million years from now, same for mercury.
    .
    Last edited by Common Soldier; October 09, 2019 at 11:55 PM.

  6. #6

    Default Re: what improvements should be made in the next generation nuclear power plants?

    The bigger point about nuclear waste is that it is minuscule. The vast majority of waste that results from nuclear reactors, is disposed safely in various sites around the country.

    Nuclear Energy Institute on waste:

    There is not that much of it. All of the used fuel ever produced by the commercial nuclear industry since the late 1950s would cover a football field to a depth of less than 10 yards. That might seem like a lot, but coal plants generate that same amount of waste every hour.
    They're talking about the most toxic waste that takes thousands of years to dispose of. The stuff that's inert, can be safely stored, and buried... Unlike the particulates tossed into the air by thousands of fossil fuel reactors, or the waste causing untold damage during mining.

  7. #7
    Genava's Avatar Centenarius
    Join Date
    Mar 2009
    Location
    Geneva
    Posts
    888

    Default Re: what improvements should be made in the next generation nuclear power plants?

    Quote Originally Posted by Common Soldier View Post
    I would like to point out that the uranium we mine is naturally radioactive. What are we going to do about all the that naturally radioactive uranium and other material?

    A few hundred million years ago, there was a natural nuclear reactor in Africa, with no shielding or protection, and nothing was done with the wasted it produced and it ran for thousands of years. Yet life survived.


    Reducing amount of nuclear waste can be another thing to look for, and ease of reprocrssing fuel. However, I think the dangers of nuclear waste are overststated. Our society works with nasty toxic material all the time. And toxic mercury waste stays toxic forever. Lead stays toxic forever lead will still be as toxic a million years from now, same for mercury.
    .
    Natural uranium is rarely enriched in U235 and lack critical mass for self sustaining reactions. The natural reactor in the actual Oklo region is 1.7 billions years old, before complex life rose. Life survived to very harsh conditions but personally I won't like to live in the same conditions. I am not a bacteria.

    But it is true that the nuclear waste are excessively regarded as an issue. A thorium fuel cycle could reduce the toxicity and calm down the public opinion about the nuclear industry. The only issue I have with nuclear is the nuclear proliferation.
    Open Access Defenders Step Up to Save ‘Pirate Bay of Science’
    https://nerdist.com/article/open-acc...brary-genesis/

  8. #8
    AqD's Avatar (~‾▿‾)~
    Join Date
    Dec 2007
    Location
    Home
    Posts
    10,117

    Default Re: what improvements should be made in the next generation nuclear power plants?

    Quote Originally Posted by Genava View Post
    The only issue I have with nuclear is the nuclear proliferation.
    What's wrong with proliferation? The most warlike countries in the world already hold the largest amounts.

  9. #9

    Default Re: what improvements should be made in the next generation nuclear power plants?

    Current nuclear technology uses fuel that could be weaponized into weapons. That's by design and it dates back to the Manhattan project. At least from what I've read. Thorium based nuclear reactors, do not produce plutonium as a by product and therefore do not pose the same risk for nuclear proliferation.

    To answer your question AqD. It's an issue of having a bigger risk of somebody pressing the button. Yeah, most countries aren't belligerent and are more concerned with their own survival, but there are many points of conflict where "survival" is a very nebulous term. Egypt and Ethiopia are currently having a fight over the Grand Ethiopian Renaissance Dam which threatens Egypt's water security. War may very well break out if negotiations go nowhere. Now what would happen if both countries had nukes? Egypt will see their existence under threat, Ethiopia also sees their economic development as vital to their existence and will fight for a better life, even if it upsets Egypt. In a world where nukes are common, the consequences of war are deadly, but that doesn't guarantee that states will be more careful with who they pick a fight with.

  10. #10

    Default Re: what improvements should be made in the next generation nuclear power plants?

    Quote Originally Posted by Sukiyama View Post
    Current nuclear technology uses fuel that could be weaponized into weapons. That's by design and it dates back to the Manhattan project. At least from what I've read. Thorium based nuclear reactors, do not produce plutonium as a by product and therefore do not pose the same risk for nuclear proliferation.

    To answer your question AqD. It's an issue of having a bigger risk of somebody pressing the button. Yeah, most countries aren't belligerent and are more concerned with their own survival, but there are many points of conflict where "survival" is a very nebulous term. Egypt and Ethiopia are currently having a fight over the Grand Ethiopian Renaissance Dam which threatens Egypt's water security. War may very well break out if negotiations go nowhere. Now what would happen if both countries had nukes? Egypt will see their existence under threat, Ethiopia also sees their economic development as vital to their existence and will fight for a better life, even if it upsets Egypt. In a world where nukes are common, the consequences of war are deadly, but that doesn't guarantee that states will be more careful with who they pick a fight with.
    Any country that really wants to have nuclear weapons, could, sanctions or no. A lot of countries have more technical expertise than North Korea, and they don't have nukes nor express any desire for them.

    I think terrorist would find it easier to bribe some under paid Russian guard or scientist to get the material they need. And long before the we worried about nukes, there was a number of old standbys to kill large number of peoples.

    1. Deliberately expose large number of people to a deadly virus. With less work than it takes to make a nuclear bomb, I bet some competent scientist could make diseases like Ebola even far more deadly and easier to spread than they are.

    2. Add a deadly nerve gas poison into a cities water reservoir. Some poisons are so toxic that even small amounts could kill large numbers of people.

  11. #11

    Default Re: what improvements should be made in the next generation nuclear power plants?

    If nuclear weapons were so easy to hide, we would've already seen it. If N. Korea and Iran cannot effectively hide their nuclear programs, then most other states can't. Chemical weapons are also tightly watched by WMD watchdogs. It's not as if there is only a fixation on nuclear weapons. However, back to what I was saying before. One of the reasons why nuclear power is also restricted is because it can be used to aid in production of nuclear weapons. I am a big proponent of nuclear energy, because the countries who have access to nukes are also the biggest polluters... So it's not as if we're putting anything at risk. High capital costs and inherent risk to the industry, means that this sort of thing needs government support. Unfortunately, I don't think any likely future POTUS approves of nuclear power. Which is a shame.

    Natural gas isn't too bad either though. I don't hate fossil fuels and ultimately, renewables have become very competitive, especially for residential use. Another 20 years, and solar panels or wind power may actually be a real consideration for home buyers. Right now I still think its better for me to invest in HVAC or a house remodel for efficiency gains, but after that, Tesla Powerwall and Solar power is up there on home investments.

  12. #12
    Magister Militum Flavius Aetius's Avatar Aetī Avēas!
    Join Date
    Mar 2010
    Location
    Rock Hill, SC
    Posts
    16,313
    Tournaments Joined
    1
    Tournaments Won
    0

    Default Re: what improvements should be made in the next generation nuclear power plants?

    sigh

    Current nuclear technology uses fuel that could be weaponized into weapons. That's by design and it dates back to the Manhattan project. At least from what I've read. Thorium based nuclear reactors, do not produce plutonium as a by product and therefore do not pose the same risk for nuclear proliferation.
    First of all, no they don't. Not easily, at least. All existing reactors will breed minute amounts of Pu-238, 239 (weapons grade), 240, 241, and 242. They are negligible in quantity and impossible to chemically separate from the fuel without massive centrifuge facilities. Operating nuclear reactors are also thermal neutron reactors, not fast neutron breeder or even thermal neutron breeder reactors. They are not useful for breeding enriched material in any meaningful sense.

    The oft-touted Thorium fuel cycle will in fact breed weapons-grade material as well. Uranium-233 is Fissile and Enriched, which is what you breed when you use Thorium-232 as a fuel source. All Thorium reactors have to be breeder reactors, because Thorium is not a viable fuel source until you breed it into a fissile Uranium. This breeding will still go up the chain and will result in the production of Plutonium isotopes as well. So yes, you can use Thorium to breed weapons grade material, mostly in the form of U-233.

    In order to stop this, most Thorium reactor designs try to make chemical separation of these isotopes impossible by keeping the fission (Caesium-137, etc.) products trapped in the fuel salt. That way if you try to extract enriched material from the reactor, you kill yourself with gamma radiation. And now you see why it's so ing hard to make a working Molten Salt reactor, because you have all these different isotopes with different chemical properties in your fuel salt and it's easy for several types to sublimate out and form blockages or create compounds that corrode containment.

    Here's the thing, the high capital cost of nuclear energy is actually its biggest strength. It's a lot easier to approve spending a ton of money on individual power plants, instead of attempting to fundamentally change the power grid. Once the reactors are built, they cost pennies to operate.
    No it's not and no they don't. Nuclear's high capital costs are because for the past 50 years a mix of fossil fuel interference and anti-nuclear activism (mostly funded by the fossil fuel industry) has set up the industry in the west to fail. Nuclear is not cheap to operate, the average nuclear plant employs more than 560 people when it should employ between 70 and 110 because for decades external interests have intentionally imposed an unnecessary regulatory burden in order to make it economically unviable. It is incredibly difficult for nuclear energy to compete when it's stuck using materials, parts, labor processes, manufacturing processes, construction process, etc. designed in the 1950's and 1960's. You can't use robotic arms to reduce the labor costs of nuclear energy because it takes years to get that kind of technology certified for use on reactor-grade components. And the certification for reactor grade components is insane. Parts used for the exact same purpose for the exact same specifications and tolerances in non-nuclear facilities have to be explicitly certified for nuclear use which drives up costs.

    And this has another impact in that it causes delays, which brings in biased financing models. Our financing of power facilities doesn't value generation out beyond about a 30 year lifespan due to a method of calculating risk in investment of these projects known as discounting. As a result, 5/8 of nuclear's generation is assigned zero value since nuclear plants have 80 year lifespans. Now throw in above-average interest rates and other factors on the WACC of plant construction and suddenly a $4 Billion Reactor actually costs $7 Billion. Now throw in delays. Over, and over, and over, again due to regulatory interference or sheer incompetence in project management and construction. Now it takes a year longer, now it costs 700 million dollars more due to that 10.25% interest rate. Then another delay, and another. Now your reactors cost $14.1 Billion each, the original projected cost of the two-unit plant. (Talking about the two new units at the Vogtle plant specifically there).

    The only way to fix this is to limit the discount rate at 5% instead of 10% and the either limit or subsidize the interest rate down to 2-3%. Either way, this only fixes financing bias, it does not fix sheer incompetence in project management that has been exhibited by western contractors.

    There is not that much of it. All of the used fuel ever produced by the commercial nuclear industry since the late 1950s would cover a football field to a depth of less than 10 yards. That might seem like a lot, but coal plants generate that same amount of waste every hour.
    If you want to do the math, the 1140 Megawatt Allen Steam Station ~7 miles from me generates approximately 310,000 metric tonnes of coal ash every year. One of the two 1185 Megawatt reactors from Catawba Nuclear Generating Station ~3 miles from me generates approximately 30 metric tonnes of spent nuclear fuel each year. A difference of about 10,330 to 1.

    That being said, the "football field" analogy only applies to Spent Nuclear Fuel. It doesn't account for the reinforced concrete containment surrounding used fuel bundles. Nuclear plants also generate a significant amount of low-level and medium-level radioactive waste each year, which is compressed and vitrified and stored in drums. Some of this is not radioactive and is only classified as such due to over-regulation. A lot of it is though. Generally speaking, those materials are typically "safe" within about 80 years or less, depending on the type and class of waste. But it's important to note that there are other waste streams. Uranium mining and enrichment also generates waste, but typically less than the mining and refining processes of other heavy or rare earth metals. Seawater extraction and fast neutron breeders would help eliminate much of that.

    A thorium fuel cycle could reduce the toxicity and calm down the public opinion about the nuclear industry.
    Ignoring the problems Protactinium causes in the Thorium fuel cycle and the fuel salt which is why we have yet to actually build a viable Thorium molten salt reactor reactor, no it doesn't. The Thorium fuel cycle has nothing to do with eliminating the radiotoxicity of the "waste" for the same reason Thorium is not special at all: it's just a fertile material with a viable fission fuel cycle. That's it.

    It instead has everything to do with the reactor physics, neutron coefficients, de Broigle wavelengths, and other particle physics. We design two types of nuclear reactor: Thermal neutron and Fast neutron. In a thermal neutron reactor we optimize the waveforms of the neutrons to achieve a slow and controlled fission cycle with very limited production of new neutrons (it's like 1.2 neutrons per fission). In a fast neutron reactor, we use higher-energy neutrons because different atoms have different neutron capture cross-sections that allow the neutrons to attach and cause a decay event which leads to fission. So we use a much wider spectrum of neutron energies and produce more neutrons per fission. This allows fast neutron reactors to fission the unenriched trans-Uranic isotopes that accumulate in reactors (Neptunium, Plutonium, Americium, etc.) which 1. eliminates some of the intermediate-lifespan waste products with higher radiotoxicities and 2. eliminates most of the proliferation-prone isotopes. The second thing this does is it allows the reactor to achieve a near-complete fuel burnup. 95% of nuclear waste produced from a standard thermal neutron light water reactor (CANDU reactors are slightly different because they use heavy water i.e. Deuterium) is usable Uranium fuel because they only achieve about a 3% to 5% burnup of the fuel. Fast neutron reactors can achieve as high as about 95%. This means that virtually the only thing left over is your fission products, which means the radiotoxicity of your material decays to near-natural levels within about 300 years.

    However this is true of all "nuclear waste." It's all radiologically relatively safe within about 300 years because of the short half-lives of the fission products. The reason "24,000 years" or other figures are tossed about is because of the old hot particle theory of Plutonium, which basically believed that ingestion of even nanograms of Plutonium was guaranteed to cause cancer and kill you. 24,000 years is the half-life of Plutonium-239. The worry is that Trans-Uranics will eventually breach the various containment systems of a geological repository, enter groundwater, and poison people. There are two problems with this:

    1. Hot Particle theory of Plutonium was conclusively disproven in 1975 when 25 people who had all inhaled atomic plutonium working at Los Alamos National Laboratory were still alive. Statistically, they had a >99.5% chance of being dead from lung cancer by that time. Not a single one of them had developed cancer.

    2. It takes about 10,000 years for any particles from spent nuclear fuel (which is a solid, not a liquid, contrary to popular belief) to make it out of a Geological repository and enter the groundwater, assuming everything goes wrong in the worst possible way. When POSIVA did this study when the Onkalo repository in Finland was proposed (which will be operational in 2022 or 2023), they found the average dose to a human would be 0.2 microsieverts (or the equivalent of eating two bananas, or the equivalent of living next to a nuclear power plant for 2 years). There is absolutely no evidence of increased cancer rates in doses below 100 millisieverts (so more than 500,000 times higher) and evidence for an increased risk of cancer for doses between 100 mSv and 200 mSv is shoddy at absolute best. And even if the Linear Non-Threshold model is true at doses of 100 to 200 mSv, your risk of cancer assuming continuous ingestion would only go up by 0.35% per year from the baseline 40% in modern Humans. And that's still 500,000 to 1,000,000 times more than what you'd actually be getting from that exposure to Plutonium.

    (Also, you still have to reprocess existing spent nuclear fuel into PUREX or MOX fuel before you can use it in a Fast Neutron Breeder, for mostly chemical reasons.)
    Last edited by Magister Militum Flavius Aetius; October 11, 2019 at 12:21 AM.

  13. #13

    Default Re: what improvements should be made in the next generation nuclear power plants?

    Quote Originally Posted by Magister Militum Flavius Aetius View Post
    sigh



    First of all, no they don't. Not easily, at least. All existing reactors will breed minute amounts of Pu-238, 239 (weapons grade), 240, 241, and 242. They are negligible in quantity and impossible to chemically separate from the fuel without massive centrifuge facilities. Operating nuclear reactors are also thermal neutron reactors, not fast neutron breeder or even thermal neutron breeder reactors. They are not useful for breeding enriched material in any meaningful sense.

    The oft-touted Thorium fuel cycle will in fact breed weapons-grade material as well. Uranium-233 is Fissile and Enriched, which is what you breed when you use Thorium-232 as a fuel source. All Thorium reactors have to be breeder reactors, because Thorium is not a viable fuel source until you breed it into a fissile Uranium. This breeding will still go up the chain and will result in the production of Plutonium isotopes as well. So yes, you can use Thorium to breed weapons grade material, mostly in the form of U-233.

    In order to stop this, most Thorium reactor designs try to make chemical separation of these isotopes impossible by keeping the fission (Caesium-137, etc.) products trapped in the fuel salt. That way if you try to extract enriched material from the reactor, you kill yourself with gamma radiation. And now you see why it's so ing hard to make a working Molten Salt reactor, because you have all these different isotopes with different chemical properties in your fuel salt and it's easy for several types to sublimate out and form blockages or create compounds that corrode containment.



    No it's not and no they don't. Nuclear's high capital costs are because for the past 50 years a mix of fossil fuel interference and anti-nuclear activism (mostly funded by the fossil fuel industry) has set up the industry in the west to fail. Nuclear is not cheap to operate, the average nuclear plant employs more than 560 people when it should employ between 70 and 110 because for decades external interests have intentionally imposed an unnecessary regulatory burden in order to make it economically unviable. It is incredibly difficult for nuclear energy to compete when it's stuck using materials, parts, labor processes, manufacturing processes, construction process, etc. designed in the 1950's and 1960's. You can't use robotic arms to reduce the labor costs of nuclear energy because it takes years to get that kind of technology certified for use on reactor-grade components. And the certification for reactor grade components is insane. Parts used for the exact same purpose for the exact same specifications and tolerances in non-nuclear facilities have to be explicitly certified for nuclear use which drives up costs.

    And this has another impact in that it causes delays, which brings in biased financing models. Our financing of power facilities doesn't value generation out beyond about a 30 year lifespan due to a method of calculating risk in investment of these projects known as discounting. As a result, 5/8 of nuclear's generation is assigned zero value since nuclear plants have 80 year lifespans. Now throw in above-average interest rates and other factors on the WACC of plant construction and suddenly a $4 Billion Reactor actually costs $7 Billion. Now throw in delays. Over, and over, and over, again due to regulatory interference or sheer incompetence in project management and construction. Now it takes a year longer, now it costs 700 million dollars more due to that 10.25% interest rate. Then another delay, and another. Now your reactors cost $14.1 Billion each, the original projected cost of the two-unit plant. (Talking about the two new units at the Vogtle plant specifically there).

    The only way to fix this is to limit the discount rate at 5% instead of 10% and the either limit or subsidize the interest rate down to 2-3%. Either way, this only fixes financing bias, it does not fix sheer incompetence in project management that has been exhibited by western contractors.



    If you want to do the math, the 1140 Megawatt Allen Steam Station ~7 miles from me generates approximately 310,000 metric tonnes of coal ash every year. One of the two 1185 Megawatt reactors from Catawba Nuclear Generating Station ~3 miles from me generates approximately 30 metric tonnes of spent nuclear fuel each year. A difference of about 10,330 to 1.

    That being said, the "football field" analogy only applies to Spent Nuclear Fuel. It doesn't account for the reinforced concrete containment surrounding used fuel bundles. Nuclear plants also generate a significant amount of low-level and medium-level radioactive waste each year, which is compressed and vitrified and stored in drums. Some of this is not radioactive and is only classified as such due to over-regulation. A lot of it is though. Generally speaking, those materials are typically "safe" within about 80 years or less, depending on the type and class of waste. But it's important to note that there are other waste streams. Uranium mining and enrichment also generates waste, but typically less than the mining and refining processes of other heavy or rare earth metals. Seawater extraction and fast neutron breeders would help eliminate much of that.



    Ignoring the problems Protactinium causes in the Thorium fuel cycle and the fuel salt which is why we have yet to actually build a viable Thorium molten salt reactor reactor, no it doesn't. The Thorium fuel cycle has nothing to do with eliminating the radiotoxicity of the "waste" for the same reason Thorium is not special at all: it's just a fertile material with a viable fission fuel cycle. That's it.

    It instead has everything to do with the reactor physics, neutron coefficients, de Broigle wavelengths, and other particle physics. We design two types of nuclear reactor: Thermal neutron and Fast neutron. In a thermal neutron reactor we optimize the waveforms of the neutrons to achieve a slow and controlled fission cycle with very limited production of new neutrons (it's like 1.2 neutrons per fission). In a fast neutron reactor, we use higher-energy neutrons because different atoms have different neutron capture cross-sections that allow the neutrons to attach and cause a decay event which leads to fission. So we use a much wider spectrum of neutron energies and produce more neutrons per fission. This allows fast neutron reactors to fission the unenriched trans-Uranic isotopes that accumulate in reactors (Neptunium, Plutonium, Americium, etc.) which 1. eliminates some of the intermediate-lifespan waste products with higher radiotoxicities and 2. eliminates most of the proliferation-prone isotopes. The second thing this does is it allows the reactor to achieve a near-complete fuel burnup. 95% of nuclear waste produced from a standard thermal neutron light water reactor (CANDU reactors are slightly different because they use heavy water i.e. Deuterium) is usable Uranium fuel because they only achieve about a 3% to 5% burnup of the fuel. Fast neutron reactors can achieve as high as about 95%. This means that virtually the only thing left over is your fission products, which means the radiotoxicity of your material decays to near-natural levels within about 300 years.

    However this is true of all "nuclear waste." It's all radiologically relatively safe within about 300 years because of the short half-lives of the fission products. The reason "24,000 years" or other figures are tossed about is because of the old hot particle theory of Plutonium, which basically believed that ingestion of even nanograms of Plutonium was guaranteed to cause cancer and kill you. 24,000 years is the half-life of Plutonium-239. The worry is that Trans-Uranics will eventually breach the various containment systems of a geological repository, enter groundwater, and poison people. There are two problems with this:

    1. Hot Particle theory of Plutonium was conclusively disproven in 1975 when 25 people who had all inhaled atomic plutonium working at Los Alamos National Laboratory were still alive. Statistically, they had a >99.5% chance of being dead from lung cancer by that time. Not a single one of them had developed cancer.

    2. It takes about 10,000 years for any particles from spent nuclear fuel (which is a solid, not a liquid, contrary to popular belief) to make it out of a Geological repository and enter the groundwater, assuming everything goes wrong in the worst possible way. When POSIVA did this study when the Onkalo repository in Finland was proposed (which will be operational in 2022 or 2023), they found the average dose to a human would be 0.2 microsieverts (or the equivalent of eating two bananas, or the equivalent of living next to a nuclear power plant for 2 years). There is absolutely no evidence of increased cancer rates in doses below 100 millisieverts (so more than 500,000 times higher) and evidence for an increased risk of cancer for doses between 100 mSv and 200 mSv is shoddy at absolute best. And even if the Linear Non-Threshold model is true at doses of 100 to 200 mSv, your risk of cancer assuming continuous ingestion would only go up by 0.35% per year from the baseline 40% in modern Humans. And that's still 500,000 to 1,000,000 times more than what you'd actually be getting from that exposure to Plutonium.

    (Also, you still have to reprocess existing spent nuclear fuel into PUREX or MOX fuel before you can use it in a Fast Neutron Breeder, for mostly chemical reasons.)

    All very good points. The highly radioactive material disappears after a few hundred years, and while.thr less radioactive material can stick around for thousands of years, it much less dangerous. The natural uranium you mined in the first place stays radioactive for billions of years.

    I am curious what nuclear design you would favor. The molten salt reactors have their advantages but also their disadvantages, same.as the others. I wonder about using something like the sodium-potasium mixiture that the Soviets used in the space based nuclear fission reactors. Na-K is molten at room temperature.

    While I.am leery about using materials that can react violently with water for cooling, apparenrly the Datsmics corporation made a liquid CPU cooler that used Na-K as the liquid.

  14. #14

    Default Re: what improvements should be made in the next generation nuclear power plants?

    Quote Originally Posted by Magister Militum Flavius Aetius View Post
    sigh
    First of all, no they don't. Not easily, at least. All existing reactors will breed minute amounts of Pu-238, 239 (weapons grade), 240, 241, and 242. They are negligible in quantity and impossible to chemically separate from the fuel without massive centrifuge facilities. Operating nuclear reactors are also thermal neutron reactors, not fast neutron breeder or even thermal neutron breeder reactors. They are not useful for breeding enriched material in any meaningful sense.

    The oft-touted Thorium fuel cycle will in fact breed weapons-grade material as well. Uranium-233 is Fissile and Enriched, which is what you breed when you use Thorium-232 as a fuel source. All Thorium reactors have to be breeder reactors, because Thorium is not a viable fuel source until you breed it into a fissile Uranium. This breeding will still go up the chain and will result in the production of Plutonium isotopes as well. So yes, you can use Thorium to breed weapons grade material, mostly in the form of U-233.

    In order to stop this, most Thorium reactor designs try to make chemical separation of these isotopes impossible by keeping the fission (Caesium-137, etc.) products trapped in the fuel salt. That way if you try to extract enriched material from the reactor, you kill yourself with gamma radiation. And now you see why it's so ing hard to make a working Molten Salt reactor, because you have all these different isotopes with different chemical properties in your fuel salt and it's easy for several types to sublimate out and form blockages or create compounds that corrode containment.
    I'm not sure why you're "disagreeing" here. Nothing you've said here contradicts what I've said. The issue isn't that current nuclear reactors can be used to make weapons-grade uranium, but that nuclear power can be used as a cover for achieving weapons grade material. That's not my opinion, that's consensus of the arms control community. And yes, Thorium is less dangerous for nuclear proliferation.

    No it's not and no they don't. Nuclear's high capital costs are because for the past 50 years a mix of fossil fuel interference and anti-nuclear activism (mostly funded by the fossil fuel industry) has set up the industry in the west to fail. Nuclear is not cheap to operate, the average nuclear plant employs more than 560 people when it should employ between 70 and 110 because for decades external interests have intentionally imposed an unnecessary regulatory burden in order to make it economically unviable. It is incredibly difficult for nuclear energy to compete when it's stuck using materials, parts, labor processes, manufacturing processes, construction process, etc. designed in the 1950's and 1960's. You can't use robotic arms to reduce the labor costs of nuclear energy because it takes years to get that kind of technology certified for use on reactor-grade components. And the certification for reactor grade components is insane. Parts used for the exact same purpose for the exact same specifications and tolerances in non-nuclear facilities have to be explicitly certified for nuclear use which drives up costs.

    And this has another impact in that it causes delays, which brings in biased financing models. Our financing of power facilities doesn't value generation out beyond about a 30 year lifespan due to a method of calculating risk in investment of these projects known as discounting. As a result, 5/8 of nuclear's generation is assigned zero value since nuclear plants have 80 year lifespans. Now throw in above-average interest rates and other factors on the WACC of plant construction and suddenly a $4 Billion Reactor actually costs $7 Billion. Now throw in delays. Over, and over, and over, again due to regulatory interference or sheer incompetence in project management and construction. Now it takes a year longer, now it costs 700 million dollars more due to that 10.25% interest rate. Then another delay, and another. Now your reactors cost $14.1 Billion each, the original projected cost of the two-unit plant. (Talking about the two new units at the Vogtle plant specifically there).

    The only way to fix this is to limit the discount rate at 5% instead of 10% and the either limit or subsidize the interest rate down to 2-3%. Either way, this only fixes financing bias, it does not fix sheer incompetence in project management that has been exhibited by western contractors.
    World Nuclear Association report on Economics of Nuclear Power.

    "The overall picture for current nuclear plants is that they are operating more efficiently than in the past and unit operating costs are low relative to those of alternative generating technologies. More output is being achieved from each reactor through improved performance and capacity uprates; their operation should continue for many years in the future, backed by the necessary investment in refurbishment. These improvements have now become routine and will be integrated into the construction of new nuclear plants"

    On economics of new plants.

    "The overall economics of new nuclear plants are dominated by their capital costs. In the assessment of new capacity, the studies quoted below show that capital costs including accrued interest account for around 65-85% of the levelised cost of a
    new nuclear plant
    14. For combined cycle gas turbine (CCGT) plants, usually around 20% of the levelised costs are accounted for by plant capital requirements, with most of the remainder being fuel requirements. For renewable electricity projects, the capital cost element can be as high as 90% because there is no fuel cost to using wind or sunlight as energy sources."

    So I disagree, my original assessment, that

    "Here's the thing, the high capital cost of nuclear energy is actually its biggest strength. It's a lot easier to approve spending a ton of money on individual power plants, instead of attempting to fundamentally change the power grid. Once the reactors are built, they cost pennies to operate."

    is largely correct.

    And again, to your other point, this is a question of politics. The Nuclear Regulatory Commission is an independent agency, and it's not hard to replace the entire Commission within an 8 year period. Like I said, the issue is financing the money. And I'd argue that it's a lot easier to secure a large chunk of money than it is to rebuild the entirety of the power grid and its regulatory structure to make us carbon-neutral.


    If you want to do the math, the 1140 Megawatt Allen Steam Station ~7 miles from me generates approximately 310,000 metric tonnes of coal ash every year. One of the two 1185 Megawatt reactors from Catawba Nuclear Generating Station ~3 miles from me generates approximately 30 metric tonnes of spent nuclear fuel each year. A difference of about 10,330 to 1.

    That being said, the "football field" analogy only applies to Spent Nuclear Fuel. It doesn't account for the reinforced concrete containment surrounding used fuel bundles. Nuclear plants also generate a significant amount of low-level and medium-level radioactive waste each year, which is compressed and vitrified and stored in drums. Some of this is not radioactive and is only classified as such due to over-regulation. A lot of it is though. Generally speaking, those materials are typically "safe" within about 80 years or less, depending on the type and class of waste. But it's important to note that there are other waste streams. Uranium mining and enrichment also generates waste, but typically less than the mining and refining processes of other heavy or rare earth metals. Seawater extraction and fast neutron breeders would help eliminate much of that.
    Okay, but the point is that high level waste is less than 5% of total waste generated by the nuclear industry. Waste is not exactly the most significant concern or an unsolved issue. The biggest issue is actually building nuclear plants. Everything else is a relatively minor issue.

  15. #15
    Magister Militum Flavius Aetius's Avatar Aetī Avēas!
    Join Date
    Mar 2010
    Location
    Rock Hill, SC
    Posts
    16,313
    Tournaments Joined
    1
    Tournaments Won
    0

    Default Re: what improvements should be made in the next generation nuclear power plants?

    I am curious what nuclear design you would favor.
    In terms of what we can build right now, immediately, to address climate change? KEPCO/KHNP's APR-1400 is probably the most cost-effective design. It has 18% of the features of most Gen III+ reactors because it's basically a System-80 reactor with some passive safety slapped onto it. It has a proven supply chain and KEPCO/KHNP have proven their ability to construct them, and have brought construction time for the design down from 10 to 6 years.

    The ESBWR is also nice but one has never been built. I would prefer to pick a Gen-II or Gen-II+ design like the System-80 or the WE 4-Loop, actually, but no utility would build one because passive safety has become "unofficially mandatory" on light water reactor designs. But the US actually has the manufacturing capability to forge parts for Gen-II/II+(1960's-80's) reactors, we do not have that capability for Gen-III/III+ reactors.

    In terms of what's most ideal? The best design I've seen remains MOLTEX's Stable Salt Reactor, a Uranium fuel cycle based Molten Salt Reactor which incorporates a 6 hour thermal storage system which allows the reactor to rapidly load follow renewables. Canada is working on licensing one for construction right now. It can also be scaled from 150 to 1200 MWe in plant size, making it useful for a wide range of applications and locations.

    Small Modular Reactors have known for a long time to have serious issues with O&M costs, I don't expect that Water-cooled SMR's will succeed unless someone invests in GE Hitachi's BWRX-300 (a downsized ESBWR) and they get a committed buyer, since its concrete and other material usage is so much vastly lower and smaller that it may actually stand to live up to its predicted pricetag of $2700 per kWe.

    While I.am leery about using materials that can react violently with water for cooling, apparenrly the Datsmics corporation made a liquid CPU cooler that used Na-K as the liquid.
    I have no issues with liquid sodium fast neutron breeder reactors. We've used them for decades and they're easy to operate and maintain. Fermi-1 only happened because an unnecessary test was mandated and one of the Zircalloy plates from that test broke loose causing a partial fuel melt. It was repaired and brought back into service until funding for it was cut off in 1972.

    but that nuclear power can be used as a cover for achieving weapons grade material. That's not my opinion, that's consensus of the arms control community.
    Not really. In order to build a nuclear reactor you have to agree to international arms control standards and have to allow IAEA inspection. Nuclear Power is a terrible cover for weapons production as a result. If you want a bomb, you build a secret reactor like Israel and North Korea did.

    "Here's the thing, the high capital cost of nuclear energy is actually its biggest strength. It's a lot easier to approve spending a ton of money on individual power plants, instead of attempting to fundamentally change the power grid. Once the reactors are built, they cost pennies to operate."
    No it's not. Those reactors that are presently operating with an average LCOE of $33 per MWh (they range from $22 to $38 per MWh) were built at costs of approximately $600 to $3200 per kWe, with a string of reactors built from 1966 to 1968 for $600 per kWe remaining the cheapest technology ever built. First of all, this is double what it was in 2002, which was about $17 to $24 per MWh inflation-adjusted, largely due to the post-Fukushima retrofits required on many plants. Second of all, modern nuclear reactors due to high capital costs and financing currently range from $2700 to $8800 per kWe. Western designs, specifically, cost between $6300 and $8800 per kWe. The LCOE of these plants usually sits at $120 to $150 per MWh now, which is far higher than the operating costs of existing plants (which have been paid off for decades). The $128 per MWh cost of Vogtle units 3 and 4 will result in higher electricity costs until the plant has refinanced its loans, then it will drop to the national average after that 20 year period.

    Like I said, the issue is financing the money.
    The fundamental issue is that the nuclear power industry, US utilities, and US construction firms are completely and utterly incompetent, use horrendous business practices, and cannot manage large infrastructure projects. If nuclear power, high speed rail, etc. want to be competitive, we have to fix these problems.

    And I'd argue that it's a lot easier to secure a large chunk of money than it is to rebuild the entirety of the power grid and its regulatory structure to make us carbon-neutral.
    That depends on how storage costs go, which will likely reach $150 per MWh in 2021. Right now, it becomes more expensive to build more wind and solar than over-budget nuclear at 52% VRE+storage penetration in the US. As storage costs fall, the economics may favor a 100% renewable grid. However, the issue is whether or not they can achieve supply reliability, not so much the economics.
    Last edited by Magister Militum Flavius Aetius; October 11, 2019 at 08:00 PM.

  16. #16

    Default Re: what improvements should be made in the next generation nuclear power plants?

    Quote Originally Posted by Magister Militum Flavius Aetius View Post
    Not really. In order to build a nuclear reactor you have to agree to international arms control standards and have to allow IAEA inspection. Nuclear Power is a terrible cover for weapons production as a result. If you want a bomb, you build a secret reactor like Israel and North Korea did.
    This is irrelevant. Regulating dual use technology doesn't stop it from being dual use. And it's terrible. It takes a long time to develop nuclear power. Your chances of getting caught are significant. Meanwhile, pursuing nuclear energy is a lot more palatable and it puts you significantly closer towards acquiring nuclear weapons.

    No it's not. Those reactors that are presently operating with an average LCOE of $33 per MWh (they range from $22 to $38 per MWh) were built at costs of approximately $600 to $3200 per kWe, with a string of reactors built from 1966 to 1968 for $600 per kWe remaining the cheapest technology ever built. First of all, this is double what it was in 2002, which was about $17 to $24 per MWh inflation-adjusted, largely due to the post-Fukushima retrofits required on many plants. Second of all, modern nuclear reactors due to high capital costs and financing currently range from $2700 to $8800 per kWe. Western designs, specifically, cost between $6300 and $8800 per kWe. The LCOE of these plants usually sits at $120 to $150 per MWh now, which is far higher than the operating costs of existing plants (which have been paid off for decades). The $128 per MWh cost of Vogtle units 3 and 4 will result in higher electricity costs until the plant has refinanced its loans, then it will drop to the national average after that 20 year period.
    Again, you're losing me. The high capital costs of nuclear reactors are my entire point. Nuclear energy has high capital costs and low O&M costs. This is the same reason why renewable energy is also cited as being "better" than fossil fuels (aside from the whole "green" thing). Because the LCOE of both nuclear and renewables are heavily skewed towards capital costs with low O&M. So you can keep saying "No" but I don't get what you're saying "No" too. High capital costs are an advantage from a policy perspective.

    The fundamental issue is that the nuclear power industry, US utilities, and US construction firms are completely and utterly incompetent, use horrendous business practices, and cannot manage large infrastructure projects. If nuclear power, high speed rail, etc. want to be competitive, we have to fix these problems.
    Bold claim.

    That depends on how storage costs go, which will likely reach $150 per MWh in 2021. Right now, it becomes more expensive to build more wind and solar than over-budget nuclear at 52% VRE+storage penetration in the US. As storage costs fall, the economics may favor a 100% renewable grid. However, the issue is whether or not they can achieve supply reliability, not so much the economics.
    That's because per unit costs of renewable energy are low. Not because it's inherently more cost effective. Energy storage is scalable, as are solar panels and wind turbines. Nuclear energy is not.
    Last edited by Love Mountain; October 12, 2019 at 12:14 AM.

  17. #17
    Magister Militum Flavius Aetius's Avatar Aetī Avēas!
    Join Date
    Mar 2010
    Location
    Rock Hill, SC
    Posts
    16,313
    Tournaments Joined
    1
    Tournaments Won
    0

    Default Re: what improvements should be made in the next generation nuclear power plants?

    Nuclear energy has high capital costs and low O&M costs.
    And those low O&M costs don't become a benefit until 20 years after reactor completion.

    Bold claim.
    Backed by MIT's massive 2018 white paper, the analysis of Third Way in Britain, and multiple other organizations. http://energy.mit.edu/research/futur...trained-world/

    That's because per unit costs of renewable energy are low. Not because it's inherently more cost effective. Energy storage is scalable, as are solar panels and wind turbines. Nuclear energy is not.
    I don't get how you think nuclear energy isn't scalable. The entire reason we've moved to large reactors is because it costs effectively no more for a 1400 MWe reactor than it does for a 900 MWe reactor. Successive builds are also known to reduce costs of construction by 12 to 18% and reduce construction times.

  18. #18

    Default Re: what improvements should be made in the next generation nuclear power plants?

    Quote Originally Posted by Magister Militum Flavius Aetius View Post
    And those low O&M costs don't become a benefit until 20 years after reactor completion.
    ??? And? How does that dispute anything I've said?

    Backed by MIT's massive 2018 white paper, the analysis of Third Way in Britain, and multiple other organizations. http://energy.mit.edu/research/futur...trained-world/
    I can already guarantee you, without reading it, that the report doesn't say that.

    I don't get how you think nuclear energy isn't scalable. The entire reason we've moved to large reactors is because it costs effectively no more for a 1400 MWe reactor than it does for a 900 MWe reactor. Successive builds are also known to reduce costs of construction by 12 to 18% and reduce construction times.
    Because it makes no sense to build smaller reactors. You'd never build nuclear power for a small town. It's simply economically unfeasible. Wind turbines and solar panels are infinitely more deployable than nuclear power. Currently, nuclear power can only exist if the government supports it. On the other hand, renewables can be purchased by pretty much anyone.

  19. #19
    Magister Militum Flavius Aetius's Avatar Aetī Avēas!
    Join Date
    Mar 2010
    Location
    Rock Hill, SC
    Posts
    16,313
    Tournaments Joined
    1
    Tournaments Won
    0

    Default Re: what improvements should be made in the next generation nuclear power plants?

    ??? And? How does that dispute anything I've said?
    I'm saying that high capital costs are a problem, not a benefit. Solar has incredibly low capital costs AND low O&M costs.

    I can already guarantee you, without reading it, that the report doesn't say that.
    Then you better read it instead of making assumptions about nuclear construction which you seem to be grossly misinformed on.

    Because it makes no sense to build smaller reactors. You'd never build nuclear power for a small town. It's simply economically unfeasible. Wind turbines and solar panels are infinitely more deployable than nuclear power. Currently, nuclear power can only exist if the government supports it. On the other hand, renewables can be purchased by pretty much anyone.
    UAMPS just purchased the NuScale (twelve 60 MWe reactors) plant at Idaho national laboratories. Each member is a small town. They funded NuScale the exact same way Renewable projects are funded.

  20. #20
    Genava's Avatar Centenarius
    Join Date
    Mar 2009
    Location
    Geneva
    Posts
    888

    Default Re: what improvements should be made in the next generation nuclear power plants?

    Quote Originally Posted by Sukiyama View Post
    Current nuclear technology uses fuel that could be weaponized into weapons. That's by design and it dates back to the Manhattan project. At least from what I've read. Thorium based nuclear reactors, do not produce plutonium as a by product and therefore do not pose the same risk for nuclear proliferation.
    Thorium: Proliferation warnings on nuclear 'wonder-fuel' https://phys.org/news/2012-12-thoriu...nder-fuel.html

    Spoiler Alert, click show to read: 

    Thorium is being touted as an ideal fuel for a new generation of nuclear power plants, but in a piece in this week's Nature, researchers suggest it may not be as benign as portrayed.

    The element thorium, which many regard as a potential nuclear "wonder-fuel", could be a greater proliferation threat than previously thought, scientists have warned.

    Writing in a Comment piece in the new issue of the journal, Nature, nuclear energy specialists from four British universities suggest that, although thorium has been promoted as a superior fuel for future nuclear energy generation, it should not be regarded as inherently proliferation resistant. The piece highlights ways in which small quantities of uranium-233, a material useable in nuclear weapons, could be produced covertly from thorium, by chemically separating another isotope, protactinium-233, during its formation.

    The chemical processes that are needed for protactinium separation could possibly be undertaken using standard lab equipment, potentially allowing it to happen in secret, and beyond the oversight of organisations such as the International Atomic Energy Agency (IAEA), the paper says.

    The authors note that, from previous experiments to separate protactinium-233, it is feasible that just 1.6 tonnes of thorium metal would be enough to produce 8kg of uranium-233 which is the minimum amount required for a nuclear weapon. Using the process identified in their paper, they add that this could be done "in less than a year."

    "Thorium certainly has benefits, but we think that the public debate regarding its proliferation-resistance so far has been too one-sided," Dr Steve Ashley, from the Department of Engineering at the University of Cambridge and the paper's lead author, said.

    "Small-scale chemical reprocessing of irradiated thorium can create an isotope of uranium – uranium-233 – that could be used in nuclear weapons. If nothing else, this raises a serious proliferation concern."

    Thorium is widely seen as an alternative nuclear fuel source to uranium. It is thought to be three to four times more naturally abundant, with substantial deposits spread around the world. Some countries, including the United States and the United Kingdom, are exploring its potential use as fuel in civil nuclear energy programmes.

    Alongside its abundance, one of thorium's most attractive features is its apparent resistance to nuclear proliferation, compared with uranium. This is because thorium-232, the most commonly found type of thorium, cannot sustain nuclear fission itself. Instead, it has to be broken down through several stages of radioactive decay. This is achieved by bombarding it with neutrons, so that it eventually decays into uranium-233, which can undergo fission.

    As a by-product, the process also produces the highly radiotoxic isotope uranium-232. Because of this, producing uranium-233 from thorium requires very careful handling, remote techniques and heavily-shielded containment chambers. That implies the use of facilities large enough to be monitored.

    The paper suggests that this obstacle to developing uranium-233 from thorium could, in theory, be circumvented. The researchers point out that thorium's decay is a four-stage process: isotopically pure thorium-232 breaks down into thorium-233. After 22 minutes, this decays into protactinium-233. And after 27 days, it is this substance which decays into uranium-233, capable of undergoing nuclear fission.

    Ashley and colleagues note from previously existing literature that protactinium-233 can be chemically separated from irradiated thorium. Once this has happened, the protactinium will decay into pure uranium-233 on its own, with little radiotoxic by-product.

    "The problem is that the neutron irradiation of thorium-232 could take place in a small facility," Ashley said. "It could happen in a research reactor, of which there are about 500 worldwide, which may make it difficult to monitor."

    The researchers note that from an early small-scale experiment to separate protactinium-233, approximately 200g of thorium metal could produce 1g of protactinium-233 (and therefore the same amount of uranium-233) if exposed to neutrons at the levels typically found in power reactors for a month. This means that 1.6 tonnes of thorium metal would be needed to produce 8kg of uranium-233. They also point out that protactinium separation already happens, as part of other chemical processes.

    Given the need for access to a research or power reactor to irradiate thorium, the paper argues that the most likely security threat is from potential wilful proliferator states. As a result, the authors strongly recommend that appropriate monitoring of thorium-related nuclear technologies should be performed by organisations like the IAEA. The report also calls for steps to be taken to control the short-term irradiation of thorium-based materials with neutrons, and for in-plant reprocessing of thorium-based fuels to be avoided.

    "The most important thing is to recognise that thorium is not a route to a nuclear future free from proliferation risks, as some people seem to believe," Ashley added. "The emergence of thorium technologies will bring problems as well as benefits. We need more debate on the associated risks, if we want a safer nuclear future."

    The researchers are: Dr Stephen F. Ashley and Dr. Geoffrey T. Parks from the University of Cambridge; Professor William J. Nuttall from The Open University; Professor Colin Boxall from Lancaster University; Professor Robin W. Grimes from Imperial College London.

    Copies of the comment piece in this week's Nature are available on request. Interviews with Dr Steve Ashley can also be arranged by contacting Tom Kirk.


    Thorium fuel has risks https://www.nature.com/articles/492031a

    Spoiler Alert, click show to read: 
    Simple chemical pathways open up proliferation possibilities for the proposed nuclear 'wonder fuel', warn Stephen F. Ashley and colleagues.

    Thorium is being touted as a potential wonder fuel. Proponents believe that this element could be used in a new generation of nuclear-power plants to produce relatively safe, low-carbon energy with more resistance against potential nuclear-weapons proliferation than uranium. Although thorium offers some benefits, we contend that the public debate is too one-sided: small-scale chemical reprocessing of irradiated thorium can create an isotope of uranium that could be used in nuclear weapons, raising proliferation concerns.

    Global stocks of thorium are uncertain, but the element is thought to be three to four times more naturally abundant than uranium (see 'World thorium deposits'). The silver-white metal is often encountered as oxide waste from the mining of rare-earth elements, and substantial thorium deposits are found in Australia, Brazil, Turkey, Norway, China, India and the United States. The last three of these, together with the United Kingdom, are exploring the potential use of thorium in civil nuclear-energy programmes.

    One of many voices proposing the deployment of new thorium-based molten salt reactors (see page 26) is the Weinberg Foundation, a non-profit organization based in London that promotes thorium-fuelled technologies to combat climate change. Molten salt reactors were developed in the 1960s and use liquid nuclear fuels, that can incorporate thorium, rather than solid fuel rods. They are claimed to be more efficient and less susceptible to meltdown-related accidents than existing technologies. Small modular reactors, such as high-temperature gas-cooled reactors that use solid thorium-based fuels, are also being pursued, most notably by China.

    Naturally-occurring thorium is made up almost entirely of thorium-232, an isotope that is unable to sustain nuclear fission. When bombarded with neutrons, thorium is converted through a series of decays into uranium-233, which is fissile and long-lived — its half-life is 160,000 years. A side product is uranium-232, which decays into other isotopes that give off intense γ-radiation that is difficult to shield against. Spent thorium fuel is typically difficult to handle and thus resistant to proliferation.

    We are concerned, however, that other processes, which might be conducted in smaller facilities, could be used to convert 232Th into 233U while minimizing contamination by 232U, thus posing a proliferation threat. Notably, the chemical separation of an intermediate isotope — protactinium-233 — that decays into 233U is a cause for concern.

    Thorium is not a route to a nuclear future that is free from proliferation risks. Policies should be strengthened around thorium's use in declared nuclear activities, and greater vigilance is needed to protect against surreptitious activities involving this element.

    Protactinium pathway

    The decay path of thorium is well understood. If bombarded with neutrons, isotopically pure 232Th forms 233Th, which has a half-life of 22 minutes and β-decays to 233Pa. That isotope has a half-life of 27 days and β-decays to 233U, which can undergo fission. The International Atomic Energy Agency (IAEA) considers 8 kilograms of 233U to be enough to construct a nuclear weapon1. Thus, 233U poses proliferation risks.

    Although 233U is not used today in commercial reactors, the United States accumulated two tonnes of it during the cold war. Plans to dispose of much of it by burial are controversial and pose security and safety risks, according to a 2012 report2.

    The chemical reprocessing needed to separate 233U from spent nuclear fuel requires major infrastructure, such as large reprocessing plants, which are difficult to hide. With thorium fuel, the presence of highly radiotoxic 232U means that the spent fuel must be handled using remote techniques in heavily-shielded containment chambers.

    After irradiating thorium with neutrons for around one month, chemical separation of 233Pa could yield minimal 232U contamination, making the 233U-rich product easier to handle. If pure 233Pa can be extracted, then it merely needs to be left to decay to produce pure 233U. The problem is that neutron irradiation of 232Th could take place in a small facility, such as a research reactor, of which around 500 exist worldwide. The 232Th need not be part of a nuclear-fuel assembly nor be involved in energy generation.

    It has been demonstrated that around 200 g of thorium metal could produce 1 g of 233Pa — and hence 1 g of 233U — if exposed to neutrons at levels typically found in power reactors and some research reactors for a month, followed by protactinium separation3. Thus, only 1.6 tonnes of thorium metal would be required to produce the 8 kg of 233U required for a weapon. This amount of 233U could feasibly be obtained by this process in less than a year.

    The separation of protactinium from thorium is not new. We highlight two well-known chemical processes — acid-media techniques3,4 and liquid bismuth reductive extraction5,6,7 (see 'Ways to obtain pure protactinium') — that are causes for concern, although there may be others. Both methods use standard nuclear-lab equipment and hot cells — containment chambers in which highly radioactive materials can be manipulated safely. Such apparatus is not necessarily subject to IAEA safeguards.

    The most common acid-media technique uses manganese dioxide to precipitate the protactinium as protactinium oxide4. Any radiotoxic uranium by-products are dissolved in acid and removed during the precipitation. This method was used in the 1960s by researchers at Oak Ridge National Laboratory in Tennessee to extract 1 g of 233Pa from 200 g of an irradiated thorium compound3.

    The main difficulty is that β-decay from each gram of 233Pa produces 50 watts of heat3, which complicates the handling. Scaling up the production of 233Pa would not be easy, but given the possibility of parallel processing of small quantities, our concerns over this technique remain.

    A second chemical method, suggested in the 1970s (refs 5,7), is being revisited for next-generation molten salt reactors (see, for example, ref. 8). These use thorium-based liquid fuels containing a fluoride-based salt with the typical composition 7LiF–BeF2–ThF4–UF4. The process is pyrochemically based, using high temperature oxidation–reduction reactions. It involves first fluorination and then extraction using molten bismuth to obtain protactinium.

    The infrastructure for pyrochemistry is more complex than for acid-media techniques, and scaling it up is even more challenging. Pyrochemical reprocessing technologies are in their infancy. But we are concerned that such a technique could be used in small batches9 to slowly accumulate protactinium.

    Given the need for access to a research or power reactor to irradiate thorium, the most likely security threat stems not from terrorist organizations but from wilful proliferating nation states. We have three main concerns:

    First, nuclear-energy technologies that involve irradiation of thorium fuels for short periods could be used covertly to accumulate quantities of 233U by parallel or batch means, perhaps without raising IAEA proliferation flags.

    Second, the infrastructure required to undertake the chemical partitioning of protactinium could be acquired and established surreptitiously in a small laboratory.

    Third, state proliferators could seek to use thorium to acquire 233U for weapons production. These three points should be included in debates on the proliferation attributes of thorium.

    Monitoring thorium

    The emergence of thorium technologies will bring problems as well as benefits. There is a need for appropriate monitoring of thorium-related nuclear technologies within declared and undeclared facilities. The IAEA and the Nuclear Suppliers Group, the group of countries that controls nuclear exports, have a role to play in observing such developments.

    Steps are needed to control the short-term irradiation of thorium-based materials with neutrons. Similarly, civil nuclear-fuel cycles involving in-plant reprocessing of thorium-based fuels should be avoided.

    Hot cells are a key technology in protactinium separation. The Additional Protocol of the Nuclear Non-Proliferation Treaty10 requires disclosure of large hot-cell facilities. The associated size cut-off is potentially important with protactinium pathways in mind. We are comforted that large hot-cell facilities are treated by the IAEA as nuclear technologies that can be 'dual use' for military or peaceful purposes, but concerns will always remain about hidden undeclared facilities.

    Thorium is not as benign as has been suggested and we call for greater debate on its associated risks. In this way, a safer nuclear future can be assured.
    Open Access Defenders Step Up to Save ‘Pirate Bay of Science’
    https://nerdist.com/article/open-acc...brary-genesis/

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •