6 ms·

About a year ago, a study was published which looked at 3 types of SMRs and found that they produced more waste per unit energy produced, in part because smalle

by abeppu 3y ago

About a year ago, a study was published which looked at 3 types of SMRs and found that they produced more waste per unit energy produced, in part because smaller reactors have more neutron leakage. Of course, this new reactor was not one of the designs analyzed, but I wonder if the same concerns apply. https://news.stanford.edu/2022/05/30/small-modular-reactors-produce-high-levels-nuclear-waste/ https://news.stanford.edu/2022/05/30/small-modular-reactors-... https://www.pnas.org/doi/full/10.1073/pnas.2111833119 https://www.pnas.org/doi/full/10.1073/pnas.2111833119

pitaj 3y ago
There's such a small amount of high-level waste that even a 30x increase isn't going to be that big of an issue, even if you don't count waste recycling.
- bradfa 3y ago
  Recycling or reprocessing of used nuclear fuel is not done in the USA currently. I'm curious if this will change in the near future with what appears to be renewed interest in nuclear power plants. Being able to renew what's currently considered a waste seems like a logical thing to do but obviously it's not financially worthwhile in the USA currently: https://www.nrc.gov/materials/reprocessing.html https://www.nrc.gov/materials/reprocessing.html
  - pfdietz 3y ago
    Almost certainly not, because with the nuclear industry shrinking uranium will remain cheap. And if uranium is cheap, reprocessing costs more than it's worth.
    - pitaj 3y ago
      You should compare not just the cost of new uranium but also disposal of the spent fuel.
      - pfdietz 3y ago
        Reprocessing doesn't reduce disposal cost. The cheapest way to dispose of spent fuel is simply sealing it in dry casks and letting the magic of nonzero interest rates and radioactive decay do their work. Even if you want to reprocess the fuel at some point, it's cheaper to wait rather than do it immediately.
  - nine_k 3y ago
    There are proliferation concerns because spent fuel has plutonium, and burning the waste in the breeder produces (and then burns) more plutonium. I personally find these concerns obsolete, but they still get mentioned.
beefman 3y ago
This paper's findings have no basis in reality. Perhaps because it was written by three people with a political angle and no relevant training.
- abeppu 3y ago
  I'm not a nuclear engineer and have no relevant training, and from my layperson's position am not immediately able to see what's wrong here. Would you mind expanding on what's wrong with the paper from your perspective? I don't know how to weight your remark about the qualifications of the authors. I would expect that PNAS used reviewers with sufficient expertise in the field.
  - beefman 3y ago
    Information about the authors is in the report, and on the web. It's not possible to debunk every bit of nonsense written about nuclear energy. And often better not to dignify it by trying. Here goes anyway: A reactor is a can filled with fuel. Per unit of energy liberated and modulo every other degree of freedom in the design, the size of the can has nothing to do with the amount of fuel or its disposition. The size of the can does have something to do with the size of the can, per unit of energy liberated. That's because volume scales as radius cubed while surface area scales as radius squared, and the energy depends only on the volume. So in that, the authors have a point. But the details they provide have little to do with it, and some are misleading or wrong. And why we should care, or how much we should care, about the amount of cans is not investigated. The result is that there's nothing in this report anyone could use to inform a decision. Edit: It has been disputed elsewhere... https://www.powermag.com/small-modular-reactors-arent-difficult-nuclear-waste-generators/ https://www.powermag.com/small-modular-reactors-arent-diffic... https://www.anl.gov/article/argonne-releases-small-modular-reactor-waste-analysis-report https://www.anl.gov/article/argonne-releases-small-modular-r... https://neutronbytes.com/2022/05/31/stanfords-questionable-study-on-spent-nuclear-fuel-for-smrs/ https://neutronbytes.com/2022/05/31/stanfords-questionable-s...
    - abeppu 3y ago
godelski 3y ago
I'm not sure why this is surprising to anyone, but I will note that the discussion is muddled. The paper notes > The excess waste volume is attributed to the use of neutron reflectors and/or of chemically reactive fuels and coolants in SMR designs. That said, volume is not the most important evaluation metric; rather, geologic repository performance is driven by the decay heat power and the (radio-)chemistry of spent nuclear fuel, for which SMRs provide no benefit. There should be no surprise that smaller reactors require more shielding when normalized to output energy. Scaling has advantages. More importantly, the muddling comes from the non-nuanced discussion of waste that is ever so common. We cannot conflate high level waste with low/mid level waste. One is dangerous, the other isn't. Long lives mean lower danger. We should know this from first principles: radioactivity is shedding of mass, the faster you shed mass the shorter you live. And this is exponential too! Iodine-129, which has a half life of 1.57×10^7 yr has a decay energy of 0.189 MeV through beta- decay (electron). On the other hand, Sodium-24 has a half-life of 15hrs and has a 1.39MeV beta+ decay (10x) followed by a 2.76MeV gamma decay and a 1.38MeV gamma decay, both happening in a fraction of a fraction of a second and reaching a stable ground state (the most common form of magnesium, who's main danger is flammability). At a 1cm distance, a 10uCi sample of I-129 results in a dosage of 57uSv/hr while 10uCi of Na-24 results in 1609uSv/hr, and almost 30x difference. Public dose limit is 1mSv/yr and occupational is 20mSv/yr. That's the difference of 17.5hrs (351hrs occupational) vs 37 minutes (12hrs occupational) to reach recommended limits. This is all before we even start talking about cancer risk (there's >an order of magnitude safety. 1Sv single does requires intervention but is non-fatal), and ease of shielding (you can assume that one is easier to shield) or how natural radiation exposure is around 2mSv/yr and a flight crew going NYC-Tokyo gets about 9mSv/yr. Conflating these is not helpful to the discussion. Our required storage techniques are vastly different for these components and so our perception also needs to be. The article there is making the same mistake that they are criticizing. They criticize studies for only looking at spent fuel, saying that it offers little insight into danger and storage concerns. But then they only focus on mid and low-level waste (i.e. mass) which similarly offers little insight. Complex systems require complex discussions. This is why public conversations like we have on HN and Reddit are less than useless. It is a bunch of armchair experts who have convinced themselves that they understand an extremely complex subject and confidently discuss the issues in naive and inaccurate ways. At the end of the day we live in a specialized world and we have to accept that we need to learn on expert decisions because there is no possible way that we can have (high) expertise knowledge in more than one or two domains. This isn't a jab at your (anyone who is reading) intelligence, but a fact of our world. I don't want to discourage people from learning more about these complex subjects, but I do want to discourage confident discussions when one doesn't have domain expertise. Fruitful conversations can be had if we discuss under this premise but if we don't we just muddle the conversation and there's a good chance we actually decrease our domain knowledge.
petre 3y ago
Yes, the scientists who published it are a previous chairman of the NRC specialized in public policies, two geologists, a director of communications. I'd put more trust in the Union of Concerned Scientists.

by abeppu 3y ago

pitaj 3y ago

There's such a small amount of high-level waste that even a 30x increase isn't going to be that big of an issue, even if you don't count waste recycling.

bradfa 3y ago
Recycling or reprocessing of used nuclear fuel is not done in the USA currently. I'm curious if this will change in the near future with what appears to be renewed interest in nuclear power plants. Being able to renew what's currently considered a waste seems like a logical thing to do but obviously it's not financially worthwhile in the USA currently: https://www.nrc.gov/materials/reprocessing.html https://www.nrc.gov/materials/reprocessing.html
- pfdietz 3y ago
  Almost certainly not, because with the nuclear industry shrinking uranium will remain cheap. And if uranium is cheap, reprocessing costs more than it's worth.
  - pitaj 3y ago
    You should compare not just the cost of new uranium but also disposal of the spent fuel.
    - pfdietz 3y ago
      Reprocessing doesn't reduce disposal cost. The cheapest way to dispose of spent fuel is simply sealing it in dry casks and letting the magic of nonzero interest rates and radioactive decay do their work. Even if you want to reprocess the fuel at some point, it's cheaper to wait rather than do it immediately.
- nine_k 3y ago
  There are proliferation concerns because spent fuel has plutonium, and burning the waste in the breeder produces (and then burns) more plutonium. I personally find these concerns obsolete, but they still get mentioned.

beefman 3y ago

This paper's findings have no basis in reality. Perhaps because it was written by three people with a political angle and no relevant training.

abeppu 3y ago
I'm not a nuclear engineer and have no relevant training, and from my layperson's position am not immediately able to see what's wrong here. Would you mind expanding on what's wrong with the paper from your perspective? I don't know how to weight your remark about the qualifications of the authors. I would expect that PNAS used reviewers with sufficient expertise in the field.
- beefman 3y ago
  Information about the authors is in the report, and on the web. It's not possible to debunk every bit of nonsense written about nuclear energy. And often better not to dignify it by trying. Here goes anyway: A reactor is a can filled with fuel. Per unit of energy liberated and modulo every other degree of freedom in the design, the size of the can has nothing to do with the amount of fuel or its disposition. The size of the can does have something to do with the size of the can, per unit of energy liberated. That's because volume scales as radius cubed while surface area scales as radius squared, and the energy depends only on the volume. So in that, the authors have a point. But the details they provide have little to do with it, and some are misleading or wrong. And why we should care, or how much we should care, about the amount of cans is not investigated. The result is that there's nothing in this report anyone could use to inform a decision. Edit: It has been disputed elsewhere... https://www.powermag.com/small-modular-reactors-arent-difficult-nuclear-waste-generators/ https://www.powermag.com/small-modular-reactors-arent-diffic... https://www.anl.gov/article/argonne-releases-small-modular-reactor-waste-analysis-report https://www.anl.gov/article/argonne-releases-small-modular-r... https://neutronbytes.com/2022/05/31/stanfords-questionable-study-on-spent-nuclear-fuel-for-smrs/ https://neutronbytes.com/2022/05/31/stanfords-questionable-s...
  - abeppu 3y ago

godelski 3y ago

I'm not sure why this is surprising to anyone, but I will note that the discussion is muddled. The paper notes > The excess waste volume is attributed to the use of neutron reflectors and/or of chemically reactive fuels and coolants in SMR designs. That said, volume is not the most important evaluation metric; rather, geologic repository performance is driven by the decay heat power and the (radio-)chemistry of spent nuclear fuel, for which SMRs provide no benefit. There should be no surprise that smaller reactors require more shielding when normalized to output energy. Scaling has advantages. More importantly, the muddling comes from the non-nuanced discussion of waste that is ever so common. We cannot conflate high level waste with low/mid level waste. One is dangerous, the other isn't. Long lives mean lower danger. We should know this from first principles: radioactivity is shedding of mass, the faster you shed mass the shorter you live. And this is exponential too! Iodine-129, which has a half life of 1.57×10^7 yr has a decay energy of 0.189 MeV through beta- decay (electron). On the other hand, Sodium-24 has a half-life of 15hrs and has a 1.39MeV beta+ decay (10x) followed by a 2.76MeV gamma decay and a 1.38MeV gamma decay, both happening in a fraction of a fraction of a second and reaching a stable ground state (the most common form of magnesium, who's main danger is flammability). At a 1cm distance, a 10uCi sample of I-129 results in a dosage of 57uSv/hr while 10uCi of Na-24 results in 1609uSv/hr, and almost 30x difference. Public dose limit is 1mSv/yr and occupational is 20mSv/yr. That's the difference of 17.5hrs (351hrs occupational) vs 37 minutes (12hrs occupational) to reach recommended limits. This is all before we even start talking about cancer risk (there's >an order of magnitude safety. 1Sv single does requires intervention but is non-fatal), and ease of shielding (you can assume that one is easier to shield) or how natural radiation exposure is around 2mSv/yr and a flight crew going NYC-Tokyo gets about 9mSv/yr. Conflating these is not helpful to the discussion. Our required storage techniques are vastly different for these components and so our perception also needs to be. The article there is making the same mistake that they are criticizing. They criticize studies for only looking at spent fuel, saying that it offers little insight into danger and storage concerns. But then they only focus on mid and low-level waste (i.e. mass) which similarly offers little insight. Complex systems require complex discussions. This is why public conversations like we have on HN and Reddit are less than useless. It is a bunch of armchair experts who have convinced themselves that they understand an extremely complex subject and confidently discuss the issues in naive and inaccurate ways. At the end of the day we live in a specialized world and we have to accept that we need to learn on expert decisions because there is no possible way that we can have (high) expertise knowledge in more than one or two domains. This isn't a jab at your (anyone who is reading) intelligence, but a fact of our world. I don't want to discourage people from learning more about these complex subjects, but I do want to discourage confident discussions when one doesn't have domain expertise. Fruitful conversations can be had if we discuss under this premise but if we don't we just muddle the conversation and there's a good chance we actually decrease our domain knowledge.

petre 3y ago

Yes, the scientists who published it are a previous chairman of the NRC specialized in public policies, two geologists, a director of communications. I'd put more trust in the Union of Concerned Scientists.