Small Modular Reactors: Update

 

Some more news on the SMR front:

Proponents of the project say the beauty of the NuScale design is that the reactors can’t melt down, can’t be hacked and the plant does not have to be shut down to be refueled. The reactors are underground and submerged in an 80-foot pool.

“This design is very simple in terms of its contrast to the large reactors,” Hunter said. “The simplicity in this thing made it pass the design certification process quickly, which for UAMPS, was reassuring.”

In December 2017, the Nuclear Regulatory Commission determined NuScale did not need a redundant power source because of its self-cooling features.

“The plant was intentionally designed to be as simple and effective as it possibly could be,” said George W. Griffith, the senior reactor physicist with Idaho National Laboratory. “That determined everything else going on down the line.”

As expected, the naysayers use the same old clichés. One of my favorites is the idea that energy conservation can be used to “produce” more energy. In the business, we call that “negawatts.” The truth is, conservation works to a point, but then you reach a point of diminishing returns governed by the existence of absolute maximum efficiencies.

However, I disagree with using “manmade global climate change” as a driver for the advancement of any source of electricity. Why? You can probably guess . . .

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  1. Bishop Wash Member
    Bishop Wash
    @BishopWash

    Thanks. Interesting read. I got a Solyndra twinge when I read about the government picking companies. Sounds like a great concept though.

    I didn’t understand the concerns about needing a base load. Of course there needs to be a constant source of production. The sun doesn’t always shine and the wind doesn’t always blow, so something always as to be available.

    • #1
  2. Stad Coolidge
    Stad
    @Stad

    Bishop Wash (View Comment):

    Thanks. Interesting read. I got a Solyndra twinge when I read about the government picking companies. Sounds like a great concept though.

    I didn’t understand the concerns about needing a base load. Of course there needs to be a constant source of production. The sun doesn’t always shine and the wind doesn’t always blow, so something always as to be available.

    A base load is a demand that’s always there.  Electricity use varies throughout the day, so a ultility has to plan for an increasing base load in the long run, but enough capacity to handle the variable load day-t0day.  Natural gas has been a boon for power companies in that it’s great for handling the variable load.  However, a power supply that starts up and never stops is perfect for the base.

    • #2
  3. OccupantCDN Coolidge
    OccupantCDN
    @OccupantCDN

    While these reactors are interesting, and I hope they have success, but they’re still a solid fuel reactor – to get truly ground breaking improvements in efficiency and safety, solid fuels will have to be left behind.

    A molten salt reactor, like the molten salt experimental reactor that ran at Oak Ridge national labs from 1965 to 1969 with both U-235 and U-233 fuel loads. U-233 is the most interesting to me personally, because then you can get into the thorium fuel cycle and breed new fuel… Its the closest thing to a perpetual motion machine that nature will allow.

    • #3
  4. OmegaPaladin Moderator
    OmegaPaladin
    @OmegaPaladin

    There is nothing wrong with a solid-fuel reactor design – they work quite well.

    I get that Thorium is the new hotness, but no reason to be exclusive.

    • #4
  5. Henry Racette Member
    Henry Racette
    @HenryRacette

    Love it.

    Just in case American’s don’t rush to embrace the conservationists’ live smaller and meaner approach to energy and life in general, it’s nice to know people are working on sensible alternatives.

    • #5
  6. OccupantCDN Coolidge
    OccupantCDN
    @OccupantCDN

    OmegaPaladin (View Comment):

    There is nothing wrong with a solid-fuel reactor design – they work quite well.

    I get that Thorium is the new hotness, but no reason to be exclusive.

    I hope these reactors get built. Nuclear energy is the only solution for base load utility powers.

    There are several problems that solid fuel reactors simply cant overcome.

    1. solid fuel reactor rods are complex engineered products, thus are expensive and wasteful.
    2. Solid Fuel reactor rods have a limited productive lives, meaning that only 1 – 2% of the useful energy in the fuel is extracted, the other 98% goes into the waste stream. (because of Xenon outgassing – the solid fuel pellets in the rod crack and break down)

    A molten salt reactor has no fuel rod assemblies and as Xenon is produced it can be bubbled out of the fuel solution on an ongoing basis without disrupting the operation of the reactor. Meaning that fuel can be left in the reactor core until their energy is exhausted.

     

    • #6
  7. Stad Coolidge
    Stad
    @Stad

    OccupantCDN (View Comment):
    solid fuel reactor rods are complex engineered products

    All reactors are.

    OccupantCDN (View Comment):
    Solid Fuel reactor rods have a limited productive lives, meaning that only 1 – 2% of the useful energy in the fuel is extracted, the other 98% goes into the waste stream. (because of Xenon outgassing – the solid fuel pellets in the rod crack and break down)

    Reprocessing recovers a bunch of the fuel.  No thanks to Jimmy “nu-cu-lar” Carter for killing it in this country.  Trump should move full throttle with recycling.

    Xenon 135 is an absorber that only precludes startup for a couple of days, and it only affects cores near the end of “core life”.  One of the definitions of “the end of core life” is “xenon precluded startup”.

    Solid fuel is here to stay, and liquid fuel has a nasty habit of being liquid, which means it leaks out of holes.

    Then there is the problem of molten salt, which has an explosice reaction if water touches it.

    I think we need to fully experienment with all types, and pick out the one that works best.  Rickover did for the nuke navy, and the PWR won.  Still, he tried molten salt in the first Seawolf core (liquid sodium).  After a short period of time, the whole plant was replaced with a PWR.  Still, molten salt might work okay for land-based applications . . . let’s try them all.

    • #7
  8. Henry Racette Member
    Henry Racette
    @HenryRacette

    Stad (View Comment):
    Xenon 135 is an absorber that only precludes startup for a couple of days, and it only affects cores near the end of “core life”. One of the definitions of “the end of core life” is “xenon precluded startup”.

    I love when you talk unstable isotopes.

    • #8
  9. OccupantCDN Coolidge
    OccupantCDN
    @OccupantCDN

    Stad (View Comment):

    OccupantCDN (View Comment):
    solid fuel reactor rods are complex engineered products

    All reactors are.

    OccupantCDN (View Comment):
    Solid Fuel reactor rods have a limited productive lives, meaning that only 1 – 2% of the useful energy in the fuel is extracted, the other 98% goes into the waste stream. (because of Xenon outgassing – the solid fuel pellets in the rod crack and break down)

    Reprocessing recovers a bunch of the fuel. No thanks to Jimmy “nu-cu-lar” Carter for killing it in this country. Trump should move full throttle with recycling.

    Xenon 135 is an absorber that only precludes startup for a couple of days, and it only affects cores near the end of “core life”. One of the definitions of “the end of core life” is “xenon precluded startup”.

    Solid fuel is here to stay, and liquid fuel has a nasty habit of being liquid, which means it leaks out of holes.

    Then there is the problem of molten salt, which has an explosice reaction if water touches it.

    I think we need to fully experienment with all types, and pick out the one that works best. Rickover did for the nuke navy, and the PWR won. Still, he tried molten salt in the first Seawolf core (liquid sodium). After a short period of time, the whole plant was replaced with a PWR. Still, molten salt might work okay for land-based applications . . . let’s try them all.

    Reprocessing is nice, but an unnecessary expense if you go with a Molten Salt Reactor.

    Molten salt is not explosive when mixed with water. Molten salts are chemically stable, its not sodium. **

    A liquid will leak through a gap, that just a fact. However the important fact about a Molten Salt Reactor, is that its Molten or very hot – somewhere above 800c – hot. If a fuel salt leaks, it would rapidly cool and crystallizes back into a powder. The problem of a leaky salty reactor is nothing compared to the problems caused by a leaky solid fuel high pressure water reactor.  It would be very simple to design catcher trays under piping to round up any possible leaks.

    Another point – a Molten Salt Reactor can be small – very small – mount on a truck small. The reaction chamber of a 50 MW reactor would be less that 2m in diameter.

     

    ** I meant to say Sulfur here, I had sodium on the brain because of my enthusiasm for salts.

    • #9
  10. OccupantCDN Coolidge
    OccupantCDN
    @OccupantCDN

    There is a reactor design called SSTAR (Small Sealed Transportable Autonomous Reactor) its a sealed reactor vessel 15mx3m produces 100 Mw and weighs in at about 500 tonnes. Has a fuel load for 25-30 years.

    • #10
  11. Stad Coolidge
    Stad
    @Stad

    Henry Racette (View Comment):

    Stad (View Comment):
    Xenon 135 is an absorber that only precludes startup for a couple of days, and it only affects cores near the end of “core life”. One of the definitions of “the end of core life” is “xenon precluded startup”.

    I love when you talk unstable isotopes.

    Cocktails later?  Pick me up at . . . say, seven?  I’ll talk transuranic to you.

    Hehe . . .

    • #11
  12. Stad Coolidge
    Stad
    @Stad

    OccupantCDN (View Comment):

    Stad (View Comment):

    OccupantCDN (View Comment):
    solid fuel reactor rods are complex engineered products

    All reactors are.

    OccupantCDN (View Comment):
    Solid Fuel reactor rods have a limited productive lives, meaning that only 1 – 2% of the useful energy in the fuel is extracted, the other 98% goes into the waste stream. (because of Xenon outgassing – the solid fuel pellets in the rod crack and break down)

    Reprocessing recovers a bunch of the fuel. No thanks to Jimmy “nu-cu-lar” Carter for killing it in this country. Trump should move full throttle with recycling.

    Xenon 135 is an absorber that only precludes startup for a couple of days, and it only affects cores near the end of “core life”. One of the definitions of “the end of core life” is “xenon precluded startup”.

    Solid fuel is here to stay, and liquid fuel has a nasty habit of being liquid, which means it leaks out of holes.

    Then there is the problem of molten salt, which has an explosice reaction if water touches it.

    I think we need to fully experienment with all types, and pick out the one that works best. Rickover did for the nuke navy, and the PWR won. Still, he tried molten salt in the first Seawolf core (liquid sodium). After a short period of time, the whole plant was replaced with a PWR. Still, molten salt might work okay for land-based applications . . . let’s try them all.

    Reprocessing is nice, but an unnecessary expense if you go with a Molten Salt Reactor.

    Molten salt is not explosive when mixed with water. Molten salts are chemically stable, its not sodium.

    A liquid will leak through a gap, that just a fact. However the important fact about a Molten Salt Reactor, is that its Molten or very hot – somewhere above 800c – hot. If a fuel salt leaks, it would rapidly cool and crystallizes back into a powder. The problem of a leaky salty reactor is nothing compared to the problems caused by a leaky solid fuel high pressure water reactor. It would be very simple to design catcher trays under piping to round up any possible leaks.

    Another point – a Molten Salt Reactor can be small – very small – mount on a truck small. The reaction chamber of a 50 MW reactor would be less that 2m in diameter.

    I’d like to see more development of the gas-cooled reactor.  The thought of having air as an emergency heat sink appeals to me . . .

    • #12
  13. Ontheleftcoast Inactive
    Ontheleftcoast
    @Ontheleftcoast

    I seem to remember that about 20 years ago Bonneville Power was touting the eco-friendly idea of small reactors with something like a 30 year useful life being helicoptered in to remote building sites (private homes or public facilities) in the wilderness because it would be cheaper and have less impact on the terrain than running power lines.

    Probably work better in the winter in the woods than solar, too.

    • #13
  14. Jim McConnell Member
    Jim McConnell
    @JimMcConnell

    A person could learn a lot on this site. Unfortunately, we laymen (persons) need to learn the language first.

    Reading this conversation, I feel like I’m back in school.

    • #14
  15. OccupantCDN Coolidge
    OccupantCDN
    @OccupantCDN

    Jim McConnell (View Comment):

    A person could learn a lot on this site. Unfortunately, we laymen (persons) need to learn the language first.

    Reading this conversation, I feel like I’m back in school.

    Nerds be nerding.

     

    • #15
  16. OccupantCDN Coolidge
    OccupantCDN
    @OccupantCDN

    Ontheleftcoast (View Comment):

    I seem to remember that about 20 years ago Bonneville Power was touting the eco-friendly idea of small reactors with something like a 30 year useful life being helicoptered in to remote building sites (private homes or public facilities) in the wilderness because it would be cheaper and have less impact on the terrain than running power lines.

    Probably work better in the winter in the woods than solar, too.

    Actually the better use for these kind of small reactors would be military.

    Forward operation bases like in Afghanistan have to be resupplied by trucks. This leaves a supply chain vulnerable to attack, a small reactor deployed at the base would dramatically reduce fuel consumption and thus reduce the need for supply missions across contested territory.

    A dramatic example of how nuclear energy could save lives.

    • #16
  17. Stad Coolidge
    Stad
    @Stad

    OccupantCDN (View Comment):
    Actually the better use for these kind of small reactors would be military.

    I”m thinking they’d be great in submarines!  But seriously, submarine reactors have a lot going for them – simple to operate, easy to maintain (even some teenagers can do maintenance!)  However, they are designed to be load-following (answer bells), so the trade-off is efficiency and base-load support for simplicity and rapid power changes.

    One guy I worked with back in the mid-90s worked on the nuclear airplane project.  He had some great stories about what he did way back then, and the test facility where he worked.

    • #17
  18. The Reticulator Member
    The Reticulator
    @TheReticulator

    OccupantCDN (View Comment):

    Ontheleftcoast (View Comment):

    I seem to remember that about 20 years ago Bonneville Power was touting the eco-friendly idea of small reactors with something like a 30 year useful life being helicoptered in to remote building sites (private homes or public facilities) in the wilderness because it would be cheaper and have less impact on the terrain than running power lines.

    Probably work better in the winter in the woods than solar, too.

    Actually the better use for these kind of small reactors would be military.

    Forward operation bases like in Afghanistan have to be resupplied by trucks. This leaves a supply chain vulnerable to attack, a small reactor deployed at the base would dramatically reduce fuel consumption and thus reduce the need for supply missions across contested territory.

    A dramatic example of how nuclear energy could save lives.

    What would be the consequences of their falling into enemy hands?  Would there be a secret back door to make them go boom? 

    • #18
  19. OccupantCDN Coolidge
    OccupantCDN
    @OccupantCDN

    Stad (View Comment):

    OccupantCDN (View Comment):
    Actually the better use for these kind of small reactors would be military.

    I”m thinking they’d be great in submarines! But seriously, submarine reactors have a lot going for them – simple to operate, easy to maintain (even some teenagers can do maintenance!) However, they are designed to be load-following (answer bells), so the trade-off is efficiency and base-load support for simplicity and rapid power changes.

    One guy I worked with back in the mid-90s worked on the nuclear airplane project. He had some great stories about what he did way back then, and the test facility where he worked.

    Yes a nuclear navy or even a nuclear merchant marine would be fantastic. However a naval reactor is far too large to be lifted by a helicopter.

    A small reactor (type D2G) has an output of 148 – 165 Mw (Thermal) and although I couldn’t find a weight for these reactors. From what Ive read about the SSTAR reactor, it would have to be far too heavy to be air lifted into a remote location.

    • #19
  20. Ontheleftcoast Inactive
    Ontheleftcoast
    @Ontheleftcoast

    OccupantCDN (View Comment):

    There is a reactor design called SSTAR (Small Sealed Transportable Autonomous Reactor) its a sealed reactor vessel 15mx3m produces 100 Mw and weighs in at about 500 tonnes. Has a fuel load for 25-30 years.

    Here’s a Japanese design with a 10 year life that weighs under 8 tons.

    Only 200 KW, though.

    The RAPID-L is a thermoelectric power conversion system using uranium-nitride fuel (40% and 50% enriched respectively) and liquid lithium-6 coolant with a 5 MW of thermal energy and 200 kW of electric power. The lithium inlet and outlet are rated for a temperature of 1,030 and 1,100 °C. Lithium-6 also serves as neutron absorber. It is the first reactor of this kind. As lithium-6 has not been used as a neutron absorbing material in conventional fast reactors, measurements were performed at the Fast Critical Assembly (FCA) of Japan Atomic Energy Research Institute (JAERI). The FCA core was composed of highly enriched uranium and stainless steel samples so as to simulate the core spectrum of the RAPID-L. The samples were enriched with 95% lithium-6 and were inserted into the core parallel to the core axis for the measurement of the reactivity at each position. It was found that the measured reactivity in the core region was in agreement with calculations. Bias factors for the core design were obtained by comparing between experimental and calculated results. [3] [5] [6]

    The reactor has basically a loop type configuration and a reactor container of 2 m in diameter, 6.5 m deep and weighs about 7.6 tons. This RAPID concept has neither diagrid nor core support structure since they are integrated in a fuel cartridge. The simple reactor container would make the most important In-Service Inspection (ISI) easier. An ISI can be conducted for each refueling. The reactor is designed to be installed below grade so that the ground provides the necessary shielding. Separate electromagnetic pumps and the fuel cartridge are connected by the connecting tubes. The reactor subsystem is characterized by the RAPID refueling concept to eliminate conventional fuel handling systems. This gives a substantial reactor block mass savings of 60% over comparable liquid metal cooled fast reactor systems. [3] [6]

    • #20
  21. OccupantCDN Coolidge
    OccupantCDN
    @OccupantCDN

    The Reticulator (View Comment):

    OccupantCDN (View Comment):

    Ontheleftcoast (View Comment):

    I seem to remember that about 20 years ago Bonneville Power was touting the eco-friendly idea of small reactors with something like a 30 year useful life being helicoptered in to remote building sites (private homes or public facilities) in the wilderness because it would be cheaper and have less impact on the terrain than running power lines.

    Probably work better in the winter in the woods than solar, too.

    Actually the better use for these kind of small reactors would be military.

    Forward operation bases like in Afghanistan have to be resupplied by trucks. This leaves a supply chain vulnerable to attack, a small reactor deployed at the base would dramatically reduce fuel consumption and thus reduce the need for supply missions across contested territory.

    A dramatic example of how nuclear energy could save lives.

    What would be the consequences of their falling into enemy hands? Would there be a secret back door to make them go boom?

    You could have a poison pill of U-238 that would denature the fuel load of the reactor and render it instantly ‘safe’. Thorium fuel cycle reactors did not get selected in the early 1950s for development because of they did not produce useful isotopes for weapons.

    MSR (or LFTR) reactors dont go boom – because they operate at high temperatures but low pressure. There is no water in the anywhere in the cooling system – so that there can’t be a Fukushima or Chernobyl style failure that causes reactor pressure vessels to rupture.

    https://en.wikipedia.org/wiki/Molten_salt_reactor

    https://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reactor

    My favorite solution for small reactors is a single fluid LFTR design with a brayton cycle cooling system. Light weight and not dependent on large bodies of water for cooling – could provide energy anywhere.

    • #21
  22. Mendel Inactive
    Mendel
    @Mendel

    Since we’re talking small reactors with a former (?) submariner:

    What’s the deal with NR-1? Isn’t that also a miniaturized reactor that requires very little manpower? Is it simply a scaled-down version of a typical naval PWR reactor, or does it also use some alternative technology?

    • #22
  23. Chuckles Coolidge
    Chuckles
    @Chuckles

    Decades ago I worked with a fellow that had just previously been assigned to some station (Navy?) in Antartica.  He operated a small, portable, self-contained nuclear power plant.  What was that?  He described it as being very small and very portable and like he was just there.

    • #23
  24. Chuckles Coolidge
    Chuckles
    @Chuckles

    This quote from the referenced article is one that drives me wild:

    “Yucca Mountain in Nevada was the planned depository for the storage of high level nuclear waste, but President Obama scuttled the project by yanking the funding after two decades of research.”

    Sorry, but there is so much wrong in that statement.  

    • #24
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