https://www.nrc.gov/reactors/new-reactors/smr/nuscale.html
Here is an interesting sub-report:
https://www.nrc.gov/docs/ML2022/ML20224A525.pdf
Information withheld for security reasons. One item concerns the "ultimate heat sink". What happens when the ultimate heat sink is lost?
Well a design assumption is that it is not lost:
https://www.nrc.gov/docs/ML2020/ML20205L410.pdf
"A key assumption of the PRA is the availability of the UHS to provide an adequate heat sink. To support passive heat removal with the DHRS or ECCS, the reactor modules are housed and partially submerged in the UHS such that most of the outer surface of the CNV directly contacts the UHS, which is a large pool of water in the reactor building (RXB). "
DHRC is decay heat. CNV is reactor containment vessel. So drain the pool and the reactor is in trouble.
- The reactor differs substantially from existing PWRs by encasing the primary in double containment, using natural circulation flow for both normal operation and emergency cooling. There are no pumps needed (or installed) to move coolant through the reactor.
- During normal operation, the primary is entirely contained within the primary containment, and circulates naturally, using the differential temperature and gravity. The steam system can is used to remove heat.
- During an emergency, valves open to admit the reactor coolant into the backup containment. These valves are normally held shut by hydraulics with positive control from electronics-- their failure mode is to open with no other operator action in case of a loss of power. No additional operator action is needed to initiate the emergency cooling flow, which is also a natural circulation loop to the backup containment shell, which then conducts heat to the pool.
- The backup containment shell is designed to withstand hydrogen explosions such as those that occurred at Fukushima, and which was possibly prevented at Three Mile Island by venting (whether there was a hydrogen explosion at TMI-2 is not fully understood).
- There is no mechanism for positive reactivity addition via graphite moderator rod such as in the Chernobyl design. The specific failure mode at Chernobyl is not possible with this reactor.
- The pool is specified as a stainless-steel-lined reinforced concrete and designed to withstand earthquakes. The safety systems are such that no reactor electricity supply is needed to remove heat-- the pool could be filled e.g. from a fire truck, and the immediate decay heat from shutdown does not require any additional heat removal or water addition. So the failure mode we saw at Fukushima (inability to remove decay heat due to loss of electricity) and hydrogen explosion breaching containment does not apply to this design.
If it's using gravity, what happens if this whole reactor gets tilted? What happens at 10 degrees? 45? 90? 180? Are there any critical angles where it would melt down?
I'm curious how you would make such a design that would be both using gravity yet tolerate being moved around.
Basically: What's so dramatically difficult about doing the same for a terrestrial compact reactor to make something like the NuScale take so long to get approval?
https://www.neimagazine.com/features/featurethe-world-s-larg...
Anyway, what if the valves to the backup containment open while it's running at full power? I mean the electronics fail so the valves open. I suppose the steam generator is still running, but even so lots of heat would be dumped into the pool. Maybe there is an interlock so that the reactor scrams in this case.
In some reactor designs overheating slows and eventually stops the reaction in a controlled/deliberate manner. The reactor system may still fail irreversibly, but it wouldn't necessarily meltdown in a way that risks widespread contamination or excessively expensive site remediation, such as by exposing unapproachable material.
I have no idea if this design has that quality.
What's an example event where the ultimate heat sink might be lost?
As I understand it, the pool has no drain. There's nowhere the water can go. Which would make sense for a passive safety feature.
The reactor ceases to transmit power and is shutdown for maintenance?
That said, rapidly losing the UHS should be incredibly rare/difficult (as several other posters have mentioned).
"DOE reported that it faced an estimated $494 billion in future environmental cleanup costs — a liability that roughly tripled during the previous 20 years."
There is no plan for this stuff. The repository that was built in Nevada was never actually approved and it is not legal to use. So everyone that was planning on sending stuff there has just been piling it in the side yard waiting for something. New Mexico is now trying to open up a waste site.
But if you operate a reactor in Tennessee, right now you have no idea where to store the waste so you just keep piling it higher and deeper on site.
Source: rumour and gossip
Or just use wind and solar?
List of sites https://www.dnfsb.gov/doe-sites
https://www.gao.gov/key_issues/disposal_of_highlevel_nuclear...
This is a roadblock put up against nuclear power plants alone.
The waste majority of those cost are not because of civilian nuclear reactor, but rather creation of nuclear weapons.
Site cleanup cost are a factor, but not a huge one considering a site can be active for 60-100 years.
Or were you just planning to let the grandkids deal with that?
If reactors, or the placement of them, are designed to be left in-situ after decommissioning, then the cost becomes a lot less. Moving spent fuel from one site to another makes little sense when the original site has already been designated nuclear.
As others have said, this kind of number is always pitched at nuclear, and not hydro, or coal, or any other form of power.
Seems like we should be running those just for those.
Nuclear reactors take ages to ramp up and down. It's basically going to be generating the same amount of power 24x7, but demand is going to fluctuate. The more other areas you're connected to, the more opportunity there is to send that power to someone who can use it.
Obviously there's a law of diminishing returns at some point, so maybe the grid doesn't need to be as large as possible.
There are alternatives like energy storage (batteries, etc.), but you'd have to compare all the costs and benefits.
https://en.wikipedia.org/wiki/Load_following_power_plant#Nuc...
Modern nuclear plants with light water reactors are designed to have maneuvering capabilities in the 30-100% range with 5%/minute slope.
Naval reactors are apparently very fast in this regard, so it's evidently not an inherent property of nuclear power.
(The USN also has an unparalleled record of safely operating reactors; more that 5,000 reactor-years clocked without major incident.)
Run them at full blast and dump the extra energy into direct air carbon capture? Of course that would require building the CC plants but it could be planned for.
solar can do the same sort of thing.
No, they aren't. They are more expensive per unit of power produced, by far bigger than any other powerplant in practical use.
The only way I see nuclear getting economical is it getting bigger. Nuclear's biggest advantage after the cost of fuel is its huuuuuuge power density, and power scalability. With currently technology level, it's possible to generate multiple gigawatts from a single reactor.
> it dramatically reduces the need to maintain a massive nationwide grid
It would not. Grid maintenance are quite non-linear, and high voltage lines are actually much cheaper per unit of electricity transferred than residential links.
Very high voltage DC transfer is very economical, efficient enough for intercontinental connections, but very expensive.
Mass production is a no-brainer.
Congrats to NuScale for making it through to the other side of US nuclear regulatory purgatory. Optimism is warranted ("all of the above" to replace fossil fuels), but cautious optimism. It's not real until a commercial reactor is generating. Vogtle is still not done [4]. I hope I get to see a factory churning out prefab reactors ready for shipment.
EDITs (to not pollute thread with replies): A carbon tax in the US is very unlikely, and you cannot count on economies of scale until you have arrived at scale.
[1] https://www.lazard.com/perspective/lcoe2019
[2] https://www.nuscalepower.com/benefits/cost-competitive
For example, right now we have a pretty serious externality with CO2 for coal and other sources, what are the costs that folks would assign to CO2 to clear to needed target? That could bring comparative cost (with CO2 impact) down a bit.
Experience to date has been the opposite. They have diseconomies of scale in construction and operation. The proponents claim they will make up for this somehow, for example by making the reactors in factories, but note that NuScale has given up on that and is going to have the parts fabricated by others and assembled on site, just like larger reactors.
https://www.oregon.gov/energy/facilities-safety/facilities/P...
https://www.corvallisadvocate.com/2012/got-nuke-state-of-the...
So startups have to essentially go from nothing to first commercial reactor in one step, without iteration.
Back when I worked at my alma mater, I could see the reactor building across the yard from the coffee room. Still waiting for that third eye to start growing out of my forehead.
https://nuclear.engr.utexas.edu/netl/triga-reactor
BUT... it also has two 74-megawatt gas turbines that supply the campus with electricity and steam:
https://utilities.utexas.edu/chp/about-carl-j-eckhardt-combi...
"In the event of any runaway reactor event, NuScale says, the reactor quenches itself in its pool, making it “passively safe.”"
Everything is 'safe' until we discover it isn't and improve. Many things have improved over times. Calling them safe seems fine, we can do so understanding the process of learning and advancing.
> Three Mile Island
Was handled reasonably well, resulted in safety improvements to procedures and designs for future reactors.
From https://www.nrc.gov/reading-rm/doc-collections/fact-sheets/3...
> The approximately 2 million people around TMI-2 during the accident are estimated to have received an average radiation dose of only about 1 millirem above the usual background dose. To put this into context, exposure from a chest X-ray is about 6 millirem and the area's natural radioactive background dose is about 100-125 millirem per year for the area. The accident's maximum dose to a person at the site boundary would have been less than 100 millirem above background.
Not exactly the end of the world.
> Chernobyl
Accident caused by Communists who did not care about what happened to Ukrainians, as usual for them, and experimented with something that any nuclear physicist could have told them was a terrible idea. This is like blaming vehicles and calling them unsafe after reaching over from the passenger seat and yanking the wheel to drive a truck into a crowd. The moral of the story here is to keep Communists away from anything important, which applies to farms, industrial sectors, food distribution, and really most things more complicated than a pitchfork or a torch.
> Fukushima
Was reasonably safe for its long life, but they cheaped out on the necessary wall and drainage functionality; should probably have been decomm'd and replaced before this happened.
The problem in the nuclear industry is that anti-nuclear people like you form public opinion that causes it to be difficult for it to move forward. New plants based on newer designs are orders of magnitude safer - e.g. the CANDU Canadian reactor which is more fail-safe than most, and the push towards 4th generation reactors.
Get out of the way and let the planet have a clean base load energy source, or be sitting here bitching about carbon footprints 50 years from now when it should be a solved problem already.
>Was reasonably safe for its long life, but they cheaped out on the necessary wall and drainage functionality
They didn't "cheap out" on the seawall at Fukushima. You may be referring to how the plant design was sited closer to the ocean but the seawall was constructed to not be overtopped by the highest tsunami possible. At the time the plant was constructed the theory was that tsunamis were generated in part by underwater landslides and the topology of the surrounding ocean was taken into account to come up with the largest possible tsunami it would have to block. The science behind tsunami formation was flawed during construction and once that theory was later improved no one ever reconsidered the implications for the seawall design.
I agree that public perception is the largest problem by far with nuclear energy but you're not helping your argument by brushing real problems under the rug like this.
https://inis.iaea.org/collection/NCLCollectionStore/_Public/...
But keep in mind that the NRX reactor it was based on had an accident:
https://www.cns-snc.ca/media/history/nrx.html
(famously, Jimmy Carter was part of the NRX clean-up crew).
What happens if the passive cooling pool drains? Let me guess, “That will never happen!”
https://en.m.wikipedia.org/wiki/Price–Anderson_Nuclear_Indus...
They didn't really care what happened to _anybody_, not just Ukrainians. Ukrainians (as well as about 30% of Russians) just happened to live in that particular location. The plume made it all the way to the Nordics and Germany, and I, as a kid, had to take iodine tablets in Russia, even though officially everything was "under control" for a few days. Then the narrative shifted to showing the heroism of the "liquidators", never fully acknowledging how dangerous any of this really was.
There were many such RBMK reactors spread all over the Soviet world that had the same flaws . There are many problems with your summary so can I just recommend that you watch the HBO mini series "Chernobyl" instead? It's a great watch.
Per: https://www.nuscalepower.com/technology/technology-overview
We'll see of this is in any way or form sustainable, especially since uranium is also a finite ressource.
Compare that to a nuclear plant near me which has two reactors that each generate 1280 megawatts.
So it would take about 25 of these to equal the power output of a traditional nuclear reactor.
The NuScale design also uses LEU and a plant is comprised of up to 12 of these modules sitting in water pools. You can view it as a battery pack where batteris are continously rotated as they are refuelled.
Yes, it gains you some of the economics of factory construction and that you can start small and scale a location, but on the other side you lose that again because you lose the economics of scale that traditional PWR gets.
I really believe we should be a nuclear society by now, and that regulations both around reactors and fuel availability prevented this from happening. In the 1960 lots and lots of innovative reactors were build, often with relatively low budgets at that. The amount of untapped potential in nuclear energy is incredible. We don't need fusion, fission is plenty energy dense, if we can't figure out how to make fission practical, we want with fusion either.
Yet here we are in the year 2020 and we are still building new PWR reactors. But the reality is, in the US it is essentially impossible to build anything else. Regulations are designed so that the only reactor that can really get approval is a PWR.
If you attempt to build anything new, you have to basically pay the government to study your design and after a unknown amount of time and money, the government might develop a new regulatory framework. By the time that happens of course you have run out of money already, no buissness plan that depends on the government figuring out how to regulate a new type of reactor would ever really happen.
The good thing at least is that the DoE in the last 5 years seem to have realized that their whole approach was a problem and they have done a lot of good things to try to change. Outside of the US the energy sector is government controlled or to small for a nuclear reactor startup to have a large enough market to make a new reactor worth it.
Canada has established itself as basically the only viable place for new reactor development, with Terrestrial Energy and Moltex Energy (moved from Britain to Canada because regulation).
So, good luck to NuScale, I hope they can prove me wrong and deploy many of these in an economical way.
You mean they lose operational efficiency ? Economies of scale come from the ability to mass produce.
You forgot to mention the largest differentiator - eliminates the possibility of a global catastrophe.
[1] http://www.oecd-nea.org/ndd/pubs/2020/7530-reducing-cost-nuc...
[2] https://whatisnuclear.com/economics.html#improving-modern-nu...
Historically, one of the few successful ways to lower the price per generated power from a nuclear power plant has been to make the reactor larger. So yeah, there's a reason why the latest traditional PWR designs such as the French EPR are huge (1600 MWe).
The gamble with these small reactors like Nuscale is that series production of the reactors in a factory would make up for the loss of the traditional economy of scale due to size. It remains to be seen how well that will work out.
From AP1000 wikipedia:
> The design traces its history to the System 80 design, which was produced in various locations around the world. Further development of the System 80 initially led to the AP600 concept, with a smaller 600 to 700 MWe output, but this saw limited interest. In order to compete with other designs that were scaling up in size in order to improve capital costs, the design re-emerged as the AP1000 and found a number of design wins at this larger size.
So modern PWR are usually build with 1GWe one location one reactor, huge economics of scale in terms of the size of the power plant. A AP1000 is not much bigger then an AP600.
> You forgot to mention the largest differentiator - eliminates the possibility of a global catastrophe.
I disagree. First of all, I think the possibility of a global catastrophe with a traditional PWR are already incredibly small, and when talking a modern build like an AP1000 the NuScale doesn't have that much better safety characteristics.
PWR are inherently problematic and require tons and tons of complex engineering to make them save and the error potential in such a solution are always there.
The problem of course is that takes a large government to mandate a huge public project, which is not really likely these days. The advantage of these small reactors for now is that they hopefully prevent expensive,bloated, one-off site designs that go over budget and miss their schedules.
They have given up on that, I read.
Do not submit to the fallacy of nuclear waste disposal. First Elon needs to fix space travel and make transport into the sun feasible. And we will have iter by then.
Could you just make an off-shore in-ocean "farm" of these?
Legit use for Project Plowshare harbors?
Not! Ocean is inherently unstable!.
The first serious storm would dislodge and damage the whole farm crashing one module against the other before to vomit them in the shore. Some modules just would dissapear.
And then you have a humongous environmental damage and a really expensive rescue problem trying to clean the fragmented mess.
Mutual impact issue sounds pretty resolvable with a big steel frame and the like.
But hey, I'm sure, this time, it will be different. 100%.
However, these are lessons learned. Today it's quite hard to come up with a reactor design without many safeguards and passive safety features, like it's quite hard to come up with a car with no seatbelts or airbags.
Is generating electricity directly from the products of fission proven [mathematically] to be less efficient than
decay->steam->mechanical->electrical
or is just that the applied science of steam power is so far ahead of everything else?
My peace of mind would be much greater if the energy transfer went through solid state systems instead of a working fluid that is pretty good at carrying the bad products of a [malfunctioning] reactor.
So you throw water (or salt) on the reactor, heat it up, and do work with the steam that is ultimately produced.
It has less to do with steam being the ideal route and more to do the the practicality of dealing with heat.
AFAIK, most reactors are closed loops anyways, so there's not much of an issue with water carrying away radioactive materials.
But that’s good info, thanks. Molten salt still has to heat transfer to steam because we don’t have any thermovoltaics in the 50% efficient range.
I think I now understand that most of the heat comes from absorbing neutrons, which don’t like to generate electricity (vs betavoltaics and gammavoltaics). And any device inside the pressure vessel would be altered by those neutrons, need to be accounted for as another source of decaying particles, and need to be replaced.
And/Or, you’d want a completely different reaction and then need a neutron generator capable of running continuously.
That about right?
I was going to say coincidence but this was clearly Google doing creepy stalker things after it saw what else I was searching for on the Internet (even not using google.com) This popped into recommendations an hour after you asked:
https://www.oecd-nea.org/nea-news/2011/29-2/nea-news-29-2-lo...
I kid! AFAIK you most want this kind of immense baselines power for heavy industrial activities.
Also AFAIK, if these are simple/easy/small enough, you could co-locate the heavy consumption with the generation which'd cut power consumption (due to transmission) by something like 30% (on top of infrastructure maintenance savings). Kinda like Netflix putting boxes in local switches (if I have those terms correct).
It's not that this is smaller. It's comparable to Shippingport or Vallecitos. The argument is that it's safe enough against meltdowns not to need a full containment vessel, which makes it cheaper. The idea is to have a group of these sharing the same reactor pool. What they do if there's a leak into the cooling pool. Does that take down all the reactors?
Anyway, the plan is to build the first one at the Idaho Reactor Test Station, 830 square miles with reactors spread miles apart. If something bad happens there, it's not a major problem.
Well, unless you're in Idaho like some of us. ;-)
Older reactors are designed like fortresses, supposedly able to take a direct hit by a commercial jet and survive. They have armed guards, etc.
It would be interesting to see how they would try to protect these. Typical electrical substations are protected by a chain-link fence and a padlock.
So the end result would be a powerplant that produces about as much power as a "normal" nuclear power plant, just that it contains many small reactors instead of a few big ones.
On the contrary, you gain economies of scale. The way the economies of scale work is if you build n identical widgets, it costs you less than n times the cost of building one single widgets. In other words the unit cost of a widget goes down as the number of produced widgets increases.
If you want to produce a bigger widget though, you generally have diseconomies of scale. For example the Saturn V rocket was about 20 times bigger than the Titan 2 rocket (from which it was derived) but cost about 60 times more.
So, if a Gigawatt-size nuclear power plant is too expensive to build, you build 20 plants of 50 MW each. This is how you achieve economies of scale.
I'm not sure if the goals for this project are the same, or if the goal of a low-maintenance reactor are even possible, but it sounded pretty cool.
Since that story didn't get much attention (relative to the interest in it), we won't call the current thread a dupe.
So what happens when an earthquake causes a rupture of the pool barrier and all the water leaks out?
https://en.wikipedia.org/wiki/Earthquake-resistant_structure...
small? how small is small?
Tiny? how tiny is tiny?
A regional power company might seek permitting at 10-20 locations. If some locations didn't get a permit or if other locations proved to be uneconomical to produce power at the time of construction, they could just build at the sites they chose. Basically takes the two phase pre-construction permitting and post-construction operating permit which has been killing nuclear power and streamlines it. Because the designs are standard and modular they will be pre-approved to operate.
As a California resident, I would like the option to run A/C after sunset.
It is fascinating, for example, how a slight change in the packaging of the fuel (as sand-sized pellets coated with carbon) affects the safety/stability of the design, and how resonances in the cross section for neutron absorption come into play (they broaden at higher temperatures, dampening rather than enhancing the overall reaction speed, as temperatures rise).
I'm very impressed by that output. It will make a difference with areas of high solar and wind generation, which can't maintain a sustained high duty cycle.
I expect these types of reactors to be in places to augment solar and wind, not replace it.
Surely they would have a much easier time selling things like that elsewhere? Growing nations would probably love reliable power that could be plonked down off a ship and added to incrementally.
I understand they've given up on making that part themselves in a factory of their own, btw.
How long does one "charge" last?
What is the price of unit and per kWh?
What is the maintenance procedure?
How long is the life?
What after expiry?
Can we use Thorium for now?
