Small nuclear reactors: tiny NuScale reactor gets safety approval • Hacker News Board

Re: Small nuclear reactors: tiny NuScale reactor gets safety approval

#151

Post by adrianmonk » Thu, Sep 03, 2020, 8:50 PM UTC

stickfigure wrote: post #111

adrianmonk wrote: post #39

Earlier quoted context omitted.

I'm not an expert, but I'm not convinced about it reducing the need to maintain a nationwide grid. 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 so…

Nukes are slow from a cold start but they can throttle up and down with load. 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.

Wow, that's pretty fast. So 12 minutes worst case. TIL.

Still, I wonder if the economics don't favor running near 100%. You've already paid the high up-front cost of the equipment, and fuel costs are low, so I assume you're better off selling excess power when possible.

Re: Small nuclear reactors: tiny NuScale reactor gets safety approval

#152

Post by godelski » Thu, Sep 03, 2020, 8:50 PM UTC

sandworm101 wrote: post #134

ColanR wrote: post #103

Earlier quoted context omitted.

No expert, but if it's a pool of water then an earthquake might cause a leak?

You don't need to be an expert. Ask anyone who has owned an in-ground pool. Leaks are rare but do happen.

Nuclear power plants were designed with this in mind. It would take a substantially larger earthquake to damage a nuclear power plant and cause it to leak than a commercial pool. Such a comparison is in bad faith and disingenuous.

Re: Small nuclear reactors: tiny NuScale reactor gets safety approval

#153

Post by Retric » Thu, Sep 03, 2020, 8:50 PM UTC

regularfry wrote: post #136

Retric wrote: post #89

Earlier quoted context omitted.

Climate change his hardly an existential threat for humanity. We survived the last ice age with stone tools, this is a less severe change. Economic impacts from things like rising sea levels really depend on how much we spend on maintaining things as they currently are vs adapting to the new normal. Aka do you live below sea level, raise the city, or move somewhere else. https://en.wikipedia.org/wiki/Raising_of_Chica…

There's a very real risk that climate change could knock us back globally to a pre-agricultural level. If that happens, there's almost certainly no coming back: the only way we know how to get to our current level of civilization is by extracting substantially all the easily-extractable energy from the Earth's crust. We only get to do that once. This, today, could well be as good as it ever gets, for the only tree of…

Surface level coal deposits are available across much of the globe, but let’s ignore that.

Agriculture can go a long way with animals, wood, and stone. Extracting energy from wind and rivers is easily attainable from that basis. At which point we would have serious energy to work with. Hydro electric dams provide 6.1% of the total U.S. electricity. That is plenty of energy to kick start industrial manufacturing and get to wide spread solar power.

The next civilization may be extracting most of it’s materials from our cities, but that’s an advantage if anything.

Re: Small nuclear reactors: tiny NuScale reactor gets safety approval

#154

Post by jessaustin » Thu, Sep 03, 2020, 8:51 PM UTC

jabl wrote: post #116

jessaustin wrote: post #94

Earlier quoted context omitted.

This undermines some of the claimed benefits. A bunch of little Fukushima Daiichi reactors in the same location wouldn't have fared any better than the actual Fukushima Daiichi reactor.

In this particular case, a power plant with these nuscale reactors would probably have survived a Fukushima type accident. One effect of being small is that the reactors are designed to be passively cooled after shutdown, using convection instead of pumped flow. So there is no need for emergency diesel generators to keep the coolant pumps running.

Sure, it's safer for reactors to tolerate flooding, if indeed these reactors actually do tolerate flooding. Definitely that would be a better design in flood/tsunami-prone areas. No design (from history, especially no reactor design) is perfect. A set of smaller reactors that were not co-located would be more tolerant of site-specific vulnerabilities in their design.

Re: Small nuclear reactors: tiny NuScale reactor gets safety approval

#155

Post by philwelch » Thu, Sep 03, 2020, 8:53 PM UTC

marshray wrote: post #67

RhodesianHunter wrote: post #58

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This is IMO a positive for nuclear, not a negative. You're forced to confront the cleanup as opposed to fossil fuels, where you just blow your waste out into the atmosphere and make it the commons' problem.

If only a method for permanent disposal of nuclear waste actually existed.

It does. The long-lived wastes can be recycled into fuel in breeder reactors.

Re: Small nuclear reactors: tiny NuScale reactor gets safety approval

#156

Post by theptip » Thu, Sep 03, 2020, 8:53 PM UTC

epistasis wrote: post #92

rubber_duck wrote: post #23

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Thing is this kind of design benefits massively from economies of scale, same kind of thing that has drawn the price of PV down and other green energy.

Up until recently the "economy of scale" meant massive reactors when it came to nuclear, and small modular reactors were abandoned because people didn't think they could be economical. We have radically different construction skill sets now than we did in the 1970s, so the economics may be different now, and it could have been that the planners were wrong before. But I'm any case, until a few of these have shipped, I…

Given the general cost disease affecting large construction projects, I think that massive reactors are an unviable proposition in western countries at this point. While the reactor core designs seem to be templatized, the projects to build them are not, and so there is huge inefficiency. E.g. see https://www.nytimes.com/2017/07/31/climate/nuclear-power-pro....

If NuScale can build hundreds or thousands of these small reactors, they should be able to perfect a turnkey installation playbook that would hopefully reduce costs significantly, and perhaps more importantly, reduce variance on project spend/timelines. I think an unpredictable total cost of ownership is one of the things hurting nuclear projects.

The big question in my mind is whether they can deploy enough of these to get to that scale, given that there's a fairly universal NIMBYism against nuclear power, even where this would be displacing CO2-emitting sources.

Re: Small nuclear reactors: tiny NuScale reactor gets safety approval

#157

Post by ses1984 » Thu, Sep 03, 2020, 8:53 PM UTC

kbenson wrote: post #138

jhallenworld wrote: post #52

Here is the NRC website about this reactor: 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…

Wasn't the big push (or maybe big PR push) for more research and development of Thorium reactors a few years ago because they fail closed/safely? That seems like the kind of thing you'd want for smaller reactors (which I assume means more and more geographically diverse, but don't really know).

There's no research being done on materials to safely contain molten radioactive salt, that research could be dangerous, pretty much only superpowers would have the resources to do the research.

Re: Small nuclear reactors: tiny NuScale reactor gets safety approval

#158

Post by thekyle » Thu, Sep 03, 2020, 8:55 PM UTC

godelski wrote: post #150

newacct583 wrote: post #115

Earlier quoted context omitted.

Or an attack, of course. Or some other event (social unreset, invasion, coup, etc...) causes an evacuation of staff and it boils off during the resulting excursion. People tend to have poor mental models for the long tail of external failures that happen in real life. It's easy to imagine that things that have never happened in the last century would Never Happen. But... they will, somewhere.

Nuclear sites are designed to withstand a strike from a commercial airliner (747). Like you, the designers imagined many of the events you mentioned and more. A good rule of thumb is that if you, a non-expert, can think of a scenario within 10 minutes, an expert has probably already thought of this scenario. Nuclear power plants and weapons sites have always been considered targets and thus considered extra scrutiny…

Wow. How do they design them to withstand a strike from a 747? That seems really difficult.

Re: Small nuclear reactors: tiny NuScale reactor gets safety approval

#159

Post by selectodude » Thu, Sep 03, 2020, 8:58 PM UTC

thekyle wrote: post #158

godelski wrote: post #150

Earlier quoted context omitted.

Nuclear sites are designed to withstand a strike from a commercial airliner (747). Like you, the designers imagined many of the events you mentioned and more. A good rule of thumb is that if you, a non-expert, can think of a scenario within 10 minutes, an expert has probably already thought of this scenario. Nuclear power plants and weapons sites have always been considered targets and thus considered extra scrutiny…

Wow. How do they design them to withstand a strike from a 747? That seems really difficult.

A whole lot of concrete, mostly.

Re: Small nuclear reactors: tiny NuScale reactor gets safety approval

#160

Post by sitharus » Thu, Sep 03, 2020, 8:59 PM UTC

phkahler wrote: post #144

adammunich wrote: post #85

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It's really hard to comprehend just how much heat a reactor can make from decay alone. Like... boiling a hot tub in only a minute.

And so a pool of water is not enough because it will boil away. A continuous flow must be present that can not be interrupted.

You need a sufficiently large reserve to allow the reactor to cool, not an infinite supply. Reactors can be shut down and in this case the pool is sized to absorb all decay heat from the shutdown, plus a significant safety margin.