Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Small nuclear reactors: tiny NuScale reactor gets safety approval

popularmechanics.com

Post reply on HN
Print view View original

321–330 of 554 posts

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

#321

Post by neltnerb »

ses1984 wrote: post #157
kbenson wrote: post #138

Earlier quoted context omitted.

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.

Really? I literally read dozens of papers about it a decade ago, at least... I guess I don't work adjacent to there so maybe no one else does either. Odd, I never have heard a reason why they were all that much worse than alternatives other than for corrosion and licensing costs, I am surprised that such a well defined problem just stopped being studied.

I suppose at some point it's not competitive with solar so what's the point. Maybe we reached that threshold recently.

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

#322

Post by URSpider94 »

wahern wrote: post #312
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…

> DHRC is decay heat. CNV is reactor containment vessel. So drain the pool and the reactor is in trouble. 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 unapproach…

I haven't had time to read all of the info, but I get the impression that this is still a pressurized water reactor, just on a smaller scale. It will fail in pretty much the same way as current reactors like Fukushima and Chernobyl. I believe that the point is that the pool provides an extra level of failsafe against coolant loss, and additionally that the substantially smaller size of the core limits the amount of heat build-up in a meltdown.

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

#323

Post by kryogen1c »

ansible wrote: post #228
kbenson wrote: post #138

Earlier quoted context omitted.

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).

Yes. Molten Salt Reactors (MSR), while operating very hot, are not operating under a lot of pressure. A pressurized water reactor (PWR) does , and if there is a leak or other problem, it can turn into an explosion.

you are confusing two different characteristics of reactor design.

one is whether or not the coolant is highly pressurised relative to atmosphere, the other is what the thread was originally about, which is how reactivity changes with respect to temperature. this is the temperature coefficient of reactivity.

https://www.nrc.gov/reading-rm/basic-ref/glossary/moderator-...

the people you were responding to were referring to the latter. specifically, if a reactor becoming more reactive results in more or less total reactivity. this characteristic is related to, but independent of, how pressurized the coolant and/or moderator are.

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

#324

Post by URSpider94 »

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…

Yes. This is not an inherently safe design. However, it adds a second level of safety, in that each reactor has its own coolant loop that would have to fail first, followed by a second failure of the large pool. It looks like the large pool is also passive, in that it does not rely on circulator pumps to provide cooling.

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

#325

Post by jacobwilliamroy »

bluejellybean wrote: post #306
jacobwilliamroy wrote: post #274

Earlier quoted context omitted.

So we can just put it all in your house and you'll be cool with that? After all, there are more dangerous things out there, and we won't be putting any of those in your house, so that makes it okay right?

Absolutely, why not? As long as the waste dealer is offering a deal that is satisfactory for me as the landowner/waste site, I would happily store said waste. Your question is a bit absurd; nobody is suggesting to keep it inside of someone's home. Should an individual not be allowed to make rational decisions about their land and property? If I owned 20 square miles in the desert, why shouldn't I be allowed to lease…

In my personal philosophy, as a landowner you are responsible not only for yourself and your neighbors, but also for the next 7 generations of people who will be using that space after you. So to me, no you have no right. But that's just my own opinion.

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

#326

Post by URSpider94 »

deegles wrote: post #146
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…

> Nuclear reactors take ages to ramp up and down. 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.

That's the whole point of creating grid-scale storage - giant batteries, lots of smaller batteries, pumped storage, pressurized air storage, traction railways, etc - or smarten up loads like EV charging so they can ramp up/down to soften the fluctuations in demand from other sources.

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

#327

Post by pdonis »

pvaldes wrote: post #272
pdonis wrote: post #251

Earlier quoted context omitted.

Leak to where? It's below grade and it's not under any pressure greater than atmospheric.

The elephants foot in Chernobyl was so hot that melted the concrete and dug into the soil. Is this pool bottom impossible to melt?

Chernobyl is not a good comparison, because that reactor design had a number of flaws that nobody in their right mind would have designed into it even then, let alone now. (The Soviet Union was not in its right mind.) And then on top of that, the operators were running an experiment with the reactor without having thought through the consequences.

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

#328

Post by natmaka »

garmaine wrote: post #212
marshray wrote: post #67

Earlier quoted context omitted.

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

It does. It’s called a breeder reactor.

Breeder reactors research was quite huge (one of the first breeder was built in the US in 1951).

Then this technology has been, for all practical purposes, abandoned by nearly all countries that were researching and developing it. See https://en.wikipedia.org/wiki/Breeder_reactor#Future_plants

One of the most (if not the most) ambitious project was Superphénix, costed billions and failed flat. https://en.wikipedia.org/wiki/Superph%C3%A9nix

The sole officially actively pursued pertinent design, BREST-OD-300 ( https://en.wikipedia.org/wiki/BREST_(reactor) ), was planned to be built in 2020 ( https://www.world-nuclear-news.org/NN_Fast_moves_for_nuclear... ) and real work didn't even began ( https://www.world-nuclear-news.org/Articles/Russia-awards-co... ). Moreover it will only (when built, if ever, but not before 2026) be a demonstrator (low power).

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

#329

Post by dheera »

patmorgan23 wrote: post #313
dheera wrote: post #271

Earlier quoted context omitted.

> materials to safely contain molten radioactive salt Wouldn't a giant steel or stone vat work, in theory?

You'd still need a heat exchanger at some point, and you want a lot of surface area and thin walls for that.

Random thought experiment -- why not just drop it in the middle of a lifeless desert, forget about heat exchangers, and just let it slowly melt its way down through the crust of the earth? Assuming it went straight down and into the mantle, it would probably not impact the ecosystem.

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

#330

Post by AtlasBarfed »

marshray wrote: post #42

I think it's disingenuous to argue the economics of nuclear without mentioning: "DOE reported that it faced an estimated $494 billion in future environmental cleanup costs — a liability that roughly tripled during the previous 20 years." https://www.gao.gov/assets/700/696956.pdf

Can LFTR reactors rebreed/run on spent fuel waste, and has a cycling process for filtering out inert elements?

Seems like we should be running those just for those.

Post reply on HN