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Small nuclear reactors: tiny NuScale reactor gets safety approval

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

#161

Post by shortandsweet »

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…

You'd hope so. Reactors yes, but not spent fuel pools. Everyone misses things. I've found 3 design flaws myself in the industry. Not too big of a deal as actions can be taken to mitigate some of the flaws. The other flaws are less probable of causing an issue due to redundant and diverse systems but there's always the off chance...

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

#162

Post by ktal »

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…

https://interestingengineering.com/crashed-jet-nuclear-react...

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

#163

Post by tgsovlerkhgsel »

phkahler wrote: post #144
adammunich wrote: post #85

Earlier quoted context omitted.

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.

Around 600-700 kWh per cubic meter depending on temperature. The reactor outputs around 200 MW thermal.

So if you have one of them in an olympic size swimming pool 50x25x2 meters, 2500 m^3, it'd need ~8 hours to evaporate the whole pool at full output.

If you assume decay heat as 1% of regular output (https://en.wikipedia.org/wiki/Decay_heat), you'd need to add (or have stored) ~3 m^3 of water per hour, or slightly less than a liter per second, to keep it from melting down.

If you assume an average of 2% for the first two hours, that'd be 8 MWh -> 12-13 m^3 for the first two hours, so a 5x5x5 = 125 m^3 pool (only considering the part above the "must always stay submerged" level) should be able to cool it for days.

I think _as long as the containment pool is intact_ (and you manage to SCRAM the reactor), this isn't going to be a major issue. But if e.g. an earthquake breaks the pool...

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

#164

Post by throwaway0a5e »

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.

They shot an F4 target drone at a block of "reactor grade" concrete wall back in the 80s and they took measurements and did science on the resulting lack of damage and concluded that a reactor can shrug off one of anything. They didn't change containment buildings to be plane proof. It's just a side effect of the design required to contain a melting down reactor with a sufficient safety factor.

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

#166

Post by Klinky »

dodobirdlord wrote: post #88
marshray wrote: post #67

Earlier quoted context omitted.

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

The world is filled with naturally occurring phenomena far more dangerous than a big pile of low-grade nuclear waste. The really dangerous stuff ceases to exist after a few decades of sitting in a cooling pond, and then what’s left has such a long half life that it’s not particularly threatening. Water is an incredible radiation dampener, and the ocean is already chock full of dissolved uranium. The only reason we do…

You're underplaying the danger and overplaying the value. Who exactly is investing in this "green gold"? If it's so valuable why does no one actually want it, and why is the DoE stuck with half a trillion liability?

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

#167

Post by Symmetry »

SamBam wrote: post #130
DuskStar wrote: post #63

Earlier quoted context omitted.

There's ~4 billion tons of uranium dissolved in seawater, too. Which is enough for a millenia or three - if we used it for all of our power needs.

How much energy would it take to extract one ton of uranium from the ocean?

Well, according to "Sustainable Energy Without the Hot Air"

>Japanese researchers have found a technique for extracting uranium from seawater at a cost of $100–300 per kilogram of uranium, in comparison with a current cost of about $20/kg for uranium from ore. Because uranium contains so much more energy per ton than traditional fuels, this 5-fold or 15-fold increase in the cost of uranium would have little effect on the cost of nuclear power: nuclear power’s price is dominated by the cost of power-station construction and decommissioning, not by the cost of the fuel. Even a price of $300/kg would increase the cost of nuclear energy by only about 0.3 p per kWh. The expense of uranium extraction could be reduced by combining it with another use of seawater – for example, power-station cooling.

https://www.withouthotair.com/c24/page_165.shtml

https://www.withouthotair.com/c24/page_174.shtml

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

#168

Post by Forbo »

karaterobot wrote: post #112
xigency wrote: post #68

Earlier quoted context omitted.

If you could solve climate change for less than that, I think it would be splendid. To put that number in context, which is just an order of magnitude, it's $5,000 for every person on Earth, about 1.5x the current US national debt, and just under the combined market cap of NYSE+NASDAQ. As an existential problem for humanity that doesn't currently have a solution, I think that's a decent cost estimate.

This is in no way to disagree with your overall point, but marine cloud brightening looks like it might be a fairly cost-effective solution to climate change. It's unproven, but not an insane gamble either, and it has little risk of second-order consequences if it doesn't work. All that at a cost of single-digit billions per year. https://en.wikipedia.org/wiki/Marine_cloud_brightening#Costs

It seems to me to make more sense combating the problem at the source. This just seems to add more complexity to the problem. Did anyone else think of Snowpiercer when they saw this?

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

#169

Post by jjoonathan »

adammunich wrote: post #85
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…

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.

Have people really found no way to dump it in an emergency with t^4 transfer?

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

#170

Post by john-shaffer »

tehabe wrote: post #149
DuskStar wrote: post #63

Earlier quoted context omitted.

There's ~4 billion tons of uranium dissolved in seawater, too. Which is enough for a millenia or three - if we used it for all of our power needs.

That is not really the point, it doesn't matter if there is 4 or 40 or 400 billion tons of uranium, the point is that it is finite. At some point, there is none, or better there is no more usable ressources available. This can be shifted with technology and better knowledge but it is still finite. And that is all the point I wanted to make.

The sun also will burn out eventually, and every other star as well.
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