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

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

#231

Post by birdyrooster » Thu, Sep 03, 2020, 10:47 PM UTC

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…

>What happens when the ultimate heat sink is lost?

The reactor ceases to transmit power and is shutdown for maintenance?

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

#232

Post by microcolonel » Thu, Sep 03, 2020, 10:47 PM UTC

rkagerer wrote: post #218

sitharus wrote: post #160

Earlier quoted context omitted.

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.

And if the pool gets a leak?

Patch it? Keep adding water? There's lots you can do with a (non-catastrophic) leak, and building water vessels that don't leak in your lifetime is honestly not that hard.

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

#233

Post by 7952 » Thu, Sep 03, 2020, 10:49 PM UTC

foxyv wrote: post #35

nsxwolf wrote: post #24

Article gave absolutely no indication of its dimensions. How "tiny" is it exactly?

Just barely too big to go on a standard tractor trailer. But small enough to be portable by a oversize load tractor trailer. Kind of like the blades for very large wind turbines in west Texas.

The weight (590 tonnes according to wiki) is likely to be an issue. You need specialist vehicles that connect to a waterway or railroad.

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

#234

Post by godelski » Thu, Sep 03, 2020, 10:50 PM UTC

dylan604 wrote: post #196

godelski wrote: post #64

Earlier quoted context omitted.

My understanding is that these DoE sites are weapon sites, such as Hanford. These are a different ball game than power plants. They use different technologies and have different kinds of waste. Sure apples and oranges are both round fruits, but aren't one to one comparisons. List of sites https://www.dnfsb.gov/doe-sites

Isn't more of Apples to Macintoshes to Honey Crisp to Granny Smith? It's all nuclear waste, but just a different variety.

It isn't. Because we're talking about vastly different types of waste with vastly different toxicity and radioactivity. Power plants also don't produce liquid contaminants. This difference means not only quantity differences, but also vastly different methods for storage are required. Ability to contaminate the local environment is also vastly different. Please stop just guessing at what waste actually involves and read up on it before making such claims.

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

#235

Post by godelski » Thu, Sep 03, 2020, 10:56 PM UTC

marshray wrote: post #86

godelski wrote: post #64

Earlier quoted context omitted.

My understanding is that these DoE sites are weapon sites, such as Hanford. These are a different ball game than power plants. They use different technologies and have different kinds of waste. Sure apples and oranges are both round fruits, but aren't one to one comparisons. List of sites https://www.dnfsb.gov/doe-sites

"In 2015, President Obama found that a separate repository for defense-related radioactive waste was required. DOE reported that defense waste is smaller in volume, less radioactive, and thermally cooler than commercial spent nuclear fuel, stating that a defense repository may be easier to develop." https://www.gao.gov/key_issues/disposal_of_highlevel_nuclear...

This doesn't really counter my argument. The key part is that it has different kinds of waste. There are more factors than the radioactivity. For example sites like Hanford have melted fuel, which might have inspired that green goo that people associate with nuclear waste, but a power plant only produces solid waste. Aerosols and liquids have vastly different storage requirements and added complexity requirements than storing the typical fuel pellets and solid matter from power generating reactors.

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

#236

Post by cm2187 » Thu, Sep 03, 2020, 10:56 PM UTC

I don’t understand what makes small reactors desirable. Don’t you loose economies of scales, not only production, but also demand (ie if you have small local sources of electricity you miss the diversification of the demand you have in the central grid and you need to overprovision a lot more)?

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

#237

Post by 0-_-0 » Thu, Sep 03, 2020, 10:57 PM UTC

Aeolun wrote: post #219

marshray wrote: post #67

Earlier quoted context omitted.

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

SpaceX can launch it into space?

And if something goes wrong at launch spread it over a nice big area

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

#238

Post by ixfo » Thu, Sep 03, 2020, 11:03 PM UTC

meepmorp wrote: post #229

asdfman123 wrote: post #207

Earlier quoted context omitted.

The article states the whole reactor will be submerged in a pool of water, making it passively safe.

Reactor cores continue to produce waste heat when shut down, and water evaporates. It’s passively safe till you run out of coolant, then it’s actively dangerous.

In this case the pool boils off slowly enough from thermal load to let decay heat reduce to the point where air cooling is adequate. So it remains passively safe unless there is a sudden loss of water from the pool.

Engineering a very resilient pond does not feel like as complex a problem as engineering highly complex cooling systems to be resilient.

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

#239

Post by jobu » Thu, Sep 03, 2020, 11:09 PM UTC

cm2187 wrote: post #236

I don’t understand what makes small reactors desirable. Don’t you loose economies of scales, not only production, but also demand (ie if you have small local sources of electricity you miss the diversification of the demand you have in the central grid and you need to overprovision a lot more)?

When I first heard about these small scale reactors 10+ years ago I remember the goals were to build them to be maintenance-free and disposable. They build a self contained unit that needs minimal labor to run, is highly failsafe, and pumps out ~50Mw for roughly 20 years. When it's done they drop the whole unit (roughly the size of a train car) into a concrete grave onsite and plug in a replacement.

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.

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

#240

Post by godelski » Thu, Sep 03, 2020, 11:14 PM UTC

Klinky wrote: post #166

dodobirdlord wrote: post #88

Earlier quoted context omitted.

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?

> Who exactly is investing in this "green gold"?

France[0]

> If it's so valuable why does no one actually want it,

I mean France does... we actually gave them the tech. The reason we stopped is more political. But more people do this than just France, but they are the biggest example since 17% of their entire grid is powered from recycled nuclear. The other reason we don't do it is that it is just cheaper to buy more Uranium than setup reprocessing plants. France doesn't have as easy of a supply chain so it makes sense for them to recycle. Obviously the US's supply chain could change, so access to that waste is a potential benefit.

[0] https://www.world-nuclear.org/information-library/country-pr...