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Why nuclear energy is our best option at the moment

energyrealityproject.com

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Re: Why nuclear energy is our best option at the moment

#381

Post by chc »

beat wrote: post #372
adventured wrote: post #223

Earlier quoted context omitted.

I should add, that's just for the largest US plant. The Kashiwazaki-Kariwa monster in Japan, with seven reactors, was capable of producing nearly 8,000 MW on just ~1,000 acres. Or upwards of 50 to 80 times what the best utility solar installations today can produce at max output on the same amount of land. https://en.wikipedia.org/wiki/Kashiwazaki-Kariwa_Nuclear_Pow... The Solar Star installation could end up being t…

Solar star is theoretically capable of about a terawatt on about 4k acres, so that makes the reactor about 15-20 times as efficient. Still a huge difference, but don't hype the numbers too much.

I can't find any source suggesting the Solar Star is capable of 1 TW output with 4000 acres. SunPower's own fact sheet† gives about 1/1500 that capacity for the 3200-acre installation. Where did you hear this?

† http://us.sunpower.com/sites/sunpower/files/media-library/fa...

Re: Why nuclear energy is our best option at the moment

#382

Post by beat »

chc wrote: post #381
beat wrote: post #372

Earlier quoted context omitted.

Solar star is theoretically capable of about a terawatt on about 4k acres, so that makes the reactor about 15-20 times as efficient. Still a huge difference, but don't hype the numbers too much.

I can't find any source suggesting the Solar Star is capable of 1 TW output with 4000 acres. SunPower's own fact sheet† gives about 1/1500 that capacity for the 3200-acre installation. Where did you hear this? † http://us.sunpower.com/sites/sunpower/files/media-library/fa...

Gigawatts, not terawatts. My bad.

579mwh ~= .6gwh, on 3200 acres. Assuming a larger 4000 acre site and some efficiency gains on this immature tech, a gigawatt seems reachable.

Re: Why nuclear energy is our best option at the moment

#383

Post by mixmastamyk »

Asbostos wrote: post #333
mixmastamyk wrote: post #287

Earlier quoted context omitted.

Molten sodium was at the heart of the Santa Susana nuclear disaster in southern California, which was covered up for fifty years. Needless to say, I'm skeptical.

Vaporized sodium is at the heart of nearly every streetlight. They're not causing disasters. Just having the same material doesn't make the safety the same.

Yes, also it's been fifty years, so I'm sure tech has advanced. I didn't say I wouldn't consider it, just that skepticism is warranted, due to frequent lying about risk.

Re: Why nuclear energy is our best option at the moment

#384

Post by xg15 »

vonmoltke wrote: post #183
mikeyouse wrote: post #132

Earlier quoted context omitted.

Are you honestly arguing that dozens of mSv of radiation annually are safe? That big bad government is preventing people from doing what they want? 50mSv is approaching the level of guaranteed higher incidence of cancer -- If you lived in the exclusion zone, you'd be receiving that every single year for the rest of your, and your childrens' lives. Canada did a survey a few years ago of all their nuclear workers, at m…

> Are you honestly arguing that dozens of mSv of radiation annually are safe? Yes, I am (despite the downvotes). The average background dose at sea level is 4mSv/year. A chest CT scan is 7mSv. The EPA has declared that 50mSv/year is perfectly safe exposure for nuclear, and any other, workers. > That big bad government is preventing people from doing what they want? I shouldn't address this, but I feel the need to. Yo…

> The EPA has declared that 50mSv/year is perfectly safe exposure for nuclear, and any other, workers.

So when a government agency declares a radiation dose safe, the measurement is immediately to be trusted, yet when it declares them unsafe and creates exclusion zones it is "overcautious"?

Re: Why nuclear energy is our best option at the moment

#385

Post by pdkl95 »

mentando wrote: post #365
PolLambert wrote: post #162

Earlier quoted context omitted.

Since regulations don't allow any other option e.g. the US doesn't allow reprocessing. Also: what better place to temporarily store nuclear waste in the exact same place where it is produced where safety and security measures are already in place?

I will try without the condescending tone of the other commentor: Why does this not increase the possible damage a meltdown would cause? Or does it increase the possible damage, but the security is high enough that the expected damage is lower than storing it elsewhere?

First, a containment structure[1] is a key feature in any reactor[2]. These are massively over-engineered specifically to contain even unlikely problems. We learned that this was important after the SL-1 accident[3]. As you suggest, this is a feature designed to fail safely - the containment should keep the rest of us outside the building safe, and doesn't say anything about what happens to the stuff in side.

> meltdown

This term is thrown around a lot, and while solid fuel melting in a traditional reactor is a serious event, a lot of people seem to think that "meltdown" is some kind of terrible or damaging event. The reason people in the nuclear industry panic over a possible meltdown has little to do with safety; up until that point you could - in theory - still reasonably believe that the reactor could be fixed and (eventually) restarted. After a meltdown, you have to assume the core is trashed and is now a financial liability instead of your main source of revenue.

Meltdowns are a terrible event financially. The actual melting of the fuel involves the passive-safety, which are usually designed to drain that fuel into (multiple) areas where it can cool down without criticality risk.

All of this is still discussing very old features. This is like worrying about today's computers because vacuum tubes are fragile and need to be replaced when they burn out. Modern reactor design is very different, because we learned form the problems that happened in the original designs, just like any other technology. Unfortunately, propaganda based on radiophobia has been a serious roadblock. Ironically, this means we're stuck using older designs that should have been replaced decades ago with modern reactors that emphasis passive safety.

If you're interested in a brief overview of these problems (and why some of us believe thorium breeder reactors are the answer for many of these problems), I recommend watching "Th"[4]. Just remember it's an overview, and they skip over some of the details to keep it short.

[1] https://en.wikipedia.org/wiki/Containment_building

[2] a feature that was missing at Chernobyl, which is one of many reasons that accident affected such a large area

[3] https://www.youtube.com/watch?v=qOt7xDKxmCM

[4] http://thoriumremix.com/th/

Re: Why nuclear energy is our best option at the moment

#386

Post by ars »

yk wrote: post #376
ars wrote: post #327

Earlier quoted context omitted.

What are you talking about? No it doesn't.

The designs I have seen dissolve the spent nuclear fuel in phosphoric acid and then operate with liquid fuel. ( Perhaps there are proposals that do not operate like that, but I think you want to homogenize the fuel as much as possible which means some kind of liquid fuel.)

How do you superheat phosphoric acid? Wouldn't it dissociate?

It's not used for an active reactor, but rather to dissolve cold fuel and extract more usable uranium.

Liquid fuel reactors don't use phosphoric acid, they use uranium tetrafluoride (a salt) or water.

Re: Why nuclear energy is our best option at the moment

#387

Post by Turing_Machine »

onli wrote: post #358
Turing_Machine wrote: post #273

Earlier quoted context omitted.

Which grid-scale wind or solar projects are profitable without being subsidized by the government? I'm not aware of any.

Wanted to make the point that you don't have to have grid-scale projects if you distribute it. One windmill at a time, each with its own financement, investors and profitability. I admit that was not clear.

Virtually all solar and wind projects of any significant size are heavily subsidized by the federal, state, or local government. I am unaware of any exceptions to this.

Re: Why nuclear energy is our best option at the moment

#388

Post by [deleted] »

datenwolf wrote: post #359
paulsutter wrote: post #272

Earlier quoted context omitted.

Could you clarify the "huge problem of load-following" for nuclear power plants? My understanding is that it's mostly a licensing issue rather than a technical issue, and in practice hasn't had a big impact on CF[1] [1] https://www.oecd-nea.org/nea-news/2011/29-2/nea-news-29-2-lo... "Most of the currently operating Generation II nuclear reactors were designed to have strong manoeuvring capabilities. Nuclear power pla…

There are also physical limitations with load following. In a fission reactor you're dealing with a steady state of influx of fission products (by the primary nuclear reaction) and the delayed decay of those products. In fact a large portion of the heat generated by a fission reactor comes from the delayed decay of the fission products. Furthermore some of the fission products are very efficient neutron catchers; not…

[deleted]

Re: Why nuclear energy is our best option at the moment

#389

Post by iaw »

beefman wrote: post #311
iaw wrote: post #289

Earlier quoted context omitted.

I am unaware of any kind of practical nuclear fission machine that doesn't require a high initial capital investment. Could you link some examples of commercially operating units? It has been a few years since I was in the field but I was unaware of any proven changes to the fundamental economics of the industry.

There's a good chance you can see one at your local university or shipyard. The post to which you're replying doesn't use the terms "proven" or "commercial", so let's not move the goalpost. Then we can talk about YC-funded startup UPower, Fluor-owned corporation NuPower, etc. Studying engineering is also a good way to reduce reliance on examples.

I was unable to find any data on the 'NuPower' technology; could you provide links?

What I found on UPower indicated that it's a nuclear thermal battery, I love that technology but they aren't legal and wont be because of widespread concerns about terrorism and radioactive contamination.

Also, my educational background is in engineering and I have worked on determining whether it's financially feasible to build power plants for a living. I would really love it if you could provide some evidence for your arguments.

Re: Why nuclear energy is our best option at the moment

#390

Post by yk »

ars wrote: post #386
yk wrote: post #376

Earlier quoted context omitted.

The designs I have seen dissolve the spent nuclear fuel in phosphoric acid and then operate with liquid fuel. ( Perhaps there are proposals that do not operate like that, but I think you want to homogenize the fuel as much as possible which means some kind of liquid fuel.)

How do you superheat phosphoric acid? Wouldn't it dissociate? It's not used for an active reactor, but rather to dissolve cold fuel and extract more usable uranium. Liquid fuel reactors don't use phosphoric acid, they use uranium tetrafluoride (a salt) or water.

No, you want to burn all the short lived isotopes, not just Uranium. So the designs I am talking about use spend fuel dissolved in acid as a fuel. There is also spent fuel recycling, where you take Uranium and Plutonium out of spent fuel and manufacture MOX fuel, but that is an entirely different process.
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