441–450 of 554 posts
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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 was an ancient design that didn't have many safeguards. This one had safety built in from the start, and it's smol and can be contained easily.
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Our largest manmade lakes are created by dams, and you can find plenty of example of dams failing in ways that don't take many days. If our smallest manmade lakes (swimming pools) can leak a lot, and our largest manmade lakes (dams) can also leak a lot the idea there's an in-between size that doesn't leak might need a bit of elaboration.
There's a big difference between a dam and a pool; the pool is supported by the ground, and even if you bash holes in it, the water still has to find somewhere to go. Also, pools are not typically built from concrete and stainless steel. The safety requirement here is not "doesn't leak", it's "holds most of the water for 30 days (after which water is not required)". You would have to get an implausibly-large leak, du…
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The kind of nuclear submarines governments are trying to raise and properly dispose of, because they're worried bioaccumulation will taint their fish stocks? [1] [1] https://www.bbc.com/future/article/20200901-the-radioactive-...
And governments are known for not over reacting to anything related to nuclear power /s
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Nuclear engineer here. I've read through a good portion of the regulatory submission to the NRC and have a few takeaways that oppose some of the less-well-informed takes in this thread: - The reactor differs substantially from existing PWRs by encasing the primary in double containment, using natural circulation flow for both normal operation and emergency cooling. There are no pumps needed (or installed) to move coo…
What is the maximum external temperature the design can operate in? Can you build it in hot places to power air conditioning and things like that during the worst days?
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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…
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…
Nuclear engineer here. I've read through a good portion of the regulatory submission to the NRC and have a few takeaways that oppose some of the less-well-informed takes in this thread: - The reactor differs substantially from existing PWRs by encasing the primary in double containment, using natural circulation flow for both normal operation and emergency cooling. There are no pumps needed (or installed) to move coo…
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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.or…
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Nuclear engineer here. I've read through a good portion of the regulatory submission to the NRC and have a few takeaways that oppose some of the less-well-informed takes in this thread: - The reactor differs substantially from existing PWRs by encasing the primary in double containment, using natural circulation flow for both normal operation and emergency cooling. There are no pumps needed (or installed) to move coo…
So it requires gravity. It may seem trivial, but how would this thing react if suddenly not mounted vertically, say if it got knocked onto its side while running? Would coolant still flow as planned?
As far as I'm aware we've never had a nuclear reactor go sideways, and it's kinda ludicrous to even ask. It's one of the most massive structures, built on bedrock because it's too heavy to be built on anything else, and even these "small" reactors will be incredibly heavy.
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I assume they meant T^4 radiation (Stefan-Boltzmann law): https://en.m.wikipedia.org/wiki/Stefan–Boltzmann_law
Nuclear reactors run at cool temperatures compared to say gas turbines. And they are powerful. So the surface area for radiative cooling is proportional to the power divided by temperature to the fourth power. So the cooling would need to be very big.
I'm sure there's a reason why it hasn't been done. Maybe you really do need high enough temperatures that you can't engineer compatible cladding, or it's hard to make IR windows low-loss enough to pass the energy, or something. Still... fourth power! The temperature you need the "lightbulb mechanism" to withstand is the fourth root of power/area! That's a powerful wind at one's back! It's easy to think of reasons why it might be impossible but if it's "just" a hard engineering problem then that's where things get interesting.
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In France this 'success story' led to a state law (2015-992, from 2015, the "loi relative à la transition énergétique pour la croissance verte") stating that the part of nuke-produced electricity must fall to less than 50% in 2025, from 72% then, and that renewables must replace it. In France nuke-power is backed by gas (which produced 10,3% of gridpower in 2017). The sole reactor currently planned (Flamanville-3) is…
I'm unsure what you are suggesting here, so I want to be extra clear about the French policy and current state of affairs. As in stands, France has one of the lowest CO2 emissions per capita[0][1]. No one is saying that we should _only_ use nuclear. Not diversifying your energy portfolio is a terrible idea. France is trying to reduce its dependence upon nuclear (which is a good idea) and replace its fossil fuel infra…
FYI I'm French.
> France has one of the lowest CO2 emissions per capita
Apples and oranges...
France has wayyyy less factories than Germany, however it imports goods produced elsewhere. CO2 emitted in order to produce those goods is to be accounted for!
Real CO2 emission: France: 6.92t/year/capita in 2017 Germany: 10.83t/year/capita in 2017
Source: https://ourworldindata.org/grapher/prod-cons-co2-per-capita?...
https://ourworldindata.org/grapher/prod-cons-co2-per-capita?...
Moreover Germany is richer than France (=> more equipment => more CO2 emitted).
GDP per capita (PPP): 52.4k€/capita versus 47.6
At this point from your data 9.13/5.2 (1.75) ratio we are back to 9.74/6.92 (1.4)
Germany's climate is much colder (=> more heating => more CO2 emitted). Heaters in Germany are massively oil-based systems because there was an historic low taxation on heating oil. Sadly I can't find solid data.
Food for thought.
> Not diversifying your energy portfolio is a terrible idea.
Yes, indeed. However it doesn't imply that we must use each and every energy source, without any consideration for all its characteristics. Nuclear plants and their waste are dangerous, and contrary to a common belief they cannot solve the climate challenge while letting us avoid changing our habits.
> You will not find pro-nuclear supporters upset with France's decision to reduce their dependence on nuclear
Some, in France, think that we should go full nuclear, and they fight for it. Example: https://www.enviscope.com/lassociation-des-ecologistes-pour-...
Other think that we may have to chose a "100% renewables" option. Example: https://www.ouest-france.fr/environnement/nucleaire/nucleair...
In 2010 in the US 8.4% of the energy comes from nuclear plants, and renewables (hydro included) produce approx 6% Source: https://en.wikipedia.org/wiki/Energy_in_the_United_States#En...
That is to say in order to only 'decarbonate' the energy sector (there are other sectors to decarbonate!) thanks to nuclear power the US should deploy ~11 times more nuclear power capacity than it already has, and adapt or retrofit all energy-consuming equipment in order to have it use gridpower (or to embark some nano-reactor). This seems completely unrealistic, from many perspectives. Even a mix (nuclear + renewables) with 3 to 5 times more nuclear seems unrealistic.
'CO2-clean' energy production as a whole isn't possible.
Electricity production accounts for 27% of CO2 emissions, and 63% (of the electricity) is produced by fossil fuel, and 20% by nukeplants). Source: https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emis... => quickly reducing CO2 emission by 27% by producing all gridpower does not imply any adaption/retrofit of any existing stuff, however it implies a 5-fold increase of nuclear capacity or a balance with renewables (taking into account the baseload) and would not be a decisive progress as the GIEC invites us to "fall by about 45 percent from 2010 levels by 2030, reaching 'net zero' around 2050". Source: https://en.wikipedia.org/wiki/Special_Report_on_Global_Warmi...
Therefore, indeed, "the proof is sitting right there, all you have to do is look": in order to reduce emissions we have to consume wayyyyy less energy and stuff.
> What we are arguing for
IMHO the sole realistic option is "let's drastically reduce our energy & stuff needs", or even "degrowth". Even an "all-nuclear gripower" plan, which is completely out-of-reach, cannot fix the climate problem: gridpower offers only about 25% of the consumed energy in advanced countries, and beyond energy-production many human activities emit huge amounts of CO2 in ways we cannot modify, or at best cannot modify quickly (agriculture comes to mind, as in the US it produces ~10% of the emitted CO2, and feeding cows with gridpower may prove to be difficult).
> _today_ we have the technology
We don't know, _today_, how to make a fool-proof nuclear plant nor how to effectively dispose of its waste. We don't know how to solve the NIMBY challenge. Financing a nuclear plant becomes more and more difficult. Even building it is a major ordeal (see the EPR projects). And even if we fix all this there is no all-nuclear approach able to tackle the challenge (dividing CO2 emissions by 3).