Random Idea - Solar/Wind energy turning Nuclear into renewable?

[mr.WHO]

Since all the doom and gloom on the off topic forum, I'd like to share my contemplation onto something more positive and constructive

Most of us probably already been dozen times over the discussion of green energy vs fossils.


Focusing on main green energy components - Solar and Wind.

Their biggest weakness is their instability and variability - with oscilating between huge peak energy spikes (which are wasteful and dangerous to energy grid) and periods of shortages (wind not blowing, very cloudy weather, or winter).


The obvious solution to this problem is some kind of energy storage, but here is the problem - all of our current energy storage methods are insuficient - e.g. like the biggest build battery station capable to store energy for like 1 hour of usage (I'll greatly simplify this, but e.g. solar producing energy for 12 hours of daylight, but then batter storing only 1 hour of reserve, so you're short of 11 hours of nighttime).

Pretty much the only solid energy storage method is water-pump storage, where you use surplus energy to pump water to uphill storage/reservoir, and then use it again when you drain water down through turbine. Unfortunately this is very geologically and geographically limited.


Now here is my idea, but it would be nice if someone with physics and energy background could check me on this.

My understanding is that we currently have awfully lot of used nuclear fuel rods that are treated as waste and stored in special facilities (e.g. one in Finland?).
Is it possible to "recharge those rods/uranium" back to usable level? You can enrich uranium to weapon grade, so maybe you can enrich it to fuel level as well?

Uranium half-life is like what? 10'000 years give or take? Seems like a very fine battery and energy storage to me.

The idea would be to use solar and wind peaks, to power those energy intense uranium enrichment facilities, charge those fuel rods for surplus and later use.
Then when you have solar/wind slumps, you just increase energy production from nuclear plants.

This also not only solve the energy storage problems, but also energy transfer problem - fuel rods are (relatively) easy to transport across the planet - e.g. You don't need an energy line connection from equatorial super solar farms, you charge the rods 24/7 on-site and then just distribute them to regions that don't have viable solar/wind conditions.


As I mention, someone would need to check me on technicalities (e.g. possibly enriched uranium require different types of Nuclear Plants?).

The only downside I can see it that we would have much more uranium moving all the time (someone could steal and use it for bad purpose) and uranium enrichment beign basic economy instead of "niche military program"

Still, this could change the world for better, turning all those rogue military programs to battery charge stations - why beign a warlords, when you can be new energy sheikh

[Usenko]

Not only is what you say a good idea, it is supremely frustrating that this isn't the normal way that uranium is managed. From a physics perspective this is absolutely a no-brainer. And in fact there are parts of the world where this is routine.

It's not so much a recharging situation, but it makes use of the fact that when you put uranium through a nuclear reactor, only a very small amount of the uranium actually gets used.

(NB - the numbers here are meant more as an illustration. The actual numbers are a bit more complex. However . . . )

A normal nuclear fuel rod is about 10% uranium 235 (the type of uranium atom that actually splits to generate electricity). Most of us know that the relevant equation is E=mc2. C is an enormous number, and c2 is even bigger, so this basically means that a tiny amount of mass is converted into a stonking huge amount of energy.

A consequence of this is that there is actually very little change to the overall composition of the fuel rod, even when it gets used for long periods of time producing vast amounts of energy. Of the 10% that is U-235, maybe 0.1% is actually split. The fuel rod doesn't actually run low on U-235 atoms; rather, the fuel rod gets cluttered with the atoms into which U-235 splits, which includes a lot of atoms called "reaction poisons" - they stop the reaction from happening.

When a fuel rod is cluttered with poisons, it becomes less and less efficient and eventually stops supporting the reaction. At this point it has to be taken out of the reactor. Usually it gets cooled in a pool of water and then thrown away. But it is possible (a mature technology, in fact) to extract the poisons (some of which are actually valuable elements, so could be sold to pay for the process!), and then put the fuel rod back in to be re-used for another cycle.

So why isn't this the way that it's always done? Well, there are a few reasons for this, but the three biggest reasons are:

1) At the moment, uranium is fairly cheap. Buying new uranium isn't a hugely expensive part of a nuclear reactor's costs. Despite a lot of people talking about how uranium is a finite resource which we are using up, the reality is that it isn't really expensive enough to be worth exploring for and building new mines. Even though you have to mine a lot of natural uranium to make a single fuel rod, the amount of money that actually needs to be invested in the fuel rod is low. So putting used fuel rods through an expensive reprocessing process is questionable from an economic perspective[1].

2) Politically it is difficult to get reprocessing plants approved. This is a bit of a bitter irony; it is not at all unusual for certain groups within legislatures to both criticise nuclear energy because of the problems with dealing with waste products, and then at the same time block attempts to build facilities for dealing with the waste products . . .

3) Because of the relatively low prices of renewable energy options, it is often considered uneconomical to invest further in nuclear infrastructure. Personally I think it's bonkers to use natural gas generators as the backup to renewables (nuclear really is a much better fit) but this is the generally accepted wisdom.

Overall then, what you suggest is a great idea, but in the current political and economic environment it is a hard sell.

[1] As I noted before, the waste products removed could actually pay for this; however, nobody has ever really accused humankind of being far-sighted!

[Alan Phipps]

Any reuse/recycling idea is a great idea. However, humans being what they are, there will be real problems:

Since economies of scale will dictate affordability, would many nations (having the technical compatibilities) agree to cooperate/contribute to make international sites commercially viable?
Where and how would the sites be decided? - ie who owns the real estate, how continuing future access is guaranteed to other contributors, is it underground/underwater, etc, etc.
How will security and environmental issues be controlled? - ie safety from accidents, sabotage, weaponisation of the process, ransom opportunities, cooling material/biproduct/waste disposal costs or value recouping schemes, etc.
What if the reality after construction proves less effective/efficient than hoped and there might be better measures already available with less technical risk?

There would have to be joint and determined will to address all these issues at the theoretical stages of the project.

[Chips]

all of our current energy storage methods are insuficient - e.g. like the biggest build battery station capable to store energy for like 1 hour of usage (I'll greatly simplify this, but e.g. solar producing energy for 12 hours of daylight, but then batter storing only 1 hour of reserve, so you're short of 11 hours of nighttime).

Pretty much the only solid energy storage method is water-pump storage, where you use surplus energy to pump water to uphill storage/reservoir, and then use it again when you drain water down through turbine. Unfortunately this is very geologically and geographically limited.

I always thought they could electrolysis water into hydrogen and oxygen with the spare energy -- for later combustion. But it suffers the same problem as any solid storage. It's finite -- and to be able to "charge" in the first instance, you need sufficient excess capacity of energy created. There's also molten salt, used by the solar concentration power plants; but again, scale of population wide coupled with the excess/transmission etc. Try to get any corporate energy company to invest *that* much to provide sufficient spare capacity would be a real high challenge.

Currently though, the best is surely existing tech in the form of "power banks" (like the Tesla power wall). Expensive to install, no idea about last and environmental cost of it -- but 13.5kwh is more than enough for most families for 24 hours. I average about 4kw/h per day in winter, so it'd last me 3 "off grid", provided there's ample to charge it. There's no need for incentives (i.e. min pricing per unit) and once it pays for itself, it's "free" thereafter; better than a centralised energy grid.

At least with nuclear you can always "shove it in a bit further" to generate more on demand, so it's an ideal solution - and reprocessing has been done since the 60's hasn't it? Sellafield is one such place I'm sure? Just the costs seem astronomical and the lead time for new plants is insane, which brings back to "but, profit?!"

Personally, if it was possible to set up small scale wind / solar for individual villages/hamlets, there'd likely be far less "NIMBY!" about windmills once they're informed "past the initial cost, your energy is free... within reason".

Lastly, amount we need could be significantly reduced as well if we changed habits; i.e. no night time cooking; old storage heaters to store heat during day/expend at night, or maybe air pumps sufficient via battery power, no idea. There was a letters page in the Guardian with a guy and girl having their public argument ruled on. He was "she spends too long in shower, i'm trying to save energy..." and you think he's being a real xxxxx about it - until you find out she spends ONE HOUR IN THE SHOWER EVERY DAY. Mental. Remember having "free" hot showers in Greece as water tanks on roof to be heated by the sun.

[mr.WHO]

I guess the equation would be how long it would take for surplus solar/wind to cover the cost of uranium enrichment facility.

This would be tricky, because best places, with best sun exposure or best wind conditions would be remote/undeveloped, so you would need to build whole infrastructure for this from scratch.
Plus, for maximum effect, you would need an access or demand from nuclear power plants, which usually are far from such locations.


Something like France-Algeria (or later and wider EU - North Africa) combo - relatively close to eachother with good access to infrastructure, tech and markets.

Albeit we are going back to issue, if we really want large humps of Uranium in North Africa.
But then, assuming this infractructure investment would boost North African economy, it would solve several problems in one sweep.

[Falcrack]

One way to store energy is through the use of towers, or underground shafts, which have large weights attached. When there is surplus electricity generation from renewable but transitory energy generation, the excess electricity is used to hoist the weights higher. When there is an energy deficit, the weights are allowed to be lowered, powering turbines and regenerating some of the electricity that was used to raise them initially. There would probably be some energy lost in the process, not sure the exact amount.

[mr.WHO]

One way to store energy is through the use of towers, or underground shafts, which have large weights attached. When there is surplus electricity generation, the excess electricity is used to hoist the weights higher. When there is an energy deficit, the weights are allowed to be lowered, powering turbines and regenerating some of the electricity that was used to raise them initially. There would probably be some energy lost in the process, not sure the exact amount.

I've heard about this method, but it scales very badly.
To store large amount of energy - either you need a lot of very large shafts (very location specific), or you need to build multiple skyscraper size towers full of weights.

Edit:
Still, it might be interesting option for old skyscrapers - instead of deconstruction/destruction, you could turn them to such towers.

[Usenko]

One HUGE issue with the weighted towers power storage method is that it involves a lot of mechanical parts, so there's a lot to go wrong.

[mr.WHO]

One HUGE issue with the weighted towers power storage method is that it involves a lot of mechanical parts, so there's a lot to go wrong.

True - when I was a kid, I watched hella lot of a show called "Scrapheap Challenge" where people design and build machine to do specific task from scrap.
The biggest lesson I took from it is "keep it simple, stupid".

Every additional part ads complexity and more points failure/maintenace.

Edit:
I'll use this opportunity for nostalgia train.
If someone has opportunity to watch this, I wholehearthly endorse it:
https://en.wikipedia.org/wiki/Scrapheap_Challenge

[Chips]

I remember seeing a statistic about solar power and the Sahara desert; covering just 1% of the "useless" desert with solar panels (the best currently made) would be enough to power the entire world from solar. The problem is transmission (and storage). But it'd indicate sufficient power to do treatment? I'm sure other locations are available (potentially without the sandblasting drawback!).

To me the storage problem still resides with focussing upon large scale energy storage instead of localised storage. It's easily achievable (its also done with water in parts of New Zealand - my sister isn't connected to mains water afaik, it's all via rain water collection and treat on site). But nuclear removing the requirement seems the ideal solution, and minimising the waste should reduce the distaste some have.

[mr.WHO]

So why isn't this the way that it's always done? Well, there are a few reasons for this, but the three biggest reasons are:

1) At the moment, uranium is fairly cheap. Buying new uranium isn't a hugely expensive part of a nuclear reactor's costs. Despite a lot of people talking about how uranium is a finite resource which we are using up, the reality is that it isn't really expensive enough to be worth exploring for and building new mines. Even though you have to mine a lot of natural uranium to make a single fuel rod, the amount of money that actually needs to be invested in the fuel rod is low. So putting used fuel rods through an expensive reprocessing process is questionable from an economic perspective[1].

This put me in somewhat positive mood.
I was worried that with increase demand for nuclear energy we would eventually ran out of viable minable deposits.
However with this, I should actually be looking forward to it.
This would literally push nuclear from minable to renewable

Unless we figure out something much better, like fusion, it's only a matter of time till we gonna need to put those wasted rods back to good use.


Even with fusion, you still need a huge and dense energy source to kickstart whole process, so it still make nuclear reactors handy and essential.

[Mailo]

So why isn't this the way that it's always done? Well, there are a few reasons for this, but the three biggest reasons are: ...

According to the World Nuclear Association, about 30% of the 400000 tons of spent nuclear fuel rods have been reprocessed. The current capacity worldwide is to reprocess 2000 tonnes per year, moving up to 2800 tons once a plant under construction in Japan is finished.
Note that fuel from PHWR reactors is not well suited to reprocessing, as it only contains 0.2-0.4% of ... interesting stuff. The source did not give how much of the 400000 tons is from PHWR reactors though.

Also, you left out a fourth reason, which is why the US stopped most of their reprocessing. That being that it produces weapon-grade materials (plutonium, amongst others), something you don't want civilians to get their hands on.

This put me in somewhat positive mood.
I was worried that with increase demand for nuclear energy we would eventually ran out of viable minable deposits.
However with this, I should actually be looking forward to it.
This would literally push nuclear from minable to renewable

Unfortunately, reprocessing the fuel rods only slightly lowers the risks and issues with nuclear power, availability of fuel never was a main cause of concern.

Up to this day, noone knows how nuclear waste should be dealt with. The current default of chucking it into a hole and praying is already showing that it does not work, the few pictures leaked from dumps older than 10 years already show barrels leaking and rusted through.
Since a very significant part of the whole production chain is still unknown, a fair and accurate cost of the energy source cannot be calculated in a trustworthy way, making comparisons to the costs of other sources moot.
Note that the whole building the reactor was in counts as nuclear waste as well at the end of its life.
Reprocessing does not make this problem go away, it just lowers the volume that needs to be dealt with a bit.

Also, it has no impact on the risk of incidents similar to Fukushima or Tchernobyl. Yes, the risk for one of those is low, but the potential damage is so immense, it needs to be considered. Actually, it might even increase the risk, as those repurposing sites are now additional places where something can go wrong.

I don't recommend switching off all nuclear reactors yesterday, I am well aware of the reality that we cannot currently do without them, but claiming they are now renewable and should be used for all times is a very dangerous road to go down.

Also, claiming it is now renewable will take the pressure off of trying to develop other sources of power, which might be the worst thing about this.

[mr.WHO]

Up to this day, noone knows how nuclear waste should be dealt with. The current default of chucking it into a hole and praying is already showing that it does not work, the few pictures leaked from dumps older than 10 years already show barrels leaking and rusted through.

That's another reason, not dump them into the hole for 10+ years.
If we managed to reprocess 30%, then it should be resonable to push this even further.
More recycling is good.

Note that the whole building the reactor was in counts as nuclear waste as well at the end of its life.
Reprocessing does not make this problem go away, it just lowers the volume that needs to be dealt with a bit.

That's a valid point, but just like with Chernobyl irradiated materials/zone there are levels of hazard, e.g direct reactor chamber that get irradiated the most.
Still, most of these (keyword most) drop most of radiation after a few decades, comparing to tens of thousands of years with the fuel rods.

However, in the end, in the ground we have less fuel rods (more dense, less volume, but bigger leak/contamination), but we have more "short term" irradiated scrap (reactor parts).
Can't really say one is better than another, especially for anybody that would end up near either.
I guess, with common sence, you might have bigger chance to end up near irradiated scrap metal from reactor, than you could ever be be near used up fuel rod.

[Chips]

If we managed to reprocess 30%, then it should be resonable to push this even further.
More recycling is good.

The problem is that attitude can lead to believing it's a solution; from what Mailo is pointing out, it's not. It's a can/road/kick outcome at best. At worst, it can make the potential issues manifestly worse by false-sense-of-security meaning it's "okay" to carry on as normal and not bother attempting to transition away.

Akin to the idea that planting trees is a solution to fossil fuels - ignoring there's a 50-80 year lead time (growth to max maturity carbon capture, which is what they base it on), and forest fires wiping several plantations out already. It doesn't actually help solve an issue; it just lets us *ignore* it while slapping each other on the back thinking it's no longer a problem and allowing everyone to pollute onwards in a "carry on as normal!" way.

The actual problem is still there.

Now whether that problem is worse than rising sea levels and global people displacement / issues with food production won't be known.

[Usenko]

Also, you left out a fourth reason, which is why the US stopped most of their reprocessing. That being that it produces weapon-grade materials (plutonium, amongst others), something you don't want civilians to get their hands on.

You know, that's an Australian thing. The link between nuclear fuel and nuclear weapons isn't as strong here. I simply didn't think of that.

But you're right - the process of reprocessing can lead to weapons grade stuff.