Subterranean Nuclear Power Plants

[Aanker]

So I have been thinking about this for a while.

As you know, engineers in countries such as Sweden and the United States (and probably Canada, too, if my memory does not fail me) are working on ways to store nuclear waste materials deep underground.

Now, this storage doesn't take place in any kind of underground, but rather, in the ancient "cores" of continents, formations which I believe are known as cratons. The preferred rock is granite, which, as I believe most of you know, is a durable rock. Some of the most ancient rocks on Earth are made of granite, a testimony to its extreme reluctance to be worn down. Additionally, the plutonic masses where you would typically find granite are stable and not prone to discouraging events such as major earthquakes, volcanism or the like. This means that one could probably quite safely say that storing radioactive materials at great depths in these primordial masses of rock is not such a bad idea. The problems are mostly related to corrosion, but there are a handful of materials to slow that down, and even if the radioactive materials should leak out into the immediate surrounding rock, the dangerous water will be some five hundred meters below ground.

So.

Why not build full-fledged reactors here? I can see a number of advantages. First off, there's plenty of water to be had. By creating shafts for the purpose of gathering water, the power plant would have access to a more or less endless supply of coolant. Secondly, the reactor would be well protected. Tsunamis destroying the backup power generators? Nope. Tsunamis destroying anything at all? Nope. In fact, few, if any, exterior events would have an effect on the power plant. Thirdly, backup power generators could perhaps use geothermal power by drilling even deeper shafts, and so would not have to rely on any fuel, which could in the event of an emergency become hard to acquire.

But perhaps most attractively, it would have very few effects on the environment above it. Venting tunnels will still probably be needed, but one could perhaps create waste shafts for the purpose of injecting radioactive dust emitted during an emergency, preventing such dangerous material from reaching the surface. Storage of waste materials underground is a better alternative than sending them for storage elsewhere, a process that involves significant risk should anything unexpected happen.

Why is this not attempted or researched in nations with access to stable underground volumes of rock? Is there an inherent weakness in the whole idea of a subterranean nuclear powerplant, or is it just not cost-effective?

Please excuse any spelling mistakes, this was written on an iPhone after all.

[PointOfViewGun]

Many things to consider:

Earthquakes could have a much larger effect on the plant.
In case of a leak the plant could contaminate water supply for the ground.
The cost of building such a plant makes it ineffective.
It would be much harder to intervene in case of an emergency.

[Blau&Gruen]

You would need to transport the energy where it is used and the grid causes costs and losses.

"Additionally, the plutonic masses where you would typically find granite are stable and not prone to discouraging events such as major earthquakes, volcanism or the like."

These are not very good places to place highly radioactive materials because Plutonits while containing old material with Gneisses and Granites are where they are because of tectonic activities.

The cooling would be an issue if you dig in nuclear facilities, too.

The main problem is the disposal of used highly radioactive materials and that's where the old and stable geological situations in your proposal make sense. I guess, the best sites are old sediments, on stable continental plates with few tectonic activity. But it all depends of how long the half-life period of a type of waste is. Some waste turns out to be unproblematic after a few decades, other takes tens of thousands of years.

[Aanker]

You would need to transport the energy where it is used and the grid causes costs and losses.

Would that not be rather unproblematic though? I mean, a tunnel for power lines can't be that expensive to drill or maintain.

"Additionally, the plutonic masses where you would typically find granite are stable and not prone to discouraging events such as major earthquakes, volcanism or the like."

These are not very good places to place highly radioactive materials because Plutonits while containing old material with Gneisses and Granites are where they are because of tectonic activities.

As I said though, we are talking about cratons, and that means the stable "core" of continents. Take for example the Baltic Shield; it is an occasionally 3.8 billion years old formation consisting of vast amounts of granites and gneisses. There is no chance of tectonic activity at all, at least not within the time frames we are considering.

The cooling would be an issue if you dig in nuclear facilities, too.

Why? You have a virtually limitless supply of coolant.

The main problem is the disposal of used highly radioactive materials and that's where the old and stable geological situations in your proposal make sense. I guess, the best sites are old sediments, on stable continental plates with few tectonic activity. But it all depends of how long the half-life period of a type of waste is. Some waste turns out to be unproblematic after a few decades, other takes tens of thousands of years.

That's strange though, since waste storage isn't actually considered for old sediments, but for, as I said, old, stable granite formations. Those aren't going to be weathered down or face some other gruelling fate within the next thousand, or million, or even billion years.

[PointOfViewGun]

I would much prefer submerged or floating nuclear power plants.

[Blau&Gruen]

Or none if nuclear fusion is within reach, at least in broader terms. I mean "we" have found the Higgs particle (possibly), so making ITER run, should work out sooner or later.

[PointOfViewGun]

Or none if nuclear fusion is within reach, at least in broader terms. I mean "we" have found the Higgs particle (possibly), so making ITER run, should work out sooner or later.

I remember a lab where they've actually managed to create partial nuclear fusion using high energy lasers. Can't remember it's name though.

A submerged or floating nuclear reactor is still a good idea in my opinion. You can have something like a submarine or an aircraft carrier to supply energy to coastal regions and when you have better ones you can actually sell the whole thing.

[The Hedge Knight]

I think the main issue here is size and for example the need for say cooling towers. If you have ever walked up to a nuclear plant you might go 'woah big'. One might also observe one of the strongest arguments for nuclear atm is the relatively low cost per unit of energy versus other methods of power generation. Once you factor in digging an enormous hole a couple of miles underground along with transportation and infrastructure that cost is going to explode reducing the viability of nuclear versus hydrocarbons.

its also worth noting the availability of locations. Power plants are generally dispersed to cover entire national grids and yet suitable underground locations probably arent (not that I know ).

[Aanker]

THK is on the spot, cost and size are the limitations:

http://www.newscientist.com/blogs/on...ndergroun.html

However, it has apparently been used for at least one French reactor, decommissioned in 1991:

http://www.neimagazine.com/story.asp?sc=2057722

So coupled with technological innovations, this method of constructing reactors could prove more attractive.

[Sphere]

The growing trend in new idea's for nuclear plants is towards smaller, lower energy reactor designs with cores that cannot physically melt down.

Things like Pebble-bed reactors or thorium based reactors.

The typical reactors we think of are actually a legacy of the cold war, as high-power, Uranium fueled, rod controlled reactors are needed to produce large quantities of Plutonium used in advanced weapons. This is where research and design was focused for decades.

[Aanker]

What happened to the molten salt reactors, by the way?

[DaVinci]

As you know, engineers in countries such as Sweden and the United States (and probably Canada, too, if my memory does not fail me) are working on ways to store nuclear waste materials deep underground.

Into Eternity

[The Hedge Knight]

What happened to the molten salt reactors, by the way?

Didn't contribute to the Manhatten project essentially so got sidelined. May see them coming in but it depends on how cost effective etc they really are, there is also a lack of experience in the field of new reactor designs which hinders innovation due to the inherent potential for catastrophe with nuclear reactors (imagined or real). Its well known that current Gen II-III reactors are very safe so long as they are used correctly so some would argue there is not a great incentive to change.

Live until 2030 and find out I guess .