Saturday, March 14, 2009

Safe acceptable nuclear power? Here's a way...

Mephistopheles flying over Wittenberg, in a lithograph by Eugène Delacroix. Image credit: WikipediaUse now; pay later ... a Faustian pact with fossil fuels: Burning fossil fuel the way we do now could almost have been designed to seriously endanger humankind and myriads of other forms of life on this planet. You want climate chaos? Okay, just burn up all that coal, oil and gas as fast as you can and you'll get a climate guaranteed to cause a mass extinction which will likely include humans. Mephistopheles, to mix metaphors, gets his pound of flesh. Suffering and mega-death are part of the fossil fuel package, clearly visible to those who can see beyond the PR smoke of the fossil fuel industry. So can we have our energy cake and eat it too? Yes, if we eschew fossil fuels and look for alternatives.


Renewable energy gap: I'm enthusiastic about renewable energy. I've built an eco-cottage (massive insulation) and a passive-solar conservatory for heating my stone-built farmhouse. I'm about to install an air-source heat pump and, in a few months, I hope to set about the installation of a grid-connected 6kW Proven wind turbine. I live a simple, low energy life. I travel very little, never fly and burn wood grown on this farm in my woodburning stove . I also plant trees. And my aim? To be carbon neutral.


Most people can't do many of these sorts of things if they live in towns or cities. They need - and expect to have - electric energy available at the flick of a switch. So do I! So... can renewables like wind and solar power deliver the energy we need? Unfortunately, the answer - for the time being - is no and all the green bluster about solar, wind and waves being able to do it is just naive. In time - by which I mean decades - renewables could and should power the planet when we have built infrastructure like supergrids, vast solar arrays in the Sahara desert and so on. But for now, renewables provide just a few percent of total electric energy used. When the wind doesn't blow and the sun doesn't shine, they're useless. This winter, there have been weeks of cold grey weather without wind. The lights still work because of fossil fuel... and nuclear generation.


Choices: We all want the lights to work when we need them. Almost every modern gadget and convenience depends utterly on dependable electricity supply. So we have choices to make:
  1. carry on burning fossil fuels like there was no tomorrow... which there won't be
  2. eliminate fossil fuels as soon as possible whilst building up renewable supply systems
  3. build nuclear power stations to replace coal-fired plants as quickly as possible, whilst pursuing renewable generation also as fast as possible (part of the much vaunted Green New Deal which may or may not come to pass)

Option 1 means disaster and ought to be unacceptable to anyone who cares about the future for their children and the rest of life on our despoiled planet.

Option 2 means many years of unreliable electricity supply with frequent power cuts. It would work if everyone was prepared to undergo hardship: cold houses, no lights, no TV, no computers for much of the time. But almost everyone would find this unacceptable too

So we're left with Option 3. Nuclear power stations have been working away, generating reliable baseload power for many years. There have been serious problems and even a disaster or two, but modern designs have good safety records. Unlike coal, they almost never kill people.



Protests: It goes without saying that any attempt to build new nuclear plants in countries like Britain will result in massive protests. The reasons people protest against nuclear plants are well known and often justified. At the very least, the massive reactor containment structures are eyesores and at the end of the reactor's life will have to remain there for many decades while radiation levels decay sufficiently for dismantling. Then there's proliferation and the unsolved radioactive waste problem. These are genuine causes for concern.

Protests can and do delay construction, sometimes for years. We haven't got years to cut carbon emissions. So is there a way to make nuclear power more acceptable to people who would otherwise protest? And is there a way to make it even safer than it is now? I think there is...



Out of sight, out of mind: If you visit Llanberis in North Wales, you'll probably not be aware that there's a major power station there. Where is it? You can't see all the usual structures. The reason is because it is completely underground. So why not take that notion further? Why not build nuclear power plants underground too? The size of excavation needed for a nuclear plant is comparable to the Dinorwig pumped storage power station in Llanberis, as my drawing shows.
Size comparison between the Sizewell PWR and Dinorwig pumped storage excavations
Let's consider the advantages that underground construction would offer:

Advantages

  1. because the containment is unbreachable (given proper choice of ground conditions, hydrogeology and rock types), reactor assemblies would be immune to military attack from the air and also from suicide bombers. Containment above ground could not withstand bunker-busting bombs or small nuclear devices, the latter possibly 'delivered' by suicide vehicle. In our dangerous world, these are possibilities
  2. such unbreachable containment is also immune to accidents, whether external (e.g. crashing airliners) or internal such as major loss of coolant (Three Mile Island) or even Chernobyl-style meltdown disasters. Building robust containment structures above ground is hardly cheap and uses a heck of a lot of greenhouse gas-emitting (in manufacture) steel and cement!
  3. virtually no decomissioning costs: you could more or less just walk away and slam the door. Monitoring would be needed, as for underground nuclear waste repositories, but because nothing irradiated is above ground, access would only need to be minimal. In addition, there would be no need ever to remove irradiated fuel assemblies unless the fuel is to be reprocessed. When the reactor reaches the end of its operating lifetime, the whole facility could be sealed, complete with its spent fuel.
  4. there will be protests at each and every new surface nuclear build with endless public enquiries because of protests. Underground plants would demolish most of the objections. Public acceptance and planning consent should be straightforward since there wouldn't be much surface infrastructure to object to. Most of the usual public fears and objections would cease to be serious issues. It also means that off-the-shelf reactor designs (like the PWRs used throughout France and the most of the USA) could be built even though they might not be as potentially safe as so-called 'fourth generation' reactors, because of the additional safety conferred by underground plants. Waiting for unproven safer designs could lose us another decade.

Disadvantages

Cost: I have no idea how much underground siting would add to a budget. But if you take into account minimised decommissioning costs (not historically factored in to the cost of nuclear power as we are now finding out) and spent fuel disposal possibilities, I would guess that it would be completely viable.The economics are only artificially marginal because there's no carbon tax. Anyway, what price security and safety? And if a power utility wanted to re-use as much of the infrastructure as possible at the close of the first reactor's design life, it could just dig another chamber and build its new (improved) reactor next door. Power lines, turbines, transformers etc. all remain to be used again

So far as I know, no-one has ever tried costing it. As my drawing (above) shows, the actual reactor vessel and primary heat exchangers are really quite small structures because of the high power density which nuclear generation allows. So the chamber would be no larger than many others routinely built for different purposes. The reactor assembly could even be built in a modified abandoned mine (e.g. salt mine). Of course, any such underground site depends on there being a cooling source nearby (river, lake, sea) for condensing steam from the turbines. All the non-radioactive sections of the plant could be above ground to reduce costs.

Location: Finding suitable underground conditions, especially in flatter rainy areas with fast-moving groundwater circulation, could be a problem. A Llanberis-like site could, in theory, be ideal because the excavations could be made within the steep valley side so that any groundwater would drain out by gravity. And just outside are two deep lakes (see Cooling, below).

Cooling: Like any steam-driven turbines, cool water is needed both for raising steam and for condensing it. There's no reason for the turbines and cooling systems to be located underground since these aren't in contact with radioactive parts of the circuit. So much of the plant could, like conventional plants, be located by a river or the sea.

So... if we are to have nuclear fission generation on a larger scale to tide us over until fusion power and renewables come to our rescue, why not build all nuclear plants underground? I think this reasonable question deserves a reasonable answer.

Further reading: You may like to look at Nuclear power... safe underground and The Future of Nuclear Power, both in this blog series.

6 comments:

M. Simon said...

We may not have to be tided over for long if this works out:

Bussard's IEC Fusion Technology (Polywell Fusion) Explained
Why hasn't Polywell Fusion been fully funded by the Obama administration?

kaleidoscope eyes said...

very interesting, this article definitely got me thinking.

if you happen to enjoy other environmental websites I stumbled upon this one: http://buildakinderearth.com

Rasmus said...

Doesn't have to be underground. Just design them in a more appealing way. Take this task out of the hands of engineers and hand it to architects, artists, industrial designers.

This idea is mentioned very briefly in this most excellent presentation (audio available)

http://www.slideshare.net/robert.hargraves/aim-high-1388496

Melody said...

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Anyway, I didn't mean to miss the point, then congratulation for this pretty well done piece of work!

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John Small said...

London is flat and rainy, but there's a layer or gault clay underneath it. If you built a suite of disposable nuclear reactors underneath the gault layer there would be no issues with ground water movement. Above ground there's plenty of cooling water, and it's right where the customers are.