Win win: Energy from (nuclear) waste

Molten-Salt Reactor Experiment, ORNL

Did you know about the Waste Annihilating Molten Salt (WAMS) reactor idea? I didn't, though it sounds similar in principle - passively safe - to the molten salt thorium reactor which ran for 4 years at Oak Ridge National Laboratory. Why aren't these means of both generating massive amounts of power plus ridding the world of highly active nuclear waste at the top of the energy agenda?

Waste not, want not: nuclear fuel recycling

Prototype for the Integral Fast Reactor

"Down in the dumps" (New Scientist, 16/2/13, p 28) rather depressingly reveals that as far as radioactive nuclear waste is concerned, nothing has changed in decades and the repository route for dealing with nuclear waste may never be acceptable. One might say the thinking on waste disposal had vitrified!

Yet there is a solution available: PRISM reactors, based on the proven passively-safe Integral Fast Reactor. These can 'burn' plutonium (the UK has 100 tonnes), actinides, and depleted uranium (UK has 35,000 tonnes). IFRs are highly efficient and versatile, burning almost all their fuel. By contrast, a Light Water Reactor (e.g. Sizewell B) uses 0.65 per cent of the energy in the original uranium ore resulting in the radioactive waste, currently such a headache. The waste produced by IFRs is about 1/20th of that from an LWR. Its radioactivity within 200 years is about the same as mined uranium ore so no long-term repository is necessary.

David MacKay, chief scientist at the Department of Energy and Climate Change, says that there is enough energy in the UK's waste stockpile to power the country for more than 500 years. So why are we still obsessed with repositories? Why not use the 'waste' to make vast amounts of carbon-free electricity, simultaneously destroying almost all the 'nasties'?

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

Use 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.

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.

Out of sight but not out of mind: coal v. nuclear

House on fire: If your house was alight, beginning to burn up all your treasured possessions and imperil the lives of your family inside, you wouldn't attempt to douse it in gasoline, would you? Of course not. You'd use water in an attempt to quell the flames. Yet the gasoline approach seems to be government orthodoxy at present so far as the climate is concerned.

World on fire: Imagine you were an energy minister and you had been warned repeatedly by thorough science that adding more carbon emissions to the atmosphere was like chucking fuel on the fire of global warming. You can see that authorising more emissions would be guaranteeing life-threatening problems for next generation; our children. So you wouldn't then go ahead and approve a whole new set of electricity-generating plants based on burning that most polluting of fuels, coal, would you? Well actually, yes you would. For that is what many governments are either doing or are about to do. NASA climate scientist James Hansen has done his utmost to carry his no-more-coal-plants message to many governments, only to be ignored. The climate campers in Britain have done their best to publicise the stupidity of approving new coal-fired power stations, only to be throttled by heavyweight police action clearly authorised directly by a government set on the blinkered short-term view despite all their rhetoric about the need to get out of fossil fuels. It seems to be a case of "Lord make me chaste but not yet". Depressing, isn't it?

Energy for the future - renewables: Everyone knows what these are by now and campaigning NGOs like Greenpeace and Friends of the Earth have rightly put a lot into getting them adopted into energy plans (whilst vehemently rejecting nuclear). The difficulty with renewables is that they are unreliable. Wind turbines notoriously generate electricity not when we need it but when the wind blows. This means that, overall, they are only generating anything like their rated output for around 25-30% of the time. What happens for the other 70-75%? The hope is that, eventually, all the different forms of renewables (wind, solar, wave, PV, tides) will be linked together via a continent-wide supergrid and employ new means of energy storage. This may work but it is still decades down the line. So we're exhorted to reduce out carbon footprints... and a few of us make valiant attempts to do this. But it's not enough; nowhere near enough. The demand for electricity is bound to increase rapidly as more people travel by the electrically-powered vehicles -trains, buses, cars - which will be replacing hydrocarbon power: petrol/gasoline, diesel and LNG.

Energy for the future - nuclear: Environmentalists Mark Lynas and George Monbiot have both crossed the rubicon and, albeit reluctantly, adopted James Lovelock's position, rejected by most Greens and set out clearly in The Revenge of Gaia: we have to embrace nuclear power if we are to survive.

"I have now reached the point at which I no longer care whether or not the answer is nuclear. Let it happen - as long as its total emissions are taken into account..." George Monbiot in The Guardian

"Increased use of nuclear (an outright competitor to coal as a deliverer of baseload power) is essential to combat climate change..." Mark Lynas in New Statesman.

Why nuclear? It's that continuity problem; baseload. All grids, to be stable, need to have a good percentage of reliable, continuous generation to which other generating capacity, like pumped storage, can be added at peak times. Coal and nuclear stations are rather well suited to long periods of steady generation, just what renewables can't deliver.

Nuclear, the lesser of two evils? I know about the dangers of nuclear power. I've had a tour around the UK's Sellafield reprocessing facilities and seen the troubled vitrification plant where the most virulent highly active radioactive waste is made into glass blocks for storage. It's not nice stuff. But it's better than coal as Lovelock has made very clear. Going nuclear, which seems to be about to happen anyway, is the lesser of the two energy-producing evils.

No time to waste but let's put safety first: Governments need to get on with nuclear build now, not in 5 or 10 years time. 'Fourth generation' inherently safe reactors are not yet beyond prototypes. Even 'off-the-shelf' nuclear plants take some years to build so to make an impact on Big Coal, they have to be built right away instead of coal plants using existing designs. But no-one wants another Chernobyl. Oddly, there is one sure way of making nuclear safe that never seems to get a mention: build the plants - or at least the reactor and primary coolant circuits - underground. The advantages of doing this are pretty obvious when you think about it:

1. immune to military attack from the air containment unbreachable (given proper choice of ground conditions, hydrogeology and rock types) and so immune to attack from, say, a suicide bomber. Even major accidents would be better contained than anything above ground
   
2. no need ever to remove irradiated fuel assemblies.
   
3. when the reactor reaches the end of its operating lifetime, the whole facility could be sealed, complete with its spent fuel. Monitoring would be needed but because nothing is above ground, access would only be minimal
   
4. planning consent more likely to be straightforward since there wouldn't be much surface infrastructure to object to. Most of the usual public fears and objections wouldn't be serious issues
   

You can judge for yourself here.

Nuclear power: build plants underground

More nuclear power, like it or not: It seems likely that many of the world's states will soon begin to build many nuclear power stations; some for the first time and others - like the US - after ending a long-frozen programme. The reasons cited centre on climate change as it is true that, once operational, nuclear reactors are largely carbon-neutral. Furthermore, they have high energy density (very high power output from a very small space) and operate continuously over lengthy periods. All they do is provide a framework in which a controlled fission reaction within its uranium fuel heats up a primary coolant (circulating water or inert gas, contained under pressure). The super-hot coolant then heats water via a heat exchanger to raise steam to drive turbines to generate electric power. Renewables have low energy densities and operate intermittently regardless of the source of energy. At present, there is no viable way to store energy produced on a large enough scale to keep power available at all times; something we have come to expect. These factors, among others, make it inevitable that many new reactors will be built.

Damage limitation: It is not my purpose here to argue for or against nuclear power or discuss other issues like uranium mining and reserves. It's more of a damage-limitation exercise. Given that reactors will be built whether we like it or not, how can we ensure that they are as safe as possible? Mention the word 'nuclear' to most people, and words like Chernobyl, Hiroshima, missiles, nuclear waste, Windscale and Three Mile Island trip into the mind. Nuclear power has not, over the years, had a good press. And with good reason given its sinister association with bomb-making and several serious accidents. Yet it could easily be made much safer.

Nuclear power hazards: These are well known so I'll just briefly review them. The hazards all stem from the radiation produced by the primary heat-generating fission reaction, spent fuel rods, irradiated reactor assemblies, reprocessing (if any) and the resulting radionuclides which are created in the fissioning of uranium-235 atoms. The reactor is typically sealed in a primary containment vessel with radiation shielding surrounding it. These assemblies, in turn, are usually contained in a secondary reinforced concrete building which is designed to contain radiation products in the event of an accident in which the primary containment breaks down. [There was no secondary containment at Chernobyl and the results of the partial meltdown that followed the doomed 'experiment' are now grim history.]

• Loss of Coolant Accident (LOCA) in which the fuel rods, normally cooled by water or carbon dioxide gas, become so hot that they melt down (as at Chernobyl)
• Containment damage or breach due to warfare (bombing, missile, suicide using hijacked civil aircraft and so on), accident (aircraft crash), earthquake or climate change events (sea level rise, for example, since many existing plants are located by the sea which is used as a coolant in the secondary circuits)
• Hazards associated with transport of fuel assemblies to and from reactors (attacks, hijacking, accidents)
• Storage of irradiated fuel (attacks, leaks, accidents) in cooling ponds or air-cooled stores
• Reprocessing - the fuel route chosen by the UK and France in particular - which yields highly radioactive acid liquid wastes with potential for explosion in poorly-maintained facilities. Reprocessing notoriously is intended to yield other fissionable products such as plutonium metal, the source for atomic bomb-making and trigger for fusion (hydrogen) bombs. Plutonium, along with enriched uranium (also used for atomic bomb-making), has been repeatedly stolen from former USSR facilities and most of it not tracked down
• Decommissioning costs high and defunct installations will require monitoring and access protection for a century or more

What happens to the long-lived radioactive wastes? The best option at present - far from perfect - is monitored deep burial as vitrified blocks which must be protected from corrosive circulating groundwaters. Unprocessed irradiated fuel rods will likewise need to be stored deep underground (e.g. Yucca Mountain). Radioactive elements such as plutonium-239 in spent fuel will remain hazardous to living things for hundreds of thousands of years.

Scary list, isn't it?

And now, the answer? Almost all of these nuclear hazards become significantly reduced when you factor in a new possibility to the construction equation. If they must be built, why not build these facilities underground? To give you some idea of the relative sizes of the excavations needed, take a look at this drawing I made many years ago for UK examples.


On the left, in my drawing, is a vertical section of the Sizewell B reactor and containment building (click for full size image). On the lower right is an equivalent section through the Dinorwig pumped storage hydropower station, located deep inside a mountain in Snowdonia, beneath defunct slate quarries. For good measure, I added (top right) an as-yet-unbuilt example of another reactor design, a high temperature gas reactor. The point of all is that these engineered structures are all at the same scale: see scale bar.

What's even more important is the size of the Sizewell reactor vessel in relation to everything else. It's small without its containment building. And it wouldn't need such a building underground because being located underground is far better containment than anything that could be built on the surface.

Safety underground: the advantages

• immune to military attack from the air
• containment unbreachable (given proper choice of ground conditions, hydrogeology and rock types) and so immune to attack from, say, a suicide bomber. Even major LOCAs would be better contained than anything above ground
• no need ever to remove irradiated fuel assemblies. When the reactor reaches the end of its operating lifetime, the whole facility could be sealed, complete with its spent fuel. Monitoring would be needed but because nothing is above ground, access would only be minimal
• planning consent more likely to be straightforward since there wouldn't be much surface infrastructure to object to. Most of the usual public fears and objections wouldn't be serious issues

Disadvantages: is there a flip side?

• 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. Anyway, what price security and safety?
• Location: Finding suitable underground conditions, especially in flatter rainy areas with fast-moving groundwater circulation, could be a problem. The ideal would be mountain areas with relatively low rainfall.
• Cooling: Like any steam-driven turbines, cool water is needed both for raising steam and for condensing it. There's no reason for the turbine and cooling systems to be located underground since these aren't in contact with radioactive parts of the circuit

A safe way forward: I've set out what seems to me an obvious way forward for nuclear power, if we are to have much more nuclear electricity as looks certain. (France, by the way, already generates 75% of its electricity this way - but above ground). If you, the reader, agree that making it mandatory to locate future nuclear plants underground is worthy of consideration, please help begin a real debate by contacting your government representative and, perhaps, your country's nuclear generating industry. The onus is on the industry to explain why underground containment is a bad idea, not a good one. If it is a good one, let them start digging!