Rethinking Nuclear Power

A renewable energy fan giving nuclear power a second thought.

After several exchanges with nuclear fans on twitter, and reading various articles, I am slowly changing my stance on nuclear power.

Let me cover some different aspect of nuclear power which has made me reconsider my rather hostile view of nuclear power.

Storage of Nuclear Waste

Storage of nuclear waste has been discussed for decades without us seemingly getting close to any long term solution. However a fairly decent and cheap solution already exists and is being used called Dry cask storage which looks something like what you see below:

These are several layers of metal and concrete providing radioactive shielding and they are strong enough to withstand a missile hit. They are typically license for storage for 20 year periods. Government inspection will then decide whether they can store another 20 years. In principle these could last up to 120 years.

There are a lot of these facilities around the world and apparently no leaks has happened from these despite having been used since the 1980s all over the world.

Ideally we get long term storage, but if not we can just keep making these dry cask containers and move nuclear waste over to new casks when the old ones are no good. Not my ideal solution but it works.

This is one part of the storage situation. But an equally important part is to understand that there simply isn’t all that much nuclear waste to store. world-nuclear.org provides more details:

To the end of 2013, a total of about 370,000 tonnes of used fuel had been discharged from reactors worldwide, with about one-third of this (120,000 t) having been reprocessed

This may sound like a lot but keep in mind this is from all reactors since nuclear power began. The remaining 250,000 tonnes would fit inside about 10 football fields 10 meters deep.

But it gets better. It turns out that most of this waste isn’t all that bad:

97% of the waste produced is classified as low- or intermediate-level waste (LLW or ILW). Such waste has been widely disposed of in near-surface repositories for many years. In France, where fuel is reprocessed, just 0.2% of all radioactive waste by volume is classified as high-level waste (HLW).

There are a few things to be aware of regarding nuclear waste and that is the relationship between half-life and radioactivity. We are frequently scared about radioactive waste with really long half-life, but the thing is that anything with a very long half-life, isn’t very radioactive.

That is because radiation is only emitted when atoms decay. If they are slow to decay, then the radiation will also be small. Hence the really radioactive material quickly decays to less radioactive material.

Most nuclear waste produced is hazardous, due to its radioactivity, for only a few tens of years and is routinely disposed of in near-surface disposal facilities (see above). Only a small volume of nuclear waste (~3% of the total volume) is long-lived and highly radioactive and requires isolation from the environment for many thousands of years.

Thus bottom line is that radioactive waste simply is not as big of a problem as I first anticipated. The volume is simply quite small. E.g. if you compare with waste from solar or wind power it is much smaller. And these are not entirely safe either.

It does not mean I am entirely won over. I think we really should be seeing more long term storage facilities coming online, but some are actually already created.

Safety of Nuclear Reactors

We have experienced both Chernobyl and Fukushima. What prevents something like this from happening again? Chernobyl was a trauma I can still remember vividly from my childhood. Despite living far away in Norway we had to stop eating reindeer meat due to the radioactive fallout.

We where told this kind of accident could not happen again, because Western reactors where much safer, but then Fukushima happened. Now this was not as bad as Chernobyl. 20,000 died from the Tsunami but nobody from the reactor accident as far as I know.

However the cleanup costs from the reactor is potentially running up to 660 billion dollars. Which is an insane cost. Is nuclear power really worth it with such outcomes?

I want to take a balanced view here. Many will people like say Michael Shellenberger, will claim both these accidents proved that Nuclear power is awesome by pointing to the the low number of people who died. Personally I find that reckless.

Both accidents caused a profound psychological trauma in the population, especially Chernobyl, which we should not forget. As with many nuclear accidents government and companies have covered up and lied. It is easy to mock common people for not properly understanding the dangers of radiation, but I believe common people have good reason to be skeptical. They have been lied to a lot.

Still I have to be reasonable. There are profound differences in how safe different reactor designs are. Both Chernobyl and Fukushima relied on active safety systems for doing things like pumping cooling water. When power fails everything can go haywire in such a system.

But there are a number of systems that are based on passive safety and there are reactors which simply cannot meltdown by the laws of physics.

For instance the Canadian CANDU reactors which is a pressurized heavy water reactor has extra protection from meltdown because it uses low grade Uranium which does not continue chain reaction in regular water (light water).

Another benefit is that CANDU can run on Thorium rather than Uranium. This protects against meltdowns and produce less radioactive waste.

Modern Russian reactors like VVER-1200 contain a host of active and passive safety features which did not exist in the Chernobyl reactor. This is an important reactor to study as it is being widely exported and built in the world.

Unlike Chernobyl it has a containment and missile shield around the reactor core.

Other new safety systems include aircraft crash protection, hydrogen recombiners, and a core catcher to contain the molten reactor core in the event of a severe accident.[15][20][27] The core catcher will be deployed in the Rooppur Nuclear Power Plant and El Dabaa Nuclear Power Plant.

But perhaps more importantly unlike the graphite moderated reactor type RBMK, used in Chernobyl if cooling fails the chain reaction is slowed down. Nuclear reactors need a moderator to keep the chain reactor going. In the VVER-1200 design that is the cooling water, and if cooling water stops flowing it also reduces reaction. This is an important safety feature.

While these are quite safe and good reactors. Problems can still arise. Fukushima e.g. shut down their reactors but this still did not hinder an accident. The residual heat got so hot that it produced hydrogen that blew a hole in the reactor confinement. Without enough cooling the fuel melted through the floor.

VVER-1200 can catch hydrogen so that can help.

So while large modern reactors are a lot safer than Chernobyl and Fukushima there are still many things which could go wrong, even if they consequences are likely not as catastrophic.

As a fan of renewable energy, these are not the reactor types I would champion or favor. Instead I think would prefer what we call Small Modular Reactors (SMR). So let us look closer at them and their safety features.

Small Modular Reactors (SMR)

SMR reactors are being designed by a number of companies:

  • Ultra Safe Nuclear making the Micro Modular Reactor (MMR) in Seattle, Washington.
  • NuScale Power making the NuScale Power Module in Portland.
  • Moltex Stable Salt Reactor (SSR) based in the UK.
  • Seaborg Compact Molten Salt Reactor based in Copenhagen, Denmark.

Actually the list of companies busy doing this is a lot longer. What differentiates a lot of these Small Modular Rectors from the big ones is that they are much simpler and are based almost entirely around passive safety.

Instead of complex monitoring systems, when they fail, they will typically shut down and cool down by themselves. No pumps or active features are needed. Heat is dissipated passively to the surroundings.

Many of these have what we call “walk away safety,” meaning the power plant operators can just walk out and the whole thing will shut down itself gracefully.

Large reactors tend to keep water under high pressure. They are inherently unstable systems which need to be kept safe with a lot of engineering. As we saw with Fukushima we got dangers with water which can turn into hydrogen and make stuff explode.

In many of these SMR designs this isn’t even possible, because here is no water. There isn’t anything that can turn into radioactive gasses and clouds that can drift far away. Instead radioactive waste is kept on site.

The second advantage I see is that, because these reactors are really small, should anything against all odds still go wrong, then the consequences are significantly smaller in scale.

Economics of Nuclear Reactors

For me safety has never been the sole reason to oppose nuclear power. I have know for some time that modern reactors are fairly safe.

My arguments against nuclear power has basically been this:

  1. Nuclear power is very expensive, so why pursue it when renewable energy is considerably cheaper and safer?
  2. Build times are extremely long and cost overruns common.
  3. They make a poor match for renewable energy. Nuclear power traditionally cannot ramp up and down power output quickly. Gas power plants can.

My thinking has been that we pair renewable energy with gas power plants because they are fairly cheap and quick to build. They can ramp up power production quickly when needed, e.g. when the wind dies down or there are clouds.

Yes I know that releases CO2 but my idea has been that as we build overcapacity of renewables this will be for short periods. Over time storage solutions will be able to replace gas power plants or we may be able to synthesize clean gas. Alternatively we could burn metal powder in coal plants. Yes this sounds crazy but you can actually use metal as an energy carrier. You spend clean energy producing metal powder and then you burn it when you need power.

I still think this is a fairly good strategy, but here are reasons I am more open to Nuclear energy: Companies such as Moltex and TerraPower plan reactors which use thermal storage. Basically hot molten salt is stored.

One has to remember that a Nuclear power plant is basically a steam engine. Instead of using coal to boil water and drive a turbine, one uses uranium to heat water.

With the molten salt reactor one uses molten salt instead to heath up water and create steam. The point with the molten salt storage is that it allows one to ramp up the power produced by the steam turbines when needed.

The Moltex reactor itself can generate 300 MW, but it is connected to a 900 MW boiler and turbine. Thus by drawing from the molten salt one can output 900 MW for 8 hours, or alternatively 600 MW for 12 hours.

Why is this a big deal? Nuclear power tends to be more expensive than renewables. So say your town needs 900 MW of continuous power. Instead of building 3 reactors, you could build one making 300 MW. The remaining 600 MW is provided by a combination of wind and solar power.

If the wind stops blowing and the sun isn’t shining we aren’t screwed. Instead our nuclear reactor’s steam turbine is able to keep outputting the full 900 MW needed to power the town for a whole 8 hours. Within that time the wind will get online again.

The wind may come and go in that period, but that just means the period in which the nuclear steam turbine can keep going is just extended as power is saved.

Conclusion: Let’s be Friends!

With the approach described here Nuclear and Renewable energy can be partners instead of enemies. Nuclear energy solutions like Moltex or TerraPower can work as batteries. When the wind is blowing, the nuclear reactors are primarily heating up its large molten salt storage.

Discharging the “battery” is basically to drain heath to drive the steam turbines.

But fellow renewable fans may object and say “What about batteries? Isn’t that a better solution?”

And indeed I actually do think it is highly probably that before we see any of these SMR designs grid scale batteries may become affordable.

However the point is that we don’t really know the future, and Nuclear power is gaining a lot of adherents. We should not be wasting energy opposing this movement which has the same goals as fans of renewable energy and batteries.

Instead I think it is important that if Nuclear energy gains momentum that we can push for the kind of Nuclear reactor solutions which complement and help renewable energy while at the same time offering safety which we can live with.

At the moment people like Michael Shellenberger is bashing renewable energy and making it look as if we have to make a choice between renewable or nuclear. This kind of dirty fight between nuclear and renewables can only benefit the fossil fuel industry. It would be better to stand united and see these power sources as having potential to complement each other:

  • Renewable energy lowering the overall cost of power.
  • Nuclear power offering stability in power generation.

Written by

Geek dad, living in Oslo, Norway with passion for UX, Julia programming, science, teaching, reading and writing.

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