“Nuclear power would not be worse for our water security than coal. It would be approximately neutral, because the consumption is basically the same. But might it actually be better?”
This post is inspired by a message that got back to me from my Mum, that a relative of mine (who shall remain nameless. Hi Auntie Jackie!) will “never agree with me because nuclear power plants use so much water”.
It’s an important point. In Australia, we can never take water for granted. The most recent and very severe drought pushed water supplies to the brink around the country. Investing heavily in a new power source that would stretch those supplies even more would seem a risky thing to do.
So this question is worth examining. In the mix of Australian energy generation, would nuclear power be:
- Better for our water security?
- Worse for our water security?
- Neutral for our water security?
I’m going to answer that question by comparing it with coal fired power generation, which is the most prevalent form of generation in Australia, and the form I want to displace quickly with nuclear power.
To start the answer, it’s worth understanding a little about nuclear power generation. Basically, it’s a thermal electricity generation method. This means you have a heat source, you add water to create steam, draw the steam through a turbine to generate electricity, then condense the steam back to water and repeat the process. This is the way it works for coal, gas, nuclear, and concentrated solar thermal electricity generation. The principal difference among these methods is the heat source. Fossil fuel plants burn large amounts of fossil fuel to create the heat (producing large amounts of greenhouse gas and other pollution in the process). Concentrated solar thermal uses concentrated sunlight, (producing no direct pollution to speak of, but taking up a lot of space and unfortunately costing a lot of money). A nuclear plant uses a nuclear reaction for heat (producing a small amount of waste which is captured and stored). Aside from that, the basic mechanism doesn’t change.
So there is water being used in two ways. Firstly to create the steam. This water is pretty much in a closed system. It is turned to steam, run through the turbine, condensed back to water, and then recirculated. So that water consumption is not really of concern.
The second way is to provide the cooling for the condenser. The condenser is, simplistically speaking, a metal barrier on the far side of the turbine from where the steam is coming. By keeping it cool with water, a temperature gradient is created between the two ends of the turbine. This acts like a vacuum to suck the steam through the turbine at speed and create the electricity. This is where the water consumption occurs. The water that is used for cooling the condenser evaporates, which is what we see leaving the power plants chimneys as steam. Allowing for better and worse, older and newer designs, because the mechanism is the same whether the heat source is fossil, nuclear, or solar thermal, there is no substantial difference between the quantity of water consumed per unit of energy created; the same job needs to be done.
To that end, we have a partial answer to the question. Nuclear power would not be worse for our water security than coal. It would be approximately neutral, because the consumption is basically the same. But might it actually be better?
Water itself is not scarce. There is more water on this planet than we know what to do with. Fresh water on the other hand, is very, very scarce indeed. It’s less than 3% of the total water on the planet, and a good deal of that 3% is captured in ice. Come to Australia, especially the south, south west and south east, and that water scarcity is regularly on display. Fresh water is way more useful to us than sea water, for drinking, industry and agriculture. Our water security is determined by our supplies of fresh water. Provided we can tolerate some localised impacts (like brine discharge from desalination processes), we can use sea water to our heart’s content without worrying about water security.
So that’s another potential difference between the power sources that we need to understand; what type of water can be used for cooling: fresh water or sea water? The answer is less technical than you might think. It depends on where the plant is.
The 2.2 GW operations of the Loy Yang coal fired power plant consumes 60,000 tons of coal per day. There is no way of moving that much fuel economically. So where do you build the power plant? Next door to the mine. The only water that is available for cooling in the middle of Gippsland is fresh water. Lovely fresh water that could be used for human consumption, agriculture, or river health is instead evaporated in a coal fired power station. For Loy Yang, the quantity of fresh water it consumed in 2009 was 37 GL (Sustainability Report 2009); 14 GL from aquifers, 25 GL from the La Trobe River, and the remainder from the Maroondah Reservoir. Is that a lot? Well, in 2006 Melbourne as a whole consumed 369 GL of water. So the coal power station consumes approximately as much water as 360,000 people in a modern Australian city(1/10th the 2006 population of Melbourne). So yes, it’s a lot. You can repeat this exercise for the Hunter Valley coal region in NSW, or Queensland or South Australia’s coal generation centres. [Author’s note: I have since learned and shown in another post that South Australia does in fact transport a very large amount of coal a very long way and use sea water for cooling. It merely requires the longest coal train in the world…]
Uranium on the other hand, is a super dense energy source. The quantity of fuel required for a nuclear plant is miniscule. Some modern designs are fuelled up, started, and refuelled 4.5 years later. This is a big advantage. It means you can put the plant more or less wherever you want, such as closer to the centres of demand, which reduces the wastage of electricity that is lost in the transmission lines. In Australia, it also means we can put them in reasonable proximity to the ocean, with some sensible buffer from storm surge and tsunami, and cool the condensers using pumped sea water.
The implication for water security is suddenly clear. Displacing all coal fired power stations for nuclear power stations would lead to a dramatic improvement in Australia’s water security by freeing up huge quantities of scarce fresh water for more beneficial uses. It is yet one more criteria in which nuclear trounces coal for sustainability. So thanks for the question Jackie. Australians need to know the answer.