The United Nations Climate Change Conference (COP26) in Glasgow has heralded a turning point for nuclear energy. Recent extreme weather events provided a backdrop for the greatest ever appreciation of the urgency to transition to low carbon energy sources, to avoid catastrophic climate change. The current favourite low carbon electricity generation mode is via the renewables. These may be becoming somewhat jaded. There is by now a lot of experience with the renewables. There are many drawbacks. Their load factor is of the order of 30%, but this average value masks the many fluctuations that range from 0% - 100%. Backup, storage or handover must provide for a net 100% alternative solution, even if it would only be rarely used at the 100% scale. Those alternatives need to be kept in full readiness, permanently. One must essentially double up on capacity. The transmission grid dependence is therefore very high, usually also requiring a different grid topology from what is currently established. In addition, the variability stresses the rest of the system that has to compensate. Substantial renewable penetration therefore has ever increasing hidden costs. Choices are few. Hydro may not be available, fossil fuels must be phased out. The greenest of the fossil fuels, natural gas, has an unreliable and wildly fluctuating price. It also requires considerable infrastructure for delivery and storage. It is therefore not surprising that COP26 has seen subtle changes in the perceived role of nuclear, towards achieving “net zero”.

Some examples are the declaration from China that it will build out its nuclear generation capacity with about 10 new reactors per year for 15 years. The important point here is not only the size of the nuclear build, but the claimed cost, at about $3000/kW. This is achieved by lower financing costs. This brings nuclear into the affordability zone, as compared to the previously more palatable alternatives. This is especially interesting considering one also buys reliable, dispatchable, baseload generation capacity. One also buys three times the load factor of renewables and three times the lifetime of the plant. Add to this the growing hype around Small Modular Reactors (SMRs). The plan there is to lower costs and shorten delivery times essentially by mass production in factories, with shorter installation times. The SMRs have similar low power outputs to renewable farms. So, like the renewables, they can also be placed where local grid loads are relatively small, due to poor grid establishment or penetration (like in Africa). So when price, delivery time and applicability are now comparable, the drawbacks of renewables compared to the advantages of nuclear, in dispatchability, security of supply and grid stability, now give nuclear the edge.

Of course, once you can claim that nuclear energy is affordable and applicable, the renewables lobby will introduce the three usual anti-nuclear arguments of last resort: proliferation, safety and waste. A modern nuclear reactor embedded in a mature regulatory environment addresses these issues to black swan standards. The intention in the remainder of the article is not to enter this debate, where clearly, the nuclear lobby are satisfied these three aspects are well covered. Instead, a new element will be discussed. It is the element of scaling. This concept comes from understanding Mathematics, Physics and Engineering, as opposed to perceptions. Basically, we must put numbers to all parameters, and visualise the scaling of these numbers to the full implementation. If imagining these numbers and units is not easy, we can use paradigms which illuminate the matter very clearly. What follows is very brief, and can’t do justice to the subject here; rather, a book is required.
A first example is that the energy content per atom for nuclear as compared to fossil fuel is 50 million times higher. That’s just how nature is. Chemical energy densities almost vanish compared to nuclear energy densities. Uranium is heavier than carbon, and also, needs to be enriched. So a 10g fuel pellet has the electricity generation capacity equivalence of between 1 – 20 tons of coal (normal or breeder reactor). This has consequences. You can build a nuclear reactor that you refuel once every ten years, whereas keeping a coal plant satisfied with fuel is a logistical nightmare. You are able to transport the small amount of nuclear fuel to the reactor, which you can locate wherever you like, rather than being forced to locate the coal plant right at the coal field. Your waste is a hundred thousand times less. Your relative operating costs are minimal, rather than being dominated by your fuel costs. When the cost of gas triples, like it is doing now, your electricity costs scale significantly, and you have to have a cold winter.

If the cost of uranium were that volatile, it would lead only to a fractional increase in the cost of electricity. Nuclear energy represents an extreme amongst the current commercially available modalities which is hugely abundant and very concentrated, by many orders of magnitude, compared to any of the alternatives. For example, it’s now much discussed in the news that Australia recently preferred a nuclear- powered submarine to a diesel one. Now we know why. If your life is at stake, it helps you make your choices with evidence-based reasoning, respecting numbers.

This energy scaling comparison maps roughly to a battery too, as both batteries and fossil fuels are based on transforming chemical energy to electricity. This somewhat puts batteries into perspective when talking about energy. They represent a vanishingly low energy density storage device, once you consider the energy hungriness of a city. In energy requirement terms, and energy storage options, we should not confuse our phone, where the battery is the biggest single item, with a city.

Now, if we consider other energy source modalities, such as hydro, wind and solar, we can’t do the same comparison, as these are not material-based sources of energy. Instead, let’s find another metric. The land use of a 1GW nuclear plant is about 3 km². By comparison, for the equivalent average output, for a wind plant its nearly 800 km² and for a solar plant its 150 km². Hydro is better, but still has a large footprint, and its unfortunately not everywhere available. Africa is not Norway. Indeed wind and solar also harvest a very diffuse source of energy, as compared to nuclear. As such, raw material requirements of the renewables are thousands of times more than for nuclear energy. If all countries should by democracy have the per capita energy generation capacity of a well-developed country, for example, if Africa should be equivalent to the USA in this respect, it would require 3400 GW generation, 20 times more than it has now. If this were to be provided by renewable energy, this is an enormous budget in the raw materials required for the construction of these very diffuse energy harvesting devices. Scaling the demand for raw materials to the requirements is very sobering. It is predicted we would need to start mining the coastal shelves of continents.

Let’s suppose we do indeed have this enormous penetration of renewables in SA. We will need backup. Suppose Koeberg next to Cape Town were replaced with a solar PV farm. Then suppose we wanted to store its 2GW energy production rate capacity for 10 hours, so that we could plan for a day of no sun. A power of 2 GW for a time of 10 hours is an energy content of 20 GWh. In principle, the battery backup is vulnerable to terrorist attack. If nuclear must be safe, black swan safe, then so must batteries. To understand the enormity of 20GWh, this equates to the energy content of a bomb just over one times the size of the Hiroshima explosion of 15 kilotons of TNT. The purpose here is not to be alarmist. It is to help you, the reader, understand how to visualise a large amount of stored energy, the amount of energy needed to power a city for a day. We want to illustrate that a city requires a very large amount of energy per day. It does not make sense to store this energy. Storing large amounts of energy is an accident waiting to happen. You can’t be against nuclear energy because of safety considerations, and then store a Hiroshima-sized bomb next to your city each night. What will happen when the city grows to 10 times its size, and the poor, become middle class? This is why utility engineers talk of load following. One makes electricity at the rate required. If you need less electrical energy, produce less, if you need more, produce more. This discussion helps one to understand the concepts ‘baseload’ and ‘dispatchable’. Nuclear is a baseload supply and its dispatchable. The renewables are not.

In this article, we noted the new interest in nuclear following COP26. Then we noted that nuclear exhibits the highest energy density source, by many orders of magnitude. We looked at the positive consequences of this. Energy is always going to scale, upwards. Our solutions must cope with scaling.