A Major Application for the New and Old Nuclear Power Plants - 2022

Nuclear Power Industry

Partanen reported in mid January 2022 that nuclear reactors produce heat. While we have used this heat to boil water into steam and then make electricity with that steam in a turbine, we can also use the heat for many other things. And we do use a lot of heat, as roughly half of all energy use is used as direct heat, while a fifth is electricity and roughly a quarter is used as liquid transportation fuels. So, if we globally use some 27,000 terawatt hours of electricity, we use some 60,000+ terawatt hours of heat. That is a very large market.

As an energy carrier, heat is different from electricity in many ways. It needs to be produced locally, because transporting heat is much harder and more expensive than electricity. It can be extremely hot steam for an industrial process, or warm water for household heating, or anything in between. And it often needs to be delivered on demand, very reliably. Even the demand profile can be different, as winter demand for district heating can be an order of magnitude larger than summer demand (when its used mainly for providing hot water).

The enormous heat market is one of the most promising applications for nuclear reactors, both old and new, big and small. District heating is something we have already done at small scale for decades. The latest news comes from China, where the brand new AP1000 reactors are now also supplying nearby towns with district heating, as well as some older reactors used for similar purpose at the Qinshan Nuclear Station. China is also building dedicated, smaller district heating reactors.

As most district heating networks are relatively small, in the hundreds of megawatts range, one or more small nuclear reactors (SMR) would be a good solution. Direct heat only needs to be around 100 C, so it can be made very efficiently with combined heat and power (CHP). With CHP, some of the lower temperature steam is taken from the low-pressure turbine and directed to the heating network. A bit of electricity production is lost, maybe 5%. However a lot of usable heat is recovered. This can bring the total efficiency of the plant to well over 80%, compared to 35-40% with electricity production only. The overall economics can be extremely good.

Heat is economically one of the most promising uses for small nuclear reactors at the moment. This is because of the fundamentals: nuclear reactors produce heat. So if we can make nuclear electricity at a levelized cost of, say, $60/MWh, it means that the cost of heat would be roughly one third of that, or $20/MWh. Compared to renewables like wind and solar, they only produce direct electricity. While this is valuable for cases that use electricity, if it needs to be turned into (reliable) high quality heat, the price will be higher than the cost of the electricity produced. This is why it makes a lot of sense to produce heat with nuclear. It’s a killer app for nuclear reactors, and something that can’t often be done reliably and cost-effectively with anything else. (Except fossil fuels, that is.)

There are even design concepts that only heat water to 100° C, suitable for district heating or desalination purposes but not for electricity production. And while normal light water reactors produce steam that is below 300° C, many advanced reactor designs, such as molten salt or gas cooled reactors, can reach much higher temperatures of 600°+ C. This opens up a host of industrial applications and processes that can be supplied, and decarbonized, with nuclear heat.

What is holding us back then? Mainly it is regulation and legislation that has been written for large reactors producing electricity in the middle of nowhere. This needs to change so we can fully utilize the potential of small nuclear reactors in replacing fossil fuels in heat production and take a big step towards a truly carbon neutral society.