Energy & Climate Change
Fennovoima-ydinvoima_Pienreaktorit

Smaller reactors have several potential uses. For example, they can supply warm water for district heating of a city or even desalinate sea water. Photo by iStock

What about the small reactors?

When people think of nuclear power, they usually think of enormous structures. Few know that there are much more small reactors around than there are big ones.

Nuclear power started small. The first motivation was military use. The first reactors built during Second World War and after it were mainly meant to make plutonium for the military. The famous Atoms for Peace -speech by President Dwight D. Eisenhower kickstarted the use of civilian nuclear energy for electricity generation in earnest. Military continued its own nuclear path, however, as a small reactor is a splendid power source for an aircraft carrier or a submarine. There have been hundreds of small reactors in use throughout history.

Larger reactors became more common in the 1980s and 1990s, as these plants enjoy the benefits of scale, enabling cheaper electricity production. But for the last ten years or so, small reactors have seen a resurgence of interest.

How small is “small”?

As a rough guide, small reactors can be around one tenth the size of modern large reactors, although there is a lot of variance. The VVER1200 that will be built at Pyhäjoki delivers power at 1,200 megawatts, while the definition of a small reactor is usually between 50 to 300 megawatts of power. Hanhikivi 1 will supply electricity for up to one million Finns, while a small reactor might supply power (and perhaps also district heating) for a mid-sized Finnish city.

There are a lot of different technologies on offer, and they work for different things. “Light water” (LWR) is the most common and furthest in development. It is the same technology that large reactors are mostly based on, so there is a lot of expertise and supply chains already in place. Some of the other technologies include gas-cooled reactors, molten salt reactors and liquid metal cooled reactors.

There is a lot going on in the world of small reactors already.

Smaller size gives a reactor both advantages and disadvantages. Smaller reactors mean smaller investments, so getting funding for them might be easier. Smaller projects are also easier to manage than huge megaprojects. One can build and assemble reactors at a manufacturing line more readily, which can decrease costs. Lower power level also means that they can be designed to have simpler and cheaper safety features than larger reactors. On the other hand, for example operating expenses can be relatively larger compared to large scale reactors. A small reactor might need a similar number of operators working at site as a larger reactor despite its smaller size.

The strict regulations of nuclear industry apply both for small and large reactors. It takes a significant amount of money, work and expertise just to be a licenced nuclear operator, even if one would only operate one tiny reactor. Many countries today lack proper legislation and safety regulations for small nuclear reactors and new uses for nuclear energy, which can include for example supplying district heating or industrial process steam. No matter how safe a reactor is, one might not be able to build and operate one if there are no evaluation methods, criteria or regulations in existence.

A large need for small reactors

There are a lot of new potential uses for smaller reactor design, as they are more suitably sized for many use-cases. They can supply warm water for district heating of a city or high temperature steam for industrial processes, or even desalinate sea water in the water-constrained parts of the world. All of these need to be supplied locally and only demand tens or perhaps a few hundred of megawatts of energy supply.

Small reactors are often designed to be flexible as well, which makes them suitable for grids that have a lot of variable wind and solar production. They can also be used to produce clean hydrogen.

Of course, small reactors can be used to produce “normal” clean and reliable electricity. Especially in developing countries, where the grid infrastructure is growing fast, smaller additions to the grid can be easier to manage and invest in.

When and from where can you buy a small reactor?

There is a lot going on in the world of small reactors already. Perhaps the most familiar for Finns is the Russian barge Akademik Lomonosov that was towed on the Baltic Sea a while ago. It has two small KLT-40 reactors installed on it, which are modified designs of an icebreaker power source.

China is preparing to start a bit more exotic helium cooled pebble-bed reactor during 2020. It can produce higher temperatures, and China is thinking of using it to replace the coal boilers in current coal power stations. This would cut both particulate pollution and carbon dioxide emissions. China is also designing and constructing simple, pool-type district heating reactors to heat their large cities.

There are over a hundred start-ups in North America that are developing new small reactors or things related to new kinds of nuclear. The ones furthest along the path, such as NuScale from the US, are already finishing their licencing process. The first small reactors are estimated to start up near the end of 2020s.

Europe has also woken up. The Danish Seaborg is developing a small molten salt reactor. LeadCold in Sweden is developing their metal-cooled SEALER. And in Great Britain, Rolls Royce has a smallish “UK SMR” under works, with France also having their own design, called “Nuward” in conceptual design.

In Finland, VTT Technical Research Centre of Finland Ltd started their own district heating reactor design project in early 2020. We might yet see the first small reactor under construction in Finland in the 2020s.

You can read more about small reactors and where to use them from this pdf.

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