Why small modular reactors do not exist – history gives the answer.

David Toke, Jan 15, 2025, https://davidtoke.substack.com/p/why-small-modular-reactors-do-not

In recent years we have seen many stories with an upbeat message about small modular reactors (SMRs) and ‘races’ to develop them. But in fact, the concept of SMR is a bogus term that tries to give the impression that something new in nuclear power is afoot. It most certainly is not. In fact what are called SMRs cannot easily be distinguished from nuclear power plants that were built in the 1940s to 1960s, long before the SMR notion was invented. The term SMR does not exist as a useful definable concept.

Even examples of new so-called SMRs are practically non-existent around the world when it comes to operating projects. But there has been a tremendous amount of hype. Indeed the hype seems to grow in inverse proportion to the lack of any projects being completed. First, a definition:

According to the International Atomic Energy Agency:

‘Small modular reactors (SMRs) are advanced nuclear reactors that have a power capacity of up to 300 MW(e) per unit, which is about one-third of the generating capacity of traditional nuclear power reactors. SMRs, which can produce a large amount of low-carbon electricity, are:

• Small – physically a fraction of the size of a conventional nuclear power reactor.
• Modular – making it possible for systems and components to be factory-assembled and transported as a unit to a location for installation.
• Reactors – harnessing nuclear fission to generate heat to produce energy.’ (Ref: see HERE

Yet the problem with this definition is that none of this represents anything new i.e. something that has not been done long ago. The term ‘advanced’ is vague and does not seem to exclude approaches that have been tried before. The notion of modular is even more misleading in practice. That is because having smaller reactors reduces the scope for factory production of components.

There are fewer economies of scale for small reactors compared to making parts for larger-scale reactors (which require more parts of a particular type). The word ‘reactor’ is not new. So what’s new? Certainly nothing, in my view, to warrant the ascription of ‘fourth generation’ nuclear designs that these so-called SMR proposals have often been given.

In practice, even projects that are called SMRs are very, very few in operation around the world. There are very few even under construction, and the ones that are seem to be taking a long time to build. That is, according to the International Atomic Energy Agency. So how can we explain this apparent contrast between, as the media stories put it ‘races’ to develop SMRs, and reality?

The problems with the concept of SMRs can be explained by reference to the historical development of nuclear power. In the 1950s and 1960s, the nuclear industry found that the (then) existing designs of small(er) reactors, what is now called SMRs, were uneconomic compared to larger reactors. As a result, the industry developed larger reactor types. The larger reactors, of course, have had very big construction problems and costs. However, this should not obscure the fact that in comparison the smaller reactors were even worse. Let us look at some of the reactor history in terms of size.

Originally, after WW2, the first electricity-generating nuclear reactors were designed for nuclear submarines. These pressurised water reactors (PWRs) range from a few MWe to over 100MWe for the largest submarines today. I would say that they are the original small nuclear reactors. Indeed here it gets a bit confusing. Why aren’t these submarine reactors called small modular reactors? Essentially, I think, because they do not fit into the current narrative which tries to give the impression that there is a new type of advanced reactor called an SMR.

Small reactors were then designed, starting in the 1950s, for land-based operations to supply mainstream electricity grids. Then design sizes increased and PWRs became the dominant technology throughout the world. Chart 1 shows how nuclear reactor sizes have increased over the decades in the case of the UK. You can see how the average design size for reactors increased from around 100 MW in the 1950s, to 400 MW in the 1960s, over 500 MW in the 1970s, and then to over 1000MW since the 1980s.

There is a very good reason that design sizes increased from the 1950s onwards. Indeed this reason seems to have been mostly overlooked in the blizzard of press releases about small modular reactors. It is all to do with the economies of scale.

There was a (at the time, well-regarded) book published in 1978 by Bupp and Derian (see later reference). This summed up the reason why the rush of ordering nuclear reactors in the USA came to an end in the 1970s. It has great relevance to the issue of small reactors today. It is all to do with the size and cost and also the safety requirements of reactors. They said:

‘In 1955 a 180 MW light water reactor design called for more than 30 tons of structural steel and about one-third of a cubic yard of concrete per MW. By 1965 a much larger plant of about 550MW required less than half as much of these materials per megawatt of capacity. These efficiencies reflect classic ‘economies of scale’. Then, in the late 1960s, the trend reversed. Larger light water plants began to require more, not less, structural materials per unit of capacity; by 1975, the steel and concrete needed per megawatt for 1,200 MW plant approximately equaled the 1960 requirement for a 200-300 MW design. This reversal was a direct consequence of stricter safety and environmental protection requirements laid down during this period. More stringent safety requirements meant thicker concrete walls.’1

So, essentially, nuclear power plants became bigger because of the drive for economies of scale. A big reason why nuclear power did not continue to become cheaper was because, by the 1970s, demands for stricter safety precautions were being translated into regulations. This meant that the progress in reduced costs had been reversed. More recent (so-called Generation 3) nuclear designs have been based on the hope that ever-bigger reactors with better safety designs would once again pave the way to cheaper nuclear reactors. It has not, of course, happened.

In other words, small modular reactors will not produce cheaper outcomes. Arguing for such a proposition flies in the face of history, not to mention basic engineering economic theory. That is, of course, if we assume that small reactors have to deliver the same safety levels as big reactors. Yet it is difficult to see the regulators scrapping the main safety requirements accumulated since the 1960s just for small nuclear reactors. Why would they? Having a much larger number of smaller reactors would increase the risk of there being a serious accident at one of them.

Progress in constructing new small reactors

This is extremely thin. Only two operating so-called SMRs were identified by the International Atomic Energy Agency in 2024, and there are very few others (three in fact) listed as under construction (see HERE page 13). So far as I can see all are very well supported by direct state or research demonstration funds. That is they are nowhere near becoming commercial propositions able to survive on the promise of privately funded bank loans and equity investment.

Of the two so-called SMR plants in operation, one is a 200 MWe reactor built in China (See HERE) – which as you can see in Chart 1 is actually rather bigger than the average reactor size in the UK designed in the 1950s. Not only that, but it took a total of 12 years to construct (see HERE). The other operational project is based on a ship in Russia. This could be described as a variation on a submarine reactor built to support a very niche market, with financing details not available.

One of the three of the three so-called SMRs under construction is being built in Argentina (and whose funding stream is threatened by Government cutbacks). This has a 32MWe reactor and is a variant of a PWR. Construction began in 2014. This is oriented mainly not to electricity production but to an extremely limited market in radioactive products.

The second is a 300 MWe ‘fast’ reactor being built in Russia. Fast reactors are certainly not new. They have been tried in various countries before (including the UK) and have not been commercially successful.

A third, much publicised, development is the 150 MWe Kairos reactor in the USA. This power plant is sited at East Tennessee Technology Park. The US Government’s Department of Energy is supporting the construction of the project. It is a ‘pebble’ bed high temperature, gas cooled reactor. Although called ‘Advanced’ pebble bed reactors were first mooted in the 1940s and have been tried and discontinued before.

Indeed, as Steve Thomas has said about the notion of ‘Advanced’ reactors (see HERE) ‘The advanced designs are not new. For example, sodium cooled fast reactors and high temperature reactors were built as prototypes in the 1950s and 1960s but successive attempts to build demonstration plants have been short-lived failures. It is hard to see why these technologies should now succeed given their poor record. Other designs have been talked about for decades but have not even been built as prototype power reactors – so again it is hard to see why the problems that prevented their deployment to date will be overcome.’

Other variants, including thorium-based plants are proposed (most recently in China). On the one hand, all of these ideas have been tried before, but are being presented as ‘new’ developments. They have failed before. These warmed-up versions of previously tried technical nuclear fission variants do not solve nuclear power’s basic cost problems. These problems involve too much steel, and concrete and the need for unique, very expensive, types of parts and techniques that are too specialist to be sourced from standard industrial supply chains.

This (Kairos) project was made famous by an announcement from Google to buy power from it. However, beyond that, I have no information about how much money Google has actually spent on the project or indeed how much it has agreed to pay for the power the reactor will produce.

Indeed the Autumn of 2024 saw a flurry of announcements of support for so-called SMRs from ‘Tech Giants’. However, the terms of the financial support were generally vague. The announcements were made just prior to the General Election and seemed to respond to the rising hype about powerful AI. In a different blog post I analyse this AI over-hype, (see HERE).

Of course, we can all agree to buy power from people for a specified price by agreeing to PPAs. No commitment to part with money is necessarily required. Whether banks and equity investors are willing to lend money to the energy project in question on the basis of such PPAs is an entirely separate matter.

SMRs in the UK

There are no projects called SMRs operating in the UK. None are under construction and none are in the process of getting anywhere near construction starts. The UK Government for its part, amongst a fanfare of publicity about support for SMRs, promises an aim of ‘deploying a First-of-a-Kind SMR by the early 2030s’ (See HERE). Of course, as Chart 1 above implies, there used to be reactors that are small enough to fit the definition of ‘SMR’. They just weren’t called SMRs at the time.

Indeed, Rolls Royce, has, for several years been promoting their so-called small modular reactor (SMR) design. This is rather larger than a lot of past British nuclear power plants, albeit none still in operation. Their proposed (so-called) SMR design has gone up to 470MWe (See HERE). It uses PWR technology.

This proposed project is rather larger, for example than the 235 MW units which comprised Hinkley A nuclear power station. This power plant began construction in 1957, started generation in 1966, and stopped generating electricity to the grid in 1999. When construction of this project began such a nuclear power plant would have been called large, not small!

I do not understand the claims made by Rolls Royce for their ‘SMR’ to be called modular. The power plant has to be constructed on-site. As I have already stated I do not understand why there is more, or even as much, scope for mass production of parts compared to a conventional reactor such as that being built at Hinkley C.

I could say much the same about Holtec, a US nuclear services company who are promoting a 300 MW reactor – again not really that small. Like Rolls Royce, it has been exciting local people in places in Yorkshire with talk of building factories. This seems unlikely to happen without, essentially the UK Government paying for all or at least much of the project.

My prize for the most ingenious piece of SMR promotion are the claims made by ‘Last Energy’, who are promoting what they describe as a 20 MW PWR reactor. A headline appeared on the Data Centre Dynamics website saying ‘Last Energy claims to have sold 24 nuclear reactors in the UK for £2.4 billion’ (see HERE). Associated with this was another story in Power Magazine saying (see HERE) that the company had secured PPAs for 34 power plants in the UK and Poland, something that was described as ‘extraordinary progress’.

I cannot see any evidence that these power plants are being constructed, ie ‘concrete poured’ at any site. However, it is claimed that the first project will be finished by 2027. There are reports that the company has been conducting site surveys in Wales (see HERE).

What I find especially puzzling about the Last Energy promotion is the lack of a mention on a specific page on the website of the Office of Nuclear Regulation (ONR). In order for a new design of a nuclear power plant to be licensed to generate in the UK, it has to be approved for what is a very lengthy (several years) and very expensive (many £millions) Generic Design Assessment (GDA). However, there is no mention of Last Energy on the ONR information page giving the current and completed GDAs (see HERE).

Why is all this so-called ‘SMR’ activity happening now?

There are two interrelated factors in operation here; material rewards and political-psychological pressures. Material factors include the designation of governmental programmes to fund demonstrations of so-called SMRs. The second is the possibility of raising share capital to fund projects labeled as ‘SMR’.

Of course this in itself does not explain why this has happened in recent years. An excerpt from an opinion piece published in the Guardian in September 2015 can give us an important clue to the political psychology involved. In an article entitled ‘We are pro-nuclear, but Hinkley C must be scrapped’, written by George Monbiot, Mark Lynas and Chris Goodall, there was a subtitle: ‘Overpriced, overcomplicated and overdue, the Hinkley project needs to be killed off and the money invested into other low-carbon technologies’. The authors’ recommendations for alternative funding went on to say: ‘We would like to see the government produce a comparative study of nuclear technologies, including the many proposed designs for small modular reactor, and make decisions according to viability and price’ (See HERE)

What this looks like to me is a face-saving device. It tries to deal with the (recently re-discovered) fact that new nuclear power stations are much too expensive. I interpret this as a piece of cognitive dissonance to deal with the very apparent limitations of environmentalists trying to promote nuclear power as a response to climate change.

This is a form of cognitive denial of the obvious; that nuclear power is extremely expensive and difficult and very longwinded to deliver. SMRs have been at least partly invented to serve the purpose of shifting mental attention from this fact, a form of denial. The denial is sugar-coated with the notion that we can escape reality by embracing so-called SMRs.

This cognitive dissonance allows people to carry on believing in and promoting nuclear power in spite of reality. A new SMR alternative reality is created. This fills the void created by dull reality.

This, in practice, diverts attention from the central cost problems of nuclear power. These are the quantities of steel and concrete needed to build nuclear power stations, the need for unique types of very expensive parts, and the need for exacting, highly specialised processes of building the reactors. Making smaller nuclear plants will not solve these problems. Indeed it makes them worse insofar as this reduces the possibilities for economies of scale.

Now I am not trying to heap the blame for the SMR fantasies on Monbiot, Lynas, and Goodall – at least not entirely! There is a large well of public wishful thinking attached to things with the word ‘nuclear’ in them and this well can be tapped by concerted, if flimsily-based efforts. The promoters of the so-called SMR technologies are the ones who have ignored history to produce what is, in essence, a warmed-up version of a long-discarded set of nuclear technological ideas and practices. Indeed I would class this stream of historical re-interpretation as an example of the use of postmodernism in the nuclear industry.

SMRs as nuclear postmodernism

Postmodernism emerged originally in architecture. It was, put simply, about reviving ancient, or at least old, building designs and using them in contemporary building design (See HERE). The old is presented therefore as the new. For buildings, that’s a pretty harmless, indeed often pleasing, pathway to adopt. However, to present old (smaller) sizes of nuclear power stations (often mixed in with long discarded design ideas) as new and call them ‘Advanced’ nuclear technologies is, in my view, doing a great disservice to us all. It skews public debate relatively against real green energy options by presenting an option (so-called SMRs) that does not exist.

Social scientists are often derided for talking about postmodernism. Yet here we see the apparent apotheosis of natural science, the nuclear sector, engaging in precisely this sort of approach. They are presenting the technologies of the 1940s to 1960s as ‘new’. We should not have to take it seriously. Many people in the nuclear industry are either living in their own alternative postmodern reality or at least are tolerating this non-existent vision.

There may be a small number of demonstration projects constructed that are called SMRs. They are, and will be, expensive and take a long to build. But they are really just warmed-up old-style versions of the 1950s-1960s-sized reactors, mixed in sometimes with tried and failed techniques. They certainly do not represent an ‘advanced’ path for a nuclear-powered future. As a concept, Small Modular Reactors have no existence outside of a postmodernist nuclear industry fantasy.

I invite people to listen to Bonzo Dog’s old hit ‘Urban Spaceman’ (see HERE). The general spirit and especially the last couple of lines of the song seem especially apposite to a discussion of so-called SMRs.

After I wrote this post came the news that the Ontario Government has given the go-ahead to the so-called SMR project at Darlington. Acclaimed as a breakthrough, it may only be a breakthrough as being the most expensive nuclear power scheme in history. Its starting price, as around $21 billion (Canadian dollars, see HERE) for 1.2 GW is almost exactly the same as the final price of the Flamanville EPR reactor in France built by EDF. This came in at €13 billion, roughly 4 times its original price tag (see HERE). Yet Flamanville has a generating capacity of 1.63 GW, that is around a third larger than the sum of the capacities of the four new Ontario reactors! So the Darlington scheme is already a third more expensive than Flamanville!

The crucial difference between the new Ontario scheme and the French power plant at Flamanville is that construction is only about to start at the Canadian scheme. So, let's repeat this. The (spuriously) acclaimed Ontario SMR scheme is already around a third more expensive than the widely panned super-expensive French Flamanville EPR even before the inevitable construction cost increases start piling up! 

Given that all nuclear power plant built in the West this century have all come in a great deal more expensive than projected before construction, the cost will spiral even farther upwards. It is likely that the Ontario SMR project will win the prize of the most expensive nuclear project (per GW) this century! Even at its projected price the Ontario SMR scheme is calculated by the Ontario Clean Air Alliance to be up to 8xs more expensive than wind power (See HERE) This puts my arguments in this post in perspective, SMRs are going to be a lot more expensive than conventional nuclear power!

pages 156-157, Bupp, I, and Derian, J-C. 1978. Light Water: How the Nuclear Dream Dissolved. New York: Basic Books

May 16, 2025 Posted by Christina Macpherson | Reference, Small Modular Nuclear Reactors | Leave a comment