Small Modular Reactors: Nuclear Power’s Last Roll Of The Dice?

By Richard Howard

The debate is currently raging as to whether or not nuclear power should be part of the future low carbon energy mix. 

The West’s nuclear building boom of the 1970s is a distant memory and the current fleet of aging reactors have already started to be phased out.

This is not universally the case. In China and Russia nuclear is being actively encouraged but elsewhere (e.g. Austria and Germany) it is being shunned [1]. Other places such as Japan swing from one extreme to another [2]. Whereas some places, such as the EU, are split down the middle as to whether nuclear will play a part in its future – 10 out of the 27 EU member states think nuclear should count as a green investment, 17 out of 27 do not [3]

Furthermore, spiralling costs and delays at plants under construction have dampened many governments enthusiasm for new large scale nuclear projects [4, 5]. That is even before the topic of safety, environmental impact, and waste handling is broached.

The nuclear industry has known it has been in a tight spot for the past few decades and the current round of existing designs/plants under construction do not look like they will lead to many more orders, in the West at least. Therefore the industry, with encouragement from governments, is looking to new technologies in order to sustain critical mass.

Small Modular Reactors

Small modular reactors (SMRs) are an attempt by the nuclear industry to shrink existing reactor designs and technology. In the process making the building, operating, maintaining, and disposal of a reactor much cheaper [6, 7].

The key change is not to the underlying nuclear physics of the reactor but to the engineering and the design. By making the reactors in a centralised factory the production process can be standardised, optimised, and economised. The transportable reactor can then be driven or shipped to the power plant and installed, plumbed in, and connected to the grid. This avoids expensive custom builds for each unique site.

Since each reactor is its own module at the end of its life the reactor could be lifted out of situ and transported whole to a centralised location for decommissioning.

Each SMR will be smaller than a traditional reactor (up to 300MW vs 1GW+) but multiple can be installed at each site. Thereby giving a combined output similar to a large single reactor. This also increases the flexibility of each site since each SMR can be serviced individually instead of turning off a whole power station.

There are many Small Modular Reactor designs already in existence, with plenty of companies proposing marketing their plans. Furthermore, it can be argued that there are already some SMR designs currently functioning since nuclear submarines rely upon small compact nuclear reactors as their primary power source [8]. It is unlikely, we will ever know how similar the proposed designs are to those used on submarines, however it does prove that nuclear technology can be shrunk successfully.

Advanced Modular Reactors

Advanced modular reactors (AMRs) are advertised as having many of the advantages of SMRs but with the added bonus of new or updated reactor technology. As stated above SMRs are currently shrunk versions of existing reactor technology. AMRs, however, use newer* reactor designs which in theory are either safer, cheaper, or more efficient than existing designs.

*Many of the designs have actually been around since the 1950s but have never been commercialized or scaled.

For example thorium molten salt reactors use liquid salt as both the heat exchange mechanism and the fuel. This leads to greater efficiency as well as greater levels of safety since the fuel can be removed quicker in the event of failure [9]. Thorium molten salt reactors have also been enjoying a resurgence in interest since thorium is far more abundant than traditional uranium fuel. Individual countries will have specific geopolitical reasons for developing different designs and with large scale government backing they might even become commercially viable.

Another reactor type is fast neutron reactors, which promise to more efficiently convert nuclear fuel into energy. Therefore, requiring less uranium in the first place and producing less (importantly not no) long-lived nuclear waste [10].

However the nuclear industry is about as conservative as an industry gets and acceptance of new designs is not guaranteed especially without the long service records of proven existing designs – even if they are objectively safer on paper.

Nuclear Fusion

And lastly if the above fails then there is always nuclear fusion. Much-maligned for ‘always being 30 years away’, the past 10 years has seen a renewed effort by governments to develop the near limitless source of energy. The interesting thing about this latest cycle of fusion hype is that it is creating lots of interest from the private sector. Just as government-owned NASA put its faith in privately-owned SpaceX can the same be done for nuclear fusion small modular reactors? Unfortunately, that’s for another blog…

The Last Role of the Dice

Ever since its conception the promise of nuclear energy has been difficult to ignore. Famously nuclear energy was misforecast as “too cheap to meter” [11], however, since then it has not lived up to its initial promise. But in the face of the current climate crisis it is still seen as having a big advantage: low carbon domestic energy.

Over other nuclear technology and roadmaps, small modular reactors use physics which has the benefit of millions of hours of operation under its belt. And since the nuclear industry is rightly paranoid about safety and switching to another technology has risks, both physical and financial.

Nuclear reactors are complex systems and so are the humans that run and finance it. The biggest initial financial hurdle is that there are huge upfront construction costs, which all have to be paid before the plant generates a single kW of saleable electrical power. The UK Government has recently tried to ease this process with the Regulated Asset Base (RAB) finance model [12], but financial risks remain.

For new nuclear technology to breakthrough it has to prove itself against the existing physics. This will take lots of time and lots of money. Safety, safety, safety remember. But in the meantime if a fleet of reliable small modular reactors have been built, proven, and earning a return on investment will they stand a chance? Why take another long term gamble?

And if SMRs do not pan out? Then it will be doubly difficult to convince anyone to take a risk on a new nuclear technology, no matter how good they look on paper. So for the nuclear industry, small modular reactors have to work…


So the nuclear industry is pivoting towards small modular reactors, with the promise of lower costs (initial investment and running costs) and the ability to help with the climate crisis, but key questions still remain: Are they better for the environment at large? They will still produce nuclear waste but will they leave sites contaminated for hundreds of years? Are they a transition technology or a sustainable future? Do we solve the climate crisis now with small modular reactors and then create a halcyon future with Fusion SMRs?


  1. Frederic Simon, 2021, Germany leads call to keep nuclear out of EU green finance taxonomy, Euractiv
  2. Sakura Murakami, 2017, Japan PM’s nuclear push faces resistance ahead of election, Reuters
  3. Frédéric Simon and Kira Taylor, 2021, The Green Brief: Gas, nuclear and the EU taxonomy saga, Euractiv
  4. Rod Walton, 2021, Vogtle nuclear expansion facing yet another delay, Georgia Power reports, Power Engineering
  5. Nora Buli, 2021, Finland’s Olkiluoto 3 nuclear reactor faces another delay, Reuters
  6. IAEA, 2021, Small Modular Reactors
  7. World Nuclear Association, 2021, Small Nuclear Power Reactors
  8. Jillian Ambrose, 2021, Rolls-Royce secures £450m for mini nuclear reactors venture, The Guardian
  9. IAEA, 2020, Advances in Small Modular Reactor Technology Developments, A Supplement to: IAEA Advanced Reactors Information System (ARIS)
  10. World Nuclear Association, 2021, Fast Neutron Reactors
  11. Lewis Strauss, 1954, Remarks prepared by Lewis L. Strauss
  12., 2021, Future funding for nuclear plants

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