Small modular reactors (SMRs).

The International Atomic Energy Agency (IAEA) defines a small reactor as one with a capacity under 300MW, compared with the two 1,600MW reactors planned for Hinkley Point C in Somerset or the two 660MW reactors at Hinkley Point B. They are often identified as an acceptable alternative to what are seen as ‘big’ reactors such as the EPR mooted for Sizewell C and which is currently under construction in Somerset at Hinkley. They are seen as less visually intrusive, less dangerous in the event of an accident and more acceptable to a community.  But there are significant drawbacks with SMRs which people should be aware of before backing them as an alternative:


  • They do not currently exist as power reactors. They need a huge amount of (normally public) money for development.  They are not expected to be available for serious consideration as viable power plants until at least 2030.
  • The ‘first of a kind’ build cost for any commercial SMR would be comparable to that of a conventional large reactor and would therefore need Government support.


  • Cost savings for manufacture will typically only be realised after 10 or more reactors have been built, which is likely to be bigger than the UK market for SMRs.


  • They are still nuclear reactors and therefore will therefore:
    • Require planning permission
    • Need safety cases
    • Emergency planning to prepare for a large off-site release of radioactivity
    • Generate nuclear waste which currently has nowhere to go, requiring on site storage
  • SMRs will have to be more numerous if they are to replace large scale reactors, and therefore there will be more individual nuclear waste inventories around the country, requiring more complicated safety, security and storage arrangements
  • The smaller size of SMRs and the claim by proponents that they produce cheaper electricity will lead to corner-cutting on safety, a reduction in safeguarding and security measures in order to reduce costs and operate with fewer staff.
  • They are still quite large – Sizewell A was rated at 420 MWe: SMRs are expected to be only 25% lower in output. They each require an average of 8 hectares of land but with ancillary buildings and services, this is expected to be an underestimate.
  • They do not necessarily generate cheaper electricity: economies of scale dictate that, all other things being equal, larger reactors will generate cheaper power.


  • SMR proponents suggest that mass production of modular reactors could offset economies of scale, but a 2011 study concluded that SMRs would still be more expensive per kWh than current reactors.


  • Mark Cooper, senior fellow for economic analysis at the Vermont Law School‘s Institute for Energy and the Environment argues that SMRs are likely to have higher costs per unit of output than conventional reactors.


  • Even if SMRs could eventually be more cost-effective than larger reactors, this advantage would only come into play if large numbers of SMRs were ordered.


  • Utilities are unlikely to order an SMR until they are seen to produce competitively priced electricity. This ‘Catch-22‘conundrum suggests the technology will require significant government financial help to get off the ground.


  • Due to the larger number of SMRs proponents would wrongly argue are needed to meet electricity demand which has been falling for the last decade and continues to do so , the opportunity for proliferation of nuclear weapons developed from the decay material from the reactors will be increased.
  • SMRs will need a full generic design assessment (GDA) by the Office of Nuclear Regulation (ONR) followed by planning processes to which such nuclear developments are subject – no fast tracking.
  • SMR electricity unit costs of a projected £60-£70 per megawatt hour have since been surpassed by other technologies – particularly renewables – whose costs continue to fall while the costs of nuclear increase.
  • SMRs retain nuclear skills needed for nuclear subs and nuclear weapons.
  • All conventional generating plant, including SMRs, are only 30% efficient as they waste energy as heat.
  • SMRs use high burn uranium fuel for which storage technologies remain unproven.

Further reading:

Rolls Royce website

Dr David Lowry’s blog:

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