Small Modular Reactors (SMRs) of up to a few hundred megawatts capacity are being touted by some as the way ahead for nuclear power since they are expected to be quicker to build than large gigawatt scale plants and so less costly to finance, with mass production also reducing unit costs. They might also be located in or near cities so that the waste heat they produce could be fed to district heating networks, the use of this extra output offsetting their cost further. It may also be possible, it is claimed, that their power output could be more easily varied, so that they could play a role in grid balancing, though, as with large nuclear plants, that would undermine their economics- it is best to run them flat out.
There has certainly been much enthusiasm expressed for the idea, with various vendors offering their wares, for example http://www.westinghousenuclear.com/New-Plants/Small-Modular-Reactor Estimates of costs vary, but in the US context it has been claimed by NuScale that ‘first of kind’ SMRs might generate at around 101cents/MWh, falling to 90c/MWh on mass production, cheaper than new large advanced nuclear plants at 96c/MWh, and also cheaper that coal fired plants, but not competitive with unabated combined cycle gas plants (64-66c) or wind plants (80c) or hydro (85c). http://www.nuscalepower.com/images/nuscale_smr_benefits/Right_Column/nuscale-operating-costs.jpg
Some of the designs for SMRs are quite exotic, based on the use of fuel dissolved in molten salt which then acts as both reaction medium/moderator and heat transfer /coolant medium. Terrestial Energy amongst others is pushing this Molten Salt Reactor idea, and is seeking US government backing: http://www.world-nuclear-news.org/NN-Terrestrial-Energy-to-complete-US-loan-guarantee-application-1409167.html It may take a while to happen- this is new ground. But some of the less radical ideas might be faster to develop. The UKs Energy Technologies Institute says SMRs could be up and running in the UK by 2030 if R&D work gets underway soon and should be designed to be able to run in CHP mode, so that they can provide heat as well as electricity: http://www.eti.co.uk/insights/the-role-for-nuclear-within-a-low-carbon-energy-system/
Although much work will have to be done to modify the technology for civil power (and possibly heat), it is claimed that civil SMRs can be based on existing nuclear submarine propulsion technology, which is well established, with companies like Rolls Royce being well placed to develop suitable units: www.telegraph.co.uk/business/2016/03/19/rolls-royce-could-power-britains-nuclear-future-with-mini-reacto/ However the submarine and civil contexts are very different, with very different operational requirements and operating regimes. Safety and reliability is obviously a key issue in all contexts, but even in the closely managed military environment things can go wrong: www.theguardian.com/world/2011/mar/10/royal-navy-nuclear-submarine-reactor-flaws And spreading SMRs around in urban areas could pose safety and security risks, with local public acceptability potentially being a big issue.
In the USA however, the Tennessee Valley Authority (TVA) claims that SMRs could be put close to population zones and it is looking to reduce the risk of issues such as emergency
planning evacuation zones slowing operating project approval. They say that, given safety
upgrades, ‘based upon the preliminary information which we've received from the four vendors, we are confident that all of them can be supported by a two-mile emergency plan [zone] and at least one has capability of site [only] boundary’ i.e. no safety zoning beyond the plant site. That compares with 10 miles typically required for a large reactor. http://analysis.nuclearenergyinsider.com/us-operator-seeks-swift-smr-licensing-optimize-low-carbon-output
That seems a little provocative. Will anyone accept mini nukes in their backyards? And what about security? SMRs will pressumably be sealed modular units, making access to the fissile material hard, but, unless they are very carefully guarded, they might still provide an enticing and convenient target for terrorist attack. In terms of safety, the US Union for Concerned Scientists says that ‘Multiple SMRs may actually present a higher risk than a single large reactor, especially if plant owners try to cut costs by reducing support staff or safety equipment per reactor.’ It adds that ‘some proponents have suggested siting SMRs underground as a safety measure. However, underground siting is a double-edged sword- it reduces risk in some situations (such as earthquake) and increases it in others (such as flooding). It can also make emergency intervention more difficult. And it increases cost.’
There are thus a range of technical, economic, safety and security issues to face, not least the issue of social acceptance, with there being no clear indication that they can be resolved: http://www.academia.edu/8114310/One_size_doesn_t_fit_all_Social_priorities_and_technical_conflicts_for_small_modular_reactors
From the industry side however, enthusiasm remains strong, and there is much debate about exactly how to proceed and on what basis. For example, should SMRs replace large nuclear plants in any future programme? In the UK context, ETI’s 2015 report on ‘The role for nuclear within a low carbon energy system’ said that contrary to the claim SMRs might be better than large nuclear plants, ‘large reactors are best suited for baseload electricity production’. However, it notes that, based on using existing (nuclear) sites for them, there is ‘an upper capacity limit in England and Wales to 2050 from site availability of around 35 GWe,’ while there could be room for at least 21GW of SMRs in the UK, given that more sites could be available for them, including near cities, where the heat option offered a key economic compensation. So, although SMRs ‘may be less cost effective for baseload electricity production, SMRs could fulfil an additional role in a UK low carbon energy system by delivering combined heat and power (CHP) - a major contribution to the decarbonisation of energy use in buildings’, assuming the necessary district heating infrastructure was available, with SMRs delivering heat into cities ‘via hot water pipelines up to 30km in length’.
In this context it is interesting that, more recently, the Newcastle-based SMR enthusiasts Penultimate Power thinks SMRs will work best as ‘complementary to, rather than competing with’ the large-scale nuclear plants: http://www.chroniclelive.co.uk/business/business-news/newcastle-company-forefront-technology-small-10869984
A SMR assessment programme has been launched by the UK government, and SMR programmes are going ahead in the USA and elsewhere: http://www.world-nuclear.org/information-library/nuclear-fuel-cycle/nuclear-power-reactors/small-nuclear-power-reactors.aspxThis is all in a context where, according to the UK National Nuclear Laboratory, the potential market for SMRs might be up to 85 GWe by 2035: http://www.world-nuclear-news.org/NN-UK-considers-how-to-use-small-reactor-opportunity-1910161.html That may be optimistic. The OECD says ‘up to 21 GWe of SMRs could be added globally by 2035’. http://www.oecd-nea.org/ndd/pubs/2016/7213-smrs.pdf And there is no shortage of critical comment on the whole idea:
http://oilprice.com/Alternative-Energy/Nuclear-Power/Why-Small-Modular-Reactors-Are-Not-The-Next-Big-Thing.html and http://realfeed-intariffs.blogspot.co.uk/2016/04/small-modular-reactors-wishful-thinking.html
It’s not a new idea: in addition to the small units developed for the US military in 1940’s, (for planes and ships) there were may attempts to build small civilian nuclear plants in the USA in the 1950s, mostly with poor results: http://spectrum.ieee.org/energy/nuclear/the-forgotten-history-of-small-nuclear-reactors The current flurry of enthusiasm for SMRs seems to be mainly driven by the failure of conventional nuclear to expand as fast as the industry would like. It’s stalled or declining in many parts of the world, due to poor economics and local opposition, and the existence of better, cheaper renewable alternatives. However, SMRs may not offer much help in changing this situation. There will no doubt be some prototype projects around the world in selected sites, and some projects may be suited to specialised applications, for example in remote sites or for some industrial processes: http://www.sciencedirect.com/science/article/pii/S0301421512000249
Or even mobile units like this: http://www.independent.co.uk/news/world/asia/china-nuclear-reactor-south-china-sea-spratly-islands-soviet-submarines-a7356246.html
However, in terms of widespread use for public power and heat production, given the practical problems of finding acceptable sites and the uncertain economics, plus all the usual problems with nuclear, including what to do with the radioactive wastes that are produced, it could be that SMRs may not prove to be that significant. But it’s also possible that they may boom, if a wider market emerges and/or if there are some major technological breakthroughs: http://www.powermag.com/market-small-modular-reactors/
All this and much more is covered in Dave Elliott’s new book for the Institute of Physics: ‘Nuclear Power: Past, present and Future’, out soon.