Small Modular Reactors: One component of a sustainable energy future?

According to the US Department of Energy, global energy use and carbon emissions are set to increase more than 50% by 2025. Demand in China and India is expected to escalate a combined 91%, with other developing countries close behind. Industrialised states’ needs’ are expected to grow by approximately one-third. Governments’ efforts to curb the resulting environmental effects are generally met with low expectations.

The world is at a vital crossroads. While wealthy countries’ consumption will increase less rapidly, it will still do so substantially. Simultaneously, developing states will continue their ever-greater pursuit of resources as they aim to close the economic gap with their industrialised peers.

Ensuring a sustained healthy natural environment and energy-secure future requires a multifaceted approach. No single source can be relied upon too heavily. Of course, fossil fuels are the principal cause behind these grave issues. While nobody definitively knows when reserves will be depleted, it is apparent that, regardless of how long it takes, pollution and price volatility will continue to be commonplace, especially with regard to oil. Though natural gas offers a cleaner alternative and in most cases a cheaper one as well, procurement methods like fracking mitigate such benefits by worsening environmental conditions. Renewables, regularly touted as a solution, pose their own issues.

As evidenced by recent crises, biofuel use plays an integral role in raising food prices. Generally speaking, solar power is too expensive. Like its cheaper counterpart wind, solar energy is dependent on weather, limiting its use to certain places. Moreover, both of these energy generation forms are difficult and costly to store, though technology is improving.

Nuclear is frequently proposed as another alternative. However, its most commonly advocated form also has daunting challenges.

‘Big’ usually comes to mind when people think of nuclear power. Reactors regularly exceed 1,000Mw capacities. To reach economies of scale, conventional wisdom holds that bigger is better, a recurring theme in many countries’ nuclear discourse. If such aspirations are realised, low carbon, extraordinarily profitable fuel can be produced for decades. Nonetheless, enormous obstacles can prevent these ambitions’ fulfilment.

Capital requirements can easily exceed several billion dollars, often leaving even the most solvent bodies unable to finance projects alone. Construction costs vary widely, causing problems if funding estimates are too low. Safety, security, infrastructure, waste management and decommissioning also contribute significantly. Operation and maintenance expenditures, though one of the cheapest components, are expensive enough to cause problems for weak entities like developing countries. Moreover, liberalised energy markets in much of the world prevent prices from being guaranteed long into the future. Huge profits can result if these obstacles are overcome, but long construction times and vast total costs mean that investment returns, if ever attained, can take dozens of years. Nevertheless, as important as they are, nuclear power’s economic risks are not its only ones.

Like construction costs, the potential levels of severity of nuclear accidents also vary widely. A large reactor’s very existence carries with it the possibility of a catastrophic accident or terrorist incident capable of irreparable environmental, human and financial damage. Nuclear power, as we know it, has enormous intrinsic risks and no guaranteed benefits.

However, new nuclear technology is being developed. Several companies intend to put Small Modular Reactors (SMRs) on the market within the next decade. SMRs’ sizes range from 10 to 300Mw for each reactor module. Plants will be able to accommodate as few as one or up to ten or more modules depending on the model. While no two SMR makes have the same energy generation capabilities, all are variations of similar design and operations concepts. They aim safely and securely to produce low cost, clean fuel while minimising the huge infrastructural requirements and environmental, human and financial risks associated with large nuclear plants.

Depending on the model chosen and the number of reactors installed, a single SMR plant could produce enough electricity for a hospital, university, refugee camp or even neighbourhoods, towns and cities comprising tens or hundreds of thousands of people. One of SMRs’ key advantages is that capacity will have the ability to be modularly augmented or downsized if demand fluctuates, instead of being set permanently, as is the case with current technology.

Other principal benefits include factory assembly rather than on-site construction, allowing SMRs to be deployed much faster than large plants. Manufacturers also assert that SMRs’ compactness will allow them to be easily shipped worldwide. Moreover, most models’ operations sites will be housed underground. Many will also store waste in underground spent fuel pools during the plant’s operating life, while others aim for off-site storage and reprocessing as soon as possible.

Although the majority will embrace refuelling methods taking place at the operating site, some will ship spent modules back to the factory and replace them with new, pre-fuelled reactors. These manufacturers argue that this will greatly simplify the decommissioning process while allowing for power supplies to continue uninterrupted.

Concerning safety and security, SMRs’ underground operating sites are intended to address post 11 September and Fukushima concerns by making reactors more difficult to sabotage, while also requiring less personnel, thereby aiming to drive down associated costs. Passive cooling systems not requiring offsite power will also be utilised. Industry professionals believe that these innovations could, in the event of an accident, keep fuel cool enough to prevent a meltdown for at least several days, more than enough time to respond. Any accidents that do occur, manufacturers assert, would be minimised due to SMRs’ small-size and underground location, preventing off-site evacuations and surrounding areas’ contamination.

Some estimates suggest that SMRs may be able to produce power significantly cheaper than fossil fuels. They could be particularly useful in sparsely populated, isolated areas where connecting to existing grids is a problem. However, despite their significant potential benefits, SMRs are not free of concerns. Though much less costly to finance and construct than large plants, SMRs are not cheap. Depending on the design and size of the module, they could cost anywhere from 25 to 500 million dollars for each reactor.

Furthermore, SMRs’ economic concerns do not end once a plant is operational. Detractors suggest that it will be impossible for SMRs to reach economies of scale. Due to their smaller size, some argue that it will be much more expensive for SMRs to produce energy. Supporters counter with an assertion that because SMRs are less expensive to construct, they will be able to run operation and maintenance costs equal to or higher than large nuclear plants and still be extraordinarily profitable. Supporters also claim that due to SMRs’ smaller size, much less personnel will be required to staff and guard them, offsetting any steep operation and maintenance costs.

SMRs’ uncertain economic prospects necessitate prudence before endorsing their use, especially for weak financial entities like developing countries. However, they are not the only reason for caution. While innovations like underground operations and spent fuel storage represent considerable safety and security improvement over large plants, they do not inherently merit the immediate use of further cost-saving measures in those areas, contrary to manufacturers’ indications. Nor do they justify the dismissal of disaster’s possibility, as some have a tendency to do.

While proponents may be correct that SMRs’ underground containment would insulate the local environment from accidents, making off-site evacuations unnecessary, meltdowns are never a positive occurrence and the scale of any repercussions is difficult to predict. Therefore, such events must be prepared for even if they are mild or unlikely. These issues must especially be considered if units would be housed near population centres.

Furthermore SMRs, though small, still have enough radioactive material to pose a terrorist threat. While design features go a long way in protecting against such incidents, it is ill-conceived to think that they would justify significantly less operations and security staff as an initially viable option because certain aspects of SMR security are particularly uncertain. For example, SMRs’ size might make them easier to guard. However, it could also be easier to steal or sabotage reactors, especially if off-site refuelling is utilised along with reduced personnel details guarding operating sites and radioactive transports.

Regarding waste, individual SMRs provide advantages over large plants, as they would create much less. However, widespread use would work against this. Moreover, while underground, spent fuel pools are an improvement over current waste management techniques, they are only a temporary solution that defers the impending, crucial necessity of a permanent disposal method.

Because SMRs pose challenges, some unique and others similar to conventional nuclear plants, convincing the public that they are different might prove incredibly difficult. However, as with other energy generation techniques, SMRs’ benefits must be weighed against their drawbacks, so that informed decisions can be made about their potential. A sustainable environment and energy-secure future will require a set of diverse, innovative solutions. It is time to seriously consider whether or not SMRs should be added to the mix.

Edward Levy recently graduated with an MSc in Globalisation and Development from London University’s School of Oriental and African Studies. He can be reached at



  1. Karen Kibler

    I find the article on SMR’s informative. I do have a concern of trasporting spent fuel bundles vs refueling on-site. The risk of transporting vs cost of on-site refueling, I would think transporting would be too high, unless the manufacturing company is close to the site and transported underground. Article was good.
    ~ Karen~ radiation protection technician

  2. Pietro Agostini

    I agree that SMR have some advantages such as short construction time and lower financial exposure; also the technical advantage to allow an easier emergency cooling should be mentioned. Nevertheless they cannot be considered sustainable if additional features are not added. Present reactors based thermal neutrons make an inefficient use of fuel and release too many minor attinides which decay in 340000 years, therefore they cannot be considered “sustainable”. The only sustainable reactors are those based on fast neutrons, that is to say having a different coolant: sodium or lead or helium.Finally we must underline that after Fukushima the major axpectation are devoted to safe reactors: SMR having water as coolant are still subject to risk of hydrogen formation and explosion in case of accidentally reached high temperature. Agai the solution is represented by a different, less reactive, coolant: lead.
    In conclusion I am in favour of small modular reactors provided that the technologies of fast neutrons and lead coolant are applied. Some designs do that in USA and in Russia.

  3. George Yadigaroglu

    “Regarding waste, individual SMRs provide advantages over large plants, as they would create much less.”
    What is the basis of this claim? Per unit power produced, all plants produce the same amount of fission products, unless you have a better fuel cycle in mind…

  4. Stephen Tindale

    I’ve asked Edward to answer this. Thanks. Stephen

  5. Edward Levy

    Hi all,

    Thank you very much for your comments. It is wonderful to dialogue with people who are informed about energy issues.


    I completely agree with you. Your concerns about off-site refueling figured heavily in my masters thesis and are an important theme in an article I am writing about SMRs’ potential in developing countries. I have had an ongoing conversation with several prominent potential SMR manufacturers. I can tell you that:

    NuScale originally planned to use off-site refueling, but abandoned this prospect after rethinking the economics and logistics. However, some companies still favor off-site refueling. They have justified it to me as a matter of operators’ personal choice. In their view, some utilities may have no problem opening the reactor core to engage in on-site refueling, while others might view their circumstances as better suited for permanently-sealed reactor designs requiring off-site refueling.

    In my opinion, off-site refueling’s detrimental risks which you mentioned, make it an issue too substantial to be dictated by preference. Furthermore, the belief espoused by potential SMR manufacturers that accidents would not merit off-site evacuations, would be an additional strike against off-site refueling if proved correct.

    If you haven’t already seen it, you might find this link interesting

    It has all of the written testimony of parties involved in the July 2011 US Senate Appropriations Committee hearing on SMRs. A link to a video of the hearing is there as well.


    Passive cooling systems were explained in paragraph thirteen. I apologize for not going into greater depth. However, I was trying to write concisely. Regarding your other points, I would like to recommend that you read the following NEA study (paste the link into google or else it won’t work)

    Sections 8.5-8.7 on pages 124-127 discuss the potential specifications of various SMR designs with alternate coolants


    I was thinking in terms of overall volume of waste. For example, compared to a gigawatt scale reactor, a full-capacity 640MWe mpower plant or a 540 MWe NuScale plant would produce less. However, if SMR capacity outweighed gigawatt-scale capacity in a given geographic area, this would not be the case.
    You might find interest in page fifteen of the study I cited in my response to Pietro. It projects that due to their smaller reactor core, SMRs would generally not be as neutron-efficient as large reactors.

  6. Richard Baldwin

    Hi Edward,

    Thanks for the interesting article. I confess that I dont know much about SMRs – what type of fuel do they use ? Is it similar to LWRs or would major investment in fuel fabrication facilities be required ?



  7. Hi Richard,

    Apologies for the late response. I just saw your comment. 2 of the most prominent models, NuScale and Babcock and Wilcox’s mPower are designed to use standard LWR technology. A third design, the Hyperion Power Module is designed for lead-bismuth coolant. Please see pages 15 and 35 of the following study for a complete list of advanced SMR designs along with currently deployable models, respectively. Paste the link into google or it won’t work. Charts on these pages describe the fuel specifications of the various reactor designs. Please remember that not all SMRs are modular. The acronym can mean either ‘Small Modular Reactor’ or ‘Small/Medium Reactor’ (defined by the IAEA as a capacity of 300-700MWe per individual module).

    Let me know if you have any more questions.

    Best regards,


  8. Note: the correct page numbers are 13 for advanced SMR designs and 35 for readily deployable SMRs. Apologies for the typo.



  9. Edward Knuckles

    Mr. Levy, you have provided a sober and concise overview of the issues related to the SMR but I would add a belated comment regarding the on-site vs. off-site refueling debate mentioned above. The new fuel has to get to the reactor site and the spent fuel has to ultimately be removed from the reactor site; when and how this occurs is a matter of safety, timing, and efficiency. Off-site refueling would be preferable if you can remove the entire core as a single package in the case of a naval reactor and replace it with a new one; However, the use of significantly lower enrichments in civilian reactors would make this evolution more frequent and possibly not economical.

    Off-site refueling of the SMR has a distinct disadvantage should one of the fuel assemblies fail; it forecloses the possibility of “repair” on-site which in itself is a complicated but doable process. It is reasonable to expect such failures to occur in a new fuel design such as those proposed for the SMR. Such failures in large scale LWR fuel assemblies have occurred and are related to either manufacturing or operation but have occurred on a decreasing frequency as their fuel designs have matured. These types of failures usually entail small breaches of the metallic cladding surrounding the fissionable material and the subsequent release of radioactive fission products into the surrounding coolant. The return of a sealed vessel containing damaged fuel to the manufacturer can be expected to be a more costly and environmentally risky affair than on-site repair because the fission products are less securely contained during transport than if the fuel had not been damaged.

  10. S. J. Blakely

    While I agree that the Nuclear Industry in the US need to be revamped to make it viable into the future, I’m not at all sure SMR’s are the complete answer. They surely can and should be part of the solution though.

    I believe standardization of equipment and design of new and/or revamped generating stations would also have cost cutting benefits for construction and operation. One of the benefits of standardization is the reduction of maintenance and re-fueling costs due to having a cadre of maintenance/re-fueling workers that travel from one plant to the next.

    As it is today each plant relies heavily on contract workers in every discipline to assist in re-fueling and/or maintenance evolutions. Having been an Outage Coordinator in the containment structure at Diablo Canyon during re-fueling activities it was apparent that those outage workers not familiar with the plant layout, equipment, tooling and policies were less efficient than those that were more familiar.

    There is also the NIMBY problem of the positioning of new plants mainly associated with the issue around the storage and/or disposal of spent fuels. It’s been my experience that most communities don’t want a nuclear plant in the neighborhood. I believe that positive education of the public, not just an Ad campaign is necessary to overcome the stigma associated with nuclear power stations. The risks as well as the benefits must be addressed openly. Community by-in is absolutely vital to the future of the industry, and SMR’s just might be a key to public acceptance of this much needed piece of our energy picture.

    As someone with seventeen years experience in nuclear power generation I want very much to see this industry flourish. I’m all for anything that would allow our industry to move forward.

  11. Hi Edward,

    I have a couple observations that might help your research.

    – $25-500 million a copy is too low of a cost for a nuclear power plant. $2 billion a copy and ~$5 billion for the first units (including non-recurring engineering, qualification testing, tooling, etc.) is more realistic and more consistent with numbers I have heard used by serious reactor vendors exploring SMRs.

    – The key disadvantage of many SMR concepts is putting safety-critical equipment (control drives and pumps) in a harsh, primary water environment where it will inevitably fail. The equipment is not necessarily fail-safe, meaning that certain kinds of control drive mechanisms can fail in this environment in such a way that the control rod will not insert. Failures during operation will cause disruptive and costly down time. Equipment replacement is costly and difficult, as is connecting and disconnecting electrical equipment in a radiation field during refueling. The costs and risks associated with emergent equipment failures should be weighed in the SMR business case. I expect that compared to known technologies, like making piping welds, the cost and risk of putting equipment inside the reactor vessel for a perceived “factor construction benefit” is not worthwhile.

    – While I am not an expert, I do not think that the size of the installation controls guard force size or security costs. My understanding is that security requirements are designed around a threat to be guarded against and not strongly dependent on site size for something the size of even a small nuclear power plant. You might want to research the requirements more.

    Otherwise, thanks for your article.

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