View source for Engineering:Small modular reactor

{{Short description|Small nuclear reactors that could be manufactured in a factory and transported on site}}
[[File:Figure 4 Illustration of a light water small modular nuclear reactor (SMR) (20848048201).jpg|thumb|Illustration of a light water small modular nuclear reactor (SMR)]]

'''Small modular reactors''' ('''SMR'''s) are a class of small nuclear fission reactors, designed to be built in a factory, shipped to operational sites for installation and then used to power buildings or other commercial operations. The first commercial SMR was invented by a team of nuclear scientists at [[Organization:Oregon State University|Oregon State University]] (OSU) in 2007.<ref>{{cite web |title=Oregon State-NuScale partnership powers the future of nuclear energy |url=https://advantage.oregonstate.edu/feature-story/oregon-state-nuscale-partnership-powers-future-nuclear-energy |website=advantage.oregonstate.edu |access-date=17 December 2023}}</ref> Working with OSU's prototype, [[Company:NuScale Power|NuScale Power]] developed the first working model, available to the US market, in 2022.<ref>{{cite web |last1=Musto |first1=Julia |title=NuScale Power secures NRC certification for its SMR design |url=https://www.foxnews.com/tech/u-s-approves-first-small-modular-nuclear-reactor-design |website=foxnews.com |publisher=FOX News |access-date=17 December 2023}}</ref> The term SMR refers to the size, capacity and [[Modular design|modular]] construction. Reactor type and the nuclear processes may vary. Of the many SMR designs, the [[Engineering:Pressurized water reactor|pressurized water reactor]] (PWR) is the most common. However, recently proposed SMR designs include: [[Engineering:Generation IV reactor|generation IV]], [[Engineering:Thermal-neutron reactor|thermal-neutron reactor]]s, [[Physics:Fast-neutron reactor|fast-neutron reactor]]s, [[Engineering:Molten salt reactor|molten salt]], and [[Engineering:Gas-cooled reactor|gas-cooled reactor]] models.<ref name=":2" /> 

Military specified small reactors were first designed in the 1950s to power [[Engineering:Ballistic missile submarine|ballistic missile submarine]]s and ships ([[Engineering:Aircraft carrier|aircraft carrier]]s and ice breakers) with nuclear propulsion.<ref name="BASE">{{cite web | author=BASE, the German Federal Office for the Safety of Nuclear Waste Management | date=2023-01-15 | title=Small Modular Reactors (SMR) | website=BASE | url=https://www.base.bund.de/EN/ns/ni-germany/smr/small-modular-reactors_node.html | access-date=2023-12-12}}</ref> The electrical output for modern naval reactors are generally limited to less than 165 MW<sub>e</sub> and dedicated to powering turboshaft props rather than delivering commercial electricity. In addition, there are many more safety controls absent from naval reactors due to the space limitations these reactors were designed for. 

Commercial SMRs can be designed to deliver an electrical power output as low as 5 [[Watt#MWe|MW<sub>e</sub>]] (electric) or a maximum of 1000 MW<sub>e</sub>. SMRs may also be designed purely for desalinization or facility heating rather than electricity. These SMRs are measured in megawatt thermals [[Watt#MWt|MW<sub>t</sub>]]. Many SMR designs rely on a modular system, allowing customers to simply add modules to achieve a desired megawatt output (MW<sub>e</sub>). Some SMR designs{{Which|date=October 2022}}, typically those using [[Engineering:Generation IV reactor|Generation IV reactors]] technologies, aim to secure additional economic advantage through improvements in electrical generating efficiency from much higher temperature steam generation. Ideally, modular reactors are expected to reduce on-site construction, increase containment efficiency, and claim to enhance safety. However, other SMR manufacturers claim greater safety should come through the application of [[Physics:Passive nuclear safety|passive safety]] features that operate without human intervention. Passive safety is a concept already implemented in some conventional nuclear reactor types. SMRs should also help reduce power plant staffing costs, as their operation is fairly simple.<ref name="auto22" /><ref name=":0b" /> and are claimed to have the ability to bypass financial and safety barriers that inhibit the construction of conventional reactors.<ref name=":0b" /><ref name=":1" />

As of 2023, only China and Russia have successfully built operational SMRs. The US Department of Energy had estimated the first SMR in the United States would be completed by [[Company:NuScale Power|NuScale Power]] around 2030,<ref>{{cite web |title=Technology Deployment |url=https://www.iea.org/energy-system/electricity/nuclear-power#tracking |website=iea.org |publisher=US Department of Energy |access-date=19 December 2023}}</ref> but this deal has since fallen through after the customers backed out due to rising costs.<ref>https://www.science.org/content/article/deal-build-pint-size-nuclear-reactors-canceled</ref> There are more than 80 [[Engineering:List of small modular reactor designs|modular reactor designs]] under development in 19 countries.<ref name="nei-20230118" /> Russia has been operating a floating nuclear power plant Akademik Lomonosov, in Russia's Far East ([[Earth:Pevek|Pevek]]), since October 2022. The floating plant is the first of its kind in the world. China's [[Engineering:Pebble-bed reactor|pebble-bed]] modular high-temperature [[Engineering:Gas-cooled reactor|gas-cooled reactor]] [[Engineering:HTR-PM|HTR-PM]] was connected to the grid in 2021.<ref name="nei-20230118" />

SMRs differ in terms of staffing, safety and deployment time.<ref>{{cite web|url=https://www.hoover.org/sites/default/files/research/docs/ostendorff_licensingsmrs_2rs_reduced_4_0.pdf|title=Licensing Small Modular Reactors: An Overview of Regulatory and Policy Issues|date=2015|website=Hoover Institution}}</ref> US government studies to evaluate SMR-associated risks are claimed to have slowed the licensing process.<ref name="auto" /><ref name="smallBeauty" /><ref name="sciencedirect.com">{{cite journal|last1=Mignacca|first1=Benito|last2=Locatelli|first2=Giorgio|last3=Sainati|first3=Tristano|date=20 Jun 2020|title=Deeds not words: Barriers and remedies for Small Modular nuclear Reactors |journal=Energy|volume=206|page=118137|doi=10.1016/j.energy.2020.118137|doi-access=free|hdl=11311/1204935|hdl-access=free}}</ref> One main concern with SMRs and their large number, needed to reach an economic profitability, is preventing nuclear proliferation.<ref name="areva-20100618">{{citation |last=Greneche |first=Dominique |title=Proliferation issues related to the deployment of Small & Medium Size reactors (SMRs) |date=18 June 2010 |url=http://bnrc.berkeley.edu/documents/forum-2010/Presentations/S-Session-III/Dominique_Greneche_NuclearConsulting_Pres.pdf |archive-url=https://web.archive.org/web/20170324173959/http://bnrc.berkeley.edu/documents/forum-2010/Presentations/S-Session-III/Dominique_Greneche_NuclearConsulting_Pres.pdf |publisher=Areva |format=presentation |archive-date=24 March 2017}}</ref><ref name="auto1b" />

== Background ==
=== Hope of enhanced safety and reduced costs ===
Economic factors of scale mean that nuclear reactors tend to be large, to such an extent that size itself becomes a limiting factor. The 1986 Chernobyl disaster and the 2011 Fukushima nuclear disaster caused a major set-back for the nuclear industry, with worldwide suspension of development, cutting down of funding, and closure of reactor plants.

In response, a new strategy was introduced by American SMR manufacturer, [[Company:NuScale Power|NuScale Power]], aimed at building smaller reactors, which were expected to be faster to fabricate, safer to operate, and operate at lower cost per reactor. Despite the loss of scale advantages and considerably less power output, funding was expected to be easier thanks to the introduction of modular construction and projects with anticipated shorter timescales. The generic SMR proposal is to swap the economies of unit scale for the economies of unit mass production.<ref>{{Cite web |title=Chasing Cheap Nuclear: Economic Trade-Offs for Small Modular Reactors |url=https://nae.edu/239267/Chasing-Cheap-Nuclear-Economic-TradeOffs-for-Small-Modular-Reactors |access-date=2023-12-05 |website=NAE Website |language=en}}</ref><ref>{{Cite journal |last1=Mignacca |first1=B. |last2=Locatelli |first2=G. |date=2020-02-01 |title=Economics and finance of Small Modular Reactors: A systematic review and research agenda |url=https://www.sciencedirect.com/science/article/pii/S1364032119307270 |journal=Renewable and Sustainable Energy Reviews |volume=118 |pages=109519 |doi=10.1016/j.rser.2019.109519 |s2cid=209778267 |issn=1364-0321|doi-access=free |hdl=11311/1204915 |hdl-access=free }}</ref>

Proponents claim that SMRs would be less expensive due to the use of standardized modules that could be industrially produced off-site in a dedicated factory.<ref name="small-beautiful">{{Cite web|url=https://www.enseccoe.org/data/public/uploads/2020/11/02.-solo-article-lukas-smr-eh-15-web-version-final.pdf|title=Is Small Really Beautiful? The Future Role of Small Modular Nuclear Reactors (SMRs) in the Military|last=Trakimavičius|first=Lukas|website=NATO Energy Security Centre of Excellence|language=en|access-date=2020-12-28}}</ref> SMRs do, however, also have economic disadvantages.<ref name=base_report>{{cite web|title=Small Modular Reactors - Was ist von den neuen Reaktorkonzepten zu erwarten?|periodical=|publisher=|url=https://www.base.bund.de/DE/themen/kt/kta-deutschland/neue_reaktoren/neue-reaktoren_node.html|access-date=|last=Bundesamt für die Sicherheit der nuklearen Entsorgung|date=2021-03-10|language=de|pages=|quote=}}</ref> Several studies suggest that the overall costs of SMRs are comparable with those of conventional large reactors. Moreover, extremely limited information about SMR modules transportation has been published.<ref name="transportation2">{{Cite conference |last1=Mignacca |first1=Benito |last2=Hasan Alawneh |first2=Ahmad |last3=Locatelli |first3=Giorgio |date=27 Jun 2019 |title=Transportation of small modular reactor modules: What do the experts say? |url=https://www.researchgate.net/publication/330823799 |conference=27th International Conference on Nuclear Engineering}}</ref> Critics say that modular building will only be cost-effective for a high number of the same SMR type, given the still remaining high costs for each SMR.<ref>{{Cite journal |last1=Boarin |first1=Sara |last2=Ricotti |first2=Marco E. |date=2014-08-05 |title=An Evaluation of SMR Economic Attractiveness |journal=Science and Technology of Nuclear Installations |language=en |volume=2014 |pages=e803698 |doi=10.1155/2014/803698 |issn=1687-6075 |doi-access=free |hdl=11311/839526 |hdl-access=free }}</ref> A high market share is thus needed to obtain sufficient orders.

=== Contribution to the net zero emissions pathways ===
In her global pathway to reach [[Earth:Net zero emissions|net zero emissions]] by 2050, the [[Organization:International Energy Agency|International Energy Agency]] (IEA) considers that the worldwide nuclear power should be multiplied by two between 2020 and 2050.<ref name="IEA2022">{{cite web | title=Nuclear power can play a major role in enabling secure transitions to low emissions energy systems | website=IEA | date=2022-06-30 | url=https://www.iea.org/news/nuclear-power-can-play-a-major-role-in-enabling-secure-transitions-to-low-emissions-energy-systems | access-date=2023-12-13}}</ref> Antonio Vaya Soler, an expert from the [[Organization:Nuclear Energy Agency|Nuclear Energy Agency]] (NEA), also acknowledges that if the renewable energies are an essential component to fight [[Earth:Global warming|global warming]], they will not be sufficient for achieving the net zero {{CO2|link=carbon dioxide}} emissions targets. To reach the objectives, the nuclear energy capacity should at least be doubled from the current level to be consistent with the net zero pathway.<ref name="VayaSoler2024">{{cite book | first1=Antonio | last1=Vaya Soler | year=2024 | title=Chapter 23 – The future of nuclear energy and small modular reactors. In: Living with Climate Change | page=465–512 | publisher=Elsevier | doi=10.1016/B978-0-443-18515-1.00012-5 | url=https://www.sciencedirect.com/science/article/abs/pii/B9780443185151000125 | ISBN=9780443185151| access-date=2023-12-13}}</ref>

To produce the same electrical power than the {{nowrap|~ 400 large}} nuclear power reactors presently in operation in the world today, BASE, the German Federal Office for the Safety of Nuclear Waste Management also estimates that it would be necessary to build several thousands to tens of thousands SMRs.<ref name="BASE" /><ref name="BASE_report2021">{{cite web | date=10 March 2021 | author=Öko-Institut | title=Sicherheitstechnische Analyse und Risikobewertung einer Anwendung von SMR-Konzepten (Small Modular Reactors) | trans-title=Safety analysis and risk assessment of the application of SMR concepts | website=BASE | url=https://www.base.bund.de/SharedDocs/Downloads/BASE/DE/berichte/kt/gutachten-small-modular-reactors.html;jsessionid=268D8A1B8EE5F6F621FDBCF3A5817292.internet992 | language=de | access-date=2023-12-13}}</ref> 

So, several fleets of SMR reactors of exactly the same type, and industrially manufactured in large series through factory production, should be rapidly and massively deployed worldwide to deliver a sufficient power output to significatively contribute to the net zero emissions of {{CO2}}. The Nuclear Energy Agency (NEA) has launched at the COP 28 a new initiative ''"Accelerating SMRs for Net Zero"'' to foster collaborations between research organizations, nuclear industry, safety authorities, and governments, in order to rapidly reduce carbon emissions for reaching the net zero emissions targets required before 2050 to limit the Earth [[Earth:Global surface temperature|global surface temperature]] increase.<ref name="NEA2023a">{{cite web | title="Accelerating SMRs for Net Zero" initiative launched at COP28 | website=Nuclear Energy Agency (NEA) | date=2023-12-05 | url=https://www.oecd-nea.org/jcms/pl_88887/-accelerating-smrs-for-net-zero-initiative-launched-at-cop28 | access-date=2023-12-13}}</ref><ref name="NEA2023b">{{cite web | title=Accelerating SMRs for Net Zero | website=Nuclear Energy Agency (NEA) | date=2023-12-05 | url=https://www.oecd-nea.org/jcms/pl_88539/accelerating-smrs-for-net-zero | access-date=2023-12-13}}</ref><ref name="NEA2023c">{{cite web | author=Nuclear Energy Agency (NEA) |date=November 2023 | title=Small Modular Reactors (SMRs) for Net Zero | url=https://www.oecd-nea.org/upload/docs/application/pdf/2023-12/smrs_for_net_zero.pdf | access-date=2023-12-13}}</ref>

=== Future challenges ===
Proponents say that nuclear energy with proven technology would be safe; the nuclear industry contends that smaller size will make SMRs even safer than larger conventional plants. Critics say that many more<ref name="BASE" /> small nuclear reactors pose a higher risk, requiring more transportation of [[Physics:Nuclear fuel|nuclear fuel]] and also increasing the production of [[Physics:Radioactive waste|radioactive waste]].<ref name="Krall2022" /> SMRs require new designs with new technology, the safety of which has yet to be proven.

Until 2020, no truly modular SMRs had been commissioned for commercial use.<ref name="Mignacca2">{{Cite journal |last1=Mignacca |first1=Benito |last2=Locatelli |first2=Giorgio |date=1 Nov 2019 |title=Economics and finance of Small Modular Reactors: A systematic review and research agenda |journal=Renewable and Sustainable Energy Reviews |volume=118 |page=109519 |doi=10.1016/j.rser.2019.109519 |doi-access=free|hdl=11311/1204915 |hdl-access=free }}</ref> In May 2020, the first prototype of a [[Physics:Floating nuclear power plant|floating nuclear power plant]] with two 30&nbsp;MW<sub>e</sub> reactors  – the type ''KLT-40'' – started operation in [[Earth:Pevek|Pevek]], Russia.<ref name="klt-40_pris">[https://pris.iaea.org/PRIS/CountryStatistics/ReactorDetails.aspx?current=895 Akademik Lomonosov-1], Power Reactor Information System (PRIS), International Atomic Energy Agency, 2020-09-13.</ref> This concept is based on the design of nuclear [[Engineering:Icebreaker|icebreaker]]s.<ref name="klt40">{{cite web |url=http://www.world-nuclear-news.org/Articles/Russia-connects-floating-plant-to-grid |title=Russia connects floating plant to grid |date=2019-12-19 |website=World Nuclear News|quote=Alexey Likhachov, director general of state nuclear corporation Rosatom, said Akademik Lomonosov had thus becomes the world's first nuclear power plant based on SMR technology to generate electricity.}}</ref> The operation of the first commercial land-based, 125&nbsp;MW<sub>e</sub> demonstration reactor ''ACP100'' (Linglong One) is due to start in China by the end of 2026.<ref name="containment-linglong1"/>

To cope with the 2050 targets of net zero {{CO2}} emissions without wasting time, a rapid and massive deployment of a large number of SMRs (several thousands to tens of thousands of units)<ref name="BASE" /> is critical and represents an unprecedented challenge for the nuclear industry, the safety authorities, and the civil society (acceptance by the public, the politicians, and the governments in the larger countries), in the short time frame considered.

== Designs ==
[[Image:Fission chain reaction.svg|thumb|A nuclear fission chain is required to generate nuclear power.]]
SMRs are envisioned in multiple designs. Some are simplified versions of current reactors, others involve entirely new technologies.<ref>INEA, NEA, IEA. [http://www.nea.fr/ndd/reports/2002/nea3969-innovative-reactor.pdf "Innovative Nuclear Reactor Development: Opportunities for International Co-operation"], [http://www.nea.fr ''OECD Nuclear Energy Agency'']</ref> All proposed SMRs use [[Physics:Nuclear fission|nuclear fission]] with designs including [[Engineering:Thermal-neutron reactor|thermal-neutron reactor]]s and [[Physics:Fast-neutron reactor|fast-neutron reactor]]s.

=== Thermal-neutron reactors ===
Thermal-neutron reactors rely on a [[Physics:Neutron moderator|moderator]] (water, [[Chemistry:Graphite|graphite]], [[Chemistry:Beryllium|beryllium]]...) to slow [[Physics:Neutron|neutron]]s and generally use {{chem|link=Uranium|235|U}} as [[Physics:Fissile material|fissile material]]. Most conventional operating reactors are of this type.

=== Fast reactors ===
[[Physics:Fast-neutron reactor|Fast reactors]] don't use moderators. Instead they rely on the fuel to absorb fast neutrons. This usually means changing the fuel arrangement within the core, or using different fuels. E.g., {{chem|link=Plutonium|239|Pu}} is more likely to absorb a fast neutron than {{chem|235|U}}.

Fast reactors can be [[Engineering:Breeder reactor|breeder reactor]]s. These reactors release enough neutrons to [[Physics:Nuclear transmutation|transmute]] non-fissionable elements into fissionable ones. A common use for a breeder reactor is to surround the core by a "blanket" of {{chem|238|U}}, the most easily available isotope. Once the {{chem|238|U}} undergoes a neutron absorption reaction, it becomes {{chem|239|Pu}}, which can be removed from the reactor during refueling, and subsequently [[Physics:Nuclear reprocessing|reprocessed]] and used as fuel.<ref name="world-nuclear1">Carlson, J. [http://www.world-nuclear.org/info/inf98.html "Fast Neutron Reactors"] {{Webarchive|url=https://web.archive.org/web/20130224035726/http://www.world-nuclear.org/info/inf98.html |date=24 February 2013 }}, [http://world-nuclear.org ''World Nuclear Association'']</ref>

== Technologies ==
[[File:Pumpless light water reactor.jpg|thumb|An example of proposed SMR type: Pumpless light water reactor developed by NuScale Power as mini nuclear reactor.]]

=== Coolant ===
Conventional [[Engineering:Light-water reactor|light-water reactor]]s typically use water as a coolant and neutron moderator.<ref name="nrc-201411052">{{citation |last=Glaser |first=Alexander |title=Small Modular Reactors - Technology and Deployment Choices |date=5 November 2014 |url=https://www.nrc.gov/reading-rm/doc-collections/commission/slides/2014/20141105/glaser-11-05-14.pdf |publisher=NRC |format=presentation}}</ref> SMRs may use water, [[Physics:Liquid metal cooled reactor|liquid metal]], gas and [[Engineering:Molten salt reactor|molten salt]] as coolants.<ref name="world-nuclear22">Wilson, P.D. [http://www.world-nuclear.org/info/inf32.html "Nuclear Power Reactors"] {{Webarchive|url=https://web.archive.org/web/20130212224059/http://www.world-nuclear.org/info/inf32.html |date=12 February 2013 }}, [http://www.world-nuclear.org ''World Nuclear Association'']</ref><ref>{{cite web |author=brian wang |date=13 October 2011 |title=Flibe Energy Liquid Flouride &#91;sic&#93; Thorium Reactor Company |url=http://nextbigfuture.com/2011/10/flibe-energy-liquid-flouride-thorium.html |access-date=18 December 2012 |publisher=Nextbigfuture.com}}</ref> Coolant type is determined based on the reactor type, reactor design, and the chosen application. Large-rated reactors primarily use light water as coolant, allowing for this cooling method to be easily applied to SMRs. [[Chemistry:Helium|Helium]] is often elected as a gas coolant for SMRs because it yields a high plant [[Physics:Thermal efficiency|thermal efficiency]] and supplies a sufficient amount of reactor heat. [[Chemistry:Sodium|Sodium]], [[Chemistry:Lead|lead]], and [[Chemistry:Lead-bismuth eutectic|lead-bismuth eutectic]] (LBE) are liquid metal coolants studied for 4th generation SMRs. There was a large focus on sodium during early work on large-rated reactors which has since carried over to SMRs to be a prominent choice as a liquid metal coolant.<ref name=":24">{{Cite book |last=Carelli |first=Mario D., Ingersoll, D. T. |url=http://worldcat.org/oclc/1222802880 |title=Handbook of small modular nuclear reactors |date=22 October 2020 |publisher=Woodhead |isbn=978-0-12-823917-9 |oclc=1222802880}}</ref> SMRs have lower cooling water requirements, which expands the number of sites where a SMR could be built, including remote areas typically incorporating mining and [[Chemistry:Desalination|desalination]].<ref>{{Cite web |title=Small nuclear power reactors - World Nuclear Association |url=https://www.world-nuclear.org/information-library/nuclear-fuel-cycle/nuclear-power-reactors/small-nuclear-power-reactors.aspx |access-date=2022-02-16 |website=www.world-nuclear.org}}</ref>

=== Thermal/electrical generation ===
Some gas-cooled reactor designs could drive a [[Engineering:Gas turbine|gas turbine]], rather than boiling water, such that thermal energy can be used directly. Heat could also be used in [[Chemistry:Hydrogen production|hydrogen production]] and other industrial operations,<ref name="world-nuclear22"/> such as desalination and the production of [[Chemistry:Petroleum|petroleum]] derivative (extracting oil from oil sands, making [[Chemistry:Coal liquefaction|synthetic oil from coal]], etc.).<ref>[http://www.world-nuclear.org/info/inf116_processheat.html "Nuclear Process Heat for Industry"] {{Webarchive|url=https://web.archive.org/web/20130216022200/http://www.world-nuclear.org/info/inf116_processheat.html |date=16 February 2013 }}, [http://www.world-nuclear.org ''World Nuclear Association'']</ref>

=== Load following ===
SMR designs are generally expected to provide [[Engineering:Base load|base load]] electrical power; some proposed designs are aimed to adjust their power output based on electricity demand.{{citation needed|date=November 2021}}

Another approach, especially for SMRs designed to provide high temperature heat, is to adopt [[Physics:Cogeneration|cogeneration]], maintaining consistent heat output, while diverting otherwise unneeded heat to an auxiliary use. [[Physics:District heating|District heating]], desalination and hydrogen production have been proposed as cogeneration options.<ref name="Cogeneration2">{{Cite journal |last1=Locatelli |first1=Giorgio |last2=Fiordaliso |first2=Andrea |last3=Boarin |first3=Sara |last4=Ricotti |first4=Marco E. |date=1 May 2017 |title=Cogeneration: An option to facilitate load following in Small Modular Reactors |url=http://eprints.whiterose.ac.uk/110233/1/Load%20Following%20by%20Cogeneration%20V27%20to%20deposit.pdf |journal=Progress in Nuclear Energy |volume=97 |pages=153–161 |doi=10.1016/j.pnucene.2016.12.012}}</ref>

Overnight desalination requires sufficient freshwater storage capacity to deliver water at times other than when it is produced.<ref>{{Cite journal |last1=Locatelli |first1=Giorgio |last2=Boarin |first2=Sara |last3=Pellegrino |first3=Francesco |last4=Ricotti |first4=Marco E. |date=1 February 2015 |title=Load following with Small Modular Reactors (SMR): A real options analysis |url=http://eprints.whiterose.ac.uk/91139/1/Accpeted%20version.pdf |journal=Energy |volume=80 |pages=41–54 |doi=10.1016/j.energy.2014.11.040 |hdl-access=free |hdl=11311/881391}}</ref> [[Chemistry:Reverse osmosis|Reverse osmosis]] membrane and thermal [[Chemistry:Evaporator (marine)|evaporators]] are the two main techniques for [[Earth:Seawater|seawater]] desalination. The membrane desalination process uses only electricity to power water pumps and is the most employed of the two methods. In the thermal process, the feed water stream is evaporated in different stages with continuous decreases in pressure between the stages. The thermal process directly uses thermal energy and avoids the conversion of thermal power into electricity. Thermal desalination is further divided into two main technologies: the [[Chemistry:Multi-stage flash distillation|multi-stage flash distillation]] (MSF) and the Multi-Effect Desalination (MED).<ref>{{Cite journal |last1=Locatelli |first1=Giorgio |last2=Boarin |first2=Sara |last3=Pellegrino |first3=Francesco |last4=Ricotti |first4=Marco E. |date=2015 |title=Load following with Small Modular Reactors (SMR): A real options analysis |url=http://dx.doi.org/10.1016/j.energy.2014.11.040 |journal=Energy |volume=80 |pages=41–54 |doi=10.1016/j.energy.2014.11.040 |issn=0360-5442|hdl=11311/881391 |hdl-access=free }}</ref>

== Nuclear safety ==
A report by the German Federal Office for the Safety of Nuclear Waste Management (BASE) considering 136 different historical and current reactors and SMR concepts stated: "Overall, SMRs could potentially achieve safety advantages compared to power plants with a larger power output, as they have a lower radioactive inventory per reactor and aim for a higher safety level especially through simplifications and an increased use of passive systems. In contrast, however, various SMR concepts also favour reduced regulatory requirements, for example, with regard to the required degree of redundancy or diversity in safety systems. Some developers even demand that current requirements be waived, for example in the area of internal accident management or with reduced planning zones, or even a complete waiver of external emergency protection planning. Since the safety of a reactor plant depends on all of these factors, based on the current state of knowledge it is not possible to state, that a higher safety level is achieved by SMR concepts in principle."<ref name="base_sicherheit">[https://www.base.bund.de/SharedDocs/Downloads/BASE/DE/berichte/kt/gutachten-small-modular-reactors.html ''Sicherheitstechnische Analyse und Risikobewertung einer Anwendung von SMR-Konzepten (Small Modular Reactors)'']. BASE, März 2021</ref><ref name="fortschritt_sz-2021">[https://www.sueddeutsche.de/wissen/atomenergie-kernkraft-atommuell-gates-reaktoren-smr-oeko-institut-gutachten-atomkraftwerk-1.5229758 ''Für die Zukunft zu spät.''] Süddeutsche Zeitung, 9. März 2021</ref><ref name=base_report/>

Negative temperature coefficients in the moderators and the fuels keep the fission reactions under control, causing the reaction to slow as temperature increases.<ref>{{harvnb|DOE-HDBK-1019|1993|pp=23–29}}</ref>

Some SMR designs proposes cooling systems only based on thermoconvection – natural circulation – to eliminate cooling pumps that could break down. Convection can keep removing decay heat after reactor shutdown. However, some SMRs may need an active cooling system to back up the passive system, increasing cost.<ref name="UCS1" />

Some SMR designs feature an integral design of which the primary reactor core, steam generator and the pressurizer are integrated within the sealed reactor vessel. This integrated design allows for the reduction of a possible accident as contamination leaks could be contained. In comparison to larger reactors having numerous components outside the reactor vessel, this feature increases the safety by decreasing the risks of an uncontained accident. Some SMR designs also envisage to install the reactor and the spent-fuel storage pools underground.<ref name=":14">{{Cite book |first=Nick |last=Cunningham |url=http://worldcat.org/oclc/813390081 |title=Small modular reactors : a possible path forward for nuclear power |date=2012 |publisher=American Security Project |oclc=813390081}}</ref>

== Radioactive waste ==
The backend of the nuclear fuel cycle of SMR is a complex and challenging issue remaining disputed. The quantity and the radiotoxicity of the radioactive waste produced by SMR mainly depend on their design and the related fuel cycle. As the notion of SMR encompasses a broad spectrum a nuclear reactor types, no simple answer can be easily given to the question. SMR may comprise small light water reactors of third generation as well as small fast neutron reactors of fourth generation. 

Often, the startup companies developing unconventional SMR prototypes advocate waste reduction as an advantage of the proposed solution and even sometimes claim that their technology could eliminate the need for a deep geological repository to dispose of high-level and long-lived radioactive waste. This is especially the case for companies studying fast neutron reactors of 4th generation (molten salts reactors, metal-cooled reactors ([[Engineering:Sodium-cooled fast reactor|sodium-cooled fast reactor]], or [[Chemistry:Lead-cooled fast reactor|lead-cooled fast reactor]]).

Fast breeder reactors "burn" {{chem|235|U|link=Uranium-235}} (0.7% of [[Physics:Natural uranium|natural uranium]]), but also convert fertile materials such as {{chem|238|U|link=Uranium-238}} (99.3% of natural uranium) into fissile {{chem|239|Pu|link=Plutonium-239}} that can be used as nuclear fuel.<ref name="world-nuclear1"/>

The [[Engineering:Traveling wave reactor|traveling wave reactor]] proposed by [[Company:TerraPower|TerraPower]] is aimed to immediately "burn" the fuel that it breeds without requiring its removal from the reactor core and its further reprocessing.<ref>Wald, M. [http://www.technologyreview.com/energy/22114/?a=f "TR10: Traveling Wave Reactor"] {{Webarchive|url=https://web.archive.org/web/20111011040125/http://www.technologyreview.com/energy/22114/?a=f |date=11 October 2011 }}, [http://www.technologyreview.com ''Technology Review'']</ref>

The design of some SMR reactors is based on the [[Physics:Thorium fuel cycle|thorium fuel cycle]], which is considered by their promotors as a way to reduce the long-term waste radiotoxicity compared to the uranium cycle.<ref>Section 5.3, WASH 1097 "The Use of Thorium in nuclear power reactors", available as a PDF from Liquid-Halide Reactor Documents database: http://www.energyfromthorium.com/pdf/</ref> However, using the thorium cycle also presents big operational challenges because of the production and the use of {{chem|232|U|link=Uranium-232}} and long-lived fertile {{chem|233|U|link=Uranium-233}}, both radioisotopes emitting strong [[Physics:Gamma ray|gamma ray]]s. So, the presence of these radionuclides seriously complicates the radiation shielding of the fresh nuclear fuel and the long-term storage and disposal of their spent nuclear fuel. 

A study of 2022 made by Krall, Macfarlane and Ewing is more critical and reports that some types of SMR could produce more waste per unit of output power than conventional reactors, in some cases more than 5&times; the number of [[Physics:Spent nuclear fuel|spent fuel]] per kilowatt, and as much as 35&times; for other waste produced by [[Physics:Neutron activation|neutron activation]], such as [[Physics:Neutron activation|activated]] steel and [[Chemistry:Graphite|graphite]].<ref name ="Barber2022">{{Cite magazine |last=Barber |first=Gregory |title=Smaller reactors may still have a big nuclear waste problem |language=en-US |magazine=Wired |url=https://www.wired.com/story/smaller-reactors-may-still-have-a-big-nuclear-waste-problem/ |access-date=2022-08-03 |issn=1059-1028}}</ref><ref name="Vaughan2022">{{Cite magazine | last=Vaughan | first=Adam | title=Mini nuclear power stations may produce more waste than large ones | website=New Scientist | date=2022-05-30 | url=https://www.newscientist.com/article/2322252-mini-nuclear-power-stations-may-produce-more-waste-than-large-ones/ | access-date=2023-12-03}}</ref><ref name="Stanford_University_2022">{{cite web | author=Stanford University | title=Small modular reactors produce high levels of nuclear waste | website=Stanford News | date=2022-05-30 | url=https://news.stanford.edu/2022/05/30/small-modular-reactors-produce-high-levels-nuclear-waste/#:~:text=%E2%80%9CWe%20found%20that%20small%20modular,%2C%20which%20will%20be%20expensive.%E2%80%9D | access-date=2023-12-04}}</ref><ref name="Krall2022">{{Cite journal |last1=Krall |first1=Lindsay M. |last2=Macfarlane |first2=Allison M. |last3=Ewing |first3=Rodney C. |date=2022-06-07 |title=Nuclear waste from small modular reactors |journal=Proceedings of the National Academy of Sciences |language=en |volume=119 |issue=23 |pages=e2111833119 |doi=10.1073/pnas.2111833119 |issn=0027-8424 |pmc=9191363 |pmid=35639689|bibcode=2022PNAS..11911833K }}</ref>

These authors have identified the neutron leakage as the first issue for SMRs because they have a higher surface area with respect to their core volume. They have calculated that the neutron leakage rates are much higher for SMRs, because in smaller reactor cores, emitted neutrons have fewer chances to interact with the fissile atoms present in the fuel and to produce nuclear fission. Instead, neutrons exit the reactor core without interacting with the nuclear fuel, and they are absorbed outside the core by the materials used for the [[Physics:Neutron reflector|neutron reflector]]s and the shielding (thermal and gamma shields), turning them as radioactive waste ([[Physics:Neutron activation|activated]] steel and [[Chemistry:Graphite|graphite]]). 

Reactor designs using liquid metal coolants (molten sodium, lead, lead-bismuth eutectic, LBE) also become radioactive and contains activated impurities. 

Another issue pinpointed by Krall ''et al.'' (2022)<ref name="Krall2022" /> related to the higher neutron leakage in SMR is that a lower fraction of their nuclear fuel is consumed, leading to a lower [[Engineering:Burnup|burnup]] and to more [[Physics:Fissile material|fissile material]]s left over in their [[Physics:Spent nuclear fuel|spent fuel]], therefore increasing the waste volume. To sustain the nuclear chain reactions in the core of a smaller reactor, an alternative is to use nuclear fuel more enriched in {{chem|235|U|link=Uranium-235}}. This could increase the risks of nuclear proliferation and could require more stringent safeguard measures to prevent it (see also [[Physics:IAEA safeguards|IAEA safeguards]]). 

If higher concentrations of fissile materials subsist in the spent fuel, the [[Physics:Critical mass|critical mass]] needed to sustain a nuclear chain reaction is also lower. As a direct consequence, the number of spent fuels present in a waste canister will also be lower and a larger number of canisters and overpacks will be necessary to avoid [[Physics:Criticality accident|criticality accident]]s and to guarantee [[Physics:Nuclear criticality safety|nuclear criticality safety]] in a deep geological repository. This also contributes to increase the total waste volume and the number of disposal galleries in a geological repository. 

Given the potential technical and economical importance of SMRs to supply zero-carbon electrical energy needed to fight [[Earth:Climate change|climate change]] and the long-term and social relevance of the study to adequately manage and dispose of radioactive waste without imposing a negative burden onto the future generations, the publication of Krall ''et al.'' (2022) in the prestigious PNAS journal has attracted many reactions ranging from criticisms on the quality of their data and hypotheses<ref name="NeutronBytes2022">{{cite web | title=Stanford's questionable study on spent nuclear fuel for SMRs | website=Neutron Bytes | date=2022-05-31 | url=https://neutronbytes.com/2022/05/31/stanfords-questionable-study-on-spent-nuclear-fuel-for-smrs/ | access-date=2023-12-03}}</ref> to international debates on radioactive waste produced by SMRs and their decommissioning.<ref name="NEA2022">{{cite web | title=Management of spent fuel, radioactive waste and decommissioning in SMRs or advanced reactor technologies. 7-10 November 2022, Ottawa, Canada. Workshop programme | url=https://www.oecd-nea.org/upload/docs/application/pdf/2022-11/smr_programme_final.pdf | access-date=2023-12-03}}</ref>

In an interview with François Diaz-Maurin, the associate editor of the [[Physics:Bulletin of the Atomic Scientists|Bulletin of the Atomic Scientists]], Lindsay Krall, the lead author of the study and a former MacArthur postdoctoral fellow at Stanford's Center for International Security and Cooperation (CISAC) answered to questions and criticisms, amongst others, those raised by the NuScale reactor company.<ref name="Diaz-Maurin2022">{{cite web | last=Diaz-Maurin | first=François | title=Interview: Small modular reactors get a reality check about their waste | website=Bulletin of the Atomic Scientists | date=2022-06-17 | url=https://thebulletin.org/2022/06/interview-small-modular-reactors-get-a-reality-check-about-their-waste/ | access-date=2023-12-03}}</ref> One of the main concerns Krall expressed in this interview is that: 
: "There's definitely a disconnect between the people working on the back end of the fuel cycle—especially with geologic repository development—and those actually designing reactors. And, there is not a lot of motivation for these reactor designers to think about the geologic disposal aspects because the NRC's new reactor design certification application does not have a chapter on geologic disposal..."

The critical study of Krall ''et al.'' (2022) has the merit to have raised relevant questions that cannot be ignored by reactor designers, or decision-makers, and to have triggered open and fresh discussions on important outcomes for SMRs and radwaste management in general. Amongst the various types of SMR projects initiated today by many start-up companies, only those correctly addressing these questions and really contributing to minimize the radioactive waste they produce have a chance to be supported by the public and governmental organisations (nuclear safety authorities and radioactive waste management organisations) and their research to be funded by long-term national policies. 

The high diversity of SMR reactors and their respective fuel cycles may also require more diverse waste management strategy to recycle, or to safely dispose, their nuclear waste.<ref name ="Barber2022" /><ref name="Krall2022" /> A larger number of spent fuel types will be more difficult to manage than only one type as it is presently the case with light water reactors only. 

As previously stressed by Krall and Macfarlane (2018),<ref name="Krall_Macfarlane_2018">{{cite journal | first1=Lindsay M. | last1=Krall | first2=Allison M. | last2=Macfarlane | title=Burning waste or playing with fire? Waste management considerations for non-traditional reactors | journal=Bulletin of the Atomic Scientists | publisher=Routledge | date=2018-08-31 | volume=74 | issue=5 | pages=326–334 | url=https://www.tandfonline.com/doi/full/10.1080/00963402.2018.1507791 | access-date=2023-12-03 | doi=10.1080/00963402.2018.1507791 | bibcode=2018BuAtS..74e.326K | s2cid=149901270 }}</ref> some types of SMR spent fuels, or coolants, (highly reactive and corrosive uranium fluoride ({{chem2|UF4}}) from [[Engineering:Molten salt reactor|molten salt reactor]]s, or pyrophoric sodium from liquid metal cooled fast breeders) cannot be directly disposed of in a deep geologic repository because of their chemical reactivity in the underground environment (deep [[Earth:Clay|clay]] formations, crystalline rocks, or rock salt). To avoid to exacerbate spent fuel storage and disposal issues it will be mandatory to reprocess and to condition them in an appropriate and safe way before final geological disposal. 

A study made by Keto ''et al.'' (2022) at the VTT Technical Research Centre of Finland also addressed the management of [[Physics:Spent nuclear fuel|spent nuclear fuel]] (SNF) and low- and intermediate-level waste (LILW) from a possible future deployment of SMRs in {{wipe|Finland}}. It also indicates that larger masses (per GWe-year) of SNF and other HLW and larger volumes (per GWe-year) of LLW would be produced by a light water SMR compared to a large NPP.<ref name="Keto2022">{{cite web | last1=Keto | first1=Paula | last2=Juutilainen | first2=Pauli | last3=Schatz | first3=Timothy | last4=Naumer | first4=Sami | last5=Häkkinen | first5=Silja | title=Waste Management of Small Modular Nuclear Reactors in Finland | publisher=VTT Technical Research Centre of Finland | date=2022-02-28 | url=https://cris.vtt.fi/en/publications/waste-management-of-small-modular-nuclear-reactors-in-finland | access-date=2023-12-15}}</ref> 

A report by the German Federal Office for the Safety of Nuclear Waste Management (BASE) found that extensive interim storage and fuel transports are still required for SMRs. A deep geological repository is still unavoidable in any case because of the presence of highly mobile long-lived fission products that, due to their too low [[Physics:Neutron cross section|neutron cross section]], cannot be efficiently [[Physics:Nuclear transmutation|transmuted]], as it is the case with dose-dominating radionuclides such as  {{chem|129|I|link=Iodine-129}}, {{chem|99|Tc|link=Technetium-99}} and {{chem|79|Se|link=Selenium-79}} ([[Chemistry:Solubility|soluble]] anions that are not [[Physics:Sorption|sorbed]] onto the negatively charged minerals and are not retarded in geological media).<ref name=base_report />

== Nuclear proliferation ==
Nuclear proliferation, or the use of nuclear materials to create weapons, is a concern for small modular reactors. As SMRs have lower generation capacity and are physically smaller, they are intended to be deployed in many more locations than conventional plants.<ref name="auto1b2">{{Cite web |last=Trakimavičius |first=Lukas |date=Nov 2020 |title=Is Small Really Beautiful?The Future Role of Small Modular Nuclear Reactors (SMRs) In The Military |url=https://www.enseccoe.org/data/public/uploads/2020/11/02.-solo-article-lukas-smr-eh-15-web-version-final.pdf |website=NATO Energy Security Centre of Excellence |language=en}}</ref> SMRs are expected to substantially reduce staffing levels. The combination creates physical protection and security concerns.<ref name="areva-20100618"/><ref name="nrc-201411052"/>

SMRs can be designed to use unconventional fuels allowing for higher [[Engineering:Burnup|burnup]] and longer fuel cycles.<ref name=":1" /> Longer refueling intervals could contribute to decrease the proliferation risks. Once the fuel has been [[Biology:Irradiation|irradiated]], the mixture of fission products and fissile materials is highly radioactive and requires special handling, preventing casual theft.

Contrasting to conventional large reactors, SMRs can be adapted to be installed in a sealed underground chamber; therefore, "reducing the vulnerability of the reactor to a terrorist attack or a natural disaster".<ref name=":14"/> New SMR designs enhance the proliferation resistance, such as those from the reactor design company Gen4. These models of SMR offer a solution capable of operating sealed underground for the life of the reactor following installation.<ref name=":14" /><ref name="Ingersoll 2009 589–603"/>

Some SMR designs are designed for one-time fueling. This improves proliferation resistance by eliminating on-site nuclear fuel handling and means that the fuel can be sealed within the reactor. However, this design requires large amounts of fuel, which could make it a more attractive target. A 200 MWe 30-year core life light water SMR could contain about 2.5 tonnes of plutonium at end of life.<ref name="nrc-201411052" />

Furthermore, many SMRs offer the ability to go periods of greater than 10 years without requiring any form of refueling therefore improving the proliferation resistance as compared to conventional large reactors of which entail refueling every 18–24 months.<ref name=":14" />

Light-water reactors designed to run on [[Chemistry:Thorium|thorium]] offer increased proliferation resistance compared to the conventional uranium cycle, though molten salt reactors have a substantial risk.<ref name="U‐232 and the proliferation‐resistance of U‐233 in spent fuel2">{{Cite journal |last1=Kang |first1=J. |last2=Von Hippel |first2=F. N. |year=2001 |title=U‐232 and the proliferation‐resistance of U‐233 in spent fuel |journal=Science & Global Security |volume=9 |issue=1 |pages=1–32 |bibcode=2001S&GS....9....1K |doi=10.1080/08929880108426485 |s2cid=8033110}} {{cite web |title=Archived copy |url=http://www.torium.se/res/Documents/9_1kang.pdf |url-status=dead |archive-url=https://web.archive.org/web/20141203135336/http://www.torium.se/res/Documents/9_1kang.pdf |archive-date=3 December 2014 |access-date=2 March 2015}}</ref><ref>{{Cite journal |last1=Ashley |first1=Stephen |year=2012 |title=Thorium fuel has risks |journal=Nature |volume=492 |issue=7427 |pages=31–33 |bibcode=2012Natur.492...31A |doi=10.1038/492031a |pmid=23222590 |s2cid=4414368|doi-access=free }}</ref>

SMRs are transported from the factories without fuel, as they are fueled on the ultimate site, except some [[Physics:Nuclear microreactor|microreactors]].<ref>{{cite web|author=Office of Nuclear Energy |url= https://www.energy.gov/ne/articles/what-nuclear-microreactor |title=  What is a Nuclear Microreactor? |publisher=Office of Nuclear Energy |date= |accessdate=2022-08-18}}</ref> This implies an independent transport of the fuel to the site and therefore increases the risk of nuclear proliferation.

== Licensing process ==
Licensing is an essential process required to guarantee the safety, security and safeguards of a new nuclear installation.<ref name="3S_Risk_Analysis">{{cite web | last1=Williams | first1=Adam David | last2=Osborn | first2=Douglas | last3=Cohn | first3=Brian | year=2019 | title=Security Safety and Safeguards (3S) risk analysis for small modular reactors. Report No. SAND2019-6657C. Sandia National Laboratory (SNL-NM), Albuquerque, New mexico (United States) | website=OSTI.GOV | osti=1640767 | url=https://www.osti.gov/biblio/1640767 | access-date=2023-12-07}}</ref> Only [[Company:NuScale Power|NuScale Power]]'s VOYGR SMR is fully licensed for use in the United States.<ref>{{cite web |url=https://www.energy.gov/ne/articles/nrc-approves-first-us-small-modular-reactor-design |title=NRC Approves First U.S. Small Modular Reactor Design|date=September 2, 2020 |website=energy.gov |publisher=Department of Energy |access-date=16 December 2023}}</ref> However, not all countries follow the NRC or IAEA licensing standards. In the United States and IAEA adhering countries, the licensing is based on a rigorous, independent analysis and reviewing work of all structures, systems and components critical for the nuclear safety under normal and accidental conditions on the whole service life of the installation including the long-term management of radioactive waste.<ref name="CNSC2016">{{cite web | title=DIS-16-04, Small Modular Reactors: Regulatory Strategy, Approaches and Challenges | website=Canadian Nuclear Safety Commission | date=2016-05-30 | url=https://nuclearsafety.gc.ca/eng/acts-and-regulations/consultation/comment/d-16-04/index.cfm | access-date=2023-12-07}}</ref> Licensing is based on the examination and scrutiny of the risk assessment studies and safety files elaborated by the fabricant and the exploitant of the SMR in the frame of the safety case they have to submit to the safety authority (regulatory body) when applying for a licence to construct and safely exploit the installation.<ref name="Pistner2021">{{cite web | last1=Pistner | first1=Christoph | last2=Englert | first2=Matthias | last3=Wealer | first3=Ben | last4=Hirschhausen | first4=Christian von | last5=Donderer | first5=Richard | title=Safety analysis and risk assessment of an application of SMR concepts (Small Modular Reactors) | website=INIS | date=2021-03-01 | url=https://inis.iaea.org/search/search.aspx?orig_q=RN:52097919 | access-date=2023-12-07}}</ref> For NRC and IAEA licensing, the safety and feasibility cases of nuclear installations have to take into account all processes and elements important for the operational safety, its security (access protection), the nuclear safeguard (risk of proliferation), the proper conditioning of radioactive waste under a stable physico-chemical form, and the long-term safety related to the final disposal of the different types of radwaste produced, including all the waste produced during dismantling operations after decommissioning of the installation.<ref name="CNSC2016" /><ref name="STUK2020">{{cite web | author=Ahonen, E., Heinonen, J., Lahtinen, N., Tuomainen, M., & Lång, O. | year=2020 | title=Preconditions for the safe use of small modular reactors: Outlook for the licensing system (STUK, Finland) | url=https://www.julkari.fi/bitstream/handle/10024/139290/STUK_Preconditions%20for%20the%20safe%20use%20of%20small%20modular%20reactors.pdf?sequence=1&isAllowed=y | website=stuk.fi | access-date=2023-12-07}}</ref><ref name="WENRA2021">{{cite web | author= WENRA RHWG | date=12 January 2021 | title=Applicability of the safety objectives to SMRs | url=https://www.wenra.eu/sites/default/files/publications/WENRA_RHWG_Report_on_applicability_of_safety_objectivers_to_SMR.PDF | website=wenra.eu | access-date=2023-12-07}}</ref> A particularly important point of attention for the backend of the [[Physics:Nuclear fuel cycle|nuclear fuel cycle]] is to avoid to producing poorly conditioned waste, or waste types without sustainable final destination or susceptible to generating unexpected reprocessing and disposal costs. 

The most common licensing process, applied by existing commercial reactors, is for the operation of light water reactors ([[Engineering:Pressurized water reactor|PWR]] and [[Engineering:Boiling water reactor|BWR]]). Early designs date back to the 1960s and 1970s during the construction of the nuclear reactor fleet currently in service. Some adaptations of the original licensing process by the US's Nuclear Regulatory Commission (NRC) have been repurposed to better correspond to the specific characteristics and needs of the deployment of SMR units.<ref>{{Cite journal |last1=Sainati |first1=Tristano |last2=Locatelli |first2=Giorgio |last3=Brookes |first3=Naomi |date=15 March 2015 |title=Small Modular Reactors: Licensing constraints and the way forward |url=http://eprints.whiterose.ac.uk/91108/1/Accepted%20version.pdf |journal=Energy |volume=82 |pages=1092–1095 |doi=10.1016/j.energy.2014.12.079}}</ref> In particular, the US Nuclear Regulatory Commission process for [[Physics:Nuclear licensing|licensing]] has focused mainly on conventional reactors. Design and safety specifications, human and organizational factors (including staffing requirements) have been developed for reactors with electrical output of more than 700&nbsp;MWe.<ref>{{cite web |last1=Rysavy |first1=Charles F. |last2=Rhyne |first2=Stephen K. |last3=Shaw |first3=Roger P. |title=Small Modular Reactors |url=http://apps.americanbar.org/environ/committees/nuclearpower/docs/SMR-Dec_2009.pdf |website=American Bar Association |department=Special Committee on Nuclear Power, Section of Environment, Energy, and Resources |archive-url=https://web.archive.org/web/20160304194918/http://apps.americanbar.org/environ/committees/nuclearpower/docs/SMR-Dec_2009.pdf |archive-date=March 4, 2016 |pages=1-3 |date=December 2009 |url-status=dead}}</ref><ref>{{cite web |last1=Smith |first1=Tyson |department=Section of Environment, Energy, and Resources |title=Special Committee on Nuclear Power, Message From The Chair |url=http://apps.americanbar.org/dch/committee.cfm?com=NR601577 |website=American Bar Association |archive-url=https://web.archive.org/web/20120609132032/http://apps.americanbar.org/dch/committee.cfm?com=NR601577 |archive-date=June 9, 2012 |date=May 25, 2012 |url-status=dead}}</ref>

To ensure adequate guidelines for the nuclear safety, while helping the licensing process, the IAEA has encouraged the creation of a central licensing system for SMRs.<ref>{{Citation |last=Black |first=R.L. |title=Licensing of small modular reactors (SMRs) |date=2015 |url=http://dx.doi.org/10.1533/9780857098535.3.279 |work=Handbook of Small Modular Nuclear Reactors |pages=279–292 |publisher=Elsevier |doi=10.1533/9780857098535.3.279 |isbn=9780857098511 |access-date=2022-05-01}}</ref> A workshop in October 2009 and another in June 2010 considered the topic, followed by an US congressional hearing in May 2010. 

The NRC and the United States Department of Energy) are working to define SMR licensing. The challenge of facilitating the development of SMRs is to prevent a weakening of the safety regulations: the risk of lightened regulations adopted more rapidly is to lower the safety characteristics of SMRs.<ref>{{Cite web |title=Advanced Small Modular Reactors (SMRs) |url=https://www.energy.gov/ne/nuclear-reactor-technologies/small-modular-nuclear-reactors |access-date=2 April 2019 |website=Energy.gov |language=en}}</ref><ref name="smallBeauty2">{{Cite web |date=2013 |title=Small isn't always beautiful |url=https://www.ucsusa.org/sites/default/files/legacy/assets/documents/nuclear_power/small-isnt-always-beautiful.pdf |access-date=2 April 2019 |publisher=Union of Concerned Scientists |archive-date=25 September 2019 |archive-url=https://web.archive.org/web/20190925220106/https://www.ucsusa.org/sites/default/files/legacy/assets/documents/nuclear_power/small-isnt-always-beautiful.pdf |url-status=dead}}</ref><ref name="UCS2013">{{cite web | title=Small modular nuclear reactors won’t solve nuclear power’s safety, security and cost problems, new report finds | website=Union of Concerned Scientists | date=2013-09-26 | url=https://www.ucsusa.org/about/news/nuclear-powers-safety-security-and-cost-problems | access-date=2023-12-27}}</ref> While deploying identical systems built in manufacturing plants with an improved quality control can be considered an advantage, SMRs remain nuclear reactors with a very high [[Physics:Energy density|energy density]] and their smaller size is not ''per se'' an intrinsic  guarantee for a better safety. Any severe accident with external radioactive contamination release could have potential serious consequences not so different from that of a large LWR reactor. It would also probably signify the final rejection of [[Physics:Nuclear power|nuclear energy]] by the public and the end of the nuclear industry. The potential "proliferation" of large SMR fleets and the high diversity of their design also complicate the licensing process. The nuclear safety cannot be sacrificed for industrial or economical interests and the risk of nuclear accident increases with the number of reactors in service, small or large unit. 

The U.S. Advanced Reactor Demonstration Program was expected to help license and build two prototype SMRs during the 2020s, with up to $4 billion of government funding.<ref name="science-202005202">{{cite news |last=Cho |first=Adrian |date=20 May 2020 |title=U.S. Department of Energy rushes to build advanced new nuclear reactors |magazine=Science |url=https://www.science.org/content/article/us-department-energy-rushes-build-advanced-new-nuclear-reactors |access-date=21 May 2020}}</ref>

== Flexibility ==
Small nuclear reactors, in comparison to conventional nuclear power plants, offer potential advantages related to the flexibility of their modular construction.<ref name=":14"/> It would be possible to incrementally connect additional units to the grid in the event electrical load increases. Additionally, this flexibility in a standardized SMRs design revolving around modularity could allow for a faster production at a decreasing cost following the completion of the first reactor on site.<ref name=":14"/><ref name="Ingersoll 2009 589–603">{{Cite journal |last=Ingersoll |first=D.T. |date=2009 |title=Deliberately small reactors and the second nuclear era |url=http://dx.doi.org/10.1016/j.pnucene.2009.01.003 |journal=Progress in Nuclear Energy |volume=51 |issue=4–5 |pages=589–603 |doi=10.1016/j.pnucene.2009.01.003 |issn=0149-1970}}</ref>

The hypothesised flexibility and modularity of SMR is intended to allow additional power generation capability to be installed at existing power plants. A site could host several SMRs, one going off-line for refueling while the other reactors stay online as it is presently already the case for conventional larger reactors.<ref name=":14"/>

When electrical energy is not needed, some SMR designs foresee the direct use of thermal energy, minimizing so the energy loss. This includes "[[Chemistry:Desalination|desalination]], industrial processes, [[Chemistry:Hydrogen production|hydrogen production]], [[Engineering:Shale oil extraction|shale oil recovery]], and [[Physics:District heating|district heating]]", uses for which the present conventional larger reactors are not designed.<ref name=":14"/><ref>{{Cite journal |last1=Locatelli |first1=Giorgio |last2=Fiordaliso |first2=Andrea |last3=Boarin |first3=Sara |last4=Ricotti |first4=Marco E. |date=2017 |title=Cogeneration: An option to facilitate load following in Small Modular Reactors |url=http://dx.doi.org/10.1016/j.pnucene.2016.12.012 |journal=Progress in Nuclear Energy |volume=97 |pages=153–161 |doi=10.1016/j.pnucene.2016.12.012 |issn=0149-1970|hdl=11311/1046551 |hdl-access=free }}</ref>

== Economics ==
[[File:Diagram of a NuScale reactor.jpg|thumb|A diagram of the NuScale Power Module reactor (50 MWe). The NuScale Power Module is the first SMR approved for commercial use in the United States. In 2023, plans to build the first NuScale VOYGR plant in Idaho, known as the Carbon Free Power Project, were scrapped due to excessive increases in power generation costs.<ref name=eenews-20231109 /> Although the project cancelation represents a setback for the US nuclear industry, NuScale has three new projects planned in the US and five more in Eastern Europe.]] 
A key driver of interest in SMRs is the claimed [[Finance:Economies of scale|economies of scale]] in production, due to volume manufacture in an offsite factory. Some studies instead find the capital cost of SMRs to be equivalent to larger reactors.<ref>{{Cite journal |last1=Carelli |first1=Mario |last2=Petrovic |first2=B |last3=Mycoff |first3=C |last4=Trucco |first4=Paolo |last5=Ricotti |first5=M.E. |last6=Locatelli |first6=Giorgio |date=1 January 2007 |title=Economic comparison of different size nuclear reactors |url=https://www.researchgate.net/publication/228463939 |journal=Simposio LAS/ANS 2007 |via=ResearchGate}}</ref> Substantial capital is needed to construct the factory – ameliorating that cost requires significant volume, estimated to be 40–70 units.<ref>{{cite news |last1=Harrabin |first1=Roger |date=23 March 2016 |title=The nuclear industry: a small revolution |work=BBC News |publisher=British Broadcasting Corporation |url=https://www.bbc.co.uk/news/business-35863846 |access-date=3 April 2016}}</ref><ref name="sciencedirect.com2">{{Cite journal |last1=Mignacca |first1=Benito |last2=Locatelli |first2=Giorgio |last3=Sainati |first3=Tristano |date=20 Jun 2020 |title=Deeds not words: Barriers and remedies for Small Modular nuclear Reactors |journal=Energy |volume=206 |page=118137 |doi=10.1016/j.energy.2020.118137 |doi-access=free|hdl=11311/1204935 |hdl-access=free }}</ref>

Another potential advantage is that a future power station using SMRs can begin with a single module and expand by adding modules as demand grows. This reduces startup costs associated with conventional designs.<ref>{{Cite journal|last1=Mignacca|first1=B.|last2=Locatelli|first2=G.|date=2020-02-01|title=Economics and finance of Small Modular Reactors: A systematic review and research agenda|journal=Renewable and Sustainable Energy Reviews|language=en|volume=118|pages=109519|doi=10.1016/j.rser.2019.109519|issn=1364-0321|doi-access=free|hdl=11311/1204915|hdl-access=free}}</ref> Some SMRs also have a [[Engineering:Load-following power plant|load-following]] design such that they could produce less electricity when demand is low.

According to a 2014 study of electricity production in decentralized microgrids, the total cost of using SMRs for electricity generation would be significantly lower compared to the total cost of offshore wind power, [[Physics:Solar thermal energy|solar thermal energy]], [[Biology:Biomass (energy)|biomass]], and [[Physics:Photovoltaic system|solar photovoltaic]] electricity generation plants.<ref name=":03">{{Cite journal |last1=Islam |first1=Md. Razibul |last2=Gabbar |first2=Hossam A. |date=2014-06-06 |title=Study of small modular reactors in modern microgrids |journal=International Transactions on Electrical Energy Systems |volume=25 |issue=9 |pages=1943–1951 |doi=10.1002/etep.1945 |issn=2050-7038 |doi-access=free}}</ref>

Construction costs per SMR reactor were claimed in 2016 to be less than that for a conventional nuclear plant, while exploitation costs might be higher for SMRs due to low scale economics and the higher number of reactors. SMR staff operating costs per unit output can be as much as 190% higher than the fixed operating cost of fewer large reactors.<ref name="eysmr-2016032">{{cite report |url=https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/665300/TEA_Projects_5-7_-_SMR_Cost_Reduction_Study.pdf |title=Small modular reactors - Can building nuclear power become more cost-effective? |date=March 2016 |publisher=gov.uk |page=38 |access-date=29 February 2020 |work=Ernst & Young}}</ref> Modular building is a very complex process and there is "extremely limited information about SMR modules transportation", according to a 2019 report.<ref name="transportation2"/>

A production cost calculation done by the German Federal Office for the Safety of Nuclear Waste Management (BASE), taking into account economies of scale and learning effects from the nuclear industry, suggests that an average of 3,000 SMR would have to be produced before SMR production would be worthwhile. This is because the construction costs of SMRs are relatively higher than those of large nuclear power plants due to the low electrical output.<ref name="base_report2">{{cite web |last=Bundesamt für die Sicherheit der nuklearen Entsorgung |date=2021-03-10 |title=Small Modular Reactors - Was ist von den neuen Reaktorkonzepten zu erwarten? |url=https://www.base.bund.de/DE/themen/kt/kta-deutschland/neue_reaktoren/neue-reaktoren_node.html |access-date= |publisher= |pages= |language=de |quote= |periodical=}}</ref>

In 2017, an Energy Innovation Reform Project (EIRP) study of eight companies looked at reactor designs with capacity between 47.5 MWe and 1,648 MWe.<ref>{{Cite web |last=EIRP |date=2017-07-01 |title=What Will Advanced Nuclear Power Plants Cost? |url=https://www.innovationreform.org/2017/07/01/will-advanced-nuclear-power-plants-cost/ |access-date=2020-11-03 |website=Energy Innovation Reform Project |language=en-US}}</ref> The study reported average capital cost of $3,782/kW, average operating cost total of $21/MWh and levelized cost of electricity (LCOE) of $60/MWh.

In 2020, [[Organization:Energy Impact Center|Energy Impact Center]] founder Bret Kugelmass claimed that thousands of SMRs could be built in parallel, "thus reducing costs associated with long borrowing times for prolonged construction schedules and reducing risk premiums currently linked to large projects."<ref name="reutersevents.com2">{{cite news |url=https://www.reutersevents.com/nuclear/industry-heads-warn-nuclear-costs-must-be-slashed |title=Industry heads warn nuclear costs must be slashed |last=Day |first=Paul |publisher=Reuters |date=21 July 2020 |access-date=25 January 2023}}</ref> [[Company:GE Hitachi Nuclear Energy|GE Hitachi Nuclear Energy]] Executive Vice President Jon Ball agreed, saying the modular elements of SMRs would also help reduce costs associated with extended construction times.<ref name="reutersevents.com2" />

In October 2023, an academic paper published in ''Energy'' collated the basic economic data of 19 more developed SMR designs, and modeled their costs in a consistent manner. A Monte Carlo simulation showed that none were profitable or economically competitive. For the closer to market PWR SMRs the median LCOEs ranged from $218/MWh to $614/MWh (in 2020 US dollars), with lower first quartile estimates from $188/MWh to $385/MWh. The three [[Engineering:High-temperature gas-cooled reactor|high-temperature gas-cooled reactor]] designs, which needed more development time, had lower median LCOEs from $116/MWh to $137/MWh.<ref name=sciencedirect-20231015>{{cite journal |url=https://www.sciencedirect.com/science/article/pii/S0360544223015980 |doi=10.1016/j.energy.2023.128204 |title=Uncertainties in estimating production costs of future nuclear technologies: A model-based analysis of small modular reactors |last1=Steigerwald |first1=Björn |last2=Weibezahn |first2=Jens |last3=Slowik |first3=Martin |last4=von Hirschhausen |first4=Christian |journal=Energy |publisher=Elsevier |volume=281 |issue=15 |date=15 October 2023 |access-date=12 January 2024|doi-access=free }}</ref>

The first SMR deployment project in the US was the Carbon Free Power Project, which planned to deploy six 77 MWe [[Company:NuScale Power|NuScale]] reactors, reduced from twelve in earlier plans. Estimated target electricity generation price after subsidies was $89/MWh in 2023, an increase from $58/MWh in 2021. The increased generation cost led to the decision to cancel the project in November 2023.<ref name=eenews-20231109 /> Before its cancellation, the project received a $1.355 billion cost-share award toward construction costs from the US government in 2020<ref name=wnn-20201019>{{cite news |url=https://www.world-nuclear-news.org/Articles/US-government-backs-NuScale-projects-at-home-and-a |title=US government backs NuScale projects at home and abroad |publisher=World Nuclear News |date=19 October 2020 |access-date=10 January 2023}}</ref> plus an estimated $30/MWh generation subsidy from the 2020 Inflation Reduction Act.<ref name=wnn-20230109>{{cite news |date=9 January 2023 |title=Further cost refinements announced for first US SMR plant |publisher=World Nuclear News |url=https://www.world-nuclear-news.org/Articles/Further-cost-refinements-announced-for-first-US-SM |access-date=10 January 2023}}</ref> Unsubsidized cost estimates at cancellation were a capital cost of $20,139/kW and generating cost of $119/MWe.<ref name=ieefa-20230111>{{cite web |url=https://ieefa.org/resources/eye-popping-new-cost-estimates-released-nuscale-small-modular-reactor |title=Eye-popping new cost estimates released for NuScale small modular reactor |last=Schlissel |first=David |website=Institute for Energy Economics & Financial Analysis |date=11 January 2023 |access-date=27 January 2023}}</ref> This raised concerns about the commercial prospects in the U.S. of the other SMR designs.<ref name=science-20231110>{{cite news |url=https://www.science.org/content/article/deal-build-pint-size-nuclear-reactors-canceled |title=Deal to build pint-size nuclear reactors canceled |last=Cho |first=Adrian |magazine=Science |date=10 November 2023 |access-date=11 November 2023}}</ref>

== List of reactor designs ==
{{Main|Engineering:List of small modular reactor designs}}
Numerous reactor designs have been proposed. Notable SMR designs:

{{trim|{{#section-h::List of small nuclear reactor designs|Summary table}}}}

== Siting/infrastructure ==
SMRs are expected to require less land, e.g., the 470 MWe 3-loop Rolls-Royce SMR reactor should take {{Convert|40000|m2|abbr=on}}, 10% of that needed for a traditional plant.<ref name="rollsroyce-smr-brochure-2017">{{cite report|url=https://www.rolls-royce.com/~/media/Files/R/Rolls-Royce/documents/customers/nuclear/smr-brochure-july-2017.pdf|title=Small Modular Reactors UK, promotion brochure|publisher=Rolls-Royce|year=2017}} (5.5 MB)</ref> This unit is too large to meet the definition{{Citation needed|reason=Where is the definition of SMR, and is it generally agreed|date=January 2023}} of a small modular reactor and will require more on-site construction, which calls into question the claimed benefits of SMRs. The firm is targeting a 500-day construction time.<ref name="rollsroyce-2017">{{cite report|url=https://www.rolls-royce.com/~/media/Files/R/Rolls-Royce/documents/customers/nuclear/smr-technical-summary.pdf
|archive-url=https://web.archive.org/web/20190608143016if_/https://www.rolls-royce.com/~/media/Files/R/Rolls-Royce/documents/customers/nuclear/smr-technical-summary.pdf
|url-status=dead
|archive-date=2019-06-08
|title=UK SMR – brochure with specifications|publisher=Rolls-Royce|year=2017}} (5 MB) Archived</ref>

Electricity needs in remote locations are usually small and variable, making them suitable for a smaller plant.<ref>{{harvnb|Report to Congress|2001|p=8}}</ref> The smaller size may also reduce the need to access to a large grid to distribute their output.

== Proposed sites ==
=== Argentina ===
In February 2014, the [[Engineering:CAREM|CAREM]] SMR project started in {{wipe|Argentina}} with the civil engineering construction of the [[Physics:Containment building|containment building]] of a prototype reactor. The CAREM acronym means {{lang|es|Central ARgentina de Elementos Modulares}}. The [[Organization:National Atomic Energy Commission|National Atomic Energy Commission]] ({{lang-es|Comisión Nacional de Energía Atómica}}, CNEA), the {{wipe|Argentina}} government agency in charge of nuclear energy research and development and {{ill|Nucleoeléctrica Argentina|es|Nucleoelectrica Argentina SA}}, the national nuclear energy company, are cooperating to achieve the realization of the project.<ref name="WorldNuclearNews2023">{{cite web | title=CNEA and Nucleoeléctrica sign CAREM SMR agreement : New Nuclear | website=World Nuclear News | date=2023-10-30 | url=https://www.world-nuclear-news.org/Articles/Argentina-s-SMR-CNEA-and-Nucleoelectrica-sign-agre#:~:text=The%20CAREM%20name%20is%20taken,be%20sourced%20from%20Argentine%20companies. | access-date=2023-12-14}}</ref>

CAREM-25 is a prototype of 25 MWe, the first nuclear power plant completely designed and developed in Argentina.<ref name="WorldNuclearNews2023" /> The project was suspended several times before being resumed. In October 2022, CNEA expected that the civil construction works would be finished by 2024. If construction continues according to plan, the first criticality of CAREM-25 is foreseen by the end of 2027.<ref name="WorldNuclearNews2023" />

=== Canada ===
In 2018, the Canadian province of New Brunswick announced it would invest $10 million for a demonstration project at the Point Lepreau Nuclear Generating Station.<ref>{{Cite web |last=Government of New Brunswick |first=Canada |date=26 June 2018 |title=$10 million committed for nuclear research cluster |url=https://www2.gnb.ca/content/gnb/en/news/news_release.2018.06.0832.html |website=www2.gnb.ca}}</ref> It was later announced that SMR proponents Advanced Reactor Concepts<ref>{{Cite web |last=Government of New Brunswick |first=Canada |date=9 July 2018 |title=Partner announced in nuclear research cluster |url=https://www2.gnb.ca/content/gnb/en/departments/erd/news/news_release.2018.07.0906.html |website=www2.gnb.ca}}</ref> and Moltex<ref>{{Cite web |last=Government of New Brunswick |first=Canada |date=13 July 2018 |title=Moltex to partner in nuclear research and innovation cluster |url=https://www2.gnb.ca/content/gnb/en/departments/erd/news/news_release.2018.07.0930.html |website=www2.gnb.ca}}</ref> would open offices there.

On 1 December 2019, the Premiers of Ontario, New Brunswick and Saskatchewan signed a [[Finance:Memorandum of understanding|memorandum of understanding]] (MoU) <ref>{{cite web |title=Collaboration memorandum of understanding |url=http://files.news.ontario.ca.s3-website-us-east-1.amazonaws.com/opo/en/learnmore/premier_ford_premier_higgs_and_premier_moe_sign_agreement_on_the_development_of_small_modular_reacto/2019%2011%2027%20-%20MOU%20Prov%20NB%20and%20ON%20and%20SK.pdf?_ga=2.103085056.1434873882.1575249250-931592757.1575249250 |access-date=2 December 2019 |publisher=Government of Ontario}}</ref> "committing to collaborate on the development and deployment of innovative, versatile and scalable nuclear reactors, known as Small Modular Reactors (SMRs)."<ref>{{cite web |title=Premier Ford, Premier Higgs and Premier Moe Sign Agreement on the Development of Small Modular Reactors |url=https://news.ontario.ca/opo/en/2019/12/premier-ford-premier-higgs-and-premier-moe-sign-agreement-on-the-development-of-small-modular-reacto.html |access-date=2 December 2019 |website=ontario.ca |publisher=Government of Ontario}}</ref> They were joined by Alberta in August 2020.<ref>{{Cite web |title=Opinion: Small nuclear reactors can play big role in clean energy transition |url=https://calgaryherald.com/opinion/columnists/opinion-small-nuclear-reactors-can-play-big-role-in-clean-energy-transition |website=calgaryherald}}</ref> With continued support from citizens and government officials have led to the execution of a selected SMR at the Canadian Nuclear Laboratory.<ref name=":24"/>

In 2021, Ontario Power Generation announced they plan to build a [[Physics:BWRX-300|BWRX-300]] SMR at their Darlington site to be completed by 2028. A licence for construction still had to be applied for.<ref>[https://world-nuclear-news.org/Articles/OPG-chooses-BWRX-300-SMR-for-Darlington-new-build ''OPG chooses BWRX-300 SMR for Darlington new build.''] WNN, 2 Dec 2021</ref>

On 11 August 2022, Invest Alberta, the Government of Alberta's crown corporation signed a MoU with Terrestrial Energy regarding IMSR in Western Canada through an interprovincial MoU it joined earlier.<ref>{{cite web |title= Pact signed to advance IMSR development in western Canada|url=https://www.ans.org/news/article-4221/pact-signed-to-advance-imsr-development-in-western-canada/  |access-date=18 August 2022 |publisher=NuclearNewswire}}</ref>

=== China ===
In July 2019, China National Nuclear Corporation announced it would build an ACP100 SMR on the north-west side of the existing Changjiang Nuclear Power Plant at Changjiang, in the Hainan province by the end of the year.<ref name=wnn-20190722>{{cite news |url=http://www.world-nuclear-news.org/Articles/CNNC-launches-demonstration-SMR-project |title=''CNNC launches demonstration SMR project'' |publisher=World Nuclear News |date=22 July 2019 }}</ref> On 7 June 2021, the demonstration project, named the Linglong One, was approved by China's National Development and Reform Commission.<ref>{{Cite web|title=''China approves construction of demonstration SMR : New Nuclear - World Nuclear News''|url=https://world-nuclear-news.org/Articles/Construction-of-demonstration-Chinese-SMR-approved|access-date=2021-07-13|website=world-nuclear-news.org}}</ref> In July, China National Nuclear Corporation (CNNC) started construction,<ref>{{Cite news|author=Editing staff|date=2021-07-13|title=''China launches first commercial onshore small reactor project''|language=en|work=Reuters|url=https://www.reuters.com/article/us-china-nuclearpower-idUSKBN2EJ073}}</ref> and in October 2021, the containment vessel bottom of the first of two units was installed. It is the world's first commercial land-based SMR prototype.<ref name="containment-linglong1">[https://www.world-nuclear-news.org/Articles/Installation-of-containment-starts-at-Chinese-SMR ''Installation of containment starts at Chinese SMR.''] WNN, 25 Oct 2021</ref> 

In August 2023, the core module was installed. The core module includes an integrated [[Physics:Pressure vessel|pressure vessel]], [[Engineering:Steam generator (nuclear power)|steam generator]], primary pump receiver. The reactor's planned capacity is 125 MWe.<ref>{{Cite web |last=Largue |first=Pamela |date=2023-08-11 |title=Core module instaled at China's Linglong One modular reactor |url=https://www.powerengineeringint.com/nuclear/reactors/core-module-instaled-at-chinas-linglong-one-modular-reactor/ |access-date=2023-08-13 |website=Power Engineering International |language=en-US}}</ref>

=== France ===
At the beginning of 2023, Électricité de France (EDF) created a new subsidiary to develop and construct a new SMR: Nuward. It is a 340 MWe power plant with two independent light water reactors of 170 MWe. The twin reactors are sheltered in a single containment building and share most of their equipment.<ref name="EDF2022">{{cite web | author=EDF | year=2022 | title=NUWARD™ SMR, leading the way to a low‑carbon world | website=EDF.fr | date=2022-12-16 | url=https://www.edf.fr/en/the-edf-group/producing-a-climate-friendly-energy/nuclear-energy/shaping-the-future-of-nuclear/the-nuwardtm-smr-solution/the-solution | access-date=2023-12-14}}</ref> In August 2023, EDF submitted a safety case for Nuward to the {{lang|fr|autorité de sûreté nucléaire}} (ASN), the French safety authority.<ref name="Lopez2023">{{cite web | last1=Lopez | first1=Alicia | title=Licensing process begins for Nuward Small Modular Reactor project in France | website=Foro Nuclear | date=2023-08-10 | url=https://www.foronuclear.org/en/updates/news/licensing-process-begins-for-nuward-small-modular-reactor-project-in-france/ | access-date=2023-12-14}}</ref>

=== Poland ===
Polish chemical company Synthos declared plans to deploy a [[Company:Hitachi|Hitachi]] [[Physics:BWRX-300|BWRX-300]] reactor (300 MW) in Poland by 2030.<ref>{{Cite web|url=https://www.thefirstnews.com/article/billionaire-pole-to-build-nuclear-reactor-8244|title=Billionaire Pole to build nuclear reactor|website=www.thefirstnews.com|language=en|access-date=2020-02-17}}</ref> A feasibility study was completed in December 2020 and the licensing process started with the Polish National Atomic Energy Agency.<ref>{{Cite web|title=Feasibility study completed on SMRs for Poland - Nuclear Engineering International|url=https://www.neimagazine.com/news/newsfeasibility-study-completed-on-smrs-for-poland-8415956|access-date=2021-01-04|website=www.neimagazine.com}}</ref>

In February 2022, [[Company:NuScale Power|NuScale Power]] and the large mining [[Company:Conglomerate|conglomerate]] KGHM Polska Miedź announced signing of contract to construct a first operational reactor in Poland by 2029.<ref>{{Cite web|date=February 2022|title=NuScale, KGHM agree to deploy SMRs in Poland|language=en|url=https://www.world-nuclear-news.org/Articles/NuScale,-KGHM-agree-to-deploy-SMRs-in-Poland}}</ref>

=== Romania ===
On the occasion of 2021 United Nations Climate Change Conference, the state-owned Romanian nuclear energy company Nuclearelectrica and [[Company:NuScale Power|NuScale Power]] signed an agreement to build a power plant with six small-scale nuclear reactors at the Doicești power station, on the site of a former coal power plant, located near the village of Doicești, Dâmbovița county, 90&nbsp;km North of [[Place:Bucharest|Bucharest]]. The project is estimated to be completed by 2026–2027, which will make the power plant the first of its kind in Europe. The power plant is expected to generate 462&nbsp;MWe, securing the consumption of about 46.000 households and would help to avoid the release of 4 million tons of {{CO2}} per year.<ref>{{Cite web |last=Chirileasa |first=Andrei |date=2022-05-24 |title=Romania, the US agree on location of first small-scale nuclear reactor |url=https://www.romania-insider.com/ro-us-location-small-scale-reactor-may-2022 |access-date=2022-11-22 |website=Romania Insider}}</ref><ref>{{Cite web |title=Prima centrală cu mini reactor nuclear din Europa va fi la Doicești, Dâmbovița. Cum funcționează o centrală SMR |url=https://romania.europalibera.org/a/centrala-nculeara-doicesti/31917155.html |access-date=2022-11-22 |website=Europa Liberă România |language=ro}}</ref><ref>{{Cite web |last=Agerpres |title=Ghiţă (Nuclearelectrica): Suntem încrezători în potenţialul pe care amplasamentul de la.. |url=http://www.agerpres.ro/economic/2022/06/15/ghita-nuclearelectrica-suntem-increzatori-in-potentialul-pe-care-amplasamentul-de-la-doicesti-il-are-de-a-gazdui-primul-smr-nuscale-din-europa--934792 |access-date=2022-11-22 |website=www.agerpres.ro |language=ro}}</ref>

=== Russia ===
Russia has started to deploy on its arctic coast small nuclear reactors embarked on board [[Engineering:Icebreaker|icebreaker]]s. In May 2020, the first prototype of a [[Physics:Floating nuclear power plant|floating nuclear power plant]] with two 30&nbsp;MW<sub>e</sub> reactors  – the type ''KLT-40'' – started operation in [[Earth:Pevek|Pevek]], Russia.<ref name="klt-40_pris" /> This concept is based on the design of nuclear icebreakers.<ref name="klt40" />

=== United Kingdom ===
In 2016, it was reported that the UK Government was assessing Welsh SMR sites – including the former Trawsfynydd nuclear power station – and on the site of former nuclear or [[Finance:Coal-fired power station|coal-fired power station]]s in Northern England. Existing nuclear sites including Bradwell, Hartlepool, Heysham, Oldbury, Sizewell, Sellafield, and Wylfa were stated to be possibilities.<ref>{{cite news|last1=McCann|first1=Kate|title=Mini nuclear power stations in UK towns move one step closer|url=https://www.telegraph.co.uk/news/2016/04/02/mini-nuclear-power-stations-in-uk-towns-move-one-step-closer/|access-date=3 April 2016|work=The Sunday Telegraph|date=2 April 2016}}</ref> The target cost for a 470 MWe Rolls-Royce SMR unit is £1.8 billion for the fifth unit built.<ref name=wnn-20191107>{{cite news |url=http://www.world-nuclear-news.org/Articles/UK-confirms-funding-for-Rolls-Royce-SMR |title=UK confirms funding for Rolls-Royce SMR |publisher=World Nuclear News |date=7 November 2019 |access-date=8 November 2019}}</ref><ref name=rr-20210908>{{cite web |url=https://www.nuclearuniversities.ac.uk/wp-content/uploads/2021/09/Sophie-Macfarlane-Smith.pdf |title=Rolls-Royce SMR - Nuclear Academics Meeting |last=Macfarlane-Smith |first=Sophie |website=Rolls-Royce |date=8 September 2021 |access-date=25 September 2021}}</ref> In 2020, it was reported that [[Company:Rolls-Royce Holdings|Rolls-Royce]] had plans to construct up to 16 SMRs in the UK. In 2019, the company received £18 million to begin designing the modular system.<ref>{{cite news |title=Rolls-Royce plans 16 mini-nuclear plants for UK |url=https://www.bbc.co.uk/news/science-environment-54703204 |access-date=12 November 2020 |work=BBC News |date=11 November 2020}}</ref> An additional £210 million was awarded to Rolls-Royce by the British government in 2021, complemented by a £195 million contribution from private firms.<ref>{{cite web |title=Rolls-Royce gets funding to develop mini nuclear reactors |url=https://www.bbc.co.uk/news/business-59212983 |date=9 November 2021|publisher=BBC|access-date=10 November 2021}}</ref> In November 2022, Rolls-Royce announced that the sites at Trawsfynydd, Wylfa, Sellafield and Oldbury would be prioritised for assessment as potential locations for multiple SMRs.<ref>{{cite web |title= Study identifies potential Rolls-Royce SMR sites|url=https://www.world-nuclear-news.org/Articles/Study-identifies-potential-Rolls-Royce-SMR-sites |date=11 November 2022|publisher=World Nuclear News|access-date=16 November 2022}}</ref>

The British government launched Great British Nuclear in July 2023 to administer a competition to create SMRs, and will co-fund any viable project.<ref name=BBCJul23>{{cite news|url=https://www.bbc.co.uk/news/business-59212992|archive-url=https://web.archive.org/web/20230610030544/https://www.bbc.com/news/business-59212992|title=Nuclear energy: How environmentally-friendly and safe is it?|date=17 July 2023|work=BBC News|accessdate=19 July 2023|archivedate=10 June 2023}}</ref>

=== United States ===

Standard Power, a provider of infrastructure as a service to advanced data processing companies, has chosen to work with [[Company:NuScale Power|NuScale Power]] and ENTRA1 Energy to develop SMR-powered facilities in Pennsylvania and Ohio that will together produce nearly two gigawatts of clean, reliable energy.<ref>{{cite web |title=Standard Power Ohio and Pennsylvania |url=https://www.nuscalepower.com/en/projects |website=nuscalepower.com |publisher=NuScale Power |access-date=16 December 2023}}</ref>

[[Company:NuScale Power|NuScale Power]] is working with Wisconsin's Dairyland Power to evaluate VOYGR™ SMR power plants for potential deployment. The US leader in SMR technology believes its load-following capabilities can be used to support Dairyland’s existing renewables portfolio, as well as facilitate growth. Additionally, VOYGR plants are well-suited for replacing Dairyland’s retiring coal plant sites, preserving critical jobs and helping communities transition to a decarbonized energy system.<ref>{{cite web |title=Dairyland Power Cooperative WisconsinDairyland Power Cooperative Wisconsin |url=https://www.nuscalepower.com/en/projects |website=nuscalepower.com |publisher=NuScale Power |access-date=16 December 2023}}</ref>

[[Company:NuScale Power|NuScale Power]] is working with Associated Electric Cooperative Inc. (Associated) in Missouri to evaluate deployment of VOYGR™ SMR power plants as part of Associated’s due diligence to explore reliable, responsible sources of energy.<ref>{{cite web |title=Associated Electric Cooperative Missouri |url=https://www.nuscalepower.com/en/projects |website=nuscalepower.com |publisher=NuSclae Power |access-date=16 December 2023}}</ref>

NuScale had planned to build an SMR project in the US, the Carbon Free Power Project, but this was canceled in November 2023 for cost reasons.<ref name=eenews-20231109 /> NuScale said in January 2023 the target price for power from the plant was $89 per megawatt hour, up 53% from the previous estimate of $58 per MWh, raising concerns about customers' willingness to pay.<ref>{{cite web |last1=Gardner |first1=Timothy |title=My View Following Saved Energy Energy Grid & Infrastructure Nuclear Sustainable Markets NuScale ends Utah project, in blow to US nuclear power ambitions |url=https://www.reuters.com/business/energy/nuscale-power-uamps-agree-terminate-nuclear-project-2023-11-08/ |website=reuters.com |publisher=Reuters |access-date=15 December 2023}}</ref> Still, increased cost estimates remain well below traditional nuclear power used for commercial facilities and most other less reliable and more environmentally hazardous forms of power production.<ref>{{cite web |last1=Fernández |first1=Lucía |title=Estimated unsubsidized levelized costs of energy generation in the United States in 2023, by technology (in U.S. dollars per megawatt hour) |url=https://www.statista.com/statistics/493797/estimated-levelized-cost-of-energy-generation-in-the-us-by-technology/ |website=statista.com |publisher=Statista |access-date=15 December 2023}}</ref>

The Utah Associated Municipal Power Systems (UAMPS) had partnered with Energy Northwest to explore siting a [[Company:NuScale Power|NuScale Power]] reactor in Idaho, possibly on the Department of Energy's [[Organization:Idaho National Laboratory|Idaho National Laboratory]].<ref>{{Cite web|url=http://www.uamps.com/index.php/38-items/24-carbon-free-power-project|title=Carbon Free|website=www.uamps.com|access-date=8 April 2016|archive-date=19 January 2017|archive-url=https://web.archive.org/web/20170119125359/http://www.uamps.com/index.php/38-items/24-carbon-free-power-project|url-status=dead}}</ref> The project was cancelled in 2023 due to increased costs.<ref name=eenews-20231109>{{cite news |url=https://www.eenews.net/articles/nuscale-cancels-first-of-a-kind-nuclear-project-as-costs-surge/ |title=NuScale cancels first-of-a-kind nuclear project as costs surge |last=Bright |first=Zach |website=E&E News |publisher=Politico |date=9 November 2023 |access-date=9 November 2023}}</ref> 

The Galena Nuclear Power Plant in Galena, Alaska was a proposed micro nuclear reactor installation. It was a potential deployment for the [[Engineering:Toshiba 4S|Toshiba 4S]] reactor.<ref>{{Cite web |title=Nuclear Power and the Perils of Pioneering |url=https://www.uaf.edu/acep-blog/nuclear-power-and-the-perils-of-pioneering.php |access-date=2023-12-05 |website=www.uaf.edu |language=en}}</ref> The project was "effectively stalled." Toshiba never began the expensive process for approval that is required by the U.S. Nuclear Regulatory Commission.

Although the SMR now under consideration has yet to be NRC licensed, the Tennessee Valley Authority was authorized to receive an Early Site Permit (ESP) by the Nuclear Regulatory Commission for siting an SMR at its Clinch River site in {{wipe|Tennessee}} in December 2019.<ref>{{Cite web|url=https://www.nrc.gov/reading-rm/doc-collections/news/2019/19-064.pdf|title=NRC to Issue Early Site Permit to Tennessee Valley Authority for Clinch River Site|last=U.S. Nuclear Regulatory Commission|date=17 December 2019|website=nrc.gov|access-date=24 December 2019}}</ref> This ESP is valid for 20 years, and addresses site safety, environmental protection and emergency preparedness. This ESP is applicable for any [[Engineering:Light-water reactor|light-water reactor]] SMR design under development in the United States.<ref>{{Cite web|url=https://www.tva.gov/Energy/Technology-Innovation/Small-Modular-Reactors|title=TVA - Small Modular Reactors|website=www.tva.gov|access-date=8 April 2016}}</ref>

== References ==
{{reflist|refs=

<ref name=":0b">{{cite web |url=https://www.oecd-nea.org/ndd/pubs/2016/7213-smrs.pdf |title=Small Modular Reactors: Nuclear Energy Market Potential for Near-term Deployment |date=2016 |website=OECD-NEA.org}}</ref>

<ref name=":1">{{cite web |url=https://www.sustainability-times.com/uncategorized/squaring-the-energy-circle-with-smrs/ |title=Squaring the energy circle with SMRs |last=Furfari |first=Samuele |date=2019-10-31 |website=Sustainability Times |language=en-GB |access-date=2020-04-16}}</ref>

<ref name=":2">{{cite web |last=Berniolles |first=Jean-Marie |date=2019-11-29 |title=De-mystifying small modular reactors |url=https://www.sustainability-times.com/low-carbon-energy/de-mystifying-small-modular-reactors/ |website=Sustainability Times |language=en-GB |access-date=2020-04-16}}</ref>

<ref name="auto1b">{{cite web |last=Trakimavičius |first=Lukas |date=Nov 2020 |title=Is Small Really Beautiful? The Future Role of Small Modular Nuclear Reactors (SMRs) In The Military |url=https://www.enseccoe.org/data/public/uploads/2020/11/02.-solo-article-lukas-smr-eh-15-web-version-final.pdf |website=NATO Energy Security Centre of Excellence |language=en}}</ref>

<ref name="auto22">[http://www.roe.com/pdfs/technical/Galena/Overview%20Whitepaper%20Rev02.pdf "The Galena Project Technical Publications"], p. 22, [http://www.roe.com ''Burns & Roe'']</ref>

<!-- <ref name="mittr-20230208">{{cite news |url=https://www.technologyreview.com/2023/02/08/1067992/smaller-nuclear-reactors/ |title=We were promised smaller nuclear reactors. Where are they? |last=Crownhart |first=Casey |website=MIT Technology Review |date=8 February 2023 |access-date=29 March 2023}}</ref> -->

<ref name="nei-20230118">{{cite news |url=https://www.neimagazine.com/features/featureiaea-ups-support-for-smrs-10528638/ |title=IAEA ups support for SMRs |last=Perera |first=Judith |publisher=Nuclear Engineering International |date=18 January 2023 |access-date=24 January 2023}}</ref>

<ref name="smallBeauty">{{cite web |url=https://www.ucsusa.org/sites/default/files/legacy/assets/documents/nuclear_power/small-isnt-always-beautiful.pdf |title=Small isn't always beautiful |publisher=Union of Concerned Scientists |date=2013 |access-date=2 April 2019 |archive-date=25 September 2019 |archive-url=https://web.archive.org/web/20190925220106/https://www.ucsusa.org/sites/default/files/legacy/assets/documents/nuclear_power/small-isnt-always-beautiful.pdf |url-status=dead }}</ref>

<ref name="UCS1">{{cite web |title=Small Modular Reactors: Safety, Security and Cost Concerns (2013) |url=https://www.ucsusa.org/nuclear-power/nuclear-power-technology/small-modular-reactors |website=Union of Concerned Scientists |language=en |access-date=2 April 2019}}</ref>

}}

== Further reading ==
{{Refbegin}}
* {{cite book | editor=Daniel T. Ingersoll and Mario D. Carelli | title=Handbook of Small Modular Nuclear Reactors | publisher=Elsevier – Woodhead Publishing | date=2021 | isbn=978-0-12-823916-2 | doi=10.1016/c2019-0-00070-2 | page=}}
* {{cite web |author=Office of Nuclear Energy, Science and Technology |title=DOE Fundamentals Handbook: Nuclear Physics and Reactor Theory |volume=2 |date=January 1993 |publisher=U.S. Department of Energy |url=http://www.hss.doe.gov/nuclearsafety/techstds/docs/handbook/h1019v2.pdf |id=DOE-HDBK-1019, DE93012223 |ref={{harvid|DOE-HDBK-1019|1993}} |url-status=dead |archive-url=https://web.archive.org/web/20121109194948/http://www.hss.doe.gov/nuclearsafety/techstds/docs/handbook/h1019v2.pdf |archive-date=9 November 2012}}
* {{cite web |author=Office of Nuclear Energy, Science and Technology |title=Report to Congress on Small Modular Nuclear Reactors |date=May 2001 |publisher=U.S. Department of Energy |url=http://www.ne.doe.gov/pdfFiles/Cong-Rpt-may01.pdf |ref={{harvid|Report to Congress|2001}} |url-status=dead |archive-url=https://web.archive.org/web/20110716055134/http://www.ne.doe.gov/pdfFiles/Cong-Rpt-may01.pdf |archive-date=16 July 2011}}
* {{cite journal | last1=Vinoya | first1=Carlo L. | last2=Ubando | first2=Aristotle T. | last3=Culaba | first3=Alvin B. | last4=Chen | first4=Wei-Hsin | title=State-of-the-Art Review of Small Modular Reactors | journal=Energies | volume=16 | issue=7 | date=2023-04-03 | issn=1996-1073 | doi=10.3390/en16073224 | doi-access=free | page=3224}}
* {{cite web | last1=Lyman | first1=Edwin | date=September 2013 | title=Small Isn't Always Beautiful. Safety, Security, and Cost Concerns about Small Modular Reactors | url=https://www.ucsusa.org/sites/default/files/2019-10/small-isnt-always-beautiful.pdf | work=ucsusa.org | access-date=2024-01-13}}
{{Refend}}

== External links ==
* {{cite web | title=Advanced Reactor Information System (ARIS) IAEA database | website=ARIS–IAEA | date=2016-05-17 | url=https://aris.iaea.org/ | access-date=2023-12-15}}
* {{cite web | title=Small Nuclear Power Reactors | website=World Nuclear Association | date=2018-02-07 | url=https://www.world-nuclear.org/information-library/nuclear-fuel-cycle/nuclear-power-reactors/small-nuclear-power-reactors.aspx | ref={{sfnref | World Nuclear Association | 2018}} | access-date=2023-12-05}}
* {{cite web | title=Small Modular Reactors: Challenges and Opportunities | website=Nuclear Energy Agency (NEA) | date=2023-07-03 | url=https://www.oecd-nea.org/jcms/pl_57979/small-modular-reactors-challenges-and-opportunities | ref={{sfnref | Nuclear Energy Agency (NEA) | 2023}} | access-date=2023-12-07}}
* {{cite web | title=Small Modular Reactors (SMR) | website=BASE | url=https://www.base.bund.de/EN/ns/ni-germany/smr/small-modular-reactors_node.html | ref={{sfnref | BASE}} | access-date=2023-12-09}}
* [https://web.archive.org/web/20100624035928/http://www.ne.doe.gov/ DOE Office of Nuclear Energy] 
* [https://www.nrc.gov American Nuclear Regulatory Commission]
* [https://www.world-nuclear.org World Nuclear Association]
* [https://www.ans.org American Nuclear Society]
* [https://www.iaea.org International Atomic Energy Agency]
* [https://www.iaea.org/INPRO/3rd_Dialogue_Forum/07.Ingersoll.pdf Overview and Status of SMRs Being Developed in the United States] {{dead link|date=December 2023}}

{{Nuclear fission reactors}}

[[Category:Nuclear power reactor types]]

{{Sourceattribution|Small modular reactor}}