Figure 4 Illustration of a light water small modular nuclear reactor (SMR) (20848048201)

Small modular reactors (SMRs) are a proposed class of

nuclear fission reactor A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. Heat from n ...

s, smaller than conventional nuclear reactors, which can be built in one location (such as a factory), then shipped, commissioned, and operated at a separate site. The term SMR refers to the size, capacity and

modular Broadly speaking, modularity is the degree to which a system's components may be separated and recombined, often with the benefit of flexibility and variety in use. The concept of modularity is used primarily to reduce complexity by breaking a sy ...

construction only, not to the reactor type and the nuclear process which is applied. Designs range from scaled down versions of existing designs to generation IV designs. Both

thermal-neutron reactor A thermal-neutron reactor is a nuclear reactor that uses slow or thermal neutrons. ("Thermal" does not mean hot in an absolute sense, but means in thermal equilibrium with the medium it is interacting with, the reactor's fuel, moderator and struct ...

s and

fast-neutron reactor A fast-neutron reactor (FNR) or fast-spectrum reactor or simply a fast reactor is a category of nuclear reactor in which the fission chain reaction is sustained by fast neutrons (carrying energies above 1 MeV or greater, on average), as opposed t ...

s have been proposed, along with

molten salt Molten salt is salt which is solid at standard temperature and pressure but enters the liquid phase due to elevated temperature. Regular table salt has a melting point of 801 °C (1474°F) and a heat of fusion of 520 J/g.< ...

and

gas cooled reactor A gas-cooled reactor (GCR) is a nuclear reactor that uses graphite as a neutron moderator and a gas (carbon dioxide or helium in extant designs) as coolant. Although there are many other types of reactor cooled by gas, the terms ''GCR'' and to a l ...

models. SMRs are typically anticipated to have an

electrical power Electric power is the rate at which electrical energy is transferred by an electric circuit. The SI unit of power is the watt, one joule per second. Standard prefixes apply to watts as with other SI units: thousands, millions and billions of ...

output of less than 300 MW_e (electric) or less than 1000 MW_th (thermal). Many SMR proposals rely on a manufacturing-centric model, requiring many deployments to secure economies of unit production large enough to achieve economic viability. Some SMR designs, typically those using Generation IV technologies, aim to secure additional economic advantage through improvements in electrical generating efficiency from much higher temperature steam generation. Ideally, modular reactors will reduce on-site construction, increase containment efficiency, and are claimed to enhance safety. The greater safety should come via the use of

passive safety Automotive safety is the study and practice of design, construction, equipment and regulation to minimize the occurrence and consequences of traffic collisions involving motor vehicles. Road traffic safety more broadly includes roadway design ...

features that operate without human intervention, a concept already implemented in some conventional nuclear reactor types. SMRs should also reduce staffing versus conventional nuclear reactors,"The Galena Project Technical Publications"
pg. 22
''Burns & Roe''
/ref> and are claimed to have the ability to bypass financial and safety barriers that inhibit the construction of conventional reactors. While there are dozens of modular reactor designs and yet unfinished demonstration projects, the floating nuclear power plant

Akademik Lomonosov ''Akademik Lomonosov'' (russian: Академик Ломоносов) is a non-self-propelled power barge that operates as the first Russian floating nuclear power station. The ship was named after Russian Academy of Sciences, academician Mikhai ...

(operating in

Pevek Pevek (russian: Певе́к; Chukchi: , ''Pèèkin'' / ''Pèèk'') is an Arctic port town and the administrative center of Chaunsky District in Chukotka Autonomous Okrug, Russia, located on Chaunskaya Bay (part of the East Siberian Sea) on a pe ...

in Russia's Far East) is, as of October 2022, the first and only operating prototype in the world. Construction of the world's first land-based SMR began in July 2021 with the Chinese power plant Linglong One ( zh, 玲珑一号); this prototype is due to commence generation by the end of 2026. SMRs differ in terms of staffing, security and deployment time. US government studies to evaluate SMR-associated risks have slowed licensing. One concern with SMRs is preventing

nuclear proliferation Nuclear proliferation is the spread of nuclear weapons, fissionable material, and weapons-applicable nuclear technology and information to nations not recognized as " Nuclear Weapon States" by the Treaty on the Non-Proliferation of Nuclear Wea ...

Background

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 The Chernobyl disaster was a nuclear accident that occurred on 26 April 1986 at the No. 4 reactor in the Chernobyl Nuclear Power Plant, near the city of Pripyat in the north of the Ukrainian SSR in the Soviet Union. It is one of only two nuc ...

and the 2011

Fukushima nuclear disaster The was a nuclear accident in 2011 at the Fukushima Daiichi Nuclear Power Plant in Ōkuma, Fukushima, Japan. The proximate cause of the disaster was the 2011 Tōhoku earthquake and tsunami, which occurred on the afternoon of 11 March 2011 and ...

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 aiming at building smaller reactors, which are faster to realize, safer, and at lower cost for a single 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 expected shorter timescales. The generic SMR proposal is to swap the economies of unit scale for the economies of unit mass production. Proponents claim that SMRs are less expensive due to the use of standardized modules that can be produced off-site. SMRs do, however, also have some economic disadvantages. 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. Critics say that modular building will only be cost-effective at high quantities of the same types, given the still remaining high costs for each SMR. A high market share is needed to obtain sufficient orders. Proponents say that nuclear energy with proven technology is safe; the nuclear industry contends that smaller size will make SMRs even safer than conventional plants. Critics say that more small reactors pose a higher risk, requiring more transportation of nuclear fuel and increased generation of waste. SMRs require new designs with new technology, the safety of which has yet to be proven. Until 2020, no truly modular SMRs had been built. In May 2020, the first prototype of a floating nuclear power plant with two 30 MW_e reactors - the type ''

KLT-40 The KLT-40 family are nuclear fission reactors originating from OK-150 and OK-900 ship reactors. KLT-40 were developed to power the ''Taymyr''-class icebreakers (KLT-40M, 171 MW) and the LASH carrier ''Sevmorput'' (KLT-40, 135 MW).Akademik Lomonosov-1
Power Reactor Information System (PRIS), International Atomic Energy Agency, 2020-09-13. This concept is based on the design of nuclear

icebreaker An icebreaker is a special-purpose ship or boat designed to move and navigate through ice-covered waters, and provide safe waterways for other boats and ships. Although the term usually refers to ice-breaking ships, it may also refer to smaller ...

s. The operation of the first commercial land-based, 125 MW_e demonstration reactor ''

ACP100 The China National Nuclear Corporation (CNNC; ) is a state-owned enterprise founded in 1955 in Beijing. CNNC's president and vice-president are appointed by the Premier of the People's Republic of China. CNNC oversees all aspects of China's civ ...

'' (Linglong One) is due to start in China by the end of 2026.

General aspects

Licensing

Once the first unit of a given design is licensed, licensing subsequent units should be drastically simpler, assuming that all units operate identically.

Scalability

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. Some SMRs have a load-following design such that they can produce less electricity when demand is low.

Siting/infrastructure

SMRs will require much less land, e.g., the 470 MWe 3-loop

Rolls-Royce SMR The Rolls-Royce SMR, also known as the UK SMR, is a small modular reactor (SMR) being developed by the Rolls-Royce (RR) company in the United Kingdom. The company has been given financial support by the UK Government to develop its design. It i ...

reactor takes , 10% of that needed for a traditional plant. (5.5 MB) This unit is too large to meet the definition 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. (5 MB) Archived Electricity needs in remote locations are usually small and variable, making them suitable for a smaller plant. The smaller size may also reduce the need for a grid to distribute their output.

Flexibility of SMR

SMRs offer significant advantages over conventional style nuclear reactors due to the flexibility of their modular design. Flexibility in the capabilities of SMRs offers advantages, incremental load capacity, ability for adaptation to current nuclear powerplant sites, utilization for industrial applications, improved operating time, and the ability to be “grid independent”.

Safety

Containment is more efficient, and proliferation concerns are much less. For example, a pressure release valve may have a spring that can respond to increasing pressure to increase coolant flow. ''Inherent'' safety features require no moving parts to work, depending only on physical laws. Another example is a plug at the bottom of a reactor that melts away when temperatures are too high, allowing the reactor fuel to drain out of the reactor and lose critical mass. 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."''Sicherheitstechnische Analyse und Risikobewertung einer Anwendung von SMR-Konzepten (Small Modular Reactors)''
BASE, März 2021''Für die Zukunft zu spät.''
Süddeutsche Zeitung, 9. März 2021

Proliferation

Many SMRs are designed to use unconventional fuels that allow for higher

burnup In nuclear power technology, burnup (also known as fuel utilization) is a measure of how much energy is extracted from a primary nuclear fuel source. It is measured as the fraction of fuel atoms that underwent fission in %FIMA (fissions per init ...

and longer fuel cycles. Longer refueling intervals can decrease proliferation risks and lower chances of radiation escaping containment. For reactors in remote areas, accessibility can be troublesome, so longer fuel life can be helpful.

Designs

SMRs are envisioned in multiple designs. Some are simplified versions of current reactors, others involve entirely new technologies. All proposed SMRs use

nuclear fission Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radio ...

with designs including

s and

Thermal-neutron reactors

Thermal-neutron reactors rely on a moderator to slow neutrons and generally use as fissile material. Most conventional operating reactors are of this type.

Fast reactors

Fast reactors don't use moderators. Instead they rely on the fuel to absorb higher speed neutrons. This usually means changing the fuel arrangement within the core, or using different fuels. E.g., is more likely to absorb a high-speed neutron than . Fast reactors can be

breeder reactor A breeder reactor is a nuclear reactor that generates more fissile material than it consumes. Breeder reactors achieve this because their neutron economy is high enough to create more fissile fuel than they use, by irradiation of a fertile mate ...

s. These reactors release enough neutrons to transmute non-fissionable elements into fissionable ones. A common use for a breeder reactor is to surround the core in a "blanket" of , the most easily found isotope. Once the undergoes a neutron absorption reaction, it becomes , which can be removed from the reactor during refueling, and subsequently used as fuel.Carlson, J
"Fast Neutron Reactors"''World Nuclear Association''
/ref>

Technologies

Cooling

Conventional reactors typically use water as a coolant. SMRs may use water,

liquid metal A liquid metal is a metal or a metal alloy which is liquid at or near room temperature. The only stable liquid elemental metal at room temperature is Mercury (element), mercury (Hg), which is molten above −38.8 °C (234.3 K, −37.9&nbs ...

gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...

and

as coolants.Wilson, P.D
"Nuclear Power Reactors"''World Nuclear Association''
/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. Helium is often elected as a gas coolant for SMRs because it yields a high plant thermal efficiency and supplies a sufficient amount of reactor heat. Sodium, lead, and lead-bismuth are common liquid metal coolants of choice for 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. SMRs have lower cooling water requirements, which expands the number of places a SMR could be built, including remote areas typically incorporating mining and desalination.

Thermal/electrical generation

Some gas-cooled reactor designs could drive a gas-powered turbine, rather than boiling water, such that thermal energy can be used directly. Heat could also be used in

hydrogen production Hydrogen production is the family of industrial methods for generating hydrogen gas. As of 2020, the majority of hydrogen (∼95%) is produced from fossil fuels by steam reforming of natural gas and other light hydrocarbons, partial oxidation of h ...

and other commercial operations, such as

desalination Desalination is a process that takes away mineral components from saline water. More generally, desalination refers to the removal of salts and minerals from a target substance, as in Soil salinity control, soil desalination, which is an issue f ...

and the production of petroleum products (extracting oil from

oil sands Oil sands, tar sands, crude bitumen, or bituminous sands, are a type of unconventional petroleum deposit. Oil sands are either loose sands or partially consolidated sandstone containing a naturally occurring mixture of sand, clay, and wate ...

, creating synthetic oil from coal, etc.).

Load following

SMR designs are generally expected to provide

base load The base load (also baseload) is the minimum level of demand on an electrical grid over a span of time, for example, one week. This demand can be met by unvarying power plants, dispatchable generation, or by a collection of smaller intermittent en ...

power; some proposed designs can adjust their output based on demand. Another approach, especially for SMRs that can provide high temperature heat, is to adopt cogeneration, maintaining consistent output, while diverting otherwise unneeded heat to an auxiliary use. District heating, desalination and hydrogen production have been proposed as cogeneration options. Overnight desalination requires sufficient freshwater storage to enable water to be delivered at times other than when it is produced. Membrane and thermal are the two principal categories of desalination technology. The membrane desalination process uses only electricity and is employed the most out of the two technologies. In the thermal process, the feed water stream is evaporated in different stages with continuous decreases in pressure between the stages. The thermal process primarily uses thermal energy and does not include the intermediate conversion of thermal power to electricity. Thermal desalination technology is further divided into two principal technologies: the Multi Stage Flash distillation (MSF) and the Multi Effect Desalination (MED).

Waste

One study reported that some types of SMR could produce more waste per unit of output than conventional reactors, in some cases more than 5x the

spent fuel Spent nuclear fuel, occasionally called used nuclear fuel, is nuclear fuel that has been irradiated in a nuclear reactor (usually at a nuclear power plant). It is no longer useful in sustaining a nuclear reaction in an ordinary thermal reactor and ...

per kilowatt, and as much as 35x other waste products, such as active steel. Neutron leakage rates were estimated to be higher for SMRs, because in smaller reactor cores, emitted neutrons have fewer chances to interact with the fuel. Instead, they exit the core, where they are absorbed by the shielding, turning it radioactive. Reactor designs that use liquid metal coolants also become radioactive. Another potential issue is that a lower fraction of the fuel is consumed, increasing waste volumes. The potentially increased diversity of reactors may require accordingly diverse waste management systems. A report by the German Federal Office for the Safety of Nuclear Waste Management found that extensive interim storage and fuel transports would still be required for SMRs. A repository would still be required in any case. Many SMR designs are fast reactors that have higher fuel burnup, reducing the amount of waste. At higher neutron energy more

fission products Nuclear fission products are the atomic fragments left after a large atomic nucleus undergoes nuclear fission. Typically, a large nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons, the release ...

can usually be tolerated. Breeder reactors "burn" , but convert

fertile material Fertile material is a material that, although not itself fissionable by thermal neutrons, can be converted into a fissile material by neutron absorption and subsequent nuclei conversions. Naturally occurring fertile materials Naturally occurring ...

s such as into usable fuels. Some reactor designs utilise the

thorium fuel cycle The thorium fuel cycle is a nuclear fuel cycle that uses an isotope of thorium, , as the fertile material. In the reactor, is transmuted into the fissile artificial uranium isotope which is the nuclear fuel. Unlike natural uranium, natural tho ...

, which offers significantly reduced long-term waste radiotoxicity compared to the uranium cycle. The

traveling wave reactor A traveling-wave reactor (TWR) is a proposed type of nuclear fission reactor that can convert fertile material into usable fuel through nuclear transmutation, in tandem with the burnup of fissile material. TWRs differ from other kinds of fast-ne ...

immediately uses fuel that it breeds without requiring the fuel's removal and cleaning.

Safety

Some proposed SMRs use cooling systems that use thermoconvection – natural circulation – to eliminate cooling pumps that could break down. Convection can keep removing decay heat after reactor shutdown. Negative temperature coefficients in the moderators and the fuels keep the fission reactions under control, causing the reaction to slow as temperature increases. Some SMRs may need an active cooling system to back up the passive system, increasing cost. Additionally, SMR designs may have less need for containment structures. Some SMR designs bury the reactor and spent-fuel storage pools underground. Smaller reactors would be easier to upgrade. oniz, Ernest. "Why We Still Need Nuclear Power: Making Clean Energy Safe and Affordable." Foreign Affairs 90, no. 6 (November 2011): 83-94./ref> SMRs maintain core cooling with a passive safety system which eliminates the need for pressure injection systems. With a passive safety system, emergency AC power sourced from a diesel generator is not required for core cooling. A passive safety system is simpler, requires less testing, and does not lead to inadvertent initiation. SMRs do not require an active containment heat system due to passive heat rejection out of containment and a containment spray system is not required. An emergency feedwater system in not necessary for SMRs, allowing for core heat removal and enhancing safety. SMRs featuring water and sodium coolants increase reactor safety through their ability to withhold byproducts of the fissile fuel introduced into the coolants during a severe accident. This characteristic of a SMR allows for the ability of a SMR to mitigate the release of fissile material, contaminating the environment, in the event of a failure to maintain containment of nuclear material occurred. 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 radiation leaks can easily be contained. In comparison to larger reactors having numerous components outside the reactor vessel, this feature drastically increases the safety by decreasing the chance of an uncontained accident. Furthermore, this feature allows many SMR designs bury the reactor and spent-fuel storage pools underground at the end of their service life therefore increasing the safety of waste disposal.

Flexibility of SMR

Small nuclear reactors, in comparison to conventional nuclear power generation plants, offer many advantages due to the flexibility of their modular construction. This flexibility in the modularity of a SMR system allows for additional units to be incrementally added in the event load on the grid increases. Additionally, this flexibility in a standardized SMRs design revolving around modularity allows for rapid production at a decreasing cost following the completion of the first reactor on site. The hypothesised flexibility and modularity of SMR allows additional power generation capability to be installed at existing power plants. Modularity of a SMR plant allows for “a single site can have three or four SMRs, allowing one to go off-line for refueling while the other reactors stay online”. The flexibility of SMRs provides additional opportunities for industrial usage through saving energy lost through the transfer of energy from thermal to electrical. Applications for a SMR under these conditions of direct energy transfer include “desalination, industrial processes, hydrogen production, oil shale recovery, and district heating” of which a conventional large reactor is not capable.

Economics

A key driver of interest in SMRs is the claimed

economies of scale In microeconomics, economies of scale are the cost advantages that enterprises obtain due to their scale of operation, and are typically measured by the amount of output produced per unit of time. A decrease in cost per unit of output enables ...

in production, as (by definition) they can be manufactured in an offsite factory. Some studies instead find the capital cost of SMRs to be equivalent to larger reactors. Substantial capital is needed to construct the factory - ameliorating that cost requires significant volume, estimated to be 40–70 units. When comparing SMRs with Large Reactors, however, the unique characteristics of SMRs that should compensate for the lack of the economy of scale should also be considered, although no SMR design presents all of them. Given the lower capacity, these characteristics will increase the demand for construction sites to obtain the same power of a Large Reactor, but will in itself not increase the demand for nuclear power plants. Financial and economic issues can hinder SMR construction. Construction costs per SMR reactor are claimed to be less than that for a conventional nuclear plant, while exploitation costs may be higher for SMRs due to low scale economics and the higher number of reactors. Staffing costs per unit output increase as reactor size decreases, due to fixed costs. SMR staff costs per unit output can be as much as 190% higher than the fixed operating cost of large reactors. Modular building is a very complex process and there is "extremely limited information about SMR modules transportation", according to a 2019 report. 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. In 2017, an Energy Innovation Reform Project study of eight companies looked at reactor designs with capacity between 47.5 MWe and 1,648 MWe. The study reported average capital cost of $3,782/kW, average operating cost total of $21/MWh and levelized cost of electricity of $60/MWh.

Energy Impact Center The Energy Impact Center is an American research institute based in Washington, D.C. It primarily advocates for the expansion of nuclear power as a clean energy solution to climate change. The organization's research into nuclear power has led it ...

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." 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. According to a 2014 study of electricity production in decentralized microgrids, compared to the total cost of offshore wind, solar thermal, biomass, and solar photovoltaic electricity generation plants, the total cost of using SMRs for electricity generation is significantly lower.

Licensing

A major barrier to SMR adoption is the licensing process. It was developed for conventional, custom-built reactors, preventing the simple deployment of identical units at different sites. In particular, the US

Nuclear Regulatory Commission The Nuclear Regulatory Commission (NRC) is an independent agency of the United States government tasked with protecting public health and safety related to nuclear energy. Established by the Energy Reorganization Act of 1974, the NRC began operat ...

process for

licensing A license (or licence) is an official permission or permit to do, use, or own something (as well as the document of that permission or permit). A license is granted by a party (licensor) to another party (licensee) as an element of an agreeme ...

has focused mainly on conventional reactors. Design and safety specifications, staffing requirements and licensing fees have all been geared toward reactors with electrical output of more than 700MWe. With a sizable focus on large reactors, it is probable that many countries will have to adapt their policies to coincide with SMRs, which can be a costly and time-consuming process. The International Atomic Energy Agency has placed emphasis on creating a central licensing system for SMRs to ensure proper guidelines in the interest of overall public safety. SMRs caused a reevaluation of the licensing process for nuclear reactors. One workshop in October 2009 and another in June 2010 considered the topic, followed by a

Congressional hearing A United States congressional hearing is the principal formal method by which United States congressional committees collect and analyze information in the early stages of legislative policymaking. Whether confirmation hearings (a procedure unique ...

in May 2010. Multiple US agencies are working to define SMR licensing. However, some argue that weakening safety regulations to push the development of SMRs may offset their enhanced safety characteristics. 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.

Nuclear proliferation

Nuclear proliferation Nuclear proliferation is the spread of nuclear weapons, fissionable material, and weapons-applicable nuclear technology and information to nations not recognized as " Nuclear Weapon States" by the Treaty on the Non-Proliferation of Nuclear Wea ...

, 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. SMRs are expected to substantially reduce staffing levels. The combination creates physical protection and security concerns. Many SMRs are designed to address these concerns. Fuel can be low-enriched uranium, with less than 20% fissile . This low quantity, sub-weapons-grade uranium is less desirable for weapons production. Once the fuel has been

irradiated Irradiation is the process by which an object is exposed to radiation. The exposure can originate from various sources, including natural sources. Most frequently the term refers to ionizing radiation, and to a level of radiation that will serve ...

, 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 without difficulty 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”. 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. 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 The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James Watt ...

30-year core life light water SMR could contain about 2.5 tonnes of plutonium at end of life. 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 Light-water reactors designed to run on

thorium Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high me ...

offer increased proliferation resistance compared to the conventional uranium cycle, though

molten salt reactors A molten salt reactor (MSR) is a class of nuclear fission reactor in which the primary nuclear reactor coolant and/or the fuel is a molten salt mixture. Only two MSRs have ever operated, both research reactors in the United States. The 1950's Ai ...

have a substantial risk. SMR are transported from the factories without fuel, as they are fueled on the ultimate site, except some microreactors.

List of reactor designs

Numerous reactor designs have been proposed. Notable SMR designs:

Proposed sites

Canada

In 2018, the Canadian province of

New Brunswick New Brunswick (french: Nouveau-Brunswick, , locally ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. It is the only province with both English and ...

announced it would invest $10 million for a demonstration project at the

Point Lepreau Nuclear Generating Station Point Lepreau Nuclear Generating Station is a nuclear power station located 2 km northeast of Point Lepreau, New Brunswick, Canada. The facility was constructed between 1975 and 1983 by NB Power, the provincially owned public utility. T ...

. It was later announced that SMR proponents Advanced Reactor Concepts and Moltex would open offices there. On 1 December 2019, the Premiers of

Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...

and

Saskatchewan Saskatchewan ( ; ) is a Provinces and territories of Canada, province in Western Canada, western Canada, bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and on t ...

signed a memorandum of understanding "committing to collaborate on the development and deployment of innovative, versatile and scalable nuclear reactors, known as Small Modular Reactors (SMRs)." They were joined by

Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...

in August 2020. With continued support from citizens and government officials have led to the execution of a selected SMR at the Canadian National Nuclear Laboratory. In 2021, Ontario Power Generation announced they plan to build a

BWRX-300 The BWRX-300 is a design for a small modular nuclear reactor proposed by GE Hitachi Nuclear Energy (GEH). The BWRX-300 would feature passive safety, in that neither external power nor operator action would be required to maintain a safe state, e ...

SMR at their Darlington site to be completed by 2028. A licence for construction still had to be applied for. On 11 August 2022, Invest Alberta, the Government of Alberta’s crown corporation signed a MOU with

Terrestrial Energy Terrestrial Energy is a Canadian nuclear technology company working on Generation IV nuclear technology. It expects to produce cost-competitive, high-temperature thermal energy with zero emissions. The company is developing a 190 MWe Integral ...

regarding

IMSR The Integral Molten Salt Reactor (IMSR) is a nuclear power plant design targeted at developing a commercial product for the small modular reactor (SMR) market. It employs molten salt reactor technology which is being developed by the Canadian comp ...

in Western Canada through an interprovincial MOU it joined earlier.

China

In July 2019,

China National Nuclear Corporation The China National Nuclear Corporation (CNNC; ) is a state-owned enterprise founded in 1955 in Beijing. CNNC's president and vice-president are appointed by the Premier of the People's Republic of China. CNNC oversees all aspects of China's c ...

announced it would build an

SMR on the north-west side of the existing

Changjiang Nuclear Power Plant Changjiang Nuclear Power Plant () is a nuclear power plant in Tangxing Village of Haiwei Township, Changjiang Li Autonomous County in the province of Hainan. It is the first power plant of its kind in the province. History Construction of the ...

at Changjiang, in the Hainan province by the end of the year. On 7 June 2021, the demonstration project, named the Linglong One, was approved by China's National Development and Reform Commission. In July, China National Nuclear Corporation (CNNC) started the construction, and in October 2021, the containment vessel bottom of the first of two units was installed. Being the world's first commercial land-based SMR prototype, the commercial operation is due to start by the end of 2026.''Installation of containment starts at Chinese SMR.''
WNN, 25 Oct 2021

Poland

Polish chemical company Synthos declared plans to deploy a Hitachi

reactor (300 MW) in Poland by 2030. A feasibility study was completed in December 2020 and licensing started with the Polish National Atomic Energy Agency. In February 2022,

NuScale Power NuScale Power is a publicly traded American company that designs and markets small modular reactors (SMRs). It is headquartered in Tigard, Oregon, United States. NuScale has been approved to build reactors in Idaho, in 2029 and 2030. The design ...

and the large mining conglomerate

KGHM Polska Miedź KGHM Polska Miedź S.A. (Kombinat Górniczo-Hutniczy Miedzi), commonly known as KGHM, is a Polish multinational corporation that employs around 34,000 people around the world and has been a major copper and silver producer for more than 50 years. ...

announced signing of contract to construct first operational reactor in Poland by 2029.

United Kingdom

In 2016, it was reported that the

UK Government ga, Rialtas a Shoilse gd, Riaghaltas a Mhòrachd , image = HM Government logo.svg , image_size = 220px , image2 = Royal Coat of Arms of the United Kingdom (HM Government).svg , image_size2 = 180px , caption = Royal Arms , date_es ...

was assessing

Welsh Welsh may refer to: Related to Wales * Welsh, referring or related to Wales * Welsh language, a Brittonic Celtic language spoken in Wales * Welsh people People * Welsh (surname) * Sometimes used as a synonym for the ancient Britons (Celtic peop ...

SMR sites - including the former

Trawsfynydd nuclear power station Trawsfynydd nuclear power station ( cy, Atomfa Trawsfynydd) is a decommissioned Magnox nuclear power station situated in Snowdonia National Park in Gwynedd, Wales. The plant, which became operational in 1965, was the only nuclear power station in ...

- and on the site of former nuclear or coal-fired power stations in

Northern England Northern England, also known as the North of England, the North Country, or simply the North, is the northern area of England. It broadly corresponds to the former borders of Angle Northumbria, the Anglo-Scandinavian Kingdom of Jorvik, and the ...

. Existing nuclear sites including Bradwell,

Hartlepool Hartlepool () is a seaside and port town in County Durham, England. It is the largest settlement and administrative centre of the Borough of Hartlepool. With an estimated population of 90,123, it is the second-largest settlement in County ...

Heysham Heysham ( ) is a coastal town in Lancashire, England, overlooking Morecambe Bay. It is a Heysham Port, ferry port, with services to the Isle of Man and Ireland, and the site of two Heysham nuclear power station, nuclear power stations. Demogra ...

, Oldbury,

Sizewell Sizewell is an English fishing hamlet in the East Suffolk district of Suffolk, England. It belongs to the civil parish of Leiston and lies on the North Sea coast just north of the larger holiday village of Thorpeness, between the coastal towns ...

Sellafield Sellafield is a large multi-function nuclear site close to Seascale on the coast of Cumbria, England. As of August 2022, primary activities are nuclear waste processing and storage and nuclear decommissioning. Former activities included nucle ...

, and

Wylfa Wylfa nuclear power station ( cy, Atomfa'r Wylfa) is a Magnox nuclear power station undergoing decommissioning. Wylfa is situated west of Cemaes Bay on the island of Anglesey, off the northwestern coast of Wales. Construction of the two 490MW n ...

were stated to be possibilities. The target cost for a 470 MWe

unit is £1.8 billion for the fifth unit built. In 2020, it was reported that 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. An additional £210 million was awarded to Rolls-Royce by the British government in 2021, complemented by a £195 million contribution from private firms. 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.

United States

In December 2019, the

Tennessee Valley Authority The Tennessee Valley Authority (TVA) is a federally owned electric utility corporation in the United States. TVA's service area covers all of Tennessee, portions of Alabama, Mississippi, and Kentucky, and small areas of Georgia, North Carolina ...

was authorized to receive an Early Site Permit (ESP) by the

for siting an SMR at its

Clinch River The Clinch River is a river that flows southwest for more than through the Great Appalachian Valley in the U.S. states of Virginia and Tennessee, gathering various tributaries, including the Powell River, before joining the Tennessee River in Ki ...

site in Tennessee. This ESP is valid for 20 years, and addresses site safety, environmental protection and emergency preparedness. This ESP is applicable for any light-water reactor SMR design under development in the United States. The Utah Associated Municipal Power Systems (UAMPS) announced a partnership with

Energy Northwest Energy Northwest (formerly Washington Public Power Supply System) is a public power joint operating agency in the Pacific Northwest, northwest United States, formed in 1957 by Washington (state), Washington state law to produce at-cost power for ...

to explore siting a

reactor in

Idaho Idaho ( ) is a state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Montana and Wyom ...

, possibly on the

Department of Energy A Ministry of Energy or Department of Energy is a government department in some countries that typically oversees the production of fuel and electricity; in the United States, however, it manages nuclear weapons development and conducts energy-rel ...

Idaho National Laboratory Idaho National Laboratory (INL) is one of the national laboratories of the United States Department of Energy and is managed by the Battelle Energy Alliance. While the laboratory does other research, historically it has been involved with nu ...

. The

Galena Nuclear Power Plant The Galena Nuclear Power Plant was a proposed nuclear power plant to be constructed in the Yukon River village of Galena, Alaska. If it had been built in the projected timeframe, it would have been the first non-military nuclear power plant built i ...

Galena, Alaska Galena () (''Notaalee Denh'' in Koyukon) is a city in the Yukon-Koyukuk Census Area in the U.S. state of Alaska. At the 2020 census the population was 472, slightly up from 470 in 2010. Galena was established in 1918, and a military airfield was ...

was a proposed micro nuclear reactor installation. It was a potential deployment for the

Toshiba 4S The Toshiba 4S (Ultra super safe, Small and Simple) is a micro sodium reactor design. General description The plant design is developed by a partnership that includes Toshiba and the Central Research Institute of Electric Power Industry (CRIEP ...

reactor.

Romania

On the occasion of

2021 United Nations Climate Change Conference The 2021 United Nations Climate Change Conference, more commonly referred to as COP26, was the 26th United Nations Climate Change conference, held at the SEC Centre in Glasgow, Scotland, United Kingdom, from 31 October to 13 November 2021. The ...

, the state-owned Romanian nuclear energy company Nuclearelectrica and NuScale signed an agreement to build a power plant with six small-scale nuclear reactors on the site of a former coal power plant, located in the village of Doicești, Dâmbovița county, 90 km North of 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 will generate 462 MWe, securing the consumption of about 46.000 households and will help avoid the release of 4 million tons of CO₂ per year.

References

External links

DOE Office of Nuclear Energy

American Nuclear Regulatory CommissionWorld Nuclear AssociationAmerican Nuclear SocietyInternational Atomic Energy AgencyOverview and Status of SMRs Being Developed in the United States
{{Nuclear fission reactors Nuclear power reactor types Small modular reactor

Background

General aspects

Licensing

Scalability

Siting/infrastructure

Flexibility of SMR

Safety

Proliferation

Designs

Thermal-neutron reactors

Fast reactors

Technologies

Cooling

Thermal/electrical generation

Load following

Waste

Safety

Flexibility of SMR

Economics

Licensing

Nuclear proliferation

List of reactor designs

Proposed sites

Canada

China

Poland

United Kingdom

United States

Romania

References

Further reading

External links