Today, the whole technological world is looking for solutions to overcome the problems of mankind. Significant attention is paid to the development of new technologies that can optimize, secure and adjust life on the planet. Highly developed countries are spending many costs on research and new engineering efforts. In particular, the United States recently announced its intention to resume funding for international programs aimed at developing civil nuclear technologies.
The developers of new reactor technologies are convinced that the future of nuclear energy lies in small modular reactors (SMR), since they have a set of advantages over their predecessors – high-capacity units. Currently, more than 50 designs of low-capacity units are at various stages of development in the world.
According to the definition of the International Atomic Energy Agency (IAEA), small reactors are reactors with a capacity of up to 300 MW and which consist of modules that are produced at the manufacturing plant before the supply and mounting. The concept of SMR and their use in electricity production have been the subject of discussion by scientists, government officials and nuclear experts for many years. The idea of using SMR seems increasingly justified and economically feasible against the background of technological breakthroughs of the last decade.
The reality for SMR implementation is brought closer by the factors that have recently become apparent in global energy: increasing demand for electricity needed for economic growth, as well as growing demand for energy security and low-carbon energy in the fight against the climate change. SMRs have a number of advantages over traditional nuclear power plants (NPPs): they can take part in a diversified energy balance, operate without a connection to the grid and be used to generate heat for process needs, water desalination and hydrogen production.
Prospects for implementation in the world
There are two nuclear power plants in Argentina, which produce 1 627 MW of energy. One of them, the two-unit Atucha NPP (Atucha-1 of 335 MW and Atucha-2 of 692 MW) uses pressurized heavy water reactors (PHWR). The nuclear power plant is located in Lima (Buenos Aires Province). Another power plant is Embalse NPP (600 MW), which also uses PHWR reactor, is located in Embalse (Cordoba Province). The construction of CAREM SMR started on the Atucha site in February 2014.
CAREM small modular reactor is a joint project of the National Atomic Energy Commission of Argentina (CNEA) and the INVAP S.E. Company. The reactor development had the status of a national project: the supply of materials and components for the plant was performed by local companies
The project is based on an integrated light-water reactor (LWR) with an electrical capacity of 30 MW and thermal capacity of 100 MW. Core cooling by natural circulation, in-vessel mechanisms of control rod regulation, as well as safety systems with an emphasis on passive protection mechanisms are among the key characteristics of this design. CAREM design minimizes unstable components and risks of interaction with the environment.
The first public presentation of CAREM design took place in 1984 during the IAEA conference in Peru. The project was terminated for political reasons, but later it was resumed as part of Argentina’s 2006 nuclear reactivation planning.
It is necessary to state that a nuclear power plant based on CAREM SMR is not just a project on paper. It is currently under construction in the area of the city of Sarat in the northern part of the Buenos Aires Province near Atucha-1 NPP.
The developers have previously called 2022 as the date of commissioning of the innovative reactor. However, because of the fact that today construction is suspended due to economic reasons, the exact date is unknown.
There are 19 NPPs with a total capacity of 13 553 MW in operation in Canada. Regional authorities and electricity suppliers have decided on long-term operation of several Canadian heavy-water nuclear reactors (CANDU) through large-scale modernization, which will allow compliance with future electricity needs.
Previously, the Canadian Nuclear Laboratory (CNL) announced in its report on the prospects for national nuclear energy development its intention to build a small modular reactor on one of its sites by 2026. In response, proposals were received from 80 organizations and individuals from Canada and other countries, including SMR developers, who applied to the Canadian Nuclear Safety Commission (CNSC) for a license.
The SMR Development Program was developed in the country, which is improving rapidly: developing companies are quick to respond to the results of new scientific research and seek for opportunities for their practical implementation. In addition, the world recognized regulatory authorities that support the use of new technologies take into account the interests of the developers.
Developers of reactor technologies pay peculiar attention to the economic characteristics of SMR. A total of 19 different SMR concepts have been proposed as potential demonstration projects, 16 of which envisage the placement of a reactor on one of the Canadian Nuclear Laboratory sites, and three projects involve the possibility of commercial operation in Canada.
The Canadian Nuclear Safety Commission (CNSC) offers Canadian and foreign developers planning to apply for receiving a license for the construction and operation of a new NPP to use the procedure for preliminary assessment of the project, when the Commission evaluates the reactor technology used by the developer. The preliminary assessment does not guarantee that the project will be approved.
The first stage of assessment takes 12 to 18 months, during which the project is assessed in terms of compliance with Canadian regulatory framework. The second stage lasts 24 months to reveal possible fundamental reasons for refusing to issue a license. During the third stage, the developers have the opportunity to study the results of the second stage of assessment and make the necessary changes to the project.
According to the Commission, applications for preliminary assessment of projects have been received from more than 10 developing companies. These include the integral molten salt reactor IMSR 200 MW by the Terrestrial Energy Inc., MMR-5 and MMR-10 high-temperature gas-cooled nuclear reactors by the Ultra Safe Nuclear Corporation, SEALER lead-cooled nuclear reactor 3 MW by the LeadCold Nuclear Inc., ARC-100 liquid sodium reactor by the Advanced Reactor Concepts Ltd., salt reactor 300 MW by the Moltex Energy, light-water SMR-160 by the Holtec International, water-cooled pressurized-water reactor by the NuScale Power LLC, etc.
Let us consider a few of them.
Therefore, the first one to consider is the NuScale, the project of which is in the final stage of licensing in the USA and is likely to become a flagship in SMR construction. This is a development of the US Company that is called the NuScale Power.
One NuScale power unit can contain up to 12 separate modules (reactors) providing up to 720 MW of electrical power.
The developers claim that NuScale reactor has a very high level of safety, which is provided by passive systems, and the probability of human error is reduced to almost zero. Fuel reloading and maintenance of one NuScale module does not affect the operation of other modules and takes about ten days.
In addition, the reactor provides for a rapid change of power in a wide range – from 20 to 100% and a short interval for power increase after its scheduled shutdown, which is about 13 hours. This will allow the reactors to be used as load following capacities for renewable generation.
The economic performance of NuScale reactors is also attractive: the estimated cost of constructing NuScale NPP is almost half that of high-capacity power units, and the number of personnel servicing NPPs with 12 NuScale modules is about 300 people.
Holtec International (USA), known worldwide as a supplier of containers and systems for spent nuclear fuel storage and as a designer of ISF-2 and CSFSF in Ukraine, has decided to become one of the developers of reactor technologies by means of SMR-160 design.
The first data that Holtec was working on SMR appeared in 2011, when the reactor was called HI-SMUR 140. Later, the project evolved and was replaced by SMR-160.
The company characterizes SMR-160 as a small modular reactor with an electrical capacity of 160 MW, “the design of which ensures safe operation, including on sites with limited water supply and limited size, where for these reasons large reactors cannot be constructed. They also have unique opportunities for use in industry in conditions where high-capacity nuclear power plants are not suitable”.
One of the advantages of the company is the level of safety “Walk way safe”. This means that in the event of an accident that occurred for any reason (including sabotage or terrorist attack), the reactor will shut down and go into a safe state without human interference.
According to the project, the reactor will be located underground at an elevation of 14 meters. In addition, dry spent fuel storage facility with a service life of up to 120 years will be placed below ground.
The design life of such a reactor is 80-100 years. The construction time is 2-3 years.
Westinghouse SMR is a design of a light-water small modular reactor of the company of the same name, with the integrated equipment layout focused on regions with unstable energy supply.
According to the developer, passive safety systems and tested components implemented in AP1000 reactor design are used in the facility to achieve the highest level of safety. In fact, Westinghouse SMR is a small copy of its “older brother”, which offers some licensing advantages to this design over competitors.
The plant is capable of generating <225 MW of electrical energy and 800 MW of thermal energy, which can be used for technological needs, provide central heating, operate without a connection to the grid (for example, in shale oil production sites), and be used for coal liquefaction.
Nuclear power plant based on Westinghouse SMR is a modular structure where all components can be easily moved by road, water or rail, creating additional conditions for its placing in areas with underdeveloped power grids.
The conceptual design of the reactor was developed in 2015. The developing company is finalizing the project and is preparing to apply for its certification to the U.S. Nuclear Regulatory Commission.
In addition, Westinghouse Company is currently developing the eVinci microreactor, which is a small modular reactor of a new generation for decentralized remote settlements. Like the previous type, this reactor can be easily transported, and the period of its installation on the site is only a week.
Westinghouse assures that the microreactor can be used as a mobile generator, its thermal and electrical capacity is from 1 MW to 5 MW. The design life of such a facility is 40 years, and the reactor can operate without a reloading for 10 years. The Company plans to put eVinci into operation by 2024.
United States of America
The United States of America is the largest producer of nuclear energy (30% of the world’s volume). In total, 98 nuclear power units located in 20 states operate in the country. The average age of reactors is 37 years. The capacity of one power unit averages 1000 MW.
The U.S. Nuclear Regulatory Commission considers preliminary applications submitted by the developers of (light-water) SMR, among which there are the NuScale Power Company with the low-capacity reactor, SMR Inventec, LLC (a subsidiary of the Holtec International Company) with SMR-160 and BWXT mPower, Inc.
When one speak about small modular reactors that are the most advanced in development, it is necessary to mention two more technologies.
At the end of 2019, the US-Chinese Company “GE Hitachi Nuclear Energy” started the process of licensing its small boiling reactor design BWRX-300 in the USA.
BWRX-300 with a capacity of 300 MW is a small version of ESBWR boiling water reactor with a capacity of 1520 MW developed by GEH, which was successfully certified by the U.S. NRC in 2014. The BWRX design uses the same design solutions as ESBWR. The first certification of BWRX-300 design is planned in Canada.
According to GEH, BWRX-300 reactor requires up to 60% less capital costs per megawatt of power compared to other small reactor designs or current high-capacity reactors. This is the tenth model of a boiling water reactor for General Electric. The Company has been developing commercial nuclear reactors since 1955.
As of May 2020, 48 nuclear power units at 17 NPPs with a total capacity of 45.6 GW are in operation in the country. Thirteen power units are under construction and the construction of about 30 units more is planned.
Several low-capacity nuclear reactors are under development to achieve China’s energy policy tasks and objectives. Within China’s national development program, the following SMR models are being developed: HTR-PM (two 250 MW (t) reactors and one 211 MW (e) turbine), ACP100 (125 MW (e) / 385 MW (t)), CAP200 (200 MW (e) / 660 MW (t)) and ACPR50S (50 MW (e) / 200 MW (t)).
Three northeastern provinces of Liaoning, Jilin and Heilongjiang, where there is a shortage of heat and energy, and the coastal provinces of Zhejiang, Fujian and Hainan, which need energy and drinking water, are potential consumers. It is also planned to supply energy to other provinces, including Hunan and Jiangxi. In addition, the option of using a floating nuclear power plant in the Bohai Bay is being considered. The North Africa and the Middle East are considered among foreign markets, where such types of reactors can be used to generate energy, heat, steam and drinking water.
Korea focuses its development on the Middle East…
The project of the Korean Atomic Energy Research Institute (KAERI) SMR SMART is a light-water “modular advanced reactor with an integrated system” aimed at electricity generation, as well as water desalination. The design of the reactor is designed so that the pressurizer, steam generator and reactor coolant pumps (RCP) together with the core are located in a single vessel.
The design envisages eight steam generators with spirally twisted heat exchange tubes, through which superheated steam passes. Pumping of the coolant is ensured by four sealed RCPs.
Such a power plant is capable of producing 100 MW of electricity to meet the needs of a city with a population of 100 000 people and of desalinating 40 000 tons of seawater. Thermal capacity is 330 MW.
South Korean scientists have been developing this technology during 22 years. The design was approved by the Korean regulatory authority in 2012.
KAERI planned to build a demonstration plant SMART, which should have worked in 2017, but the project was terminated due to lack of orders. In general, the situation has changed a bit. The developer is focusing its modular reactors on the Middle East. In particular, a Memorandum of Understanding with Saudi Arabia on the Commercialization and Licensing and Construction of the SMR SMART in this country was recently signed.
What about Ukraine?
The Energy Strategy of Ukraine until 2035 envisages the need for the selection of reactor technologies to construct new nuclear power units to replace NPP capacities, which will be decommissioned.
At present, the SNRIU is actively studying the experience of regulatory authorities of other countries, primarily the United States, in licensing small modular reactors and regulatory support of their construction.
In the summer of 2019, the technical support organization of the SNRIU, the State Scientific and Technical Center for Nuclear and Radiation Safety, became one of the signatories of the agreement on the establishment of the Consortium with the U.S. company Holtec Int. for the implementation of small modular reactor technology in Ukraine. However, this area has not been developed for certain reasons.
At the end of 2019, the SSTC NRS together with the SNRIU performed significant efforts in exchanging experience with colleagues from the USA, including the NuScale Company that is the developer of small modular reactor technology. In early 2020, the SSTC NRS and the NuScale Power signed a Memorandum of Understanding, which will launch activities on the assessment of national regulatory and design documents related to the implementation of NuScale technology for the construction of SMR in Ukraine. The management of the developer expressed readiness to promote such activities.
This cooperation supported by the U.S. Department of Energy and the U.S. State Department made it possible to carry out a workshop in Ukraine on the implementation of new technologies in nuclear energy of the country and the official presentation of NuScale technology in Eastern Europe.
The position of the Energoatom that is the only NPP operator in Ukraine on the development of new technologies is still unknown. No programs have been submitted to consider the possibility of SMR introduction into the national nuclear industry. However, taking into account the age of nuclear power plants operated in Ukraine, the issue of new technology development is urgent.
Since SMR are of load following mode and low-carbon type of generation, this technology can be considered alongside other sources of renewable energy in the face of climate change. This is, at least, the position of small modular reactor technology in the world.
New challenges: SMR spent fuel management
The process of spent fuel management needs special attention. According to researchers involved into nuclear energy area, the issue of SMR spent fuel depends on the design of a specific reactor, as well as on the existing procedure for spent fuel management in the country.
Countries with nuclear energy programs deal with spent fuel management for decades. They have gained a lot of experience and have the proper infrastructure. For these countries, the management of SMR spent fuel will not be a problem, if a decision is made to use SMR based on available technologies.
Thus, if small modular reactors are operated with the same fuel as traditional nuclear power plants, their spent fuel can be managed in the same way as spent fuel of large reactors.
As for SMR, which is based, for example, on high-temperature gas-cooled reactors that use fuel packed into graphite prismatic blocks or graphite spheres, even for them some countries with nuclear power plants already have solutions that allow spent fuel storage and management. Already available infrastructure can be used for this purpose or it can be easily adapted to new streams of radioactive waste.
Countries that have just started developing nuclear energy sector should consider the issue of spent fuel management and create the appropriate infrastructure. This is necessary even if they prefer traditional nuclear power plants or SMR based on existing technologies.
According to the IAEA Division of Nuclear Fuel Cycle and Waste Technology, they will face additional difficulties if they select first-of-the-kind or less established technologies, as there will be less experience and fewer benchmarks to manage the entire fuel cycle.
In general, decisions on the management of spent fuel and radioactive waste resulting from SMR operation will be considered as the most important factors considered in the selection of this or that technology together with the reliability of fuel supplies.
Some SMR structures can reduce the amount of activities related to spent fuel management. Properly constructed power plants require a lower frequency of reloading, that is every 3-7 years, as compared to 1-2 years for traditional power plants, and some are designed so as to operate without reloading up to 30 years. However, even in such cases, some volumes of spent fuel will remain and will still need to be disposed of properly.
Currently, engineers and designers have a unique opportunity to find solutions to improve the management of spent fuel and radioactive waste of SMR in the early stages of development. After all, such an approach will help eliminate the uncertainties associated with the final stage of the fuel cycle and reduce costs.
Uatom.org Editorial Board