SMALL AND MEDIUM REACTORS1

In operation2 139
Under construction 8
Number of countries with SMRs 28
Generating capacity, GW(e) 61.5
Operating experience, reactor-years 5427

China's HTR-10 is undergoing power ascension testing near Beijing. First criticality was achieved in December 2000. This plant will be utilized to evaluate a wide range of nuclear power applications including electricity production, steam and district heat generation, and high temperature industrial processes. (Credit: Institute of Nuclear Energy Technology) There is a renewed interest in Member States in the development and application of small and medium sized reactors (SMRs) In the past, the trend in nuclear power reactor technology development showed an emphasis towards large reactors due to the economies of scale, which produced reactor designs on to 1600 MWe. A development of SMRs points into the opposite direction, i.e. towards smaller outputs with an equivalent electrical power of less than 700 MWe.

In the early decades, civil nuclear power essentially borrowed from the experience of reactors for nuclear submarines, which came first and were essentially small-capacity reactors. Since 1970’s, the major focus for nuclear power was on the design and construction of nuclear plants of increasing size, with average size levelling out at about 1000 MWe with a tendency for further increase. This was and is generally appropriate for many industrialized countries, which could add generation capability to their electrical grids in larger increments and benefit from the construction costs reduced due to scale factor. However, it might be not appropriate for many developing countries that have small electricity grids, limited capacity for investment and less developed infrastructure.

At the moment, there is no general consensus on the future role of SMRs. A balanced view is that SMRs are an option, not a universally best option that will suit for all cases. Large utilities with a big grid size will still favour large units for reasons of the economy of scale. On the other hand, many developing countries have small electricity grids and limited turnover of capital in the energy market. In this context, SMRs may become the only affordable nuclear power option for such countries.

In industrialized countries, the market deregulation and resulting competition drives the utilities toward shorter time of capital recovery and lower financial risks, which could perhaps be achieved by enabling the incremental capacity addition to a network that would match the incremental increase of demand. SMRs may also attract a concern of the utilities in this context. On the other hand, an essential simplification of plant operating and maintenance requirements may be requested to justify for, say, the reduced number of control rooms at a site with several modular reactors, etc.

Last but not least, SMRs are also the preferred option for non-electrical applications of nuclear energy for both near-term, such as desalination of seawater or district heating or longer-term, e.g. hydrogen production and other process heat applications. Therefore, it is not a surprise that more than 50% of the nuclear energy systems selected by the Generation IV International Forum (GIF) fit into a SMR range. However, the Generation IV systems are targeted for deployment around 2030 and, therefore, do not address the urgent needs of developing countries.

Some SMRs also offer the possibility of very long core lifetimes with reduced core power density, burnable absorbers or high conversion ratio in the core. An infrequent refuelling interval may provide certain guarantees of sovereignty for those countries that have a less developed infrastructure and would prefer to lease fuel rather than master an autonomous fuel cycle. For more advanced designs, such as some Generation IV systems, it is noted that lifetime reactor operation without on-site refuelling might be an attractive solution for the implementation of adequate safeguards in a scenario of large-scale global deployment of nuclear power.

In order to beat the economy of scale, SMRs have to incorporate specific design features that result into simplification of the overall plant design, modularization and mass production. A safety-by-design approach3 aims to eliminate the possibility of accidents from occurring rather than deal with their consequences, thus significantly improving the defence-in-depth and safety characteristics. This approach is illustrated by several designs of integral type small PWRs developed around the world. Several other approaches under consideration include increased use of the inherent and passive features for reactivity control and reactor shut down, decay heat removal and core cooling, and the reliance on an increased margin to fuel failure achieved through advanced high-temperature fuel forms and structural materials. These approaches may be common to several reactor designs or even several reactor lines and, therefore, could benefit from being developed on a common or shared basis. To build and operate an NPP, any country should establish a certain infrastructure, including relevant legal and regulatory norms and institutions, as well as human resource and certain industrial capacities. SMRs are no exception here. Certain infrastructure developments, such as establishment of design certification/licensing reciprocity regimes between different countries, creation of legal and institutional provisions for fuel leasing could be of benefit for all innovative reactors, not SMRs only. However, some infrastructure changes are mentioned as being of special benefit namely to SMRs, among them:

At the moment, 146 SMRs are operated worldwide, accounting for 61 GW(e) of electricity generation, and 12 more are under construction. These are mostly earlier generation reactors still in operation and a few prototype or tests reactors, generally not representative of those advanced SMR designs that are considered for future deployment. On the other hand, more than 50 concepts and designs of advanced SMRs are under development in more than 15 IAEA Member States representing both industrialized and developing countries. SMRs are under development for all principle reactor lines, i.e., water cooled, gas cooled, and liquid metal cooled, as well as for some non-conventional combinations thereof, and there are growing expectations of an increased support from the IAEA to interested Member States in the definition of common technology and infrastructure development needs and deployment strategies for such reactors.

With these developments in mind, the IAEA’s Division of Nuclear Power prepares a new report on the status of innovative SMR designs and a dedicated report on small reactors without on-site refuelling. These reports will present the designs of SMRs in a balanced way according to a common new outline, which takes into account design and technological provisions for the resolution of the issues currently accepted as important for nuclear power and also provides for the description of applications, fuel cycle options, and special features relevant for each SMR design or concepts.

A Coordinated Research project (CRP) on development of small reactors without on-site refuelling (2004-2007) has been started late in 2004 with 17 participants from 11 Member States. The objective of this CRP is to increase the capabilities in IAEA Member States to achieve progress in the development and deployment of small reactors without on-site refuelling by formulating major requirements for such reactors and increasing international cooperation for the development of key enabling technologies for such reactors, including long-life cores, inherent and passive safety features and systems, and design and regulatory provisions to reduce or eliminate off-site emergency planning. Specifications and broad requirements for such reactors will be defined based on the analysis of demands and market conditions for specific representative regions.

Also under preparation are TECDOCs on definition of plant safety design options to cope with external events, review of passive safety design options for SMRs and review of the experience and options relevant for validation, testing and demonstration of passive systems for SMRs.

In 2006-2007 a dedicated project on common technologies and issues for SMRs will be performed, including a new CRP on identification of competitive technological options for SMRs.

On 7-11 June 2004 the IAEA convened a Technical Meeting on Innovative Small and Medium Sized Reactors: Design Features, Safety Approaches and R&D Trends, which was attended by 15 experts from 12 Member States and produced an insight on the current status of technology development and implementation plans for SMRs. The final report of this meeting was published as IAEA-TECDOC-1451. (Download IAEA-TECDOC-1451).

COORDINATED RESEARCH PROJECT ON SMALL REACTORS WITHOUT ON-SITE REFUELLING

The contact for SMRs is: V.V.Kuznetsov@iaea.org.



1 According to the classification adopted by IAEA, Small Reactors are reactors with the equivalent electric power less than 300 MW, Medium Sized Reactors are reactors with the equivalent electric power between 300 and 700 MW

2 Reactor data presented in this Brochure are results as of June 2005 and are derived from the IAEA’s Power Reactor Information System

3 Safety by design is a trademark of the IRIS project of an integral type pressurized water SMR developed by an international consortium led by Westinghouse (USA)

4 The factors affecting sovereignty may be energy security as well as economic competitiveness.