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Key principles

The development of small modular reactors is well underway.
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The Research Institute for Nuclear Systems for Low-Carbon Energy Production (IRESNE) is actively contributing to the development of small modular reactor (SMR) concepts. The CEA’s strength lies in its accumulated wealth of knowledge and skills in conventional nuclear reactors, but it also has expertise in naval propulsion reactors and research reactors like material testing reactors (MRT). All the innovative developments resulting from research on these different reactor technologies provide the foundations needed to develop SMRs.

What are SMRs?

Main features of SMRs.

As their name indicates, these reactors are small-scale, modular and generate low power, typically between 150 to 300 MWe, i.e. 5 to 10 times less than an EPR. Their difference with a PWR-type reactor (second- and third-generation) lies in their design, which is based on simpler and highly standardised approach. Their modules can be prefabricated and then transported by standard means to their intended location, thereby reducing the duration of SMR construction phases. SMRs will benefit from series-production effects (due to standardised or reproducible operations), which will compensate for losses in economies of scale achieved by larger units like EPRs.​

Why develop such a reactor concept?

This new reactor configuration reflects changes in the way people are using electricity worldwide.

• Meeting a new demand:
  The SMR concept quickly gained ground with the growing need for electricity while reflecting the world’s commitment to fight global warming. A nuclear reactor represents an initial high investment cost that is directly related to its complexity and size (power). From this perspective, SMRs have an advantage over high-power reactors because of their lower initial investment cost. Another advantage lies in the possibility of being able to build these reactors in locations that do not have well-distributed high-power grids. Last of all, they could replace coal-fuelled plants of equivalent power at their end of life, benefiting from the location and the power distribution system already in place.
  

• In addition to electricity generation:
  SMRs are not only easy to transport and install, but also modular, which makes them versatile enough for other purposes. Their thermal power - usually 500 MWth - is well-suited to be used for water desalination, hydrogen production or even heat production. Nuclear energy is now capable of providing much more than its initial purpose of generating electricity. New applications are possible.
  

• Electricity generation in isolated locations:
  The small modular reactor technology has the added advantage of being transposable to isolated regions, thereby meeting local needs for a self-sufficient power source and thus circumventing the need to roll out kilometres and kilometres of costly high-voltage transmission lines.
  
  

Advantages

SMRs offer numerous advantages, which explains the current level of investment devoted to their research and development.

• A modular concept:
  SMRs are designed on the basis of a series of modules. These modules can be manufactured in series, which means cost savings can be made through economies of scale.
  Standardised manufacturing processes also make it possible to reduce construction times on site and therefore construction costs. Small prefabricated modules also simplify transport operations to the site where the reactor is to be built.
  

• Reduced waste:
  The fuel burn-up rate is higher in small modular reactors using fast neutrons, which reduces the quantity of resulting radioactive waste. This type of small fast reactor is called an advanced modular reactor or AMR.
  

• Technical features:
  The reactor’s architecture has been simplified to allow for the small size of this technology. The primary loop has been eliminated, thus reducing the risk of a primary loss-of-coolant accident.
  The core is encased in a large reactor vessel. Added to the low power produced, this feature makes it possible to retain the corium inside the vessel in the event of core meltdown. SMRs are also designed with passive cooling systems, an enhanced safety feature developed from operating experience and know-how. For instance, these systems require no manual operations to remove the decay heat from the reactor core in the event of a loss of power supplies. Furthermore, the integration of immersed control rod systems significantly reduces the risk of a reactivity insertion accident (RIA). These control rods alone absorb the neutrons to control the chain reaction inside the reactor; they make it possible to eliminate the use of soluble boron, which simplifies both reactor operation and effluent treatment. Lastly, the SMR design is such that the building can be partially or fully buried in the ground, which is a bonus safety feature. Buried structures reduce the risk of building damage due to the impact of an external hazard, e.g. aeroplane crash.​
  
  
  

The NUWARD^TM project

NUWARD^TM: the French SMR.

The French Alternative Energies & Atomic Energy Commission (CEA), and more specifically IRESNE, is working in close collaboration with its long-standing industry partners on the development of the French SMR called NUWARDTM (NUclear forWARD). This collaboration is managed by EDF and also includes Naval Group and TechnicAtome. The project was first presented on 17 September 2019 at the annual general meeting of the International Atomic Energy Agency (IAEA). The SMR project was given the green light after promising feasibility studies and the pre-conceptual design phase, which also included identifying a model of economic growth. This project is currently in its conceptual design phase, with the objective of developing an SMR based on the pressurised water reactor (PWR) technology with a power of 170 MWe (megawatt electric). The intention is to build two identical SMR units per site, i.e. 340 MWe in total. The skills, know-how and expertise of the all partners focused on this project have made it possible to produce an advanced reactor that demonstrates the highest levels of nuclear safety while being competitive and showcasing some remarkable innovations.​​​​​

Learn more about research on small modular reactors at IRESNE.