Small Nuclear Reactors: Issues and Challenges

In recent years, small nuclear reactors have seen a resurgence of interest around the world. For a long time, these small reactors were de facto hardly used outside military operations, especially for submarines. Today, the situation has changed with a much more civil use of this technology in a context of energy transition. Small nuclear reactors (SMRs) could thus promote the integration of intermittent renewable energies into the energy mix.

For the nuclear industry, this is a major paradigm shift towards more flexible production. For decades, the industry has been characterized by a race for high power reactors. The objective was to reduce the combustion rate in order to maximize the power per fuel used. This approach now seems to be widely questioned after the failures of the EPR in France and the AP-1000 in the United States.

However, this substitution of large reactors for small units is still largely hypothetical. Numerous technical constraints are thus an obstacle to the large-scale deployment of these small reactors. Under these conditions, what are the issues and challenges of small nuclear reactors?

The advantages of small nuclear reactors

Small nuclear reactors are defined as fission reactors with a power of less than 300 MW. Because of their small size, they can be manufactured in a modular fashion in the factory. In addition, they can be transported in individual parts, allowing them to be installed directly on the site of installation. These characteristics give SMRs a number of advantages over higher power reactors.

First, small reactors benefit from an integrated technological architecture that simplifies fuel use. Thus, the entire primary circuit is installed inside the tank, which promotes stability. The civil engineering costs required to secure the reactors are therefore greatly reduced. This point is fundamental, because it is the slippage in these costs that explains the failure of the third generation reactors.

In addition, the modular construction of the SMRs favors its implementation in isolated regions, as the assembly is done directly on site. In this respect, small reactors can enable the nuclear industry to conquer new markets. To this end, Rosatom has used small reactors to supply regions in Siberia by means of a floating barge. Similarly, SMRs are particularly coveted by Middle Eastern countries to supply their desalination plants.

These technical benefits are minor, however, when compared to the financial gains that could be achieved through RMS. According to an MIT study, these small reactors result in a 20 to 40 percent reduction in costs. The return on investment is also faster, which makes the technology more attractive financially. As a result, there has been a frenzy of investment in RMS in recent years.

The global race for small nuclear reactors

Interest in small nuclear reactors continues to grow around the world. Today, we are witnessing a real technological race to dominate this new part of the nuclear industry. At present, only Russia has put into service an SMR which is a modernized version of the Soviet KTL-40. However, this reactor has experienced many delays and can only be used on a barge, which makes it less attractive.

The Russian RITM-200 project seems much more competitive, but it is still in the development stage. China has also entered the race with CGN’s ACPR50 and CNNC’s ACP100. For the moment, these two reactors have not yet been commercialized. Another important player is South Korea, which is developing an SMR called SMART for Saudi desalination plants.

In recent years, new players have emerged in the race for small reactors. Argentina is one such country with its CAREM project currently under construction. Canada, with Terrestrial Energy’s IMSR, and France, with the Nuward project, are also positioning themselves on this technology. Finally, the United States has seven SMRs under construction, with the NuScale project currently the most advanced.

However, all of these reactors are not expected to be operational before the 2030s. This delay can be explained by the time required for certification, but above all by technical constraints that have not yet been resolved.

Constraints on small nuclear reactors

The competitiveness of small nuclear reactors will depend largely on the economies of scale achieved. The manufacturers will have to be able to market sufficient volumes in order to make their investments profitable. One of the keys to success will be to facilitate the international standardization of the parts used. In this light, technological competition between states will likely turn into future rivalry for the establishment of standards.

For the time being, the main difficulty lies in refueling. This is because a low fuel load significantly limits the service life of the SMRs before they are returned to the factory. All the research work will therefore consist of increasing this period of use without having to constantly recharge the fuel.

To achieve this goal, Framatome and GA-EMS announced on October 14 their FMR small reactor project. This SMR will allow the reactor to operate for 9 years, which represents a real technological advance. It is expected to be commercialized in the mid-2030s. GA-EMS also announced the EM2 project designed to be used for 30 years without charging.

The issue of fuel recharging therefore appears to be central to the deployment of RMS worldwide. At present, the technology is still in the development stage despite the interest of investors. We will probably have to wait until the next decade to see the concrete impact of SMRs for the nuclear industry.

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