SMALL MODULAR REACTORS (SMR)

Definition of SMR #

Small comes from the physical size of the reactors. An SMR is a fraction of the size of a conventional nuclear power reactor.

Modular means that the reactor’s components are factory-manufactured as modules and transported as a unit to where they are to be installed. They are a replica of a prototype as they are serial produced in exact copies based on that design.

Reactor. SMR uses fission technology. According to the International Atomic Energy Agency (IEA), the reactor must have a maximum capacity of around 300 megawatts (MW) per unit to be designated as SMR. It is 3 approx. times less than conventional larger reactors [1]. SMR’s capacity can always be adjusted by adding new modules.

SMR types #

SMRs are not a distinct type of reactor, but rather a family of different reactor designs. More than 70 SMR designs are being developed around the world [2]. SMR can be based on conventional Generation III+ and advanced Generation IV designs.

BWRX-300 #

The BWRX-300 is a 300 MWe Boiling water reactor (BWR) and the 10th development of the GE Hitachi Nuclear Energy (GEH) BWR, hence the “X” in its name [3].

BWRX-300 like most boiling water reactors use low pressure water to remove heat from the core. A distinct feature of this reactor design is that water is circulated within the core by natural circulation. This is in contrast to most nuclear reactors which require electrical pumps to provide active cooling of the fuel. This system has advantages in terms of both simplicity and economics [4].

AP-300 #

The Westinghouse AP300 SMR is a 300 megawatts single-loop pressurized water reactor (PWR) scaled down from the larger AP1000 reactor. Moreover, like the AP1000, the AP300 is designed to operate for an 80+ year life cycle [5].

Rolls-Royce UK-SMR-470 #

The Rolls-Royce SMR, also known as the UK SMR, is being developed by the Rolls-Royce company in the United Kingdom [6].

It is a close-coupled three-loop pressurized water reactor (PWR) design with an power output initially designed to be 440 MWe, and subsequently increased to 470 MWe which is above the usual range considered to be a SMR.

Holtec smr-160 #

The SMR-160 is a pressurized water reactor (PWR) design with an power output initially designed to be 160 megawatts with a passive core cooling system without pumps or valves. It uses standard size PWR enriched uranium fuel [7]. Holtec claims that their system is simpler than the currently operating reactors, with no need for active pumps, which makes them more reliable.

Copenhagen Atomics thorium molten salt reactor #

The Danish company Copenhagen Atomics small modular thorium molten salt reactor design with an output of 100 megawatts (MW) [8]. it is small enough to allow for mass manufacturing and assembly line production.

Safety #

The Generation III+ SMR is designed with passive cooling, meaning no human intervention or external power is required to shut down the reactor when necessary. This significantly increases the safety of the reactor, as a power failure or human error would not cause a loss of cooling. [9, 10].

Smaller nuclear plants produce proportionally less decay heat and easier to cool cores with a smaller number of traditional fuel assemblies.

Economy #

The economic opportunity for SMRs is driven by four factors: power scaling; standardisation; modular build; and production learning. These drivers will affect different components of the capital cost in different ways.

SMRs have the potential to reduce the upfront capital costs associated with larger nuclear power plants. The modular design approach and the potential for factory manufacturing can help control costs and improve cost predictability.

In 2023, a large number of researchers published a so-called “State-of-the-art review” concerning SMR [11]. The study’s conclusion is that the SMR technology will very likely bring down the price of nuclear power and create far better investment opportunities for investors.

The most mature SMR on the market is from NuScale, whose 12 module 684MWe plant is expected to cost approximately $3 billion ($4385/kW) [12]. Another SMR design is GE Hitachi’s BWRX-300, which is a 300MWe scaled-down version of the mature Gen III+ 1520MWe ESBWR [13]. The expected cost point for nth-of-a-kind commercial deployment is expected to be US$2250/kW.

SMR construction time #

Overall, it is significantly easier, faster and cheaper to manage a construction process for an SMR on a factory assembly line rather than a large project out in the countryside.

This enables SMR to be sent out to all parts of the world, especially remote areas that are not connected to a specific energy grid.

SMR can be of great importance when fossil fuels are to be phased out in places where the electricity market does not have room for large reactors.

Status of SMR #

Sometimes it is claimed that SMR is nowhere to be found and it is not known when they will be ready.

Akademik Lomonosov (Russia) #

Akademik Lomonosov is a floating nuclear power plant. It was connected to the grid in 2019 and started commercial operation in May 2020. It has two 35 MW(e) KLT40S SMR units. They generate 35 MW of electrical power and 150 MW of thermal power and can also be used for desalination of seawater [14].

Sources #

1. https://www.iaea.org/newscenter/news/what-are-small-modular-reactors-smrs
2. https://aris.iaea.org/Publications/SMR_Book_2020.pdf
3. First U.S. Small Modular Boiling Water Reactor Under Development | Department of Energy
4. BWRX-300 – Wikipedia
5. Westinghouse Unveiled Its AP-300 SMR (euronuclear.org)
6. Small Modular Reactors | Rolls-Royce
7. Small Modular Reactor – Holtec International
8. Potential (copenhagenatomics.com)
9. https://www.world-nuclear.org/information-library/nuclear-fuel-cycle/nuclear-power-reactors/small-nuclear-power-reactors.aspx
10. https://www.sciencedirect.com/science/article/abs/pii/S0029549315001545?casa_token=5hW9p0QwJIEAAAAA:WGorVdcIarlylsC0nDSFmyo6qHMoVXEOf-2_Zf2NodRT3kUg6g3nxyZDJvEI6a8oLfYfC3aEdBg
11. https://www.mdpi.com/1996-1073/16/7/3224
12. https://www.nuscalepower.com/en/products/VOYGR-SMR-Plants
13. https://nuclear.gepower.com/build-a-plant/products/nuclear-power-plants-overview/bwrx-300
14. Small Reactors, Great Potential | IAEA