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Advantages and Disadvantages of Small Modular Reactors

Small modular reactors are very specific. Their size and modularity offer many advantages. On the other hand, they have some disadvantages, which must be considered during decision-making.

Possible Advantages

Enhanced safety and security

Lower thermal power of the reactor core, compact architecture, and employment of passive concepts have the potential for enhanced safety and security compared to earlier designs and large commercial reactors. The passive safety systems are a very important safety feature in the SMR. Therefore, there is less reliance on active safety systems and additional pumps and AC power for accident mitigation. These passive safety systems can dissipate heat even after the loss of offsite power. The safety system incorporates an on-site water inventory that operates on natural forces (e.g., natural circulation). In reactor engineering, natural circulation is a very desired phenomenon since it can provide reactor core cooling without coolant pumps so that no moving parts could break down.


As was written, the term “modular” in SMRs refers to its scalability and the ability to fabricate major components of the nuclear steam supply system (NSSS) in a factory environment and then transport them to the site. This can help limit the on-site preparation and also reduce the construction time. This is very important since the lengthy construction times are one of the key problems of the larger units. Moreover, the in-factory fabrication and completion of major parts of the nuclear steam supply system can also facilitate the implementation of higher quality standards (e.g., inspections of welds).

Construction time and financing

Size, construction efficiency, and passive safety systems (requiring less redundancy) can reduce a nuclear plant owner’s capital investment due to the lower plant capital cost. In-factory fabrication of major components of a nuclear steam supply system can significantly reduce the on-site preparation and also reduce the construction time. This, in turn, can lead to easier financing than larger plants.

Possible Disadvantages

Large-scale Production

Most economic benefits (especially lower capital cost) stated are valid for n-th unit produced. Large-scale production of SMRs and initial orders for tens of units is required to achieve these economic benefits.


One of the very important barriers is licensing of new reactor designs. For example, in regulating the design, siting, construction, and operation of new commercial nuclear power facilities, the NRC currently employs a combination of regulatory requirements, licensing, and oversight. Historically, the licensing process was developed for large commercial reactors. The licensing process for new reactor designs is a lengthy and costly process.

Reactor Physics and Thermal Hydraulics:
  1. J. R. Lamarsh, Introduction to Nuclear Reactor Theory, 2nd ed., Addison-Wesley, Reading, MA (1983).
  2. J. R. Lamarsh, A. J. Baratta, Introduction to Nuclear Engineering, 3d ed., Prentice-Hall, 2001, ISBN: 0-201-82498-1.
  3. W. M. Stacey, Nuclear Reactor Physics, John Wiley & Sons, 2001, ISBN: 0- 471-39127-1.
  4. Glasstone, Sesonske. Nuclear Reactor Engineering: Reactor Systems Engineering, Springer; 4th edition, 1994, ISBN: 978-0412985317
  5. Todreas Neil E., Kazimi Mujid S. Nuclear Systems Volume I: Thermal Hydraulic Fundamentals, Second Edition. CRC Press; 2 edition, 2012, ISBN: 978-0415802871
  6. Zohuri B., McDaniel P. Thermodynamics in Nuclear Power Plant Systems. Springer; 2015, ISBN: 978-3-319-13419-2
  7. Moran Michal J., Shapiro Howard N. Fundamentals of Engineering Thermodynamics, Fifth Edition, John Wiley & Sons, 2006, ISBN: 978-0-470-03037-0
  8. Kleinstreuer C. Modern Fluid Dynamics. Springer, 2010, ISBN 978-1-4020-8670-0.
  9. U.S. Department of Energy, THERMODYNAMICS, HEAT TRANSFER, AND FLUID FLOW. DOE Fundamentals Handbook, Volume 1, 2 and 3. June 1992.

See above:

Type of Reactors