SMRs and Microreactors: Benefits, Limitations, and the Case for Large Nuclear Plants in Taiwan

What are SMRs and MMRs?

SMR stands for small modular reactor. The IAEA generally describes the category as reactors with electrical output of up to 300 MWe per module. MMR stands for micro modular reactor and is used here as a general term for very small modular reactors. Naming and capacity boundaries vary across organizations and suppliers; IAEA descriptions generally place microreactors below 10 MWe. [1]

MWe measures electrical power; MWth measures thermal power. They are not equivalent electricity-supply capacities. A plant may also contain several SMR modules, so a “small” reactor does not necessarily mean a small total site capacity.

SMR classifies size and construction approach, not a particular coolant. Some designs build on light-water technology; others use high-temperature gas, liquid metals, or molten salts. The labels SMR and MMR alone do not establish fuel, temperature, safety characteristics, or maturity. [2]

Real applications exist, but maturity varies considerably by design

SMRs have moved beyond the concept stage. Russia's Akademik Lomonosov floating nuclear plant entered commercial operation in 2020, and China's Shidaowan HTR-PM high-temperature gas-cooled demonstration project entered commercial service in December 2023. [1][3]

Those examples do not establish mature serial production for every SMR, and one design's operating record cannot be transferred to another design still awaiting validation.

Microreactors also have concrete research and testing progress. In April 2026, the US Department of Energy announced completion of the DOME microreactor test facility, whose functions include collecting performance data for future commercial licensing. Completing a test facility, starting a reactor for the first time, and providing long-term commercial power are different milestones. [4]

For an electricity buyer, the relevant question is whether the specific design being considered has verifiable construction, operating, and maintenance experience.

What advantages can smaller units offer over large reactors?

First, a smaller initial investment and flexibility to add capacity in phases. Where demand grows gradually, an owner can begin with fewer modules and expand later, reducing pressure to commit large amounts of capital at once. The IEA also identifies the potential for smaller project investment, while noting that financing-risk improvements still depend on successful first projects and technical validation. [5]

Second, potential benefits from factory manufacturing and repeated construction. Moving some site work into factories may improve manufacturing conditions and quality consistency. Repeated production of the same design can accumulate construction experience and spread development costs. Enough orders, a stable design, and a qualified supply chain are needed to realize those benefits. [2]

Third, finer increments of capacity. As an illustration, four 300 MW units can be added in stages to reach 1,200 MW and maintained at different times. If modules can operate independently, losing one removes less capacity. Shared systems or a common external event can still affect several modules, however; modularity does not mean complete independence. [6]

Fourth, serving smaller or specialized energy requirements. Some designs can provide industrial heat. Microreactors target microgrids, remote facilities, and locations where transporting diesel is expensive. These applications must be assessed against local energy conditions, rather than only the price per kilowatt-hour on a large grid. [4]

Low-carbon, sustained electricity supply is a general nuclear characteristic, not unique to SMRs. Passive safety features also need design-specific assessment; reactor size alone does not establish a safety ranking.

Lower initial spending does not guarantee cheaper electricity

Cost discussions should distinguish at least three questions:

Large reactors spread costs through economies of scale. SMRs aim to offset the scale economies lost through smaller size with simplification, standardization, and serial production. That is part of the business model that remains to be demonstrated. [2]

Smaller reactors do not eliminate spent-fuel and other radioactive-waste management. Some new fuels may require changes to storage, transport, or back-end arrangements. Smaller size alone does not establish a lower waste burden per kilowatt-hour. [2]

A more accurate conclusion is that SMRs may lower the threshold for an individual capital commitment, but do not guarantee an inexpensive first project or a lower total cost for the same electricity output.

Compare the full timeline from project initiation to commercial operation

Faster site construction is another commonly cited SMR advantage. Electricity systems need units that actually supply power, however. Complete delivery also includes final design, safety demonstration, site preparation, equipment and fuel delivery, and commissioning.

For a first-of-a-kind design, work easily omitted from construction-time claims includes:

- Experiments and analyses for new safety systems, followed by validation of integrated performance. - Design changes and renewed analysis arising from licensing-review requests. - Factory capability, supplier quality, and long-lead equipment preparation. - Fuel supply, operator training, and commissioning.

The IAEA SMR Regulators' Forum distinguishes the demonstrations needed for first and subsequent units and identifies passive-safety performance, shared systems between modules, and manufacturing oversight among the issues. [6]

Some work can proceed in parallel. The overall duration depends on the last necessary activity that blocks subsequent progress. If additional early-stage work exceeds the time saved in construction, an SMR can enter commercial service later than a mature large-reactor design. Requiring more safety evidence is not itself proof of lower safety.

The burden varies by design. GE Vernova Hitachi says BWRX-300 uses commercially available GNF2 fuel, avoiding development of a new fuel product. Its complete configuration and safety performance still require validation. [7]

Canada's Darlington project illustrates the difference in time boundaries. OPG selected BWRX-300 in late 2021 and currently targets grid connection by the end of 2030—approximately nine years later. A grid-connection target is also not completed commercial operation. The interval includes engineering, procurement, site work, and owner decisions, and cannot all be attributed to regulatory review. [8]

An ideal construction period after serial production matures should not be treated as the complete delivery timeline for today's first project.

Why this article still favors proven large nuclear technology for Taiwan

The assessment here is limited to selecting new nuclear generation for large-scale electricity supply in Taiwan. Lifetime extensions or restarts of existing units involve different equipment, licensing, and cost conditions and require separate comparison.

First, Taiwan needs large amounts of continuous industrial and household electricity. If additional demand can absorb a large unit's output over the long term, economies of scale deserve early consideration. Microreactors' remote-energy role differs from the main island's large-scale requirements, although multiple SMR modules can also serve larger loads.

Second, the conditions of a state-owned utility mean the initial investment threshold need not be the only constraint. Taipower is an integrated state-owned utility. The IEA notes that state-owned enterprises can often access financing closer to sovereign terms. [9][5] One inference is that, if the government supports long-term construction, SMRs' smaller upfront commitments may be less decisive than for private developers. State ownership still does not remove interest costs, overruns, or pressure on public finances.

Third, power planning needs predictable delivery. A large-reactor design with commercial operating experience, a stable design, and an active supply chain may offer a more estimable schedule than an SMR awaiting its first demonstration. This is conditional: the IEA also documents severe delays and overruns in some large nuclear projects in advanced economies. Large size is not a guarantee of punctual delivery. [5]

Taiwan's island geography and warm, humid climate do not automatically determine the appropriate reactor size. Every option must address sites, earthquakes and coastal hazards, cooling, and transmission access. A large unit's sudden outage creates a larger supply gap, while smaller SMR units may spread the effect of losing one unit. Both require complete grid and backup assessments. Site and external-event safety requirements do not disappear with smaller size. [6]

This article therefore favors proven large nuclear technology as the initial comparison baseline for new nuclear capacity in Taiwan. That depends on feasible sites, designs, supply chains, and financing—not simply the word “large.” Nor can a firm conclusion be reached by applying foreign prices and schedules directly to Taiwan.

What could make SMRs more attractive in the future?

Today's first-of-a-kind risks do not necessarily describe future serial-production performance. If a specific SMR accumulates several operating units, avoids frequent design changes, and gains reliable factories, fuel, and qualified suppliers, later projects may reduce repeated development and licensing work.

Taiwan can track four things:

1. Whether the first units enter commercial operation on schedule and operate reliably. 2. Whether actual schedules and costs improve for subsequent units of the same design. 3. How much foreign validation and review experience can be used under Taiwanese site conditions. 4. Whether complete investment, operations, grid, and waste costs are competitive for the same supply requirement.

At that point, SMRs could provide initial electricity sooner and make expansion easier. The first 300 MW module entering service and completion of a 1,200 MW project are different delivery outcomes and should still be compared separately.

Taiwan can evaluate mature technologies for sustained, large-scale supply while tracking actual SMR deployment results. As technology, supply chains, and regulatory experience mature, shorter SMR construction times have a better chance of becoming earlier commercial operation for the complete project.