Small Modular Reactor Patents: Leaders, Trends & White Space 2026
Filing growth compares 2021 (38 records) with 2024 (13) — a three-year span. 2024 is the most recent year we treat as complete: publication lags filing by roughly 18 months, so 2025 onwards are still filling in and any growth rate that ends there would understate the field. Top-5 share is the combined record count of the five largest assignees divided by all 542 records in scope (CR5), not by the ranked leaders only.
What the modular reactor vessel filing record shows
Modular reactor vessel design sits at the structural centre of small modular reactor (SMR) engineering: how the core, containment, and integral steam or heat-transfer components are packaged into a single transportable unit. The 542 records in scope span filings from 2015 through mid-2026, concentrated almost entirely under G21C (nuclear reactors), with secondary claims reaching into plant-level systems, radiation shielding, and heat exchange. Publication lags filing by roughly 18 months, so the most recent years in any trend chart understate real activity.
Filing volume rose through the mid-2010s, peaked in 2021, and has since declined through the last complete year of data. Assignee concentration is moderate rather than extreme: a single leader holds a meaningfully larger share than the rest of the field, but the ranked group of 100 companies still shows plenty of room for new entrants below the top tier.
Filing trend and technology composition
Two views of the same 542-record dataset: how filing volume has moved year over year, and how records distribute across IPC subclasses relevant to modular reactor vessel design.
A filing peak in 2021, then a pull-back
Annual filings rose from 8 in 2017 to a peak of 38 in 2021, then fell to 13 by 2024 — a 66% drop over that three-year span. Because 2025 and 2026 are still filling in as publications catch up, this should be read as a slowdown from an unusually active filing wave rather than a verdict on where SMR vessel innovation is heading next.
Vessel claims dominate; supporting systems are thinner
99.6% of the 542 records carry a G21C nuclear-reactor classification, confirming the search is well-targeted. Beyond that core, 16.4% also touch G21D nuclear power plant claims, 5.4% touch G21F radiation shielding, and smaller shares extend into heat exchange (F28D, F28F), control systems (G05B), steam generation (F22B) and signalling (G08B) — the branches most likely to hold under-claimed combinations.
Shares are the percentage of the 542 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Small Modular Reactors: Modular Reactor Vessel Patent Landscape with Eureka
This page is one run against one query. Ask Eureka your own question about small modular reactors: modular reactor vessel patent landscape and every answer comes back with the patent numbers behind it.
Try EurekaThe most-cited records anchoring this field
Containment pressure suppression system for liquid metal cooled reactors (US5706320A)
A pressure suppressing and aerosol scrubbing system configured to be located between low pressure upper containments associated with modular reactor vessels. The design uses a water tank with connected, partially filled chambers and a vertical baffle with horizontal vent holes, each chamber linked by a vent/relief line to a respective upper containment, isolating containments from each other under normal operating conditions.Filed by General Electric Company, published 1998-01-06.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US4508677A | Modular nuclear reactor for a land-based power plant and method for the fabrication, installation and operati… | 129 |
| 2 | US5513226A | Destruction of plutonium | 115 |
| 3 | US4096032A | Modular in-core flow filter for a nuclear reactor | 75 |
| 4 | US20150243376A1 | Molten salt fission reactor | 67 |
| 5 | US4678623A | Modular head assembly and method of retrofitting existing nuclear reactor facilities | 65 |
| 6 | US3957575A | Mechanical design of a light water breeder reactor | 64 |
| 7 | US20160203883A1 | Semi Submersible Nuclear Power Plant and Multi-Purpose Platform | 60 |
| 8 | US4678626A | Radiant vessel auxiliary cooling system | 60 |
| 9 | US20130336441A1 | Small modular reactor safety systems | 58 |
| 10 | CN108648837A | 一种全自然循环的模块式小型反应堆 | 55 |
Citation counts reflect influence within the searched corpus and skew toward older filings; they are not a measure of current commercial relevance.
Patent titles are shown in the language they were filed in, not translated, so that each record stays verifiable against the original filing — a translated title will not match in Eureka or in any national register. Each row carries its publication number; clicking a row searches Eureka by that number.
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Browse MCP servers →What the numbers mean for a filing or licensing decision
Four data points from this dataset that change how a search, freedom-to-operate review, or partnership scan should be scoped.
The top of the field is concentrated, not locked up
Five assignees together account for 165 of the 542 records in scope. That is a real concentration, but it leaves nearly 70% of filings spread across a ranked field of 100 companies, meaning freedom-to-operate work cannot stop at the largest holders.
The 2021 peak has not been sustained through the last complete year
Annual filings fell from 38 in 2021 to 13 in 2024. Because 2025-2026 data is still incomplete under normal publication lag, this reads as a cooling from a filing wave rather than confirmation that interest in vessel design itself is fading.
Plant-level integration claims are the largest adjacent branch
Beyond the core G21C classification held by 99.6% of records, the next-largest overlap is G21D nuclear power plant claims, followed by radiation shielding (G21F) and heat exchange (F28D/F28F). These smaller branches are where vessel-adjacent combination claims are least crowded.
Filing activity is US-led but genuinely multi-jurisdictional
The United States leads with 142 records, followed by European (EPO), PCT, South Korean, Chinese, and UK filings in a fairly even spread. A vessel design cleared against US prior art alone will still face separate exposure in Europe and South Korea.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to small modular reactors: modular reactor vessel patent landscape, with the prior art for and against each one.
Where to take this analysis
This landscape identifies where claim density sits and where it thins out. Turning that into a filing or licensing decision means going deeper on specific branches or specific holders.
Map the under-claimed branches
G05B control systems and F28F heat-exchanger details carry the smallest shares of the 542 records. A targeted claim-chart review of these branches can surface whether a first-mover position is still open.
Explore white space in EurekaTrack the leading assignees' recent activity
With 30.4% of records held by five assignees, monitoring their post-2021 filings specifically shows whether the leaders are still active or have shifted focus elsewhere.
Build an assignee watchlist in EurekaRun a freedom-to-operate check against the most-cited records
The five most-cited records anchor prior art across containment, filtration and retrofit claims. Any new vessel design should be checked against these specifically before broader searching.
Start an FTO search in EurekaCommon questions about modular reactor vessel patents
One assignee leads the field with 61 of the 542 records in scope, a clear margin over the rest of the ranked group. The next four assignees combined bring the top-five share to 165 records, or 30.4% of all filings. Below that, the ranking of 100 companies shows a long tail of firms with only a handful of filings each, so leadership at the top does not mean the field is closed to new entrants.
Filing activity rose through the late 2010s, peaked at 38 records in 2021, and had fallen to 13 by 2024, a 66% decline over that span. Because patent publication typically lags filing by around 18 months, the 2025 and 2026 figures in any dataset are still incomplete and should not be read as confirmation of a continued drop. The honest read is that the 2021 filing wave has cooled, not that vessel innovation has stopped.
Virtually all records, 99.6% of the 542 in scope, carry a core G21C nuclear-reactor classification, which confirms the dataset is well-targeted. The largest secondary overlap is G21D nuclear power plant claims at 16.4%, followed by radiation shielding under G21F at 5.4%. Heat exchange, control systems, steam generation and signalling each account for smaller single-digit shares, marking them as the thinner, more open branches around the core vessel claims.
The United States receiving office leads with 142 records, followed by the European Patent Office at 94 and WIPO's PCT route at 55. South Korea, China and the United Kingdom follow with 44, 39 and 35 records respectively. This spread means a design cleared against US prior art can still face separate exposure in Europe or South Korea, so multi-jurisdiction searching matters for any SMR vessel programme with international ambitions.
US5706320A, filed by General Electric, describes a containment pressure suppression and aerosol scrubbing system positioned between low-pressure upper containments associated with modular reactor vessels in liquid metal cooled reactors. Its core mechanism is a water tank with connected, partially filled chambers and a vertical baffle, each chamber linked by a vent or relief line to a respective containment so the containments stay isolated under normal operating conditions. Anyone designing a similar inter-containment pressure relief or scrubbing approach for a modular liquid-metal design should review this claim scope directly rather than relying on general prior-art searching.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.