Why SMR safety systems are the most contested IP domain in nuclear energy

Small modular reactor safety systems encompass every engineered and inherent provision that prevents, detects, and mitigates abnormal events in reactors typically rated below 300 MWe — and they represent the single most technically intensive and IP-contested domain in SMR development. The field subdivides into four primary technical clusters: passive safety systems, reactor protection systems (RPS), engineered safety features (ESFs), and monitoring, simulation, and probabilistic safety assessment (PSA) tools. Each cluster carries distinct regulatory weight, because safety system architecture is typically the primary constraint on licensing speed, according to literature from 2023 analysed in this dataset.

The central design philosophy running across all retrieved sources is a decisive shift away from active, power-dependent safety systems toward passive, fail-safe architectures that exploit natural physical laws — gravity, natural convection, thermal conduction — to eliminate reliance on external utilities during accident scenarios. This shift is a direct engineering response to the Fukushima station blackout (SBO) event, which exposed the vulnerability of active cooling systems to loss of external power. According to IAEA safety standards and the literature surveyed here, passive systems reduce the probability of core damage events in scenarios where active systems would fail.

The innovation timeline spans 2012 to late 2025, capturing the full arc from foundational concept filings to highly specialised second-generation architectures. Early filings (2012–2016) established conceptual frameworks. The 2016–2021 period accelerated digital instrumentation and control (I&C) development and formalised passive system architectures. The 2022–2025 cluster — the densest and most strategically significant — reflects specialisation for compact, marine, and micro-reactor configurations, with SNERDI (Shanghai Nuclear Engineering Research and Design Institute) dominating this period across multiple distinct sub-domains.

Four application domains emerge as primary deployment targets across the dataset: land-based distributed grid power and energy security; marine and offshore power generation; nuclear-renewable hybrid energy systems (N-R-HES) operating in load-following and hydrogen co-production modes; and developing nation deployments, with literature addressing Indonesia, Saudi Arabia, and sub-Saharan Africa contexts.

Patent geography and assignee concentration: China’s commanding lead

Within the analysed dataset, China (CN jurisdiction) accounts for approximately 28 of the ~35 identified patents — the dominant share by a wide margin, with US and GB/EP jurisdictions accounting for a smaller but strategically significant portion. This concentration is not merely a filing-volume artefact: it reflects genuine R&D depth, with Chinese assignees filing across all four technical clusters and all identified application domains simultaneously.

SNERDI’s filing trajectory spans the broadest range of sub-domains of any single assignee: passive safety systems for compact reactors (2022, 2024, 2025), marine SMR safety systems (2024), built-in diversity reactor protection systems (April and October 2025), integrated reactor safety systems (2023), and heat pipe micro-reactor safety analysis frameworks (2025). This breadth suggests a coordinated R&D programme rather than opportunistic filing.

NuScale Power’s CN-filed patent family — covering its modular protection system (MPS) architecture across filings in 2016, 2019, and 2024 — represents the most complete US-origin SMR-specific RPS architecture in the dataset. The China General Nuclear Power Corporation’s 2020 GB filing for a reactor protection system indicates Chinese assignees are actively protecting IP in Western jurisdictions, a pattern that IP strategists at Western utilities and reactor vendors should monitor via tools like PatSnap’s IP intelligence platform.

Westinghouse Electric’s 2015 CN filing establishing the integrated passive safety system architecture for integral PWRs predates the Chinese filing wave and appears, based on technical content alignment, to have served as a reference architecture. Korean innovation is represented primarily through literature (SMART reactor, KAERI thermal-hydraulic validation) and the Doosan simulation patent, rather than safety system IP filings in this dataset, as also noted by OECD Nuclear Energy Agency analyses of Asian SMR R&D patterns.

Passive safety systems: from 7-day cooling to indefinite heat removal

Passive residual heat removal and core cooling is the most heavily patented cluster in the dataset, driven by post-Fukushima regulatory requirements and SMR-specific design constraints. Passive systems exploit natural convection loops, gravity-fed emergency cooldown tanks, and conduction through containment walls — without relying on electrical power or manual intervention — to maintain core cooling through any accident scenario in which external power is unavailable.

The 2015 Westinghouse filing established the foundational benchmark: a single unified system integrating passive decay heat removal, high-pressure head water injection, and coolant recirculation. SNERDI’s 2022 filing for a compact reactor rated below 300 MWe advanced this architecture, designing for zero reliance on external power inputs and claiming a reduction in core melt probability of one to two orders of magnitude compared to conventional active-dependent designs. The 2024 continuation addressed loss-of-coolant accident (LOCA) and non-LOCA accident sequences, containment overpressure prevention, and post-accident radioactivity confinement within a single integrated passive architecture.

“Passive safety systems for compact SMRs rated below 300 MWe, relying on gravity, natural convection, and thermal conduction, can reduce core melt probability by one to two orders of magnitude compared to conventional active-dependent designs — without external power inputs.”

A 2020 academic study in the dataset demonstrated an indefinite passive heat removal design using an intermediate dry air cooling tower, fundamentally eliminating the stored-water depletion constraint inherent in conventional emergency cooldown tank designs. This advance directly addresses one of the key regulatory concerns with passive systems: the finite duration of stored water inventories. The EU H2020 McSAFER project (2021) provided experimental validation of passive thermal-hydraulic safety behaviour across four SMR designs — CAREM, SMART, F-SMR, and NuScale — using the COSMOS-H, HWAT, and MOTEL test facilities, establishing a multi-design experimental baseline for regulators as noted in proceedings tracked by IAEA.

A 2022 literature study in the dataset linked passive safety features directly to grid resilience outcomes, noting that natural circulation cooling, the ability to avoid shutdown during power quality events, and low vulnerability to external hazards collectively enable SMRs to serve as resilience anchor points in distributed energy networks. This application-level framing reinforces why passive safety IP is commercially significant beyond regulatory compliance: it is a direct enabler of SMR value propositions in grid stability markets, a point also underscored by emerging frameworks from the US Department of Energy on advanced reactor grid integration.

Digital reactor protection systems: redundancy, diversity, and the built-in shift

Reactor protection systems (RPS) execute automatic reactor trip (scram) and engineered safety feature actuation (ESFAS) when monitored parameters exceed safety setpoints. In SMRs, digital RPS architectures must balance three competing requirements: sufficient redundancy to tolerate single hardware and software failures; diversity across channels to prevent common-cause failures; and compact physical footprint compatible with the smaller module layouts of SMRs rated below 300 MWe.

NuScale Power’s CN-filed patent family is the most architecturally documented US-origin RPS in the dataset. Its 2019 filing systematised redundancy through deterministic protocols and voting logic. The 2024 update incorporated symmetric functional architecture across dedicated logic engines, with manual control override maintained via hardwired analog signals — a design choice that preserves a non-digital fallback independent of software state. China General Nuclear Power Corporation’s 2020 GB filing describes an RTS/ESFAS architecture with N redundant protection channels, safety system bus (SB) integration, and a safety automation system (SAS) — and notably was filed in GB jurisdiction, signalling deliberate Western IP protection.

The built-in diversity shift: eliminating the dedicated DAS

The most architecturally significant recent development in this dataset is SNERDI’s April and October 2025 patents proposing to replace the conventional RPS + dedicated diverse actuation system (DAS) configuration with a single RPS incorporating built-in channel diversity. The motivation is explicitly stated in the filings: conventional four-redundant-channel RPS+DAS configurations are too physically large for compact SMR layouts. Additionally, inherently safe SMRs — with high coolant inventory, natural circulation, and passive injection — do not require the same level of redundancy as large PWRs, making the conventional architecture over-engineered for the SMR safety case.

Jiangsu Nuclear Power’s 2025 CN filing on a diversified protection system (DPS) adds a further architectural layer, explicitly framing the DPS as a defense-in-depth Level 4 protection against common-cause failure of both RTS and ESFAS. This clarifies the functional stack for next-generation SMR safety I&C: RTS → ESFAS → DAS (or built-in diversity) → DPS as the fourth level. CNPEC-SED’s 2025 three-channel safety system filing proposes replacing the conventional two-train manifold configuration with three independent channels, eliminating cross-train pipe break vulnerabilities that can compromise both trains simultaneously — a distinct but complementary innovation to the SNERDI built-in diversity approach.

Emerging frontiers: marine SMRs, three-channel architectures, and heat pipe micro-reactors

The 2022–2025 filing cluster reveals four distinct forward vectors beyond the established passive and digital RPS domains, each representing a genuinely new design space rather than incremental iteration on prior art.

Marine and offshore-specific passive safety

SNERDI’s 2024 CN filing for a marine small reactor safety system is the most significant maritime-specific filing in the dataset, explicitly covering offshore drilling platforms, remote islands, and oceangoing vessels. The filing notes that existing land-based large-reactor safety systems are architecturally incompatible with marine SMR requirements — passive operation is critical and external power unavailability is a baseline assumption, not a contingency. This signals that Chinese designers are treating marine deployment as a first-class design basis, not an adaptation. In the dataset, marine-specific passive safety system patents outside China are sparse, representing a potential IP whitespace for US and European developers of floating nuclear plants.

Heat pipe micro-reactor safety instrumentation

SNERDI’s 2025 filing on safety analysis methodology for heat pipe micro-reactors represents a qualitatively different innovation category. Heat pipe micro-reactors have no primary coolant pump; they transfer heat via conduction through high-temperature heat pipes to secondary systems. This fundamentally different thermal-hydraulic pathway — conduction → heat pipe evaporation/condensation → natural convection to heat sink — requires entirely new protection signal identification methodologies, incompatible with conventional PWR-based safety analysis frameworks.

The SNERDI 2025 filing is among the earliest systematic frameworks in the prior art base for this reactor type captured in this dataset. No consensus safety analysis framework for heat pipe micro-reactors exists in regulatory guidance as of the filing dates surveyed. Organisations working on heat pipe reactor programmes — including derivatives of designs with heritage in space reactor programmes, and newer commercial micro-reactor ventures — should develop and protect their safety analysis methodologies before regulatory frameworks crystallise, as standards bodies including IAEA have yet to publish finalised guidance for this reactor class.

N-R-HES and variable load safety challenges

Two 2022–2023 literature sources in the dataset introduce safety system challenges specific to SMRs operating in nuclear-renewable hybrid energy systems (N-R-HES) — where SMRs follow variable load profiles alongside renewable generation assets and may simultaneously produce hydrogen via electrolysis co-production. Frequent power transients in these operating modes create novel safety-relevant operational envelopes not addressed by conventional steady-state safety analysis frameworks. This represents an emerging gap between the patent literature — which addresses steady-state and accident scenarios — and the emerging operational reality of SMRs in integrated energy systems.

Strategic implications for R&D and IP teams

The SMR safety system landscape as revealed in this dataset carries five concrete strategic implications for R&D leaders, IP counsel, and technology strategists in the nuclear sector.

1. Treat SNERDI’s filing trajectory as a leading indicator

SNERDI alone accounts for a multi-year filing cluster spanning passive systems, marine variants, protection system architecture, and micro-reactor safety analysis — the broadest single-assignee scope in the dataset. Western R&D teams should monitor SNERDI’s filing trajectory as a leading indicator of where SMR safety system IP will be concentrated through 2030. The PatSnap platform enables real-time assignee monitoring against this benchmark.

2. The RPS architecture decision is a near-term bifurcation point

Organisations entering detailed design for SMR I&C systems must explicitly choose between the traditional four-channel RPS + separate DAS architecture and the emerging built-in diversity approach. The choice has physical footprint, licensing timeline, and IP implications. The traditional approach has a deeper prior art base and regulatory precedent; the built-in diversity approach offers a compliance path with significantly reduced spatial footprint for compact designs, but regulatory acceptance remains to be established.

3. Passive safety IP is mature but still differentiable

The core passive decay heat removal concept is established (Westinghouse 2015 foundational architecture; McSAFER 2021 thermal-hydraulic validation). Differentiation now lies in three areas: indefinite cooling duration through dry air cooling tower integration; marine environment optimisation with passive-dominant architectures; and multi-accident sequence coverage within a single unified passive architecture. Patent claims in these differentiated areas remain finable for new entrants.

4. Marine SMR safety systems are an open IP space outside China

Marine-specific passive safety system patents are concentrated exclusively in China in this dataset. US and European developers of floating nuclear plants — and their insurers, regulators, and licensing partners — face a landscape in which the prior art base for marine-specific passive safety is Chinese-controlled. Developing and protecting marine-specific safety system IP is a strategic priority for non-Chinese developers entering this application domain, particularly as OECD NEA regulatory working groups begin to develop guidance for floating nuclear plants.

5. Heat pipe micro-reactor safety is pre-paradigmatic — act before frameworks crystallise

No consensus regulatory safety analysis framework for heat pipe micro-reactors exists in the prior art or regulatory guidance captured in this dataset. The SNERDI 2025 filing is among the earliest systematic approaches to protection signal identification for this reactor class. Organisations in this space should develop proprietary safety analysis methodologies and file foundational patents before regulatory frameworks crystallise around a particular analytical approach — a pattern consistent with advice from standards bodies on establishing IP positions in pre-paradigmatic technical fields.