CPC technology class · G21

G21D - Nuclear Power Plant

Nuclear power plant. 744 US utility patents granted 2015–2025, with the leading assignees and year-by-year grant trajectory.

Compiled by PlainPatent · May 15, 2026

744
US patents granted: #4/8
in G21: 8.3%
G21 class share: -6%
5-yr velocity

The verdict

According to USPTO PatentsView, Nuclear Power Plant ranks #493 of 670 CPC technology areas - 744 US patents granted since 2015, with recorded grant volume down 6% over five years.

#493
of 670 CPC technology areas: 744
US patents granted, 2015–2025: Mitsubishi Electric
leading assignee (55): -6%
grant velocity, last 5 yrs

How G21D's grant cadence moved

Between 2020–2024, G21D recorded 318 grants versus 339 in 2015–2019 (-6% equal-window velocity). Across complete years, output peaked in 2019 at 83 grants and bottomed in 2015 at 50 (+66% peak-over-trough). Lead assignee Westinghouse Electric Company LLC holds 6.0% of the class ; the top three share 17.2%.

Leaderboard read

G21D concentration, lead at 6.0%

Westinghouse Electric Company LLC leads this historical grant record at 6.0% of G21D - us corporation assignees hold 57% of class grants (278 of 484). Figures describe granted US utility patents in this CPC subclass, not current investment or legal strength.

Leader's share: 6.0%
Top three share: 17.2%
Lead over #2: 2

Where G21D sits inside G21

Among 8 subclasses in G21 (Nuclear PHYSICS; Nuclear Engineering), G21D ranks #4 and holds 8.3% of the parent class's 8,981 recorded grants. Sibling chips below are the other subclasses in the same parent class, not the nationwide volume/lead-share peers further down.

G21K 3,019 G21C 2,434 G21F 1,599 G21G 629 G21B 372 G21H 179 G21J 5

Rising assignees active in G21D

Company-wide grant multiples (2022–2024 vs 2019–2021) among assignees with ≥5 patents in this subclass. Growth is company-wide; class patent counts are subclass-specific.

#1 Bwxt Advanced Technologies LLC 24x 0 → 24 company-wide · 13 in G21D
#2 King Abdullah City for Atomic & Renewable Energy (K.A. CARE) 15x 1 → 15 company-wide · 5 in G21D
#3 Carbon Free Holdings LLC 6.00x 1 → 6 company-wide · 7 in G21D
#4 Bwxt Nuclear Energy, Inc. 2.67x 3 → 8 company-wide · 10 in G21D
#5 Korea Hydro & Nuclear Power Co., Ltd. 1.82x 22 → 40 company-wide · 26 in G21D

G21D grants by year, peak 2019 (83)

US utility-patent grants per year in G21D, 2015–2025 - recent five years are down 6% versus 2015–2019.

Westinghouse Electric

45
Terrapower

43
Ge-hitachi Nuclear…

40
Nuscale Power

29
Korea Atomic Energy…

27
Korea Hydro & Nuclear…

26
Framatome

19
Bwxt mpower

17
Smr Inventec

17
Bwxt Advanced

13
Doosan Heavy…

10
Hitachi-ge Nuclear…

10

What this shows Mitsubishi Electric is the most active filer in G21D, holding 55 of the 744 patents in this class. Concentration at the top signals how contestable this technology area is for new entrants.

View data table

Top patent holders in CPC subclass G21D
Rank	Company	Patents in G21D
#1	Westinghouse Electric Company LLC	45
#2	Terrapower, LLC	43
#3	GE-Hitachi Nuclear Energy Americas LLC	40
#4	Nuscale Power, LLC	29
#5	Korea Atomic Energy Research Institute	27
#6	Korea Hydro & Nuclear Power Co., Ltd.	26
#7	Framatome	19
#8	Bwxt mPower, Inc.	17
#9	SMR Inventec, LLC	17
#10	Bwxt Advanced Technologies LLC	13
#11	Doosan Heavy Industries & Construction Co., Ltd.	10
#12	Hitachi-ge Nuclear Energy, Ltd.	10
#13	Areva NP	10
#14	Areva GMBH	10
#15	Bwxt Nuclear Energy, Inc.	10
#16	DCNS	8
#17	Nugen, LLC	8
#18	Liqid Inc.	7
#19	Kepco Engineering & Construction Company Inc.	7
#20	Atomic Energy OF Canada Limited	7

Footprint here vs. claim strategy

Each dot is a leading G21D assignee, placed by how many patents it holds in this class (horizontal) against its company-wide average claims per patent (vertical) - a read on whether the class is led by broad-but-shallow filers or focused deep-claim players.

Top 14 G21D assignees by class footprint. Bubble size = patents in G21D. Source: USPTO PatentsView (claim depth is company-wide across all classes).

Classes near G21D's 744-grant footprint

Nationwide nearest neighbors for G21D (#493 of 670 by volume ; lead share 7.4%) - not the G21 parent-class siblings above.

Nearest by grant volume

B31D 747 B27N 750 B62H 738 C01C 735

Nearest by lead-assignee share

D21H 7.4% B21J 7.4% F16C 7.4% B60J 7.4%

Questions about G21D

Which company holds the most patents in G21D?

Mitsubishi Electric Corporation leads G21D with 55 patents (6.0% of the subclass). By PatentsView assignee type, us corporations account for 57% of class grants.

Which G21D assignees grew fastest recently?

Among assignees with ≥5 grants in G21D, Bwxt Advanced Technologies LLC shows the highest company-wide grant multiple (24x: 0 grants in 2019–2021 → 24 in 2022–2024) while holding 13 patents in this subclass. Growth is company-wide, not class-only.

How does G21D compare inside parent class G21?

Inside G21 (Nuclear PHYSICS; Nuclear Engineering), G21D ranks #4 of 8 subclasses by grant volume and holds 8.3% of the parent class total. The largest sibling is G21K (3,019 grants).

What to do with this data

G21D in context - here's where to go next.

Westinghouse Electric Company LLC leads G21D with 45 grants in this class. See full portfolio
G21D ranks #493 of 670 by grant volume among all tracked CPC technology areas. See the ranking
Inside parent class G21, the largest sibling subclass is G21K with 3,019 grants. Explore G21K

Figures reflect USPTO PatentsView grant data through 2026-05-15; pending applications not yet granted are not counted.

Methodology - G21D figures are USPTO PatentsView granted-utility totals for this subclass (744 grants in the tracked window).

Every figure on PlainPatent is rendered directly from USPTO source data, no number is typed in by an editor. This page draws directly on USPTO source data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.