289 companies in our data use OpenMC, and 94 of them name it in job posts they wrote. From October 2025 to August 2026, 101 job posts named it. Nuclear Engineer is the role that names it most often.
Which companies name OpenMC in the most job posts?
Radiant, Commonwealth Fusion Systems and Oak Ridge National Laboratory are among the companies with the most job posts naming OpenMC. Radiant is the newest of the five companies in the table, with its first job post naming it in March 2025.
CompanyPostsPeopleRecent job post
Radiantfirst seen Mar 2025272
"Professional experience developing and applying MCNP, OpenMC, or comparable neutron and radiation transport models."Staff Nuclear Engineer, Oct 21, 2026
Commonwealth Fusion SystemsUtilities · first seen Sep 2022171
"Experienced in MCNP or OpenMC"Intern - Nuclear/Systems Engineer - Summer 2027, Oct 24, 2026
Oak Ridge National LaboratoryPublic Administration · first seen Mar 2023170
"…and analyze reactor models using world-class modeling and simulation codes (SCALE, VERA, OpenMC, MCNP, Serpent, MOOSE) to support the design and development of next generation nuclear reactors."Advanced Nuclear Reactor and Fuel Cycle Engineer (Associate), Oct 27, 2026
CEAUtilities · first seen Sep 2023158
"…flux et les taux de réaction seront comparés à ceux d’autres codes Monte Carlo, tels qu’OpenMC (développé principalement au MIT et au Laboratoire national d’Argonne, aux États-Unis) et MVP développé à…"verification and validation of photon transport for the Monte Carlo Tripoli-5 code (H/F), Oct 21, 2026
Analytical Mechanics AssociatesProfessional Services · first seen May 2023153
"Experience performing reactor and radiation physics calculations in MCNP, Serpent, OpenMC, Geant4, SCALE, DAGMC, or equivalent."Space Nuclear Systems Engineer, Oct 28, 2026
0.07 in every 10,000 job posts named OpenMC from June to August 2026, against 0.05 from March to May. One company accounts for most of that change.
Show the data
Month
Job posts naming OpenMC
All job posts
Per 10,000
Oct 2025
4
1,413,673
0.03
Nov 2025
12
1,822,119
0.07
Dec 2025
2
1,236,103
0.02
Jan 2026
7
1,828,002
0.04
Feb 2026
10
1,856,647
0.05
Mar 2026
11
1,850,711
0.06
Apr 2026
11
1,728,886
0.06
May 2026
6
1,821,509
0.03
Jun 2026
8
1,909,496
0.04
Jul 2026
11
1,815,180
0.06
Aug 2026
19
1,835,698
0.10
How many companies named OpenMC in a job post for the first time in recent months?
From June to August 2026, 9 companies posted their first job naming OpenMC; 5 did from March to May. From October 2025 to August 2026, 21 companies named it in a job post for the first time.
March to May 20265
June to August 20269
October 2025 to August 202621
Companies whose first job post naming it appeared in that period. Recruiters, staffing firms and job boards are left out.
How do we know which companies use OpenMC?
94 companies name OpenMC in their own job posts. The other 195 show up because employees list it on their profiles. 36 show up in both job posts and employees' profiles.
How we knowCompaniesShare
Job posts name OpenMC
9433%
Employees' profiles list OpenMC
19567%
289 companies. Each is counted once, under the strongest evidence we have for it.
What size are the companies that use OpenMC?
OpenMC leans toward large companies. 22% of its users are companies with 1,000 to 5,000 employees, against 17% on the typical tech page. 83 of its companies have more than 5,000 employees.
Share of its companies
Typical tech page
ShareTypical
Under 50 employees
17%22%
50 to 999
32%38%
1,000 to 5,000
22%17%
Over 5,000
29%23%
Where are OpenMC companies based?
Italy is 2.2 times as common among OpenMC companies as on the typical tech page, at 3.2%. The United States leads overall with 48%. France is second, at 9.4%.
ShareTypical
United States
48%43%
France
9.4%4.6%
United Kingdom
9%6.4%
Italy
3.2%1.5%
Germany
2.9%4.4%
Canada
2.2%3.6%
Companies in 40 countries and territories. Shares are of companies with a known headquarters country.
Show the data
Country
Companies
Share
Typical tech page
United States
133
48%
43%
France
26
9.4%
4.6%
United Kingdom
25
9%
6.4%
Italy
9
3.2%
1.5%
Germany
8
2.9%
4.4%
Canada
6
2.2%
3.6%
Which teams work with OpenMC?
OpenMC sits mostly with nuclear engineering teams (5 companies).
TeamCompanies
Nuclear engineering
5
Draco
2
Edf R&D uk
2
Laboratoire de neutronique
2
Neutronics
2
Nuclear services
2
Which companies started naming OpenMC in job posts recently?
8 companies with 50 or more employees picked up OpenMC in their job posts from April to August 2026. Xcimer Energy has the most job posts of the new commercial companies, 4 from April to August.
Companies that named OpenMC in a job post for the first time between April and August 2026, ranked by their job posts in those months. AI-native companies get a group of their own, whatever their size. Recruiters and job boards are left out.
Which roles mention OpenMC most?
Nuclear Engineer roles make up 53% of the job posts that name OpenMC. Nuclear Engineer posts naming it numbered 11 from March to May 2026 and 22 from June to August.
RoleSharePosts
Nuclear Engineer
53%54
Researcher
9.9%10
Hardware Engineer
3%3
Analyst
2%2
Industrial Engineer
2%2
Laboratory Services
2%2
Show the data
Role
Share
Oct 2025 to Aug 2026
Mar to May 2026
Jun to Aug 2026
Nuclear Engineer
53%
54
11
22
Researcher
9.9%
10
0
7
Hardware Engineer
3%
3
2
1
Analyst
2%
2
1
1
Industrial Engineer
2%
2
0
0
Laboratory Services
2%
2
1
1
About this data
Sumble built this page. Sumble gives sales, marketing and other GTM teams technographics and hiring signals for the companies they sell to: the technologies each company uses, which teams are hiring and for what, and who reports to whom. That helps a team know who to contact, why now, and what to say.
Sumble covers more than 3.6 million companies, 93 million job posts collected since 2022 and 194 million employee profiles, and tracks more than 37,000 technologies. It finds which technologies a company uses by reading its job posts and its employees' public profiles.
Sumble has a free plan, and the same data is available through its API and MCP server.
A company counts when its own job posts or its employees' public profiles name the technology. Hiring is that technology's share of all job posts collected each month. Quotes are copied word for word from the companies' job posts.
Every figure on this page comes from Sumble's own analysis, and you won't find it outside Sumble.
