Rejobs
Commonwealth Fusion Systems

Senior Multiphysics Modeler

Join Commonwealth Fusion Systems as a Senior Multiphysics Modeler in Devens, Massachusetts. You'll develop fuel cycle models for the world's first fusion power plant, collaborating with experts to ensure feasibility and innovation. Enjoy competitive compensation, flexible vacation days, and professional growth opportunities.
Commonwealth Fusion Systems
Commonwealth Fusion Systems
Devens, Massachusetts, United States   Hybrid   Full Time   USD 110k–185k yearly  UTC-05:00

Commonwealth Fusion Systems

Company Overview

Commonwealth Fusion Systems (CFS)

Cambridge, MA, United States

2018

Approximately 430 employees (source: zoominfo.com). Revenue figures vary, with reports indicating $211.3 million or $31.7 million, though as a pre-revenue fusion developer focused on R&D, these may reflect funding or operations rather than sales.

What They Do

Commonwealth Fusion Systems (CFS) is a pioneering private fusion energy company that specializes in tokamak-based magnetic confinement fusion. Founded as a spinout from MIT's Plasma Science and Fusion Center, CFS focuses on utilizing high-temperature superconducting magnets to achieve commercial net energy production (source: cfs.energy). The company has made significant strides in its technology, particularly with the development of compact fusion machines that leverage decades of tokamak science. Their flagship projects, SPARC and ARC, aim to demonstrate net energy gain and commercial viability in the coming years (source: cfs.energy).

Projects & Track Record

CFS is currently engaged in several groundbreaking projects, most notably the construction of SPARC, which is set to be the world's first net-energy fusion machine. Located at their Fusion Energy Campus in Devens, Massachusetts, SPARC aims to demonstrate net energy gain by the late 2020s (source: cfs.energy). Additionally, CFS is planning the ARC project, a 400 MW-class grid-scale tokamak power plant designed for commercial deployment in the early 2030s. These projects are underpinned by significant technological advancements, including the successful testing of the central solenoid magnet module (CSMC) in November 2024, which confirmed the manufacturability of critical components for SPARC (source: zoominfo.com).

Recent Developments

In the past two years, CFS has made remarkable progress, including the opening of its Devens Fusion Energy Campus on February 10, 2023, which was attended by notable figures such as U.S. Secretary of Energy Jennifer Granholm (source: cfs.energy). The company has also secured substantial funding, raising $863 million in August 2024, building on a previous $1.8 billion round in May 2023, bringing total funding to over $2 billion (source: wbjournal.com). Furthermore, CFS announced its first commercial power plant site in Chesterfield County, Virginia, which will be independently financed and operated, with plans for grid connection in the early 2030s (source: zoominfo.com).

Working There

CFS offers a range of roles across various disciplines, including fusion science, engineering, manufacturing, and materials science. The majority of their workforce is based at the Devens campus, which has grown to over 430 employees (source: cfs.energy). The company culture emphasizes rapid execution and transparency, attracting top talent from the fusion and manufacturing sectors. Key executives include Co-Founder and CEO Bob Mumgaard, along with other leaders in operations and science, indicating a strong demand for expertise in tough tech and physics (source: nasdaqprivatemarket.com). While specific benefits are not detailed, the scale-up and investor backing suggest competitive packages for high-caliber roles in a mission-driven environment (source: cfs.energy). Job seekers are encouraged to monitor their careers page for openings related to SPARC and ARC advancements.

Contact


Last updated on 2026-01-02 | Report an issue

Job Description

Commonwealth Fusion Systems is on a mission to deliver the urgent transition to fusion energy.

Combining decades of research, top talent, and new technologies, we're designing and building commercially viable fusion power plants. And working with policymakers and suppliers to build the energy industry of the future.

We're in the best position to make it happen. Since 2018, we've raised nearly $3 billion in capital, making us the largest and leading private fusion company in the world.

Now we're looking for more thinkers, doers, builders, and makers to join us. People who'll bring new perspectives, solve tough problems, and thrive as part of a team.

If that's you and this role fits, we want to hear from you.

Join the power movement as a Senior Multiphysics Modeler

The Senior Multiphysics Modeler will work closely with the CFS tritium program and process engineering team to develop a fuel cycle model for the world's first fusion power plant, ARC, located in Chesterfield County, Virginia.

The senior multiphysics modeler will develop simulation toolkits and workflows that integrate first-principles multiphysics simulations with industrial process models to support technology development and subsystem integration for key fuel cycle systems, supported by the CFS fuel team to understand system requirements.

The ideal candidate is an expert in heat and mass transport modeling, with an appreciation for simplicity and drive to build. This individual knows the power of optimizing devices by tuning material parameters, and appreciates a simple non-dimensional analysis and rigorous integrated simulations as the problem space requires. The candidate enjoys teaching and building tools that others can use independently.

Applicants must have a degree in a relevant engineering or science discipline as well as experience in process modeling and programming. Applicants must have a demonstrated ability to apply a first principles approach in solving complex engineering problems and experience conducting cost-benefit to evaluate the economics of proposed solutions. Applicants must have demonstrated success working on engineering projects in multi-disciplinary teams generating effective solutions to complex problems.

What you'll do

  • Lead the development of an integrated power plant fuel cycle model
  • Develop models for unit operations and incorporate multi-effects in components
  • Develop simulation tools to enable targeted R&D for key fuel cycle technologies
  • Own the fuel cycle simulation tools and models
  • Validate models and identify key R&D requirements to enable validation where there are currently gaps in the literature
  • Collaborate cross-functionally with both internal and external experts to ensure fuel cycle models are feasible, economic and state-of-the-art
  • Develop processes and layouts for fueling subsystem blocks that are communicated through standard engineering documents
  • Generate detailed work plans and define milestones, integrated with R&D, to deliver validated models
  • Provide guidance to colleagues for use of developed modeling tools and outputs
  • Identify emerging trends and opportunities and influence CFSs's fuel cycle modeling strategy

What we're looking for

  • Master's degree or similar experience with 7+ years in chemical engineering, mechanical engineering, physics, materials science, physical chemistry or similar
  • 5+ years experience modeling process systems
  • 5+ years experience in computer programming
  • Knowledge of transport phenomena and chemical processes in gasses
  • Experience building integrated process models
  • Process engineering and systems integration
  • Experience managing large data sets
  • Understanding of scalable simulations
  • Track record in version control
  • Data reduction and results analysis

Bonus points for

  • Experience with Python and/or Matlab
  • Experience with multiphysics tools such as Comsol
  • Exposure to process simulators like HYSYS
  • Use of engineering management tools
  • Confluence/JIRA and remote collaboration tools
  • Fusion energy experience
  • Chemical engineering
  • Atom and molecular mass transport

Must-have requirements

  • Ability to occasionally lift up to 50 lbs
  • Perform activities such as sitting, typing, standing, stooping, or climbing for extended periods of time
  • Dedication to safety to mitigate industrial hazards that may include heat, cold, noise, fumes, strong magnets, lead (Pb), high voltage, and cryogenics
  • Willingness to travel or work required nights/weekends/on-call occasionally

$110,000 - $185,000 a year

Salary range for this full-time position + equity + benefits

The actual salary will depend on level, location, qualifications, and experience. The range displayed on each job posting reflects new hire salaries for the position across all US locations. Benefits include:

  • Competitive compensation with equity
  • 12.5 Company-wide Holidays
  • Flexible vacation days
  • 10 sick days
  • Generous parental leave policy
  • Health, dental, and vision insurance
  • 401(k) with employer matching
  • Professional growth opportunities
  • Team-building activities

At CFS, we excel in fast-paced environments, driven by our values of integrity, execution, impact, and self-critique. As we grow, we're eager to bring on mission-driven folks who offer diverse perspectives and fresh ways to tackle challenges.

We value diversity deeply and are proud to be an equal opportunity employer by choice. We consider all qualified applicants equally, regardless of race, color, national origin, ancestry, citizenship status, protected veteran status, religion, physical or mental disability, marital status, sex, sexual orientation, gender identity or expression, age, or any other basis protected by law.

This role requires compliance with U.S. laws concerning the export of controlled or protected technologies or information (collectively, "Export Control Laws"). Any offer of employment will be contingent on the need for compliance with such Export Control Laws.

Get Job Alerts

Get job alerts for opportunities in Devens, Massachusetts, United States

About the role

December 18, 2025

Full Time

Company

January 2, 2026

Hybrid

USD 110k–185k yearly

Commonwealth Fusion Systems

cfs.energy

  •  Devens, Massachusetts, United States

7+ years in relevant fields

UTC-05:00

Apply now

Job expired?

Please let Commonwealth Fusion Systems know you found this job on Rejobs. This will help us grow and get more people to work on renewable energy!

Discover how you’re connected

View connections

See your contacts at Commonwealth Fusion Systems on LinkedIn to leverage your network in applying for this position.