Senior Mechanical Engineer, Mechanisms

Department: Engineering

Location: El Segundo, CA

Compensation: $133.5K – $184.8K • Offers Equity

Employment Type: FullTime

About Radiant

Radiant is an El Segundo, CA-based startup building the world’s first mass-produced, portable nuclear microreactors. The company’s first reactor, Kaleidos, is a 1-megawatt, fail-safe microreactor that can be transported anywhere power is needed and run for up to 5 years without refueling. Portable nuclear power with rapid-deploy capability can replace similar-sized diesel generators and provide critical asset support for hospitals, data centers, remote sites, and military bases. Radiant’s unique, practical approach to nuclear development leverages modern software engineering to rapidly deliver safe, factory-built microreactors that use existing, well-qualified materials. Founded in 2020, Radiant is on track to test its first reactor at the Idaho National Laboratory this summer, with initial customer deliveries beginning in 2028.

About the Role

Radiant is seeking a highly motivated Senior Mechanical Engineer, Mechanisms to design and develop critical mechanisms within Kaleidos. You will solve unique challenges creating efficient and reliable mechanisms that control reactivity or actuate critical safety features. You will be responsible for the following: trade studies, material selection, detailed structural analysis, assembly, integration, and testing. You will have an instrumental impact of fueling the first new commercial reactor design in over 50 years by 2026.

Responsibilities & Duties:

• Ownership of critical mechanisms such as the control blade actuator or air jacket valves.

• Conduct trade studies and develop designs to meet program requirements.

• Perform detailed thermomechanical analysis (static strength, durability/fatigue) and kinematic analysis to determine structural integrity and performance margins using both hand calculations and finite element tools.

• Develop and execute manufacturing/assembly instructions and test plans.

• Create and manage a Bill-Of-Materials (BOM).

• Find and develop suppliers for components.

• Own subassembly design, manufacturing, and test schedules.

• Own risk analysis (FMEA) for subsystems.

• Collect requirements, provide expertise and feedback to engineers in other functional areas via clear, constructive communication.

Required Qualifications & Skills:

• Bachelor’s degree from an accredited institution in Mechanical or Aeronautical Engineering.

• 4+ years of experience designing mechanisms.

• 4+ years of experience performing stress analysis using both hand calculations and finite element tools (Abaqus, Ansys, FEMAP, or similar).

Desired Qualifications & Skills:

• Experience with design of multi-component assemblies in CAD (NX or similar).

• Experience designing hardware that was manufactured, deployed, and iteratively improved.

• Experience designing pneumatic systems.

• Experience integrating electromechanical components such as motors or encoders.

• Experience working with interdisciplinary teams.

• Solid understanding and application of GD&T.

• Proficiency with both “hand calc” analytical methods and higher fidelity finite element-based analysis methods.

• Ability to derive free-body diagrams for systems with which one was not previously familiar.

• Self-motivated with strong organizational, written, and oral communication skills.

• Experience with using text-based software development tools.

Additional Requirements:

• Must be willing to work extended hours and weekends as necessary to accomplish our mission.

• Must work 100% onsite at El Segundo HQ.

Benefits and Perks

• Stock: Substantial incentive stock plan for all full-time employees.

• Medical: 100% up to base silver level plan for employee + 50% dependents, offers up to Platinum plans.

• One Medical: Sponsored memberships for employees and their dependents.

• Vision: 100% top tier plan coverage + 50% for dependents.

• Dental: 100% top tier plan coverage, orthodontia extra, 50% for dependents.

• Voluntary life, accident, hospital, critical illness, commuter and FSA/HSA are offered as employee contributed benefits.

• 8-weeks of paid parental leave for all parents. Additional paid pregnancy leave for CA employees.

• Daily catered lunch. Free snacks and drinks.

• Flexible PTO policy. Remote workday allocation.

• Company and team-bonding events, happy hours and in-person camaraderie.

• Beautiful El Segundo headquarters close to the Pacific Ocean.

Total Compensation and Benefits
Radiant compensates people for impact and invests in those who continue to raise the bar. Radiant’s new hire compensation package includes base salary, substantial equity grants, and comprehensive health benefits. Total compensation and level are determined through a rigorous evaluation of interview performance, experience, education, and qualifications, and are designed to support continued growth as scope, responsibility, and impact expand at Radiant.

The best of today’s advanced reactor builders don’t wait for job postings. They join the winning team. If that’s you, contact us directly for immediate opportunities: recruiting@radiantnuclear.com.

We are an equal opportunity employer and all qualified applicants will receive consideration for employment without regard to race, color, religion, sex, sexual orientation, gender identity or expression, pregnancy, age, national origin, disability status, genetic information, protected veteran status, or any other characteristic protected by law.

This position involves access to technology that is subject to U.S. export controls. Any job offer made will be contingent upon the applicant’s capacity to serve in compliance with U.S. export controls.