<div>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 failsafe microreactor that can be transported anywhere power is needed and run for up to five years without the need to refuel. 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 utilizes modern software engineering to rapidly achieve safe, factory-built microreactors that leverage existing, well-qualified materials. Founded in 2020, Radiant is on track to test its first reactor next year at the Idaho National Laboratory, with initial customer deliveries beginning in 2028.</div>Internship - Mechanical Engineer (Fluid Systems, Mechanisms, or Structures) Radiant is seeking a highly motivated Mechanical Engineering Intern for Fall 2025. Under the KDU Engineering team, you will be responsible for a project tailored towards the finalization of the design, assembly and testing of the Kaleidos Development Unit – the United States’ first new fueled reactor design in over 50 years. You will be tasked with this project based on your skillset (fluid systems, mechanisms, or structures) and our organization’s priority. You’ll learn from a direct mentor, cross-functional teammates, and have a tangible impact on the readiness of KDU for fueled operations next year. Please note: we plan to begin interviewing for Summer 2026 internships in November/December. Responsibilities and Duties:    <ul><li>Own all aspects of a project within given discipline. </li><li>Deliver project on time and with minimal supervision to accelerate KDU development. </li><li>Present a final project review at the end of internship to engineers and leadership.   </li></ul>Required Skills and Qualifications:  <ul><li>Strong connection to engineering first principles expected from a third-year engineering student (thermodynamics, fluid mechanics, statics, dynamics, strength of materials). </li><li>Currently pursuing BS in mechanical engineering, aerospace engineering, or related discipline.  </li><li>Hands on project examples outside of the classroom such as extracurricular projects, clubs, research, lab work or personal projects.  </li></ul>Desired Skills and Qualifications:  <ul><li>Currently pursuing MS in mechanical engineering, aerospace engineering, or related discipline.  </li><li>A high level of independence in solving challenging engineering tasks is preferred.   </li><li>Ability to seek out resources and proactively ask questions to finish projects through completion effectively, accurately, and timely.   </li><li>Ability to work in a fast-paced startup environment with a proactive and collaborative attitude.  </li><li>Genuinely excited for our mission to rapidly deploy nuclear microreactors to remote locations requiring abundant, clean energy. </li><li>Knowledge of reactor physics will provide useful context but is not necessary.  </li><li>Prior internship experience helpful but not required.  </li></ul>Additional Requirements:   <ul><li>This internship will require working onsite at our El Segundo HQ.</li><li>You may be asked to work extended hours or weekends occasionally to support project goals.</li></ul><div>Total Compensation and BenefitsRadiant's new hire compensation package includes base salary, substantial equity grants, and comprehensive benefits. Total compensation and level are determined through a holistic evaluation of your interview performance, experience, education, and qualifications. Benefits and Perks for Eligible Employees:<ul><li>Stock: Substantial incentive stock plan for all full-time employees.</li><li>Medical: 100% up to base silver level plan for employee + 50% dependents, offers up to Platinum plans.</li><li>One Medical: Sponsored memberships for employees and their dependents.</li><li>Vision: 100% top tier plan coverage + 50% for dependents.</li><li>Dental: 100% top tier plan coverage, orthodontia extra, 50% for dependents.</li><li>Voluntary life, accident, hospital, critical illness, commuter and FSA/HSA are offered as employee contributed benefits.</li><li>8-weeks of paid parental leave for all parents. Additional paid pregnancy leave for CA employees.</li><li>Daily catered lunch. Free snacks and drinks.</li><li>Flexible PTO policy. Remote workday allocation.</li><li>Company and team-bonding events, happy hours and in-person camaraderie.</li><li>Beautiful El Segundo headquarters close to the Pacific Ocean.</li></ul>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.Unfortunately, we are unable to provide visa sponsorship at this time. 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. </div>

Radiant is a clean energy startup building a nuclear microreactor. A climate-friendly alternative to diesel generators, Radiant's Kaleidos 1MW microreactor will be the world's first portable, zero-emissions power source that works anywhere. We plan to test our development reactor by 2026 and if successful, it will be the first new commercial reactor design to achieve a fueled test in over 50 years. Our microreactor can bring power to remote parts of the world and provide backup power for life-saving applications in hospitals or disaster-relief scenarios.&nbsp;

Summer 2026 Internship - Mechanical Engineer (Fluid Systems, Mechanisms, or Structures)

<div>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 failsafe microreactor that can be transported anywhere power is needed and run for up to five years without the need to refuel. 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 utilizes modern software engineering to rapidly achieve safe, factory-built microreactors that leverage existing, well-qualified materials. Founded in 2020, Radiant is on track to test its first reactor next year at the Idaho National Laboratory, with initial customer deliveries beginning in 2028.</div>Internship - Mechanical Engineer (Fluid Systems, Mechanisms, or Structures)&nbsp;Radiant is seeking a highly motivated Mechanical Engineering Intern for Fall 2025. Under the KDU Engineering team, you will be responsible for a project tailored towards the finalization of the design, assembly and testing of the Kaleidos Development Unit – the United States’ first new fueled reactor design in over 50 years. You will be tasked with this project based on your skillset (fluid systems, mechanisms, or structures) and our organization’s priority. You’ll learn from a direct mentor, cross-functional teammates, and have a tangible impact on the readiness of KDU for fueled operations next year.&nbsp;Please note: we plan to begin interviewing for Summer 2026 internships in November/December.&nbsp;Responsibilities and Duties:   &nbsp;<ul><li>Own all aspects of a project within given discipline.&nbsp;</li><li>Deliver project on time and with minimal supervision to accelerate KDU development.&nbsp;</li><li>Present a final project review at the end of internship to engineers and leadership.  &nbsp;</li></ul>Required Skills and Qualifications: &nbsp;<ul><li>Strong connection to engineering first principles expected from a third-year engineering student (thermodynamics, fluid mechanics, statics, dynamics, strength of materials).&nbsp;</li><li>Currently pursuing BS in mechanical engineering, aerospace engineering, or related discipline. &nbsp;</li><li>Hands on project examples outside of the classroom such as extracurricular projects, clubs, research, lab work or personal projects. &nbsp;</li></ul>Desired Skills and Qualifications: &nbsp;<ul><li>Currently pursuing MS in mechanical engineering, aerospace engineering, or related discipline. &nbsp;</li><li>A high level of independence in solving challenging engineering tasks is preferred.  &nbsp;</li><li>Ability to seek out resources and proactively ask questions to finish projects through completion effectively, accurately, and timely.  &nbsp;</li><li>Ability to work in a fast-paced startup environment with a proactive and collaborative attitude. &nbsp;</li><li>Genuinely excited for our mission to rapidly deploy nuclear microreactors to remote locations requiring abundant, clean energy.&nbsp;</li><li>Knowledge of reactor physics will provide useful context but is not necessary.&nbsp;&nbsp;</li><li>Prior internship experience helpful but not required. &nbsp;</li></ul>Additional Requirements:  &nbsp;<ul><li>This internship will require working onsite at our El Segundo HQ.</li><li>You may be asked to work extended hours or weekends occasionally to support project goals.</li></ul><div>Total Compensation and BenefitsRadiant's new hire compensation package includes base salary, substantial equity grants, and comprehensive benefits. Total compensation and level are determined through a holistic evaluation of your interview performance, experience, education, and qualifications.&nbsp;Benefits and Perks for Eligible Employees:<ul><li>Stock: Substantial incentive stock plan for all full-time employees.</li><li>Medical: 100% up to base silver level plan for employee + 50% dependents, offers up to Platinum plans.</li><li>One Medical: Sponsored memberships for employees and their dependents.</li><li>Vision: 100% top tier plan coverage + 50% for dependents.</li><li>Dental: 100% top tier plan coverage, orthodontia extra, 50% for dependents.</li><li>Voluntary life, accident, hospital, critical illness, commuter and FSA/HSA are offered as employee contributed benefits.</li><li>8-weeks of paid parental leave for all parents. Additional paid pregnancy leave for CA employees.</li><li>Daily catered lunch. Free snacks and drinks.</li><li>Flexible PTO policy. Remote workday allocation.</li><li>Company and team-bonding events, happy hours and in-person camaraderie.</li><li>Beautiful El Segundo headquarters close to the Pacific Ocean.</li></ul>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.Unfortunately, we are unable to provide visa sponsorship at this time. 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. </div>

Summer 2026 Internship - Mechanical Engineer (Fluid Systems, Mechanisms, or Structures)

About the Job

About the Company

Radiant

Similar Jobs

Summer 2026 Internship - Engineering

Summer 2026 Internship - Engineering

Mechanical and Manufacturing Engineering Internship - Summer 2026

Mechanical and Manufacturing Engineering Internship - Summer 2026

2026 Summer Innovative Solutions - Civil / Mechanical / Industrial Engineer Intern

2026 Summer Innovative Solutions - Civil / Mechanical / Industrial Engineer Intern

Mechanical Engineer - 2026 New Grad (Fluid Systems, Mechanisms, or Structures)

Mechanical Engineer - 2026 New Grad (Fluid Systems, Mechanisms, or Structures)

Summer 2026 Internship - Mechanical Engineering

Summer 2026 Internship - Mechanical Engineering

Design Engineer Intern - Spring 2026

Design Engineer Intern - Spring 2026

Engineer Intern - Modeling & Simulation (Summer 2026)

Engineer Intern - Modeling & Simulation (Summer 2026)

Mechanical Engineering Design Intern

Mechanical Engineering Design Intern

Mechanical Engineering Design Intern

Mechanical Engineering Design Intern

Mechanical Engineering Intern (Summer 2026+)

Mechanical Engineering Intern (Summer 2026+)