Nuclear Fuel Assembly Engineer

ABOUT SUBCRITICAL SYSTEMS

Subcritical Systems, Inc. is a venture-backed startup in Austin, Texas building accelerator driven systems and the only US commercial manufacturer of accelerator cavities. What SpaceX did for rockets, we plan to do for accelerator cavities and commercialize across applications of power production, medical isotopes, semiconductors and waste transmutation.

We are in the process of building the Energy Amplifier, a novel nuclear fission system in which a particle accelerator drives a subcritical core, making meltdown physically impossible for clean power production. Due to its inherent safety, our system has a more streamlined licensing process. Our founding team includes successful entrepreneurs with a track record of building several multibillion dollar companies in deep-tech, and scientists who were leading U.S. national labs with deep experience in accelerator & nuclear technologies.

We are actively hiring to expand our team as we work toward licensing, regulatory submissions, and construction of our first energy amplifier. More information is available at subcritical.com.

ROLE SUMMARY

We seek a motivated mechanical engineer to lead the design and fabrication of nuclear fuel assemblies for the subcritical core of SSI's Energy Amplifier. The fuel assemblies constitute the heart of the subcritical assembly and must perform in an incredibly harsh environment of intense heat and radiation. Reporting to the SVP for Nuclear, the selected candidate will be an integral member of the subcritical core team responsible for designing, prototyping, and constructing the core.

KEY RESPONSIBILITIES

Design & Analysis

• Working closely with the core materials and neutronics teams, perform thermal and structural assessments of fuel assemblies to inform the selection of materials and geometries of fuel assembly components.
• Conduct CFD and FEA analyses to validate that fuel assembly designs meet operational and safety requirements across the full range of normal, transient, and credible event conditions.
• Evaluate and select joining techniques appropriate for high-temperature, high-radiation fuel assembly components.
• Collaborate with the neutronics team to optimize fuel assembly geometry for neutronic performance while satisfying structural, thermal-hydraulic, and radiation damage constraints.
• Develop and maintain detailed design documentation, including drawings, specifications, and design basis reports for fuel assembly components.

Procurement & Fabrication

• Engage with potential vendors early in the design process to ensure components are manufacturable in the most cost-effective manner.
• Produce procurement packages, qualify vendors, and manage fabrication to appropriate quality standards.
• Conduct supplier audits and source inspections; review and approve fabrication traveler documentation and nonconformance reports.

Licensing & Compliance

• Ensure designs comply with applicable codes and standards and prepare supporting regulatory documentation.
• Support interactions with the NRC and other regulatory bodies on fuel assembly design and qualification.

Program Execution

• Track key technical milestones and deliver results within aggressive timelines.
• Identify and escalate technical risks; drive resolution across teams.
• Document work in reports, presentations, and regulatory submissions.

QUALIFICATIONS

Required

• Demonstrated technical expertise in thermal hydraulic analysis, including computational fluid dynamics, and in structural analysis.
• Strong work ethic, resilient, able to work in a fast-paced environment, driven, and passionate about the field.
• B.S or M.S. in mechanical engineering.

Preferred

• Familiarity with nuclear fuel assembly design, irradiation behavior of nuclear materials, and relevant codes and standards.
• Familiarity with and experience in applying AI tools to enhance productivity.

BENEFITS

Benefits: We offer health, dental, and vision insurance.

LOCATION & WORK POLICY

This role is fully on-site in Austin, Texas. Our facility is located near Austin Airport.

HOW TO APPLY

Apply on LinkedIn or submit your resume and a brief cover letter to careers@subcritical.com with the subject line "[Job Title] - Application". Applications are reviewed on a rolling basis.