Principal Software Engineer, Compute

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 driven Principal DevOps Engineer to own on‑site High‑Performance Compute (HPC) infrastructure, deployment, and automation projects in tight collaboration with hard‑science users and cloud infrastructure engineers. You will work closely with the software team to design scalable, secure, and resilient DevOps practices, tools, and systems across the entire organization. As a technical lead, you will define team scope, shape individual responsibilities, and serve as the primary liaison between engineering and software teams, acting as the subject‑matter expert on workflows, tools, and optimizations. The ideal candidate is patient, organized, and comfortable managing high volumes of cross‑disciplinary requests, capable of diving deep into complex legacy stacks and synthesizing findings. The infrastructure you manage, the pipelines you build, and the developer productivity culture you establish will help design, run, and mass‑produce the first high‑temperature gas‑cooled portable microreactor ever commercialized. Responsibilities & Duties Lead HPC initiatives as driven by the software org, establishing responsibilities, project scope, and technical mentorship. Serve as the go‑between for engineering teams and software, fielding HPC questions, simulation software issues, and infrastructure needs from nuclear, thermal, materials, mechanical, and electrical engineers, translating them into actionable work. Own workflows, tooling, and performance for scientific computing, including Ansys, STAR‑CCM+, and Abaqus, covering licensing, environment setup, job orchestration, and results infrastructure. Triage inbound infrastructure requests, HPC/MPI/Linux debugging, job failure analysis, shell and systems mentorship, while prioritizing effectively and communicating clearly across stakeholders. Partner with DevOps engineers to architect and maintain infrastructure across AWS and on‑premises Linux environments, ensuring high availability, security, and performance for mission‑critical systems. Dive deep into HPC software, workload scheduling, data movement, storage hierarchies, and compute environments to build robust, high‑throughput Linux systems. Modernize legacy scientific computing systems and tooling, migrating to current stacks to improve maintainability, performance, and developer experience. Architect tools supporting build systems, testing frameworks, deployment automation, and developer environments. Design and maintain networking infrastructure for distributed simulation systems, optimizing data transfer between HPC clusters. Required Qualifications & Skills Bachelor’s degree in Computer Science, Engineering, or a related technical field. 8+ years of professional experience in DevOps, Site Reliability, Infrastructure, or Platform Engineering. Expert‑level proficiency in one or more languages: Python, Golang, Rust, C#, or C/C++. Strong code review skills, including the ability to read stack traces and chase down dense rabbit holes in high‑compliance, legacy scientific software environments. Working experience with Kubernetes and Docker for orchestration and deployment. Deep Linux and sysadmin fluency, file systems, process management, and networking, with a hard‑science approach to problem‑solving. Exceptional communication skills, organized, and effective when fielding a high volume of questions and requests from engineering stakeholders. Ability to dive deep into complex, nested legacy stacks and then zoom out to synthesize findings clearly for a broader technical audience. Desired Qualifications & Skills Hands‑on physical infrastructure experience: server hardware, rack configuration, data center ops, or high‑throughput networking (InfiniBand, Slingshot, AWS EFA). Scientific computing experience with direct exposure to HPC environments, simulation workloads, or academic/research computing (SLURM, PBS, MPI, Lustre, EFS, AWS ParallelCluster, PCS, etc.). Cloud DevOps experience, production‑grade work with Kubernetes, Ansible, Terraform, or AWS in a cloud‑native or hybrid environment. Experience working cross‑functionally with engineering teams across mechanical, electrical, materials, and nuclear disciplines. 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: View email address on click.appcast.io. 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. Compensation Range: $200,500 – $314,475 #J-18808-Ljbffr Radiant