About Radiant Radiant is an El Segundo, CA-based company building the world's only mass-produced, transportable nuclear microreactors. The U.S. grid is under growing strain, with power demand accelerating, driving higher utility costs, rising carbon emissions, and interconnection backlogs. Radiant has a solution, transportable, on-site power. Our first reactor, Kaleidos, is 1 megawatt: small enough to be factory-built, transported by land, sea, or air, and deployed wherever power is needed. 1 MW can power 1000 homes for five years. Ship it back and we refuel for a 20 year operating life. We made energy a product that can be used for critical infrastructure like military bases, data centers, hospitals, and remote sites, as well as the commercial main street businesses that keep America running. Founded in 2020, Radiant is under contract to deliver power to the U.S. Army, Navy and Air Force and has signed pre-order agreements with Equinix, with deployments beginning in 2028. About the Role Radiant is seeking a Senior Safety Analysis Engineer to lead reactor safety analyses supporting the design, testing, and deployment of Kaleidos. You will evaluate reactor behavior during normal, transient, and accident conditions, assess safety margins, and develop technically defensible analyses that inform reactor design decisions and regulatory evaluations. This role combines reactor systems and thermal-hydraulic analysis with fuel performance, source term development, and radiological consequence assessments. You will own complex analytical work from methodology development and model execution through uncertainty evaluation, technical review, and documentation, working closely with nuclear design, thermal, mechanical, materials, testing, and regulatory teams. The ideal candidate brings strong reactor safety fundamentals, hands-on modeling experience, and sound engineering judgment. You should be comfortable identifying dominant physical phenomena, evaluating analytical uncertainties, and translating complex results into practical design and safety decisions. Responsibilities & Duties • Lead deterministic reactor safety analyses covering anticipated operational occurrences, transients, and postulated accident scenarios. • Develop and apply system-level thermal-hydraulic and transient models to evaluate reactor response, operating limits, and safety margins. • Perform source term and radiological consequence analyses, including fuel performance, fission product release and transport, and dose evaluations. • Evaluate uncertainties in reactor physics, power distributions, fuel behavior, and thermal-hydraulic models and their impact on safety conclusions. • Apply sensitivity studies, bounding assumptions, and phenomena-ranking methods to develop technically defensible analysis approaches. • Collaborate with nuclear, mechanical, thermal, materials, and controls teams to establish analysis inputs, evaluate design alternatives, and resolve safety-related technical challenges. • Partner with testing and materials teams to identify data gaps, establish validation requirements, and correlate analytical predictions with experimental results. • Develop and improve safety analysis methods, models, and tools, including verification and validation, configuration control, and uncertainty quantification. • Prepare and technically review calculation packages, safety analysis reports, and regulatory documentation supporting reactor design and licensing activities. • Work with regulatory and safety teams to establish safety requirements, support technical submissions, and resolve technical issues through closure. Required Qualifications & Skills • Bachelor's degree in nuclear engineering, mechanical engineering, or a related technical discipline from an accredited institution. • 5+ years of relevant experience in reactor safety analysis, thermal-hydraulics, nuclear systems modeling, or related engineering disciplines. • Experience developing and applying reactor systems or safety analysis codes such as RELAP5-3D, TRACE, SAM, MELCOR, or equivalent tools. • Strong understanding of reactor thermal-hydraulics, transient behavior, heat transfer, and deterministic safety analysis. • Knowledge of reactor physics, fuel performance, fission product behavior, and radiological safety principles. • Experience developing or evaluating source terms, radiological consequences, or other safety-related performance calculations. • Experience evaluating modeling assumptions, uncertainty, sensitivity, and conservatism in engineering analyses. • Demonstrated ability to independently own complex analytical projects and translate results into design requirements, safety conclusions, and technical documentation. • Strong written and verbal communication skills, including experience preparing rigorous calculation packages, technical reports, or safety-related engineering documentation. Preferred Qualifications & Skills • Master's degree or Ph.D. in nuclear engineering, mechanical engineering, or a related technical discipline. • Experience with high-temperature gas-cooled reactors, microreactors, advanced reactors, or first-of-a-kind nuclear systems. • Experience with TRISO fuel performance, irradiation behavior, fuel failure mechanisms, and fission product release and transport. • Familiarity with source term, dose consequence, or fuel performance tools such as ORIGEN, MACCS, PARFUME, or BISON. • Experience with reactor physics and neutronics tools such as MCNP, OpenMC, Serpent, or SCALE. • Familiarity with probabilistic risk assessment (PRA), licensing basis event selection, and risk-informed safety methodologies. • Experience with safety analysis code verification and validation, uncertainty quantification, and nuclear quality assurance practices. • Familiarity with DOE authorization processes, NRC licensing frameworks, nuclear industry codes and standards, or regulatory safety analysis. • Experience supporting reactor testing, safety basis d