Thermal-Hydraulics and Safety Analysis Engineer - Isotopes

Thanks for your interest in Oklo!  We are searching for a Thermal-Hydraulics and Safety Analysis Engineer to join our isotope engineering team to own the thermal hydraulic safety case for the next generation of domestic isotope production facilities.

Position Description

The Thermal-Hydraulics and Safety Analysis Engineer is responsible for developing and executing systems-level thermal-hydraulic analyses that support the safety case, design basis, and licensing of Oklo's reactor systems. This engineer will evaluate reactor and plant response during normal operation, anticipated operational occurrences, and postulated accident conditions using codes such as RELAP5 and other systems-analysis tools.

This role combines hands-on transient modeling with safety-methodology development. The engineer will establish modeling approaches, assess code and model applicability, quantify uncertainty, and produce clear, auditable technical documentation suitable for licensing applications and regulatory review. The engineer will work closely with safety, licensing, reactor physics, thermal-hydraulics, controls, and system-design teams to connect analysis assumptions and acceptance criteria to an evolving reactor design.

This position is focused on thermal-hydraulic safety analysis and licensing support. It does not own source-term, radiological-consequence, or severe-accident progression analysis, although collaboration with engineers performing those analyses may be required.

The isotope engineering team is a small but growing team, so the candidate must be capable of operating in a highly iterative and independent environment.

Specific responsibilities may include:

• Develop, maintain, and execute systems-level thermal-hydraulic models of reactor and plant behavior using RELAP5 or comparable analysis codes.

• Analyze normal operating conditions, anticipated operational occurrences, design-basis events, and selected beyond-design-basis conditions relevant to the thermal-hydraulic safety case.

• Develop event-specific analysis plans, including initial and boundary conditions, assumptions, acceptance criteria, figures of merit, and treatment of uncertainties.

• Develop and document thermal-hydraulic safety-analysis methods, modeling guidance, and engineering practices appropriate to advanced reactor licensing.

• Establish and justify code, model, and correlation applicability for the physical phenomena and operating regimes being evaluated.

• Perform model verification, validation, sensitivity studies, uncertainty analyses, scaling evaluations, and comparisons with experiments, benchmarks, hand calculations, or higher-fidelity analyses. Identify gaps in available methods, data, and validation evidence, and define practical plans to close those gaps.

• Translate regulatory requirements and safety acceptance criteria into defensible analysis requirements and technical evaluation strategies.

• Prepare high-quality calculation packages, methodology documents, safety-analysis reports, licensing-application content, and responses to regulator questions.

• Evaluate design changes and provide timely feedback on their effects on transient response, safety margins, system performance, and the licensing basis.

• Collaborate with reactor physics, fuel, controls, mechanical, thermal-hydraulics, safety, and licensing engineers on coupled analyses and interface conditions.

• Develop scripts and automated workflows for model generation, execution, post-processing, regression testing, and configuration control.

• Review safety analyses and models prepared by internal contributors, vendors, and external partners.

Minimum Qualifications:

• Bachelor's, master's, or doctoral degree in nuclear, mechanical, chemical, or aerospace engineering, or a closely related technical field.

• Five or more years of relevant experience in reactor thermal-hydraulics, nuclear safety analysis, reactor transient analysis, or a closely related field. A relevant advanced degree may substitute for a portion of the professional experience.

• Demonstrated experience developing and executing systems-level transient models using RELAP5.

• Strong foundation in heat transfer, fluid mechanics, thermodynamics, and reactor thermal-hydraulics.

• Experience defining and analyzing reactor transients or accident scenarios, including initial conditions, boundary conditions, equipment response, operator or control actions, and acceptance criteria.

• Experience evaluating the reasonableness and applicability of models, correlations, assumptions, and results rather than treating analysis software as a black box.

• Experience documenting engineering analyses in clear, reviewable technical reports or calculation packages.

• Ability to work independently while collaborating effectively across engineering and licensing disciplines.

• Experience with verification and validation, uncertainty quantification, sensitivity analysis, scaling, bias evaluation, or code applicability assessments.

• Familiarity with experiment design, separate-effects and integral-effects testing, benchmark problems, and the use of test data to validate analytical methods.

Bonus Qualifications:

• Experience supporting NRC or DOE licensing applications, audits, topical or methodology reports, requests for additional information, or other regulatory interactions.

• Fluency with Python or another language used for model automation, data analysis, visualization, and quality checks.

• Competency with modern software engineering practices, including version control, automated testing, reproducible computing environments, and continuous integration.

• Experience working under a nuclear quality-assurance program or with safety-related analysis software and records.

• Experience mentoring other analysts or providing technical review of safety-analysis work.

Competencies

We are looking for a Thermal-Hydraulics and Safety Analysis Engineer who is:

• Skilled at developing and interpreting systems-level reactor transient analyses.

• Able to connect thermal-hydraulic behavior, safety functions, acceptance criteria, and licensing conclusions.

• Methodical about verification, validation, uncertainty, configuration control, and technical documentation.

• Comfortable making conservative but technically defensible assumptions when information is incomplete.

• Able to distinguish important safety drivers from modeling detail that does not materially affect a conclusion.

• Comfortable explaining model limitations and uncertainty to designers, reviewers, and regulators.

• Collaborative and effective at working across safety, licensing, design, reactor physics, and analysis teams.

• Passionate about clean energy, and about making domestic supply of national-need and therapeutic isotope production a reality.

• Willing and able to learn quickly, think differently, and do things in new ways.

• Comfortable in a fast-paced, highly iterative startup environment.

• An excellent writer who can write in a modern active voice, and able to communicate technical content and results verbally.

Who you are:

A startup person: You aren't driven by titles or hierarchy, and prefer efficiency to excess process. You don't need or expect to have a lot of guidance but you enjoy working in a fast-paced team. If you prefer the culture and feel of a large organization, that is great, but you likely won’t enjoy working with us! There is plenty of important work and plenty of good opportunities with organizations like that.

Motivated: You are self-motivated. You bring an enthusiasm to the team, and imbue a sense of passion that goes beyond clocking in and clocking out. This isn’t about a fake or arbitrary “pieces of flair” mentality or lack of work-life balance! It is about being a part of the vision and feeling a part of reaching team goals.

A team-player: Oklo genuinely is a team. We aren’t about taking credit for ourselves, and we aren’t about pushing blame to others. We do incredible things because we work as a team.

An excellent communicator: We need a person who is not only technically competent but also a clear and upbeat communicator.

Creative: Being creative means that when things fall outside clear scopes or processes or problems arise without clear solutions, you are able to identify it as well as invent ways to solve a problem or fill a need without micromanagement. The successful person in this job will not only be creative, but also enjoy being creative and solving open-ended problems which may change day-by-day.

Detail-oriented: This focus is a big part of excellence, consistency, and quality. Excellent grammar and spelling matter for both good communication as well as the image of the company that we put forward.

About Oklo travel requirements:

Oklo requires remote employees to travel to headquarters (Santa Clara, CA) twice a quarter annually, based on business or team needs, including attendance at team meetings, off-sites, and other company events or gatherings. For the first two weeks of onboarding, employees are required to be in person at headquarters in Santa Clara, CA.

About Oklo compensation:

The salary range for this position is $150,000 to $200,000, subject to experience level.

Oklo offers flexible time off, equity, bonuses, competitive pay, 401(k), health insurance (with employer contribution), HSA, FSA, flexible work hours, wellness credits, and other benefits.

This position may involve access to information subject to U.S. export control laws. Only applicants who meet the definition of a U.S. person under applicable laws may be eligible.

About Oklo Inc.: Oklo Inc. is developing fast fission power plants to deliver clean, reliable, and affordable energy at scale; establishing a domestic supply chain for critical radioisotopes; and advancing nuclear fuel recycling to convert nuclear waste into clean energy. Oklo was the first to receive a site use permit from the U.S. Department of Energy for a commercial advanced fission plant, was awarded fuel material from Idaho National Laboratory, and submitted the first custom combined license application for an advanced reactor to the U.S. Nuclear Regulatory Commission. Oklo is also developing advanced fuel recycling technologies in collaboration with the U.S. Department of Energy and U.S. National Laboratories.

#CHOP: Oklo’s Values
Collaboration: We go further, together. We bring diverse perspectives, listen actively, and build trust through transparency and respect. We work across disciplines, sharing ownership to turn complex challenges into shared successes.
Humility: We are team players who act for the good of the company and for the world. We are focused on our mission, not personal recognition.
Ownership: We take pride in what we do and how we do it. We are proactive in finding solutions and see tasks through  to completion. We are committed to delivering on our promises to provide clean, reliable, and affordable energy.
Pathfinding: We chart new ground where no path exists by approaching challenges with curiosity, courage, and creativity while navigating ambiguity.