Thermal-Hydraulics and Safety Analysis Engineer - Isotopes

OKLO; Santa Clara (CA); Hybrid; USD 150,000 - 200,000; Full time

Benefits offered by this job

Flexible time off

Equity participation

Bonuses

Job summary

Oklo is seeking a Thermal-Hydraulics and Safety Analysis Engineer for isotope production facilities. You will develop and execute system-level transient analyses to support safety cases, licensing, and regulatory reviews.

The role requires collaboration with safety, licensing, reactor physics, and design teams, and involves ensuring defensible results with clear documentation. You will work in a fast-paced, iterative environment to connect analysis assumptions with licensing criteria, using

Qualifications

• Bachelor's, master's, or doctoral degree in a relevant engineering field.
• 5+ years in reactor thermal-hydraulics or nuclear safety analysis.
• Experience developing and executing systems-level transient models using RELAP5.
• Strong foundation in heat transfer, fluid mechanics, thermodynamics, and reactor TH.
• Ability to document analyses in clear, reviewable reports or calculation packages.

Responsibilities

• Develop and maintain systems-level thermal-hydraulic models using RELAP5.
• Analyze operating conditions, design-basis events, and significant beyond-design events.
• Develop event-specific analysis plans with boundaries, assumptions, and uncertainties.
• Document TH safety-analysis methods, modeling guidance, and practices.
• Collaborate with safety, licensing, reactor physics, and design teams on analyses.

Skills

Thermal-hydraulics

Transient analysis

Uncertainty quantification

Regulatory documentation

Independent work

Cross-functional collaboration

Education

Bachelor's degree in nuclear, mechanical, chemical, or aerospace engineering

Master's or Doctoral degree preferred

Tools

RELAP5

Python

Version control (Git)

Job description

Thermal-Hydraulics and Safety Analysis Engineer - Isotopes

Santa Clara, CA or Remote

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.

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.

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.

Oklo’s Values — Collaboration, Humility, Ownership, Pathfinding. We value teamwork, transparency, and curiosity in approaching challenges.

Candidates should be aware that employment may be contingent upon successful completion of a drug screening, and employees may be subject to drug testing at any time in accordance with company policy and applicable laws.