Reactor Core Thermal Fluids Engineer

Oklo Inc. is an advanced nuclear fission technology company developing small, fast fission power plants called Aurora powerhouses, designed to deliver clean, reliable energy directly to customers under long-term power purchase agreements. Beyond power generation, Oklo operates across three interconnected business lines: power generation, nuclear fuel recycling, and production of medical and industrial isotopes, positioning itself as a vertically integrated nuclear energy and materials company. Its reactors are designed to use recycled nuclear fuel, including used fuel and nuclear waste, reducing the need for newly mined uranium and addressing long-standing nuclear waste challenges. The company's mission centers on providing abundant, carbon-free energy to combat climate change while modernizing the nuclear industry through faster deployment timelines, compact reactor designs, and innovative fuel cycles. By recycling nuclear waste into usable fuel, Oklo aims to turn a historical liability of the nuclear industry into a resource, supporting both sustainability goals and energy security. Its isotope production business also supports critical applications in medicine, industry, and scientific research, diversifying its impact beyond electricity generation. Oklo differentiates itself through its compact, fast-spectrum reactor design that can be deployed rapidly (in under a year per site), its direct-to-customer power sales model, and its integrated approach spanning power, fuel, and isotopes. Backed by high-profile investors and leadership, including chairman Sam Altman, Oklo has advanced through regulatory processes with the U.S. Nuclear Regulatory Commission and is pursuing projects across multiple U.S. states, positioning itself as a leader in the next generation of advanced nuclear deployment.

Thanks for your interest in Oklo!  We are searching for a Thermal Fluids Engineer to join our Core Thermal-Hydraulics team. 

Position Description

The Core Thermal-Hydraulics team at Oklo is responsible for analyzing fluid flow and heat transfer within a reactor core. The work includes engineering analyses of thermal-fluid dynamics, clear and thorough documentation of the analyses, as well as interfacing with design teams. A engineer on the team will contribute to the development, qualification, and validation of methods for modeling coolant flow within reactor cores using one-dimensional models, intermediate-fidelity subchannel models, and high-fidelity computational fluid dynamics models.

Specific responsibilities may include:

• Modeling core thermal-hydraulic behavior using
• subchannel codes such as DASSH, MOOSE-Subchannel, or COBRA-TF
• one-dimensional systems codes such as SAS4A/SASSYS-1 or RELAP
• first principles approaches and in-house flow network models
• 3-D computational fluid dynamics
• Developing and documenting methods to analyze core thermal-hydraulic behavior at steady-state and during transients
• Automation, verification, and validation of modeling and simulation tools in support of analyses
• Collaborating cross-functionally to define design requirements, and providing technical feedback to quick-iterating design teams

Minimum Qualifications

• Bachelors, Masters, or PhD in a technical field, such as nuclear, mechanical, or aerospace engineering
• Proficiency with thermal fluids (thermal-hydraulics) analysis methods and first principles
• Able to write clear and concise documentation
• Experience with
  • low-fidelity and intermediate-fidelity (e.g., porous body and correlation-based) models for heat transfer and fluid flow
  • numerical methods and software development for heat transfer and fluid flow problems
  • data processing (e.g., pre-processing, post-processing, scripting)

Bonus Qualifications

• Fluency with Python
• Demonstrated success in qualification and validation of analyses
• Experience with
  • CI/CD computing environments
  • reactor systems codes (RELAP or similar)
  • subchannel analysis codes (COBRA-TF or similar)
  • high-fidelity computational fluid dynamics analysis

Competencies

We are looking for a Thermal Fluids Engineer that is:

• Willing and able to learn quickly
• Deeply skilled in analysis of heat transfer and fluid flow in confined geometries
• Eager to work on a dynamic team, receive constructive feedback, and grow with us
• Excited to think creatively, critically, and reflectively about the problems they are solving
• Familiar with the importance of high-quality documentation

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. Some travel to other sites is also required for this position. For the first two weeks of onboarding, employees are required to be in person at headquarters in Santa Clara, CA.

About Oklo compensation:

Salary: $80,000-$175,000

Oklo offers flexible time off, equity, competitive pay, 401k, health insurance, FSA, flexible work hours, and other benefits.

We are looking to fill this position immediately!

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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.