RELAP-3D Code Developer and Analyst

As a pivotal member of Idaho National Laboratory's groundbreaking team, you'll push the boundaries of innovation by developing, testing, and refining cutting‑edge models that drive advancements in nuclear energy and beyond. Your expertise will shape the future of American energy security and technological leadership, building on INL's legacy of firsts and helping to secure critical infrastructure in a rapidly evolving world.

Working at the forefront of scientific discovery, you'll turn complex data into transformative insights, accelerating breakthroughs in energy, national security, and space exploration. Your contributions will directly support INL's mission to pioneer solutions that power the nation and protect its resilience. This is your chance to leave a lasting impact on history, alongside a team of brilliant scientists and engineers committed to shaping America's technological future.

INL is seeking a skilled and forward‑thinking Developer to join the Reactor Systems and Heat Transport Department as part of the RELAP5‑3D team in modernizing and expanding the capabilities of this critical nuclear safety analysis tool. This role involves improving code structure, readability, and maintainability, while also supporting the integration of new features and tools. The ideal candidate will be passionate about clean code practices and eager to contribute to a high‑impact nuclear safety software platform.

Additionally the developer will have the ability to perform thermal hydraulic analysis using RELAP5‑3D to determine areas of improvement.

• Update legacy Fortran code to modern standards, including restructuring.
• Break down complex routines into manageable components through refactoring and enhancing inline documentation.
• Program new code features, capabilities, and algorithms in Fortran as assigned and use existing and new write Python scripts.
• Apply the automated documentation systems to streamline manual creation and updates.
• Submit code updates as pull requests to the repository.
• Participate in the International RELAP5 User Group (IRUG) Meetings.
• Collaborate with analysts, stakeholders, and external partners to support ongoing development and integration efforts.
• Perform thermal hydraulic design/safety analysis using RELAP5‑3D or other thermal hydraulic tools.
• Participate in strategic planning and performance reviews to align development with long‑term goals.

• Level 3:
  Bachelor's and (5) years of relevant experience, Master's degree and (2) years of relevant experience or PhD and (2) years of relevant experience in Computer Science, Software Engineering, Mechanical Engineering, Nuclear Engineering, Mathematics or a related field.
• Level 4:
  Bachelor's, and (9) years of relevant experience OR Master's degree and (6) years of relevant experience or PhD and (4) years relevant experienc in Computer Science, Software Engineering, Mechanical Engineering, Nuclear Engineering, Mathematics or a related field.
• Proficiency in programming is required:
  • Proficiency will be used to assess level, ranging from proficiency with basic scripting languages like Python, matlab or java script to compiled languages, e.g., C++ or Fortran. Advanced proficiency in Fortran is a plus.
• Familiarity with software development tools and version control systems (e.g., Git).
  • Experience with git or other version control software is highly valued and will count towards the level determination
  • Must be good at typing and working with text‑based input.
  • Strong problem‑solving skills and attention to detail

• Experience with RELAP5‑3D or similar nuclear system codes.
• Exposure to DOE programs, nuclear reactor modeling, or simulator development.
• Experience with software refactoring, code modernization, and technical documentation.
• Knowledge of numerical methods and linear algebra

While performing the duties of this classification, the employee is frequently required to stand, walk, sit, stoop, kneel, bend, use hands to handle materials, manipulate tools, keyboard and type, reach with hands and arms, and operate job‑related equipment. The employee must…