Senior Mechanical Design Engineer - Reactor Module

Thanks for your interest in Oklo! We are searching for an experienced Mechanical Design Engineer to join our team. We are looking to fill this position immediately. Level (Engineer III/Senior) will be determined by experience. Position Description As a Senior Mechanical Design Engineer at Oklo, you will play a central role in designing the critical hardware that enables our advanced fast reactors to operate safely and reliably. This includes technical ownership of large, multi-component weldments and assemblies that comprise the reactor module within our Aurora powerhouses—ranging from the reactor vessel to various internal support structures and primary coolant flow elements. You will be responsible for advancing these components from conceptual design through detailed design and fabrication readiness, ensuring that every element is engineered for performance, manufacturability, industrial Code compliance, and integration into Oklo’s broader reactor system. Your work will require deep engagement with cross-functional teams including structural analysts, systems engineers, materials experts, and external design and fabrication partners. This is a high-responsibility role at the heart of our flagship product. Success in this position requires producing quality mechanical solutions in a fast-paced, startup environment where technical excellence and a collaborative mindset are equally valued. Specific responsibilities may include: Develop and own the design of complex mechanical components and subsystems within the reactor module Collaborate cross-functionally with other engineering teams to define design and functional requirements, ensuring compliance with safety regulations and industry codes standards (e.g., ASME BPVC) Use CAD tools to translate functional requirements into robust designs that meet structural, thermal, and integration constraints Conduct and participate in design reviews, providing and receiving technical feedback Rigorously evaluate mechanical designs to identify deficiencies and proactively propose and implement solutions Generate and maintain detailed 3D CAD models, 2D drawings, and bills of materials using controlled processes in PDM/PLM systems Coordinate closely with analysis teams to guide and interpret thermal, structural, fatigue, and safety analyses in support of design validation Perform detailed manufacturability reviews, tolerance studies, and DFM/DFA assessments to prepare components for fabrication and assembly Create and maintain clear, well-written engineering documentation, including design rationales, functional requirements, reviews of historical designs, and detailed explanations of system architecture and performance Work closely with fabrication partners to refine designs for cost-effective and practical production Manage engagements with consultants and engineering firms to support high-fidelity analysis, ASME code compliance, and design maturity advancement Contribute to continuous improvement of Oklo’s mechanical design processes, tools, and standards through feedback and development of best practices Minimum Qualifications: Bachelor’s or higher degree in Mechanical Engineering or a related engineering discipline 8+ years of industry experience in mechanical or structural design within sectors such as aerospace, automotive, energy, or industrial equipment Proficiency in 3D CAD modeling software (e.g., Siemens NX, CATIA, SolidWorks), including part modeling, large assemblies, and detailed drawings Experience with design control using PDM/PLM tools (e.g., Siemens Teamcenter, SolidWorks PDM, Windchill) Robust understanding of mechanical design principles, including DFM (Design for Manufacturability), DFA (Design for Assembly), and tolerance stack-up analysis Ability to interpret and produce engineering drawings that apply GD&T in line with ASME Y14.5 or similar standards Working knowledge of material selection (particularly metals), manufacturing methods, and fabrication techniques Demonstrated ability to collaborate on cross-functional teams, integrating feedback from analysis, manufacturing, and systems engineering Strong written and verbal communication skills, with the ability to clearly document and present engineering work Bonus Qualifications: Experience designing large structural weldments and mechanical joints Familiarity with the ASME Boiler and Pressure Vessel Code, particularly Sections III or VIII Background in designing components for high-integrity or safety-critical systems (e.g., nuclear, aerospace, defense, or heavy industry) Proven ability to lead hardware projects through the full development cycle—from concept and design to testing and production Comfortable working with external manufacturers and engineering consultants for fabrication and analysis support Knowledge of large scale fabrication techniques and transportation/handling of large components Understanding of thermal-mechanical analysis principles, with experience designing for high-temperature environments Basic knowledge of nuclear fission and radiation effects on materials and components Competencies We are looking for aSenior Mechanical Design Engineer that is: Passionate about clean energy Passionate about making advanced fission a reality Willing and able to learn quickly Knowledgeable about fast reactor design Eager to work on a dynamic team, receive constructive feedback, and grow with us Willing to think differently and do things in new ways Comfortable in a fast-paced, highly iterative startup environment Excited to think creatively, critically, and reflectively about the problems they are solving, while not leaning only on what has been done before Willing to propose novel and creative solutions to technical problems An excellent writer who can write in modern active voice, so make your cover letter compelling and write it well! 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…