Senior-Level Mechanical Engineer

We are seeking an experienced, collaborative engineering professional who excels at keeping teams aligned, stakeholders engaged, and projects delivered on schedule and within budget. Based in Oak Ridge, Tennessee, this role will provide design engineering support for large-scale, complex projects for a diverse portfolio of clients that includes the U.S. Department of Energy, the National Nuclear Security Administration (NNSA), and commercial nuclear companies. The successful candidate will provide leadership across capital projects involving nuclear infrastructure, advanced reactor deployment, fuel cycle facilities, and mission-critical national security programs while ensuring the highest standards of safety, quality, regulatory compliance, and financial performance. This is an opportunity to play a key role in delivering projects that strengthen America's nuclear security mission, support the deployment of next-generation nuclear technologies, and expand the nation's commercial nuclear capabilities. Amentum Nuclear Projects is a Tier 1 services provider supporting the U.S. Department of Energy’s, the National Nuclear Security Administration (NNSA), and leading commercial nuclear companies. We deliver safe, innovative, and mission-focused solutions at some of the nation's most complex nuclear security, production, and advanced nuclear technology facilities. Our core capabilities include: Program and project management NNSA capital line-item projects Naval Reactors facility designs Nuclear facility modernization and construction management Nuclear material and fuel cycle management Technical consulting and owner's engineering Engineering, procurement, and construction management (EPCM) projects Engineering and project delivery for advanced reactor programs, including Small Modular Reactors (SMRs) and advanced reactor technologies Engineering support for commercial nuclear fuel fabrication facilities Engineering and project execution for nuclear fuel reprocessing and related fuel cycle infrastructure Job Description As a senior-level mechanical engineer, you will serve as a technical leader responsible for the design, coordination, and delivery of building mechanical systems for industrial and government facilities. This role includes oversight of HVAC, plumbing, and piping system designs; leadership of mechanical engineering teams; and accountability for technical quality and compliance throughout the project lifecycle. The successful candidate will work closely with project management, discipline leads, and clients to deliver fully coordinated, code‑compliant, and high‑quality engineering solutions in accordance with Amentum’s established quality procedures. Key Responsibilities: Lead and oversee the design of HVAC, plumbing, and piping systems, including B31.3 process piping Serve as technical authority for mechanical system design within assigned project scope Review, approve, and check engineering calculations, layouts, specifications, and drawings Apply advanced engineering judgment to resolve complex design issues Support project planning by assisting with: Scope definition Equipment sizing Schedule development Budget control for mechanical design activities Coordinate mechanical designs with structural, electrical, architectural, and process disciplines Apply applicable codes, standards, and procedures (e.g., IMC, ASHRAE, NFPA, ASME) Interface with clients and other stakeholders as a senior technical contributor Provide senior‑level support during procurement and construction phases, including review and resolve RFIs, submittals, and field issues Mentor and guide engineers and designers on applicable codes, standards, and best practices Ensure all work under your technical responsibility complies with Amentum’s engineering and quality procedures Basic Qualifications: B.S. Mechanical Engineering from an ABET accredited engineering program 15+ years in industrial/government design of Mechanical, HVAC, Plumbing Systems, and related mechanical building systems Demonstrated experience delivering projects from concept through detailed design completion Proven ability to lead teams of engineers and designers within budget and schedule constraints Proficiency with discipline-specific tools such as: Carrier HAP, Trane TRACE, PipeFlo, AutoCAD, MicroStation, etc. Thorough knowledge of applicable codes & standards (International Mechanical Code, NFPA, ASHRAE, etc.) Professional Engineer (PE) license required USA citizenship is required Preferred Qualifications: In addition to the Basic Qualifications the ideal candidate might also have: Prior nuclear, DOE, or high‑hazard facility design experience Experience working under a formal quality program (ISO 9001, NQA 1) Strong leadership, communication, and technical mentoring skills Demonstrated attention to detail and commitment to technical excellence Proficiency with Microsoft Office (Excel, Word, Outlook) Work Environment: Primarily office-based work in a secure engineering environment   Amentum office location is preferred; hybrid or remote work may be available by prior agreement based on role and project requirements Occasional exposure to industrial facilities, which may include elevated noise levels, hazardous materials, or controlled areas Site visits may be required Physical Requirements:   Ability to sit or stand for extended periods Ability to lift up to 35 lbs occasionally Vision correctable to 20/20 Ability to read and use computer‑aided design software effectively Appropriate PPE and training will be provided as required   Compliance & Eligibility Requirements: U.S. Citizenship required (no dual citizenship) Valid driver's license is required Ability to obtain and maintain a security clearance Ability to pass pre-employment background investigation and drug screening Willingness to work overtime or outside normal hours as needed Professional appearance appropr