Mechanical Engineer – High-Temperature Stress Analysis

ZettaJoule, Inc.; Houston (TX); Remote; USD 120,000 - 180,000; Full time

Benefits offered by this job

Flexible hours

Remote options

Health/Life/Disability benefits

Paid vacation

Job summary

ZettaJoule, Inc. in Houston, TX or remote is seeking a Mechanical Engineer to perform elevated-temperature stress analyses for HTGR components and lead FEA-based code certification work. You will develop nonlinear models, verify materials data, and document results for ASME design reports.

Required: BS in Mechanical or Nuclear Engineering, 8+ years in stress analysis, and strong ANSYS/Abaqus skills; PE license and regulatory experience are a plus.

Qualifications

• Minimum 8 years of experience in stress analysis of pressure-retaining components.
• Experience with elevated-temperature design and ASME Section III design-by-analysis rules.
• Proficiency in nonlinear FE analysis and nuclear QA processes.

Responsibilities

• Perform elevated-temperature stress analysis of HTGR class components to ASME III, Div. 5 compliance.
• Develop nonlinear FE models (thermal-structural, creep) and document results.
• Coordinate with multiple engineering teams to define loads and design specs.
• Evaluate creep-fatigue, ratcheting, and weld/discontinuity effects under time-dependent loading.
• Manage analysis vendors and perform independent review under nuclear QA.

Skills

Finite element analysis

Nonlinear analysis

Python scripting

Education

BS in Mechanical Engineering

BS in Nuclear Engineering

Advanced degree preferred

Tools

ANSYS

Abaqus

Job description

Mechanical Engineer – High-Temperature Stress Analysis

Location: Houston, TX or Remote

Employment Type: Full Time

Reports To: Director, Core Design

About Us

We are a next-generation nuclear technology startup pioneering the commercialization of High-Temperature Gas-cooled Reactors (HTGRs) - a proven, safe, and transformative technology for delivering ultra-high-temperature heat and enabling a carbon-neutral future.

Our mission is to deploy the world’s first global fleet of Advanced Modular Reactors, redefining how clean energy powers industries, communities, and economies.

As a fast-growing company in its early stage, every team member — whether in engineering, program management, partnerships, operations, or business development — plays a direct role in shaping our technology, culture, and impact. You’ll join a collaborative, mission-driven team of internationally recognized experts and innovators working together to bring advanced nuclear energy to the world.

The Role

The Mechanical Engineer, High-Temperature Stress Analysis will be a key contributor to ZettaJoule’s reactor design activities, responsible for the structural analysis and code qualification of metallic components operating at elevated temperature in our High-Temperature Gas-cooled Reactor (HTGR). Working at the intersection of design, materials, and licensing, this role performs and oversees design-by-analysis evaluations that demonstrate compliance with ASME Boiler & Pressure Vessel Code Section III, Division 5 (High Temperature Reactors), develops the analysis methods and calculation packages that support ASME Code certification, and works closely with Materials Engineering to ensure that material properties and design curves are applied correctly in creep and creep-fatigue evaluations. The role also supports the design of non-nuclear pressure equipment under ASME Section VIII.

Key Responsibilities

• Perform elevated-temperature stress analysis of HTGR Class A metallic components — reactor vessel, core support structures, heat exchangers, and hot gas ducting — to demonstrate compliance with ASME Section III, Division 5 (Subsection HB, Subpart B).
• Evaluate primary and secondary stress limits, strain accumulation (ratcheting), creep-fatigue damage, and creep buckling using Division 5 elastic, simplified inelastic, viscoplastic, and full inelastic design-by-analysis methods.
• Develop nonlinear finite element models (thermal-structural, plasticity, and creep) and the supporting methodologies, and document results in calculation packages and ASME Design Reports.
• Work with Thermal Hydraulics and Systems Engineering to define design loadings, service levels, and thermal transients, and support development of the ASME Design Specifications for high-temperature components.
• Apply material allowables, isochronous stress-strain curves, and creep-fatigue interaction data in collaboration with Materials Engineering, and identify data gaps that require additional testing or code cases.
• Evaluate weldments, bolted and flanged joints, and structural discontinuities under time-dependent loading, including weld strength reduction factors and local strain concentrations.
• Track and contribute to ASME Section III Division 5 code cases and technical positions, and support ZettaJoule’s engagement with code committees and regulators.
• Manage analysis vendors and perform independent review and verification of calculations, including qualification of FEA software and models under a nuclear quality assurance program (10 CFR 50 Appendix B / NQA-1).
• Perform design and analysis of non-nuclear pressure vessels and heat exchangers, such as balance-of-plant, process heat, and helium/gas handling equipment, in accordance with ASME Section VIII, Division 1 (design by rule) and Division 2 (design by analysis, Part 5).
• Prepare and review Section VIII design specifications, calculations, and U-1/U-2 manufacturer’s data report inputs, and work with fabricators and the Authorized Inspector to resolve design and Code compliance questions.
• Determine the appropriate Code of construction (Section III Division 5 or Section VIII) for each component based on function, safety classification, and regulatory requirements, and document the basis for that decision.
• Coordinate with Systems Engineering, Design, Materials, and Licensing teams to ensure structural analyses support the plant design basis and regulatory strategy.

What You'll Bring

• BS in Mechanical Engineering, Nuclear Engineering, or a related field required; advanced degree preferred.
• Minimum 8 years of experience in stress analysis of pressure-retaining components, including direct experience with elevated-temperature design (HTGR, sodium fast reactor, molten salt, or similar advanced reactor, or high-temperature power/process equipment).
• Demonstrated experience applying ASME Section III design-by-analysis rules, with working knowledge of Division 5 Subsection HB, Subpart B (HBB-T) for creep, creep-fatigue, and ratcheting evaluation.
• Proficiency in nonlinear finite element analysis (ANSYS, Abaqus, or equivalent) including plasticity, creep, and coupled thermal-structural modeling.
• Experience preparing formal calculation packages and stress reports under a nuclear quality assurance program.

U.S. citizenship or U.S. permanent resident status is required. Access to EAR-controlled and 10 CFR 810-governed nuclear technology requires authorization consistent with U.S. export control law.

Even Better

• Direct participation in ASME Boiler & Pressure Vessel Code committees or working groups (Section III Division 5).
• Experience with unified viscoplastic constitutive models or Division 5 inelastic analysis methods for alloys such as 316H, Alloy 800H, or Alloy 617.
• Professional Engineer (PE) license.
• Experience with ASME Code certification, including Design Specification and Design Report review by an Authorized Inspection Agency.
• Experience automating analysis and Code post-processing using Python or APDL scripting.

Why Work for Us

• Flexible hours & remote options.
• Health/Life/Disability benefits.
• Vacation/Sick leave.
• Work alongside internationally recognized experts shaping the future of nuclear energy.

EEO Statement

ZettaJoule is an Equal Employment Opportunity employer committed to diversity and inclusion.