Senior Nuclear Engineer, Neutronics

About HelionWe are a fusion power company based in Everett, WA, with the mission to build the world's first fusion power plant, enabling a future with unlimited clean electricity. Our vision is a world with clean, reliable, and affordable energy for everyone. Since Helion's founding in 2013, we have raised over $600 million from investors such as Sam Altman, Mithril, and Capricorn Investment Group to propel us forward. Our last prototype, Trenta, completed 10,000 high-power pulses and reached plasma temperatures of 100 million degrees Celsius (9 keV). Now we are working toward Polaris, which will be the first machine to demonstrate electricity from fusion, making this a great time to join Helion! Bring your skills, experiences, and determination to make a difference in the world. Together, we can make a future with unlimited clean electricity from fusion a reality.  What You Will Be Doing:We are seeking an experienced Senior Nuclear Engineer to support Helion’s efforts in nuclear engineering needs. This includes supporting the fusion neutronics, shielding, activation analysis, and diagnostics support. You will prepare reports and coordinate with cross-functional teams to integrate neutron diagnostics, support radiation safety, and ensure compliance with regulatory requirements. This is an onsite role at our Everett locations, and you will be reporting directly to the Nuclear Engineering Manager.You Will:Conduct comprehensive radiation transport, shielding, and activation simulations for Helion fusion devicesCreate the workflow to estimate dose, decay heat during operation, and shutdown conditions for Helion fusion generatorsUtilize variance reduction and other methods to reduce computation run timeCollaborate with Helion Science and Engineering teams throughout the design, development, and deployment phases of Helion fusion devicesCommunicate technical results and findings with accuracy and rigor to diverse audiences by preparing reports, presentations, and GUIsRequired Skills:5+ years of experience in nuclear engineering, with a focus of neutronics, shielding, and activation analysis of nuclear systemsNuclear Physics Expertise with strong knowledge of neutron and photon interactions, cross sections, attenuation, decay, and radiation typesMonte Carlo Radiation Transport codes hands-on experience (e.g., Attila, MCNP, OpenMC, Geant4, FLUKA)Experience with activation analysis (e.g., FISPACT, CINDER) and CAD to MC conversion (e.g., DAGMC, GEOUNED)Proficient in Python, MATLAB, or C++ for data analysis and HPC cluster job submissionsProven ability to validate simulations against experimental data#LI-Onsite #LI-KL1Compensation and BenefitsAt Helion, we are committed to fostering a fair and equitable environment in every aspect of our operations, including compensation. We ensure all our roles are competitively benchmarked and our total compensation package includes a base salary, comprehensive benefits, and equity grants, giving you a true stake in Helion's success. Final compensation is determined through a holistic evaluation of your experience, qualifications, and our commitment to maintaining internal equity, ensuring fairness and transparency across our teams.This is an exempt salaried role.Annual Base Pay$130,000—$190,000 USDBenefitsOur total compensation package includes benefits, including but not limited to: Medical, Dental, and Vision plans for employees and their families 31 Days of PTO (21 vacation days and 10 sick days) 10 Paid holidays, plus company-wide winter break Up to 5% employer 401(k) match Short term disability, long term disability, and life insurance Paid parental leave and support (up to 16 weeks) Annual wellness stipend  NOTE: Underrepresented people are less likely to apply unless they meet 100% of the job's requirements. We believe in hiring people, not checklists, and encourage you to apply even if you do not check all of the boxes. If this job isn't the one, we have many other openings that may be a fit.All qualified applicants will receive consideration for employment without regard to race, color, religion, sex, disability, age, sexual orientation, gender identity, national origin, veteran status, or genetic information. If we reach out to you to begin an interview process, we will also ask if you require any reasonable accommodation at that time.