{"id":853108,"url":"https://alion.io/job/radiantnuclear-senior-nuclear-engineer","title":"Senior Nuclear Engineer","company":{"id":690814,"name":"Radiant Nuclear","domain":"radiantnuclear.com","url":"https://alion.io/company/radiantnuclear","size_band":"201-500","is_staffing_agency":false,"employer_type":"direct","is_intermediary":false,"listed_via":null,"ats_vendor":"Ashby","truth_index":{"grade":"A","score":88,"open_postings":26,"ghost_share":0,"stale_share":0.5,"repost_share":0,"time_to_fill_p50_days":53,"computed_at":"2026-11-02T06:13:15Z"}},"role":"Energy","role_family":"Energy","seniority":"senior","employment_type":"full_time","work_mode":"on_site","remote_scope":null,"remote_scope_basis":null,"remote_working_hours":null,"hiring_geo_confidence":"structured","locations":["El Segundo, United States"],"countries":["US"],"hiring_countries":[],"hiring_countries_total":0,"salary":{"min":150025,"max":211838,"currency":"USD","period":"year","gross":null,"usd_annual":211838},"salary_estimate":null,"experience_years_min":4,"visa_sponsorship":false,"relocation_package":false,"has_equity":true,"technologies":[{"name":"Digital Twin","optional":false},{"name":"MCNP","optional":false},{"name":"Python","optional":false},{"name":"Verification & Validation","optional":false}],"status":"live","first_seen_at":"2026-08-07T21:48:47Z","employer_posted_date":"2026-08-07","last_verified_at":"2026-11-02T05:59:53Z","board_verified":true,"closed_at":null,"days_open":86,"trust":{"level":"ok","repost_count":null,"flags":[],"days_open":86},"description":"About Radiant\nRadiant is an El Segundo, CA-based startup building the world’s first mass-produced, portable nuclear microreactors. The company’s first reactor, Kaleidos, is a 1-megawatt, fail-safe microreactor that can be transported anywhere power is needed and run for up to 5 years without refueling. Portable nuclear power with rapid-deploy capability can replace similar-sized diesel generators and provide critical asset support for hospitals, data centers, remote sites, and military bases. Radiant’s unique, practical approach to nuclear development leverages modern software engineering to rapidly deliver safe, factory-built microreactors that use existing, well-qualified materials. Founded in 2020, Radiant is on track to test its first reactor at the Idaho National Laboratory this summer, with initial customer deliveries beginning in 2028.\nAbout the Role\nRadiant is seeking a driven Senior Nuclear Engineer to join our team! You will own modeling methods and reactor physics calculations of neutronics parameters such as reactivity, kinetics parameters, and energy deposition distributions used within our cutting-edge custom-made Digital Twin simulation software. You’ll be responsible for assessing conservatism and verifying assumptions within the modeling methods and documenting all results. Because these methods are pivotal in the safety analysis, you will play a key role in the commercialization of the first mass-produced nuclear reactor.\nResponsibilities & Duties: \nOwn modeling methods of core neutronics and reactor physics calculations supporting Radiant’s transient safety analyses.\n\nPerform calculations of energy deposition distributions, reactivity coefficients, kinetics parameters, and control blade worths to input into Digital Twin models.\n\nVerify assumptions and assess conservatism of neutronics models.\n\nDocument methods for both technical and non-technical audiences.\n\nAssist in Verification & Validation (V&V) efforts for the Digital Twin.\n\nReview and support other nuclear analyses across the company in reactor physics, shielding, and radiation detection.\n\nRequired Qualifications & Skills:\nBachelor’s degree in nuclear engineering or a similar field from an accredited institution.\n\n4+ years of experience with Monte Carlo nuclear engineering software such as OpenMC, MCNP, Serpent, SCALE, etc.\n\nExperience documenting analysis methods and assumptions.\n\nStrong programming skills in any language, preferably Python.\n\nDesired Qualifications & Skills:\nKnowledge and experience in reactor kinetics.\n\nBasic knowledge of thermal hydraulic principles.\n\nExperience communicating and distilling information with cross-functional teams.\n\nDriven, self-motivated, and takes ownership of work end to end.\n\nAdditional Requirements:\nMust be willing to work extended hours and weekends as necessary to accomplish our mission.\n\nMust work 100% onsite at El Segundo HQ.\n\nBenefits and Perks\nStock: Substantial incentive stock plan for all full-time employees.\n\nMedical: 100% up to base silver level plan for employee + 50% dependents, offers up to Platinum plans.\n\nOne Medical: Sponsored memberships for employees and their dependents.\n\nVision: 100% top tier plan coverage + 50% for dependents.\n\nDental: 100% top tier plan coverage, orthodontia extra, 50% for dependents.\n\nVoluntary life, accident, hospital, critical illness, commuter and FSA/HSA are offered as employee contributed benefits.\n\n8-weeks of paid parental leave for all parents. Additional paid pregnancy leave for CA employees.\n\nDaily catered lunch. Free snacks and drinks.\n\nFlexible PTO policy. Remote workday allocation.\n\nCompany and team-bonding events, happy hours and in-person camaraderie.\n\nBeautiful El Segundo headquarters close to the Pacific Ocean.\n\nTotal Compensation and Benefits\nRadiant compensates people for impact and invests in those who continue to raise the bar. Radiant’s new hire compensation package includes base salary, substantial equity grants, and comprehensive health benefits. Total compensation and level are determined through a rigorous evaluation of interview performance, experience, education, and qualifications, and are designed to support continued growth as scope, responsibility, and impact expand at Radiant.\nThe best of today’s advanced reactor builders don’t wait for job postings. They join the winning team. If that’s you, contact us directly for immediate opportunities: .\nWe are an equal opportunity employer and all qualified applicants will receive consideration for employment without regard to race, color, religion, sex, sexual orientation, gender identity or expression, pregnancy, age, national origin, disability status, genetic information, protected veteran status, or any other characteristic protected by law.\nThis position involves access to technology that is subject to U.S. export controls. 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