{"id":853056,"url":"https://alion.io/job/radiantnuclear-principal-nuclear-engineer","title":"Principal 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":0.269,"repost_share":0,"time_to_fill_p50_days":71,"computed_at":"2026-11-04T06:34:25Z"}},"role":"Energy","role_family":"Energy","seniority":"lead","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":195713,"max":262500,"currency":"USD","period":"year","gross":null,"usd_annual":262500},"salary_estimate":null,"experience_years_min":12,"visa_sponsorship":false,"relocation_package":false,"has_equity":true,"technologies":[{"name":"MCNP","optional":false},{"name":"Verification & Validation","optional":false},{"name":"NRC Licensing","optional":true},{"name":"Python","optional":true}],"status":"live","first_seen_at":"2026-09-11T23:39:20Z","employer_posted_date":"2026-09-11","last_verified_at":"2026-11-04T18:21:21Z","board_verified":true,"closed_at":null,"days_open":53,"trust":{"level":"ok","repost_count":null,"flags":[],"days_open":53},"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 Principal Nuclear Engineer to lead the interdisciplinary nuclear engineering work supporting Kaleidos. This role combines people leadership with hands-on technical ownership across core physics, neutron and radiation transport, shielding, activation and dose, thermal-hydraulics, safety analysis, instrumentation and controls, operations, and regulatory evaluations. You will guide work from requirements and early design trades through analysis, verification and validation, testing, and regulatory documentation. The ideal candidate brings deep expertise in neutron transport and Monte Carlo methods, along with the judgment to translate complex analysis into practical reactor design and operational decisions.\nResponsibilities & Duties\nLead an interdisciplinary team working across reactor physics, core performance, shielding, dose and activation, thermal-hydraulics, safety analysis, I&C, and operations.\n\nEstablish technical priorities, project plans, resource needs, and clear ownership across the nuclear engineering organization.\n\nServe as a technical authority for neutron and radiation transport and Monte Carlo simulation methods.\n\nOwn nuclear engineering projects from requirements capture and design iteration through model development, analysis, technical review, and final documentation.\n\nGuide analyses of criticality, reactivity control, shutdown margin, power distribution, depletion, temperature feedback, radiation transport, dose, activation, and shielding performance.\n\nTranslate analytical results into actionable requirements and design decisions affecting the core, shielding, control systems, instrumentation, fluid systems, and structures.\n\nEstablish technically rigorous practices for model verification and validation, peer review, configuration control, uncertainty evaluation, and documentation.\n\nCollaborate with reactor systems, thermal, mechanical, electrical, test, operations, safety, and regulatory teams to resolve multidisciplinary design challenges.\n\nTranslate nuclear standards and regulatory requirements into analysis plans, design criteria, calculation packages, and verification activities.\n\nSupport reactor testing and startup by defining analysis needs, instrumentation requirements, acceptance criteria, and methods for comparing predicted and measured performance.\n\nIdentify technical risks, drive complex problems through closure, and communicate decisions and recommendations to engineering teams and company leadership.\n\nMentor engineers through technical guidance, actionable feedback, and regular coaching.\n\nRequired Qualifications & Skills\nBachelor’s degree in nuclear engineering or a related technical discipline from an accredited institution.\n\n12+ years of relevant nuclear engineering experience across reactor design, analysis, testing, licensing, safety, or operations.\n\nDemonstrated experience leading complex nuclear engineering projects and multidisciplinary technical teams.\n\nExperience hiring, managing, mentoring, or technically leading nuclear engineers.\n\nDeep knowledge of neutron transport theory, Monte Carlo simulation methods, nuclear data, and statistical convergence.\n\nProfessional experience developing and applying MCNP, OpenMC, or comparable neutron and radiation transport models.\n\nStrong understanding of criticality, reactivity coefficients, depletion, power distribution, shutdown margin, radiation transport, and uncertainty analysis.\n\nExperience translating analysis into reactor design decisions, technical requirements, safety conclusions, or regulatory documentation.\n\nFamiliarity with model verification and validation, configuration control, peer review, and nuclear software quality practices.\n\nStrong written and verbal communication skills, including the ability to explain complex analyses, assumptions, uncertainties, and technical conclusions.\n\nPreferred Qualifications & Skills\nMaster’s degree or Ph.D. in nuclear engineering or a related discipline.\n\nExperience with high-temperature gas-cooled reactors, microreactors, advanced reactors, or first-of-a-kind nuclear systems.\n\nExperience with SCALE, Serpent, Shift, Griffin, MOOSE-based applications, or similar analysis tools.\n\nProficiency with Python or another language used for simulation automation and data post-processing.\n\nExperience with coupled neutronics and thermal-hydraulics or other multiphysics analyses.\n\nFamiliarity with DOE authorization, NRC licensing, nuclear codes and standards, or regulatory safety analysis.\n\nExperience supporting reactor testing, commissioning, startup, or operational readiness.\n\nAdditional Requirements\nWilling to support extended hours when needed to meet critical program milestones.\n\nMust work 100% onsite at Radiant’s El Segundo headquarters.\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. Any job offer made will be contingent upon the applicant’s capacity to serve in compliance with U.S. export controls.","description_format":"text","description_chars":7726,"description_truncated":false,"requirements":{"experience_years_min":12,"management_years_min":null,"team_size_min":null,"manages_managers":false,"education":{"level":"bachelor","optional":false},"security_clearance":false,"languages":[]},"benefits":["Equity","Parental leave"],"hiring_locations":[],"hiring_excludes":[],"relocation_offered":false,"industries":["Nuclear Energy"],"lifecycle":[{"event":"open","at":"2026-09-13T04:41:29Z"}],"visa":[],"liveness":{"score":62,"band":"ok","label":"Likely open","p_open":1,"p_active":0.824,"p_room":0.75,"age_days":53,"expected_fill_days":71,"reasons":["conf:2","win:late"],"computed_at":"2026-11-04T06:34:25Z"},"pay":{"stated_usd_annual":262500,"is_top_pay":true},"html_url":"https://alion.io/job/radiantnuclear-principal-nuclear-engineer","json_url":"https://alion.io/job/radiantnuclear-principal-nuclear-engineer.json","meta":{"generated_at":"2026-11-04T18:30:01Z","cache_seconds":300,"methodology":"https://alion.io/methodology","terms":"https://alion.io/terms","contact":"https://alion.io/contact","api":"https://alion.io/developers","about":"Alion is a live layer of people, companies and AI agents: who they are, whether they are real and active right now, what they do and how to work with them, readable by people and by agents and paid per call.","catalog":"https://alion.io/catalog.json","usage":{"tier":"crawler_verified","counted_by":"address","units_charged":1,"used_today":28463,"day_limit":null,"remaining_today":null,"minute_limit":300,"resets_at":"2026-11-05T00:00:00Z"}},"offers":[{"id":"company.slices","title":"One company in depth, by slice","status":"live","price":{"credits":0.02,"usd":0.002,"plus_per_slice":{"credits":0.05,"usd":0.005}},"unit":"per company, plus each slice with data","note":"the employer in depth","call":{"mcp_tool":"get_company","arguments":{"id":690814},"rest":"https://alion.io/mcp/rest/get_company?id=690814"},"human":"https://alion.io/catalog?offer=company.slices&for=job%2Fradiantnuclear-principal-nuclear-engineer"},{"id":"market.stats","title":"A market slice: pay, demand and time to fill","status":"live","price":{"credits":1,"usd":0.1},"unit":"per slice","note":"pay, demand and time to fill for this role and place","call":{"mcp_tool":"market_stats"},"human":"https://alion.io/catalog?offer=market.stats&for=job%2Fradiantnuclear-principal-nuclear-engineer"},{"id":"job.search","title":"Open jobs by role, technology, place, pay and visa","status":"live","price":{"credits":0.02,"usd":0.002},"unit":"per posting in a list","note":"similar open postings","call":{"mcp_tool":"search_jobs"},"human":"https://alion.io/catalog?offer=job.search&for=job%2Fradiantnuclear-principal-nuclear-engineer"},{"id":"company.verify","title":"Is this company real and active right now","status":"pilot","price":null,"unit":"per company","request":{"url":"https://alion.io/catalog/request","method":"POST","body":"{\"offer\": \"company.verify\", \"for\": \"job/radiantnuclear-principal-nuclear-engineer\", \"note\": \"what you need it for\"}"},"human":"https://alion.io/catalog?offer=company.verify&for=job%2Fradiantnuclear-principal-nuclear-engineer"}],"agent":{"mcp":"https://alion.io/mcp/jobs","mcp_open":"https://alion.io/mcp/open","next":[{"tool":"get_job","arguments":{"id":853056}},{"tool":"search_jobs","arguments":{"company":"radiantnuclear.com","detail":"compact"}},{"tool":"match_people","arguments":{"job_id":853056},"note":"people open to offers who fit this vacancy"}],"note":"The same data through MCP tools: https://alion.io/mcp/open needs no sign-in (compact searches, postings, people); https://alion.io/mcp with an Alion account has everything. Docs: https://alion.io/developers"}}