Senior Network Security Engineer

About the role

ABOUT RADIANT Radiant 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. SENIOR NETWORK SECURITY ENGINEER Radiant is looking for a hands-on Senior Network Security Engineer to own our network infrastructure as we scale. You will be the primary architect and administrator for our network security fabric, bridging our on-premise locations with our growing cloud footprint. This is not a "maintain the lights" role — you will lead critical infrastructure initiatives immediately, including migrating core services to a colocation facility (Equinix) and redesigning our site-to-site connectivity using Fortinet SD-WAN. Responsibilities and Duties Lead the design and implementation of moving on-premise servers and network gear to a secure Equinix datacenter cage; ensure high-availability connectivity between the datacenter, HQ, and warehouse sites. Serve as the Subject Matter Expert (SME) for our Fortinet stack — manage and optimize FortiGate firewalls (HA pairs), FortiSwitch, and FortiAP. Design and manage secure connectivity (VPN/Direct Connect) between our physical infrastructure and cloud environments (AWS/Azure) Manage complex routing protocols (BGP, OSPF) to ensure seamless failover and optimal traffic paths across our SD-WAN fabric. Implement Zero Trust principles, manage VLAN segmentation, and monitor threats using FortiAnalyzer or similar tools. Required Qualifications and Skills: 5+ years of network engineering experience with a heavy focus on security and hybrid environments Deep, hands-on experience with FortiOS — comfortable configuring HA clusters, VDOMs, and SD-WAN rules from scratch (NSE 7 certification is a strong plus) Solid understanding of cloud networking constructs, including VPCs, VNETs, Transit Gateways, and Security Groups Willingness to be hands-on with hardware when necessary — racking, cabling, and physically configuring devices in the datacenter Ability to troubleshoot complex connectivity issues spanning the physical layer, ISP routing, and cloud firewalls Desired Qualifications and Skills: Experience connecting distributed sites (e.g., warehouses, remote offices) via SD-WAN Background in regulated or high-security industries Experience with network automation tools such as Ansible, Terraform, or Python Work Environment Must work 100% onsite at El Segundo HQ. Must be willing to work extended hours and weekends as necessary to accomplish our mission. Benefits and Perks Stock: Substantial incentive stock plan for all full-time employees. Medical: 100% up to base silver level plan for employee + 50% dependents, offers up to Platinum plans. One Medical: Sponsored memberships for employees and their dependents. Vision: 100% top tier plan coverage + 50% for dependents. Dental: 100% top tier plan coverage, orthodontia extra, 50% for dependents. Voluntary life, accident, hospital, critical illness, commuter and FSA/HSA are offered as employee contributed benefits. 8-weeks of paid parental leave for all parents. Additional paid pregnancy leave for CA employees. Daily catered lunch. Free snacks and drinks. Flexible PTO policy. Remote workday allocation. Company and team-bonding events, happy hours and in-person camaraderie. Beautiful El Segundo headquarters close to the Pacific Ocean. Total Compensation and Benefits Radiant 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. The 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: [email protected] . We 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. Unfortunately, we are unable to provide visa sponsorship at this time. This 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.