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Radiant is building the world's first mass-produced, portable nuclear microreactors. The company's flagship product, Kaleidos, is a 1-megawatt, fail-safe microreactor designed for rapid deployment to hospitals, data centers, remote sites, and military bases. Founded in 2020 and headquartered in El Segundo, CA, Radiant is preparing for initial customer deliveries in 2028.
As Senior Systems Administrator, you will own the complete Microsoft 365 GCC High environment and identity infrastructure that powers the company's operations. This is a high-ownership, individual contributor role in an interdisciplinary environment supporting the commercialization of advanced nuclear technology.
Key responsibilities include:
- Full ownership of Microsoft 365 GCC High tenant, including Exchange Online, SharePoint, Teams, and underlying configuration; serve as the authority on cloud capabilities and in-house build requirements.
- End-to-end Entra administration: conditional access, privileged access management, app registrations, and single sign-on configuration.
- Design and build the IAM automation layer from scratch, including joiner/mover/leaver lifecycle automation, entitlements driven by HR data, provisioning via Microsoft Graph and SCIM, and self-service access reviews.
- Windows and endpoint management through Intune, Autopilot, compliance policies, and update rings across the fleet without Group Policy.
- Email security and information protection: Defender for Office, mail flow and anti-phishing posture, and Purview for DLP, sensitivity labeling, and retention in a CUI-handling environment.
- SaaS administration and integration across the business application portfolio, including Box and Slack.
- AWS workloads, services, and licensing infrastructure in coordination with the IT DevOps engineer.
- Implement and evidence technical controls for CMMC assessment as part of normal operations.
- Take new platform projects from concept through deployment, integration, and documentation.
This role requires 100% onsite presence at El Segundo headquarters and willingness to work extended hours and weekends as needed.
REQUIREMENTS:
- Bachelor's degree in Information Technology, Computer Engineering, Cybersecurity, or related field (or 4 years of work experience in lieu of degree).
- 7+ years administering and engineering production systems.
- Deep, hands-on experience across all responsibilities: GCC High tenant administration, Entra, self-built IAM automation, Intune without Group Policy, email security and Purview, SaaS and AWS administration.
- Solid networking fundamentals: VLANs, routing, firewall policy, DNS/DHCP, VPN, wireless.
- Treat compliance control implementation and evidence collection as normal work.
- Service-oriented mindset; willingness to support end users regardless of seniority level.
DESIRED QUALIFICATIONS:
- Purview depth in DLP, sensitivity labeling, retention, or eDiscovery.
- CMMC or NIST 800-171 exposure.
- Experience standing up identity governance tooling (Entra ID Governance, SailPoint, Okta Workflows, or equivalent).
- Automation experience with PowerShell, Python, Microsoft Graph, and infrastructure as code (Terraform, Bicep, or similar).
- Experience writing and maintaining PowerShell modules for organizational use.
- Experience deploying Box, Slack, or comparable platforms into regulated environments with data boundary expertise.
