Senior System Administrator

About Radiant Radiant is an El Segundo, CA-based startup building the world’s first mass-produced, portable nuclear microreactors. Rising energy demand is straining the U.S. grid and driving up utility costs, emissions, and interconnection backlogs. Radiant decentralizes energy, producing power close to where it’s used. Its first reactor, Kaleidos, is a factory-built, 1-megawatt, fail-safe microreactor that can be transported by land, sea, or air and runs up to 5 years without refueling.

Deployed locally without a decade-long build or permitting fight, Kaleidos provides independent power for critical infrastructure like military bases, data centers, hospitals, and remote sites. Founded in 2020, Radiant is under contract to deliver power to the U.S. Army, Air Force, Navy, and has pre-order agreements with Equinix, with deployments beginning in 2028.

About the Role:

Radiant is seeking a Senior Systems Administrator to own the systems that keep the company running day-to-day within Microsoft 365 GCC High. You'll own the tenant, build our identity and access automation from the ground up in an Entra-native environment with no on-prem Active Directory or Group Policy, and manage the endpoint, email security, and SaaS infrastructure the business runs on.

You'll implement and evidence the technical controls behind our CMMC assessment as part of the normal job, not a detour. This is a high-ownership seat in an interdisciplinary environment, advancing milestones toward commercializing the first mass-produced nuclear reactor.

Responsibilities and Duties:

Own Microsoft 365 GCC High:
Exchange Online, SharePoint, Teams, and the tenant configuration underneath them; be the authority on what's possible in this cloud and what has to be built in-house

Own Entra end-to-end: conditional access, privileged access, app registrations, and single sign-on Build the IAM automation layer, the centerpiece of the role: joiner/mover/leaver lifecycle, entitlements driven by HR data, provisioning through Graph and SCIM, and access reviews that run themselves

Own Windows and endpoint management through Intune, Autopilot, compliance policy, and update rings across the fleet, with no Group Policy underneath

Own email security and information protection:
Defender for Office, mail flow and anti-phishing posture, and Purview for DLP, labeling, and retention in an environment handling CUIOwn SaaS administration and integration across the business application portfolio, including Box and Slack; some running today, some a project waiting for an owner

Own the workloads, services, and licensing infrastructure running in AWS, in constant contact with the IT Dev Ops engineer who owns the account layer

Take new platform projects from idea to deployed, integrated, and documented

Implement and evidence the technical controls in these areas for the CMMC assessment ahead, as normal work rather than a detour

Required

Qualifications and Skills:

Bachelor's degree in Information Technology, Computer Engineering, Cybersecurity, or a similar field (4 years of work experience in lieu of a degree)7+ years administering and engineering production systems

Deep, hands-on experience across the responsibilities above: GCC High tenant administration, Entra, self-built IAM automation, Intune without Group Policy, email security and Purview, and SaaS/AWS administration

Solid networking fundamentals: VLANs, routing, firewall policy, DNS/DHCP, VPN, wireless

Treats compliance control implementation and evidence collection as normal work Service is the job; tier-1 handles day-to-day support, but nobody's too senior to help the person at their desk Desired

Qualifications and Skills:

Purview depth: DLP, sensitivity labeling, retention, or eDiscoveryCMMC or NIST…