Senior System Administrator

Radiant is an El Segundo CA-based startup building the worlds first mass-produced portable nuclear microreactors. The companys 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. Radiants 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.

Radiant is seeking a Senior Systems Administrator to own the systems that keep the company running day-to-day within Microsoft 365 GCC High. Youll 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. Youll 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.

• Own Microsoft 365 GCC High: Exchange Online SharePoint Teams and the tenant configuration underneath them; be the authority on whats 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 CUI

• Own 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 DevOps 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

• Bachelors 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 nobodys too senior to help the person at their desk

• Purview depth: DLP sensitivity labeling retention or eDiscovery

• CMMC or NIST 800-171 exposure; leading an assessment is not required

• Stood 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)

• Written and maintained PowerShell modules other people use not just scripts

• Deployed Box Slack or comparable platforms into a regulated environment and handled the data boundary questions

• Must be willing to work extended hours and weekends as necessary to accomplish our mission.

• Must work 100% onsite at El Segundo HQ.

• 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. Radiants 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 todays advanced reactor builders dont wait for job postings. They join the winning team. If thats you contact us directly for immediate opportunities: .

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.

This position involves access to technology that is subject to U.S. export controls. Any job offer made will be contingent upon the applicants capacity to serve in compliance with U.S. export controls.

Required Experience:

Senior IC