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 failsafe microreactor that can be transported anywhere power is needed and run for up to five years without the need to refuel. 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 utilizes modern software engineering to rapidly achieve safe, factory-built microreactors that leverage existing, well-qualified materials. Founded in 2020, Radiant is on track to test its first reactor next year at the Idaho National Laboratory, with initial customer deliveries beginning in 2028.
Radiant is seeking an AP Manager to own our end-to-end accounts payable operations. We process 800-1,300 invoices monthly across fragmented systems (QuickBooks, ION, and Ramp) with no automatic integration or three-way match. This role will manage the full invoice-to-payment cycle, build scalable AP infrastructure, and establish the controls and processes needed to support our growth from prototype development through production ramp.
This is a hands-on role with significant ownership. You'll process high volumes while simultaneously building the systems, controls, and documentation that will scale with the company. You'll partner closely with Supply Chain on procurement workflows and with Finance leadership on cash management strategy and ERP implementation planning.
ResponsibilitiesInvoice Processing & Management- Process 800-1,300+ invoices monthly across QuickBooks, ION, and Ramp
- Review, code, and approve invoices ensuring proper GL account assignment, project codes, and class accounting
- Perform manual three-way matching across disconnected systems until ERP implementation
- Handle employee and candidate reimbursements, corporate card reconciliations, and ad-hoc payment requests
- Manage vendor setup, W-9 collection, and vendor master data maintenance
- Execute payment runs to capture early payment discounts and avoid late penalties
- Serve as primary point of contact for 150+ active vendors; resolve inquiries, disputes, and statement reconciliations
- Coordinate with Procurement on vendor onboarding, contracts, and payment terms
- Monitor aging reports and resolve payment holds or exceptions
- Build scalable AP infrastructure with automations where possible
- Design and document AP policies, procedures, and workflows for a scaling organization
- Implement approval matrices, segregation of duties, and fraud prevention controls
- Build audit-ready documentation and support external audits
- Maximize functionality of existing tools: Ramp Pro automation, ION workflows, QuickBooks coding rules
- Document current-state processes and pain points to inform 2026 ERP requirements
- Lead AP workstream for ERP selection, implementation, and data migration
- Maintain 1099 vendor tracking and support sales/use tax compliance and annual filings
- Partner with Supply Chain and Receiving on purchase order workflows and vendor management
- Train employees on policies, Ramp usage, and invoice submission requirements
- 5+ years of accounts payable experience, with at least 2 years in a senior or lead AP role
- Experience processing high-volume AP (500+ invoices/month) in a fast-paced environment
- Proficiency with AP automation tools and ERP systems
- Strong understanding of three-way match processes, GL coding, and month-end close procedures
- Experience with 1099 reporting, sales/use tax compliance, and audit support
- Track record of building or improving AP processes and controls
- Excellent attention to detail and ability to manage competing priorities
- Strong communication skills for vendor management and cross-functional collaboration
- Hardware, manufacturing, or aerospace/defense industry background
- Experience with government contract accounting (FAR/DFARS)
- Familiarity with Ramp, QuickBooks, and/or ION
- Experience supporting ERP implementations or system migrations
- SQL or reporting tool proficiency for building AP analytics
- Experience in high-growth companies navigating significant scale
Ownership mentality: Takes full accountability for AP operations and proactively identifies improvements
Builder mindset: Creates scalable processes rather than just executing existing ones
Detail-oriented: Catches errors, maintains accuracy under volume pressure, and keeps clean records
Systems thinker: Understands how AP connects to procurement, receiving, and financial reporting
Adaptable: Thrives in an environment where systems are imperfect and processes are evolving
Team player: Works effectively with Supply Chain, Engineering, and Finance partners
Additional Requirements- Must be willing to work extended hours and weekends as necessary to accomplish our mission.
- Must work 100% onsite at El Segundo HQ.
Total Compensation and Benefits
Radiant's new hire compensation package includes base salary, substantial equity grants, and comprehensive benefits. Total compensation and level are determined through a holistic evaluation of your interview performance, experience, education, and qualifications.
Benefits and Perks for Eligible Employees:
- Stock: Substantial incentive stock plan for all full-time employees.
- Medical: 100% premium coverage for base Silver level plan for employee + 50% premium coverage for dependents. Platinum plans available.
- One Medical: Sponsored memberships for eligible employees and their dependents.
- Vision: 100% premium coverage for top tier plan + 50% for dependents.
- Dental: 100% premium coverage for top tier plan (including orthodontia) + 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.
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.
Top Skills
Radiant Nuclear El Segundo, California, USA Office
1921 E. Maple Ave., El Segundo, CA, United States, 90245
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