Senior Test Engineer, Mechanical/Fluids

About Radiant

Radiant is an El Segundo, CA-based company building the world's only mass-produced, transportable nuclear microreactors. The U.S. grid is under growing strain, with power demand accelerating, driving higher utility costs, rising carbon emissions, and interconnection backlogs. Radiant has a solution, transportable, on-site power. Our first reactor, Kaleidos, is 1 megawatt: small enough to be factory-built, transported by land, sea, or air, and deployed wherever power is needed. 1 MW can power 1000 homes for five years. Ship it back and we refuel for a 20 year operating life. We made energy a product that can be used for critical infrastructure like military bases, data centers, hospitals, and remote sites, as well as the commercial main street businesses that keep America running. Founded in 2020, Radiant is under contract to deliver power to the U.S. Army, Navy and Air Force and has signed pre-order agreements with Equinix, with deployments beginning in 2028.

We are seeking a Senior Test Engineer to drive test operations for the development, qualification, and acceptance of our nuclear microreactor technology, with a primary focus on fluid and mechanical systems. This role offers a rare opportunity to bridge engineering, operations, and human factors in a highly technical and fast-paced environment. You will collaborate with a multidisciplinary team to translate complex hardware and software designs into clear, executable test operations, with encompassing test procedures that will efficiently and safely execute test, commissioning, and operational activities.

As part of a small, passionate, and accomplished team of test engineers, you will help drive test operations to meet Radiant’s requirements in a fast-paced production environment. You will directly contribute to test operations by assisting with test planning and execution, risk identification and mitigation, hardware integration for test campaigns, post-test inspections, data review, and hardware performance analysis.

This position goes beyond traditional systems engineering - you will also gain hands-on experience as a test conductor and test director, directly influencing the development of operational software, procedures, and test ground support equipment.

Responsibilities & Duties

Test Strategy, Planning & Technical Ownership

Own and lead the test strategy across development, qualification, and production acceptance phases.

Define test objectives, plans, success criteria, instrumentation strategies, and data requirements for hardware and systems.

Serve as the technical authority for test methods, measurement quality, and data integrity.

Translate analytical predictions and design requirements into targeted test campaigns that validate assumptions and retire risk.

Balance test coverage, technical risk, schedule, and hardware availability to enable rapid iteration while maintaining safety and rigor.

Test Execution & Data Analysis

Serve as Test Conductor/Test Director, ensuring procedures reflect real-world execution.

Plan and execute fluid, mechanical, and thermal tests on Kaleidos hardware, from component level to full system development, qualification, and acceptance.

Partner with design engineers to develop test methods and fixtures for fluid, mechanical, and electrical hardware.

Integrate hardware into test setups: plumbing, instrumentation, data acquisition, and controls.

Author and maintain test procedures meeting DOE/NRC-aligned documentation standards, with strict formatting, clarity, and usability.

Identify risks and hazards (e.g., FMECA, keep-out zones) and define mitigations for pressurized and high-energy tests.

Analyze test data, compare results to analytical predictions, and support root cause investigations.

Specify and source test components and help qualify suppliers for fabrication.

Drive continuous improvement in test processes and data quality.

Support one-off test campaigns in a fast-moving environment where requirements are still being defined.

Required Qualifications & Skills