---
title: 'Mechanical Engineer, Fluid Systems - 2026 New Graduate at Radiant Industries'
canonical: 'https://feeny.ai/job/mechanical-engineer-fluid-systems-2026-new-graduate-radiant-industries-el-72pbmfghye0y'
type: 'job'
last_seen: '2026-09-14'
---

# Mechanical Engineer, Fluid Systems - 2026 New Graduate at Radiant Industries

- **Company:** [Radiant Industries](https://feeny.ai/companies/radiant-industries)
- **Location:** El Segundo, CA
- **Compensation:** $105k–$125k
- **Employment:** full-time
- **Work type:** onsite
- **Posted:** 2026-06-02
- **Last confirmed live:** 2026-09-14
- **Apply:** https://jobs.ashbyhq.com/radiant-industries/6ab08a2a-61f7-4411-bdc6-a08bafe5be21/application

**Skills:** Fluid system architecture design, Fluid dynamics, Thermodynamics, Heat exchanger design, Heat exchanger analysis, Finite element tools, First-principle hand calculations, Matlab, Python, Fluid system modeling, Design for manufacturability, Test stand operation

> Radiant is seeking an entry-level Mechanical Engineer to own fluid systems for its Kaleidos microreactor, from preliminary design through production. The role involves thermal-hydraulic analysis, component selection, piping design, and vendor management to support the first new commercial reactor design in over 50 y...

## Job description

## About Radiant

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, 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. Radiant’s 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.

## About the Role

Radiant is seeking a highly motivated Mechanical Engineer, Fluids Systems to help own critical Kaleidos fluid systems from preliminary design through build and production. These systems include the primary loop subsystems and power conversion loop, serving to convert heat from the reactor core into electrical power. You will be responsible for the following: trade studies, component selection, thermal hydraulic analysis, piping design, vendor selection, assembly, and testing. You will have an instrumental impact of fueling the first new commercial reactor design in over 50 years by 2026.

Responsibilities & Duties:

- Help own end-to-end engineering of fluid systems and components, including compressors, valves, and heat exchangers.
- Perform thermal and fluids analysis to drive design decisions, verify system performance, and ensure structural integrity using first-principle hand calculations and finite element tools.
- Perform trade studies to optimize system and meet program requirements.
- Develop and execute manufacturing/assembly instructions and test plans.
- Create and manage a Bill-Of-Materials (BOM).
- Find and develop suppliers for all components.
- Own subassembly design, manufacturing, and test schedules.
- Own risk analysis (FMEA) for subsystems.
- Collect requirements, provide expertise and feedback to engineers in other functional areas via clear, constructive communication.

Required Qualifications & Skills:

- Bachelor’s degree from an accredited institution in Mechanical, Materials, Aeronautical, Civil or Structural Engineering.
- Experience with fluid system architecture design.
- Experience in designing, building, and testing fluids systems.
- Proficient knowledge in fluid dynamics and thermodynamics.
- Proficient knowledge of heat exchanger design and analysis methods.

Desired Qualifications & Skills:

- Knowledge of thermodynamic power cycles.
- Prior experience with fluid system modeling via Matlab/Python.
- Experienced in design for manufacturability and ramping up hardware build in a production environment.
- Experienced in designing and operating test stands.
- Takes extreme ownership of work and a high degree of responsibility.
- Excellent communication across multidisciplinary teams.
- Prior nuclear experience in not required for this role.

## Benefits and Perks

- 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. Radiant’s 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 today’s advanced reactor builders don’t wait for job postings. They join the winning team. If that’s you, contact us directly for immediate opportunities: recruiting@radiantnuclear.com.

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 applicant’s capacity to serve in compliance with U.S. export controls.

## About Radiant Industries

## Company Overview
- **One-liner**: Radiant Industries is building the world’s first mass‑produced, portable nuclear microreactor (Kaleidos) to replace diesel generators with zero‑emission, resilient power for remote sites, hospitals, data centers, and military installations.
- **Entity Type**: Private (Series D – $300M raised in December 2025, led by Lockheed Martin Ventures)
- **Headquarters**: El Segundo, California, USA
- **Founded**: 2020 (some sources list 2019)
- **Founders**: Not publicly disclosed

## Core Business
- **Primary industry**: Nuclear electric power generation / clean energy
- **Target customers**: B2B – remote communities, hospitals, data centers, military bases, industrial sites that currently rely on diesel generators or unstable grids
- **Mission**: To bring one of the world’s first factory‑constructed microreactors to market, providing portable, zero‑emissions power anywhere, anytime.

## Products & Services
- **[Kaleidos Microreactor](https://www.radiantnuclear.com/)**: A 1 MW electric / 1.9 MW thermal portable nuclear reactor packaged in a shipping container. It uses helium gas cooling and TRISO fuel (meltdown‑proof ceramic uranium particles). Delivered by truck or aircraft, installed without site excavation, and can reach full power the next day. After 5+ years the entire container is returned to the factory for refueling; up to four fuel cycles yield a 20‑year product lifetime. Customers purchase via Power Purchase Agreements (PPAs) or direct unit sales.

## Market Standing
- **Valuation / Market Cap**: Not disclosed
- **Key Metric**: Total funding raised – **$622.6M** (as of early 2026)
- **Notable Investors/Partners**: Andreessen Horowitz (led Series B), Lockheed Martin Ventures (led Series D), plus 18+ other investors across Series B, C, and D rounds
- **Growth Signals**:
  - Headcount grew **141% YoY** to 157 employees (as of mid‑2026)
  - 64 active job postings (+178% YoY)
  - Plans to test its development reactor in **2026** – which would be the first new commercial reactor design to achieve a fueled test in over 50 years
  - Initial customer deployments targeted for **2028**
  - SBIR Phase II awards from the U.S. Air Force for nuclear microreactor installation energy resilience

## Competitive Advantages
- **Portability & speed**: Delivered in a standard shipping container, installed in one day, no on‑site water or excavation needed.
- **Passive safety**: TRISO fuel is meltdown‑proof; the core is cooled by natural convection (air jacket) without pumps.
- **Factory‑built, factory‑refueled**: No nuclear waste or infrastructure left on site after the container is returned.
- **High energy density**: Over 110× the energy density of existing diesel systems.
- **Fleet monitoring**: Hundreds of units can be monitored 24/7 from a centralized control center.

## Strategic Focus
- Complete fueled testing of the Kaleidos prototype in 2026.
- Secure regulatory approvals (special nuclear material license, Part 7 license).
- Scale manufacturing for initial customer deployments beginning in 2028.
- Expand into military, commercial, and humanitarian markets (disaster relief, remote microgrids, backup power).

## Why Work Here
- **Culture & mission**: High‑impact climate tech – directly replacing diesel generators with clean nuclear power. Rated 5.0/5.0 on employer reviews (5 reviews) with strong scores for culture (4.7) and career growth (4.8).
- **Work location**: On‑site in El Segundo, CA (steps from the Pacific Ocean, near downtown). Employees work from a physical office.
- **Perks**: Company equity, relocation assistance, free daily meals, commuter benefits, onsite parking, generous parental leave, family medical leave, onsite Mother’s Room, dental/health insurance, FSA.
- **Diversity & inclusion**: Mandated unconscious bias training; hiring practices that promote diversity.
- **Tech stack**: React, TypeScript, Python, C++, C#, Kubernetes, Docker, PostgreSQL, AWS, Ansys, SolidWorks, Altium, and more. Engineers work on cutting‑edge nuclear, mechanical, and embedded systems.
- **Growth trajectory**: 141% headcount growth in the past year; 64 open roles across engineering, regulatory, supply chain, and operations.

## Sources
1. [radiantnuclear.com](https://www.radiantnuclear.com/) – Product details, specs, deployment model
2. [builtin.com](https://builtin.com/company/radiant) – Company overview, perks, culture, tech stack, reviews
3. [linkedin.com](https://www.linkedin.com/company/r-a-d-i-a-n-t) – Funding, headcount, employee growth, locations, key executives
4. [sbir.gov](https://www.sbir.gov/portfolio/1655711) – SBIR awards, Phase II contracts with U.S. Air Force
5. [jobs.ashbyhq.com](https://jobs.ashbyhq.com/radiant-industries) – Current open positions (64+)

## Other roles at Radiant Industries

- [PLM Administrator](https://feeny.ai/job/plm-administrator-radiant-industries-el-segundo-csy2rbcdhq2h) — El Segundo, CA
- [Senior System Administrator](https://feeny.ai/job/senior-system-administrator-radiant-industries-el-segundo-ajbhsjpanz1h) — El Segundo, CA
- [Nuclear Engineer, Sensors](https://feeny.ai/job/nuclear-engineer-sensors-radiant-industries-el-segundo-vw4q4fqf90mj) — El Segundo, CA
- [Principal Nuclear Engineer](https://feeny.ai/job/principal-nuclear-engineer-radiant-industries-el-segundo-ft4d50035gp0) — El Segundo, CA
- [Lead Nuclear Engineer](https://feeny.ai/job/lead-nuclear-engineer-radiant-industries-el-segundo-zds6vj27xyf1) — El Segundo, CA
- [Direct Procurement Manager](https://feeny.ai/job/direct-procurement-manager-radiant-industries-el-segundo-nkjv9abaxen0) — El Segundo, CA
- [Supply Chain Manager](https://feeny.ai/job/supply-chain-manager-radiant-industries-el-segundo-cftnmm6a4xf8) — El Segundo, CA
- [California Legislative Director](https://feeny.ai/job/california-legislative-director-radiant-industries-el-segundo-75jx3kkyzw2c) — El Segundo, CA
- [Quality Operations Specialist](https://feeny.ai/job/quality-operations-specialist-radiant-industries-el-segundo-6ezmmkzb2744) — El Segundo, CA
- [Senior FPGA Engineer, Verification](https://feeny.ai/job/senior-fpga-engineer-verification-radiant-industries-el-segundo-kher3k7r7tf4) — El Segundo, CA