Nuclear Engineer

About Avalanche Energy

Avalanche Energy is a Washington-based startup building compact, deployable fusion systems through rapid hardware iteration. Rather than pursuing fusion as a single grid‑scale outcome, Avalanche develops transportable fusion machines designed to be built, tested, and operated on short cycles, turning real hardware into steady progress. This approach enables near‑term applications that demand extreme energy density and endurance—starting with fusion neutron production for radioisotope power and other defense and space uses—while advancing the underlying fusion platform.

Backed by U.S. government programs and a team experienced in delivering complex systems, Avalanche is focused on building fusion that runs in the real world, not just on paper.

You are self‑motivated, energized by problem solving, and enjoy supporting a small, tight‑knit team working across a wide variety of technical challenges. You take pride in precision and getting the physics right, and you thrive in an environment where priorities can shift quickly. You communicate clearly, maintain strong attention to detail, and can work independently while building strong partnerships across the company.

You want to model real nuclear hardware—not hypothetical designs—and see your analysis inform actual regulatory submissions and engineering decisions. This is hands‑on neutronics experience that many nuclear engineers never get.

Avalanche Energy is seeking a Nuclear Engineer, Radiation Transport to perform neutronics modeling for our fusion neutron source programs. This is a high‑impact technical role. You will be responsible for developing and executing radiation transport calculations that support everything from tritium breeding and radioisotope production to shielding design and activation analysis. The work spans Monte Carlo simulation development, CAD‑to‑geometry workflows, variance reduction implementation, and model validation against experimental data.

You will inform nuclear design choices through trade studies and parametric analysis, with your results feeding directly into hardware decisions and regulatory filings.

• Develop and execute neutron and photon transport simulations using OpenMC and MCNP to support fusion neutron source development.
• Support iterative facility and shielding design in close collaboration with mechanical engineers, providing timely analysis to inform design decisions.
• Perform streaming, penetration, and skyshine analyses for complex shielding configurations.
• Perform tritium breeding calculations, radioisotope production modeling, and displacement damage (DPA) analysis.
• Contribute to regulatory deliverables including shielding design reports, airborne emission assessments, emergency planning dose evaluations, and activation/waste characterization documentation.
• Build and maintain CAD‑to‑geometry workflows for complex device geometries.
• Perform airborne source term and atmospheric dispersion analyses to support facility dose assessments, including release fraction estimation, Gaussian plume modeling, and dose conversion factor application for inhalation and submersion pathways.
• Validate models against experimental data and iterate to improve predictive accuracy.
• Contribute to continuous improvement of neutronics tool chains, workflows, and documentation.

• Proficiency in OpenMC and/or MCNP.
• Experience with CAD‑to‑geometry workflows for radiation transport problems.
• Strong Python scripting skills for automation, post‑processing, and workflow development.
• Experience with version control (Git) for managing simulation code bases and inputs.
• Hands‑on experience running radiation transport calculations for complex problems.
• Comfortable working in Linux environments and with cloud computing resources.
• Strong foundation in nuclear engineering fundamentals, including radiation interactions, neutron physics, and nuclear data.
• Interest and excitement in developing AI/LLM‑assisted workflows for neutronics analysis.
• Eligible for a DoD secret clearance or DOE Q clearance equivalent.

• PhD in nuclear…