Criticality Safety Engineer

Subcritical Systems, Inc. is a venture-backed startup in Austin, Texas building the accelerator driven systems and the only US commercial manufacturer of accelerator cavities. What Space X did for rockets, we plan to do for accelerator cavities and commercialize across applications of power production, medical isotopes, semiconductors and waste transmutation. We are in the process of building the Energy Amplifier, a novel nuclear fission system in which a particle accelerator drives a subcritical core, making melt‑down physically impossible for clean power production. Due to its inherent safety, our system has a more streamlined licensing process. Our founding team includes successful entrepreneurs with a track record of building several multibillion dollar companies in deep‑tech, and scientists who were leading U.S. national labs with deep experience in accelerator & nuclear technologies. We are actively hiring to expand our team as we work toward licensing, regulatory submissions, and construction of our first energy amplifier. More information is available at subcritical.com.

ROLE SUMMARY

We seek an experienced Criticality Safety Engineer to provide nuclear criticality safety (NCS) leadership, with supporting radiation shielding input and radiation machine operational support, across Subcritical Systems facilities. The role supports both the Austin Fabrication Facility, including operational support for state‑registered/state‑licensed radiation machines, and the Energy Amplifier program, including design reviews, contractor deliverable review, coordination with Licensing, support for accelerator and target shielding, and development of the 10 CFR Part 70 license application. Reporting to the Head of Regulatory Affairs, this individual will serve as the company's internal owner for criticality safety analyses, program documentation, and NCS‑related portions of the Integrated Safety Analysis (ISA). Contractors may initially develop portions of the ISA and CSAs; this role will review, challenge, accept, and maintain assigned deliverables as the Energy Amplifier Facility is designed, built, commissioned, and operated. Successful candidates combine hands‑on analytical capability with strong safety‑basis judgment, and the ability to translate complex calculations into facility requirements, IROFS/controls, procedures, and license application content.

KEY RESPONSIBILITIES

Criticality Safety Analysis, Computational Modeling & Independent Review Develop, validate, and maintain criticality safety calculations for fuel receipt, storage, handling, transport, core loading, operation, shutdown, maintenance configurations, and credible abnormal conditions using SCALE/KENO/TSUNAMI, MCNP, Serpent, or equivalent Perform sensitivity and uncertainty analyses, bias and bias uncertainty determinations, and upper subcritical limit (USL) development for fissile material operations, consistent with ANSI/ANS‑8 standards, NUREG/CR‑6698, and applicable NRC expectations. Evaluate subcritical multiplication factor, reactivity margins, moderation/flooding scenarios, geometry changes, reflection, material degradation, and credible reactivity insertion scenarios for Energy Amplifier configurations Review, challenge, and formally accept contractor and vendor criticality safety calculations, assumptions, methods, validation bases, margins, and conclusions before incorporation into the licensing or operating basis Translate analysis results into controlled parameters, design requirements, operating limits, surveillance requirements, procedures, and configuration‑management requirements Criticality Safety Program Development & Maintenance Author, maintain, and improve the Criticality Safety Program Plan, Criticality Safety Evaluations, CSAs, nuclear criticality safety assessments, and supporting calculation packages in accordance with 10 CFR Part 70, ANSI/ANS‑8 standards, and Subcritical procedures Establish and maintain the double‑contingency compliance matrix and controlled‑parameter basis for all fissile material handling and storage operations Define, and periodically review NCS controls: engineered controls, physical limits, administrative controls, inspections, surveillances, and management measures Maintain the facility Criticality Safety Basis as part of the ISA, ISA Summary, and license application Develop or maintain the criticality accident alarm system basis, emergency response plan, and associated training if required Integrated Safety Analysis, Licensing Interface & Contractor Deliverable Ownership Serve as the NCS SME to the Licensing team for the 10 CFR Part 70 license application; support ISA Summary content, safety program descriptions, IROFS descriptions, and responses to NRC RAI responses Participate in ISA, PHA/HAZOP, What-If, FMEA, and accident sequence reviews to ensure that criticality, radiation, accelerator, fire, and chemical hazards are consistently integrated Review contractor ISA, CSA, and safety‑basis deliverables for technical adequacy, regulatory completeness, design integration, and maintainability; track comments to closure and assume ownership after turnover Develop and maintain NCS‑relevant IROFS, including safety functions, management measures, and configuration controls Interface with Licensing, NRC staff, state regulators, contractors, and independent reviewers on NCS, accelerator safety, and shielding topics Radiation Safety, Accelerator & Fabrication Facility Support Support radiation shielding evaluations for the Austin Fabrication Facility, accelerator systems, beamlines, targets, penetrations, temporary shielding, and ALARA‑driven work planning Support or review photon and neutron shielding, activation, dose‑rate, skyshine, and streaming calculations using MCNP, SCALE/MAVRIC, ADVANTG, Attila/Attila4MC, or equivalent Support compliance of state‑registered radiation machines, including procedures, interlocks, surveys, dosimetry, postings, inventories, training, and inspection support Support or serve as RSO if designated including maintenance of radiation machine registrations, records, and regulator communications. Design Review, Engineering Change Control & Operations Support Serve as Criticality Safety SME in preliminary, critical, and final design reviews for fuel handling, accelerator, target, storage, and facility modifications, coordinating shielding inputs with Health Physics and Licensing Review and concur on engineering changes, nonconformances, temporary modifications, and maintenance activities affecting fissile material configuration, shielding, beam operations, or radiation controls. Conduct periodic NCS and radiation safety walk‑downs of fissile material areas, fuel storage, radiation machine areas, and accelerator areas Provide on‑call technical support for operational question ...

QUALIFICATIONS

Required B.S. in Nuclear Engineering, Health Physics, Physics, or a closely related technical field; M.S. or Ph.D. preferred. Minimum 3 years of nuclear criticality safety, safety analysis, or fuel‑cycle/accelerator safety experience. Advanced degrees may substitute for part of the experience Demonstrated experience performing or reviewing CSE/CSAs as part of a nuclear facility safety basis, preferably for an NRC‑licensed fuel cycle, DOE, or advanced nuclear facility. Working knowledge of 10 CFR Part 70 Subpart H, Integrated Safety Analysis, IROFS/management measures, ANSI/ANS‑8 standards, or NUREG‑1520. Hands‑on experience with criticality codes such as SCALE/KENO/TSUNAMI, MCNP, Serpent, or equivalent; familiarity with shielding tools such as ADVANTG, Attila/Attila4MC, MAVRIC, or equivalent Ability to independently review contractor/vendor deliverables, identify gaps in assumptions and methods, and convert deliverables into controlled company‑owned licensing and operating‑basis documents. Excellent written and verbal communication skills; ability to write defensible calculation packages, safety‑basis sections, procedures, and regulator‑facing responses. Strong safety culture, technical ownership, attention to detail, and ability to work effectively in a fast‑paced startup environment with evolving design information. Preferred Direct experience supporting 10 CFR Part 70 license applications, ISA Summaries, NRC audits, inspections, and RAI responses. Experience with HALEU, fuel fabrication, handling/storage, accelerator‑driven systems, high‑power accelerators, target systems, or advanced reactor/fast‑spectrum applications. Experience with Texas DSHS radiation machine registration requirements, state inspections, industrial or research accelerators, or serving as/supporting a Radiation Safety Officer. Experience with nuclear QA programs, calculation verification, design control, and configuration management. Familiarity with critical experiments, benchmark selection, and sensitivity/uncertainty methods. Familiarity with AI‑enabled tools, or automation to improve calculation workflows and document quality

BENEFITS

We offer health, dental, and vision insurance

LOCATION & WORK POLICY

This role is fully in person in Austin, Texas. Our facility is located next to Austin Airport.

HOW TO APPLY

Apply on LinkedIn or submit your resume and a brief cover letter to View email address on click.appcast.io with the subject line "Criticality Safety Engineer - Application". Applications are reviewed on a rolling basis. #J-18808-Ljbffr Subcritical Systems Inc