Senior Neutronics Engineer

Position Description

The Senior Neutronics Engineer is responsible for developing and executing neutronics analyses supporting the design, optimization, operation, and safety evaluation of an isotope production reactor. The engineer will perform analyses to support core design, fuel cycle, target performance, shielding, and sensitivity/uncertainty quantification across the reactor lifecycle and isotope production facility.

This role requires close collaboration with thermal hydraulics, mechanical design, materials, isotope processing, operations, safety, and licensing teams. The engineer will translate system and production objectives into analysis requirements; develop appropriate computational models and methods; and produce technically sound, traceable, and defensible results. Areas of analysis include criticality, depletion, isotope production, target optimization, shielding, activation, source term, and sensitivity/uncertainty analysis.

The isotope division is a small but growing team so the candidate must be capable of operating in a highly iterative and independent environment.

Specific responsibilities may include:

• Perform reactor core design and optimization using Monte Carlo and, where appropriate, deterministic neutron transport methods.

• Develop and execute models using codes such as MCNP, Serpent, and SCALE.

• Perform core lifecycle and fuel management analyses, including depletion, burnup, reactivity evolution, power distributions, fuel utilization, and operating cycle optimization.

• Evaluate core physics parameters, including excess reactivity, control element worth, shutdown margin, reactivity coefficients, kinetics parameters, and criticality safety margins.

• Design and optimize irradiation targets to meet isotope yield, specific activity, radionuclidic purity, heat limits, and production schedule objectives.

• Perform depletion, activation, decay, and transmutation analyses for fuel, targets, structural materials, experimental hardware, and reactor components.

• Develop neutron and photon source terms for shielding, activation, decay heat, dose, and isotope processing evaluations.

• Perform shielding analyses using variance reduction techniques.

• Apply sensitivity and uncertainty methods using tools such as TSUNAMI and SAMPLER to quantify nuclear data, modeling, and manufacturing uncertainties.

• Establish appropriate biases and uncertainties to establish design margins.

• Develop, qualify, and maintain computational methods, analysis procedures, cross-section libraries, and reference models.

• Perform verification and validation using critical experiments, shielding benchmarks, depletion benchmarks, operating data, and applicable international benchmark programs.

• Support the design and evaluation of startup testing, physics measurements, irradiation experiments, and reactor surveillance activities.

• Couple neutronics results with thermal hydraulic, mechanical, isotope processing, and safety analyses.

• Perform design space exploration and optimization across competing objectives such as isotope production, fuel utilization, power peaking, irradiation damage, cycle length, and safety margin.

• Develop repeatable analysis workflows using modern software development practices, including configuration control, automated testing, code review, and reproducible data processing.

• Provide timely technical feedback to rapidly iterating multidisciplinary design teams.

• Document assumptions, methods, results, uncertainties, and limitations in clear technical reports.

• Support design reviews, safety evaluations, licensing activities, and responses to regulatory questions.

Minimum Qualifications:

• If you have experience and expertise in reactor design, apply! We also think the following are good indicators of qualifications to do this job: Bachelors, Masters, or PhD in a technical field, such as nuclear engineering, with experience in reactor design and analysis (Masters or PhD may be preferable).

• Fluency with Python.

• Proficiency with high performance computing systems.

• Proficiency with MCNP, SERPENT, or SCALE (TRITON, KENO, SAMPLER, TSUNAMI, MAVRIC) is highly recommended.

Bonus Qualifications:

• Hands on experience with irradiation experiments at a research and test reactor is a plus.

Competencies

We are looking for a senior neutronics engineer who is:

• Passionate about applying nuclear technology to isotope production.

• Knowledgeable about reactor physics and radiation transport methods.

• Experience with methods for light water/research and test reactor analysis.

• Highly skilled with Monte Carlo tools such as MCNP, Serpent, SCALE, or OpenMC.

• Experienced with or eager to develop expertise in sensitivity and uncertainty analyses.

• Familiar with shielding calculations and variance reduction methods.

• Interested in irradiation target design and isotope yield optimization.

• Able to develop and qualify computational methods using benchmarks, experiments, and independent verification.

• Comfortable working across neutronics, thermal hydraulics, materials, mechanical design, operations, safety, and licensing disciplines.

• Proficient in scientific programming and analysis automation, preferably using Python or a comparable language.

• Attentive to model configuration, software quality assurance, traceability, and reproducibility.

• Able to identify important assumptions and communicate the effects of uncertainty on engineering decisions.

• Willing and able to learn quickly and take ownership of technically challenging work.

• Comfortable in a fast-paced, highly iterative development environment.

• Willing to propose creative, technically rigorous solutions rather than relying solely on established approaches.

• An excellent technical writer who communicates assumptions, methods, limitations, and conclusions clearly.

• Able to present technical content and results effectively to both specialist and multidisciplinary audiences.

Who you are:

A startup person: You aren’t driven by titles or hierarchy, and prefer efficiency to excess process. You don’t need or expect to have a lot of guidance but you enjoy working in a fast-paced team. If you prefer the culture and feel of a large organization, that is great, but you likely won’t enjoy working with us! There is plenty of important work and plenty of good opportunities with organizations like that.

Motivated: You are self-motivated. You bring an enthusiasm to the team, and imbue a sense of passion that goes beyond clocking in and clocking out. This isn’t about a fake or arbitrary “pieces of flair” mentality or lack of work-life balance! It is about being a part of the vision and feeling a part of reaching team goals.

A team-player: Oklo genuinely is a team. We aren’t about taking credit for ourselves, and we aren’t about pushing blame to others. We do incredible things because we work as a team.

An excellent communicator: We need a person who is not only technically competent but also a clear and upbeat communicator.

Creative: Being creative means that when things fall outside clear scopes or processes or problems arise without clear solutions, you are able to identify it as well as invent ways to solve a problem or fill a need without micromanagement. The successful person in this job will not only be creative, but also enjoy being creative and solving open-ended problems which may change day-by-day.

Detail-oriented: This focus is a big part of excellence, consistency, and quality. Excellent grammar and spelling matter for both good communication as well as the image of the company that we put forward.

About Oklo travel requirements:

Oklo requires remote employees to travel to headquarters (Santa Clara, CA) twice a quarter annually, based on business or team needs, including attendance at team meetings, off-sites, and other company events or gatherings. For the first two weeks of onboarding, employees are required to be in person at headquarters in Santa Clara, CA.