We are expanding our engineering team and are seeking a Neutronics Engineer to support advanced reactor and fusion programmes. Working in multidisciplinary teams, you will ensure neutronics analysis meaningfully informs design decisions and programme strategy. Key duties include: Perform Monte Carlo neutronics analyses using tools such as OpenMC for neutron and photon responses relevant to fusion device optimisation and design, comprising facility and component‑level assessments including depletion, activation, shielding and criticality. Construct simulation‑ready geometry models, including CSG and CAD‑based representations. Lead verification and validation (V&V) of neutronics analyses through comparison with benchmark problems, experimental data, and independent codes, whilst also promoting software development best practices and version control (using Git) within the company. Integrate neutronics workflows into automated analysis pipelines, including scripting and in-house tool development. Apply engineering judgement across adjacent disciplines (e.g. thermal hydraulics, materials, fuel performance, structural design) to interpret results and inform design trade‑offs in collaboration with quick-iterating design teams. Maintain awareness of international reactor and fusion neutronics activities, benchmarks, and experimental programmes, and apply relevant insights to Oxford Sigma work. Ensure all work is delivered in accordance with the Oxford Sigma Management System, including document control, design reviews and technical governance. Support knowledge sharing and capability development within the team, including informal mentoring of less‑experienced engineers where appropriate and line management. Qualifications & Experience Ideally, you will have some of these: Bachelor’s degree (or higher) in Nuclear Engineering, Physics, Mechanical Engineering, or a closely related discipline. 3 - 8 years experience in neutronics analysis for nuclear fission and/or fusion systems in a fusion company, national laboratory, or scientific research environment. Candidates with sufficient demonstrated experience will be considered for the role of Senior Neutronics Engineer. Considerations will be made for hiring into a Senior role. Demonstrated experience with Monte Carlo neutronics codes such as OpenMC, and inventory codes such as FISPACT-II. Proficiency in Python for scientific computing, workflow automation, and data analysis. Awareness of legal and contractual aspects of project activities, such as procurement, processes, negotiation strategies, and regulatory compliance. Ability to communicate complex technical results clearly to both specialists and non‑specialists. Excellent verbal and written communication and presentation skills, including technical document quality. Experience as a project team member in a multi-partner interdisciplinary environment. Additionally, it would be advantageous if you have: Experience in CadQuery, DAGMC and Paramak workflows. Experience in integrated thermal, neutronic and structural design and analysis. Experience with other codes such as MCNP, MONK and MOOSE. Experience in applying AI and ML. Experience in experimental validation of neutronics simulations and models. Eligibility Due to the nature of the work, candidates must be British citizens and have been continuously resident in the UK for the past five years Our Benefits 28 days annual leave pro-rata. Company bonus scheme. Flexible working around core hours. Company pension scheme. Cycle to work scheme. Enhanced parental pay. Inclusion in the Business Health Scheme. Assist and support chartership progression with the appropriate body Additional Information It is anticipated that this role may require for you to work on defence related projects. Underrepresented people are less likely to apply for engineering roles if they do not meet 100% of the job requirements. We are actively seeking these kinds of applicants and believe in hiring people not checklists. If you are interested but unsure if your experience aligns, please get in touch with our Recruitment Team (careers@oxfordsigma.com) to discuss if this role or others we are developing may match you as a person. When applying please upload both a CV and Cover Letter in pdf format explaining why you would like to apply for the role and more about your skills and experience.