Lead Reactor Physics & Shielding Engineer

Remote within the United States | One week per month in Northern California | Full-timeAbout the CompanyOur client is a well-capitalised advanced nuclear developer building a compact PWR platform designed to make clean, reliable baseload power faster and more scalable to deploy.The company is combining proven reactor fundamentals with a radically different approach to manufacturing and deployment. It is now assembling the technical leadership team that will take the technology through detailed design, licensing and commercial delivery.This is an opportunity to join early enough to shape the reactor, analytical methods and engineering organisation, not simply inherit an established programme.The OpportunityThe company is seeking a Lead Reactor Physics & Shielding Engineer to take technical ownership of reactor physics, criticality, shielding and source-term analysis across its reactor programme.This is a foundational position with significant influence over the reactor design and analysis strategy. You will establish calculation methodologies, perform and review critical analysis, support licensing and safety documentation, and help build the technical capability as the programme grows.This is not a narrow shielding or core-analysis position. The successful candidate will connect core design, depletion, criticality, radiation transport, source terms and dose analysis into a defensible overall methodology.ResponsibilitiesOwn reactor-physics and shielding analysis across the reactor programme.Support core geometry, lattice design, enrichment selection, reactivity control and shutdown-margin development.Perform criticality, kinetics, reactivity-coefficient, depletion and cycle-length calculations.Develop criticality-safety cases covering fresh fuel, in-core fuel, spent fuel and storage configurations.Establish and maintain qualified calculation models, base decks and analysis workflows.Develop core, coolant, activation and decommissioning source terms.Design primary and secondary shielding and produce occupational and facility dose maps.Analyse deep-penetration radiation streaming through complex penetrations using variance-reduction techniques.Cross-verify computational methods and support benchmarking, uncertainty analysis and validation.Provide neutronics, shielding and source-term inputs to safety analyses and licensing documentation.Support reactor-safety-report chapters and design-basis accident dose calculations.Work closely with thermal-hydraulics, mechanical, fuel, safety, licensing and operations teams.Provide technical leadership, review engineering calculations and mentor developing engineers.Experience RequiredMS or PhD in Nuclear Engineering, Reactor Physics, Health Physics or a closely related discipline.Significant hands-on reactor-physics, criticality or radiation-transport experience.Production experience with tools such as MCNP, SCALE, Serpent, OpenMC, CASMO/SIMULATE or comparable codes.Experience with lattice-physics, burnup or depletion calculations.Demonstrated shielding and dose-analysis capability, ideally including deep-penetration problems and variance reduction.Experience with nuclide-inventory, activation or decay tools such as ORIGEN or an equivalent.Strong understanding of criticality safety, shutdown margin, power distributions, reactivity coefficients and fuel depletion.Ability to develop, validate, document and defend safety-relevant analytical methodologies.Experience contributing to reactor safety reports, licensing calculations or regulatory-facing documentation.Strong communication skills and the ability to operate effectively within a fast-moving, multidisciplinary engineering environment.Particularly Relevant ExperienceCompact PWRs, SMRs, microreactors or other advanced-reactor programmes.Core design involving alternative reactivity-control approaches or near-boron-free operation.Criticality benchmarking and development of Upper Subcritical Limits.SCALE/MAVRIC, Monaco, ADVANTG or comparable variance-reduction methodologies.Candidates do not need to have used every code listed. Equivalent tools and transferable experience will be considered, the priority is analytical depth, sound engineering judgement and the ability to own the complete technical scope.Working ArrangementThis position can be performed remotely within the United States, with an expectation of spending approximately one week per month onsite in Northern California.The organisation offers a highly competitive compensation package, substantial technical ownership and the opportunity to shape a reactor programme from an early stage.