Senior Thermohydraulic Analyst

Blykalla; Stockholms kommun; On-site; SEK 750,000 - 1,100,000; Full time

Job summary

Blykalla in Stockholm seeks a Senior Thermohydraulic Analyst to lead system-level analyses of the SEALER primary loop, supporting design-basis transients and safety demonstrations. You will perform CFD studies where needed, maintain TH models, and document assumptions.

You will collaborate with Nuclear and Safety, Test and Validation, and Materials teams, with strong emphasis on safety and accuracy. Fluent English is required; Swedish is a plus.

Qualifications

• Approximately 10+ years of thermohydraulic analysis experience in nuclear or related field.
• Degree in nuclear, mechanical, energy, chemical engineering, or related discipline.
• Hands-on experience with at least one nuclear system-level TH code (RELAP5/TRACE/CATHARE/APROS/MELCOR).
• Strong fundamentals in single-phase & two-phase TH, natural circulation, reactor safety analysis.
• Fluent scripting in Python or MATLAB for pre-/post-processing, studies, and uncertainty propagation.
• Ability to write rigorous technical reports that withstand independent review and regulatory scrutiny.
• Fluent in English; Swedish language is a plus.
• Experience with CFD tools (STAR-CCM+/ANSYS OpenFOAM) is highly valued.

Responsibilities

• Perform system-level thermohydraulic analyses of the SEALER primary loop under normal and design-basis transients.
• Perform CFD analyses on components/regions where system-level tools are insufficient.
• Support fluid system engineers with pressure drop budgets, transient response calculations, NPSH assessments, and related analyses.
• Set up and maintain plant TH models; document modelling assumptions, uncertainties, and limitations.
• Conduct sensitivity and uncertainty analyses to understand modelling impacts on design conclusions.
• Contribute TH input to safety analyses and interface with Nuclear and Safety team on accident analyses.
• Coach junior engineers on TH fundamentals, modelling practices, and code use.
• Support qualification, verification, and validation of in-house codes against benchmarks.

Skills

Thermohydraulic analysis

Nuclear industry experience

Python or MATLAB

CFD tools

Technical writing

English fluent

Swedish a plus

Lead-bismuth TH knowledge

Gen IV reactor familiarity

Code validation/compliance

Education

Engineering degree (Nuclear/Mechanical/Energy)

Tools

RELAP5

TRACE

CATHARE

MELCOR

STAR-CCM+

OpenFOAM

Job description

What we do at Blykalla

Blykalla is a Swedish deep-tech company at the forefront of the nuclear industry, pioneering the development of small modular reactors that provide clean, safe, and reliable energy. Thanks to lead-cooling, we achieve high safety in a very compact format, allowing for a simple and cost-effective design that can be mass-produced. Our unique reactor design will provide safe and green baseload energy that perfectly complements solar and wind power.

The role

You will be the senior in-house thermohydraulic analyst for Blykalla's fluid systems, executing the analyses that underpin the design of the primary loop, safety-classified systems, and balance of plant.

This means running the system-level thermohydraulic calculations that the system engineers scope, from steady-state performance and pressure drop budgets through transient analyses, natural circulation, and passive safety demonstrations. Where system-level tools are not sufficient, you may also perform CFD analyses. You will work closely with the Nuclear and Safety team, particularly where thermohydraulic analyses interface with safety transient and accident analyses.

The role is analytical, hands-on, and cross-cutting. You will not own individual systems, but you will support the system engineers with the calculations they need, and you will be one of the senior technical voices Blykalla relies on when the numbers get hard.

What you'll get to do

• Perform system-level thermohydraulic analyses of the SEALER primary loop under normal operating conditions and design-basis transients, working closely with the Nuclear and Safety team, which is responsible for the safety transient analyses.
• Perform CFD analyses on selected components and regions where system-level tools are not sufficient, such as mixing zones, thermal stratification, plena, and heat exchanger inlets and outlets.
• Support fluid system engineers with pressure drop budgets, transient response calculations, NPSH assessments, and other thermohydraulic analyses needed to develop and verify their designs.
• Set up and maintain the plant thermohydraulic models, validate them against experimental data from Blykalla's test facilities and relevant published data, and clearly document modelling assumptions, uncertainties, and limitations.
• Perform sensitivity and uncertainty analyses where needed to understand key modelling assumptions and their impact on design conclusions.
• Contribute thermohydraulic input to safety analysis reports and interface closely with the Nuclear and Safety team on accident analyses and passive safety demonstrations.
• Coach junior engineers and system engineers on thermohydraulic fundamentals, modelling practices, and code use.
• Support the qualification, verification, and validation of the codes used in-house against international benchmarks and relevant validation datasets.
• Help develop Blykalla's thermohydraulic analysis methods, modelling standards, and engineering practices as the SEALER design matures.

Who you'll get to work with

The Senior Thermohydraulic Analyst sits in the Fluid Systems Engineering Team within Blykalla and reports to the Manager of Fluid Systems Engineering.

You will collaborate daily with the fluid system engineers and interface closely with the Nuclear and Safety, Test and Validation, and Materials teams, as well as with academic and industrial partners on code validation and experimental campaigns.

We are a diverse team that is passionate about our work and Blykalla.

Who you are

You will be part of a highly skilled team with a can-do attitude. We value personnel chemistry and strive to create a workplace where you enjoy coming to. There are, however, a few things that we think will help you succeed in this role:

• Around 10 years or more of professional experience as a thermohydraulic analyst in the nuclear industry, or in a closely related field with equivalent analytical depth.
• A degree in nuclear, mechanical, energy, chemical engineering, or a related discipline.
• Deep hands-on experience with at least one nuclear system-level thermohydraulic code, such as RELAP5, TRACE, CATHARE, APROS, MELCOR, or equivalent.
• Strong fundamentals in single-phase and two-phase thermohydraulics, natural circulation, and reactor safety analysis.
• Fluent scripting in Python or MATLAB for pre- and post-processing, parametric studies, sensitivity analyses, and uncertainty propagation.
• The ability to write rigorous technical reports that stand up to independent review and regulatory scrutiny.
• Fluent in English, spoken and written.
• Fluency in Swedish is a plus.

Experience with at least one CFD tool, such as STAR-CCM+, ANSYS Fluent, OpenFOAM, or equivalent, applied to reactor, fluid system, or heat exchanger problems is highly valued.

Meritorious skills

• Prior experience with Generation IV reactor programmes (LFR, SFR, MSR), especially heavy liquid metal systems.
• Familiarity with thermohydraulic phenomena specific to lead and lead-bismuth systems, including heat transfer correlations, natural convection, void behaviour, and chemistry-induced deposits.
• Prior experience supporting a nuclear licensing submittal (SSM, NRC, or equivalent) with thermohydraulic analyses.
• Code development, code coupling, or code verification and validation experience.
• Experience with test facility data analysis, benchmark exercises, or international validation projects.

Location

This position is for our office in Stockholm.

So, what do you think?

We are proud to foster an inclusive workplace free from discrimination. We strongly believe that diversity of experience, perspectives, and background will lead to a better environment for our employees and a better product. This is something we value deeply and we encourage everyone to be a part of changing the way the world thinks about power supply!

We are not open to external help from recruitment agencies.