Job Description

Principal Developers are responsible for designing, developing, and implementing innovative technical software solutions (both on-prem and cloud) that meet ISO/ICT’s, and Sellafield Ltd.’s, strategic business needs.

They serve as Subject Matter Experts for the technical aspects of software products within the ISO portfolio. They are responsible for the delivery of bespoke applications development and maintenance for projects. They develop and maintain bespoke applications as part of the ISO Development and Configuration capability, delivering solutions in a safe, secure, and professional manner to relevant technical and business best practice and standards in order to support Sellafield Ltd in its technical vision.

Principal Accountabilities

• Support the delivery of digital products across ISO/ICT and Sellafield Ltd by developing software components and writing clean, secure, and well-tested code to provide quality solutions.
• Troubleshoot and resolve complex technical issues that arise during development and after deployment.
• Provide technical leadership during all phases of the software development lifecycle (SDLC).
• Ensure that security, stability and capacity are embedded in the development and deployment of services.
• Proactively manage service components in line with key performance indicators (KPIs), supporting service availability and capacity management as well as the identification and resolution of service faults.
• Optimise development processes by analysing existing workflows, identifying improvements, and supporting their implementation.
• Design, review, and support the quality assurance of software solutions to ensure they effectively mitigate security threats.
• Apply modern development techniques and standards to the delivery of all software solutions and encourage adherence to them among other developers.
• Use a variety of prototyping methods, sharing best practice and supporting other developers in their application, while considering the strategic end-to-end design of services.
• Design systems in line with architectural principles, policies and organisational standards. This may also include supporting their implementation and procurement.
• Support systems integration by defining the integration build, coordinating build activities across systems, and participating in testing.
• Support engagement with the Digital & Business Partnering team to understand customer needs and translate them into user stories. This includes identifying appropriate tools and methods to prioritise user stories and clearly articulating the distinction between user needs and desires.

Essential Skills

• A degree or equivalent experience in a relevant field, such as Computer Science.
• Strong understanding of agile software development methodologies.
• Excellent problem solving and analytical skills.
• Strong interpersonal skills, demonstrating ability to work in teams and collaborate effectively.
• Strong stakeholder engagement; ability to translate business needs into technical solutions.
• Excellent documentation and knowledge‑transfer capability.
• Proficiency with Test Strategies, Test Frameworks and Test Automation.
• Proficiency in some or all of the following:
• C#, SQL, PL/SQL, JavaScript, Vue.js, React, HTML, CSS, PowerShell.
• Microsoft Power Platform and PowerApp development.
• Proficiency in K2 and/or ServiceNow.
• Deep Azure expertise across core services (Compute, Storage, Networking, Identity, Security, Monitoring).
• Complex workload migrations into Azure, including operationalisation.
• DevOps engineering: CI/CD (e.g., Azure DevOps/GitHub), IaC (Terraform, Bicep, ARM), automation (PowerShell, Bash).
• Azure security and governance (Entra ID, Conditional Access, PIM, Defender for Cloud, Azure Policy, RBAC, Key Vault, Private Endpoints, BYOIP/Hub‑Spoke).
• Experience with cost management (tags, budgets, reservations, rightsizing, workloads on demand).
• Expertise in observability: Azure Monitor, Log Analytics, Application Insights, alerts, workbooks.

Desirable Skills

• Proven experience as a Full Stack Developer.
• Able to lead and mentor junior developers.
• Knowledge of the Microsoft Power Platform Centre Of Excellence process and governance.
• Experience working in a highly regulated environment.
• Understanding of Sellafield Ltd, including its operations and ICT estate or equivalent.

Additional Information

• Open VN
• Number of Vacancies: 8
• Contact/s: Ian Cousins/Steve Jones

The interviews for this vacancy are expected to be between 6th & 10th July 2026.

ASW’s may have the right to apply for internal Sellafield Ltd vacancies. Please note if you are an Agency Supplied Worker you are required to attach evidence of all qualifications obtained to support your application. We require a minimum of A*-C (9-4) GCSE in English Language, Maths & Science/IT or equivalent / higher qualification.

If you choose to apply for this role and your application is shortlisted by the hiring manager, you will be invited to a competency based interview. In the interview, you will be assessed against the below competencies:

Behavioural:
1. Commitment to Standards – 3.1.5
2. Commitment to Nuclear Safety and Security – 3.1.1
3. Safely Deliver Results & Inspire Our People – Drive Accountability and Lead Others
4. Create the Future – Future-Focused and Vision-Aligned
5. Set Direction – Lead and Shape Change

Technical:
1. Using IT at work – 31.3
2. Driving and facilitating change – 37.6

Please see link to the competency framework for further information:
https://slportal.ssa-intra.net/pub/SC001/00027/Competency%20Framework/Forms/AllItems.aspx

If your technical competency is not in the above framework, please refer to the profession’s share point page for further information.

There will be a requirement for a presentation and further details will be given at interview stage.

This presentation should be sent to recruitment@sellafieldcloud.co.uk via email at least two working days before your interview. You should also take four paper copies of your presentation to your interview in case of any IT issues on the day.

Sellafield Ltd are recognised as a Disability Confident Employer (Level 3). Disability Confident employers offer an interview to disabled applicants that meet the minimum criteria for a vacancy. Sellafield Ltd define the minimum criteria as the ‘essential skills’ which are listed on the vacancy notice. Whilst completing your application form, you will be able to indicate if you wish to be considered under the disability confident scheme. If you would prefer to discuss this directly with us, please contact the GBS Recruitment team on recruitment@sellafieldcloud.co.uk

Please ensure that you save a copy of this advert for future reference if you make an application for this role.

The closing date for this vacancy is 14th June 2026.