Job Description:

⚡️💡 About Assystem

At Assystem, our mission is to accelerate the energy transition worldwide. Our 8,000 Switchers blend historical engineering expertise with cutting-edge digital technologies to drive this change. Join us in revolutionizing the energy sector and making a significant global impact.

🤝 Why Join the Community of Switchers?

Be part of one of the top three largest independent nuclear engineering companies globally. At Assystem, you'll contribute to groundbreaking projects that push the boundaries of innovation and engineering excellence. Join a community committed to driving forward the future of energy.

We are seeking a skilled Software Developer to play a key role in supporting Instrumentation & Control (I&C) system commissioning across a major nuclear project. This role focuses on designing, developing, testing, and supporting software solutions that enable safe, efficient, and compliant commissioning activities on one of the UK’s most significant infrastructure projects.

You will develop robust, scalable applications using technologies such as Python, JavaScript, and PostgreSQL, contributing across the full software development lifecycle - from requirements capture and technical design through to implementation, testing, deployment, and ongoing optimisation.

We are looking for someone who is comfortable working across both server-side and client-side technologies, has a strong understanding of modern web architectures, and takes pride in delivering clean, maintainable, and high‑quality code. A proactive approach to troubleshooting, performance optimisation, and continuous improvement is essential, along with a desire to stay current with emerging technologies and best practices.

This is a hands-on role within a fast‑paced commissioning environment, requiring strong attention to detail, adaptability, and effective collaboration with multidisciplinary teams. Your work will directly support the safe startup and long-term performance of critical nuclear systems.

Roles & Responsibilities:

• Design technical solutions to support I&C commissioning engineers, simplifying the use and interpretation of I&C data.
• Improve and maintain web-based applications.
• Implement backend logic, data processing workflows, and automation solutions using Python.
• Build responsive, user-friendly frontend components and interactive features using JavaScript.
• Design, manage, and optimise relational databases in PostgreSQL.
• Write performant SQL queries, stored procedures, and data migration scripts.
• Ensure data integrity and security across environments.
• Ensure software quality by testing and writing documentation.
• Conduct unit testing, integration testing, and assist in user acceptance testing.
• Write technical specifications and installation procedures.
• Assist in writing user manuals.
• Debug, troubleshoot, and resolve software defects across the stack.
• Deploy and maintain these tools.
• Collaborate with cybersecurity team.
• Ensuring high standards of security, performance, and scalability across all developed solutions.
• Contribute to the continuous improvement of development practices and code quality standards.

Essential

• Proven experience developing web applications.
• Strong proficiency in Python and at least one major Python framework (FastAPI, Flask, Django).
• Strong knowledge of JavaScript and common front-end libraries (ideally Angular).
• Solid understanding of SQL database: modelling, query optimisation, and performance tuning.
• The ability to innovate, think laterally and implement processes.
• Fluent in spoken and written English. 

Desirable

• Degree in software development.
• Experience with containerisation technologies such as Docker.
• Familiarity with cloud platforms (AWS, Azure, GCP) or on-premises hosting environments.

Additional information

🌟 Join us at Assystem and be part of a global team delivering some of the most exciting and complex engineering projects in the world. This is your chance to shape the UK’s energy future while developing your expertise in a unique environment.

Benefits include:

🏡 Hybrid Working Opportunity
🕒 Flexible working hours
🛡️ Pension scheme (8% company contribution / 4% personal contribution)
🏖️ 25 days’ paid annual leave + bank holidays + option to buy or sell days
💼 Professional fees reimbursed
💰 Employee referral scheme
🤒 Competitive Sick Pay – Support when you need it
🏥 Income Protection & 3x Salary Death-in-Service Cover
💪 Free Digital Gym Access – Expert-led fitness classes
📞 24/7 Employee Support Line – Mental health, financial & legal help

We are committed to equal treatment of candidates and promote, as well as foster all forms of diversity within our company. We believe that bringing together people with different backgrounds and perspectives is essential for creating innovative and impactful solutions. Skills, talent, and our people’s ability to dare are the only things that matter!

Bring your unique contributions and help us shape the future

NOTICE TO CANDIDATES ON RECRUITMENT FRAUD - We are committed to safeguarding candidates from fraudulent activity associated with our recruitment process. Please note that we will never offer specialist CV writing services, request payment or ask for sensitive personal information during the recruitment process.

We are committed to equal treatment of candidates and promote, as well as foster all forms of diversity within our company. We believe that bringing together people with different backgrounds and perspectives is essential for creating innovative and impactful solutions. Skills, talent, and our people’s ability to dare are the only things that matter !. Bring your unique contributions and help us shape the future.