Design supervision of a nuclear ventilation system equipment

Context and challenges

This client is a leading group in the UK nuclear sector.

It is responsible for the safe and secure operation and clean-up of the Sellafield nuclear site. It now comprises 400 buildings spread over 10 square kilometers and employs around 10,000 people.

In order to ensure the continuation of safe site operations, the client needed to address the integrity of an ageing ventilation system carrying a category 1 risk rating assigned by the nuclear regulator.

The operation was time sensitive, with environmental authorities pressuring on this client to swiftly address the issue and ensure the safety of the pipework which is classified as C5 (the highest level of contamination).

The project’s success would be based on two key deliverables: the creation of a bypass section of ductwork (a Duct Control Connection Assembly, or DCCA) and finding a way to cut the ducting while ensuring the contaminated area remained sealed off.

This client has mandated Assystem as part of the AXIOM collaboration (a multi-disciplinary joint-venture design and safety contract) to design and produce a proof of concept design and subsequently the detailed design for implementation on site (22” duct bypass and fan removal).

Project scope

Development of novel equipment, to attach the DCCA to the contaminated duct, in order to stabilise ventilation pressure and to allow a section of ductwork to be removed whilst ensuring no breach of containment during the installation.
Development of a unique internal duct cutter capable of removing a narrow band of duct whilst maintaining the containment.
Creation of a 1:1 dynamic scale replica of the site facility and ductwork (off site by Assystem’s manufacturing partner using original drawings, laser-scanning techniques and advice from Sellafield site staff). This allowed Assystem to collaborate with its manufacturing partner and the client to visualise solutions and practically test equipment and the DCCA in a safe, uncontaminated environment. The facility provided the additional benefit of operational training prior to installation.
Delivery of the full design solution, these designs will then be manufactured by a subcontracted manufacturing partner to enable the client to confidently implement on site with the full knowledge that the design solution has attracted the highest level of verification and validation.

Client benefits

Minimisation of the number of time-consuming reviews, improving the project’s efficiency, thanks to Assystem’s autonomous teams (ISO 9001:2015 accredited internal management system) enabling the project team to manage the design, checking and approvals before seeking final acceptance from the client.
Efficient resources management, the right resources were available at the right time at each stage of the project, resulting from the use of a specific internal resource database, National Skills Academy Nuclear (NSAN) to select precisely the right resources.
Time-savings resulting from advanced planning and the preparation of a list of pre-approved suppliers before selecting the most suitable candidate as its manufacturing partner.
Improve testing phase and time and money savings, thanks to producing a mock-up/replication of the client-site including any obstacles that would have to be considered (with Assystem’s manufacturing partner), ensuring all testing could take place in a safe, controlled and representative environment. This method not only provided a practical means of testing solutions but removed the need to test equipment at the client’s site.
Good coordination of projects, the design and development of the duct cutting tool was placed under a separate reimbursable project so as not to affect other project activities, and was delivered to the client early and under budget.
Adaptation of the design to any changes from the client’s original brief, thanks to using an internal quality management process and the site mock-up. One such example was a risk assessment which identified a need for an interlocking function. Using the mock-up, examples could be designed and tested with millimetre accuracy before being passed for final client approval within a short space of time.