Trawsfynydd Reactor Dismantling – Design and Integration Support

MARKETS: Power & renewables; Nuclear

LOCATION: Trawsfynydd, United Kingdom

CLIENT: Nuclear Restoration Services

COMPLETION DATE: 2025

AtkinsRéalis has partnered with Nuclear Restoration Services (NRS) to support the dismantling of the Trawsfynydd Nuclear Power Station, a site that has been defueled since 1995. The project is a pivotal move to reflect the NDA’s shift the decommissioning strategy for Magnox reactors, a type of reactor designed to run on uranium, with graphite as a moderator and carbon dioxide as the heat exchange coolant. Trawsfynydd was chosen as the lead site for a Rolling Programme of Decommissioning, aiming to avoid further delays and guide future dismantling efforts.

The challenge

The NRS required integration support to consolidate and manage extensive data sets provided from all scheme design packages.

This included:

1. Developing a digital management strategy, including Building Information Modelling (BIM) datasets, a platform for uploading and accessing Computer-Aided Design (CAD) models.
2. Management of information and data associated with all scheme design packages.
3. Integrating designs from all Scheme Design Packs.
4. Providing a Technical Integration Manager to oversee the process.

AtkinsRéalis solution

AtkinsRéalis developed a comprehensive digital strategy to capture and understand the existing site configuration, ensuring seamless information exchange across all scheme design packages. Through utilising a range of advanced digital tools, the team communicated project details and objectives to all stakeholders. This approach ensured that design execution was in line with the Information Management (IM) principles and ISO 19650 standards, which promotes efficiency and collaboration throughout the project.

Digital services provided

Digital services provided

Information Management (IM) services

AtkinsRéalis provided an Information Manager to work on behalf of NRS to support with setup and delivery of scheme design. The support would include general project delivery, and a client advisory service, which both services would ensure NRS were able to articulate the need for information, make sure they get the right information, and enabling information to be exploited to aid the project delivery teams.

Common Data Environment (CDE)

AtkinsRéalis identified and established the necessary CDE’s for the project based on the technical specification, and type of information that would be produced and collated from all stakeholders throughout the scheme design. These included:

• Autodesk Construction Cloud – Documentation of historic drawings, 2D and 3D CAD data
• CIRRUSinsite – Survey data
• Information exchanges between CDE’s were detailed to enable collaboration and better access to information.

Shielding services reach back

The existing Reactor Activation Model (RAM) at Trawsfynydd did not distinguish between the operational lifetimes of the reactors. Therefore, AtkinsRéalis conducted a review of the reactors operational histories and completed the following:

• Calculated dose rates of the reactor following bio-shield and pile cap break in.
• Updated the dose rate model and revised moderator support structure neutron fluxes.
• Reviewed the sensitivity of several components around the equator of the reactor to radial and axial changes in neutron flux.
• Updated the RAM with updated moderator support structure neutron flux data.
• Determined the sensitivity of standpipe activities to radial and Axial neutron flux distribution.

Reality capture

The digital team at AtkinsRéalis conducted comprehensive site surveys, utilising techniques such as laser scanning, point cloud dimensional surveys, and a combination of panoramic and standard photos and videos. The survey data was transferred to CIRRUSinsite, an in-house cloud-based platform developed by AtkinsRéalis, used to store, manage, view, and disseminate survey information. Access to this platform was granted to all project members, enabling access to as-built information, facilitating more informed decision-making processes.

Model development & verification

AtkinsRéalis provided CAD resources, responsible for generating initial models as a basis for other scheme design contractors, civil and mechanical models of the reactor building and components, and waste packages. The Civil Structural team converted the original civil construction drawings of the existing Reactor building into a comprehensive model using Autodesk Revit, which was subsequently refined against point cloud data using FARO products. Various mechanical models were generated in Autodesk Inventor of more detailed components such In-Core Furniture, Shield Cooling, Pile cap, and the RPV & Core.

BIM coordination

The BIM Coordinator integrated various data types, including point cloud data, existing structural models, and new conceptual designs from all scheme design packages. Using the mechanical and structural models developed by AtkinsRéalis, a federated model of the Reactor 2 building was constructed, and continuously updated with new data and designs from other scheme design packs, ensuring compatibility and aiding clash detection. The BIM Coordinator formulated a clash matrix, conducted tests in Navisworks, and relayed the results back to the design teams for necessary design alterations. The unified model was made available to all project stakeholders through the ACC.

Dismantling and operations animation

Additional digital tasks will be undertaken using operational and 4D sequencing, along with ‘fly-through’ animations. These will be developed to provide a visual representation of the design team’s strategy for disassembling the reactor building and its components, as well as the sequence of these operations.

Key benefits and success factors

The results of AtkinsRéalis digital strategy for supporting the decommissioning of Trawsfynydd Nuclear Power Station included:

Single source of information - Our Common Data Environment (CDE) centralises all designs, data, and models, ensuring easy access and enhancing stakeholder collaboration. This consistency across scheme design packages streamlines the entire process.

Better-informed clients - By demonstrating the importance of Information Management (IM), we equip NRS with the knowledge to ask the right questions and make informed decisions in future projects, benefiting both them and AtkinsRéalis.

Digitally de-risked designs – Implementing BIM coordination and 4D planning/phasing allows us to identify clashes and errors early in the design lifecycle, significantly reducing risks and ensuring smoother project execution.

Reduced on-site presence – Utilising digital scan data enhances model accuracy, ensuring the reliability of designs and reducing the need for stakeholders to travel to the site. This not only saves time but also cuts down on travel-related costs and emissions.

Better-informed decision making - With accurate, real-time easily accessible, stakeholders can make well-informed decisions quickly, driving the project forward with confidence.