Engineering savings at Sellafield

THE VIRTUAL ENGINEERING CENTRE (VEC) worked with Sellafield Limited to co-develop a mixed reality training simulator that mimics the real-life working environment of Sellafield’s newly commissioned nuclear waste removal crane.

Sellafield approached the VEC with a challenge to understand how virtual reality could be used to inform and benefit the design of new facilities and equipment — such as specialist cranes — in the early stages.

In particular, Sellafield was looking to ensure the safety of specialist operators of its newly-commissioned crane, designed to scoop up and remove hazardous material from the site’s 70-year-old Pile Fuel Cladding Silo (PFCS).

Commissioned for use in 1952, the Pile Fuel Cladding Silo received and safely stored radioactive cladding from uranium fuel rods used some of the UK’s earliest nuclear reactors. The structure is 21m high and, inside, houses six extremely tall waste containers. It was originally designed to be permanently sealed, meaning innovative ways of accessing and retrieving the waste had to be developed.

Upgrade work completed on the PFCS in the 1990s made it possible to continue to use the structure safely. The silo holds more than 3200 cubic metres of intermediate-level waste.

The objective of the Sellafield Pile Fuel Cladding Silo (PFCS) programme is to retrieve waste from the facility. Each section of concrete had to be cut away in a single piece (known as the monolith) and withdrawn into a containment bag. Six containment doors (already installed on all compartments) were then lowered over the apertures and closed.

To remove the waste, a crane extends through the holes, a grabber will then drop down to scoop the waste up, lifting it out of the container and back through the hole.

The crane then drops the waste into a specially-designed metal box, for safe and secure storage in a modern facility.

To support overall risk reduction the key driver is to deliver the waste retrieval equipment as soon as possible. To achieve quicker delivery a ‘fit for purpose’ approach was taken for the retrieval equipment design, particularly the retrievals crane at the heart of the process. A standard ‘commercial-off-the-shelf’ crane/grab was selected, although for PFCS the operations would be undertaken remotely, using CCTV to view the crane inside the silo. To prevent crane clashes with the silo walls emphasis was placed on skilled operators managing the safety risk (as other industries would do), rather than designing a complex zoning system that would hamper operations.

The team recognised the importance of the Human Factors (HF) safety aspects for the crane operation and realised that new technology could potentially support the operators to achieve the required skill levels before operating the crane in the silo.

Developing a virtual training solution

A basic simulator was developed very quickly from existing Sellafield 3D design models containing digital information on the silo and crane. The VEC team then integrated crane movements into a simulator, controlled from a chair with a built-in joystick identical to the real crane. The VR model replicated the real plant CCTV camera views, allowing the virtual cameras to be controlled as they would be onsite.

Lynn Dwyer, Head of Commercial at The Virtual Engineering Centre (VEC) says: “The relationship with Sellafield started with a number of industry challenge led sandpit sessions. Our unique ‘sandpit’ model allows technology organisations to enhance their capabilities through virtual innovation, accessing academic research and the latest scientific and technology infrastructure.”

“We are always open-minded during these sessions... exploring a range of options to co-create a solution with the client. In this instance, a mixed reality solution best addressed Sellafield’s unique set of challenges,” Dwyer adds.

Cross-functional teams from Sellafield’s training, operations and specialist human factors divisions took part in the sessions. The team developed the training modules before finalising a crane training programme. The outcome was then used to familiarise and provide confidence to key Sellafield stakeholders, including senior management, the Office for Nuclear Regulation (ONR) and the Nuclear Decommissioning Authority (NDA).

The crane training simulator provides a realistic environment for Sellafield’s operators, both visually and physically. It includes accurate manipulation and haptic feedback of all control systems. It also mimics both the look and feel of the waste removal process and the environment in which the operator will be working. The VR environment enabled operators to learn to ‘drive’ the nuclear waste retrieval crane in a safe environment before a full-scale training environment was available.

Virtual reality training systems are extremely cost- effective compared to traditional physical mock-up-based rigs. This is the case because the digital information required is now readily available. There are clearly environmental and safety benefits from working in virtual reality rather than in physical space.

The approach used on PFCS has been shared within Sellafield Limited, with ONR and NDA, and there is potentially of benefit across the wider NDA estate. The operators fed back differences between the

simulator and real plant (for example slight variations in crane speed), to help improve the simulator. The operators completed the task of filling a 3m3 waste container with simulant waste in just one day on the first attempt. The progressive training approach using the VR simulator made this remarkable achievement possible.

Benefits of VR training

The realistic user experience of the training simulator built operator confidence and shortened the overall project schedule. In the design phase, the operators identified where visual aids would help them position the crane more precisely, and these spatial and design features were added to the real plant during its construction.

Being able to identify project needs quickly enabled Sellafield to make quick and easy changes before the crane went into manufacture.

The simulator is now so sophisticated that the project team have decided to use it as the primary tool for crane operator training. In the long term, this will allow the full-scale training rig to be re-purposed as a second retrieval system, saving £20 million on the cost of future waste retrievals.