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From CAD User AEC Magazine  Vol 22 No 11 - NOVEMBER/DECEMBER 2009

How does this grab you? Taking apart a nuclear reactor at Dounreay needed a bit of Design Innovation

Aformer nuclear research establishment in the process of being decommissioned. The creation of robot-like machines to roam the plant and do the jobs that no human can. The development of these devices in a virtual environment where life-size models react on screen as if they were the real thing.

It sounds like a chapter from a science fiction novel. However, this is no story, but the reality of life at the UK's former centre of fast reactor research at Dounreay in Northern Scotland. Here, a by-product of deconstructing the complex technology of a former generation, is the development of ideas that will help the next. For example, engineers working for Dounreay Site Restoration Ltd (DSRL), the company responsible for decommissioning the plant, are breaking new ground in digital design and the use of visualisation and animation in product design.

The result will be a futuristic Reactor Dismantling Manipulator (RDM), nicknamed the Reactorsaurus, which will be used to help take apart Dounreay's Prototype Fast Breeder Reactor (PFR). But the intricacy of this robot - and the serious nature of the tasks it will need to perform - means its capability and actions need to be rehearsed in life-like scenarios before the actual event. For this reason, a life-size model of the manipulator will be made before the real thing and a contract for the construction of this will be awarded later this year. However before this, the device and the reactor itself have been modelled digitally using Autodesk Inventor, 3D digital design software, AutoCAD Electrical and Autodesk 3ds Max. According to DSRL engineering manager, Jared Fraser, this means the construction of the mock-up, and subsequently the actual manipulator, should be far more straightforward and faster than it would have been otherwise. "Much of the work and trouble shooting has been done already on screen," he says.

NEW BENCHMARKS

Dounreay's PFR was the UK's second and last fast breeder reactor. It had the dual role of providing power to the national grid, as well as offering unique research and development facilities. Its dismantling is a long and complex process, due to be completed in 2024. It has already involved the building of the world's largest destruction plant for liquid metal, the elimination of 1,500 tonnes of bulk liquid sodium and the development of a new effluent treatment plant. However, the actual, physical dismantling of the inside of the reactor is at the heart of the challenge. Needless to say, this is no-go territory for humans - and consequently, in 2007, Jared and his team began to design a remotecontrolled device to carry out the work.

The result is a 75-tonne machine which moves back and forth on rails and is activated from a central control room. It has two remotely operated manipulators and robotic arms incorporating specialist cutting and handling tools. These will reach down into the reactor via a comparatively small 3.7 metre space and then extend to access even the furthest parts. An integral, radiation-tolerant camera system within the arms of the device will relay images back to the control room.

But according to Colin Watson of Imass Ltd, which has supplied DSRL with its design software, the project will leave yet another legacy. "The modelling of the manipulator and the reactor represents new benchmarks in digital prototyping and the modelling of large assemblies," he says.

As a highly-experienced designer, Jared has been using Autodesk Inventor since the software was first developed and released. Now, he particularly appreciates its testing and analysis capabilities, which the team use in conjunction with Ansys Design Space to simulate loadings and carry out Finite Element Analysis (FEA).

As he explains, the amount of FEA needed on this project has been vast - to the point where, on Imass' recommendation, this was outsourced to specialist company Wilde FEA. Using a 3D digital model means different solutions can be quickly tested and the results fed directly back into the model. Every time a change is made, the entire model and all linked drawings and documents are updated automatically, so it is fast and easy to test the impact of any change on the rest of the design. This has been particularly important because of the specialist materials, including rubber, steel and hydraulic fluids, needed to withstand the high levels or radiation within the reactor. But, according to Jared, one of the main challenges of the design phase was checking whether the Reactor Dismantling Manipulator would actually fit inside the small penetration in the reactor. "It's a small space and a very large machine, so clash detection has been an extremely useful tool for us," he says. To check this, the team has digitally modelled the reactor using data from old drawings. This enables them to simulate the entry of the RDM and its cutting and lifting actions.

"One of the benefits of having a complete digital prototype of the RDM and the reactor is that this one model can be used for many purposes - we don't have to keep recreating data or developing new drawings for testing and analysis or to create an animation to demonstrate what we are doing," says Jared. This last point is an important one. Because of the sensitive nature of the DSRL's work, the number of stakeholders involved, and the sheer size and expense of the overall decommissioning task, it is vital for the team that they are able to communicate their work in a way that everybody can understand.

"If you sit down with somebody and run through a set of 2D drawings they may well find them difficult to interpret. However, show a couple of 3D images, pan around them and simulate movement to show how everything will work and you'll find they become far more engaged and better able to understand with what you are saying," he says.

In fact, Jared and his team have gone further than this and used the 3D model to produce a seven minute animation to show stakeholders exactly how they plan to dismantle the reactor using the RDM. To do this they have taken the Inventor model, stripped it back taking away details not needed for this purpose, and migrated it to Autodesk 3ds Max, a design visualisation tool.

Throughout the project the DSRL team has worked closely with Imass. "Whenever we hit a challenge, the Imass team was there for us, particularly because we are modelling such a large object with thousands of components," says Jared. "In fact, they held special workshops to help us overcome the problems we had with this."

Despite the fact that the design phase is clearly only the beginning of this long "Reactorsaurus" project, Jared believes that much of the groundwork has already been done. "The contract for the mock-up has gone to tender and we have been able to give potential manufacturers a DWF of around 400 drawings so they can see dimensions, parts and what the finished device should look like. Hopefully, many potential pitfalls have been identified and already put right on screen."

After the next phase, the job of developing the actual RDM will be put out to tender too. It is estimated that it will cost around £3 million to build and will be commissioned in 2013. It will take around three years to complete its task of destroying the reactor, after which it will be decontaminated and decommissioned itself.

By the time the RDM embarks on its task of stripping out the reactor, virtual environments, digital prototyping and robots may well be commonplace - and not just on projects as sensitive as this one. Meantime, it is encouraging to know that out of a major dismantling task, new ideas have flourished and look set to become reality in the years to come.

www.imass.co.uk

www.autodesk.com

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