A former nuclear research establishment is due to be decommissioned. Robotlike machines are being created to roam the plant and do the jobs that no human can. They have been created in a virtual environment where life-size CAD models are put through rigorous operational tests. TM talks to Dounreay Site Restoration’s Jared Fraser.
Robots deconstructing a nuclear reactor. It may sound like a chapter from a science fiction novel but it is reality for the former UK centre of fast reactor research in Dounreay, Scotland.
Engineers working for Dounreay Site Restoration Ltd (DSRL), the company responsible for decommissioning the plant, are breaking new ground in digital design, visualisation and animation in product design. Their aim is to produce a Reactor Dismantling Manipulator (RDM) robot, nicknamed the Reactorsaurus, which will be used to help dismantle Dounreay’s Prototype Fast Breeder Reactor (PFR). A PFR is a fast neutron reactor designed to breed, or produce, fuel by producing more fissile material than it consumes But the technical specification of the robot — and the dangerous nature of the tasks it will perform — mean its capabilities and actions must be rehearsed thoroughly before physical trials, so a life-size prototype of the RDM must be made before the operational version. The contract for the construction of RDM will be awarded later this year.
The RDM and the reactor have already been modelled using 3D design software Autodesk Inventor, AutoCAD Electrical and Autodesk 3ds Max. DSRL’s engineering manager Jared Fraser says the construction of both the mock-up and the actual manipulator should be faster and more straightforward than it would have been without the 3D CAD model. “Much of the work and troubleshooting has been done already on screen,” he says.
Robots love the jobs you hate
Dounreay’s PFR was the last fast breeder reactor in the UK. Its dismantling is a long and complex process which has already involved building the world’s biggest destruction plant for liquid metal, involving the elimination of 1,500 tonnes of liquid sodium, and the development of a new effluent treatment plant. But the physical dismantling of the inside of the reactor is at the heart of the challenge and as this is clearly an area off-limits to people, Fraser and his team created a remote-controlled device to do the work.
The result is a 75 tonne machine which moves 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 must reach down into the reactor via a 3.7 metre space and then extend to access the furthest recesses.
Colin Watson of Imass, which supplied the design software, says the modelling of the manipulator and the reactor represents a new benchmark in digital prototyping and the modelling of large assemblies. Fraser and his team used Autodesk Inventor with Ansys Design Space to simulate loadings and to carry out finite element analysis (FEA). The depth of FEA needed on this project was such that it was outsourced to a specialist company, Wilde FEA. Using a 3D digital model means different solutions can be tested quickly and the results fed directly back into the model. Whenever a change is made, the entire model and all linked drawings and documents are updated automatically.
One of the main challenges in the design was to check whether the RDM would fit inside the small penetration in the reactor. By creating a digital model of the reactor using data from old drawings, the team could accurately simulate the RDM’s entry.
“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 re-creating data for testing and analysis or create an animation to demonstrate what we’re doing,” says Fraser.
People can see in 3D
Several factors — the sensitive nature of DSRL’s work, the number of stakeholders, the sheer size and expense of the decommissioning task — means it is vital that the team can communicate its work in a way that everybody understands. “If you run somebody through a set of 2D drawings, they may find them difficult to interpret. But if you show them a couple of 3D images, pan around and simulate movement to show how everything works, people become far more engaged with what you’re saying,” Fraser says.
His team has even used the 3D model to produce a seven minute animation that shows stakeholders exactly how the company plans to dismantle the reactor using the RDM. To do this they stripped back the Inventor model and migrated it to Autodesk 3ds Max, a design visualisation tool.
DSRL worked closely with Imass through the project. “We were modelling such a large object with thousands of components but whenever we hit a challenge, the Imass team was there for us,” says Fraser. “They even held special workshops to help us.” Although the design phase is only the beginning of this long and complex project, Fraser 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 [computer file] of around 400 drawings so they can see dimensions, parts and what the finished device should look like. Hopefully, many potential pitfalls have already been identified and put right on screen.” After the next phase, the development of the RDM itself will also be put out to tender. It is estimated that it will cost around £3 million to build and will be commissioned in 2013. It will take three years to complete the destruction of the reactor, which will then be decontaminated and decommissioned.
By the time the RDM embarks on its task of stripping out the reactor, these virtual environments, digital prototypes and robots could be commonplace — and not just on projects as sensitive as this one. It is hoped that, in finessing this complex task of destruction and decommissioning, breakthrough ideas and methodologies will be developed that will help create future industrial designs.
