Pictured above: The new Beakbane gaiters were approved after extensive testing

Beakbane has developed new protective covers that make it easier, cheaper and safer to service the equipment used to handle hazardous radioactive material. The Kidderminster-based bellows and machinery protection specialist has already received a substantial order to supply these to the waste vitrification plant at Sellafield Ltd.

The covers, known as gaiters, are fitted to the slave end of the master-slave manipulators (MSM) - large robot arms - that are used to handle radioactive materials during activities such as the disposal of nuclear waste and the processing of nuclear fuel. The gaiters reduce the amount of radioactive contamination the arms pick up in service and hence reduce the amount of decontamination required if they have to be removed for repair or servicing.

Decontamination is a laborious and expensive process, and the more contamination there is on the manipulator arm the more expensive it is to clean it. 

Beakbane has been supplying protective gaiters to the Sellafield Ltd for around twenty years now and has built up a strong relationship with its customers there. For most applications it supplies flexible polyurethane gaiters that provide the ease of use and durability required. There are a couple of areas though, such as the vitrification plant, where these do not provide the best solution.

High-level waste (HLW) is the most radioactive form of nuclear waste and is produced when spent fuel has been reprocessed through the Magnox and Thorp facilities. At Sellafield this waste is treated through a process called vitrification. This involves converting the high-level liquid waste into a solid form, reducing the volume of the liquid waste to one third of its original size. Vitrifying the waste enables the material to be stored safely and in preparation for eventual transport and permanent long term storage.

This is a tough radioactive working environment and the presence of heat and chemicals makes it even more hostile. In these conditions, polyurethane gaiters can become embrittled and tear. This allows radioactive particles to contaminate the slave arm and defeats the point of fitting them in the first place.

Working closely with Sellafield engineers, Beakbane developed a replacement gaiter made from woven cloth which is bonded to a layer of aluminium foil. This is mechanically stronger than the previous material and can also withstand the changes of temperature

The gaiters are around 1.5m long and 300mm in diameter and are split into two parts. At one end they incorporate an O-ring that forms a seal on the slaves gearbox down to its farthest point called the wrist, a fabricated bellows that allows the arm to extend and retract. All the parts are designed in CAD and cut out on a CNC machine before being assembled to form the completed gaiter, using special processes that ensure a 100% leak-tight seal.

The new gaiters have now been successfully trialled for over a year in real working conditions and adopted as standard equipment. Now, as each polyurethane gaiter in the vitrification plant reaches the end of its service life, it is replaced with one of the new aluminised glass cloth gaiters. 

The first of the new gaiters have already been in service twice as long as their predecessors with no sign of deterioration and will not need replacing as long as the slave manipulator arm remains in service.

Beakbane's managing director Barry Reeves said: "One of our core capabilities is to apply our expertise, experience and manufacturing capabilities to solve customers' problems. In this case we have developed a product that is mechanically stronger, can resist extremely aggressive environments and produces considerable benefits for the customer. We expect there to be a lot of interest in this new product wherever there is a need for remote handling in tough and hazardous environments and at extreme temperatures."

Improvement Engineer Colin Etheridge replied "Using our committed teams in conjunction with Beakbane, together we have developed a better product that not only keeps the Manipulator cleaner but can have significant reductions in the amounts of effluent produced in the cleaning process. Improvements in the above areas reduce our waste and environmental footprint."