The programme to decommission the UKAEA site at Harwell in Oxfordshire and transform it into a world-class centre for excellence in science and innovation is a complex technical process requiring a great deal of hard work in planning and implementation.
One of the companies supporting UKAEA is Nuvia Limited (formerly NUKEM Limited). Nuvia offers an extensive engineering design resource for the nuclear industry ranging from new build plant for radioactive and hazardous environments, shielded facilities and containment systems, and treatment plants for solid and liquid active waste in addition to extensive radiation safety and consulting expertise.
Nuvia has been awarded a contract to design and build a nuclear waste encapsulation facility at the site, which has included an ExMac Automation conveyor system designed to transport stainless steel drums containing intermediate-level radioactive waste (ILW) through the process.
The drums, which are 800mm in diameter, 1200mm high and weigh up to 1000kg, are loaded onto the conveyor system from an existing drum storage facility. The conveyor system then transports the drums through the process, which involves drum inspection followed by grout filling of the drums, before transporting them back to the existing storage facility. During the process the weight of the drums increases to a maximum of 2000kg.
The Nuvia specification required the contact surface of the ExMac conveyors to be stainless steel. To meet this specification, ExMac designed a bespoke handling system consisting of sets of powered roller conveyors fitted with stainless steel tube rollers and side guides; and cross-chain transfer units having stainless steel pads fixed to the chains. The rectangular conveyor system layout carries drums inside a ‘cell’ with a concrete roof and walls. As the drive motors are located outside the cell, each of the conveyors is fitted with a through-wall drive to enable the drive shaft and coupling of the motor gearbox to connect to the conveyor chains that drive the rollers. The support structure of the conveyors and any equipment that is not in contact with the drums, are manufactured from carbon steel and finished with a special paint.
Because the cell is a restricted area ExMac has also designed and supplied a drum removal system consisting of a hand operated cable winch recovery bogie and hydraulic cylinder-driven drum pushers. In the event of a conveyor breakdown, the drum pushers are extended through the walls in order to push drums into a position where they can be transferred to the existing storage facility.
Proving all components and the system itself off-site was also a key requirement of the contract. This involved ExMac testing a sample of the conveyor drive system to ensure that the lubricant free drive chains used ‘incell’ were fit for purpose and could be approved. The system was then made and assembled in Worcester and laid out in the company’s workshops. Each item of equipment underwent a unit trial, which was then followed by a total factory acceptance test and buy-off by both Nuvia and its customer UKAEA. The whole system was then stripped down, packed, itemised, and delivered to site, where it was installed by Nuvia.
Commenting for Nuvia, design manager Andy Blue says: “ExMac Automation was involved in the project from the start, and the input of its design and engineering team on the conveying system was invaluable. The installation itself also went very smoothly and we were delighted with the result.