Shaft Intervention Platform

PROJECT: Shaft Intervention Platform (SIP)

DURATION: 2013 to 2021

CLIENT: Dounreay Site Restoration Ltd (DSRL)

EXPERTISE: Remote Handling, Engineering Studies, solving complex problems with simple remote solutions

The challenge

A 65m deep shaft was created on the Dounreay site during the 1950s. It was latterly used as a store for Intermediate Level Waste to within 20m of ground level (see image at bottom of next page). The shaft is 4.6m in diameter and from its base extends 18m along a horizontal tunnel where waste and sludge have accumulated.

In March 2013, following a competitive exercise, Veolia Nuclear Solutions (VNS) was awarded a contract to develop a concept design for the equipment for clearance of the shaft and tunnel (see the illustration on page 2). VNS was able to assemble a multi-disciplinary team with the skills and experience to develop a solution for the unique and challenging problems of operations within the Dounreay shaft and tunnel.

Veolia's solution

The solution VNS developed consists of a Shaft Intervention Platform (SIP) from which two manipulator arms are suspended. The SIP is lowered into the shaft by a hoist system and the whole assembly is mounted on a trolley that allows the SIP to transfer from a shielded maintenance cell into the processing cell above the shaft opening.

The Tunnel Clearance System could be integrated together or implemented independently and needed to be capable of appropriate manipulation and reach to deal with a wide variety of tasks. The system also needed to be designed to facilitate remote recovery from any credible single point failure.

Tunnel Clearance

VNS invited external experts with knowledge of dredging and remote vehicles to participate in a review of the DSRL baseline concept for the tunnel clearance. An optioneering study of several alternative tunnel clearance concepts resulted in the proposal to use a remotely operated high-pressure water jet deployed from the SIP to reach the end of the 18m stub tunnel.

The concept of using a water jet is very much in line with the project's ethos of utilizing well understood technologies from other industries and adapting them for a nuclear application. VNS demonstrated the efficacy of this proposal by undertaking full-scale trials at its Assembly Integration and Test facility at Abingdon, applying the water-jet solution to a wide range of different materials (see photo below).

Manipulator Arms for the Shaft Intervention Platform

After a detailed optioneering process VNS selected the use of 2 telescopic manipulator arms. The kinematics of these proved more suitable than the more conventional anthropomorphic nuclear manipulators. The tasks are all performed below the SIP and require a long reach capability to access all areas of the shaft and mouth of the tunnel. Conventional manipulators are inappropriate for operation in the tightly confined shaft because of the "elbow" room they require.

Rather than design a bespoke manipulator, VNS modified an industrial telescopic crane of the sort usually found on delivery trucks. These COTS hydraulic arms are low cost and can be readily adapted because of their unsophisticated technology. The manipulator wrist axes are also COTS from the construction industry, assembled to provide the range of motion necessary to manipulate the tools. The tools are remotely docked to the arms by means of COTS tool changers normally found on earth moving equipment. The ability of VNS to recognise the potential of solutions using these COTS components and to convey that belief to DSRL produced a cost-effective solution with very low technical risk.

VNS was able to quickly assemble the telescopic arm and wrist components in order to demonstrate that such an arm is fit for purpose and can achieve the required TRL level for implementation in the SIP.

Full Design and Manufacture

Following the successful concept design stage VNS were awarded the contract for full design and manufacture of the SIP which was built and tested at the Abingdon facility. This included deployment of the SIP along rails and down into a mock-up shaft.

The benefits of VNS' innovative solution to clearing hazardous materials from the tunnel included reduced project risks, costs and timescales, which resulted in anticipated savings of approximately £600k from the project budget.

Steve Efemey, Project Manager, Dounreay

NDA Estate Supply Chain Award for the "Best application of an innovative solution with tangible savings/benefits from an SME"