Sellafield, Cumbria

Steve Vick International has been working with Corus Process Engineering (CPE) to provide sealing solutions for redundant sludge and effluent lines at Sellafield.

The latest project is to eliminate any potential fault scenarios on the plant and reduce operator dose uptake during implementation by avoiding the need to drain the effluent tank pipes of radioactive sludge before the sealing mechanism is deployed.

It is anticipated that the special sealing techniques which Steve Vick International has helped to develop will also accelerate the nuclear plant’s Effluent Tank remediation programme and deliver cost savings.

Background

In April 2006, Sellafield commissioned CPE to provide a sealing solution for two redundant sludge and effluent lines which connect the Magnox storage pond to the effluent tank. Due to the potential risk of a hydraulic ‘link’ between the two plants, the isolation or sealing of these lines was critical in order to enable the early start of the sludge and effluent removal from the Magnox storage pond.

The scope of work was to develop and demonstrate a method of sealing the lines which were located approximately seven metres underwater within the effluent tank sludge sump, and four metres underwater within the effluent tank inlet chamber.

After numerous trials, CPE made the decision to use Steve Vick International’s FOAMBAG system which employs a fabric bag positioned in the redundant pipe and subsequently filled with expanding resin foam.

Sealing lines into the Effluent tank

From the results of the initial trials at CPE Workington, it was quickly established that although the FOAMBAG™ technique would be suitable for the current application, the foam bag needed to be positioned within the pipework in dry conditions for system deployment. To achieve this would require additional work and time by the implementation team in a hazardous environment at Sellafield.

The project team, therefore, in conjunction with CPE and Steve Vick International, has developed a new system that gives greater confidence in the function of the seal. It also greatly reduces the time it will take to perform the isolation on site and reduces the dose burden that would otherwise make this such an onerous task.

To upgrade the performance of the original FOAMBAG™ for this project, Steve Vick International developed the High Integrity FOAMBAG™. It has two connected chambers which are filled with foam, creating a central void which allows a second fill operation with high performance resin. High Integrity FOAMBAG™ fully cured showing the central void filled with high performance resin

A chemical bond is formed between the pipe wall and the High Integrity FOAMBAG™ fabric shell enabling it to withstand higher pressures, vibration and shock loadings. The High Integrity FOAMBAG™ can be installed locally or from a distance of up to 50 metres from the access point. Deployment can be completed whilst the pipe is filled with media.

Sellafield Project Manager, Chris Cunningham, said*, “The project was very successful and represents a major risk reduction exercise for the Sellafield site. In terms of safety, the new sealing technique provides the plant with a step change in risk reduction and negates any potential fault scenarios with the effluent and sludge tank systems.”

“The approach taken on this project will realise an acceleration of the Effluent Tank Remediation programme of about two years with corresponding cost savings,” continued Chris Cunningham. “The solution will have additional safety benefits in terms of reduced operator dose uptake during implementation as the pipes no longer have to be drained of liquor before the sealing process takes place.”

Stuart Pegler, project Engineer at CPE, added: “Potentially, the new sealing and deployment technique has many other applications at Sellafield and may offer opportunities as a technical solution in the remediation and decommissioning of facilities across the site.”

* Source: Process Engineering Online, published March 10th 2008

Date Published – 6th April 2006