Posted on: 25th October 2012

picture of site water system at JET

The refurbishment of the site water system at the Culham Science Centre is under way.

One of the most interesting refurbishment tasks for JET this year is costing over half a million euros, extending the lifetime of JET and reducing operating costs.

The original construction of JET’s site cooling water system was carried out under two separate contracts. The pipework in the immediate area of the cooling towers passed its original design lifetime long ago and continued to work successfully. However, for the last four or five years it has been plagued with a series of chronic water leaks. This has not been enough to interrupt operations, but it was certainly sufficient to have a noticeable impact on running costs. Water leaking from the system has to be replaced with fresh water, which has to be specially treated before it can be used.

picture of corroded part of the pipes

An example of a corroded part of the pipes that are being replaced. The smaller of the two corroded hole is more than 10mm wide. (The small round hole was drilled to facilitate removal of the affected area.)

Remarkably, the pipes around the rest of the site are still in good condition, thanks to the choice of cast iron as opposed to mild steel in the corroded sections. It was originally hoped that the leaking pipes could be repaired using ‘trenchless technology’ where a leak-tight lining is installed inside the pipes without disturbing the ground. Several companies expressed an interest in the task, but in the end none of them tendered. Consequently a contract has been placed with a company to design, fabricate install and test about 200m of pipe as large as 700mm in diameter. Since August, trenches have been dug and much of the old pipework has been removed. It is being replaced by new pipes of the same material, carbon steel with a bitumen coating. These are likely to be serviceable for at least 20 years. This large operation has progressed according to plan, and by early November the task should be complete, pressure tests will have been carried out, and the performance of the system demonstrated against benchmark measurements that were taken on the old system.