The Nuclear Decommissioning Authority

A technique to cut through underground pipes using high-pressure water has been used for the first time at Winfrith, where it has speeded up decommissioning work.

As part of the programme to clean up the site’s iconic Steam Generating Heavy Water Reactor (SGHWR), Research Sites Restoration Ltd (RSRL) employed the technique to remove redundant underground cooling water pipelines.

“Though it’s novel for us, high-pressure water-cutting is a tried-and-tested technique widely used in the petrochemical industry, where flame cutting is obviously out of the question,” said RSRL’s deputy project manager, Mike Wyatt.

“For us, the big advantage was that the pipes could be cut from the inside, avoiding the need for operatives to work in a deep trench. Cutting equipment was set up inside the pipe, the pipe was cut, the equipment was reset and another cut was made. This process was repeated some 45 times. With the pipes then in sections, the way was clear to strip off the ground-surface and remove the sections, piece by piece.”

The project, part of RSRL’s ongoing programme to clean up and restore its Dorset site on behalf of the NDA, involved removing concrete base slabs for cooling towers and two pipelines which linked the reactor to the cooling towers. Demolition work was led by KDC, the term contractor responsible for demolitions at both RSRL Winfrith and Harwell.

A prototype power reactor, the pioneering SGHWR has been Winfrith’s most recognised landmark reactor for many years, operational from 1968 until 1990. The reactor cooling towers themselves were demolished in the early 1990s. The two pipelines comprised a ‘suction’ line and a ‘return’ line, and ran at a depth of four metres below ground, between the reactor and the old cooling-tower bases, a distance of some 240 metres. Their removal forms one of the final tasks in the latest phase of the extensive SGHWR clean-up programme.

Various options for cutting up the 1.57m and 1.93m diameter pipes were considered. In the end, KDC employed specialist high-pressure water-jetting company, RGL. In coming to this decision, safety was the top priority, however it also proved to be a quick, straightforward and highly effective solution for dealing with the pipeline removal works.

“The technique was safe, fast and used the minimum of water”, Mike added. “It was so successful, the pipeline project was completed in just a month, a week ahead of schedule, and to cost. Work on removing and crushing the concrete base slabs associated with the former cooling-towers also proceeded well and was completed a week later. We encountered no problems at all with the cutting operation and are extremely pleased with the way the project worked out – this is definitely a technique that we would consider using again.”