Project Report – Isolation of four Primary Circuit Feeder Pipes from the Steam Generating Heavy Water Reactor, Winfrith

January 5, 2017

Location: Winfrith

Project: Isolation of four Primary Circuit Feeder Pipes from the Steam Generating Heavy Water Reactor

Contractor: Magnox Limited (previously RSRL)

Equipment: SVI FOAMBAGS™, umbilical filling system, CCTV and closed cell polyurethane foam

Steve Vick International (SVI) has recently completed a project for Magnox Ltd. The project required SVI to design, test and install FOAMBAGS™ into four Primary Circuit Feeder Pipes attached to the Steam Generating Heavy Water Reactor (SGHWR) at Winfrith.

The operation was undertaken as part of a programme to decommission the cylindrical reactor (SGHWR) which comprises 100 channel tubes beneath, some of which contain Intermediate Level Waste (ILW).

Decommissioning the core involves elevating it which in turn presents the risk of ILW falling through the channel tubes. In most instances the ILW is too large to fall out; however, two types of ILW were small enough to fall through four of the channel tubes: the Pencil Loops (50kg) and Interstitial Shield Plugs (10kg).

To remove this risk, preparation work beneath the core was required and it was decided that the safest method was to use a physical plug to prevent any ILW or other debris falling out and through the four channel tubes. Magnox decided that the best and safest option for a physical plug was the SVI FOAMBAG™ system.

Magnox chose to use SVI’s expertise and the FOAMBAG™ system following the company’s successful record of providing similar solutions previously at Winfrith, as well as at Chapelcross, Harwell and Sellafield.

Well proven technique

The FOAMBAG™ system was first developed by SVI in the 1980s for flowstopping underground pipes in the safety critical gas distribution industry. For the past 20 years, the company has been working in the nuclear decommissioning and emergency repair sector where FOAMBAG™ technology has proved to be extremely effective in encapsulating and locking down loose contamination.