MORE POWER TO YOU: SURFACE PREPARATION OF PIPES IN NUCLEAR PLANTS

“I contacted them and discussed our potential application,” recalls Stoltz. “The engineering department made some recommendations and sent some different hone models. We installed a test facility, equipping it with the same size and type of pipe and conditions, although it wasn’t actually radioactive. After we started using the flexible hone we knew immediately that it was going to work, that it was exactly what we were looking for. Brush made some suggestions about the style and grit of the hone as well as the operating speed (rpm), because we needed to maintain a specific finish on the pipes.”

According to Mike Miller of BRM, such specific applications often require preliminary testing, which is routinely performed by his firm’s engineering department and surface finishing laboratory, which can recommend and perform evaluations on various types of hones and fixtures.

SAVING ON RAD WASTE
Because one of the secondary costs of nuclear plant water pipe decontamination is for the disposal of RAD (radioactive absorbed dose) waste, Stoltz was anxious to see how much of this could be eliminated by use of the flexible hone. Sandblasting and other mechanical methods of pipe decontamination produce a considerable amount of RAD waste above and beyond the oxide layer because the blast media becomes part of the waste. In addition, there is a need to decontaminate the blast tool itself because it, too, becomes contaminated while doing the decon work.

Since this ball-style hone uses no media other than the balls of grit on its filaments, the RAD waste and associated disposal costs are significantly reduced. Perhaps more important, the cleanup process itself is less rigorous, saving time and money. Plus, the low-cost tool is considered a disposable, so it requires no decontamination after use in a radioactive pipe.

EXPEDITING DECON
Aquilex WSI Nuclear Services (Atlanta, GA), a welding solutions provider for complex needs of major industries including the energy, petrochemical, steel and pulp & paper sectors, was one of the first contractors to use the flexible hone for removal of radioactive oxides from water pipes in nuclear power plants.

“Traditional removal of radioactive oxides takes a long time and can mean tens of thousands of dollars an hour,” says Mark Stoutamire, Aquilex engineering manager. “It also generates a lot of contaminated waste that has to be cleaned up and disposed of. With this ball-style hone you don’t have that added radioactive waste. And the work involved is only a fraction of the typical grinding or honing approach, which means that workers experience less exposure – and that also translated to major savings.”

Aquilex, which performs sophisticated projects all over the world, has used the flexible hone to decontaminate water pipes in nuclear plants located in Spain and the U.S.

“What initially led to our interest in the flexible hone was surface preparation of pipes we were going to repair by welding,” Stoutamire explains. “We could see that this tool could be lowered and controlled in such a way that it would remove material inside pipes workers could not reach. In some situations that may involve removing a layer of radioactive oxide, so we decided that would also be an excellent application for the tool.”