Abrasive-Waterjet Deep Kerfing and Waterjet Surface Cleaning for Nuclear Facilities

Abstract

A deep kerf tool was designed to cut through the thick, reinforced concrete structures of nuclear facilities to help make the decommissioning process more efficient. Abrasive-waterjet (AWJ) cutting technology is used as the basis of the system. The cutting tool has a rotary nozzle that directs a high-pressure AWJ in a circular pattern. The circular pattern and the angle of jet impact create a slot wider in diameter than the tool itself as the tool moves across the face of the concrete. This makes it possible to insert the tool into the slot and create a deep cut for each pass along it until the desired depth is reached. In this testing program, concrete as thick as 1.5 meters was cut through from one side. The cutting rate of the tool ranges from 0.2 to 0.6 m2/hr. The tool employs a computer-controlled traverse mechanism with a simple device that can detect obstacles, such as uncut reinforcing bars (rebar) or hard aggregate. An electronic sensor system to identify, in real-time, when rebar is being cut was developed and tested with good results. A cleaner/scarifier tool for removing the surface layers of contaminated concrete and decontaminating metal surface was also designed and tested. It uses ultrahigh-pressure waterjets mounted on a rotating arm to remove or clean the target surface. Concrete can be scarified to a depth of 7 mm at a rate of 11 m2/hr. Concrete and metal surfaces can be cleaned of paint and corrosion at a rate of 33 m2/hr. Spoils recovery using a shroud/vacuum system is more than 99 percent for each tool.