EDM used on live nuclear reactor pipeline

Machining specialist Hydratight says it has become the first company to use EDM for maintenance work on a live nuclear reactor pipeline system.
The company completed the technically challenging campaign for a major energy company at a US power station as part of post-Fukushima upgrades.

Using EDM avoided an expensive unplanned shutdown of the reactor, and took 48 hours off the reactor outage schedule.
The process used a heated solid electrode to cut a hole (featuring 0.05 mm tolerance) within the reactor feed water line. Microscopic cuttings were then removed using back-flushing and vacuums. Hydratight’s process prevented 99.5% of foreign material exclusion particles, such as drill cuttings and debris, from entering the reactor.
Mike Riordan, Hydratight’s nuclear speciality services manager, says: “This was a milestone achievement on a live nuclear reactor pipeline system, and resulted in safety enhancements in line with the industry’s post-Fukushima requirements. The work has created another way to feed water into the main line if there is ever a power loss to the reactor.”
The line had water pressure of 8.3 bar and electrical conductance exceeding 3,500 micro-siemens. Hydratight’s speciality services deployed customised tooling to negotiate a 380 mm long, 25 mm wide pipe as an entry point to reach the spot where the 19 mm EDM penetration was to take place.
“Material contaminations are a major concern for most facilities, and EDM is a highly accurate and safe way of machining,” says Riordan. “Tool pressure was also a concern on this particular project, so we were able to use a method which was completely contactless.”
Hydratight has offered its services to the nuclear and power-generation industries for more than 30 years.
For further information www.hydratight.com