Atomic Energy of Canada Limited (AECL) has reached an important milestone with the first successful completion in Wolsong, South Korea, of the removal and replacement of calandria tubes, pressure tubes and end fittings in a CANDU 6 nuclear reactor.

“This success marks the first time a CANDU 6 reactor has had all of the fuel channels removed and replaced,” says Hugh MacDiarmid, AECL’s President and CEO, “bringing us one step closer to completing the project and allowing the Wolsong reactor to continue building on its excellent operating performance record for another 30 years.”

AECL developed hundreds of specialized tools and systems for this first-of-a-kind groundbreaking work. The tools’ robotically driven movements are intricate and precise, and designed to be used in a radioactive environment.

AECL began work on the South Korean reactor in June 2009 to replace all 380 calandria tubes. Each calandria tube is approximately six metres long by 13 centimetres in diameter. Made of zirconium-alloy, the tubes house the reactor’s 380 fuel channels. The fuel channels connect to end fittings on each fuel channel assembly to circulate heavy water coolant between the reactor and steam generators.

“We have 170 Canadian employees working in Korea on the Wolsong project, and they are focused on successfully completing their work in a safe, professional, quality manner,” said Ramzi Fawaz, AECL Senior Vice-President of Operations. “Their experience gained at Wolsong will serve us well in delivering our current and future refurbishment projects.”

The next stage of work at Wolsong is to remove the multi-tonne tooling systems and the work platforms supporting them before feeder installation begins. This will be managed jointly by AECL and the client, Korea Hydro & Nuclear Power Company Ltd. (KHNP). The reactor is now on track to return to service for Korea’s summer peak demand next year.

AECL’s CANDU 6 (C6) design is a 700 megawatt (MW) class nuclear power reactor. Built in Canada, Argentina, China, Romania and South Korea, the C6 is one of the top performing reactor designs in the world, with an overall 88.6% lifetime capacity factor. There are four C6 units located in Wolsong. The first unit was built in 1983, with Units 2, 3 and 4 completed in 1997, 1998 and 1999 respectively. The four Korean units have an average lifetime capacity factor of 92.8%.