Atomic Energy of Canada Ltd (AECL) is celebrating an important milestone in Candu 6 reactor refurbishment: the removal and replacement of calandria tubes, pressure tubes and end fittings at Korea's Wolsong 1.
AECL was contracted by Korea Hydro and Nuclear Power (KHNP) to retube the reactor in 2006 and the work began on the project in 2009. All 380 calandria tubes, which house the reactor's fuel channels and through which heavy water coolant circulates, have been removed and replaced in work which should enable the 679 MWe reactor to operate for a further 25 years. The entire project is scheduled to take 55 months to complete.
Each calandria tube is made of zirconium alloy and is approximately 6 metres long and 13 cm in diameter. Heavy water coolant is circulated between the reactor and the steam generators through the end fittings on the reactor's fuel channel assemblies. The first-of-a-kind refurbishment project has involved the development of hundreds of specialised tools and systems, according to AECL.
AECL president and CEO Hugh MacDiarmid praised the achievement as an important step towards completing the project. "This success marks the first time a Candu 6 reactor has had all of the fuel channels removed and replaced," he noted.
The next stage of work at Wolsong will be managed jointly by AECL and KHNP and will involve the removal of the multi-tonne tooling systems and the work platforms supporting them before feeder installation begins. The reactor expected to return to service for in time for summer 2011.
Candu reactors are designed to undergo refurbishment after approximately 25 years of operation, requiring a major outage but allowing reactor life to be extended by up to 30 years. For the more modern Candu 6s this involves complete retubing. AECL is currently also working on a similar refurbishment project at Canada's Point Lepreau, although that project has been running well over budget and behind schedule. Lessons learned from Point Lepreau have been invaluable for the refurbishment of Wolsong, however, and with the design also in operation in Argentina, Romania and China, the experience will benefit future projects.
Researched and written
by World Nuclear News