NRU Vessel Repair and Return to Service: Enhancing a Canadian R & D Asset for the Future

Abstract

The National Research Universal (NRU) reactor was successfully returned to high power operation in 2010 August, after completing extensive inspections and repairs of the calandria vessel, in response to a small leak of heavy water that was discovered in 2009 May. The aluminum alloy vessel material had corroded from the outside surface over many years, and required application of weld build-up and plated weld repair at ten locations, executed by remote tooling deployed from inside the reactor vessel. Many specialized remotely operated tools were developed for inspection, sampling and repair operations. In parallel with the repair efforts, important maintenance activities were performed, enabled by the de-fuelled state with the heavy water drained from the vessel. Two annual inspection cycles have now been completed since the reactor was returned to high power operation, confirming the fitness of the vessel for continued operation. The NRU reactor is now entering its 56th year of operation and the current operating licence extends to 2016. Based on the outcome of a comprehensive Integrated Safety Review, AECL is continuing to implement major equipment upgrades and process improvements to support safe and reliable operation through 2021, for the benefit of Canadians and the world.