Title

Bruce Units A 1&2 SGR (EPC)

Excerpt

SNC-Lavalin Nuclear Inc. is in the final stages of the first ever steam generator replacement project in a CANDU nuclear power plant. The Contract was awarded in 2005,

Date

12/21/2007



SNC-Lavalin Nuclear Inc. is in the final stages of the first ever steam generator replacement project in a CANDU nuclear power plant. The Contract was awarded in 2005, and a detailed planning stage culminated in early site work starting in 2006. Most of the work was completed in 2007. The scope involved removal and replacement of a total of 16 steam generator sections from Bruce A, reactors 1 & 2. There are 4 reactors in total at the Bruce A plant. The steam generator geometry in the Bruce A plant is quite unique and challenging. Two sets of 4 lower steam generator sections are connected to horizontal steam drums in each reactor. After considering numerous possible approaches to the replacement, the selected method was to cut the lower sections from the drums, lift and relocate the drums within the reactor building, and then lift the lower steam generator sections out through the reactor building roof. A massive crane of 1800 tonne capacity was required for the project due to the combination of lift weights (the steam drums weighed 250 tonnes, the individual steam generator sections weighed 100 tonnes) and the distance the crane had to reach to perform the lifts.

One of the major challenges of the project involved the re-assembly of the systems after the new lower steam generator sections were ready to be lifted into place. The new sections had to align perfectly in 12 points; two nozzles for each lower steam generator section and four connections to each steam drum. In addition, each assembly had portions of it in three separate enclosures of the reactor building. Extremely precise laser measurement and computer analysis technology was developed and utilized to ensure that all parts would fit perfectly on first try. The job was a complete success, and first time alignment was achieved on each of four assemblies.

Other achievements on the job included removal and re-pouring of close to 900 tons of high density concrete shielding in the two reactor buildings, necessary to relocate the steam drums, a world-record low net radiation dose of only 41 man-rem in Unit 2, and critical replacement time on the second reactor cut to well under half the time taken for the first unit. With more than one million man-hours of work performed on the project, there were zero lost-time accidents and zero worker over-exposures to radiation. Final closing of the building roofs is underway and will be completed during 2008.