Project Description

Replacement of two Steam Generators

The Beznau Nuclear Power Plant unit I in north-east Switzerland was commissioned in 1969. For power uprating reasons the owner of the plant decided in 1988 to have the two steam generators replace in 1993.

The transport itself, until the steam generators were placed on sliding tracks, was operated by a consortium. From there, up to the final placement inside the containment, VSL was responsible. This included detail planning of movement, design, supply, erection and dismantling of temporary steel structures. Each steam generator is weighing 205 t and is 18 m long. The planning was very difficult because of various restrictions, geometrical conditions and a necessary extensive risk analysis and contingency planning. Particularly in view of the fact that the rigging operation had to start with the old radioactive steam generators.

The main hardware components were: sliding tracks, 2 sliding carriages, a tilting ring, 2 hook-up lifting beams and a central tower, acting as temporary polar crane support.

The actual exchange work started in April 1993. The generators were lifted on the sliding carriages by the consortiums winch system. Using the VSL strand pulling system, the steam generator was the moved through a temporary opening into the containment structure. After hooking up with the VSL lifting equipment on top of the polar crane, the steam generator was  tilted up by alternate lifting and sliding steps. Special attention was given to the final step from "near vertical" to "free hanging". The steam generator was then lifted to enable the bottom end to pass over the housing wall.

Working around the clock, the rigging operation was carried out over 8 days, well ahead of the orginal schedule.

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