The Leibstadt nuclear power plant (KKL) in Switzerland was originally commissioned in 1984 with a nominal power output of 1000 MWel. Since then, there have been several uprates of the boiling water reactor (BWR) which have increased the power to 1275 MWel.

After the nearly four decades of operation, the original condenser was impacted by advanced erosion corrosion and by progressive performance deterioration. In addition, the thermal power uprates required load reduction during hot summer periods to avoid high condenser back pressure.

Consequently, KKL asked GE to carry out a comprehensive retrofit study to identify potential improvements on both lifetime and performance. These included: robust material selection, optimized extraction of non-condensable gases by means of a bespoke air cooler section of the condenser and applying GE Steam Power's latest innovative tube pattern design which is aligned to BWR requirements.

However, site constraints prevented a typical modular condenser retrofit. Hence, working in a close cooperation between KKL and GE Steam Power, a customized retrofit concept was developed which used semi-prefabricated skeletal modules and an on-site rebuild of the condenser.

In total, approximately 475 tons of old condenser material were dismantled, 24 new semi-prefabricated skeletal modules were installed, a condenser with 51'600 tubes was rebuilt on-site and 8 waterboxes were replaced with an improved design made of stainless steel. More than 350 professionals contributed to the successful retrofit with an overall site effort of 270'000 working hours - increasing the power output to 1285 MWel.

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