Session: 21-08 Field Service and Modernization

Paper Number: 102578

102578 - Condenser Retrofit in Leibstadt Nuclear Power Plant (Bwr) - Far Beyond a Standard Modular Solution 

The Leibstadt nuclear power plant (KKL) in Switzerland was originally commissioned in 1984 with a nominal power output of 1000 MW_el. After more than three decades of plant operation and subsequent to several power uprates of the boiling water reactor (BWR) up to 1275 MW_el, the original condenser had been affected by locally advanced erosion corrosion due to aging and by progressive performance deterioration. In addition, the thermal power uprates were resulting in load reduction during hot summer periods due to the high condenser back pressure.

GE were asked to carry out a comprehensive retrofit study and identified major improvements on lifetime and performance related aspects: such as a robust material selection considering cycle chemistry and cobalt limitations, an optimized extraction of non-condensable gases by means of a bespoke air cooler section of the condenser, applying GE Steam Power’s latest innovative tube pattern design aligned to BWR and optimizing the condensation area as well as steam flow paths.

However, site related challenges did not allow the realization of a typical modular condenser retrofit as the local access in the machine house is very restricted in space and modifications on concrete walls of the radiation shielding had to be avoided. Based on a close cooperation between KKL and GE Steam Power, a customized retrofit concept could be finally developed, resulting in prefabricated semi-modular skeleton structures and a rebuild of the new condenser on-site.

This paper provides details on the design solution, particularly the improvements which are specific to condensers operating in a BWR plant. Prior to the retrofit, preparatory and complementary refurbishment work was executed at the system interfaces, as well as replacement of strongly eroded condenser neck parts, an out-side reinforcement of the condenser walls and modifications at the continuous tube cleaning system. The construction site work itself covered proper safety measures, a complex logistics of work processes, the development of specific installation tools as a handling and turning device for the skeleton modules and compliance with adequate treatment of contaminated material.

In total, approximately 475 tons of old condenser material have been dismantled, 24 new skeleton semi-modules have been installed, a condenser with almost 52’000 tubes has been rebuilt on-site and 8 waterboxes have been replaced by an improved design made of stainless steel. More than 350 professionals contributed to the successful retrofit with an overall site effort reaching in total 270’000 working hours – all without any major accident. Close and efficient cooperation between an experienced and knowledgeable customer and the OEM supplier with their expertise in engineering and construction during all project phases, including a very detailed planning and preparation period, has been a key success factor of the retrofit.

The condenser installation could be completed within the planned outage schedule. All guaranteed performance parameters have been reached. The condenser with a church-window based tube pattern operates far beyond HEI performance requirements even under the challenging conditions of a BWR environment with the high amount of radiolysis gases.

During the first year of operation with the new condenser, the former summer load reductions could be eliminated. At design conditions a power increase of 10 MWel has been achieved, and at higher cooling water inlet temperatures there is even a significant additional power output gain. With this condenser retrofit, the nominal power output of nuclear power plant Leibstadt has been uprated to 1285 MWel.

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Presenting Author: Hartwig WOLF GE Steam Power Switzerland GmbH

Presenting Author Biography: To follow. Presenting author might be subject to change.

Authors:

Hartwig WOLF GE Steam Power Switzerland GmbH
Arthur Wettstein GE Steam Power Switzerland GmbH
Robert Faltermeier GE Steam Power Switzerland GmbH
Peter Graf Kernkraftwerk Leibstadt AG
Daniel Schupp Kernkraftwerk Leibstadt AG