Working Group on Integrity of Components and Structures (IAGE)
Ageing management of thick-walled concrete structures, including in-service inspections maintenance and repair, instrumentation methods and safety assessment in view of long-term operation
Prague, Czech Republic
1-3 October 2008
The objective of this workshop is to present state-of-the-art techniques for the integrity assessment of concrete structures and to recommend areas in which further research is needed. Special emphasis will be given to performance-based in-service inspections (ISI) based on non-destructive evaluation (NDE) methods (such as impact echo, ultrasound and high frequency radar) and instrumentation. The limits of applicability will be extensively discussed. The management of ageing programmes based on suitable structural monitoring will also be addressed in the framework of a safety assessment of the installations in the long term. Probabilistic methods oriented towards the reliability of structural assessments will be compared and suggestions will be made for the consistent management of the integrity assessment of civil structures, both repairable and unrepairable.
The overall objective of the workshop is to address the present situation, regulatory, utility and industry aspects, as well as experiences and R&D activities in NEA member countries in this field. Information obtained from this workshop should provide understanding of the potential differences and discrepancies in present practices and propose methods to address them.
Background
The main purposes of nuclear power plant containments are to provide the final physical barrier to the release of fission products to the environment and to protect the reactor and other safety-related structures, systems and components.
Although, it was thought that concrete was maintenance free with a design life of hundreds of years, this has proved to be optimistic. Experience has demonstrated that concrete structures start to degrade after 20 years or even earlier. Concrete containments are subjected to many types of environmental effects that can degrade their structural integrity.
The safety significance of containment combined with the current trend towards life extension and regulatory authority demands for even higher levels of safety assurance means that ageing degradation must be effectively controlled. An important element of this control is inspection and monitoring to assess and determine the condition of the concrete structures and associated components.
The development priorities for NDE of concrete structures in nuclear power plants were identified during the 1997 CSNI/IAGE workshop on this subject. Since then nuclear power plant operators have recognised many challenges to maintenance, repair and the
long term operation
(LTO) aspects for their concrete structures. One of these is the ability to detect and predict the extent of internal damage and ageing effects. Modern NDE methods and instrumentation are thought to provide potentially useful techniques for the detection and measurement of the extent of internal damage and provide information on the construction quality.
Moreover, despite of the large choice of inspection techniques available, the engineering community still employs different practices in the management of concrete ageing, especially in the use of ISI, their integration with the safety assessment and their optimisation. This issue has become urgent in recent years, when the degradation mechanisms affecting concrete structures have shown their potential to jeopardise structural reliability, thereby challenging the safety of the installation.
The NEA Committee on the Safety of Nuclear Installations (CSNI) and its Working Group on Integrity of Components and Structures (IAGE WG) considered that there was a need to ensure that the methods used for the inspection and monitoring of safety critical containment structures are reliable and that their capabilities and limitations are properly understood. The overall objective of this workshop is to determine what additional information is needed to assure that non-readily replaceable components and structures (e.g., concrete structures) will retain their integrity and reliability during their projected years of service.
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