Periodic Reporting for period 1 - DELISA- LTO (DELISA-LTO: DEscription of the extended LIfetime and its influence on the SAfety operation and construction materials performance – Long Term Operation with no compromises in the safety)
Période du rapport: 2022-06-01 au 2023-11-30
As many of the reactors are approaching the designed lifetime, the current global trend of nuclear power plants (NPP) operators is an extension of the plant lifetime above the design. The requirement is the knowledge of the actual technical state and material degradation as well as credible prediction of the material properties changes, so-called ageing, of the safety-related component (SRC) up to an extended lifetime. Responding to this need, the DELISA-LTO project aims to determine the most affected and threatened components from the point of view of the long-term operation (LTO) and describe the effect of the LTO on the material properties as well as develop a simulation tool able to predict the non-acceptable state of the material. The outputs of the project will lead to an increase in operational safety at the extended lifetime due to the in-time prediction of potential failure. The focus is on LWR technologies in general and specifically on the VVER (Water-Water Energetic Reactor) type reactors due to the consortium composition. Partners cover the majority of regions operating VVER reactors which are considered the most distributed reactor type in the world.
The industrial relevance, impact and subsequent exploitation potential of the DELISA-LTO project are extremely high mainly due to the participation of key industrial partners, a unique opportunity to obtain real data from operating components of decommissioned European power plants and to obtain relevant information on the impact of the design lifetime operation to SRC degradation and commitment for rapid usage of project results. The strategy included in the Dissemination and Exploitation plan includes the harmonization of new design and operating conditions, operating limits and improved safety criteria suggested as resulting from research activities, the development of improved methodologies and provision of the technical basis for design and assessment of reliable NPPs, the adoption of a harmonization strategy with smooth and efficient methods to enlarge progressively the field of consensus among stakeholders, link to the national as well as international professional or international organizations - some of them gather the operators (FORATOM, WANO), others illustrate the safety efforts (WENRA, AEN/CSNI, ETSON), but especially SNETP/NUGENIA and EERA JPNM.
The goal of DELISA-LTO project is to provide a comprehensive description of degradation mechanisms that affect selected components, such as steam generator tubes and primary pipes utilizing materials obtained from decommissioned NPP. The decommissioning of two V1 units in Slovakia presents a unique chance to study materials obtained in real operational conditions (app. 28-29 campaigns). Various components within the primary circuit exhibit distinct degradation mechanisms, leading to diverse changes in material properties. Consequently, different types of test methodologies, including Non-Destructive Testing (NDT) methods, structural and substructural analysis, and mechanical testing, are needed for evaluation. The integration of simulation tools and experimental techniques, such as mechanical testing and NDT inspection methods, is crucial for comprehending thermal ageing and swelling phenomena. Harvested materials mainly consist of primary circuit components such as main circulation piping and pressurizer surge line, predominantly composed of stainless steels.
The industrial relevance, impact and subsequent exploitation potential of the DELISA-LTO project are extremely high mainly due to the participation of key industrial partners, a unique opportunity to obtain real data from operating components of decommissioned European power plants and to obtain relevant information on the impact of the design lifetime operation to SRC degradation and commitment for rapid usage of project results. The strategy included in the Dissemination and Exploitation plan includes the harmonization of new design and operating conditions, operating limits and improved safety criteria suggested as resulting from research activities, the development of improved methodologies and provision of the technical basis for design and assessment of reliable NPPs, the adoption of a harmonization strategy with smooth and efficient methods to enlarge progressively the field of consensus among stakeholders, link to the national as well as international professional or international organizations - some of them gather the operators (FORATOM, WANO), others illustrate the safety efforts (WENRA, AEN/CSNI, ETSON), but especially SNETP/NUGENIA and EERA JPNM.
The goal of DELISA-LTO project is to provide a comprehensive description of degradation mechanisms that affect selected components, such as steam generator tubes and primary pipes utilizing materials obtained from decommissioned NPP. The decommissioning of two V1 units in Slovakia presents a unique chance to study materials obtained in real operational conditions (app. 28-29 campaigns). Various components within the primary circuit exhibit distinct degradation mechanisms, leading to diverse changes in material properties. Consequently, different types of test methodologies, including Non-Destructive Testing (NDT) methods, structural and substructural analysis, and mechanical testing, are needed for evaluation. The integration of simulation tools and experimental techniques, such as mechanical testing and NDT inspection methods, is crucial for comprehending thermal ageing and swelling phenomena. Harvested materials mainly consist of primary circuit components such as main circulation piping and pressurizer surge line, predominantly composed of stainless steels.
The work to be done within the project is divided into 6 work packages. Two of them are supportive. WP1 is dedicated to project coordination and management whereas WP6 focuses on the communication, dissemination and exploitation activities with attention to young researchers' involvement.
The work in WP2 included preparatory activities, the creation of a material database, sampling of materials from primary pipes in NPP V1, development of detailed cutting plans, primary sampling, and transportation to all participating entities. Up to now, all transports have been successfully executed, and the verification of the material volume for the specified range of tests outlined in the agreed experimental matrix is in progress.
The WP3 aims to develop, test and validate models of RPV internals to ensure their integrity and functional capability and evaluation of current and predictable state over the long-term operation, the models of thermal ageing is considered as well. Within the reporting period, the tasks were directed to get corresponding achievements for the defined aim. The survey of definition and comparison of normative requirements, current practice and approaches to the thermal ageing definition was developed.
WP4 creates a solid and reliable basis of experimental data to foster the project goals and activities in other WPs. In the first period, preparatory activities were carried out providing the basis for the implementation into the key area of the project - the experimental program in the form of an extensive inter-laboratory study using a wide range of experimental and analytical methods – mechanical testing, microstructural examinations, post-test analyses and NDT techniques. The experimental material matrix, describing the involvement of each participating laboratory, was finalized and the manufacture of the testing specimen has already started.
Within WP5, the safety guidelines related to the available SSCs’ materials which could affect the safe LTO will be analyzed. A Questionnaire and Survey of the used guidelines, standards, codes and "best practices" was designed and completed by the participants to create a robust base for the analysis. The questionnaire was approved by all participants and covered the following topics: safety codes, standards, guidelines related to the available SSCs' relevant for swelling and thermal ageing during LTO expected for 60+ years, best practice recommendations for swelling and thermal ageing assessment.
The work in WP2 included preparatory activities, the creation of a material database, sampling of materials from primary pipes in NPP V1, development of detailed cutting plans, primary sampling, and transportation to all participating entities. Up to now, all transports have been successfully executed, and the verification of the material volume for the specified range of tests outlined in the agreed experimental matrix is in progress.
The WP3 aims to develop, test and validate models of RPV internals to ensure their integrity and functional capability and evaluation of current and predictable state over the long-term operation, the models of thermal ageing is considered as well. Within the reporting period, the tasks were directed to get corresponding achievements for the defined aim. The survey of definition and comparison of normative requirements, current practice and approaches to the thermal ageing definition was developed.
WP4 creates a solid and reliable basis of experimental data to foster the project goals and activities in other WPs. In the first period, preparatory activities were carried out providing the basis for the implementation into the key area of the project - the experimental program in the form of an extensive inter-laboratory study using a wide range of experimental and analytical methods – mechanical testing, microstructural examinations, post-test analyses and NDT techniques. The experimental material matrix, describing the involvement of each participating laboratory, was finalized and the manufacture of the testing specimen has already started.
Within WP5, the safety guidelines related to the available SSCs’ materials which could affect the safe LTO will be analyzed. A Questionnaire and Survey of the used guidelines, standards, codes and "best practices" was designed and completed by the participants to create a robust base for the analysis. The questionnaire was approved by all participants and covered the following topics: safety codes, standards, guidelines related to the available SSCs' relevant for swelling and thermal ageing during LTO expected for 60+ years, best practice recommendations for swelling and thermal ageing assessment.
Experimental evaluation of design materials towards the long-term operation of VVERs is extremely important for the NPP's lifetime prolongation and increase in their safety margin. European VVER countries previously considered prolonging the operating lifetime from 40 to 60+ years keeping regularly updated high safety standards during the last decades. During the first 18 months of its implementation, project DELISA-LTO collected a great number of specimens coming from different VVERs. Measurements of VVER design material specimens via several techniques as received, irradiated as well as thermally treated will provide a unique set of results that will be relevant not only for VVERs but also PWRs operating in Europe. Several additional spectroscopic techniques will contribute to better understanding of degradation processes in material microstructure after long-term operational loads. The high abundance of experimental data will imply excellent possibilities for further research with an impact on increasing nuclear safety.