Periodic Reporting for period 4 - TeaM Cables (European Tools and Methodologies for an efficient ageing management of nuclear power plant Cables)
Periodo di rendicontazione: 2021-09-01 al 2022-08-31
The lifetime of existing nuclear power plants (NPPs) can potentially be extended to between 60 and 80 years if safety and operability of facilities can be guaranteed. With an average of total length of 1 500 km per nuclear power plant unit, all organisations involved in the current and next generation of NPPs have recognised the importance of cable qualification, condition monitoring, and ageing management. Cables, especially their insulation and jacket materials made of polymers, are vulnerable to ageing degradation during normal operation and accidents and means must be established to ensure that cable ageing does not lead to unsafe operation. Latest developments in polymer ageing research have revealed important limits in current methods for estimating the lifetime of NPP cables. These are related to the lack of representativeness of accelerated ageing and the lack of consideration of the polymer composition (e.g. fillers, antioxidants) in cable ageing models.
The main aim of TeaM Cables was to develop a multiscale approach for an accurate estimation of the cable lifetime. The project analysed the effects of irradiation and temperatures on cables from micro- to macroscale level to develop multiscale models of ageing. Ageing in both normal operation conditions and accidental conditions were addressed. The multi-scale and kinetic models produced by the project were to be integrated into an open access tool – the TeaM Cables tool – which is built on the merger of a currently used European cable management tool with a cable ageing modelling tool. In parallel, criteria and protocols for on-site use of non-destructive testing techniques were to be proposed. The aim is to allow NPP operators to safely extend the plant life duration of generation II and III reactors thanks to the TeaM Cables multiscale modelling approach and associated tools, and thus contribute to the production of sustainable energy responding to future energy needs.
The main aim of TeaM Cables was to develop a multiscale approach for an accurate estimation of the cable lifetime. The project analysed the effects of irradiation and temperatures on cables from micro- to macroscale level to develop multiscale models of ageing. Ageing in both normal operation conditions and accidental conditions were addressed. The multi-scale and kinetic models produced by the project were to be integrated into an open access tool – the TeaM Cables tool – which is built on the merger of a currently used European cable management tool with a cable ageing modelling tool. In parallel, criteria and protocols for on-site use of non-destructive testing techniques were to be proposed. The aim is to allow NPP operators to safely extend the plant life duration of generation II and III reactors thanks to the TeaM Cables multiscale modelling approach and associated tools, and thus contribute to the production of sustainable energy responding to future energy needs.
Numerous model materials have been produced with different geometries, from tapes to cables, to ease the interpretation but also to remain as close as possible to the application. Experiments have been done under various conditions and temperatures, both in normal and accidental conditions. In comparison with the initial plan, more samples have been aged in more ageing conditions, and more measurements have been carried out; thus, increasing the scientific scope of the project.
All the characterisations were carried out at the different scales showing some unexpected results as the presence of antioxidant crystals. Thanks to this extensive database, kinetic models have been established for some materials considering fillers and antioxidant contributions for XLPE material. Difficulties were faced with a primary antioxidant within the material, notably due to the additional stabilizing effect of antioxidant crystals on the sample surface. Correlations have been highlighted between the changes in the dielectric and mechanical properties and changes in oxidation markers.
Based on this relationship, a multi-scale modelling has been suggested. This approach is very promising but needs to be challenged on fully formulated materials.
An open access tool has been set up integrating the multiscale models and providing the residual lifetime of cables knowing material data and the exposure conditions. The distribution of the TeaM Cables tool to the partners and end-user group has been done through workshops. The end-user group could satisfactorily test the tool and check the transposability of the models developed on data coming from in-service cables or from databases of previous projects.
In addition, six different non-destructive tests or micro-sampling techniques were further set up during the project. For each testing method, the measurement procedures have been further developed in a more detail level, some of them can be considered now to be verified in lab conditions and ready to be demonstrated in an on-site environment.
In parallel to the progress of scientific activities, the TeaM Cables consortium has also performed many dissemination activities to raise awareness of the project. The project has continued to be active in dissemination during the overall project duration by publishing 38 peer-reviewed papers and by participating to 16 scientific conferences.
All the characterisations were carried out at the different scales showing some unexpected results as the presence of antioxidant crystals. Thanks to this extensive database, kinetic models have been established for some materials considering fillers and antioxidant contributions for XLPE material. Difficulties were faced with a primary antioxidant within the material, notably due to the additional stabilizing effect of antioxidant crystals on the sample surface. Correlations have been highlighted between the changes in the dielectric and mechanical properties and changes in oxidation markers.
Based on this relationship, a multi-scale modelling has been suggested. This approach is very promising but needs to be challenged on fully formulated materials.
An open access tool has been set up integrating the multiscale models and providing the residual lifetime of cables knowing material data and the exposure conditions. The distribution of the TeaM Cables tool to the partners and end-user group has been done through workshops. The end-user group could satisfactorily test the tool and check the transposability of the models developed on data coming from in-service cables or from databases of previous projects.
In addition, six different non-destructive tests or micro-sampling techniques were further set up during the project. For each testing method, the measurement procedures have been further developed in a more detail level, some of them can be considered now to be verified in lab conditions and ready to be demonstrated in an on-site environment.
In parallel to the progress of scientific activities, the TeaM Cables consortium has also performed many dissemination activities to raise awareness of the project. The project has continued to be active in dissemination during the overall project duration by publishing 38 peer-reviewed papers and by participating to 16 scientific conferences.
With the TeaM Cables project results and experience, the way forward is to demonstrate the robustness of the developed approach on the real-scale cables and to move forwards the upscaling of the lab. developed tools to the field by delving the following topics:
• Degradation mechanisms understanding:
o Expertise on harvested cables from the NPPs
o Characterize different environment: combined effects of temperature and irradiation, influence of water
o Determine degradation kinetics of filled materials
• Modelling:
o Establish a kinetic modelling for a fully formulated material considering the thickness of the insulation layer (oxygen depletion and antioxidant diffusion)
o Generalize the multiscale modelling for materials with an increasing complexity, notably the structure/electrical property relationships
o Compare the multiscale approach to additional models (phenomenological, statistical)
o Crosscheck the prediction with data from continuous monitoring and in service inspections which allows for predictive maintenance
o Enrich the TeaM Cables tool to capitalize new models and integrate phenomenological model widely used
• Continuous monitoring:
o Some non-destructive tests set up needs to be verified in lab conditions and to be demonstrated in an on-site environment
o Use and develop sensors capable of directly measuring chemical aging tracers (e.g. oxidation, absorption of humidity, ...) whose value could directly be calculated by the kinetic model
These topics are considered of great importance by the TeaM Cables consortium for a wider and meaningful impact. It is necessary to keep the momentum created within the project to strengthen the European leadership and its supply chain regarding the cables are they are crucial components when it comes to ensuring the safety and reliability of the existing and future NPPs.
• Degradation mechanisms understanding:
o Expertise on harvested cables from the NPPs
o Characterize different environment: combined effects of temperature and irradiation, influence of water
o Determine degradation kinetics of filled materials
• Modelling:
o Establish a kinetic modelling for a fully formulated material considering the thickness of the insulation layer (oxygen depletion and antioxidant diffusion)
o Generalize the multiscale modelling for materials with an increasing complexity, notably the structure/electrical property relationships
o Compare the multiscale approach to additional models (phenomenological, statistical)
o Crosscheck the prediction with data from continuous monitoring and in service inspections which allows for predictive maintenance
o Enrich the TeaM Cables tool to capitalize new models and integrate phenomenological model widely used
• Continuous monitoring:
o Some non-destructive tests set up needs to be verified in lab conditions and to be demonstrated in an on-site environment
o Use and develop sensors capable of directly measuring chemical aging tracers (e.g. oxidation, absorption of humidity, ...) whose value could directly be calculated by the kinetic model
These topics are considered of great importance by the TeaM Cables consortium for a wider and meaningful impact. It is necessary to keep the momentum created within the project to strengthen the European leadership and its supply chain regarding the cables are they are crucial components when it comes to ensuring the safety and reliability of the existing and future NPPs.