Most of today's operating nuclear plants that were originally designed for 30 or 40-year life are facing the long-term operation issues. Therefore, it is of meaningful importance to assess the time-dependent degradation and the ageing of the relevant nuclear system, structure, and components (SSCs). Ageing (such as e.g. thermal fatigue, vibrational fatigue, thermal ageing, etc.) refers indeed to the change in mechanical and physical proprieties of such a type components and may result in loss of structural capacity. The paper deals with the assessment of a quite new methodology for estimating primary pipe performance in a typical PWR-II subjected to ageing mechanisms. In this framework, inverse method is implemented to the purpose starting from temperature at an accessible boundary, which are measured through a monitoring system. The used reconstruction technique uses the elaborated signal provided by the monitoring system to determine temperature at inaccessible surface: this is the so-called inverse heat transfer problem (IHTP). The inverse space marching method is applied. Analytical and numerical studies are performed, taking into account thermal transient conditions, in order to determine thermal loads. In particular, the developed code demonstrates to be able to reconstruct temperature and stress profiles in any section of the pipe with a good accuracy. In addition, the thermal loads obtained used for ageing analysis suggests that the investigated transient condition are not able to jeopardise the integrity of NPP. Results seems to confirm the performance of the pipeline and the possibility of the plant extension of life.


ICONE Competition - ICONE28-POWER2020-16129: Inverse Heat Conduction Problem in Estimating NPP Pipeline Performance

Division / Sponsors: 
Power Division & Nuclear Engineering Division (NED)

Power Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/POWER/POWER2020/volume/83747

International Conference on Nuclear Engineering
Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE2020/volume/83761

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