The Reactor Pressure Vessel (RPV) is an essential component, which is liable to limit the lifetime duration of PWR plants. The assessment of defects in RPV subjected to pressurized thermal shock (PTS) transients made at an European level generally does not necessarily consider the beneficial effect of the load history (Warm Pre-stress, WPS). The SMILE project — Structural Margin Improvements in aged embrittled RPV with Load history Effects — aims to give sufficient elements to demonstrate, to model and to validate the beneficial WPS effect. It also aims to harmonize the different approaches in the national codes and standards regarding the inclusion of the WPS effect in a RPV structural integrity assessment. The project includes significant experimental work on WPS type experiments with C(T) specimens and a PTS type transient experiment on a large component. This paper deals with the results of the PTS type transient experiment on a component-like specimen subjected to WPS- loading, the so called Validation Test, carried out within the framework of work package WP4. The test specimen consists of a cylindrical thick walled specimen with a thickness of 40mm and an outer diameter of 160mm, provided with an internal fully circumferential crack with a depth of about 15mm. The specified load path type is Load-Cool-Unload-Fracture (LCUF). No crack initiation occurred during cooling (thermal shock loading) although the loading path crossed the fracture toughness curve in the transition region. The benefit of the WPS-effect by final reloading up to fracture in the lower shelf region, was shown clearly. The corresponding fracture load during reloading in the lower shelf region was significantly higher than the crack initiation values of the original material in the lower shelf region. The post test fractographic evaluation showed that the fracture mode was predominantly cleavage fracture also with some secondary cracks emanating from major crack.

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Safe operation, availability and lifetime assessment of piping are of utmost concern for plant operators. The knowledge on how failures in piping and its support construction are reflected in changes of the dynamic behavior (eigen-frequencies, -modes and damping) is a useful basis for System Identification and Structural Health Monitoring (SHM). Modal analysis of complex piping, the identification of system changes and the use of vibration dampers in piping still constitute challenges. In this study three different piping systems are investigated: 1. In the first piping system at a chemical plant, which is supported by a tall steel structure fixed at the base, piping-elbow forces at the top of the building cause large vibration amplitudes. Tuned mass dampers (TMD) for minimizing vibration amplitudes were first tested in the laboratory of MPA Stuttgart and then designed for the piping system in the plant for preventing failures. 2. Another piping system is reported that is excited at resonance frequency to cause failure due to in-plane bending in an elbow with local wall thinning. 3. Finally, a large piping system at a lignite power plant is investigated under ambient vibration to detect changes in boundary conditions. Experimental Output Only Modal Analysis (OOMA) and Operational Modal Analysis (OMA), FE-model studies and model-updating are performed. Changes in the natural frequencies and corresponding mode shapes due to through-wall cracks or changing boundary conditions were observed.

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Hinterschnittdübel werden in kerntechnischen Anlagen zur nachträglichen Befestigung von maschinentechnischen Komponenten an Stahlbetontragwerken eingesetzt. Um die Integrität der Komponenten auch bei außergewöhnlichen Einwirkungen wie Erdbeben zu garantieren, müssen die Dübel eine ausreichende Tragfähigkeit aufweisen. Für die Annahme einer ausreichend starren Befestigung müssen darüber hinaus bleibende Dübelverschiebungen in engen Grenzen gehalten werden, da Dübelverschiebungen unmittelbaren Einfluss auf die Lastverteilung und ‐übertragung der Rohrhalterungen haben. Zum Nachweis von Tragfähigkeit und Verschiebungsverhalten von sicherheitstechnisch wichtigen Dübelbefestigungen werden Zulassungsversuche nach europäischen und deutschen Richtlinien bei unterschiedlichen Belastungen und bei unterschiedlichen Rissbreiten bzw. Risskollektiven durchgeführt. Um die Übertragbarkeit des Verschiebungsverhaltens bei Zulassungsversuchen auf realitätsnahe Belastungsbedingungen zu überprüfen, werden Ergebnisse von Zulassungsversuchen und Ergebnisse von großmaßstäblichen Erdbebenversuchen miteinander verglichen.