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Vol.4 No.4 previous AA-SP8(49-50-51-52-53-54-55-56-57-58)-NT 53 -54-55

Academic Articles
Regular Paper Vol.5No.1 (2013) p.15 - p.24
 

R&D to lifetime management – ND-characterization of ageing phenomena

 
Gerd DOBMANN1,*, Christian BOLLER1, Hans-Georg HERRMANN1, and Iris ALTPETER 1
 
1 Fraunhofer-Institute for Non-destructive Testing- IZFP,Campus E 3 1, Saarbrücken, 66123, Germany
 
Abstract
The contribution reports to R&D performed under the umbrella of the German Nuclear Safety Research Program in the last decade by the Fraunhofer-IZFP within the context of nondestructive materials characterization of materials ageing phenomena which can occur during the lifetime of a nuclear power plant. The Cu-rich low-alloy heat-resistant steel 15 NiCuMoNb 5 (WB 36, material number 1.6368) which is used as piping and vessel material in boiling water reactor (BWR) and pressurized water reactor (PWR) nuclear power plants in Germany was under special investigations. In all damage situations observed in plants, the operating temperature was between 320℃ and 350℃ and the damage was combined with a shift in the ductile-to-brittle-transition-temperature (ΔDBTT) of the notched-bar impact test to higher temperatures. Micromagnetic NDT techniques were applied to characterize the material degradation which is enhanced when low cycle fatigue loads are superimposed to the precipitation process of Cu-rich particles. As the essential results correlations were found between micromagnetic properties on one hand and microhardness and the Cu-content on the other hand.
As Cu-rich-precipitates play also an essential role in neutron embrittlement of pressure vessel material, the same NDT techniques were applied to predict ΔDBTT at irradiated Charpy specimen. Also here high correlations were found between the micromagnetic properties and the ΔDBTT with small residual standard error. Austenitic stainless steel AISI 321 is used in German plants as surge- and spray-pipeline material which under service is exposed to cyclic thermo-mechanical loads. The contribution documents the ability of ultrasonic time-of-flight measurements to sensitively characterize the whole fatigue life from the beginning to the end of life. As the experiments were performed at 300°C too, EMAT-transducers have been applied.
 
Keywords
Material degradation, ageing phenomena, thermal ageing, neutron embrittlement, low cycle fatigue
 
Full Paper: PDF EJAM Vol.5No.1 pp.15-24 "R&D to lifetime management –ND–characterization of ageing phenomena"

















Article Information
Article history:
Received 18 October 2012
Accepted 7 February 2013