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Power plant piping system subjected to many cyclic loading conditions leads to fatigue loading and thereby crack initiation in the piping system. Demonstrating Leak-Before-Break (LBB) in the design stage itself plays an important role in ensuring the safety of the Sodium-cooled Fast Reactors (SFR) system. The design code guidelines as per RCC MRx A16 in LBB demonstration is conservative in nature. Conducting experiments for each size of the piping systems are expensive and time-consuming. In this paper present, the efforts taken to develop reliable numerical methods to demonstrate Fatigue Crack Growth (FCG). The geometries selected for the FCG analysis include both specimen level as well as full-scale component. The results show that KI estimate for the plate specimen increased with the increase of ‘a/t’ ratio up to 0.6 and then decreases, whereas, in case of the pipe bend, it reduced beyond the ‘a/t’ ratio of 0.4. This early reduction is due to the influence of global compressive stress present ahead of the crack growth. Thus, component level FCG simulation is essential for the accurate demonstration of LBB. FCG simulation has numerically demonstrated with better engineering accuracy for both specimen level as well as component level geometries

This paper describes a benchmark analysis that was performed to demonstrate numerical simulation capability on fatigue crack growth (FCG) behaviour under cyclic bending. Economic design of a piping system against the leak-before-break (LBB) criteria require an accurate estimate of crack growth behaviour. To this end, two representative geometries were selected. The first model was a plate-type geometry with a specimen-type feature, and the other model was a prototype pipe bend geometry with the component feature. The numerically simulated FCG behaviour was found to agree with published data within engineering accuracy for both the specimen-level and the component-level geometries. Details of the FCG simulation, its validation against benchmark data, and plausible reasons the difference observed in the FCG behaviour of the specimen-level and full-scale component-level geometries are presented in this paper. The results of the FCG simulation strengthen the argument for performing component-level FCG simulation for an accurate demonstration of LBB for the power plant piping systems. [ABSTRACT FROM AUTHOR]

An experimental study has been performed on a representative prototype-sized pipe bend made of SS 316 LN material to generate the relevant material parameters required for fatigue crack growth (FCG) simulation. Traditionally, FCG numerical simulation material parameters are generated based on specimen level test. In the literature there are many prototype pipe bend test results can be found. However, this paper takes a new look for generating FCG material parameters based on prototype-sized pipe bend test results. A semi-elliptical shaped pre-cracked pipe bend is used for the crack growth studies. Advancement of the crack profile has been measured in a periodic interval of cyclic testing, and the essential crack dimensions are derived to extract the FCG material parameters. FCG response curve derived, based on the prototype sized pipe bend test result, is well below the similar response curve obtained from the conventional material properties. The major reason behind this difference in FCG response is attributed to the influence of the residual stress locked during pipe bend fabrication. Based on these findings, it is recommended to adopt the material parameters derived based on the component-level test for more accurate prediction. Further studies are required to generalise the role of fabrication assisted effects in the material parameters in the case of prototype sized components. • Fatigue crack growth (FCG) experiments on a full-scale prototype-sized SS 316 LN pipe bend have been conducted. • Advancement of the crack profile is measured at periodic intervals and the required crack growth data is extracted. • Material parameters required for FCG simulation are derived based on the test data and FCG response is computed. • This response is compared with those computed based on conventional material parameters. • An approach for predicting a realistic FCG response of power plant piping components is proposed. [ABSTRACT FROM AUTHOR]