Fast Reactors and Accelerator Driven Systems Knowledge Base

Conference Article: Thermomechanical and fracture mechanics analysis on a tee junction of LMFR secondary circuit due to thermal striping phenomena

Kasahara, N. (O-arai Engineering Center (Japan))

Abstract

Structural analysis has been conducted concerning a tee junction of the Phenix secondary circuit due to thermal striping phenomenon, in the IAEA coordinated research programme on 'Harmonization and validation of fast reactor thermomechanical and thermohydraulic codes and relations using experimental data'. Under the boundary condition provided from thermohydraulic analysis with DINUS-3, BEMSET, and AQUA codes, possibility of crack initiation and propagation was assessed, by two different approaches. One is a simplified analysis approach based on the Structural Response Diagram proposed in this study. The other is a detailed analysis method with the Finite Element structural analysis code FIN AS and the Fracture Mechanics analysis code CANIS. When taking into account of attenuation factors of temperature fluctuation, calculated results indicate that cracks hardly initiate at base metal portions. On the other hand, strength of welded joint is reduced mainly by peak stress concentration at penetration beads, so that there is possibility of crack initiation within several thousands hours at the welded joint. According to fracture mechanics analysis, crack propagation rate is sensitive to mean stress and low frequency fluctuation. If there exist sufficient mean stress and low frequency components of temperature fluctuation, cracks will pass through the secondary circuit pipe wall.

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key words: benchmarks; crack propagation; codes; finite element method; fluid mechanics; mechanical properties; phenix reactor; pipes; secondary coolant circuits; stress analysis; temperature dependence; thermal analysis; thermal stresses; welded joints
Reference:
Final report of a co-ordinated research project 1996-1999
International Atomic Energy Agency, Vienna (Austria)
IAEA-TECDOC--1318, pp:89-116