PVC Tape Induced Stress Corrosion Cracking Test and Estimation of Cracking Potential of Every Pipes

摘要

The morphology of cracks, the chemical adhesions on the cracks, large residual stresses in pipes, and the location of cracks restricted to pipes of short hot water flow were reported in the previous paper. It was also found that the temperature depending peaks in chloride production was caused by the properties of FeCl_3. Semi-quantitative expression of the chloride production was proposed. A four points bending stress test was performed on the steel plates with the baked on PVC tape in humid air at 80 deg C. It is found that the baked PVC tape is the most harmful in 50 percent humid air, and its harm is same as NaCl in 100 percent humid air. The highest possible stress in pipes and the highest possible atmospheric temperature surrounding pipes is estimated to be 200MPa and 40 deg C, respectively. By taking both temperature- and stress- dependences into consideration, the SCC curve relating PVC-tape-induced-contamination for pipes in stagnant was established. Under the assumption of linear damage rule in stress corrosion cracking phenomena, damage to be accumulated in 60 years to pipes with fluids of various temperature and duration were calculated and a damage contour was graphed with a fluid temperature ordinate and a flow duration abscissa. The fluid conditions of major pipes at the Ikata-1 nuclear power plant, which had not received the full inspection, were positioned on so low area on the damage contour that the plant was estimated to be safe for the coming forty years.