ISSN:
1013-9826
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
A primary water stress corrosion cracking (SCC) and an outside diameter SCC haveoccurred in the steam generator (SG) tubes of nuclear power plants around the world. It is importantto establish the repair criteria for the degraded tubes to assure a reactor integrity, and yet maintainthe plugging ratio within the limits needed for an efficient operation. For assessment andmanagement of the degradation, it became crucial to understand initial leak behaviors under a smallpressure and leak rate evolution under a constant pressure of SCC flaws. Stress corrosion crackedtube specimens were prepared by using a room temperature cracking technique, and leak behaviorsof these tubes were measured at room temperature. Water pressure inside the tube was increasedslowly in a step like manner with a designated holding time. Water leak rates just after a ligamentrupture were measured by collecting the leaked water in a plastic container for a designated time. Aleak rate was calculated by dividing the amount of water by the time. Under 3.45 MPa, a smallwater droplet was formed, but it did not grow after a 10 minute holding period at a constantpressure of 3.45 MPa. A throughwall crack seemed to open at around 8.28 MPa (1200 psi). Sometubes with 100 % through wall cracks did not show a leakage at 10.8 MPa, which is a typicalpressure difference of pressurized water reactors (PWRs) during a normal operation. The higher thepressure was applied, the larger the rates of increase with the time were. Axial cracks showed alower leak pressure than that of the circumferential cracks, which might be from a higher hoopstress than the axial stress. A large open and long axial crack showed an increasing leak rate withthe time at a constant pressure
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/01/54/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.345-346.1345.pdf
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