Stress corrosion cracking of zirconium alloys

Langmuir ◽  
1987 ◽  
Vol 3 (6) ◽  
pp. 867-873 ◽  
Author(s):  
B. Cox
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Zirconium Alloys ◽  
Corrosion Cracking

Iodine-Induced Stress Corrosion Cracking of Zircaloy-4: Identification of Critical Parameters Involved in Intergranular to Transgranular Crack Propagation

2011 ◽  
Vol 183 ◽  
pp. 49-56 ◽  
Author(s):  
Virginie Francon ◽  
Marion Fregonese ◽  
Hiroshi Abe ◽  
Yutaka Watanabe
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Hexagonal Lattice ◽  
Ductile Failure ◽  
Zirconium Alloys ◽  
External Pressure ◽  
Corrosion Cracking ◽  
Critical Parameters ◽  
Propagation Mode ◽  
Induced Stress

During power transient conditions in nuclear reactors, uranium oxide pellets expand and crack due to the increase in temperature and their poor thermal conductivity. Moreover, the cladding undergoes creep because of the external pressure, and its diameter shortens. These antagonistic phenomena lead to the establishment of a contact between the pellet and the cladding, called the pellet-cladding interaction. The synergistic effect of the hoop tensile stress and strain imposed on the cladding by fuel thermal expansion and corrosion by iodine released from the UO2 fuel as a fission product at the same time can lead to Iodine-induced Stress Corrosion Cracking (I-SCC) of the Zircaloy-4 cladding. I-SCC failures of zirconium alloys are usually described in three steps: initiation of cracks, intergranular subcritical propagation, and critical propagation with a brittle transgranular propagation mode [1]. Transgranular propagation occurs as soon as the stress intensity factor overshoots a threshold value KI,SCC. It is the critical step and leads to the final ductile failure of the cladding. Transgranular cracks propagate by cleavage-like fracture on basal planes of the hexagonal lattice and fluting; it is the result of a competition between a plastic accommodation of the applied strain and the brittle fracture of basal planes by iodine assisted cleavage.

In Situ SEM study of iodine-induced stress corrosion cracking (ISCC) in Zircaloy-4

1990 ◽  
Vol 48 (4) ◽  
pp. 840-841
Author(s):  
Marthinus P Fick
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Zirconium Alloys ◽  
Tensile Tests ◽  
Gauge Length ◽  
Argon Atmosphere ◽  
Corrosion Cracking ◽  
Outer Diameter ◽  
Mechanism Of Failure

Stress corrosion cracking (SCC) of Zirconium alloys by an abundant fission product, iodine, has been extensively studied in order to understand the mechanism of failure of fuel cladding in nuclear reactors. This study was an attempt to observe the fracture mechanics of ISCC in Zircaloy-4 during in situ scanning electron microscope (SEM) tensile tests.A 200mm long section of a Zircaloy-4 cladding tube with an outer diameter of 9’55mm and a wall thickness of 0,55mm, was bisected and then cold rolled into flat strips 14mm wide and 0,5mm thick. The material was annealed at 680°C for 1 h at a time in an Argon atmosphere between successive cold working steps. Following the final cold roll the material was annealed at 1080°C for 4 h in an Argon atmosphere and air-quenched.Tensile test specimens with a gauge length of 12’5mm and a width of 3’12mm were cut from the sheet metal by spark erosion accordinq to scaled down ANSI/ASTM E8-79a specifications. The specimens had to be lapped and polished to a thickness of 0’16mm in order to obtain a maximum stress of 500MPa without exceeding the 250N limit of the apparatus.

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