In order to predict a time to failure of plant components due to stress corrosion cracking
(SCC), crack initiation and growth behavior must be understood. The crack growth
behavior is generally investigated using a pre-cracked specimen, and the relationship
between stress intensity factor (SIF) and crack growth rate is quantified according to fracture
mechanics. In nuclear power plants, this relation has been utilized to evaluate growth
behavior of cracks detected in operating plants according to fitness-for-service codes [1,2].
On the other hand, it is difficult to grasp crack initiation behavior. Although various test
methods, such as a constant load test, an U-bend test, a CBB test [3], and a slow strain rate
test, have been used in investigating crack initiation, the results obtained by these tests
have not fully contributed to understanding of crack initiation process in nuclear power
plant. If an initiation time and a size of each crack under a specified stress and environmental
condition can be predicted, the failure time of large components in nuclear power
plants could be estimated by the crack growth model combined with the crack initiation
model.
In order to predict a time to failure of plant components due to stress corrosion cracking
(SCC), crack initiation and growth behavior must be understood. The crack growth
behavior is generally investigated using a pre-cracked specimen, and the relationship
between stress intensity factor (SIF) and crack growth rate is quantified according to fracture
mechanics. In nuclear power plants, this relation has been utilized to evaluate growth
behavior of cracks detected in operating plants according to fitness-for-service codes [1,2].
On the other hand, it is difficult to grasp crack initiation behavior. Although various test
methods, such as a constant load test, an U-bend test, a CBB test [3], and a slow strain rate
test, have been used in investigating crack initiation, the results obtained by these tests
have not fully contributed to understanding of crack initiation process in nuclear power
plant. If an initiation time and a size of each crack under a specified stress and environmental
condition can be predicted, the failure time of large components in nuclear power
plants could be estimated by the crack growth model combined with the crack initiation
model.
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