Stress-corrosion crack initiation behavior of carbon steel in simulated BWR environment

Book · Sat Dec 31 04:00:00 EST 1994

OSTI ID:70098

Nakanishi, Koki; Tanaka, Yasuhiro; Yoshida, Kazuo ^[1]; Nakayama, Guen; Akashi, Masatsune ^[2]

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1. Ishikawajima-Harima Heavy Industries Co. Ltd., Yokohama (Japan). Nuclear Power Division
2. Ishikawajima-Harima Heavy Industries Co., Ltd., Tokyo (Japan). Research Inst.

Carbon steels and low-alloy steels are said to possess, even though susceptible to stress-corrosion cracking themselves, conspicuously longer life than weld-sensitized Type 304 stainless steels in actual boiling water reactor (BWR) primary coolant environments of high-temperature, high-purity water containing some dissolved oxygen. This has been examined for a carbon steel pipe material and its weld by conducting uniaxial constant-load tests as a laboratory accelerated test. By statistically analyzing the distribution of stress-corrosion cracking lifetimes and metallographical examining the features of stress-corrosion crack initiation in an SEM, following results have been obtained: (1) the stress-corrosion cracking lifetime obeys the exponential distribution model; (2) stress-corrosion cracks are initiated at the bottom of corrosion pits, and it appears possible to analyze their initiation conditions in terms of stress-intensity calculated regarding the pit as a sharp crack; (3) the microcracks as initiated at the corrosion pit are non-propagative per se, so that it is only when they have grown into a main crack by coalescence with nearby microcracks that steady propagation becomes possible; and (4) both the process of pit initiation and that of microcrack coalescence can be described as a Poisson stochastic process just as for the stainless steels in the same environment, so that the whole process of stress-corrosion crack initiation can be conceived as consisting of these two independent Poisson stochastic processes connected in serial succession.

• OSTI ID: 70098
• Report Number(s): CONF-940222--
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
36 MATERIALS SCIENCE
BWR TYPE REACTORS
CARBON STEELS
CHEMICAL COMPOSITION
CRACK PROPAGATION
EXPERIMENTAL DATA
LOW ALLOY STEELS
MATHEMATICAL MODELS
MECHANICAL PROPERTIES
PITTING CORROSION
REACTOR MATERIALS
SCANNING ELECTRON MICROSCOPY
STRESS CORROSION
STRESS INTENSITY FACTORS
WELDED JOINTS