Technical basis for normal water chemistry guidelines: Review of laboratory studies of water chemistry effects on SCC (stress corrosion cracking) Page: 2 of 11
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TECHNICAL BASIS FOR NORMAL WATER CHEMISTRY GUIDELINES--REVIEW OF
LABORATORY STUDIES OF WATER CHEMISTRY EFFECTS ON SCC*
T. F. Kassner, P. S. Maiya, J. Y. Park,
W. E. Ruther, W. J. Shack, and W. K. Soppet
Materials and Components Technology Division
Argonne National Laboratory
Argonne, Illinois 60439
SUMMARY
The influence of dissolved oxygen, hydrogen, and various impurity anions
on the stress corrosion cracking (SCC) susceptibility of sensitized Type 304
stainless steel (SS) and alternative piping materials such as Types 316NG and
347NG SS is being investigated in constant-extension-rate-tensile (CERT) tests
and in cyclic loading experiments on fatigue precracked fracture-mechanics-
type specimens at 2890C. In these experiments, the crack growth behavior of
the materials is being correlated with the impurity concentration and the
electrochemical potentials of Type 304 SS and platinum electrodes in simulated
BWR normal operating environments (-200-300 ppb oxygen and (100 ppb of various
oxyanions or halides added as acid or salts, at a total conductivity of <1 PS/cm).
Results from the CERT experiments on lightly sensitized Type 304 SS
specimens indicate that sulfur species (viz., sulfate) produced the highest
degree of intergranular stress corrosion cracking (IGSCC) in terms of the
crack growth rate and morphology of the fracture surface. CERT experiments on
Type 316NG and 347NG SS specimens indicate that these steels are susceptible
to ransgranular stress corrosion cracking (TGSCC) at strain rates of <5 x
10 s- in environments containing -200 ppb oxygen and (100 ppb sulfate.
Under analogous test conditions, the transgranular crack growth rates of these
materials were a factor of -8 lower than the intergranular rate for sensitized
Type 304 SS.
Long-term fracture-mechanics crack growth experiments were performed
within the range of normal BWR chemistry on Types 304 and 316NG SS and a weld
overlay specimen under low-frequency, high-R loading at a moderate stress
intensity. In the first experiment, crack growth in two sensitized Type
304 SS specimens virtually ceased upon removal of sulfate from the feedwater
and resumed when sulfate was added, whereas a solution-annealed specimen
cracked at the same rate whether or not sulfate was present in the environ-
ment. In a similar experiment with Types 304 and 316NG SS, the lightly
sensitized Type 304 specimen again responded in a favorable manner when
sulfate was removed from the feedwater (conductivity -0.1 pS/cm), but crack
growth in the Type 316NG specimen continued at the same rate as in the
impurity environment (-0.9 pS/cm). In the test on an overlay specimen
(fabricated from a sensitized Type 304 SS 10-in.-dia., schedule 140 pipe with
ER 308L SS weld metal), the crack grew to the overlay, branched at 900 along
the weld interface (parallel to the nominal applied load), and traveled a long
distance (-12 mm) in each direction.
The laboratory SCC studies indicate that all the materials exhibit a low
degree of tolerance to impurities in simulated normal BWR environments.
*Work supported by the U. S. Nuclear Regulatory Commission under Interagency
Agreement DOE 40-550-75.
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Kassner, T. F.; Maiya, P. S.; Park, J. Y.; Ruther, W. E.; Shack, W. J. & Soppet, W. K. Technical basis for normal water chemistry guidelines: Review of laboratory studies of water chemistry effects on SCC (stress corrosion cracking), article, October 1, 1986; Illinois. (https://digital.library.unt.edu/ark:/67531/metadc1408327/m1/2/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.