A method of strength assessment of WWER reactor internals by the criterion of stress corrosion cracking in irradiated austenitic steels

2012 ◽  
Vol 44 (2) ◽  
pp. 115-128 ◽  
Author(s):  
B. Z. Margolin ◽  
V. A. Fedorova ◽  
V. M. Filatov
2014 ◽  
Vol 115 (6) ◽  
pp. 586-599 ◽  
Author(s):  
Yu. I. Filippov ◽  
V. V. Sagaradze ◽  
V. A. Zavalishin ◽  
N. L. Pecherkina ◽  
N. V. Kataeva ◽  
...  

Author(s):  
C Priya ◽  
K. B. Rao ◽  
M. B. Anoop ◽  
N Lakshmanan ◽  
V Gopika ◽  
...  

Stress corrosion cracking (SCC) is an important degradation mechanism to be considered for failure assessment of nuclear piping components made of austenitic steels. In this paper, an attempt has been made to compute the failure probabilities of a piping component against SCC with time using Monte Carlo simulation (MCS) technique. The initiation and propagation stages of stress corrosion cracks are modelled using the general methodology recommended in PRAISE modified by using the recommendations given by ASM for more rational modelling of stress field around cracks for estimating their growth with time. Degree of sensitization, applied stress, time to initiation of SCC, initial crack length, and initiation crack growth velocity are considered as random variables. An attempt has been made to study the stochastic propagation of stress corrosion cracks with time, using MCS technique. The trend of the distribution of crack depths at the initial stages obtained from simulation are compared and is found to be in satisfactory agreement with the relevant experimental observations reported in the literature. The failure probabilities are computed using two different failure criteria, namely (a) based on net-section stress and detectable leak rate as recommended in PRAISE and (b) based on R6 approach (using R6-option 1 curve as the failure assessment diagram). The procedure presented in the paper is general and the usefulness of the same is demonstrated through an example problem.


Author(s):  
B. Z. Margolin ◽  
N. E. Pirogova ◽  
A. A. Sorokin ◽  
V. I. Kokhonov

This paper presents results of a corrosion cracking test of specimens of irradiated austenitic chromium- nickel steels of grades 321 (Kh18N10T), 316 (06Kh16N11M3) and 304 (02Kh18N9). Specimens were irradiated to different damage dose from 4.5 to 150 dpa. The tests were carried out in autoclaves in the water environment simulating a coolant of the first circuit of WWER reactors at temperatures of 290–315°С. The influence of the damage dose and the neutron energy spectrum on the tendency of steels to stress corrosion cracking (SCC) is analyzed. The dominant SCC mechanisms for various austenitic steels are determined. Loading modes effects on the SCC resistance of specimens irradiated to the same damage dose are compared.


2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Bin Gong ◽  
Yanping Huang ◽  
E. Jiang ◽  
Yongfu Zhao ◽  
Weiwei Liu ◽  
...  

Austenitic steel is a candidate material for supercritical water-cooled reactor (SCWR). This study is to investigate the stress corrosion cracking (SCC) behavior of HR3C under the effect of supercritical water chemistry. A transition phenomenon of the water parameters was monitored during a pseudocritical region by water quality experiments at 650°C and 30 MPa. The stress–strain curves and fracture time of HR3C were obtained by slow strain rate tensile (SSRT) tests in the supercritical water at 620°C and 25 MPa. The concentration of the dissolved oxygen (DO) was 200–1000  μg/kg, and the strain rate was 7.5×10−7/s. The recent results showed that the failure mode was dominated by intergranular brittle fracture. The relations of the oxygen concentration and the fracture time were nonlinear. 200–500  μg/kg of oxygen accelerated the cracking, but a longer fracture time was measured when the oxygen concentration was increased to 1000  μg/kg. Chromium depletion occurred in the oxide layer at the tip of cracks. Grain size increased and chain-precipitated phases were observed in the fractured specimens. These characteristics were considered to contribute to the intergranular SCC.


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