Probabilistic Failure Analysis of Austenitic Nuclear Pipelines against Stress Corrosion Cracking

Abstract

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.

Determination of bounds on failure probability in the presence of hybrid uncertainties

“…For AISI 304 austenitic stainless steel, F has a mean of 2·551 and standard deviation of 0·4269, and G = 1·3447 (Harris et al 1992). From parametric studies carried out, a value of 5% coefficient of variation of log(v 1 ) was found to be critical to life of piping component (Priya et al 2005), and hence this value is used in this study. The procedure followed for transition from initiation to fracture mechanics crack growth rate in the present study is (Anoop et al 2008):…”

“…For AISI 304 austenitic stainless steel, C 12 = 0·8192, C 13 = 0·03621 and C 15 = 1·7935, mean value of C 14 = −3·1671 and standard deviation of C 14 = 0·7260 (Harris et al 1992). From a probabilistic failure analysis of austenitic nuclear pipe against SCC, Priya et al (2005) inferred that expressions given in PRAISE for computation of stress intensity factors for modelling crack propagation need modification. In Priya et al (2005), this modification has been introduced by using well-accepted expressions given in ASM, and with modified PRAISE approach, stochastic propagation of stress corrosion cracks with time has been studied.…”

“…From a probabilistic failure analysis of austenitic nuclear pipe against SCC, Priya et al (2005) inferred that expressions given in PRAISE for computation of stress intensity factors for modelling crack propagation need modification. In Priya et al (2005), this modification has been introduced by using well-accepted expressions given in ASM, and with modified PRAISE approach, stochastic propagation of stress corrosion cracks with time has been studied. It has been noted that trend of distribution of crack depths at initial stages is in satisfactory agreement with relevant experimental observations reported in literature (Priya et al 2005).…”

“…In Priya et al (2005), this modification has been introduced by using well-accepted expressions given in ASM, and with modified PRAISE approach, stochastic propagation of stress corrosion cracks with time has been studied. It has been noted that trend of distribution of crack depths at initial stages is in satisfactory agreement with relevant experimental observations reported in literature (Priya et al 2005). Hence, modified PRAISE approach proposed by Priya et al (2005) is followed in the present study.…”

Structural Reliability Improvement Using In-Service Inspection for Intergranular Stress Corrosion of Large Stainless Steel Piping

“…Rahman (Rahman S. 1997) has developed another computer code named PSQUIRT (probabilistic see page quantification of upsets in reactor tubes) to determine the probability of leak age of piping made of stainless steel and carbon steel subjected to intergranular stress corrosion cracking (IGSCC) and corrosion fatigue. Failure probabilities of a piping component subjected to SCC was computed in (Priya C et al, 2005and Guedri et al, 2009a, 2009b) using a Monte Carlo simulation (MCS) technique.…”