Probabilistic assessment of a reactor pressure vessel subjected to pressurized thermal shocks by using crack distributions

Abstract Probabilistic methods are used to analyze a reactor pressure vessel (RPV) subjected to pressurized thermal shocks (PTSs) initiated by a small loss-of-coolant accident (SLOCA) and a medium loss-of-coolant accident (MLOCA). The FAVOR code is applied to calculate the probabilities for crack initiation and failure by considering crack distributions based on cracks observed in the Shoreham and PVRUF RPVs in the U.S. The crack parameters, i.e. crack density, depth, aspect ratio, orientation and location are assumed as random variables following different distributions. The Vflaw code is used to generate FAVOR input files for the crack distribution data from the decommissioned plants. Weld type, size and its manufacturing process are also considered in the calculation. In this paper it is shown that the calculated failure probability of the RPV subjected to the SLOCA is higher than that subjected to the MLOCA due to different loading. The failure probabilities are compared with those based on a different crack assumption. Among the analyzed cracks, the embedded crack with a depth of 6.83 mm and surface crack with a depth of 5.13 mm result in the highest probability for failure. Maximum stress intensity factors of the simulated cracks range from 36 MPa m 0.5 to 91 MPa m 0.5 for the MLOCA and from 30 to 41 MPa m 0.5 for the SLOCA, respectively. We conclude that considering the observed crack distribution in probabilistic PTS analyses may lead to higher failure probabilities than by assuming cracks of specific size.

[1]  Guian Qian,et al.  Procedures, methods and computer codes for the probabilistic assessment of reactor pressure vessels subjected to pressurized thermal shocks , 2013 .

[2]  Markus Niffenegger,et al.  Probabilistic analysis of pipelines with corrosion defects by using FITNET FFS procedure , 2011 .

[3]  Shengjun Yin,et al.  Fracture Analysis of Vessels. Oak Ridge FAVOR, v06.1, Computer Code: Theory and Implementation of Algorithms, Methods, and Correlations , 2007 .

[4]  V. F. González-Albuixech,et al.  Integrity analysis of reactor pressure vessels subjected to pressurized thermal shocks by XFEM , 2014 .

[5]  Guian Qian,et al.  Probabilistic fracture assessment of piping systems based on FITNET FFS procedure , 2011 .

[6]  J. Newman,et al.  Stress-intensity factor equations for cracks in three-dimensional finite bodies subjected to tension and bending loads , 1984 .

[7]  R. D. Cheverton,et al.  OCA-P, a deterministic and probabilistic fracture-mechanics code for application to pressure vessels , 1984 .

[8]  Yinsheng Li,et al.  Development of a PFM code for evaluating reliability of pressure components subject to transient loading , 2001 .

[9]  Markus Niffenegger,et al.  The proper use of thermal expansion coefficients in finite element calculations , 2012 .

[10]  J. Strosnider,et al.  VISA: a computer code for predicting the probability of reactor pressure-vessel failure. [PWR] , 1983 .

[11]  Terry L. Dickson,et al.  An updated probabilistic fracture mechanics methodology for application to pressurized thermal shock , 2001 .

[12]  Nilsson Karl-Fredrik,et al.  NESC-IV Project: an Investigation of the Transferability of Master Curve Technology to Shallow Flaws in Reactor Pressure Vessel Applications - Final Report , 2005 .

[13]  Guian Qian,et al.  Integrity analysis of a reactor pressure vessel subjected to pressurized thermal shocks by considering constraint effect , 2013 .

[14]  Naoki Soneda,et al.  Benchmarking Studies of Probabilistic Fracture Mechanics Analysis Code, PROFMAC-II, for Assessing Pressurized Thermal Shock Events of Reactor Pressure Vessel Integrity Issues , 1996 .

[15]  Guian Qian,et al.  Deterministic and probabilistic analysis of a reactor pressure vessel subjected to pressurized thermal shocks , 2014 .