A New Stress Intensity Factor Solution Based on the Response Surface Method for Nozzle Corner Cracks in Nuclear Reactor for Thermal Energy Generation

Ting Jin,Yuebing Li,Zihang Wang,Pan Liu,Dasheng Wang,Zhibo He

doi:10.3389/fenrg.2021.801919

Abstract

As considered carbon-free, the use of nuclear energy for thermal energy generation may expand in the future, with the guarantee of safe operation of the nuclear reactor. In a nuclear reactor pressure vessel (RPV), the nozzle area is an important part of the safe operation. It bears internal pressure, axial force, and overall moment, and at the same time bears higher stress than the rest of the vessel. To assess the integrity of the nozzle structure with a crack under combined load, an accurate solution of stress intensity factors (SIF) along the crack front is necessary. To obtain the SIF, this paper proposes a solution method that uses the stress on the crack surface and the response surface method to fit the stress under the framework of the linear superposition technique. This method is the first choice to determine a series of influence coefficients under unit pressure load. Then, one can estimate the SIFs by superposition method for an arbitrary stress distribution resulted from combined loads. The proposed solution is verified for a typical RPV with cracks under internal pressure, axial force, and global bending moment. The results reveal that the proposed solution is in good agreement with the existing solutions under internal pressure. Therefore, it can be obtained that this solution can be effectively used for the structural integrity assessment of RPV with nozzle corner cracks.

Highlights

With the excessive use of fossil energy, the global greenhouse effect intensifies, which requires immediate action to reduce carbon emission (Sadekin et al, 2019)
To ensure the applicability of the stress intensity factor solution, this paper proposes a new stress fitting method based on multivariate to improve the solution, which is effective for both internal pressure load and complex combined load
This study examines the stress intensity factor (SIF) of nozzle corner crack based on the linear elastic fracture mechanics and linear superposition method (Shiratori and Miyoshi, 1986; Nagai et al, 2015)

Summary

Introduction

With the excessive use of fossil energy, the global greenhouse effect intensifies, which requires immediate action to reduce carbon emission (Sadekin et al, 2019). Being admitted as a carbon-free energy (Akhmat and Zaman, 2013; Gao et al, 2013), for emission reduction, nuclear energy has been used for thermal energy generation, which drives power generation, space heating, and desalination (Brook et al, 2014; Xu et al, 2021). As an important part of the nuclear reactor pressure vessel (RPV), ensuring the structural integrity of the RPV is the premise of the safe operation of nuclear power equipment. Due to the inconsistency of the local structure, the local stress level in the nozzle corner region may be extremely. Some specific analytical expressions have been established to determine the fracture parameters, such as stress intensity factor (SIF) and J-integrity, for applications in nuclear power plants. The applicability of the existing codes (ASME, 2010; British Energy, 2010) is limited to plates, elbows, and cylinders

Methods

Results

Conclusion