Structural Integrity of Penetration Nozzle of Reactor Pressure Vessel Head of PWR Plant

2008 ◽  
Author(s):  
Kiminobu Hojo ◽  
Naoki Ogawa ◽  
Yoichi Iwamoto ◽  
Kazutoshi Ohoto ◽  
Seiji Asada ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Field ◽  
Pressure Vessel ◽  
Structural Integrity ◽  
Complex Structure ◽  
Reactor Pressure Vessel ◽  
Reactor Pressure

A reactor pressure vessel (RPV) head of PWR has penetration holes for the CRDM nozzles, which are connected with the vessel head by J-shaped welds. It is well-known that there is high residual stress field in vicinity of the J-shaped weld and this has potentiality of PWSCC degradation. For assuring stress integrity of welding part of the penetration nozzle of the RPV, it is necessary to evaluate precise residual stress and stress intensity factor based on the stress field. To calculate stress intensity factor K, the most acceptable procedure is numerical analysis, but the penetration nozzle is very complex structure and such a direct procedure takes a lot of time. This paper describes applicability of simplified K calculation method from handbooks by comparing with K values from finite element analysis, especially mentioning crack modeling. According to the verified K values in this paper, fatigue crack extension analysis and brittle fracture evaluation by operation load were performed for initial crack due to PWSCC and finally structural integrity of the penetration nozzle of RPV head was confirmed.

Introduction of Warm Pre-Stress Concept in French RPV Structural Integrity Assessment: Part II — RSE-M Appendix

2016 ◽  
Author(s):  
Stéphane Marie ◽  
Stéphane Chapuliot ◽  
Dominique Moinereau ◽  
Malik Ait-Bachir ◽  
Clémentine Jacquemoud ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Pressure Vessel ◽  
Structural Integrity ◽  
Loading History ◽  
Main Criterion ◽  
Integrity Assessment ◽  
Service Operation ◽  
Reactor Pressure

A new appendix is introduced in the RSE-M code, devoted to in-service operation on PWRs, dealing with the assessment of a defect in the Reactor Pressure Vessel. This new appendix reflects the current French practice and introduces a second criterion to consider the Warm Pre-Stress (WPS) effect. This appendix is applicable to under clad defects and defects partially in the cladding, and covers nominal, incidental and accidental conditions. The main criterion is the classical comparison between the stress intensity factor (amplified to account for the plasticity of the cladding) and the material toughness (taking into account the irradiation induced ageing). For incidental and accidental situations, if the conventional criterion is not verified, an alternative criterion is proposed to take into account the WPS effect. The criterion corresponds to the ACE criterion developed by AREVA, CEA and EDF taking into account the effective material toughness depending on the loading history. The present paper presents this new RSE-M appendix and provides some basic elements of justification and validation on the ACE criterion.

Research on the Fracture Mechanics Analysis Method for Reactor Pressure Vessel Nozzle Corner Flaw

2017 ◽  
Author(s):  
Shen Rui ◽  
Cao Ming ◽  
He Yinbiao ◽  
Tao Hongxin
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Pressure Vessel ◽  
Solution Method ◽  
Reactor Pressure Vessel ◽  
Design Code ◽  
Outlet Nozzle ◽  
Reactor Pressure

This paper has discussed the stress intensity factor solution method of most popular used nuclear equipment design code and published papers. A series of inlet and outlet nozzle of reactor pressure vessel 3-D FEA fracture mechanics models with different size of corner flaw are created by ABQUAS software. Moreover, the crack front has been specially processed by ZENRCAK software. By compare the stress intensity factor solutions of FEA method and the solutions of influence function method for a 1/4 infinite symmetry plate, the influence functions for PWR reactor pressure vessel inlet and outlet nozzle corner flaw solution are obtained.

Evaluation of Pressure-Temperature Limit Curve Considering Revised Stress Intensity Factor Method

2020 ◽  
Author(s):  
Yunjoo Lee ◽  
Hyosub Yoon ◽  
Kyuwan Kim ◽  
Jongmin Kim ◽  
Hyunmin Kim
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Pressure Vessel ◽  
Temperature Limit ◽  
Reactor Pressure Vessel ◽  
Flaw Size ◽  
Limit Curve ◽  
Asme Code ◽  
Reactor Pressure

Abstract Pressure-Temperature limit methodology is based on the rules of Appendix G in Section XI of the ASME Code in accordance with the requirements of 10 CFR 50, Appendix G, and the Appendix G in Section XI method refers to Welding Research Council (WRC) Bulletin 175 (WRC175). Flaw size is an important factor to protect the reactor pressure vessel from brittle failure but is not explicitly documented in WRC175. However, according to the recent change of Appendix G, the ¼ thickness (¼T) flaw size is postulated in the surface of the nozzle inner corner for the evaluation of Pressure-Temperature limit. In this paper, stress intensity factor is computed by using 3D finite element analysis (FEA) considering ¼T corner cracks of inlet nozzle and outlet nozzle in reactor pressure vessel. The result is compared with the stress intensity factor using influence function in the ASME Code. The results of stress intensity factor in accordance with the ASME Code are more conservative than those of the 3-D FEA with a crack. The allowable pressure and operation region in Pressure-Temperature limit curve are affected by the calculation methods of stress intensity factor.

The Favorable Effect of Autofrettage on Uniform Arrays of 3-D Unequal-Depth Cracks in a Thick-Walled Cylindrical Pressure Vessel

2003 ◽  
Author(s):  
M. Perl ◽  
B. Ostraich
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Field ◽  
Pressure Vessel ◽  
Crack Depth ◽  
Favorable Effect ◽  
Residual Stress Field ◽  
Cylindrical Pressure Vessel

The favorable effect of autofrettage on the mode I stress intensity factor (SIF) distributions along the fronts of radial, semi-elliptical surface cracks pertaining to large uniform arrays of unequal-depth cracks emanating at the bore of a pressurized thick-walled cylinder is studied. The analysis is based on the, previously proposed, “two-crack-depth level model”. SIF values are evaluated by the finite element method (FE) using the ANSYS 6.1 code. In the FE model singular elements are employed along the crack front and an equivalent temperature load simulates the autofrettage residual stress field. The distribution of KIN = KIP + KIA, the combined stress intensity factor due to pressurization and full autofrettage, for numerous uneven array configurations bearing n = n1 + n2 = 8 to 128 cracks, a wide range of crack depth to wall thickness ratios, a1/t = 0.01 to 0.4, and various crack ellipticities, a1/c1 = 0.3 to 1.5, are evaluated for a cylinder of radii ratio Ro/Ri = 2. The accuracy of the evaluated SIFs is increased using an improved displacement extrapolation. The results clearly indicate the favorable effect of the residual stress field on the fracture endurance and the fatigue life of autofrettaged cylindrical pressure vessel bearing uniform arrays of 3-D unequal-depth cracks emanating from its inner bore. This favorable effect is governed by Ψ = σo/p — the ratio of the vessel’s material yield stress to its internal pressure. The higher ψ is the more effective autofrettage becomes. The “interaction range” for the various configurations of uneven crack arrays is evaluated. The range of influence between adjacent cracks on the maximal combined SIF, KNmax, is found to be dependent on the density of the array, as reflected in the inter-crack aspect-ratio, as well as on the cracks’ ellipticity.

3-D Stress Intensity Factors due to Autofrettage for an Inner Radial Lunular or Crescentic Crack in a Spherical Pressure Vessel

2015 ◽  
Author(s):  
M. Perl ◽  
M. Steiner ◽  
J. Perry
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Field ◽  
Pressure Vessel ◽  
Bauschinger Effect ◽  
Three Dimensional ◽  
Residual Stress Field ◽  
Spherical Pressure

Three dimensional Mode I Stress Intensity Factor (SIF) distributions along the front of an inner radial lunular or crescentic crack emanating from the bore of an autofrettaged spherical pressure vessel are evaluated. The 3-D analysis is performed using the finite element (FE) method employing singular elements along the crack front. A novel realistic autofrettage residual stress field incorporating the Bauschinger effect is applied to the vessel. The residual stress field is simulated in the FE analysis using an equivalent temperature field. SIFs for three vessel geometries (R0/Ri=1.1, 1.2, and 1.7), a wide range of crack depth to wall thickness ratios (a/t=0.01–0.8), various ellipticities (a/c=0.2–1.5), and three levels of autofrettage (e=50%, 75%, and 100%) are evaluated. In total, about two hundred and seventy different crack configurations are analyzed. A detailed study of the influence of the above parameters on the prevailing SIF is conducted. The results clearly indicate the possible favorable effect of autofrettage in considerably reducing the prevailing effective stress intensity factor i.e., delaying crack initiation, slowing crack growth rate, and thus, substantially prolonging the total fatigue life of the vessel. Furthermore, the results emphasize the importance of properly accounting for the Bauschinger effect including re-yielding, as well as the significance of the three dimensional analysis herein performed.

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