Probability of Fracture for HFIR Pressure Vessel Caused by Random Crack Size or by Random Toughness

1994 ◽  
Vol 116 (1) ◽  
pp. 24-29 ◽  
Author(s):  
S.-J. Chang
Keyword(s):  
Fracture Toughness ◽  
Pressure Vessel ◽  
Crack Depth ◽  
Crack Size ◽  
Distribution Functions ◽  
Probability Curve ◽  
Pressure Pulses ◽  
Vessel Response ◽  
Point Pressure ◽  
Probability Of Fracture

The probability of fracture (or the fracture fragility) for a range of internal pressure-pulses for the HFIR pressure vessel is obtained. The fracture is assumed to be caused by randomly distributed cracks and by fracture toughness of variable magnitudes. The probability curve is applied to estimate the vessel fracture strength against the pressure-pulses of hypothetical accident. Both the crack population and the fracture toughness are assumed to be random variables of given distribution functions. Possible hoop stress is based on the numerical solution of the vessel response after a point pressure-pulse is applied at the center of the reactor vessel. The fluid-structure interaction and radiation embrittlement are both considered in the analysis. Only elastic fracture mechanics is used. The probability of vessel fracture for a single crack caused by either a variable crack depth or a variable toughness is first derived. Then the probability of fracture with multiple number of cracks is obtained. The probability of fracture is further extended to include different levels of confidence and variability.

scholarly journals A Local Approach to Assess Effects of Specimen Geometry on Cleavage Fracture Toughness in Reactor Pressure Vessel Steels

2018 ◽  
Author(s):  
Diego F. B. Sarzosa ◽  
Rafael Savioli ◽  
Claudio Ruggieri ◽  
Andrey Jivkov ◽  
Jack Beswick
Keyword(s):  
Fracture Toughness ◽  
Cleavage Fracture ◽  
Pressure Vessel ◽  
Crack Tip ◽  
Crack Size ◽  
Size Ratio ◽  
Additional Contribution ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Shallow Crack

This work presents recent improvements in the micromechanical failure criterion based on the Weibull stress (σw) concept for prediction of cleavage fracture in ferritic steels. The model is applied in SE(B) specimens extracted from an ASTM A533 pressure vessel steel having different levels of stress triaxiality at the crack tip. Nonlinear 3D finite element models with dimensions matching the tested specimens were built to provide the necessary crack tip stresses at the fracture process zone for calculation of the σw-J evolution from wich the variation of characteristic toughness values (J0) between different cracked geometries can be estimated. Application of this methodology for the material used at this study is able to predict J0 for SE(B) specimens with very shallow crack size ratio a/W = 0.05, short crack a/W = 0.2 and deep crack a/W = 0.4. The reported fracture toughness values for specimens having very shallow crack size ratio is an additional contribution of this study.

Use of Local Approach for Prediction of the Irradiation Effect on Fracture Toughness of Pressure Vessel Steel

2011 ◽  
Vol 465 ◽  
pp. 568-573
Author(s):  
Sergiy Kotrechko ◽  
Sergii Mamedov ◽  
Ivo Dlouhy ◽  
Vladislav Kozák
Keyword(s):  
Fracture Toughness ◽  
Pressure Vessel ◽  
Fracture Probability ◽  
Irradiation Effect ◽  
Pressure Vessel Steel ◽  
Local Approach ◽  
Vessel Steel ◽  
Reactor Pressure Vessel Steel ◽  
Probability Of Fracture ◽  
Reactor Pressure

Possibility of use of Local Approach (LA) to prediction of the effect of neutron irradiation on the fracture toughness of pressure vessel steel is discussed. The fundamental of new version of LA to fracture is briefly stated. Specific feature of this version of LA is that Weibull distribution is not used for description of distribution function of fracture probability. Probability of fracture is estimated by modeling of regularities of the crack nucleus formation and instability in polycrystal. Findings on simulation of fracture of reactor pressure vessel steel 2Cr-Mo-V in initial and irradiated states are presented.

Testing of Fracture Toughness Under Biaxial Loading

2005 ◽  
Author(s):  
Milan Brumovsky ◽  
Dana Lauerova ◽  
Jiri Palyza
Keyword(s):  
Fracture Toughness ◽  
Pressure Vessel ◽  
Biaxial Loading ◽  
Crack Depth ◽  
Pressure Vessels ◽  
Operating Conditions ◽  
Testing Equipment ◽  
Life Assessment ◽  
Biaxial Tests ◽  
Reactor Pressure

Reactor pressure vessels under some special regimes (i.e. pressurized thermal shock) are loaded by a strongly biaxial tensile stresses whose ratio can reach even an opposite value in comparison with normal operating conditions. Pressure vessel integrity as well as its life assessment is performed on the basis of fracture mechanics where normally only uniaxial fracture toughness of materials are used as material inputs. Special biaxial tests on cruciform type specimens with thickness up to 90 mm were tested in Nuclear Research Institute (NRI) Rez - special testing equipment and testing methods including measurements have been developed and realized. Testing equipment with maximum loading up to 1.5 MN allows to reach different biaxial loading ratios between 0 and 2. During tests, carried out mostly at low temperatures, specimens deflections, strains, load and crack opening displacement are measured and then evaluated. In NRI Rez comparative experimental tests on cruciform and beam specimens were performed. The aim of these tests was to examine the effect of crack depth and biaxial loading on fracture toughness for reactor pressure vessel material 15Kh2MFA. For evaluating the tests, the FEM (program SYSTUS) was used. The performed tests confirm shallow crack effect, i.e. increase of fracture toughness for shallow cracks compared to that one of deep cracks. Further, the performed experiments show decrease of fracture toughness of shallow cracks loaded biaxially compared to uniaxial loading of shallow cracks. Quantitatively, the fracture toughness decrease was about 20%.

Fatigue life analysis of pressure vessel based on residual strength and crack size

2021 ◽  
Author(s):  
Mengyu Zhu ◽  
Xintian LIU ◽  
Jiafeng Lai ◽  
Jiao Luo
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Residual Strength ◽  
Pressure Vessel ◽  
Residual Life ◽  
Crack Depth ◽  
Circumferential Stress ◽  
Crack Size ◽  
Pressure Vessels ◽  
The Relationship

In the field of pressure vessel fatigue life, the study of fracture failure is very important. Based on the Paris law, the relation model between fatigue crack size and residual fatigue life is established by considering the circumferential stress. The relationship between the crack length and the crack depth is introduced. According to the specific structure of the pressure vessel, the relationship model between the fatigue crack size and the residual strength is established based on the residual strength allowable value. The S-N curve of pressure vessel is obtained based on two models. The fatigue life of the pressure vessel is predicted combined with the actual test data. By comparing with the actual service life, the feasibility of the model is verified, which provides a new method for predicting the residual life of pressure vessels.

scholarly journals Probabilistic Assessment of Crack Failure of Reactor Pressure Vessel (RPV) Cladding Material

2018 ◽  
Vol 41 (2) ◽  
pp. 237-245
Author(s):  
Shamsul Huda Sohel ◽  
Md Al Amin Hossain ◽  
Debashis Datta ◽  
Md Fazlul Huq
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Crack Propagation ◽  
Pressure Vessel ◽  
Crack Size ◽  
Reactor Pressure Vessel ◽  
Initiation Point ◽  
Probabilistic Fracture Mechanics ◽  
Final Crack ◽  
Reactor Pressure

To design a Reactor Pressure Vessel (RPV), material property like crack must be considered as it is an unavoidable property of materials. Presence of crack in materials must be kept within limit to prevent material’s failure. So, crack propagation must be analyzed and observed. In this paper, crack propagation due to stress and materials fracture toughness of reactor pressure vessel cladding has been observed to estimate cumulative probability of crack failure using Probabilistic Fracture Mechanics (PFM). Average crack size is guessed as 3 mm and geometry factor is considered as 1.12 to analyze edge crack. Final crack analysis range has been found to be 1.8 mm with crack propagation rate of ± 30% of its average size. Variation of critical crack size and crack initiation point for several design stresses and fracture toughness has been investigated with probabilistic fracture mechanics technique. The observed crack propagation by calculating final crack size and the cumulative crack failure probability of the reactor pressure vessel materials are presented in this work.Journal of Bangladesh Academy of Sciences, Vol. 41, No. 2, 237-245, 2017

CARELSO 60/65

Alloy Digest ◽  
2011 ◽  
Vol 60 (10) ◽  
Keyword(s):  
Fracture Toughness ◽  
Tensile Properties ◽  
Pressure Vessel ◽  
Heat Treating ◽  
Steel Alloy ◽  
Vessel Material ◽  
Sour Service

Abstract CarElso 60/65 is a steel alloy with special melt practice producing a pressure vessel material with resistance to mild sour service. This datasheet provides information on composition and tensile properties as well as fracture toughness. It also includes information on forming, heat treating, and joining. Filing Code: SA-635. Producer or source: Industeel USA, LLC.

The method for calculating the probability of brittle destruction of NPP equipment in different operating modes with postulated defectiveness

2021 ◽  
Vol 14 (1) ◽  
pp. 34-39
Author(s):  
D. A. Kuzmin ◽  
A. Yu. Kuz’michevskiy
Keyword(s):  
Fracture Toughness ◽  
Pressure Vessel ◽  
Nuclear Power ◽  
Power Plants ◽  
Reactor Pressure Vessel ◽  
Practical Significance ◽  
Reactor Unit ◽  
Operating Modes ◽  
Brittle Destruction ◽  
Reactor Pressure

The destruction of equipment metal by a brittle fracture mechanism is a probabilistic event at nuclear power plants (NPP). The calculation for resistance to brittle destruction is performed for NPP equipment exposed to neutron irradiation; for example, for a reactor plant such as a water-water energetic reactor (WWER), this is a reactor pressure vessel. The destruction of the reactor pressure vessel leads to a beyond design-basis accident, therefore, the determination of the probability of brittle destruction is an important task. The research method is probabilistic analysis of brittle destruction, which takes into account statistical data on residual defectiveness of equipment, experimental results of equipment fracture toughness and load for the main operating modes of NPP equipment. Residual defectiveness (a set of remaining defects in the equipment material that were not detected by non-destructive testing methods after manufacturing (operation), control and repair of the detected defects) is the most important characteristic of the equipment material that affects its strength and service life. A missed defect of a considerable size admitted into operation can reduce the bearing capacity and reduce the time of safe operation from the nominal design value down to zero; therefore, any forecast of the structure reliability without taking into account residual defectiveness will be incorrect. The application of the developed method is demonstrated on the example of an NPP reactor pressure vessel with a WWER-1000 reactor unit when using the maximum allowable operating loads, in the absence of load dispersion in different operating modes, and taking into account the actual values of the distributions of fracture toughness and residual defectiveness. The practical significance of the developed method lies in the possibility of obtaining values of the actual probability of destruction of NPP equipment in order to determine the reliability of equipment operation, as well as possible reliability margins for their subsequent optimization.

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