Irradiation Embrittlement Behavior of SA508 Gr.4N RPV Steel Model Alloy

2016 ◽  
Author(s):  
Min-Chul Kim ◽  
Bong-Sang Lee
Keyword(s):  
Fracture Toughness ◽  
Alloy Steel ◽  
Neutron Irradiation ◽  
Charpy Impact ◽  
Model Alloy ◽  
Low Alloy Steel ◽  
Irradiation Embrittlement ◽  
Master Curve Method ◽  
Rpv Steel ◽  
Curve Method

The mechanical properties and irradiation embrittlement behavior of SA508 Gr.4N low alloy steel have been characterized systematically using SA508 Gr.4N model alloys. For an evaluation of neutron irradiation embrittlement behavior of model alloy, several irradiation tests were carried out at the research reactors, HANARO and HBWR, up to a fluence level of 1.5 × 1020n/cm2 (E>1MeV) at 290 ± 10°C. The master curve method according to ASTM E1921 was adopted to evaluate the fracture toughness in the transition region. Ni and Cr additions resulted in increasing the martensite fraction in low alloy steel by enhancing the hardenability of the steel. Thus, the predominant microstructure of SA508 Gr.4N model alloy is a mixture of tempered martensite and bainite, while SA508 Gr.3 steel shows a typical tempered upper bainitic structure. SA508 Gr. 4N model alloy shows excellent strength and transition behavior compared to commercial SA508 Gr.3 steel. After neutron irradiation, the yield strength and tensile strength of model alloy were increased with an increase in the neutron fluence level. The transition temperature shifts of SA508 Gr.4N model alloy obtained by both Charpy impact and fracture toughness tests were not significantly larger than those of commercial SA508 Gr.3 low alloy steel. It seems that the increased Ni content in the SA508 Gr.4N model alloy did not show significant effects on the irradiation embrittlement behavior owing to the controlled low Mn content. In addition, good fracture toughness of the SA508 Gr.4N model alloy was maintained even after neutron irradiation up to a level of ∼1020n/cm2.

Applicability of Miniature C(T) Specimens for the Master Curve Evaluation of RPV Weld Metal

2015 ◽  
Author(s):  
Masato Yamamoto ◽  
Naoki Miura
Keyword(s):  
Fracture Toughness ◽  
Weld Metal ◽  
Master Curve ◽  
Master Curve Method ◽  
Rpv Steel ◽  
Steel Base ◽  
Toughness Evaluation ◽  
Curve Method ◽  
The Difference

The Master Curve approach for the fracture toughness evaluation is expected to be a powerful tool to ensure the reliability of long term used reactor pressure vessel (RPV) steels. In order to get sufficient number of data for the Master Curve approach coexistent with the present surveillance program for RPVs, the utilization of miniature specimens that can be taken from the broken halves of the surveillance Charpy specimens is important. CRIEPI has developed the test technique for the miniature C(T) specimens, whose dimensions are 4 × 10 × 9.6 mm, and has verified the basic applicability of the Master Curve approach by means of the miniature C(T) for the determination of the fracture toughness of typical Japanese RPV steel base metals [1]. A series of round robin tests on RPV steel base metals [2–4] demonstrated that the miniature C(T) specimen can be used for the determination of the reference temperature (To) with no specific difficulties in test techniques. The present paper addresses the applicability of the fracture toughness evaluation by the miniature C(T) specimens on a RPV weld metal with multi-layer weld bead structure. The distribution of the fracture toughness and the trend in fracture toughness change with temperature were confirmed to show a good agreement with the assumption of the Master Curve method [5]. Fracture surface of the specimens were in cleavage fracture mode regardless of the difference in fracture toughness level. The relevance of the specimen size correction in the Master Curve method was confirmed. The difference of To values were only in a few degrees Celsius between the data obtained with 0.5 inch-thickness C(T) specimens and the miniature C(T) specimens. The effect of local loss of constraint nearby the specimen side surface was examined by comparing with the datasets from the specimens with and without side grooves. The difference of To was only 3 degree centigrade and no remarkable effect of side grooving could be seen. From overall examination results, it was concluded that the miniature C(T) specimen can be used for the Master Curve evaluation of tested PRV weld metal.

Estimation of Q345R Fracture Toughness Based on Master Curve

2017 ◽  
Author(s):  
Lele Gui ◽  
Tong Xu ◽  
Binan Shou ◽  
Haiyang Yu
Keyword(s):  
Fracture Toughness ◽  
Transition Temperature ◽  
Master Curve ◽  
Charpy Impact ◽  
Tensile Tests ◽  
Empirical Formulas ◽  
Master Curve Method ◽  
Temperature Method ◽  
Single Temperature ◽  
Curve Method

1T CT specimens are used to evaluate the fracture toughness of Chinese Q345R steel in the ductile-brittle transition regime by Master Curve method. Tensile tests, Charpy impact tests and drop-weight tests of Q345R steel are also carried out to get the ductile-brittleness transition temperature and nil-ductility transition temperature. Master Curves are compared with the empirical formulas adopted in ASME, API and BS codes. Results show that the reference temperature T0 values derived from single-temperature and multi-temperature method by 1T specimen are basically consistent. Master Curve can well envelop the fracture toughness and temperature curves derived from the empirical formulas, and is more economic and flexible than the K1C curve with sufficient conservation.

scholarly journals Master Curve Fracture Toughness Characterization of Eurofer97 Using Miniature Multi-Notch Bend Bar Specimens for Fusion Applications

2018 ◽  
Author(s):  
Xiang Chen ◽  
Mikhail A. Sokolov ◽  
Yutai Katoh ◽  
Michael Rieth ◽  
Logan N. Clowers
Keyword(s):  
Fracture Toughness ◽  
Power Plants ◽  
Master Curve ◽  
Reference Temperature ◽  
Irradiation Damage ◽  
First Wall ◽  
Irradiation Embrittlement ◽  
Master Curve Method ◽  
Fusion Applications ◽  
Curve Method

Eurofer97 is one of leading candidates of reduced activation ferritic martensitic (RAFM) steels for first wall structural materials of early demonstration fusion power plants. During fusion plant operation, high neutron irradiation damage on first wall materials can cause irradiation embrittlement and reduce the fracture toughness of RAFM steels. Therefore, it is critical to select proper testing techniques to characterize the fracture toughness of RAFM steels with high fidelity. In this manuscript, we present the feasibility study of using pre-cracked miniature multi-notch bend bar specimens (M4CVN) with a dimension of 45mm (length) × 3.3mm (width) × 1.65mm (thickness) to characterize the transition fracture toughness of Eurofer97 steel based on the ASTM E1921 Master Curve method. The testing yielded a provisional Master Curve reference temperature ToQ of −89°C of unirradiated Eurofer97 steel heat J362A in the normalized and tempered condition. The results are within the normal scatter range of Master Curve reference temperature T0 for Eurofer97 steel, indicating suitability of applying M4CVN specimens for characterizing the transition fracture toughness of Eurofer97 steel.

Component Reliability Considerations for New Designs and Extended Operation of Boiling Water Reactor (BWRs)

2008 ◽  
Author(s):  
E. Kiss
Keyword(s):  
Stainless Steel ◽  
Alloy Steel ◽  
High Reliability ◽  
Pressure Vessels ◽  
Operational Experience ◽  
Low Alloy Steel ◽  
Irradiation Embrittlement ◽  
Component Reliability ◽  
Extended Operation ◽  
Reactor Pressure

To achieve high reliability for new designs and extended operation of Reactor Pressure Vessels and Internals it is mandatory to apply the technical knowledge gained during operation of the existing Plants to assure that sufficient “Margin” is built into the new design. This paper discusses the importance of four key structural degradation mechanisms that have been shown by operational experience to affect the reliability of the BWR. These are: 1) Stress Corrosion Cracking (IGSCC) of Stainless Steel and Nickel-based Alloys; 2) Irradiation Assisted SCC (IASCC) of Stainless Steel and Nickel-based Alloys; 3) Irradiation Embrittlement of RPV low alloy Steel; 4) Corrosion Assisted Fatigue of Carbon and Low Alloy Steel. While the focus of this paper is the BWR, the mechanisms discussed are equally applicable to the PWR, although the water chemistry effects and mitigations will be different.

Alternative RTNDT for Linde 80 Weld Materials

2002 ◽  
Author(s):  
K. K. Yoon ◽  
J. B. Hall
Keyword(s):  
Fracture Toughness ◽  
Transition Temperature ◽  
Pressure Vessel ◽  
Nuclear Power ◽  
Power Plants ◽  
Pressure Vessels ◽  
Screening Criteria ◽  
Master Curve Method ◽  
Asme Code ◽  
Curve Method

The ASME Boiler and Pressure Vessel Code provides fracture toughness curves of ferritic pressure vessel steels that are indexed by a reference temperature for nil ductility transition (RTNDT). The ASME Code also prescribes how to determine RTNDT. The B&W Owners Group has reactor pressure vessels that were fabricated by Babcock & Wilcox using Linde 80 flux. These vessels have welds called Linde 80 welds. The RTNDT values of the Linde 80 welds are of great interest to the B&W Owners Group. These RTNDT values are used in compliance of the NRC regulations regarding the PTS screening criteria and plant pressure-temperature limits for operation of nuclear power plants. A generic RTNDT value for the Linde 80 welds as a group was established by the NRC, using an average of more than 70 RTNDT values. Emergence of the Master Curve method enabled the industry to revisit the validity issue surrounding RTNDT determination methods. T0 indicates that the dropweight test based TNDT is a better index than Charpy transition temperature based index, at least for the RTNDT of unirradiated Linde 80 welds. An alternative generic RTNDT is presented in this paper using the T0 data obtained by fracture toughness tests in the brittle-to-ductile transition temperature range, in accordance with the ASTM E1921 standard.

Prediction of Fracture Toughness for WWER RPV Integrity Assessment on the Basis of the Unified Curve Approach and Surveillance Specimens Testing

2009 ◽  
Author(s):  
Boris Margolin ◽  
Victoria Shvetsova ◽  
Alexander Gulenko ◽  
Valentin Fomenko
Keyword(s):  
Fracture Toughness ◽  
Master Curve ◽  
Present Report ◽  
Temperature Shift ◽  
Curve Shape ◽  
Integrity Assessment ◽  
Master Curve Method ◽  
Curve Method ◽  
Unified Curve ◽  
Surveillance Specimens

For construction of the fracture toughness temperature curve that may be used for WWER RPV integrity assessment on the basis of tests of cracked surveillance specimens, the issues have to be solved as follows. First of all, it is important to determine how fracture toughness varies as a function of temperature, and how the fracture toughness vs. temperature dependence, KJC(T), changes with in-service material degradation due to neutron irradiation. These variations of KJC(T) curve are known to be the shift of KJC(T) curve to higher temperature range and change in the KJC(T) curve shape. At present, two advanced engineering methods are known that allow the prediction of KJC(T) curve on the basis of small-size fracture toughness specimens (for example, pre-cracked Charpy specimens), namely, the Master Curve and the Unified Curve methods. Procedures of test result treatment for the Master Curve and the Unified Curve are very similar. The Master Curve method uses the lateral temperature shift condition and, therefore, does not describe possible change in the KJC(T) curve shape. The Unified Curve method has an advantage as compared with the Master Curve as the Unified Curve describes a variation of the KJC(T) curve shape when degree of embrittlement increases. This advantage becomes important for RPV integrity assessment when the reference KJC(T) curve is recalculated to the crack front length of the postulated flaw that is considerable larger than thickness of surveillance specimens. Application of the KJC(T) curve determined from test results of cracked surveillance specimens to RPV integrity assessment requires also to introduce some margins. These margins have to take into account the type and number of tested specimens and the uncertainty connected with spatial non-homogeneity of RPV materials. Indeed, there is sufficient number of experimental data showing variability in fracture toughness for various parts of RPV. Therefore, situation is possible when the material properties near the postulated flaw will be worse than the properties of surveillance specimens. In the present report, advanced approaches are considered for prediction of fracture toughness for WWER RPV integrity assessment that allow one: • to construct the KJC(T) curve for irradiated RPV steels with any degree of embrittlement; • to provide transferability of fracture toughness data from cracked surveillance specimens to calculation of resistance to brittle fracture of RPV with a postulated flaw.

Thermal Aging Assessment and Microstructural Investigations of Alloy 52 Dissimilar Metal Welds for Nuclear Components

2019 ◽  
Author(s):  
Miguel Yescas ◽  
Pierre Joly ◽  
François Roch
Keyword(s):  
Fracture Toughness ◽  
Alloy Steel ◽  
Thermal Aging ◽  
Base Alloy ◽  
Narrow Gap ◽  
Low Alloy Steel ◽  
Nickel Base Alloy ◽  
Pressurized Water ◽  
Dissimilar Metal ◽  
Nickel Base

Abstract Dissimilar Metal Welds (DMW) are commonly found between the ferritic low alloy steel heavy section components and the austenitic stainless steel piping sections in nuclear power plants. In the EPR™ design which is the latest FRAMATOME Pressurized water reactor (PWR) these DMW involve a narrow gap technology with no buttering, and only one bead per layer of a nickel base alloy weld filler metal (Alloy 52). In order to assess the thermal aging performance of this relatively new narrow gap DMW design, a significant internal R&D program was launched some years ago. Several representative mock-ups were thoroughly characterized in the initial condition as well as in the thermal aged condition, up to 50,000 hours aging at 350°C. The characterisations were focused on the fusion line between the ferritic low alloy steel (LAS) and the nickel base alloy since a particular microstructure is present in this area, especially in the carbon depleted area of the Heat Affected Zone (HAZ) which is often regarded as the weak zone of the weld joint. Metallography, hardness, nanohardness, chemical analyses, and Atom Probe Tomography, as well as fracture toughness tests were carried out on different specimens in different thermal aging conditions. The results show that the fracture toughness behaviour in the ductile-brittle domain of the low alloy steel carbon depleted HAZ at the interface with the alloy 52 weld metal of the DMWs is excellent, even for a thermal ageing equivalent to 60 years at service temperature. This was found in spite of the carbon depleted zone of the HAZ, the variations of hardness, chemical composition, particularly the carbon gradients, and the thermal aging effect induced by phosphorous segregation at grain boundaries.

Sign in / Sign up

Export Citation Format

Share Document