scholarly journals Electron Beam Welding of Large Components for The Nuclear Industry

2019 ◽  
Vol 269 ◽  
pp. 02009
Author(s):  
Bernd Baufeld ◽  
Thomas Dutilleul
Keyword(s):  
Electron Beam ◽  
Pressure Vessel ◽  
Large Scale ◽  
Electron Beam Welding ◽  
Pressure Vessels ◽  
Nuclear Industry ◽  
Future Application ◽  
Research Centre ◽  
Circumferential Welds ◽  
Full Penetration

The nuclear industry requires rapid and high quality joining of large scale components. Electron beam welding (EBW) has the potential to respond to these requirements. The aim of Nuclear Advanced Manufacturing Research Centre (Nuclear AMRC) is to develop solutions for the future application of this technology. One example is the research on deep penetration EBW for joining large scale pressure vessels for small modular nuclear reactors. This will require several circumferential welds of ~ 6 metres length each. In addition joining of sections of the upper and lower vessel heads and of HIP sections with varying wall thickness must be developed. In collaboration with the US Electric Power Research Institute (EPRI) the Nuclear AMRC is working to produce two-thirds scaled demonstrators of the lower and the upper pressure vessel assembly (based on a generic NuScale model). 100 mm deep single track, full penetration welds of pressure vessel steel have been demonstrated. In addition, within 26 minutes joining of shells was achieved with 6 metres long circumferential welds (78 mm full penetration). In future the joining of complex sections and sections with variable thickness will be investigate.

Oxygen Pressure Aging. Improved Equipment

1938 ◽  
Vol 11 (4) ◽  
pp. 722-727
Author(s):  
L. M. Freeman
Keyword(s):  
Oxygen Pressure ◽  
Pressure Vessel ◽  
Large Scale ◽  
Oxygen Supply ◽  
Pressure Vessels ◽  
Water Bath ◽  
Aging Test ◽  
Constant Temperature Water Bath ◽  
Temperature Water ◽  
Continuous Source

Abstract Since the introduction of the oxygen pressure-aging test by Bierer and Davis, prevailing standard conditions for the test have been 70° C. (158° F.) and 300 pounds per square inch oxygen pressure. Various types of equipment have been used; usually the equipment has consisted of a pressure vessel immersed in a constant-temperature water bath to which is connected an oxygen supply. In the majority of instances the equipment has been difficult to operate and maintain for several reasons: Immersion of pressure vessels in a water bath made handling difficult. Corrosion was a continuous source of trouble, causing “freezing” of cover bolts and making it difficult to obtain a leakproof oxygen seal between cover and vessel. This caused loss of oxygen. Each time the pressure vessel was removed from the bath it was necessary to disconnect the oxygen supply and make the connection again when the test was started. This also caused loss of oxygen. If more than one pressure vessel was connected to the oxygen supply and a safety released, the entire oxygen supply was exhausted. The original pressure vessels were relatively large. Since the use of age resistors on a large scale, smaller units have been desirable in order to decrease migration of age resistors and eliminate erroneous results. Some of these operation difficulties were outlined by Ingmanson and Kemp, who also emphasized the importance of temperature control to obtain reproducible results. It is the purpose of this paper to describe an improved oxygen pressure installation which avoids some of these difficulties.

Improving Toughness of Electron Beam Welds of Heavy Mn-Mo-Ni Steel Plates for Pressure Vessels

1993 ◽  
Vol 115 (3) ◽  
pp. 242-248 ◽  
Author(s):  
Y. Tomita ◽  
K. Tanabe ◽  
K. Koyama
Keyword(s):  
Electron Beam ◽  
Weld Metal ◽  
Steel Plate ◽  
Electron Beam Welding ◽  
Fracture Initiation ◽  
Pressure Vessels ◽  
Chemical Compositions ◽  
Intergranular Cracking ◽  
Electron Beam Weld ◽  
Upper Bainite

Electron beam welding melts and solidifies steel plate without using any welding material, unlike the conventional welding. Therefore, the toughness at the weld metal can decrease, depending on the chemical composition of the steel plate. Toughness at the electron beam weld can be increased by turning the microstructure from upper bainite into lower bainite and making the effective grain size finer. The microstructure can be controlled by the addition of alloy elements and optimization of impurity elements. In case the chemical compositions cannot be varied, largely because of the specification for their ranges, and the weld metal microstructure remains as upper bainite even after the application of microstructure control, methods to improve the toughness of electron beam weld itself, regardless of steel grades, becomes necessary. Phenomena peculiar to the electron beam weld are segregation during solidification and intergranular segregation over the dendrite surface. The fracture initiation is accelerated by the microcracks caused by the segregations during solidification. The fracture propagation is promoted by intergranular cracking caused by the intergranular segregation. By reducing these segregations, the fracture initiation and propagation are restrained and toughness increases despite the upper bainite microstructure. This can be achieved by the higher purification of steel. Through the foregoing investigations, ASTM A533 Type B Class 2 steel plate of 100 mm in thickness for electron beam welds has been developed for pressure vessels. Various welding tests as pressure vessels have been conducted, and it becomes clear that the developed steel plate has excellent toughness at the weld superior to those obtainable by conventional welding. The use of this steel greatly reduces the welding period compared to the conventional welding method.

The Assessment and Assurance of Pressure Vessel Reliability

1975 ◽  
Vol 189 (1) ◽  
pp. 391-404 ◽  
Author(s):  
R. W. Nichols
Keyword(s):  
Quality Assurance ◽  
Pressure Vessel ◽  
Reliability Assessment ◽  
Pressure Vessels ◽  
Nuclear Industry ◽  
Detailed Design ◽  
Confidence Levels ◽  
Statistical Confidence ◽  
Reliability Assessments ◽  
Operational Behaviour

The factors involved in assessing the reliability of pressure vessels drawing extensively upon the developments which have arisen from applications in the nuclear industry. Existing assessments of reliability and operational behaviour highlight some improvements which could result from more detailed design assessments especially with respect to stress analysis, stress transients and the significance of defects. Additionally the contributions to reliability made by fabrication and materials technology, inspection and quality assurance and post operational surveillance are critically examined. The use of such data in synthesizing a reliability assessment is discussed noting the problems of establishing statistical confidence levels and highlighting those areas where further evidence would produce significant advances in quantifying reliability assessments.

The Consequences of Macroscopic Segregation on the Transformation Behavior of a Pressure-Vessel Steel

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
E. J. Pickering ◽  
H. K. D. H. Bhadeshia
Keyword(s):  
Mechanical Properties ◽  
Pressure Vessel ◽  
Large Scale ◽  
Pressure Vessels ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Chemical Segregation ◽  
Compositional Variations ◽  
Grade 3 ◽  
Kinetics Of

It is important that the material used to produce high-integrity pressure vessels has homogeneous properties which are reproducible and within specification. Most heavy pressure vessels comprise large forgings derived from ingots, and are consequently affected by the chemical segregation that occurs during ingot casting. Of particular concern are the compositional variations that arise from macrosegregation, such as the channels of enriched material commonly referred to as A-segregates. By causing corresponding variations in microstructure, the segregation may be detrimental to mechanical properties. It also cannot be removed by any practically feasible heat treatments because of the large scale on which it forms. Here we describe an investigation on the consequences of macrosegregation on the development of microstructure in a pressure-vessel steel, SA508 Grade 3. It is demonstrated that the kinetics of transformation are sensitive to the segregation, resulting in a dramatic spatial variations in microstructure. It is likely therefore that some of the scatter in mechanical properties as observed for such pressure vessels can be attributed to macroscopic casting-induced chemical segregation.

Probabilistic Risk Assessment of Aging Layered Pressure Vessels

2019 ◽  
Author(s):  
D. S. Riha ◽  
M. L. Kirby ◽  
J. W. Cardinal ◽  
L. C. Domyancic ◽  
J. M. McFarland ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Pressure Vessel ◽  
Pressure Vessels ◽  
Regions Of Interest ◽  
Probabilistic Framework ◽  
Circumferential Welds ◽  
Failure Assessment ◽  
Modeling Software ◽  
Geometric Discontinuities ◽  
Flaw Location

Abstract The National Aeronautics and Space Administration (NASA) operates approximately 300 aging layered pressure vessels that were designed and manufactured prior to ASME Boiler and Pressure Vessel (B&PV) code requirements. In order to make decisions regarding the continued fitness-for-service of these non-code carbon steel vessels, it is necessary to perform a relative risk of failure assessment for each vessel. However, risk assessment of these vessels is confounded by uncertainties and variabilities related to the use of proprietary materials in fabrication, missing construction records, geometric discontinuities, weld residual stresses, and complex service stress gradients in and around the welds. Therefore, a probabilistic framework that can capture these uncertainties and variabilities has been developed to assess the fracture risk of flaws in regions of interest, such as longitudinal and circumferential welds, using the NESSUS® probabilistic modeling software and NASGRO® fracture mechanics software. In this study, the probabilistic framework was used to predict variability in the stress intensity factor associated with different reference flaws located in the head-to-shell circumferential welds of a 4-layer and 14-layer pressure vessel. The probabilistic studies predict variability in flaw behavior and the important uncertain parameters for each reference flaw location.

Investigation on the Effects of Carbon Macro-Segregation of Mechanical Properties Using a Large-Scale Forged Low Alloy Steel for a BWR Reactor Pressure Vessel

2020 ◽  
Author(s):  
Takahiro Hayashi ◽  
Takuya Ogawa ◽  
Rie Sumiya ◽  
Tetsushi Yamaoka ◽  
Shigeaki Tanaka ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Carbon Content ◽  
Pressure Vessel ◽  
Material Properties ◽  
Large Scale ◽  
Structural Reliability ◽  
Pressure Vessels ◽  
Reactor Pressure Vessel ◽  
Steel Making ◽  
Reactor Pressure

Abstract Control of carbon macro-segregation in the steel-making process for large steel forgings is of great importance in order to achieve the material properties and structural reliability required for the pressure vessels of nuclear power plant components. It is well known that high carbon content due to carbon macro-segregation can affect the mechanical properties of steels, leading to decreases in ductility and fracture toughness. In this study, possible effects of carbon macro-segregation have been examined using a large-scale forged steel “bottom head dome” of a reactor pressure vessel (RPV) manufactured for a recent BWR. Material testing conducted included chemical analyses, tensile tests and Charpy impact tests. In the center part of the concave disk-shaped forged material, carbon content varied slightly in the material thickness direction within the range of carbon content requirement, as expected from the relationship between the solidification and the resultant segregation process in the cast ingot material and the forging process from the ingot to the dome material. The results of each mechanical test also showed full compliance with the properties required in the code regardless of the carbon content at each of the thickness locations examined. All the tests results demonstrated that with the steel-making technology and practice employed, carbon macro-segregation is well controlled to achieve the required material properties even in large-scale forged materials used in BWRs.

Researching Signals from Workpiece Backside during Electron Beam Welding in Full Penetration Mode

2017 ◽  
Vol 743 ◽  
pp. 231-235
Author(s):  
Stepan Varushkin ◽  
Vladimir Belenkiy ◽  
Dmitriy Trushnikov
Keyword(s):  
Electron Beam ◽  
Electron Beam Welding ◽  
Research Work ◽  
Sensor Selection ◽  
Ion Current ◽  
Electron Current ◽  
X Ray ◽  
Control Precision ◽  
Full Penetration ◽  
Selection For

In this research work, we consider the problem of sensor selection for the system controlling full penetration mode in electron beam welding. For this, we have investigated four signals from the backside of the workpiece: electron current in root plasma, ion current in root plasma, through-thickness electron current and penetrating bremsstrahlung X-ray. After having done the research we have estimated the advisability of two signals: one for cases if requirements for control precision are high and the other for other cases.

Simulation and Measurements of Electron Beam Welding Distortions

2009 ◽  
Author(s):  
Antoine Martin ◽  
Vincent Robin ◽  
Philippe Gilles ◽  
Fabrice Bouyer
Keyword(s):  
Electron Beam ◽  
Electron Beam Welding ◽  
Welding Process ◽  
Nuclear Industry ◽  
Design Stage ◽  
Strong Impact ◽  
Simplified Approach ◽  
Numerical Predictions ◽  
Welded Structure ◽  
Welding Sequence

Welding problems encountered in the nuclear industry have been mainly addressed by weldability tests analysis, development of new techniques or improvements through lessons learnt. For the last decade, AREVA has developed a complementary approach based on numerical simulation. Residual stresses inherent in the manufacturing of reactor components do not constitute a major problem at the design stage; even though they may have a strong impact on some types of damage. Numerical welding simulation in the nuclear industry has mainly focused on residual stress prediction. Distortion may also be a source of concern in component design: some structures are slender in spite of their thickness. In the frame of GEN IV project like sodium fast reactor or ITER, the distortion problem has gained in importance. For industrial project considering large structure, DCNS has developed electron beam welding process and built several mock-ups to validate the manufacturing steps. AREVA NP carried out welding simulations on one of these mock-ups (1m × 1m) made of austenitic steel plates and representative of nuclear components. The aim of the numerical simulations was to check the quality of the distortion prediction. Electron beam (EB) welding offers significant advantages for structures with many long welds and high requirements on the final shape of the welded structure. Since distortion values are very low (between 0.1 mm and 1.6 mm), prediction of distortions induced by electron beam welding is difficult. Compared to the size of the mock-up (1 m), distortions represent only 0.1%. Distortions induced by each weld have been computed using a simplified approach (local/global method [1]), which aims at modelling long and numerous welding operations with an acceptable calculation time. After each welding sequence, DCNS measured distortions at some representative points of the mock-up. This paper comments on the difficulties of the validation of the numerical predictions by comparison with measurements: • Measurements are made after each welding step, requiring removing the parts from the chamber. • Distortion values are very low compared to the size of the mock-up that may increase the risk of measurement error. In spite of these problems, the main trends of the experimental deformed shape are well represented by the simulation.

Residual Stresses in a Welded Zircaloy Cold Neutron Source Containment Vessel

2014 ◽  
Vol 777 ◽  
pp. 194-198 ◽  
Author(s):  
Philip Bendeich ◽  
Vladimir Luzin ◽  
Michael Law
Keyword(s):  
Electron Beam ◽  
Residual Stresses ◽  
Neutron Source ◽  
Electron Beam Welding ◽  
Cold Neutron ◽  
Rotational Symmetry ◽  
Welding Process ◽  
Nuclear Industry ◽  
Critical Crack ◽  
Cold Neutron Source

Zirconium alloys are widely used in the nuclear industry because of their relative high strength, neutron transparency, resistance to high neutron-irradiation environment and corrosion resistance. One application for Zirconium alloy Zr-2.5Nb is the vacuum confinement vessel utilised in the cold neutron source of the OPAL research reactor at ANSTO. Having a total length of more the 3 meters, it is made of two sections joined using electron beam welding. The weld and the nearby regions are critical for the performance and integrity of the component and therefore understanding of the residual stresses development within the weld is important in connection to (i) evolution of fine dual phase α/b microstructure and crystallographic texture (ii) and stress-related radiation induced phenomena, such as grain growth, creep and sub-critical crack growth by delayed hydride cracking. The stresses were measured in and around an electron beam weld produced during the development of this component of the OPAL Cold Neutron Source. The effects of a large grain size in the weld were reduced by taking advantage of rotational symmetry and rotating the sample to increase the swept volume. Due to the heat-treatment after welding, the stresses were very low, less than 10% of the yield strength of the material, in both the hoop and axial directions. As a result of phase transformation effects during the welding process the final stresses are compressive in the weld, which reduces the likelihood of fracture or of hydride formation in this region. The highest stresses are in the parent material adjacent to the weld where the toughness is expected to be higher than in the weld material.

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