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.

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

2013 ◽  
Author(s):  
Ed Pickering ◽  
Harry Bhadeshia
Keyword(s):  
Mechanical Properties ◽  
Pressure Vessel ◽  
Pressure Vessels ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Chemical Segregation ◽  
High Integrity ◽  
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. Given the scale of the pressure vessel casting, the segregation cannot be removed by practically feasible heat treatments. 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.

Elaboration and Introduction of the Methodics of Non-Destructive Inspection (Control) of Physical-Mechanical Properties of NPP Pressure Vessels

2004 ◽  
Author(s):  
M. Bakirov ◽  
V. Potapov ◽  
N. Zabruskov ◽  
I. Vystavkin ◽  
V. Levchuk
Keyword(s):  
Mechanical Properties ◽  
Pressure Vessel ◽  
Pressure Vessels ◽  
Full Scale ◽  
Primary Circuit ◽  
Pressure Vessel Steel ◽  
Physical Barrier ◽  
Vessel Steel ◽  
The Third ◽  
Inspection Control

Resource of reactor with PWR is defined, in the first instance, by foundation of integrity of the third physical barrier of safety. The third physical barrier of safety provides a reliable keeping of the coolant in the boundaries of NPP primary circuit. More than thirty year history shows, that reactor vessel is a weak spot in this barrier, the metal of the pressure vessel is subjected to intensive irradiation. The mechanism of operational damage of pressure vessel steel is represented in Fig. 1. This article describes the works, which were conducted by VNIIAES during the last years in the field of elaboration of specimen-free methods and means of inspection (control) of physical-mechanical properties of pressure vessels welds metal of NPPs with PWR. On the base of analysis of that factors, which exercise the most substantial influence on the irradiation embrittlement of pressure vessel materials and on the base of distribution of these factors by degree of significance, there were selected the most appropriate specimen-free methods of inspection: kinetic indentation and kinetic magnetising. It was presented the description of the specimen-free methods, devices and of the results of laboratory measurements, and also the description of the manufacturing procedure and the procedure of certification of the methods on full-scale slabs from WWER-1000 pressure vessel. In the article also is described the example of using of the specimen-free methodics by full-scale inspection (control) of the metal of reactor internal components and of pressure vessel of WWER-1000 of Rostov NPP Unit 1.

Measurements of Stress During Thermal Shock in Clad Reactor Pressure Vessel Material Using Time-Resolved In-Situ Synchrotron X-Ray Diffraction

2018 ◽  
Author(s):  
Sam Oliver ◽  
Chris Simpson ◽  
Andrew James ◽  
Christina Reinhard ◽  
David Collins ◽  
...  
Keyword(s):  
Thermal Shock ◽  
Pressure Vessel ◽  
Pressure Vessels ◽  
Reactor Pressure Vessel ◽  
Pressure Vessel Steel ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
Vessel Steel ◽  
X Ray ◽  
Reactor Pressure

Nuclear reactor pressure vessels must be able to withstand thermal shock due to emergency cooling during a loss of coolant accident. Demonstrating structural integrity during thermal shock is difficult due to the complex interaction between thermal stress, residual stress, and stress caused by internal pressure. Finite element and analytic approaches exist to calculate the combined stress, but validation is limited. This study describes an experiment which aims to measure stress in a slice of clad reactor pressure vessel during thermal shock using time-resolved synchrotron X-ray diffraction. A test rig was designed to subject specimens to thermal shock, whilst simultaneously enabling synchrotron X-ray diffraction measurements of strain. The specimens were extracted from a block of SA508 Grade 4N reactor pressure vessel steel clad with Alloy 82 nickel-base alloy. Surface cracks were machined in the cladding. Electric heaters heat the specimens to 350°C and then the surface of the cladding is quenched in a bath of cold water, representing thermal shock. Six specimens were subjected to thermal shock on beamline I12 at Diamond Light Source, the UK’s national synchrotron X-ray facility. Time-resolved strain was measured during thermal shock at a single point close to the crack tip at a sample rate of 30 Hz. Hence, stress intensity factor vs time was calculated assuming K-controlled near-tip stress fields. This work describes the experimental method and presents some key results from a preliminary analysis of the data.

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