scholarly journals Study on Micro-Structure and Tensile Mechanical Properties of Dissimilar Metal Weld Joint Connecting Steam Generator Nozzle and Safe-End

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1470
Author(s):  
Shuang Qi ◽  
Wenxin Xiang ◽  
Lixun Cai ◽  
Xiaokun Liu ◽  
Yonggang Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Power Plant ◽  
Nuclear Power ◽  
Plant Design ◽  
Micro Structure ◽  
Pressurized Water ◽  
Dissimilar Metal ◽  
Strain Relationship ◽  
Dissimilar Metal Weld ◽  
Metal Weld

The safe-end of a steam generator (SG) nozzle dissimilar metal weld (DMW) for pressurized water reactors (PWRs) is the weakest point of failure which is crucial for the safe operation of a nuclear power station. Related to materials micro-structures, a uniaxial stress–strain relationship is the basic input parameter for nuclear power plant design, safety evaluation, and life management. In this paper, the micro-structure and tensile mechanical properties of a DMW of a European pressurized water reactor (EPR) were studied. Vickers hardness tester, optical microscope, and electron back scatter diffraction were used to analyze the micro-structure of the DMW joint. In addition, the residual strain of the DMW joint base material, heat-affected zone, weld metal, and fusion boundary region were studied. Based on digital image correlation (DIC) technology, tensile mechanical properties of the DMW joint were obtained. The results show that an accurate tensile stress–strain relationship of dissimilar metal welded joints can be obtained by using the DIC technique, the weld is the relatively weak link, and the residual strain is concentrated in the heat-affected zone. This study provides valuable engineering information regarding nuclear power plant design, in-service performance testing, and structural analysis and evaluation of welds containing defects.

Microstructures and Mechanical Properties of Dissimilar Metal Weld A508/52M/316L Used in Nuclear Power Plants

2011 ◽  
Vol 479 ◽  
pp. 40-47 ◽  
Author(s):  
Ke Wei Fang ◽  
Guan Jun Li ◽  
Guang Fu Li ◽  
Wu Yang ◽  
Mao Long Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Weld Metal ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Dissimilar Metal ◽  
Primary Water ◽  
Dissimilar Metal Weld ◽  
Microstructures And Mechanical Properties ◽  
Metal Weld

The microstructures and mechanical properties of a dissimilar metal weld A508/52M/316L used in the primary water system of pressurized water reactor (PWR) nuclear power plants were investigated. The weld exhibits complicated microstructures, with significant change around the interfaces A508/52M and 52M/316L. The variations of main elements in 52M weld metal are greater than those in the A508 and 316L, with significant changes in the zones closed to the interfaces. The bulk 52M weld metal has higher and more uneven hardness than both of the base metals A508 and 316L. The HAZ of A508 exhibits the highest hardness value in the weld. The area around the A508/52M interface is the most weak part for stress corrosion cracking (SCC) resistance of the weld in simulated PWR primary water at 290°C. SCC was only found in the specimens tested at +200mV(SHE) but not in those tested at both -780mV and Ecorr (about -500mV).

Full Structural Weld Overlay on a Super Emergency Feedwater Nozzle at the Dukovany Nuclear Power Plant

2019 ◽  
Author(s):  
Steven L. McCracken ◽  
Marek Palán ◽  
Pavel Mlynář ◽  
Nicholas Mohr
Keyword(s):  
Czech Republic ◽  
Power Plant ◽  
Nuclear Power Plant ◽  
Nuclear Power ◽  
The Czech Republic ◽  
Weld Overlay ◽  
Nondestructive Examination ◽  
Dissimilar Metal ◽  
Dissimilar Metal Weld ◽  
Metal Weld

Abstract A weld overlay (WOL) following the general guidelines of ASME Code Case N-740-2 was successfully installed in March of 2018 on a dissimilar metal weld joining the super emergency feedwater1 piping to steam generator (SG) at the Dukovany nuclear power plant (NPP) in the Czech Republic. The repair was necessary due to stress corrosion cracking detected in the super emergency feedwater nozzle to safe-end dissimilar metal weld. This was the first WOL installed in the Czech Republic and represents a significant step towards further acceptance of this proven repair technology in Europe. The WOL repair approach was accepted by the Czech regulator, and two different inspection agencies, following successful mockup demonstrations, welding procedure qualification, nondestructive examination demonstrations and weld residual stress analyses. This paper describes the preparatory work as well as field deployment of WOLs in the Czech Republic.

Two- and Three-Dimensional Weld Residual Stress Analysis of a Weld Overlay Mockup of a VVER Feedwater Nozzle Dissimilar Metal Weld

2018 ◽  
Author(s):  
Francis H. Ku ◽  
Steven L. McCracken
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Three Dimensional ◽  
Pressurized Water ◽  
Weld Overlay ◽  
Dissimilar Metal ◽  
Before And After ◽  
Dissimilar Metal Weld ◽  
Three Dimensional Finite Element ◽  
Metal Weld

Weld overlay (WOL) is a popular repair technique to mitigate stress corrosion cracking (SCC) in dissimilar metal weld (DMW) in U.S. pressurized water reactor (PWR) design. The WOL technique is being considered as a SCC mitigation technique for DMW in Russian water-water energetic reactor (WWER or VVER) design. A WOL mockup on a VVER super emergency feedwater nozzle DMW has been fabricated, which represents the first WOL on VVER with the goal to mitigate SCC and the first WOL in Czech Republic civilian nuclear power plants. This paper presents the two- and three-dimensional finite element analyses performed to assess the weld residual stresses in the WOL mockup. The analysis evaluates the stress distribution and changes in the DMW before and after the WOL application, as well as compares the results to established industry guidelines and comparable WOLs on U.S. PWR.

An Approach to Controlling Inaccessible Regions for Inspection Defined by Rules on Fitness-For-Service in Japan

2009 ◽  
Author(s):  
Takashi Ota ◽  
Koji Dozaki
Keyword(s):  
Ultrasonic Testing ◽  
Nuclear Power ◽  
Industrial Safety ◽  
Current Status ◽  
Inlet Pipe ◽  
Dissimilar Metal ◽  
Primary Water ◽  
Alternative Measures ◽  
Dissimilar Metal Weld ◽  
Metal Weld

On September 2007, Primary Water Stress Corrosion Cracking (PWSCC) flaws were found on the dissimilar metal weld of the steam generator (SG) inlet pipe nozzles of Tsuruga-2. Following the Tsuruga-2, similar cases were found in some other plants. These cracks were located in inaccessible regions by Ultrasonic Testing (UT) examination applied from the outer surface. Triggered by these cases, the Nuclear and Industrial Safety Agency (NISA), Japanese regulator of nuclear industries, directed nuclear power plant owners to investigate current status of these inaccessible regions for inspection defined by rules on fitness-for-service in Japan, and required to show developing plan on alternative measures of inspection for UT-exempted welds. On the other hand, the study to manage inaccessible regions in the rules on fitness-for-service has been started. The authors consider and propose a possible approach for modified rules of inspection in order to make control of these inaccessible regions.

Failure Analysis Study of Dissimilar Metal Weld SA-213 T22 and SA-213 TP304H at Boiler Tube Steam Power Generation

2015 ◽  
Vol 827 ◽  
pp. 366-370
Author(s):  
Cukup Mulyana ◽  
Aswad Hi Saad ◽  
Mariah Kartawidjaja ◽  
Agtri Henboral
Keyword(s):  
Power Plant ◽  
Failure Analysis ◽  
Carbon Diffusion ◽  
Boiler Tube ◽  
Steam Power ◽  
Dissimilar Metal ◽  
Cause Of Failure ◽  
Dissimilar Metal Weld ◽  
Metal Weld ◽  
Plant Shutdown

Critical component of boiler that frequently experiencing failure is on the junction of boiler tube consist of two different materials. This failure mechanism would lead to tube rupture and would be followed by power plant shutdown. Failure analysis has been conducted on dissimilar metal weld (DMW) of Ferritic SA-213 T22 welded with Austenitic SA-213 TP 304H. This tube is used in Suralaya Steam Power Plant. Operating temperature and pressure of the steam inside the tube in normal condition are respectively 196.8kg/cm2 and 540 °C.In order to understand the real cause of failure several tests are ran, which are chemical composition test, micro vickers, and metallographic test on based metal, heat effective zone, and filler area. The tests are conducted in a layered manner to clearly understand the cause of the failure. Causes of the failure are due to the contribution of carbon diffusion and disparity of expansion coefficient of two materials.

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