Microstructure and Properties Analysis of Inner Cladding Tube and End Plug Girth Weld of Annular Fuel Element

2017 ◽  
Author(s):  
Ji Pengbo ◽  
Lu Hanghang ◽  
Wang Zhaosong ◽  
Zhang Zhoufeng ◽  
Liu Bin
Keyword(s):  
Fuel Element ◽  
Heat Affected Zone ◽  
Welded Joints ◽  
Weld Zone ◽  
Tensile Fracture ◽  
Massachusetts Institute Of Technology ◽  
Micro Hardness ◽  
Welding Zone ◽  
Pressurized Water ◽  
Institute Of Technology

Annular fuel element is a kind of new double-sided fuel element, and the welding between the inner cladding tube and end plug of it belongs to a new kind of welding. Actually the conception was first proposed by Massachusetts Institute of Technology and the China Institute of Atomic Energy of Reactor Engineering makes the physical design of annular fuel element product. Through this research, we now basically master the method of welding annular fuel element. In this research, we designed a girth-welding fixture for welding the inner cladding tube and end plug of annular fuel element. The influences of the power input on the weld penetration and morphology have been obtained. The metallurgical performance of welded joints was analyzed through optical microscope, hardness testing and scanning electron microscope (SEM). The mechanical tests results indicate that the tensile properties of the welded joints are closely related to the microstructure. And the welding joints are also tested in the autoclave. The research shows that the micro hardness along the longitudinal section of the inner cladding tube appears to be the trend: firstly gradually reduced, and then stayed. The highest hardness is in the welding zone. And the heat-affected zone has great impacts on the micro hardness: the far the area is away from the welding line, the lower the micro hardness becomes. The grains in both of the weld zone and heat-affected zone are obviously grown up, but the grain growth is more obvious in the weld zone. The tensile fracture of the welding joint all occurs in the welding zone, the tensile strength is larger than that of the bar, which is used for processing the end plug. And the maximum force belongs to the shear stress fracture. In microstructure picture, the weld fracture appears to be dimple-shaped. And some of the dimples showed equiaxial and some of the dimples showed the elongated dimples. And the surface-welding zone is coated with the uniform and compact black oxide film without the white and brown corrosion. All the results and study in the paper will be of guidance for the further processing of the annular fuel element used in the pressurized water reactor (PWR).

scholarly journals Weld Formation in Laser Hot-Wire Welding of 7075 Aluminum Alloy

Metals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 909 ◽  
Author(s):  
Shichun Li ◽  
Wei Xu ◽  
Gang Xiao ◽  
Bing Chen
Keyword(s):  
Aluminum Alloy ◽  
Base Metal ◽  
Heat Affected Zone ◽  
Weld Zone ◽  
Welding Process ◽  
Tensile Fracture ◽  
Hot Wire ◽  
Columnar Crystal ◽  
Weld Formation ◽  
Hot Wire Welding

The laser hot-wire welding process was adopted to weld 7075 high-strength aluminum alloy. The influence laws of parameters on the weld formation were analyzed during laser hot-wire welding, and the microstructure characteristics and mechanical properties of welds were analyzed. The results showed that the parameters whose significance of influence on weld formation as ranked from high to low were laser power, current, gap width, welding speed and wire feeding rate. With the increase of wire temperature, the weld formation quality became better initially and then worse. Under the condition of optimized parameters, good weld formation could be obtained. The weld zone had a fine grain microstructure, and was in casting state consisted of dendritic crystal and equiaxed crystal. The heat affected zone mainly consisted of columnar crystal. The microhardness decreased gradually from base metal to heat affected zone then to weld zone. The tensile fracture of weld specimen occurred at the weld zone, and was in the ductile fracture state. The tensile strength of weld joint was 206 MPa and was 64.2% of base metal strength.

scholarly journals Investigation of Micro Hardness, Cooling Rate and Microstructure of ATIG Welded samples of Al-SiC composite

2018 ◽  
Vol 151 ◽  
pp. 01002 ◽  
Author(s):  
Sivachidambaram Pichumani ◽  
Raghuraman Srinivasan ◽  
Venkatraman Ramamoorthi
Keyword(s):  
Cooling Rate ◽  
Heat Affected Zone ◽  
Weld Zone ◽  
Correlation Study ◽  
Tig Welding ◽  
Constant Current ◽  
Micro Hardness ◽  
Micro Structure ◽  
Fine Grain ◽  
Hardness Values

Activated TIG welding has been performed on Al – 8% SiC composite 5mm plate with various fluxes such as Al2O3, MnO2, CaO, MgO, SiO2 & TiO2, to study & analyze the Microstructure, Micro hardness and cooling rate. Correlation study between micro hardness, microstructure and cooling rate for Constant Current TIG welding and Activated TIG welding on Al-SiC composite are also carried out to analyze the relation between the effect of cooling rate on microstructure & the effect of microstructure on micro hardness. The experimental results of ATIG welding on Al-SiC composite shows fine grain weld microstructure on ATIG – SiO2 & ATIG – TiO2, which results in higher micro hardness. Micro hardness values are taken in different locations of weld surface at 1mm, 2mm & 3mm below the weld surface and the same is also observed along the weld zone to heat affected zone upto 12mm for the center of the weldment. Minimum micro hardness values found in ATIG – MnO2, ATIG – CaO & ATIG – MgO are due to intermediate micro structure between coarse and fine in heat affected zone. ATIG – Al2O3 weld zone & heat affected zone and heat affected zone of ATIG – MnO2, ATIG – CaO & ATIG – MgO shows coarse microstructure leading to reduction in micro hardness value. Cooling rate for the different CCTIG & ATIG welding are recorded and correlation between the micro structures are studied. Coarse micro structure in weld zone and heat affected zone have least cooling rate whereas fine micro structure in weld zone resulted at higher cooling rate. Heat affected zone strongly depends on temperature gradient between the weld center and weldment’s heat affected zone.

scholarly journals Optimization of the loading pattern of the PWR core using genetic algorithms and multi-purpose fitness function

Nukleonika ◽  
2021 ◽  
Vol 66 (4) ◽  
pp. 147-151
Author(s):  
Wojciech Kubiński ◽  
Piotr Darnowski ◽  
Kamil Chęć
Keyword(s):  
Genetic Algorithms ◽  
Fuel Cycle ◽  
Fitness Function ◽  
Geometry Optimization ◽  
Total Power ◽  
Massachusetts Institute Of Technology ◽  
Power Flux ◽  
Pressurized Water ◽  
Loading Pattern ◽  
Institute Of Technology

Abstract The study demonstrates an application of genetic algorithms (GAs) in the optimization of the first core loading pattern. The Massachusetts Institute of Technology (MIT) BEAVRS pressurized water reactor (PWR) model was applied with PARCS nodal-diffusion core simulator coupled with GA numerical tool to perform pattern selection. In principle, GAs have been successfully used in many nuclear engineering problems such as core geometry optimization and fuel configuration. In many cases, however, these analyses focused on optimizing only a single parameter, such as the effective neutron multiplication factor (k eff), and often limited to the simplified core model. On the contrary, the GAs developed in this work are equipped with multiple-purpose fitness function (FF) and allow the optimization of more than one parameter at the same time, and these were applied to a realistic full-core problem. The main parameters of interest in this study were the total power peaking factor (PPF) and the length of the fuel cycle. The basic purpose of this study was to improve the economics by finding longer fuel cycle with more uniform power/flux distribution. Proper FFs were developed, tested, and implemented and their results were compared with the reference BEAVRS first fuel cycle. In the two analysed test scenarios, it was possible to extend the first fuel cycle while maintaining lower or similar PPF, in comparison with the BEAVRS core, but for the price of increased initial reactivity.

scholarly journals Massachusetts Institute of Technology Reactor LEU Fuel Element Flow Test Conceptual Design

2021 ◽  
Author(s):  
Cezary Bojanowski ◽  
Guanyi Wang ◽  
Ron Kmak ◽  
Andrew Hebden ◽  
Aaron Weiss ◽  
...  
Keyword(s):  
Fuel Element ◽  
Conceptual Design ◽  
Massachusetts Institute ◽  
Massachusetts Institute Of Technology ◽  
Flow Test ◽  
Institute Of Technology

scholarly journals DIFFUSION OF HYDROGEN IN WELDED JOINTS OF STRUCTURAL STEELS

2017 ◽  
Vol 21 (6) ◽  
pp. 85-95 ◽  
Author(s):  
N. N. Sergeev ◽  
A. N. Sergeev ◽  
S. N. Kutepov ◽  
A. E. Gvozdev ◽  
E. V. Ageev
Keyword(s):  
Diffusion Coefficient ◽  
Weld Metal ◽  
Heat Affected Zone ◽  
Welded Joints ◽  
Chemical Potential ◽  
Weld Zone ◽  
Base Material ◽  
High Strength ◽  
Low Alloy Steels ◽  
Alloy Steels

High-strength low-alloy steels are widely used in the construction of welded metal structures. The main advantage of these steels is good combination of strength and toughness, and weldability. However, when welding high strength low alloy steels during cooling of the weld to a temperature below 150-100 °C there may be a risk of formation of bulk crystal structures defects in the weld zone - cold cracks. It was experimentally established that one of the factors contributing to the formation of cold cracks may be the occlusion of hydrogen in the atmosphere of arc plasma in the solidifying weld metal, from which diffusion hydrogen may diffuse to different areas of the weld after cooling. Hydrogen cracking typically has a tendency to slow down i.e. cracks can occur several days after the completion of welding process. As a rule, hydrogen induced cracking occurs either in the original steel in the heat-affected zone or in the weld metal, which is important, topical and long been researched by various scientific schools. Modern technologies of high strength low alloy steels processing have significantly improved the quality of the base material by reducing the amount of carbon and impurities, which has increased the stability of weld in the heat affected zone (HAZ) to hydrogen induced cold cracking. The paper presents modern approaches to the definition of diffusion coefficient of hydrogen in welded joints of high-strength low-alloy steels. Taking into account the temperature, the gradient of chemical potential and continuity conditions there has been considered the process of mass transfer of hydrogen under the influence of diffuse inhomogeneous mediums. It has been shown that the local effects of changing pressure and chemical potential are described using the equation of generalized potential of the diffusing substance. Our paper presents analytical expressions to determine the apparent diffusion coefficient of hydrogen in different local areas of a welded joint depending on temperature.

Tests of Fracture Toughness of Laser-Welded Joints Made of Duplex 2205 Steel

2016 ◽  
Vol 250 ◽  
pp. 191-196
Author(s):  
Robert Soltysiak
Keyword(s):  
Fracture Toughness ◽  
Fatigue Crack ◽  
Heat Affected Zone ◽  
Welded Joints ◽  
Welded Joint ◽  
Weld Zone ◽  
Structural Heterogeneity ◽  
Parent Material ◽  
Joint Area

The process of welding introduces geometric notches to the area of joined material in the form of a face and root of a weld as well as structural heterogeneity in the form of changed properties (as compared with the parent material) in the heat affected zone and the weld zone. The parent material, as compared with the zones formed by welding, may differ in fracture toughness. In this paper the results of tests of fracture toughness of DUPLEX 2205 steel laser-welded joints are presented. Butt-welded joints were made by use of an Nd-YAG disc laser with no filler. The fatigue crack was initiated in the parent material and in the area including both the heat affected zone as well as the weld zone. The tests showed higher fracture toughness of the welded joint area as compared with the parent material.

scholarly journals THERMAL INFLUENCE ON THE MICROSTRUCTURE AND THE MICRO HARDNESS OF A CARBON STEEL WELD PROBES

2020 ◽  
Vol 5 (8) ◽  
pp. 1-10
Author(s):  
Mbelle Samuel Bisong ◽  
Kisito Pierre ◽  
Valeriy Lepov
Keyword(s):  
Carbon Steel ◽  
Heat Affected Zone ◽  
Weld Zone ◽  
Low Carbon Steel ◽  
Hardness Test ◽  
Low Carbon ◽  
Micro Hardness ◽  
Structural Examination ◽  
Fine Grained ◽  
Thermal Influence

During welding, the heat produced during the process can affect the microhardness and the microstructure of the material. The change in the microstructure and the microhardness can be discovered by carrying out a microhardness test on the welded sample and compare changes in the three different zones i.e the base, the weld and the Heat affected zone or by carrying out a micro structural examination on the welded sample and see the grain dispersion in relation to their sizes. In this work, weld quality of manual arc welded samples of low-carbon steel St3spdestined for bridge construction to be used in Cameroon has been investigated. After a chemical analysis of the material, a micro hardness test and a micro structural examination was also done. Results show that a composition of pearlite and ferrite was seen with the print of the id enter of the micro hardness test. The formation of pearlite and ferrite in base metalis composed of 20/80 respectively. For weld zone and HAZ it changes due to thermal processes. So the microstructure analysis shows that the base metal is a ferrite and pearlite having a grain size of 11-12 on a scale corresponding to an average grain diameter ≈ 7 microns. The structure of the weld metal is also made up of ferrite and pearlite with columnar crystals of cast metal. The HAZ is made up of Widmanstätten. The width of the HAZ zone is about 1,5 mm. In different areas of heat affected zone is observed fine-grained ferrite-pearlite structure with a high degree of dispersion.

Applying the Anderson-Darling Test to Suicide Clusters

Crisis ◽  
2013 ◽  
Vol 34 (6) ◽  
pp. 434-437 ◽  
Author(s):  
Donald W. MacKenzie
Keyword(s):  
Poisson Process ◽  
Goodness Of Fit ◽  
Small Samples ◽  
Massachusetts Institute Of Technology ◽  
Homogeneous Poisson Process ◽  
Cornell University ◽  
The Difference ◽  
Suicide Clusters ◽  
Institute Of Technology ◽  
Anderson Darling

Background: Suicide clusters at Cornell University and the Massachusetts Institute of Technology (MIT) prompted popular and expert speculation of suicide contagion. However, some clustering is to be expected in any random process. Aim: This work tested whether suicide clusters at these two universities differed significantly from those expected under a homogeneous Poisson process, in which suicides occur randomly and independently of one another. Method: Suicide dates were collected for MIT and Cornell for 1990–2012. The Anderson-Darling statistic was used to test the goodness-of-fit of the intervals between suicides to distribution expected under the Poisson process. Results: Suicides at MIT were consistent with the homogeneous Poisson process, while those at Cornell showed clustering inconsistent with such a process (p = .05). Conclusions: The Anderson-Darling test provides a statistically powerful means to identify suicide clustering in small samples. Practitioners can use this method to test for clustering in relevant communities. The difference in clustering behavior between the two institutions suggests that more institutions should be studied to determine the prevalence of suicide clustering in universities and its causes.

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