Development of Co-Reduced Valve Seat for Nuclear Power Plants

2013 ◽  
Author(s):  
Toshiyuki Tazawa ◽  
Masahiro Saito ◽  
Nobuo Kojima
Keyword(s):  
Tensile Strength ◽  
Abrasion Resistance ◽  
Nuclear Power ◽  
Power Plants ◽  
Charpy Impact ◽  
High Hardness ◽  
Mechanical Tests ◽  
Valve Seat ◽  
Alternative Material ◽  
Sliding Test

The overlaying of Co-based alloy (e.g. “Stellite”) has been applied to valve seats in power plants to improve wear and abrasion resistance. However, using of the Co-based alloy should be avoided to valves which involve with reactor water in nuclear power plant because of activating to Co-60, and increment of radiation dose. Therefore, the alternative material to Co-based alloy has been required for these valves. Hardfacing is usually applied to improve abrasion resistance. Several high hardness materials without Co element were investigated, and it was found a Fe-based alloy as an alternative to Co-based alloy for the overlaying of valve seats. Mechanical tests of this Fe-based alloy formed by Plasma Transfer Arc (PTA) welding were carried out. Obtained values of tensile strength, Vickers hardness and Charpy impact value of the Fe-based alloy were almost equivalent to Co-based alloy. In addition, mock-up valve specimen was prepared, and sliding test was performed in simulated BWR plants environment. As a result, the amount of leakage was little enough when the Fe-based alloy is overlaid on one side seat part, and the radiation exposure from the valve seat can be reduced by 78 percent compared with the case of using the Co-based alloy for both side of overlaying. Note: Product names mentioned herein may be trademarks of their respective companies.

Apply the Acoustoelastic Method to Determine Residual Stresses in Welded Joints

NDT World ◽  
2020 ◽  
pp. 10-17
Author(s):  
Arkady Kamyshev ◽  
Aleksandr Danilov ◽  
Lev Pasmanik ◽  
Aleksandr Getman ◽  
Dmitry Kuzmin ◽  
...  
Keyword(s):  
Residual Stresses ◽  
Weld Metal ◽  
Base Metal ◽  
Welded Joints ◽  
Nuclear Power ◽  
Power Plants ◽  
Stress Measurement ◽  
Metal Structure ◽  
Mechanical Tests ◽  
Residual Welding

The problem of maximum stresses estimation in the weld metal, where the direct measurements are not possible due to the influence of the metal structure on the measurement error, was solved. The influence of features of welding joints manufacturing technology on the structure of the weld metal was also determined. We use several reference welded joints of pipelines at nuclear power plants in our studies. Instrumental estimation of acoustoelasticity parameters in the weld metal in welded joints and in adjacent areas of the base metal was used together with computational modeling of the residual welding stresses distributions. Results obtained demonstrate that the error of stress measurement in the metal in the joint, which is related to the structure of the weld metal, is comparable to the material yield strength. Due to that a direct measurement of the maximum values of welding stresses is not possible. Comparison of results of acoustoelasticity parameters measurements with results of the metal macrostructure studies and mechanical tests allowed us to determine the relationship between peculiarities of structure of the weld metal sections at vertical joints with their tendency to brittle destruction. We propose and justify the NDT method of residual welding stresses in the weld metal. It is based on the principle of residual stresses balancing and employs the results of stress measurements in the base metal by acoustoelasticity. Applicability of non-destructive testing of acoustoelasticity parameters to identify the areas of welded joints with a higher tendency to brittle fracture is also justified.

Polybutadienes of Controlled Cis, Trans and Vinyl Structures

1959 ◽  
Vol 32 (2) ◽  
pp. 614-627 ◽  
Author(s):  
J. N. Short ◽  
G. Kraus ◽  
R. P. Zelinski ◽  
F. E. Naylor
Keyword(s):  
Tensile Strength ◽  
Low Temperature ◽  
Natural Rubber ◽  
Physical Properties ◽  
Abrasion Resistance ◽  
High Hardness ◽  
High Modulus ◽  
High Tensile Strength ◽  
Truck Tires ◽  
Wide Range

Abstract The physical properties of polybutadiene vulcanizates have been measured as a function of polymer microstructure. Although the over-all properties of any one polybutadiene are determined by the relative ratio of cis, trans and vinyl units in the polymer chain, marked changes in physical properties do not occur until a relatively pure configuration is approached or unless the raw polymer displays crystallinity. Thus, polybutadienes containing more than 85 per cent cis, trans or vinyl units are characteristically different from each other and the differences are accentuated as the isomeric forms approach 100 per cent of a given configuration. Polybutadiene of 95 per cent cis configuration displays very low heat generation and high resilience (equaling natural rubber in these properties) and excellent abrasion resistance. trans-Polybutadiene (90 per cent), a crystalline plastic in the raw state, becomes rubbery after vulcanization. Gum vulcanizates possess high tensile strength, and tread stocks display high modulus and tensile strength, high hardness and fair hysteresis properties. Vulcanizates of amorphous 94 per cent vinyl polybutadiene are characterized by fair tensile properties, low hysteresis, and poor low temperature properties. Crystalline syndiotactic polybutadiene, 70 per cent vinly, displays much higher gum and tread tensile strengths than its amorphous counterpart. Amorphous polybutadienes containing less than 70–80 per cent of any one configuration are generally similar in most properties, and resemble emulsion polybutadiene in many respects. The wide range of properties of the various polybutadienes makes them suitable for many applications. cis-Polybutadiene is an excellent tire rubber, which has given as much as 40 per cent greater abrasion resistance than natural rubber in passenger tire tests. Heavy duty 10:00 × 20 truck tires fabricated with a 1:1 blend of cis-polybutadiene and natural rubber in the treads have given slightly better abrasion ratings and lower running temperatures than control tires fabricated entirely from natural rubber. Amorphous 80 per cent cis-polybutadiene has been found to possess exceptionally good low temperature properties, far superior to present arctic-type unsaturated elastomers, trans-Polybutadienes by virtue of their high modulus, high tensile strength, and high hardness could be utilized in the preparation of hard rubber goods, floor tiles, and shoe soles. While none of these polybutadienes is yet available commercially, their unusual properties and potential applicability in many areas should lead to their manufacture in the future.

A STUDY ON THE FRETTING FATIGUE LIFE OF ZIRCALOY ALLOYS

2008 ◽  
Vol 22 (11) ◽  
pp. 851-856
Author(s):  
JAE-DO KWON ◽  
DAE-KYU PARK ◽  
SEUNG-WAN WOO ◽  
YOUNG-SUCK CHAI
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
Fatigue Behavior ◽  
Fretting Fatigue ◽  
Mechanical Tests ◽  
Fatigue Tests ◽  
Cyclic Damage

Studies on the strength and fatigue life of machines and structures have been conducted in accordance with the development of modern industries. In particular, fine and repetitive cyclic damage occurring in contact regions has been known to have an impact on fretting fatigue fractures. The main component of zircaloy alloy is Zr , and it possesses good mechanical characteristics at high temperatures. This alloy is used in the fuel rod material of nuclear power plants because of its excellent resistance. In this paper, the effect of the fretting damage on the fatigue behavior of the zircaloy alloy is studied. Further, various types of mechanical tests such as tension and plain fatigue tests are performed. Fretting fatigue tests are performed with a flat-flat contact configuration using a bridge-type contact pad and plate-type specimen. Through these experiments, it is found that the fretting fatigue strength decreases by about 80% as compared to the plain fatigue strength. Oblique cracks are observed in the initial stage of the fretting fatigue, in which damaged areas are found. These results can be used as the basic data for the structural integrity evaluation of corrosion-resisting alloys considering the fretting damages.

HHC (Hitachi Hyper Valve): Corrosion Resistant, Withstands Erosion and Low CO Release

2004 ◽  
Author(s):  
Yoshihisa Kiyotoki ◽  
Mutuo Chigasaki
Keyword(s):  
Corrosion Resistance ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Base Alloy ◽  
Chemical Compositions ◽  
Valve Seat ◽  
Valve Body ◽  
Valve Disc ◽  
Metal Microstructure

In order to prevent valve performance deterioration by corrosion and wear against the seat (following, the valve-seat) of the valve-disc and the valve-body at fossil and nuclear power plants, a Co-base alloy is hard-faced onto the valve-seat. However, valve-seats deteriorate, for example, by corrosion, cracking and erosion. Moreover, the drift of the set point of the safety valves also occurs, by the phenomenon of Corrosion-Bonding. A valve-seat with excellent corrosion resistance, erosion toughness and mechanical toughness is sought. And, if possible, a low Co release rate material is preferred in nuclear power plants. Therefore, to improve valve performance, we manufactured a new valve named HHV with a valve seat, whose metal microstructure is different from that of conventional valve seats, within the range of chemical compositions of RCoCr-A (AWS). We also, evaluated the performance of the HHV Valve. We verified that HHV has improved valve performance. Moreover, we applied HHV under actual operating power plant conditions. The results show that HHV is superior to conventional valves in corrosion resistance, etc.

ICONE11-36481 Improvement in Maintainability and Reliability of a Valve Seat Material for Nuclear Power Plants

2003 ◽  
Vol 2003 (0) ◽  
pp. 42
Author(s):  
Shigeru Tachihara ◽  
Hiromitsu Sakamoto ◽  
Yoshihisa Kiyotoki ◽  
Akira Sakamoto ◽  
Mitsuo Chigasaki
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Valve Seat

Long Term Operation of Safety Valves at Pressures Near the Set Pressure

2017 ◽  
Author(s):  
L. Ike Ezekoye ◽  
Thomas Beagen ◽  
Brian S. Gordon ◽  
John W. Boufford
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Valve Seat ◽  
Term Operation ◽  
Design Function ◽  
Fast Transients ◽  
High System ◽  
Transient Events ◽  
The Impact

Safety valves in nuclear power plants provide over pressure protection of pressurized systems. Accordingly, these valves are required to open quickly and stably (i.e., open, relieve pressure and close) during postulated transients to protect the integrity of the protected systems. Typically, postulated transients are classified as fast or slow. Fast transients have high system pressurization rates that proceed very quickly thereby requiring the safety valves to pop open. On the other hand, there are transients that proceed very slowly that are less challenging to the system but may initiate leakage across the installed safety valve seat. There is very limited knowledge on the impact of prolonged operation of safety valves during slow pressurization accident events. The integrity and functionality of these valves during such slow pressurization events are often in question. This paper examines analytically the behavior and the integrity of safety valves during slow pressurization transient events at pressures near the valve set pressure. This paper considers extended periods of valve simmering that may progress to valve cycling (popping fully open) during such events. To validate the analytical performance prediction, steam tests were performed with safety valves which confirmed that these valves can operate extensively under slow pressurization transient events while maintaining their capability to perform their intended design function.

Evaluation of Mechanical Properties of the Reactor Pressure Vessel Materials Changes by Small Punch Test Application

2013 ◽  
Author(s):  
Jana Petzová ◽  
Martin Březina ◽  
Ľudovít Kupča
Keyword(s):  
Mechanical Properties ◽  
Pressure Vessel ◽  
Nuclear Power ◽  
Power Plants ◽  
Mechanical Tests ◽  
Reactor Pressure Vessel ◽  
Small Punch Test ◽  
Small Punch ◽  
Punch Test ◽  
Reactor Pressure

The reactor pressure vessel (RPV) is the most important component of nuclear power plants. RPV steel near the reactor core is subject of irradiation degradation due to the fast neutron flux. Irradiation processes are rather complex but after all the damage of the steel crystal lattice lead to the changes of RPV mechanical properties as well as the shift of the transition temperature to higher values. Hence, monitoring of the RPV material irradiation changes must be proved during the all nuclear power plant (NPP) operation. The new surveillance specimen programs (SSP) at all Slovak NPPs reactors included, among the standard mechanical tests, also new types of evaluation mechanical properties due to method Small Punch Test (SPT).

Air Pressure Test on Concrete with Nano-Cement

2019 ◽  
Vol 16 (2) ◽  
pp. 748-753
Author(s):  
Jemimah M. Carmichael ◽  
Prince G. Arulraj
Keyword(s):  
Particle Size ◽  
Tensile Strength ◽  
Nuclear Power ◽  
Power Plants ◽  
Air Pressure ◽  
Nano Particles ◽  
Hardened Concrete ◽  
Nano Materials ◽  
Split Tensile Strength ◽  
Pressure Test

Nanotechnology is an emerging area of research that has received a lot of attention for its ability to make use of the unique properties of nano-sized materials. The grain size of the nano particles will be in the order of 10–9 m (1–100 nm). Due to the very small particle size and extremely large specific surface area, nano particles have same remarkable properties. The use of nano materials for making concrete is of recent origin. Addition of nano materials in concrete can lead to significant improvements in the strength and durability of concrete. For nuclear power plants, concrete with high compressive strength, high split tensile strength, low porosity and high density are required. An attempt has been made to increase the compressive and split tensile strength of concrete by replacing a portion of cement with nano cement. M20, M30, M40 and M50 grades of concrete were cast. For each of these mixes, 10%, 20%, 30%, 40% and 50% of cement was replaced with nano- cement. Nano-cement was made by grinding the commercially available 53 grade pozzolona cement in the ball grinding mill. A scanning electron microscope was used to determine the particle size of the nano-cement produced. A hollow cylinder of the concrete was made with concrete containing nano materials. The Air pressure test was carried at on hardened concrete and the results were compared with that of normal cement concrete. The safe internal pressure for M50 concrete with 50% replacement of cement with nano-cement was found to be 13.3 kg/cm2, which 31.6% higher than that of the normal M50 concrete.

The Effects of Ion Implantation on the Surface Features of Inconel 600

1985 ◽  
Vol 43 ◽  
pp. 288-289
Author(s):  
John D. Rubio
Keyword(s):  
Grain Boundary ◽  
Ion Implantation ◽  
Nuclear Power ◽  
Power Plants ◽  
Surface Region ◽  
Selective Dissolution ◽  
Boundary Region ◽  
Near Surface ◽  
Inconel 600 ◽  
Steam Generator Tubing

The degradation of steam generator tubing at nuclear power plants has become an important problem for the electric utilities generating nuclear power. The material used for the tubing, Inconel 600, has been found to be succeptible to intergranular attack (IGA). IGA is the selective dissolution of material along its grain boundaries. The author believes that the sensitivity of Inconel 600 to IGA can be minimized by homogenizing the near-surface region using ion implantation. The collisions between the implanted ions and the atoms in the grain boundary region would displace the atoms and thus effectively smear the grain boundary.To determine the validity of this hypothesis, an Inconel 600 sample was implanted with 100kV N2+ ions to a dose of 1x1016 ions/cm2 and electrolytically etched in a 5% Nital solution at 5V for 20 seconds. The etched sample was then examined using a JEOL JSM25S scanning electron microscope.

Work structure in nuclear power plants

1983 ◽  
Author(s):  
Marjorie B. Bauman ◽  
Richard F. Pain ◽  
Harold P. Van Cott ◽  
Margery K. Davidson
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Work Structure
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