stainless steel in nuclear
DESCRIPTION
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TOPIC
PRESENTATION OVERVIEW
INTRODUCTION PRODUCTION CLASSIFICATION CHARACTERISTIC APPLICATION IN NUCLEAR INDUSTRY APPLICATION IN NUCLEAR POWER INDUSTRY
INTRODUCTION Stainless steels constitute a group of high-alloy steels based on the Fe-Cr, Fe-Cr-
C, and Fe-Cr-Ni systems.
It must contain a minimum of 10.5 wt% chromium.
The chromium allows formation of a passive surface oxide that prevents oxidation and corrosion.
Some steels that contain less than 11 wt% Cr, such as the 9 wt% Cr alloys used in power generation applications.
Stainless steels also have good resistance to oxidation, even at high temperatures.
Some high chromium alloys (25 to 30 wt%) can be used at temperatures as high as 1000oC (1830oF).
CONT……..
Stainless steels are used in a wide variety of applications, such as a power generation, in nuclear industry, chemical and paper processing, and in many commercial products.
PRODUCTION OF STAINLESS STEEL Stainless steel is produced in a wide variety of shapes and sizes. Melting of stainless steels was revolutionized by the introduction
of argon-oxygen decarburization (AOD) and vacuum-oxygen decarburization (VOD) techniques.
Using the AOD process, a mixture of argon and oxygen is injected into the motlen steel. The oxygen combines with the carbon to form carbon monoxide to achieve the desired carbon content.
The process using VOD is similar, except that the argon carrier gas is not necessary and oxygen is injected directly into the melt. By this process we achieve the desired carbon content and reduce the residual sulfur content to as low as 0.001 wt%.
Following the refining process, the steel can be poured into ingot molds or transferred directly to a continuous casting machine.
CLASSIFICATION OF STAINLESS STEELS
Stainless steels are commonly divided into five groups.
1.Martensitic stainless steels
2. Ferritic stainless steels
3.Duplex stainless steels
4.Austenitic stainless steels
5.Precipitation-hardening stainless steels
CHARACTERISTICS OF STAINLESS STEELS
• Higher work hardening rate• Higher ductility• Higher strength and hardness• Higher corrosion resistance• Possess higher tensile and yield strengths• Good ductility and formability• Good machinability
APPLICATION IN NUCLEAR INDUSTRY Hydrometallurgy of Uranium. Uranium minerals should undergo
working procedures including acid pickling/ alkali pickling-solvent lixiviating-solvent extracting-denitration, to form U3O8 in the end. The application of stainless steel in the above technique process is shown in the following table.
Material Position
Carbon steel 0Cr17Ni12Mo2
liquid-gas interface of the lixiviating slot
00Cr19Ni10 Evaporator
0Cr18Ni9 Pipes
0Cr26Ni35MoCu
Ti
Acid adding pipe, flange fastener
Air blowing pipe, plasma drainage
pipe, overflow pipe
CONTI….. Dissolving of fuel core In dissolving the metal uranium, uranium oxide, and uranium-
aluminum fuel, nitric acid is widely used, material of solving capsule commonly use 0Cr23Ni13Nb， 00Cr19Ni10 .
Treating equipment for high radioactive waste liquid
The high radioactive waste liquid is the compound medium containing various waste gas and various high radioactive liquids, it is highly corrosive, and often contains HNO3, sulfate radical, iron ions, in treating this kind of waste liquid, leakage must be strictly prevented, in case the environment is polluted, material of the equipments should be 00Cr18Ni9 and 00Cr25Ni20Nb.
APPLICATION IN NUCLEAR POWER INDUSTRY
Light-water reactor (LWR) The reactor used to provide power for generating electricity, it is commonly cooled by water, and is generally called light-water reactor (LWR). Light-water reactor can be divided to as pressurized water reactor (PWR) and boiling-water reactor, PWR is the mainstream type.The following table shows stainless steel application conditions for pressurized water reactor (PWR) nuclear power plant.
Name MaterialReactor component 0Cr17Ni14Mo2
Main cooling pipe 0Cr18Ni10Ti
Auxiliary heat exchanger 0Cr18Ni9
CONTI….Sodium Cooling Reactor The fuel jacket material is improved 316 stainless steel that contains Ti. 00Cr18Ni12Mo2 is used in the sodium capsule and thermal loop . According to the difference of temperature, the evaporator and super heater unit can use 0Cr18Ni10Ti, 0Cr17Ni14Mo2， 0Cr18Ni9 . Primary Coolant Pipes Of Nuclear Power Plant
Primary coolant pipe is a key component of nuclear power plant (NPP) and usually made from cast duplex stainless steels, for example Z3CN20.09M DSS.
Chemical composition of Z3CN20.09M cast duplex stainless steel (wt %).
Fission Reactors (Type 316LN austenitics stainless steel (0.03% C max, 17.0-18.0% Cr, 12.0-12.5% Ni,
2.30-2.70% Mo, 0.06-0.08% N, 0.001-0.002% B, 0.030% Cu max, 0.25% Co max, 0.15% Nb+Ta+Ti max), which has been used as a fuel element cladding material in fast fission reactors).
C Si Mn P S Cr Ni Cu Co Nb+T
a
B Mo N Ti
0.024 1.09 1.11 0.023 0.0039 20.16 9.06 0.031 0.026 0.066 0.0001 0.26 0.033 0.0027
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Steam Power Plants .stainless steel is use in steam power plant containing 9-12Cr steels for boiler (super heater and reheater tubing, thick-walled pipes for steam lines and headers)
Turbine Components.1. Rotors(12Cr-MoVNbB steel , 12Cr-MoVNbW steel)2. Casings and Valve Bodies(9Cr-MoVNbW , 12Cr-MoVNb)3. Turbine Blades(12Cr-MoVNbW ,12Cr-MoV )4. Bolts(12Cr-MoNiV,12Cr-MoV )