Nuclear Industry

1.Nuclear Fuel Industry.
U235 that can generate fission reaction in the natural uranium minerals has ratio of only 0.7%, it can only be used for the reactor after various machining process to make it to the product with the concentration up to 2%-4%U235, after operation of the reactor, unburned U235 in spent  fuel and the new produced Pu239 will require recycling technique process to reclaim them. A complete system of nuclear fuel industry includes uranium mineral mining-hydrometallurgy-concentration-reactor- chemical treatment, etc. in the whole recycling process of nuclear fuel, stainless steel and corrosion resistant alloy material are widely used, without proper stainless steel material, there will not be modern nuclear fuel industry.

(1)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. For the reason of alkali lixiviating, corrodibility is comparatively weak, using the common steel can be acceptable, but at the liquid-gas interface position, the baffle plate should use 0Cr17Ni14Mo2 as the material, it can prevent the corrosive pitting caused by splashing of sulfide. When using nitric acid for lixiviating, the material should be 18-8 Type Austenite stainless steel with intercrystalline corrosion resistance. When using sulfoacid for lixiviating, material should be Cr-Ni Austenite stainless steel containing molybdenum or molybdenum-copper compound, under the corrosive conditions; it is required to use the deposit strengthening Austenite stainless steel.

Application conditions of stainless steel in the uranium Hydrometallurgy factory

Technique
Material
Position
Lixiviating slot for Alkali lixiviating technique Carbon steel 0Cr17Ni12Mo2 Stainless steel used for the liquid-gas interface of the lixiviating slot
HNO3 lixiviating,90-100℃
UO2(NO3)2Evaporator 120-145℃
0Cr18Ni11Nb,0Cr18Ni10Ti
00Cr19Ni10
0Cr18Ni9
0Cr23Ni13Nb
Lixiviating slot and pipe lines
Evaporator
Pipes
H2SO4lixiviating 0Cr17Ni12Mo2
00Cr19Ni10
Mixer
Extraction tank, pipe lines
Acid adding pipe of the lixiviating tower 00Cr26Ni35MoCuTi Acid adding pipe, flange fastener
Air blowing pipe, plasm drainage pipe, overflow pipe
Denitration kettle with organic solvent extraction 0Cr19Ni0
0Cr18Ni11Nb
0Cr18Ni9
Denitration kettle
Denitration kettle
Mixer

(2)Refining of Uranium

Replacing U3O8 produced by hydrometallurgy with UF4, and change UF4 to UF6,there are the wet method and dry method technique in the actual production.
The technique process for producing UF4 with dry method, equipment material shall bear the corrosion by nitric acid, nitric acid steam, UO2(NO3)2, , material shall vary according the working procedures, details see the table below:

Material of technique equipments for refining uranium

Procedure name
Equipment
Material
U3O8Nitric acid solving
Solving capsule, pipes
0Cr18Ni11Nb
00Cr19Ni10
UO2(NO3)2Extraction
Reaction extracting barrel and pipe pump
00Cr19Ni10
Carpenter20
Vaporizing and drying
Vaporizing tank
Pipes
00Cr19Ni10
0Cr23Ni13
Denitration
Denitration tank
Mixer
00Cr19Ni10、0Cr18Ni11Nb
0Cr18Ni9
UO3(1000℃)
Reactor
Mixer
0Cr23Ni13、0Cr17Ni12Mo2
0Cr17Ni14Mo2、ILLium R,HastelloyC
Hydrogen fluoride
Reactor
Mixer
Inconel 600,Monel No.1 alloy,
Pure Ni No.1,HastelloyC

(3)Concentrating Uranium.

In using the gaseous diffusion to separate U235,the isolating cover of the compressor should use 0Cr35Ni65Al. The high speed rotating cylinder for centrifugal separation uses the Martensite aged steel.

(4)Retreatment of nuclear fuel.
Giving chemical treatment to spent fuel of the reactor and the radiant nuclear fuel of the production reactor, and separating U and Pu, the chemical treating process to the dangerous nuclear fission product is called nuclear fuel retreatment, or after treatment.

For nuclear fuel retreatment, presently mature technique is water method, the reclaiming process is constructed of three parts including the unshell of fuel components, fuel solving and the separating/ reclaiming of fuel. Material problem of the last part can refer to section of “Refining of Uranium”. For the two part at the front, the technique medium has strong corrodibility, so the equipments, pipes, pumps, valves of the nuclear fuel after treatment factory are all made of stainless steel and corrosion resistant alloy. The material will differ according to the technique medium condition, shown in the following table:

Corrosion resistant material in the unshell technique of nuclear fuel retreatment

Technique Name
Medium components
Material
NifleX Solving the jacket
NifleX Solving the jacket
Solving the UO2-graphite granular fuel
1MHNO3-2MHF
60℃,0.3MHF的HF-HNO3
3MHF-23MHNO3, boiling
00Cr25Ni50Mo6CuTi(BMI-HAPO-20)
0Cr35Ni65 Alloy
0Cr18Ni11Nb,0Cr23Ni13Nb,00Cr19Ni10
Zirlfex technique for solving zirconium-tin alloy jacket and the zirconium-base fuel
6MNH4F-1MNH4NO3
3MHN4·HF2
0Cr23Ni13Nb
HasfelloyF
Ni-O-Nel825
00Cr19Ni10
Sulfex Solving stainless steel jacket
4-6MH2SO4
Ni-O-Nel825
HasfelloyF
HAPO-20,Carpenter20 Alloy
Durex Solving stainless steel jacket
5MHNO3-2MHCL
Ti

Dissolving of fuel core
 Normally solution similar or close to the unshell is used for dissolving. In dissolving the metal uranium, uranium oxide, and uranium-aluminum fuel, nitric acid is widely used, material of solving capsule commonly use 0Cr23Ni13Nb,00Cr19Ni10 and Carpenter20 alloy.

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, the latter has excellent corrosion resistance, and operating all post- treatment factories use it as structure material of reactor (vaporizing and concentrating).

2.Nuclear power Industry.
(1)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:

Conditions of stainless steel of pressurized water reactor (PWR)

Name
Material
Reactor component
Main cooling pipe
Control rod driving machine
Water press device
Auxiliary heat exchanger
0Cr17Ni14Mo2,0Cr18Ni10Ti Nitrogen control 00Cr18Ni10
0Cr18Ni10Ti,0Cr17Ni12Mo2 Nitrogen control 00Cr17Ni12
00Cr13Ni5Mo,0Cr17Ni4Cu3Nb Nitrogen control 304、1Cr13
0Cr18Ni9
0Cr18Ni9
Steam generator
0Cr18Ni10Ti,Inconel600
Inconel800,Inconel690

(2)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 2 1/4 Cr-1Mo, 0Cr18Ni10Ti, 0Cr17Ni14Mo2,0Cr18Ni9, Incology800, etc.
 
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