Fuel element can of fast reactor with liquid metal heat carrier

FIELD: physics.

SUBSTANCE: invention is designed for increasing operation parametres and life cycle of active zone of a reactor due to the maximum fuel burnup, improved reliability and operation safety of maintenance of nuclear power stations. Fuel element can of a fast reactor with liquid metal heat carrier includes a metal tube of vanadium alloy with titanium, chrome and unavoidable impurities. External and internal tube surfaces are coated with stainless ferrite steel. Vanadium alloy components are taken at a given ratio. In particular, titanium to chrome ratio lies within 2.2 to 1.8 range. Between vanadium alloy and stainless ferrite steel a 6-8 mcm thick transition layer of solid solution of vanadium alloy with stainless ferrite steel is formed.

EFFECT: improved radiation, corrosion and heat resistance and mechanical properties of fuel element can in a fast reactor with liquid metal heat carrier.

3 cl, 5 dwg

 

The invention relates to nuclear energy, in particular for fuel element cladding nuclear fast reactors with liquid metal coolant, and can be used to increase operating parameters and resource reactor core, maximum burnup of nuclear fuel, improve the reliability and safety of operation of nuclear power plants.

A known fuel cladding made of a material is austenitic steel. This steel has a satisfactory combination of strength, heat resistance (up to temperatures of ˜650°C), corrosion resistance, good processability and development in industry [Sensation, Issolvin, Vpolonskiy. The problems of developing advanced materials for fuel cladding of fast reactors, " in proc. Nuclear power plants of Russia. 60 years of the nuclear industry. Moscow, 2005, s-335] (table).

To do this, the shell material characteristic propensity for high-temperature radiation embrittlement (WTRO) and vacancy swelling that is not possible with the required efficiency (burn-up fuel ≥17% T.A., temperature ˜750° (C) to use it in systems with liquid metal coolant, in particular, sodium or lead.

Heat-resistant properties of ferritic-martensitic, austenitic steels and vanadium alloys
Material contentLong durability σDPon the basis of 10,000 hours, depending on temperature
Temperature, °
500550600650700750
Long-time strength, MPa
The ferritic-martensitic steel:
12% Cr, 1% Mo, W, V
20015060---
Austenitic steel:
16% Cr, 15% Ni, 0.5% of Nb,-1601108040-
0,004
The alloys of the V-Ti-Cr:
92% V 4% Ti, 4% Cr-370230180140100
85% V 10% Ti, 5% Cr--300-180-

Known shell made of a structural material - chromium ferritic-martensitic stainless steel, well-proven at temperatures up to ˜550° [Sensation, Issolvin, Vpolonskiy. The problems of developing advanced materials for fuel cladding of fast reactors, " in proc. Nuclear power plants of Russia. 60 years of the nuclear industry. Moscow, 2005, s-335].

For this material with low heat resistance at temperatures of more than 550-600°With a propensity for low-temperature embrittlement (NTRO) and alloys during neutron irradiation at temperatures over 550°that prevents the use of these materials at the operating temperature of promising fast reactors ˜750°C.

The most promising materials for fuel element cladding reactor is quickly neutrons are alloys based on vanadium.

For vanadium and alloys on its basis the characteristic propensity for interaction with impurity oxides and nitrides liquid metal coolants, leading to degradation of mechanical properties, which limits the use of these alloys in conditions of contact with liquid metal coolants.

A prototype of the selected fuel cladding reactor fast neutron reactors with liquid metal coolant: lead or sodium containing metal tube with end caps made of radiation resistant chromium steel, made of at least two layers of different metals in which the metal tube is made of vanadium alloy V-Ti-Cr, covered with outer and inner sides of a chromium stainless steel type XI7 [a utility model Certificate No. 23521, MKI G21C 3/06].

The disadvantage of the prototype is that this shell does not guarantee the required level of properties of the fuel element. It is known that alloying titanium suppresses the low-temperature radiation embrittlement. However, alloys with a high concentration of Ti prone to high temperature embrittlement. Alloying with chromium reduces the effect of high-temperature embrittlement, but the increase in the chromium content again increases the susceptibility of the alloys to NTRA. Also in the composition of the material of the prototype is not who felt the influence of impurities on the degradation of mechanical properties and swelling.

It is known that when the total content of oxygen and nitrogen less than 0.05 wt.% in these alloys under neutron irradiation increases the swelling, and when the content is more than 0.2 wt.% increased tendency to embrittlement. In the material description of the prototype are also missing features interoperability layer base and cover defining the functionality of the shell.

The task to be solved by the invention is to increase the radiation resistance and corrosion resistance, increased structural stability, and improved mechanical properties and heat resistance of the fuel cladding of fast reactor liquid metal cooled.

To solve this problem the fuel cladding reactor fast neutron reactors with liquid metal coolant contains a metal tube made of vanadium alloy including titanium, chrome and inevitable impurities, coated her inner and outer surface, made of ferritic stainless steel, and the components are vanadium alloy are in the following ratio, wt.%:

titanium8,0-12,0
chrome4,0-6,0
the amount of oxygen and nitrogenof 0.05-0.2
vanadiumthe rest,

moreover, the ratio of titanium to chromium is selected in the range from 2.2 to 1.8, and between vanadium alloy and ferritic stainless steel transition layer formed solid solution of vanadium alloy with a ferritic stainless steel of a thickness of from 6 to 8 microns.

In the private embodiment, the coating thickness of the ferritic stainless steel outer and inner surface of the pipe is 30 to 70 μm.

In another private version for the coating material used ferritic stainless steel type X17 or HT.

The shell is made of a material with the chemical composition of the base in which the ratio of content of the main alloying components Ti/Cr is maintained within ˜2:1, and the total content of oxygen and nitrogen in the metal structure is not less than 0.05 wt.% and not more than 0.2 wt.%, improves the properties of ductility, toughness and heat resistance.

Covering the basics of vanadium alloy chromium ferritic steel type X17 or HT with the zone of diffusion between the layers of shell thickness ˜6-8 μm, which represents a solid solution components vanadium alloy and ferritic steels, improves corrosion resistance in environments coolants (sodium, lithium, lead) and in the aquatic environment of the cooling pool for spent fuel elements.

Thus, p is shown, what are the essential features of the invention allow to achieve more complex characteristics that determine performance of elements of the nuclear power plants in liquid metal cooled at temperatures of ≥750°C.

The study of the properties of the shell material was conducted at the experimental smelts.

In figure 1, figure 2 and table on the example alloy 12X17/V-4Ti-4Cr/12X17 shown short-term mechanical properties of the sheath material, the relevant requirements of the standards.

Figure 1 shows the temperature dependence of the tensile strength (upper curve) and yield strength (lower curve) for three-layer material.

Figure 2 presents the temperature dependence of the total elongation (upper curve) and uniform elongation (lower curve) for three-layer material.

Figure 3 presents the mechanical properties of the alloys V-4Ti-4Cr and V-10Ti-5Cr.

Figure 4 shows the distribution of concentrations of major alloying elements in the material package manufactured according to the developed technology for two-layer and three-layer materials using durable and radiation-resistant vanadium alloy clad corrosion-resistant ferritic stainless steel. The final thickness of the package, strain hot rolling, is 0.4 mm Thickness obrazovash is the action scene of the zone of diffusion bonding of materials is ˜ 6-8 μm. The proposed material with the ratio of the alloying components fundamentals of Ti/Cr≈2:1 (figure 3) compared with the most developed industry-alloy V-4Ti-4Cr has higher strength properties similar to plastic and a higher heat resistance (table).

Figure 5 presents the surface appearance of the destruction of samples alloy V-4Ti-4Cr tested in argon, which contained ˜6 wt.% oxygen and nitrogen.

Properties of chromium steels and alloys of vanadium depends on composition and structure, but many of the physical properties (thermal conductivity, coefficient of linear expansion and, most importantly, by setting thermal stability of these materials are close to each other. These components of the alloy form with iron solid solutions, which is especially important for the welding process.

Visual inspection of the tested samples showed that under the same test conditions (heating rate, speed, tension and other) of the analyzed samples are destroyed equally with the formation of a neck. The failure zone has the form of a slanting cut at an angle of 45° to the longitudinal axis, which indicates the viscous destruction,

Figure 5 shows the fracture of the sample after mechanical tests on the gap in argon. It is seen that the sample tested in argon, also destroyed with the formation of the neck at an angle of 45° the longitudinal axis. However, the side surface of the sample, there are tears, i.e. there is a small crack on the side surface so as to laterally vanadium alloy was not protected from the environment that speaks about the reaction of the vanadium substrate with impurities in argon containing up to 6 wt.% impurities of oxygen and nitrogen.

When tested in vacuum cracking was not observed, confirm the validity of the protection vanadium alloy V-Ti-Cr steel H.

Thus, as a result of a comprehensive experimental study indicates that the proposed shell allows to provide in comparison with the known shells of similar purpose of the comprehensive improvement of the most important technological and functional characteristics that provide high performance structural elements of nuclear power plants operating in complex radiation and corrosive conditions.

1. The fuel cladding of fast reactor liquid metal cooled containing a metal tube made of vanadium alloy including titanium, chrome and inevitable impurities, by coating its outer and inner surfaces, made of ferritic stainless steel, characterized in that the components are vanadium alloy are followed by the third value, wt.%:

titanium8,0-12,0
chrome4,0-6,0
the amount of oxygen and nitrogenof 0.05-0.2
vanadiumrest

moreover, the ratio of titanium to chromium is selected in the range from 2.2 to 1.8, and between vanadium alloy and ferritic stainless steel transition layer formed solid solution of vanadium alloy with a ferritic stainless steel of a thickness of from 6 to 8 microns.

2. Shell according to claim 1, characterized in that the thickness of the coating of the inner and outer surfaces of the pipe ranges from 30 to 70 microns.

3. The membrane according to claims 1 and 2, characterized in that the coating material used ferritic stainless steel type X17 or HT.



 

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