RU2799242C1 - Apparatus for high-temperature corrosion studies of the physical and chemical properties of materials in molten salts - Google Patents

Abstract

FIELD: corrosion testing.

SUBSTANCE: invention relates to equipment for identifying the corrosion resistance of structural materials for high-temperature devices, mainly used for handling melts of alkali metal halide used in the pyrochemical and pyrometallurgical processing of spent nuclear fuel. The device consists of a support platform, containers for heated crucibles, three metal pipes not connected to each other, each of which is configured for hermetic connection with a container for heated crucibles at one end. Threaded spires are mounted on the support platform, on which transverse disks of heat-reflecting material are screwed vertically in several tiers, through which metal pipes pass. A set of at least three vertical spires is inserted into each of the metal pipes of the device, fixed relative to each other in height by parallel transverse disks made of heat-reflecting material, whereas the device is placed in a cylindrical vessel closed with a removable lid with through holes for the passage of electrodes, and also through hole for evacuation and gas purging of a cylindrical vessel, ending with ports with removable sealing plugs made of vacuum rubber.

EFFECT: ability to study the physical and chemical properties of materials in molten salts outside the boxed unit, which expands the experimental base for studying the corrosion-electrochemical behaviour of metal materials used in electrochemical technologies.

1 cl, 6 dwg

Description

The invention relates to equipment for testing the corrosion resistance of structural materials for high-temperature devices, mainly used for working with alkali metal halide melts used in pyrochemical and pyrometallurgical processing of spent nuclear fuel.

The chemical aggressiveness of alkali metal halide melts requires a detailed study of the mechanism of destruction of materials and their corrosion-electrochemical behavior.

For these purposes, an installation has been developed for conducting high-temperature corrosion studies of the physicochemical properties of materials in molten salts, the prototype of which is an installation for determining the corrosion rate of materials in molten salts, known from [RU 2758772, publ. 01.11.2021].

A known installation is a device containing a support platform, containers for heated crucibles, three metal pipes not connected to each other, each of which at one end is made with the possibility of a tight connection with a container for heated crucibles, and at the other with a removable heat-reflecting cover . Threaded spiers are mounted on the support platform, on which transverse disks made of heat-reflecting material with three holes are screwed vertically in several tiers for metal pipes to pass through them.

Non-connected metal pipes provide physical separation of working areas, which is necessary in the conditions of work with melts of alkali halide used in pyrochemical and pyrometallurgical processing of spent fuel, making it possible to carry out parallel corrosion tests simultaneously.

Using a well-known setup, researchers are able to simultaneously conduct three parallel, independent experiments on high-temperature corrosion studies of the physicochemical properties of materials in molten salts, with the exception of electrochemical measurements, such as, for example, determining the corrosion potential by potentiometry, electrochemical diagnostics by voltammetry and others

Metal pipes insulated with a lid make it possible to conduct a qualitative and quantitative analysis of all volatile products formed during the experiment, which expands the technological capabilities of the installation. Covers with heat-reflecting screens installed on the upper edges of the pipes prevent heat loss.

The indicators of corrosion resistance of structural materials of reactors in molten salts are affected by oxygen-containing impurities present in these corrosive media, traces of moisture, multiply charged transition metal cations. Therefore, to conduct experiments on a well-known installation, pre-cleaned and certified samples of salt electrolyte and the material under study are used. Salt melts are prepared and purified outside the facility, which ultimately complicates the technology for studying the corrosion resistance of reactor structural materials. In addition, not only the experiments, but also the assembly of the facility, including the hermetic joining of pipes with the corresponding containers for crucibles, as well as the fastening of the transverse disks on the threaded studs by tightening with metal bushings, must be carried out in an inert atmosphere, in a special hermetic box, which is extremely inconvenient.

In the absence of a unified standard and unified devices for conducting high-temperature corrosion studies of the physicochemical properties of halide melts that are extremely susceptible to thermal hydrolysis, including alkali metal fluorides, there is a need to develop an apparatus that is easy to use, allowing high-temperature corrosion studies of the physicochemical properties of metallic materials. in molten salts using an electrolyte - a corrosive medium of the required composition and purity, prepared and purified in the same apparatus.

Thus, the technical problem to be solved by the invention lies in the absence of a convenient apparatus design that allows high-temperature corrosion studies of the physicochemical properties of metallic materials in molten salts using an electrolyte - a corrosive medium of the required composition and purity, prepared and purified in the same apparatus.

To solve this problem, an apparatus for conducting high-temperature corrosion studies of the physicochemical properties of materials in molten salts is proposed, containing a device consisting of a support platform, containers for heated crucibles, three metal pipes not connected to each other, each of which is made with the possibility of hermetic connection with a container for heated crucibles, threaded spiers are mounted on the support platform, onto which transverse disks of heat-reflecting material are screwed vertically in several tiers, through which metal pipes pass. The device differs in that a set of at least three vertical spiers is inserted into each of the metal pipes of the device, fixed relative to each other in height by parallel transverse disks made of heat-reflecting material, while the device is placed in a cylindrical vessel closed with a removable lid with through holes for the passage of electrodes, as well as a through hole for evacuation and gas purge of a cylindrical vessel, ending with ports with removable sealing plugs made of vacuum rubber.

Non-connected metal tubes of the device provide physical separation of the working areas necessary for working with alkali metal halide melts, which makes it possible to simultaneously conduct three independent experiments on corrosion high-temperature studies of the physicochemical properties of materials in molten salts. The fact that the device, which consists of a platform with threaded pins, containers for heated crucibles, metal pipes with a set of vertical pins, is placed in a cylindrical vessel designed for evacuation and hermetic gas purge, simplifies the assembly and operation of the apparatus, including the hermetic docking of pipes with appropriate containers. under the crucible.

Unlike the known device, the use of which, including assembly, must be carried out in a sealed box, the claimed device can be used outside the sealed box, that is, in open fume hoods.

The technical result provided by the invention is the ability to study the physicochemical properties of materials in molten salts outside the boxed installation, which expands the experimental base for studying the corrosion-electrochemical behavior of metallic materials used in electrochemical technologies.

The invention is illustrated in the following figures: FIG. 1 shows the apparatus, general view; figure 2 - apparatus in the assembly process; figure 3 - cover of the apparatus, perspective view; figure 4 - cover of the apparatus, side view; figure 5 - cover of the apparatus, bottom view; figure 6 - cover of the apparatus, top view.

Installation for high-temperature corrosion studies of the physical and chemical properties of materials in molten salts, contains a device consisting of a support platform 1, containers 2 in the form of a glass for heated crucibles with salt electrolyte and test samples, three metal pipes 3 not connected to each other, each of which it is made with the possibility of tight connection with the container 2. On the support platform 1, threaded spires 4 are mounted, on which transverse disks 5 of heat-reflecting material are screwed vertically in several tiers, through which metal pipes 3 pass.

A set of at least three vertical spiers 6 is inserted into each of the metal pipes 3, fixed relative to each other in height by parallel transverse disks 7 made of heat-reflecting material. The device consisting of a platform 1 with threaded pins 4 and disks 5, containers 2, metal pipes 3 with a set of pins 6 is placed in a cylindrical vessel 8, closed with a hermetic lid 9 made of PTFE. The lid 9 is made three-stage in height, while the stage 10 contains three protrusions 11 intended for insertion into metal pipes 3, the stage 12 is designed to support the lid on the vessel 8. The lid 9 has three sets of three through holes 13, coaxial to the pipes 3, intended for the passage of electrodes immersed in the molten salt in the crucible 2, as well as a hole 14 for evacuating and purging the vessel 8 with gas. All holes in the cover 8 end with ports 15, which are sealed with plugs 16 made of vacuum rubber.

For experimental verification of the claimed installation and statistical processing of the results, parallel independent tests were carried out simultaneously in all three metal pipes of the device. To do this, a crucible with a salt composition and samples of the test material was placed in the lower part of each tube 3. The setup was assembled outside the boxed setup, placed in a high-temperature furnace, evacuated, and then vessel 8 and metal pipes 3 were filled with argon. High-temperature studies of the physicochemical properties of materials in molten salts were carried out, namely, the corrosion potentials of nickel alloys in a melt of lithium and potassium chlorides were determined relative to a silver chloride reference electrode at a temperature of 500 to 700°C.

Thus, the invention makes it possible to study the physicochemical properties of materials in molten salts outside a boxed installation, which expands the experimental base for studying the corrosion-electrochemical behavior of metal materials used in electrochemical technologies.

Claims (1)

Apparatus for conducting high-temperature corrosion studies of the physicochemical properties of materials in molten salts, containing a device consisting of a support platform, containers for heated crucibles, three non-connected metal pipes, each of which is made with the possibility of tight connection with the container at one end under the heated crucibles, threaded spiers are mounted on the support platform, onto which transverse disks of heat-reflecting material are screwed vertically in several tiers, through which metal pipes pass, characterized in that a set of at least three vertical spiers is inserted into each of the metal pipes of the device, fixed relative to each other in height by parallel transverse disks made of heat-reflecting material, while the device is placed in a cylindrical vessel, closed with a removable lid with through holes for passing electrodes, as well as a through hole for evacuating and purging the cylindrical vessel with gas, ending with ports with removable sealing plugs from vacuum rubber.

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