CZ2013178A3 - Method of cooling and temperature control of cold trap for cleaning liquid metals as a coolant for 4th generation power reactors and fusion reactors as well as apparatus for making the same - Google Patents

Abstract

Method of cooling and regulation of cold trap temperature for liquid metal cleaning as a coolant for power reactors IV. The generation and the fusion reactors are such that the liquid metal (8), continuously in the circuit passing through the cold trap, is cooled therein by the cooling medium (3) to a temperature close to its solidification state, where crystallization occurs during the cooling process impurities from this liquid metal (8) that are trapped in the cold trap. The liquid-containing refrigerant (3) is subjected to boiling and subsequent condensation of the liquid metal (8) while cooling the liquid metal (8), the impurities of the liquid metal (8) depositing on its surface. The apparatus for carrying out this method comprises a primary vessel (1) into which a liquid metal inlet (9), continuously flowing through a plurality of internal baffles (5, 7) in the primary vessel (1), opens in the region of the housing under its cover (4). ) to the outlet (10) of the liquid metal (8). This primary vessel (1) is arranged inside a closed outer secondary vessel (2) which is at least partially filled with liquid cooling medium (3). The secondary vessel (2) is provided with closable inlets to allow the liquid coolant (3) and the inert cover gas to be topped up above the coolant level (3) and further with a safety valve to protect the secondary vessel (2) while increasing the pressure inside the secondary vessel (2) above defined limit. The secondary vessel (2) is provided with means for regulating the temperature of the liquid cooling medium (3) controlled by electric heating, wherein a flow condensation is arranged above the surface of the cooling medium (3) within the upper portion of the secondary vessel (2).

Description

Method of cooling and temperature control of cold trap for purification of liquid metals as coolant for power reactors IV. generation and fusion reactors and equipment for carrying out this process

Field of technology

The present invention relates to a method for cooling and regulating the temperature of a cold trap for the purification of liquid metals as coolants for power reactors IV. generation and fusion reactors and equipment for carrying out this process in the separation of corrosive impurities of these liquid metals.

State of the art

Due to the extreme temperatures required to sustain the thermonuclear reaction and the neutron fluxes and gait radiation produced, the vacuum vessel of the fusion reactor must be intensively cooled and shielded. The cooling and shielding system of the inner wall of the fusion reactor serves this purpose. <

Suitable substances for intensive heat dissipation are liquid metals, (sodium lithium, eutectic Pb-Li, eutectic Pb-Bi); For Tokamak ITER, the eutectic Pb-Li is considered as a refrigerant, which serves as a heat transfer medium and at the same time as a source of tritium, which is formed by radioactive transformation and serves as a fuel for the fusion reaction. Liquid metals have a high heat transfer coefficient and a high temperature, boiling / boiling at atmospheric pressure, and are therefore suitable refrigerants in systems with high heat generation. Their disadvantage is that they cause significant corrosion in the system. In a radioactive environment, corrosive impurities are then activated and cause contamination of the entire system, which leads to complications in the operation and maintenance of the entire facility. Thus, one of the main tasks in liquid metal systems is to ensure the purification of the liquid metal.

A device which is used to clean liquid metal from _corrosive impurities is, for example, a cold trap. This eliminates corrosive impurities in the areas where they cool, i.e. on the cooled surfaces of the construction materials or directly in the melt. The existing cold traps work mainly on the principle of capturing the excluded impurities on the wire network, where these impurities settle. The wire mesh reduces the cleaning capacity of the cold trap, increases the pressure drop and threatens complete clogging of the trap, which would lead to undesirable downtime of the equipment. The cooling of these cold traps is realized by gas, especially air.

Due to the relatively low heat transfer coefficient to the cooling gas (Large heat transfer area and at the same time large temperature difference are required to remove the required heat.) The eutectic Pb-Li alloy, for example, has a highly variable density depending on the temperature, leading to inhomogeneity of the temperature field. lower than the solidification temperature of the liquid metal, and thus there will be a gradual freezing in the cold trap area.

The essence of the invention

The invention relates to a method for cooling and controlling the temperature of a cold trap for the purification of liquid metals as a coolant for power reactors IV. generation and fusion reactors, where the liquid metal, continuously passing through a cold trap, is cooled in it by a cooling medium to a temperature close to its solidification temperature, at which it retains a liquid state and where during the cooling process impurities from this liquid metal crystallize. caught in a cold trap. The essence of '' J. The invention relates to the fact that the cooling medium, which is in a liquid state, is exposed to boiling and subsequent condensation of its vapors during the cooling of the liquid metal in a cold trap, the impurities of the liquid metal settling on its surface.

The advantage is the uniform and almost constant temperature field of the heat transfer surface of the cold trap at high heat removal intensities. Cooling is realized in three circuits. The primary circuit consists of its own liquid metal, the secondary circuit consists of a chamber where the coolant boils, which cools the primary circuit, and the tertiary circuit consists of a condenser, where condensation formed by boiling the liquid in the secondary circuit. As an example, at a cooling air velocity of 2 4 »3« mb; '. , · ·; · F í í «-i: t <

m / s in the specific geometry of the cold trap reaches the heat transfer coefficient on the air side values of 10/110 W / m ² .K. During boiling, the value of the heat transfer coefficient is at the level of 10,000 W / m ² K.

The level of the liquid metal in the cold trap is regulated by adjusting the height of the overflow of the flowing liquid metal at its outlet from the cold trap.

The liquid metal is selected from the group consisting of Na, Li, Pb, eutectic Pb-Li, eutectic, bsiPíoé-ct

Pb-Bi. The liquid cooling medium is selected from the group of liquids whose boiling point is controllable by their pressure in the range of the solidification temperature of the cooled liquid metal and the desired operating temperature in the liquid metal circuit.

The present invention also relates to an apparatus for carrying out the method described above for separating corrosive impurities of these liquid metals. It comprises a primary vessel into which a supply of liquid metal, which flows continuously through a system of internal baffles in the primary vessel to the liquid metal outlet, opens in the region of the jacket below its lid, this primary vessel being arranged inside a closed outer secondary vessel which is at least partially filled with liquid refrigerant. and wherein the secondary vessel is provided with closable inlets for the possibility of replenishing the liquid refrigerant and inert cover gas above the level of the refrigerant and a safety valve to protect the secondary vessel when the pressure inside the secondary vessel rises above a defined limit. The secondary vessel is provided with means for regulating the temperature of the liquid refrigerant by controlled electric heating, a flow condenser of refrigerant vapor being arranged in the upper part inside the secondary vessel above the surface of the refrigerant.

The method of flowing liquid metal through the baffles is characterized in that the liquid metal enters the trap through a tube on the outer diameter of the primary circuit. By boiling the liquid on the secondary side, the liquid metal cools and flows through the system of chambers towards the central outlet pipe.

In one possible embodiment of the invention, the primary vessel is a cylindrical steel weldment, wherein the liquid metal supply is formed by an inlet pipe terminating in the liquid metal surface area under the lid of the primary vessel, wherein there is a set of internal partitions in the direction from the shell to the center of the primary vessel. formed by concentrically arranged cylinders which are alternately, at both their ends, w 4 *>

unequally terminated to allow the flow of liquid metal fed to the outer intermediate space of the primary vessel meanderingly gradually to its center, where the outlet pipe for discharging the liquid metal from the primary vessel is located.

In another embodiment of the invention, the primary vessel is a block-shaped steel weldment, wherein the liquid metal supply is formed by an inlet pipe terminating in the liquid metal surface area below the primary vessel lid, where there is a set of inner baffles , which are alternately terminated at both their ends to allow the flow of liquid metal fed to the outer interspace space of the primary vessel meanderingly sequentially to its center, where an outlet pipe for discharging liquid metal from the primary vessel is located.

In both of these embodiments, the primary vessel may advantageously be located symmetrically within the outer secondary vessel and the refrigerant vapor condenser may be formed by a shaped finned tube for condenser coolant flow, the inlet and outlet of which are welded to the outer vessel shell.

The means for regulating the temperature of the liquid coolant by controlled electric heating may be formed by an electric heater situated on the shell of the secondary vessel or in the space of the secondary vessel filled with liquid coolant.

The apparatus for carrying out the above-described method for separating corrosive impurities of these liquid metals may further comprise a primary vessel into which a liquid metal supply flowing continuously through a system of internal baffles in the primary vessel to the outlet of the liquid metal opens in the region of the shell below its lid. is arranged inside a closed outer secondary vessel and the space of the secondary vessel is at least partially filled with liquid refrigerant, the secondary vessel being incorporated in a closed circuit and provided with a refrigerant supply and vapor discharge to a condenser allowing condensate to return to the secondary vessel.

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An example of an embodiment of the device according to the invention is shown in the accompanying drawings. In Fig. 1A this device is in a side view, in Fig. 1C in a vertical section and in Figs. 1B and 1D in two different horizontal sections.

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Examples of embodiments / invention

Cold trap is a device that is used to separate corrosion products from liquid metals. In the trap, the liquid metal is cooled to a temperature which is close to its melting point, while a continuous flow of liquid metal through the cold trap is ensured. At the same time, at a given temperature, corrosion impurities crystallize, which are trapped in the cold trap. If a trap is clogged, which is detected by an increase in trap pressure by clogging or reaching a limit of retained activity (more retained impurities will be radioactive X _# when used in ITER or another nuclear reactor), the trapped metal is allowed to solidify and the entire equipment is replaced.

The whole cold trap device can be divided into three elementary circuits. The primary circuit consists of a flow section with baffles, where the liquid metal itself is cleaned. The secondary part consists of a volume with coolant. The tertiary circuit serves to remove heat from the secondary circuit of the trap and consists of a cooler in which the tertiary coolant flows.

In this type of trap, cooling is realized by boiling the coolant on the outer shell of the primary circuit. This achieves a high heat dissipation intensity without the need for a larger temperature difference between the melt and the coolant. At the same time, it is ensured that the temperature on the cooled walls and in the entire primary part of the trap will not be lower than the solidification temperature of the eutectic and therefore the eutectic will not freeze. The required cooling temperature (coolant boiling) is easily adjustable by regulating the pressure on the secondary side.

The flow part of the primary circuit consists of concentric tubes / baffles that define the flow inside the trap. Liquid metal is not trapped throughout. Thus, a level is created above which the shielding gas is. The level is regulated by the pressure of the shielding gas or by a suitable location of the outlet pipe (overflow). The baffles are drilled above the surface to allow pressure equalization in all chambers.

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The liquid metal enters the trap through a tube on the outer diameter of the primary circuit and flows through a system of chambers which are separated by baffles to the central outlet tube. The impurities crystallize on the cooled walls of the primary circuit or directly in the eutectic, and these impurities then settle on the surface of the liquid metal due to the lower density.

For a secondary circuit, the secondary side is a more appropriate name because it is not a circuit in the true sense of the word. The secondary side is formed by an annular vessel which surrounds the primary circuit itself and which forms one part with the trap. The coolant itself and the shielding gas are present in the secondary circuit. The coolant level is about the same as the liquid metal level. The required pressure in the secondary part is regulated by admitting or discharging the shielding gas. The secondary side is equipped with a condenser on which the secondary refrigerant vapor condenses. The steam which is formed during the cooling of the liquid metal by the boiling of the liquid thus condenses on the condenser condenser, which forms the tertiary circuit. This ensures that steam generation does not increase the pressure on the secondary side.

Finally, the tertiary sector also needs to be clarified. The tertiary circuit consists of a condenser, which is designed to ensure condensation of vapors generated by boiling the secondary coolant.

In the ITER fusion reactor project, one of the research subjects is a circuit called the Test Blanket Module. The liquid eutectic Pb-17Li flows in the circuit. The purpose of this circuit is to cool the primary wall of the reactor and at the same time produce fuel, tritium with its subsequent extraction. An essential part of the circuit is a cold trap, which serves to retain corrosive products and thus prevents the spread of these radioactive particles throughout the circuit.

Below is a specific implementation case, including all operating parameters. The following table shows the design of possible operating parameters of the trap for the case of cleaning the Pb-17Li eutectic. In this case, the cooling of the cold trap is realized by water.

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------------------—-—---------—--- Primary circuit of the cold trap - eutectic Pb-17Li Nominal inlet eutectic temperature [° C] 550 Maximum inlet eutectic temperature [° C] 600 Nominal temperature of cooled eutectic [° C] 300 Minimum temperature of cooled eutectic [° C] 275 Maximum temperature of cooled eutectic [° C] 350 Nominal eutectic pressure [MPa] 0.3 Maximum eutectic pressure [MPa] 0.6 Minimum eutectic pressure [MPa] 0.1 Nominal eutectic flow [kg / min] 1 Maximum flow eutectic [kg / min] 10 Secondary side - cooler I Coolant Water Nominal temperature (saturation) [° C] 300 Maximum coolant temperature [° C] 350 Minimum (operating) temperature [° C] 275 Minimum temperature [° C] ambient temperature Nominal pressure [MPa] 8.6 Maximum pressure [MPa] 20 Minimum operating pressure [MPa] 5.9 Flow [kg / s] 0 Tertiary circuit - cooler II Coolant Water Inlet temperature [° C] 25 Max outlet temperature [° C] 90 Nominal pressure [MPa] 0.2 Maximum pressure [MPa] 1 Flow [kg / s] as required*

* The liquid flow in the tertiary circuit must be such that it does not boil in the circuit. This must be calculated from the heat balance at the maximum operating flow and the maximum operating temperature of the eutectic.

The device consists of a closed steel outer cylindrical primary vessel 2, inside which a closed steel cylindrical primary vessel 1 with an upper lid 4 and a bottom 6 is arranged symmetrically. In the space of the secondary vessel 2 there is a liquid cooling medium is provided with closable inlets for the possibility of replenishing the liquid refrigerant 3 and cover gas (argon, helium _, nitrogen) above the surface of the refrigerant 3 and a pressure relief valve inside the secondary vessel 2. An electric heater is located in the space filled with refrigerant 3.

Inside the secondary vessel 2, above the surface of the refrigerant 3, a refrigerant vapor condenser H is arranged, formed by a finned tube for the flow of coolant 12 of the condenser _11t (water, oil), the inlet and outlet of which are welded to the vessel shell 2. Marloterm) It is possible, if necessary, to increase the temperature on condenser 11 above 100 £ C at atmospheric pressure in the circuit.X

The primary container 2 is formed by a steel weldment which comprises a lower cylindrical inner partition 5 welded with its lower end to the bottom 6 of the primary container 1, the upper end being situated under the lid 4 at a certain distance from its surface. The weldment of the primary vessel 2 further comprises two upper cylindrical inner baffles 7, welded with their upper ends to the lid 4, the lower ends of which are above the bottom 6 of the primary vessel 1. This assembly of inner baffles 5, 7 forms for liquid metal 8 (e.g. eutectic Pb ^Li X) The primary vessel 1 is provided with inlet pipes 9 and outlet pipes 10 for the passage of liquid metal 8. A primary gas supply (inert gas, e.g. Ar, He) also opens into the primary vessel 1. which allows the level of liquid metal 8 to be formed in the primary vessel 1 at the desired height and the entire volume of the primary vessel 1 is not filled. In the inner space of the primary vessel 1 there are temperature sensors determined by the height of the outlet pipe 10 in this primary vessel 1. In an alternative embodiment, it may be: ·. * · Í «» · • 9 «• Y o;

the inner space of the primary vessel 1 is completely filled with liquid metal 8, but M represents a somewhat reduced ability to retain the displaced impurities from the liquid metal 8. This is due to the absence of surface tension at the surface where the vast majority of impurities settle.

The primary vessel 1 may in an alternative embodiment be in the form of a cuboid with plate-shaped inner baffles 5, 7 for the flow of liquid metal 8 between them. This corresponds to the shape of the outer secondary vessel 2 and the condensers 11 of the refrigerant vapor 3.

Industrial applicability

The principle of cooling liquid metals by boiling the cooling liquid can be used, for example, for a cold trap for cleaning eutectics in the ITER Tokamak blanket, where it will serve as a device for cleaning Pb-17Li eutectics from corrosive impurities. If the cold trap and the entire TBM circuit are verified, such equipment will also be usable for subsequent fusion reactors such as DEMO and potential other power reactors. A cold trap based on this principle can also be used in the operation of experimental loops with liquid metals, where it is possible to use a cold trap to determine the efficiency and reliability of the entire cleaning process, which is necessary to comply with appropriate chemical regimes during experiments. Furthermore, this device can be used for all IV energy reactors. generations that use liquid metals as a refrigerant. b <LFŘ, SFR.

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List of reference marks

... primary container

... secondary container

... liquid refrigerant II side

... primary container lid

... lower inner bulkhead

... the bottom of the primary vessel

... upper inner partition

... liquid metal

... liquid metal supply

... liquid metal outlet

... capacitor

... condenser coolant

Claims (11)

PATENT CLAIMS 1. Method of cooling and temperature control of cold trap for purification of liquid metals as coolant for power reactors IV. generation and fusion reactors, where the liquid metal (8), continuously passing through a cold trap, is cooled in it by a cooling medium (3) to a temperature close to its solidification temperature, at which it retains a liquid state and where during the cooling process impurities crystallize from this liquid metal (8), which are trapped in the cold trap, characterized in that the cooling medium (3), which is in a liquid state, is exposed to boiling and subsequent condensation of its vapors during the cooling of the liquid metal (8) in the cold trap, wherein the impurities of the liquid metal (8) settle on its surface. Method according to claim 1, characterized in that the level of the liquid metal (8) in the cold trap is regulated by adjusting the height of the overflow of the flowing liquid metal (8) at its outlet from the cold trap. Method according to claims 1 or 2, characterized in that the liquid metal (8) is selected from the group consisting of Na, Li, Pb, eutectic Pb-Li, eutectic Pb-Bi. Method according to claim 1 or 2, characterized in that the liquid cooling medium of the bipol (3) is selected from the group of liquids whose boiling point is controllable by their pressure in the solidification temperature range of the cooled liquid metal (8) and required operating temperatures in the liquid metal circuit (8). Apparatus for carrying out the method according to one of Claims 1 to 4, characterized in that it comprises a primary vessel (1) into which a liquid metal supply (9) (8) opens continuously in the region of the casing under its lid (4). flowing through a system of internal baffles (5, 7) in a primary vessel (1) to an outlet (10) of liquid metal (8), said primary vessel (1) being arranged inside a closed outer secondary vessel (2) which is at least partially filled with liquid refrigerant (3), and wherein the secondary vessel (2) is provided with closable inlets for the possibility of replenishing the liquid refrigerant (3) and inert cover gas above the level of the refrigerant (3) and a safety valve to protect the secondary vessel (2) pressure inside the secondary vessel (2) above a defined limit, and wherein the secondary vessel (2) is provided with means for regulating the temperature of the liquid coolant (3) by controlled electric heating, ) a flow condenser (11) of refrigerant vapor (3) is arranged. Device according to claim 5, characterized in that the primary vessel (1) is made of a cylindrical steel weldment, wherein the liquid metal inlet (9) is formed by an inlet pipe terminating in the liquid metal surface area (8) under the lid. (4) a primary vessel (1), where in the direction from the shell to the center of the primary vessel (1) a set of internal baffles (5, 7) formed by concentrically arranged cylinders which are alternately terminated unequally at both ends to allow flow of liquid metal (8) fed into the outer intermediate space of the primary vessel (1) meanderingly sequentially to its center, where the outlet pipe for discharging the liquid metal (8) from the primary vessel (1) is located. Device according to claim 5, characterized in that the primary vessel (1) is made of a block-shaped steel weld, wherein the liquid metal inlet (9) is formed by an inlet pipe terminating in the liquid metal surface area (8) under the lid. (4) a primary vessel (1), where in the direction from the shell to the center of the primary vessel (1) a set of internal baffles (5, 7) formed by plates which are alternately at both ends are unequally terminated to allow the flow of liquid metal (8) fed into the outer intermediate space of the primary vessel (1) meanderingly gradually to its center, where an outlet pipe for discharging liquid metal (8) from the primary vessel (1) is located. Device according to claim 6 or 7, characterized in that the primary container (1) is situated symmetrically inside the outer secondary container (2). Device according to claim 5, characterized in that the refrigerant vapor condenser (11) is formed by a shaped finned tube for the flow of coolant (12) of the condenser (11), the inlet and outlet of which are welded to the outer vessel shell (11). 2). • 13·· Device according to claim 5, characterized in that the means for regulating the temperature of the liquid cooling medium (3) by controlled electric heating is formed by an electric heater situated on the shell of the secondary vessel (2) or in the space of the secondary vessel (2) filled with liquid cooling medium (3). Device according to claim 5, characterized in that it comprises a primary vessel (1) into which a supply (9) of liquid metal (8) flowing continuously through a system of internal baffles (5) opens in the region of the casing under its lid (4). 7) in the primary vessel (1) to the outlet (10) of the liquid metal (8), where this primary vessel (1) is arranged inside the closed outer secondary vessel (2) and the space of the secondary vessel (2) is at least partially filled with liquid cooling medium (3), wherein the secondary vessel (2) is incorporated in a closed circuit and is provided with a supply of refrigerant (3) and an outlet of its vapors to the condenser (11), enabling the return of condensate of these vapors to the secondary vessel (2).