US3438431A - Heat exchanger system - Google Patents

Description

A ril 15, 1969 s. DREYER ET Al.

HEAT EXCHANGER SYSTEM I of 5 Sheet Apnl 15, 1969 s. DREYER ET AL 3,438,431

HEAT EXCHANGER SYSTEM Filed Aug. 25, 1967 Sheet ,8 of 5 si -ii S 'IIIIIIIIIIIIIIII April 15, 1969 5 DREYER ETAL HEAT EXCHANGER SYSTEM Sheet Filed Aug. 25, 1967 April 15, 1969 5 DRE-YER ET AL 3,438,431

HEAT EXCHANGER SYSTEM Filed Aug. 25, 1967 Sheet 4 of 5 April 15, 1969 s. DREYER ET AL 3,438,431

HEAT EXCHANGER SYSTEM Filed Aug. 25, 1967 Sheet 5 of 5 United States Patent 3,438,431 HEAT EXCHANGER SYSTEM Siegfried Dreyer, Kreuzbergstrasse, 506 Steininenhruck; Rudolf Harde, Huettenstrasse 1; Walter Jansmg, Beethovenstrasse 12; Friedel Kalkoiten, Hermann- Loens-Strasse 17; Hans Mausbeck, Diakonissenweg 24; and Werner Schnittker, Koelner Strasse 47, all of Bensberg, Germany Filed Aug. 25, 1967, Ser. No. 663,339 Int. Cl. G21c 9/02, 19/32; F28f 19/00 US. 'Cl. 165-134 23 Claims ABSTRACT OF THE DISCLOSURE The invention covers a heat exchanger system, particularly for use in a nuclear reactor plant, which comprises one or several heat exchanger units of single or multipart design. When leaks or pipe ruptures occur in such systems, e.g. for the media sodium/ water, the problem is to evacuate the reaction products and liquid and gas volumes consequent upon such leaks or pipe fractures in such a way that the plant is not destroyed or damaged or its safety impaired; the reaction products exhibit extraordinarily high pressures and velocities which in turn pressurize and accelerate the liquids and gases.

Background of the invention The known proposals for safety measures of this type are directed at leading the highly pressurized media into expansion tanks through special pipes when certain pressure values are exceeded. Such measures are however insufiicient on their own, as the reaction, e.g. of liquidmetal/water, especially sodium with water, takes place at extraordinarily high speed; a pressure increase to the first maximum taking place within a very short space of time, roughly in the order of 10 sec. The effects of this pressure can damage or destroy the pipework and appliances of the entire circulation system, particularly any heat generating equipment used such as an intermediate heat exchanger for primary and secondary fluids, such as liquid-metal. As activated liquid-metal could escape into the atmosphere on this occurring, a dangerous situation for human beings and animals could arise over a wide radius; this must be avoided, and the invention is directed towards this problem.

Summary of the invention In accordance with the invention, the heat exchanger units of a heat exchanger system are followed by a buffer vessel through which a returning liquid-metal fiows continuously, the storage chamber of this vessel being separated from a pipe leading into it by a rupture disc, this pipe leading to a separator. The pipe discharging liquidmetal from the buffer vessel has an orifice plate, throttle, or similar device, and is connected behind this point to a surge tank by a branch line, the surge tank always containing a certain level of liquid-metal pressurized by an inert gas buffer.

When a leak or pipe rupture occurs in the heat exchanger, the system prevents the highly pressurized liquidmetal and reaction products from entering the low-pressure pipework section of the liquid-metal circulating system. When a water or steam-conducting pipe springs a leak or ruptures, the medium, which is under a substantially higher pressure, enters the flow space of the lowerpressure liquid-metal and the chemical reaction products, particularly hydrogen, cause a volume expansion. This displaces the liquid-metal from the heat exchanger; the displaced liquid-metal flows at high speed and under high pressure into the manifold leading to the surge tank.

3,438,431 Patented Apr. 15, 1969 The orifice plate in the surge tank infeed pipe acts as a throttle and substantially reduces the pressure of the liquid-metal, considerably reducing the stress placed upon the following pipe-work of the circulation system, particularly the pipe section leading to the surge tank. The orifice plate has no effect on gas, steam, or biphase mixture. In order to ensure that only liquid metal can reach the orifice plate in spite of the advancing reaction front, the orifice plate is preceded by the buffer vessel, which always contains such a quantity of liquid-metal that the liquid level can never drop below the level of the orifice as such on an accident occurring and the liquid level dropping rapidly.

Measures must therefore be adopted to restrict the amount of liquid-metal driven out of the butter vessel towards the surge tank to the permissible value. The rupture disc serves as a pressure-relieving element by allowing the volumes of liquid-metal propelled along by the reaction front, and the following highly-pressured volumes of steam, gas, and reaction products, to escape from the buffer vessel. When this disc ruptures, a plug of liquid metal flows through the pipe leading to the separator. The separator retains the non-gaseous reaction products and the liquid metal. At this point, it must be expected that the buffer vessel will also be subject to high pressure from the steam circuit. The arrival of the sodium plug in the separator is followed by a stream of hydrogen or steam, which can be mixed with reaction products or liquid-metal mist. The pressure in the buffer tank then drops rapidly.

A preferred version of the bufier vessel is a vertical design, the full top plate of the vessel is the rupture disc separating the butter vessel as such from a transfer chamber in which the pipe leading to the surge tank terminates. The liquid-metal infeed pipe terminates in the upper part of the buffer vessel but below the rupture disc, and the liquid-metal outflow pipe is connected with the lower section of the bufier vessel. With this design, the volume of gas exiting at high speed increases the pressure in the liquid-metal to such a degree that the rupture disc gives way and the liquid-metal level in the buffer vessel drops. The liquid-metal flows from the buffer vessel into the pipe leading to the surge tank and passes through the orifice plate, the pressure and flow velocity of the volumes of the liquid-metal still flowing through the circulating system being limited to the extent that the pipe-work and fittings of the system cannot be damaged or defects caused.

An additional feature of the invention is the inclusion of a rapid shut-off element in the pipe conveying the liquid-metal from the butter vessel, this element being located between the orifice plate and the branch pipe leading to the surge tank. When this shut-01f element is closed on a defect occurring, the circulating system is protected against damage from any reactions that may occur.

A further feature of the invention covers an appreciable enlargement of the buffer vessel transfer chamber between the rupture disc and the outflow line to equal roughly twice the diameter of the bufier vessel proper. This provides an expansion chamber which permits expansion of the liquid-metal plug and accelerated entry of the gaseous and vaporous medium, so allowing the inflowing volumes of gas and reaction products to enter the separator more rapidly and with a lower pressure loss.

A further feature of the butter vessel covered by the invention is the connection of the liquid-metal infeed pipe to the upper portion of this vessel. By this means, the conveyed gases and reaction products are admitted in the near vicinity of the rupture disc and above the liquid level forming during this period.

In an alternative design covered by the invention, the liquid-metal infeed pipe is entered through the lower portion of the butter vessel and runs up the inside of this vessel to terminate immediately beneath the rupture disc. This arrangement has an additional effect in that the gases collecting in the buifer vessel are entrained ejector-fashion and thus evacuated more rapidly. In turn, this can also restrict the formation of a liquid-metal plug.

A modified design in accordance with the invention is the arrangement of a primary separator on the transfer chamber with a primary separator gas discharge pipe leading to a following separator. This design keeps the dimensions of the buffer vessel to a minimum, and calls for restriction of the high reaction pressure phase to the shortest period possible. All measures which permit rapid evacuation of the reaction gases and quick separation of the liquid-metal mist from these reaction gases and water vapor are suitable for this purpose. The primary separators main task is to accept the volume of liquid-metal not retained in the buffer vessel, and in particular the liquid-metal plug expelled by the pressure of the gases and steam, and separate this as quickly as possible from the gases and vapors allowing these to escape into the following separator via the connecting pipe.

A particular advantage is gained by a further embodiment of the invention in which the pipe leading from the transfer chamber to the primary separator, and connected tangentially to the latter, is kept very short, thus keeping the maximum length of the liquid-metal plug down to the smallest possible value.

The buffer vessel with primary separator can also be designed in such a way that the upper portion of the vertical cylindrical vessel takes a horizontal pipe with a cross-section corresponding to the diameter of the buffer vessel, such pipe leading to the primary separator and accommodating the rupture disc.

A further advantageous feature in accordance with the invention is the branching of the infeed pipe shortly ahead of the separator, the two branches entering the separator tangentially on opposite sides and pointing in the same direction of rotation. This produces a more uniform feed of the medium containing liquid metal, vapor, hydrogen, and reaction products, and reduces vibration, which would otherwise call for a greater technical outlay in order to render the design and arrangement of the separator dependable in operation. A further embodiment of the invention is the provision of a branch pipe from the liquidmetal discharge line coming from the buffer vessel, such branch being located immediately behind the orifice plate and leading to a separator and accommodating a rupture disc. With this facility, the liquid metal passing the orifice plate on a defect occurring in the system has an avenue of escape along which only very minor liquid masses have to be accelerated. The substantial reduction in the masses to be accelerated thus achieved produces acceleration values greater by a factor of 10 to 100 and a corresponding reduction in the time needed to reach the maximum flow speed. This permits the orifice plate to achieve its fuel throttling effect in a much shorter space of time.

A further design feature of the heat exchanger plant in accordance with the invention covers the installation of non-return valves in the liquid-metal infeed line to one or several heat exchanger units which close automatically on the flow direction being reversed, so preventing liquid-metal flowing from the heat generally equipment to the heat exchanger units in question, as well as blocking the flow of water, steam, or reaction products, on reactions taking place between liquid-metal and water or steam on pipes fracturing. When these nonreturn valves are fitted in common infeed lines to several heat exchanger units, the advantage gained is that no stationary reaction zones can form, as the reaction pressure being converted into speed can divert into the unit next to the affected heat exchanger unit, so distributing the volume of accelerated liquid, reaction products, and gas between the neighboring units and thus effecting a pressure drop. This also creates a moving reaction front, which does not locally heat the pipe walls to the same extent as would a stationary reaction zone.

The invention further covers other measures on the hot side of the liquid-metal circulation system, i.e. in the infeed pipework section leading from the heat source to the heat exchanger, for discharging the returning reaction products and the volumes of liquids in question. For this purpose, it is proposed in accordance with the invention that a buffer vessel for liquid-metal be installed in every manifold leading to the heat exchanger units; the buffer vessel being continuously under flow and isolated by a rupture disc from a pipe leading from the buffer vessel to a separator, and also isolated by a further rupture disc installed in a branch line from the manifold located ahead of the buffer vessel and leading to a further separator.

This design renders a superfluous non-return valves in the pipes leading to the heat exchanger units. The arrangement of the buffer vessel on the hot side produces the advantage that the returning liquid-metal can be absorbed and separated at maximum speed, just as on the cold side, without any reactions affecting the heat generation plant, in particular any intermediate heat exchanger that may be used.

The effect of this buffer vessel and paired separator is the same as on the cold side. The liquid-metal collects in the lower portion of the buffer vessel unless it was discharged as a plug into the separator together with the steam and gaseous mediums when the rupture disc burst. A separate relief passage is provided for the liquid-metal in the lower part of the buffer vessel. However, a further difliculty is experienced in that the direction of flow has to be reversed in the infeed pipes to make the pressure relief system effective. This reversal is favored by the fact that a separation cycle is provided between the heat generation unit and the buffer vessel; the separation action rapidly dropping the pressures in that transfer is effected into the branch line on the rupture disc bursting. A further embodiment of the invention is, therefore, the fitting of a nozzle in the line leading to the branch pipe, such line being kept as short as possible. The nozzle effects only a slight pressure loss when the medium is flowing in the normal direction and a high pressure loss on this flow being reversed.

According to a further design feature covered by the invention, the transfer chamber between rupture disc and discharge pipe can be substantially larger, e.g. up to twice the diameter of the buffer vessel.

In accordance with further design features, a primary separator can be attached to the buffer vessel transfer chamber; the gas discharge pipe of this separator leading to the following separator, the connection to the transfer being of horizontal design and leading to the primary separator and entering the latter tangentially.

In accordance with a further feature of the invention, the buffer vessel is of cylindrical, vertical design, the upper portion taking a horizontal pipe equivalent in cross-section to the diameter of the buffer vessel, such horizontal pipe accommodating the rupture disc and leading to the primary separator.

In a modified design covered by the invention, the arrangement is such that the pipe evacuating liquid-metal terminates in the upper portion of the buffer vessel at a point immediately below the rupture disc. This arrangement has an ejector effect on the liquid-metal, gaseous, and vaporous mediums flowing out of this pipe, so entraining further gaseous and vaporous mediums flowing out of this pipe, so entraining further gaseous and vaporous components and liquid-metal mist and conveying them into the separator.

A special arrangement of the apparatus covered by the invention is the connection of two or more heat exchanger units and their buffer vessels, which are arranged ahead of the manifolds for liquid-metal, to a common liquid-metal feed pipe, each branch pipe featuring a nozzle with a minor pressure loss in the normal operating flow direction and a high pressure loss in the reversed flow direction. This arrangement improves the relieving effect, so that when the flow from the heat exchanger system is reversed, the liquid first passes through the first nozzle at a high pressure loss, enters the branch line with a considerably lower pressure, and then passes through the nozzle with a minor pressure loss-no great resistance being met to take effect on the pressure relief system of the unaffected plant section. A particularly favorable effect is achieved by the fact that accelerations towards the pressure relieving system of the parallel heat exchanger facility are considerably higher than those in the direction of the heat generator since the volumes of liquids to be conveyed are substantially lower.

In accordance with a further feature of the heat exchanger system, the liquid-metal discharge line(s) of each of several heat exchanger units feature hydrogen bubble indicators. This provides for rapid detection of any holes, e.g. measuring 0.01 to about 0.5 mm., being formed in the water/steam pipes of the heat exchanger units when the rapid shut-off valves are closed. When defects of this nature occur, the reactions between liquidmetal and water cause the formation of hydrogen which is entrained in the form of bubbles; these bubbles are registered by the indicators mentioned above.

Further objects, features, and the attending advantages of the invention will become apparent when the following description is read in connection with the accompanying drawing.

Brief description of the drawing FIGURE 1 shows a schematic representation of the heat exchanger system in accordance with the invention;

FIGURE 2 shows a section through the buifer vessel from FIGURE 1;

FIGURE 3 shows a section through a buffer vessel in accordance with FIGURE 2 but of modified design;

FIGURE 4 shows a section through a buffer vessel with following primary separator;

FIGURE 5 shows a heat exchanger system of modified design when compared to that shown in FIGURE 1 and with a buffer vessel on the hot side;

FIGURE 6 shows a heat exchanger system in accordance with FIGURE 4 which features a bulfer vessel on the hot side preceded by a primary separator; and

FIGURE 7 shows a heat exchanger system in accordance with the invention comprising two systems connected to a common infeed manifold.

Description of the embodiments In the heat exchanger system in FIGURE 1, pipe 1 carries the sodium coming from an intermediate heat exchanger (exchange mediums preferably primary sodium/ secondary sodium) at a temperature of approximately 560 C. A rapid shut-off element such as control valve 2 in pipe 1 permits the rapid closure of pipe section 1 on liquid-metal/water reactions occurring as a result of pipe failure and protects such system from reaction effects. The following pipework section 3 serves as a distributing network; pipe 4 branches off from this network and leads to the manifold 5. A non-return or check valve 6 is located in pipe section 4; this non-return valve closes immediately when liquid-metal/ water reactions occur and isolate the distributing network 3 from the manifold ipe 5. P Infeed pipes 7 branch from the manifold 5 to the heat exchanger units 8; the latter are of two-tube design, i.e. the sodium fiows through the outer tube and enters the manifold through transfer pipe 9.

An alternative arrangement provides for an infeed pipe 7a leading direct from distributing pipe 3 to each heat exchanger unit 801, each infeed pipe 7a accommodating a non-return valve 6. Further, the heat exchanger units 8a can be joined in pairs by a connecting pipe 7b. The individual heat exchanger units 8a are connected by individual branches 9a to main branch 11, which also receives the manifold 10. Hydrogen bubble detectors 40 are installed in branch lines 9a and manifold 10a. These hydrogen detectors are used for the detection of hydrogen bubbles in the sodium lines. On a defect occurring, hydrogen can be transferred from the water/steam pipes into the sodium lines through pinholes of various sizes in the steam/ water pipe walls.

Pipe 12 feeds water for steam generation. A rapid shutoff valve 13 is used to cut off the water feed in case of danger. Water infeed manifold 14 has several branches 15 which feed the heat exchanger units 8, 8a with water. The generated steam is conveyed through steam lines 16 to the steam manifold 17, which also features a rapid shutoff valve 18.

After passing through the heat exchanger units 8, 8a, the sodium has been cooled down to approximately 300 C.; it then leaves the heat exchanger system through line 11 and enters the buffer vessel 13; line 11 terminates in the upper portion of the buffer vessel chamber 20.

The buffer vessel chamber 20 is isolated at the top from the transfer chamber 22 by a rupture disc 21 (see FIG- URES 2 to 4). A connecting line 23 leads to the separator 24 and terminates in transfer chamber 22. Connecting line 23 branches into lines 23a and 23b, which enter the separator 24 tangentially and pointing in the same direction of rotation. The vaporous and gaseous media are evacuated through line 25, and the collected liquid-metal can be tapped out through line 26, whihc has a shut-off device. Line 25 has apertures 39 in the interior of the separator; these apertures permit the discharge of vaporous and gaseous media even when the end of the pipe is submerged in the sodium.

The liquid-metal collected in buffer vessel chamber 20 is evacuated through line 27, which has a restrictor or an orifice plate 28. Line 27 also has a rapid shut-off valve 29 and a branch line 31 leading to the surge tank 38; an inert gas buifer above the sodium level in the surge tank 38 is maintained at a selected pressure.

On an internal pipe fracture occurring in heat ex changer unit 8 or 8a, the relevant non-return valves 6 are immediately actuated to block the sodium distributing line 3. The presure peak ahead of the rapid shut-off or non-return valves 6 is reduced by the grouped entry lines 7a, and, what is even more important, the creation of a stationary reaction zone and consequently the endangering of the outer casing of heat exchanger units 8, 8a is avoided.

The reaction zone then moves from lines 9, 9a, 10, 10a into outlet manifold 11. The remaining shut-off elements 6 also close, blocking entry manifold 3. Shortly before entry of the reaction zone into buffer vessel chamber 20, rupture disc 21 gives way and the sodium ascends to the separator 24 through lines 23, 23a, and 23b. On the reaction zone entering transfer chamber 22, the sodium (sodium plug) above the reaction zone is forced into the separator 24 at high speed. The increase of the transfer chamber space 22 immediately above the rupture disc 21 prevents the formation of a solid plug of sodium and thus any excessive loading of the separator 24. The volume of the buffer vessel 19, the extension of the transfer chamber 22, the orifice plate 28, and the gas volume in the surge tank 32 are so dimensioned that the secondary sodium system, and in particular the intermediate heat exchanger, is not endangered. The dosing effect of orifice plate 28 behing the buffer vessel 19 and the cushioning action of the gas buffer in the surge tank 32 prevent an excessively high pressure increase in the secondary sodium system.

The centrifugal effect of the sodium in the separator is virtually cancelled out by the division of the infeed line into branches 23a, and 23b, and by its entering the separator at two opposite points simultaneously, such inlets pointing in the same direction of rotation.

FIGURE 2 shows the details of the buffer vessel 19. It comprises the chamber 190, the upper portion of which receives sodium infeed line 11. Sodium discharge line 27, which has an orifice plate 28, terminates in the lower portion. The buffer vessel chamber 19c is closed at the top by a flange arrangement 21a which also serves as the mounting element for the rupture disc 21. The increased space 22 above the rupture disc serves as a transfer chamber and is connected by connecting pipe 23, through which the sodium is fed to the separator 24 (not shown here).

FIGURE 3 shows a modified arrangement of buffer vessel 19. Again in this arrangement, the cooled sodium is fed to buffer vessel chamber 20 which is separated from the transfer chamber 22 by a rupture disc 21. The connecting line 23 leads from the transfer chamber 22 to the separator 24 (not shown here).

In contrast to the arrangement as shown in FIGURE 2, the liquid-metal infeed line 11 is connected with the lower part of the vessel 19c and is led vertically upwards through the vessel chamber 20 to terminate immediately below the rupture disc 21. Corresponding to the design as shown by FIGURE 2, the liquid-metal is evacuated from the lower portion of the vessel chamber 20 by line 27, which has an orifice plate 28.

FIGURE 4 shows a further modified arrangement of buffer vessel 19. In this arrangement, a primary separator 33 is located ahead of the buffer vessel 19. This buffer vessel comprises the buffer chamber 20, the lower portion of which receives the liquid-metal infeed line 11 upward vertically. The lower portion of the buffer vessel chamber 20 receives the discharge line 27 in which the orifice plate 28 is located.

A branch line 34 leads sideways from the upper portion of the buffer vessel chamber. The diameter of branch line 34 is equivalent to the cross-section of the vessel; this branch line accommodates the orifice plate 21.

Primary separator 33 is connected to branch line 34, the gas discharge line 35 of the primary separator leading to the sepaartor 24 (not shown here). The gas discharge line 35 is open at the bottom end and has suitable apertures 35a to evacuate reaction gases even when the sodium level rises to cover the bottom opening. The primary separator 33 has a discharge line 26a for liquidmetal; this discharge line is equipped with a shut-off element (see FIGURE 6).

FIGURE shows a further modified version of the heat exchanger system. In this arrangement, a branch line 36 is arranged in discharge line 30 between the orifice plate 28 and the rapid shut-off valve 29, such branch line 30 leading to a sepaartor (not shown here) and featuring a rupture disc 37.

The mass to be accelerated is substantially reduced by branch line 36; thus, acceleration values higher by a factor of to 100 are achieved in the line as a considerable proportion of the liquid-metal volumes can escape through branch line to the separator; the velocity through rapid shut-off valve 29 to the heat generation source changing only very slowly.

A further improvement of the heat exchanger system as described is obtained by the inclusion of a continuous-flow buffer vessel 19a on the hot side of the liquid-metal circuit in the manifold 1a, 3. In the same way as with the buffer vessel 19, the chamber 20 of buffer vessel 19a is separated from the transfer chamber 22 by a rupture disc 21. A connecting line 23 leads from the transfer chamber 23 to a separator (not shown here). In contrast to the buffer vessel 19 on the cold side, the liquid-metal infeed line 1a terminates in the lower portion of the buffer chamber 20, whereas the liquid-metal discharge line 3 is connected to the upper portion of the buffer vesel chamber 20 below the rupture disc 21.

A branch line 3601 having a rupture disc 37a is fitted to infeed line 1a and leads to a separator (not shown here). This arrangement oifers the advantage that the pressures built up in the buffer vessel 19a are reduced very quickly following evacuation into the branch line 3611 through rupture disc 37a. It is advantageous that a nozzle 38 be installed in a short line 1]) between branch 36a and the buffer vessel 38, such nozzle effecting a low pressure loss in the operating fiow direction and a high pressure loss on the flow direction being reversed.

In accordance with a further modification as shown by FIGURE 6, a primary separator 33a is connected to the buffer vessel 19a on the hot side of the heat exchanger, such bufi'er vessel having the same effect as that shown in FIGURE 4. The primary separator is connected to a main separator (not shown here) by line 35 and features a drain line 26a for the collected liquidmetal. With this arrangement, the branch line 36a with installed rupture disc 37a and the special separator are not required.

On the cold side of the heat exchanger, a primary separator 33 is connected to buffer vessel 19, and to a separator 24 by a connecting pipe 35.

In the arrangement shown by FIGURE 7, two heat exchanger systems are joined in parallel in that their manifold 1d, 10, for liquid-metal infeed are connected to a common liquid-metal infeed line 1. Infeed manifold 1 has a rapid shut-off element 2. In addition, nozzles 38a, 38b are installed in the branching manifolds 1d, 1e. The nozzles effect a low pressure loss in the operating flow direction and a high pressure loss when the flow direction is reversed.

The manifolds 1a, 1e lead to the buffer vessel- s 19a, 19b, to which the lines 3a, 3b for liquid-metal feed to the heat exchanger units are connected.

Each of the two heat exchanger facilities are equipped with their own buffer vessels 19, 19d on the cold side, their discharge lines 30c, 30d terminating in a discharge manifold 30c. Both discharge lines 30c, 30d are connected to a common surge tank 32 by two separate lines 31c, 31d.

As will be evidenced from the foregoing description, certain aspects of the invention are not limited to the particular details of construction as illustrated, and it is contemplated that other modifications and applications will occur to those skilled in the art. It is, therefore, intended that the claims shall cover such modifications and applications that do not depart from the true spirit and scope of the invention.

We claim:

1. A heat exchanger system using the exchange media liquid-metal/water comprising one or more heat exchanger units of single or multi-part design, and a relief vessel to accept the high-pressure liquid metal, Water, and reaction products on pipes fracturing, in which the heat exchanger unit (8, 8a), are followed by a buffer vessel (19) through which the returning liquid-metal continuously flows, the chamber (20) of such buffer vessel being separated by a rupture disc (21) from a line (23) running between such vessel chamber and a separator (24) and in which the liquid-metal discharge line (27) from the buffer vessel (19) features a restrictor device (28) and is connected by a branch line (31) to a surge tank (32), the latter at all times containing a certain quantity of liquid-metal and having an inert gas cushion.

2. A heat exchanger system in accordance with claim 1, and in which the buffer vessel (19) is of cylindrical design and arranged standing vertically, the top end being closed by a rupture disc (21) covering the full crosssection of such vessel to separate the vessel chamber (20) from a transfer chamber (22) which takes the end of the feed line (23) leading to the separator (24), and in which the liquid-metal infeed line, (11) terminates in the upper portion of the buffer vessel chamber (20) below the rupture disc (21) and the liquid-metal discharge line (27 is connected to the lower portion of the buffer vessel chamber (20).

3. A heat exchanger system in accordance with claim 2, and in which the liquid-metal discharge line (30) from the buffer vessel (19) features a rapid shut-off element (29) between the orifice plate (28) and the branch (31) leading to the surge tank.

4. A heat exchanger system in accordance to claim 2, and in which the transfer chamber (22) of the buffer vessel (19) is considerably widened (to equal about twice the buffer vessel diameter) between the rupture disc (21) and the discharge line (23).

5. A heat exchanger system in accordance with claim 3, and in which the liquid-metal infeed line (11) is connected to the upper portion of the buffer vessel (19c).

6. A heat exchanger system in accordance with claim 2, and in which the liquid-metal infeed line (11) enters the lower portion of the buffer vessel (19c) and is led upwards inside the buffer vessel chamber (22) to terminate immediately below the rupture disc (21).

7. A heat exchanger system in accordance With claim 2, in which a primary separator (33) is connected to the transfer chamber (20), the gas discharge pipe (25, 35) of such primary separator leading to a following separator (24).

8. A heat exchanger system in accordance with claim 6, and in which a short horizontal line leads to the primary separator (33), entering such primary separator tangentially.

9. A heat exchanger system in accordance with claim 1, and in which the buiier vessel (19) is designed as a cylindrical vessel (19c) arranged to stand vertically, the top end of such vessel taking a line (34) having a diameter equal to the cross-section of the vessel and accommodating the rupture disc (21), such line (34) leading to th primary separator (33).

10. A heat exchanger system in accordance with claim 1 and in which the separator (24) features two lines (23b) and (23a) which enter the separator vessel tangentially, at opposite points in such a way as to point in the same direction of rotation, such lines (23b) and (23a) being the branches of infeed line (23), which forks shortly ahead of the separator to form these two branches.

11. A heat exchanger system in accordance with claim and in which the liquid-metal line (27) as an infeed line of the buffer vessel (19) takes a branch (36) immediately behind the orifice plate (28), such branch line leading to a separator and featuring a rupture disc (37).

12. A heat exchanger system in accordance with claim 11 and in which the infeed lines (7a) to individual heat exchanger units and/or the common infeed lines (4) to several heat exchanger units (8, 8a), are equipped with non-return valves (6) which automatically block such lines on the flow direction being reversed.

13. A heat exchanger system in accordance with claim 12, and in which the liquid-metal infeed manifolds (1, 1a, 1b, 3) to the heat exchangerv units (8, 8a), each having a continuous-flow buffer vessel (19a), the chamber (20) of which is separated by a rupture disc (21) from a line (23) leading to a separator and terminating in such chamber (20), and in which the chamber (20) is further isolated by a rupture disc (37a) located in a line (36a) branching from the manifold (1a) ahead of buffer vessel (19a) and leading to a further separator.

14. A heat exchanger system in accordance with claim 13, and in which the line (1a, b) feeding liquid-metal to a buffer vessel (19a) has a nozzle (38) which efiects a minor pressure loss in the operating flow direction and a high pressure loss on the direction of flow being reversed.

15. A heat exchanger system in accordance with claim 13, and in which the buffer vessel (19a) is designed as a cylindrical vessel (19c), and arranged standing vertically, the top end being closed by a rupture disc (21) cove-ring the full cross-section of such vessel to separate the vessel chamber (20) from a transfer chamber (22) which receives the end of a line (23) leading to a separator, and in which the liquid-metal infeed line (11)) terminates at the lower portion of buffer vessel chamber (200), and the liquid-metal discharge line (3) is connected to the upper portion of the buffer vessel chamber (19c) below the rupture disc (21).

16. A heat excanger system in accordance with claim 15, and in which the transfer chamber (22) between the rupture disc (21) and discharge line (23) is considerably widened, to equal about twice the buffer vessel diameter.

17-. A heat exchanger system in accordance with claim 13, and in which a primary separator (33a) is connected to the transfer chamber (22) of the buffer vessel (19a), the gas discharge pipe (35a) of such primary separator leading to a following separator.

18. A heat exchanger system in accordance with claim 17, and in which a short horizontal line leads from the transfer chamber (22) to the primary separator (33a), entering the latter tangentially at one side.

19. A heat exchanger system according to claim 13, and in which the buffer vessel (19a) is designed as a cylindrical vertical vessel (190) the upper portion taking a horizontal pipe (34) equal in cross-section to the diameter-of the vessel (19a), such pipe (34) accommodating the rupture disc (21) and leading to the primary separator (33a).

20. A heat exchanger system in accordance with claim 19, and in which the liquid-metal infeed line (1b) which terminates in the upper portion of the buffer vessel (19a) immediately below the rupture disc (21) is led downwards vertically inside the vessel (20), leaving such vessel at the bottom portion.

21. A heat exchanger system in accordance with claim 20, and in which two or more heat exchanger systems, together with their buffer vessels (19a, 19b) arranged ahead of the manifolds, are connected to a common liquidanetal infeed line (1), each branch line (1e, 1d) being equipped with a nozzle (38a, 38b) which effects a low pressure loss in the operating flow direction and a high pressure loss on the direction of flow being reversed.

22. A heat exchanger system in accordance with claim 21, and in which each of the liquid-metal discharge lines (9a, 10a) of each indiivdual or several heat exchanger facilities (8, 8a) feature a hydrogen bubble detector (40).

23. A heat exchanger system in accordance with claim 7, and in which the vaporous or gaseous media discharging or conveying lines and feature apertures (39, 35a) in their walls.

References Cited UNITED STATES PATENTS ROBERT A. OLEARY, Primary Examiner.

A. W. DAVIS, Assistant Examiner.

US. Cl. X.R.

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