DE2316066A1 - NUCLEAR REACTOR, ESPECIALLY. PRESSURE WATER REACTOR - Google Patents

Description

Nuclear reactor, especially pressurized water reactor

The invention relates to a nuclear reactor with a reactor pressure vessel, which contains a reactor core and has at least two lines with main coolant pumps that lead to a steam generator, as well as a system for introducing emergency cooling water in the event that one of the lines breaks.

From the magazine "Atomwirtschaft", Nov. 1971, page 462, a pressurized water reactor is known in which coolant from so-called flood tanks for emergency cooling of the reactor core or from the sump of the reactor building into the normal main coolant lines, So in the "hot" and "cold" branch of the primary cooling circuit is pressed, so that the coolant floods the reactor core. In the event of a break in the cold strand, i.e. the strand from the steam generator to the reactor pressure vessel and which usually contains the main coolant pump, can, however, after the emptying phase Form a vapor cushion in the reactor core, which prevents the emergency coolant from penetrating into the Reactor core prevented. The vapor cushion results in such a high pressure that it is fed into the primary cooling circuit Emergency coolant sometimes escapes directly from the leak caused by a break in one of the coolant lines.

It has also been proposed to spray emergency coolant directly into the reactor core, where it is applied directly to the Fuel rods rebound from the fuel assemblies that form the reactor core. This also solves the aforementioned problem of

4098 4 1/0558

- 2 -

- .. 2 - VPA 73/9414

Do not solve the development of steam satisfactorily, because the immediate Spraying into the core can lead to additional steam formation, which results in a particularly high pressure. This makes refilling the core even more difficult.

In contrast, the invention has set itself the goal of emergency cooling to improve without much effort. In particular, the development of steam in the event of a break in the so-called cold Strings, i.e. the lines that lead from the steam generator (s) to the reactor pressure vessel and contain the main coolant pumps, are taken into account.

Based on the nuclear reactor mentioned at the outset, it is provided according to the invention that at least one further emergency cooling line in a space above the reactor core within the reactor pressure vessel or in the line between Reactor pressure vessel and steam generator or leads into the steam generator itself and that the escaping from this emergency cooling line Emergency coolant predominantly towards the edge of the reactor core and / or bypassing the reactor core to the point of break the line drains.

With the emergency cooling line according to the invention, at least one Part of the emergency coolant out in such a way that it contributes practically nothing to a new vapor formation. In the Greg part it does Emergency coolant condensation of the vapor, as it is opposite to the boiling temperature in the emptied reactor is cold, e.g. only at room temperature. Through the steam condensation it is also achieved that the core can be filled from below via other emergency cooling lines, because the pressure in the area of the core in relation to the height difference of the main coolant line above the upper edge of the core is so small that only small amounts of the emergency coolant flow through the leak will escape.

In the case of a nuclear reactor with a collecting space in the steam generator, from which the main coolant is returned to the reactor pressure vessel.

409 841/0558 - 3 -

- 3 - VPA 73/9414

flows, you can provide a spray device in this collecting space, which is connected to the emergency cooling line. the The spray device then produces a strong vapor condensation outside the reactor pressure vessel, with the emergency coolant after steam condensation bypassing the reactor core because it exits directly through the broken pipe. This gives a rapid reduction in pressure, which via the unbroken line, in particular via the hot strand, very quickly also in the reactor pressure vessel itself affects.

Another embodiment of the invention, which can also be used together with the aforementioned possibility, has a spray device above the reactor core, from which the emergency coolant is sprayed against the core container, which includes the reactor core. By spraying, in turn, vapor condensation is achieved. On the other hand, the sprayed flows Emergency coolant not in the center of the reactor core, which would undesirably form new steam, but it runs on the core container wall and in the edge zone of the Reactor core down, where the temperatures are lower than in the middle of the reactor core.

The spray device can be a channel on its underside having directed towards the core container spray openings. The spray device can, however, also have vertically extending spray pipes with lateral spray pipes directed towards the core container Include openings. You can also use the core structure and / or the lid of the reactor pressure vessel, i.e. with parts that are required during normal operation of the Reactor, e.g. when changing fuel assemblies, can be removed. It is thus achieved that the new emergency cooling device does not interfere with normal operation.

In a further embodiment of the invention lead fluidically Additional feed pipes running parallel to the spray device into the reactor core. These pipes

409841/0558 - 4 -

- 4 - VPA 73/9414

enable, as in the case of the earlier proposal mentioned, an immediate Cooling of the reactor core with supercooled water already during the emptying phase. According to the further invention, they are only used in conjunction with the aforementioned condensation measures used to allow replenishment of the reactor core can take place despite an additional development of steam. The feed pipes are preferably in several groups distributed over the cross section of the reactor core. It is recommended that the groups not be one-sided to assign certain small sections of the reactor core, but to overlap so that even if one Group the whole core is still largely sprayed evenly. The feed pipes are also in the middle of the reactor core arranged while the spray tubes on the edge of the reactor core lie.

The feed pipes can be connected to the same emergency cooling line which also feeds the above-mentioned spray devices. But you can also have your own feed In particular, the safety feed pump customary in reactor systems can only be installed in the feed pipes and, if necessary, can still be promoted into a few spray tubes directly connected to them. You save on this Way the previously usual complex selection circuit, which is to ensure that the available emergency coolant is not useless from the leak in the broken main coolant line flows off. This is particularly favorable when the safety feed pump promotes concentrated boric acid solution into the feed pipes, because this is then carried over the core cross-section Security is distributed so that the reactivity is strong is reduced.

An emergency cooling line can also pass through the cover of the reactor pressure vessel to lead. For example, it can feed a spray device that is attached to the lid itself and thus together with this can be removed without the structure of the reactor core has to be changed somehow - You should have a check valve inside the lid, at least close to it.

■ 409841/0558 - 5 -

- 5 - «PA 73/9414

see that in normal operation the emergency cooling line of the cover keeps pressure-free. We also recommend a siphon above the Cover, which prevents the heating of connecting flanges etc. by a coolant flow caused by natural convection out of the cover upwards.

Within the reactor pressure vessel, plug-in connections are expediently used in the course of the emergency cooling lines to the To make removal and installation as simple as possible during normal operation, especially when changing fuel assemblies. as Such a plug connection can also be used with hollow throttle bodies, via which the feed pipes in the core are connected to the emergency cooling line be connected. The throttle bodies are normally only used to counteract those provided in each fuel assembly Guide tubes for control rods in fuel assemblies in which no control rods are used or to close less tightly in order to prevent a useless coolant flow in the bypass, i.e. with little heating prevent. If these throttle bodies are made hollow according to the invention, the emergency coolant can be fed into the feed pipes via them are distributed, from which it then exits into the reactor core. You can then get by without additional parts.

Due to the reduction in vapor pressure brought about by the invention in the event of a break in the cold main coolant lines only a relatively low pressure is required for emergency cooling. It can therefore be enough if the emergency cooling lines are connected to an elevated tank arranged above the reactor pressure vessel. If the liquid level is sufficient, the elevated tank can ensure that the emergency coolant is used without additional pumps reaches the reactor core at a pressure greater than the vapor pressure. Appropriate heights above the reactor pressure vessel from about 5 to 30 m can be achieved in conventional nuclear power plants inside the safety envelope without great structural effort.

For a more detailed explanation of the invention are in the following

409841/0558

- 6 - VPA 73/9414

Embodiments described with reference to the drawing in Fig. 1 of :. Line diagram of a pressurized water reactor and in the Fig. ' 2 to 5 shows details in vertical sections at different scales.

In Fig. 1 is a schematic representation of the reactor pressure vessel 1 of a pressurized water power reactor of 1200 MWE> drawn, which is closed with a pressure vessel cover 2. The flange connection 3 of the lid also serves to Fastening a core container ″ 4 in which the reactor core 5 is fixed with the aid of the so-called core structure 6. The The core structure 6 can be removed, for example, to change the fuel element. .

The primary cooling circuit 8 is connected to the reactor pressure vessel 1. It comprises the 4 coming from the interior of the core barrel hot leg 9 of the main coolant lines with a steam generator 10, the primary inlet chamber designated 11 and its Primärauslaßkammer mi 12 is _t. Two parallel “cold” branches 14, 14 ′ of the primary cooling circuit lead back from the steam generator 10 to the reactor pressure vessel 1. A main coolant pump 15, 15 'is located in each line.

For emergency cooling of the core container 4 in the event of an accident in which a leak occurs in the primary cooling circuit 8, an emergency and After-cooling pump 17 is provided. It sucks what is coming out of the leak Coolant via a non-return flap 18 from a sump 19 at the bottom of a metallic safety envelope 20 which includes all essential parts of the pressurized water reactor.

The pump 17 delivers via an intercooler 22 and a Check valve 23 in an emergency cooling line 24, which via a further non-return valve 26 and an emergency cooling line 46b in the hot strand 9 of the coolant circuit leads. Below the hot strand 9 »that extends into the reactor vessel 4 is guided, there is a channel 27, which will be described in more detail later. The channel 27 has outlets from which use supercooled feed water as an emergency coolant (temperature

409841/055 8 -7-

- 7 - VPA 73/9414

door approx. 20 ⁰ C) can be sprayed into the edge zones in the vicinity of the core container inside the reactor pressure vessel 1. There vapor spaces are formed in the upper part of the reactor pressure vessel because, in the event of a leak in one of the cold strands 14, 14 ', the cooling water which normally completely fills the pressure vessel escapes, but the steam resulting from the pressure relief does not find a direct outlet.

If parts of the primary cooling circuit 8 break, the emergency cooling line 24 is initially fed by a pressure accumulator 30. This is a container which has a gas cushion 31 in its upper part, which exerts a certain pressure on the coolant 32 in the lower area. The pressure accumulator 30 feeds into the cold branch 14 of the primary cooling circuit 8 via a non-return valve 34, namely in the so-called pump arc between the steam generator 1 * 0 and pump 15. In parallel, the coolant passes via a non-return valve 34 ¹ into the cold branch 14 ″ the pump 15 ′ and the reactor pressure vessel 1. The contents of the pressure accumulator 30 flows from the emergency cooling line 24 via the non-return valve 26 and the hot pipe 9 into the channel 27.

To the line 36 leading to the pressure accumulator 30 is via a further non-return valve 37 connected to an elevated tank 40. This container therefore also feeds the emergency cooling system as soon as the back pressure has dropped sufficiently. ' It is combined with the structural features inside the safety envelope 20, as indicated e.g. in the patent application P 22 17 398.4 = VPA 72/9424. A thickened downpipe can be attached to the elevated tank 40 42, which contains concentrated aqueous boric acid solution with, for example, 4 $ boric acid, with it the reactivity of the reactor core 5 is reduced, which otherwise, for example, as a result of the negative temperature coefficient of the Reactor core would rise if the reactor temperature was at a break in the main steam lines that are fed by the steam generator decreases.

- 8 409841/0558

- 8 - VPA 73/9414

On the thickened downpipes 42 can, if necessary, another Safety feed pump 44 must be connected. This promotes parallel to the non-return valve 37 and that via a non-return valve 45 only in an emergency cooling line 46a. Line 46a is via two detachable paddling connections 47 and 48 with one Connection piece 49 connected, which leads through the cover 2 of the pressure vessel 1. Inside the pressure vessel 1 opens the Connection piece 49 via a non-return flap 50 in a plug connection 51 which can be opened and closed in the vertical direction. From this go spray tubes 55 out. These are vertically extending tubes with lateral, directed towards the core container 4 Spray openings 55a. With respect to the cross section of the reactor core 5, the spray tubes are located on the edge thereof.

The plug connection 51 also feeds so-called feed pipes 52, which lead directly into the reactor core 5. Even though In the figure, for the sake of clarity, only one feed pipe 52 is drawn, there are a large number of pipes 52 in several parallel groups across the cross section of the reactor core 5 distributed, that is, also arranged in its center. The feed pipes 52 thus additionally enable a direct cooling of the entire reactor core in the event that the steam condensed according to the invention no longer interferes. the Feed pipes also offer the possibility of supplying boric acid concentrate to the reactor core 5 in a targeted manner.

The pressure accumulator 30 is also connected to the line 46a via a non-return valve 54 connected, so that the spray pipes 55 and the feed pipes 52 can also be fed from the elevated tank 40 or the folded pipe 42. But it is also possible the spray tubes 55, which are located above the core 5 at the core ' Structure 6 are attached and spray there in the direction of the core container 4, from the feed pipes 52 completely separate and feed, for example, through its own nozzle on the reactor pressure vessel 1 or its cover 2.

In the embodiment according to FIG. 1, the emergency cooling pump promotes 17 not only into line 24, but via another

409841/0558 ' . - ■

- 9 - VPA 73/9414

Check valve 56 and an emergency cooling line 46c also in the Outlet chamber 12 of the steam generator 10. There are spray nozzles 57 provided for reducing the pressure in the primary circuit 8, which is also noticeable in the reactor pressure vessel 1 via the lines 9 and 14. That about steam condensation emergency cooling water used flows directly to the leak in the primary circuit 8, so that no new steam is formed will.

In the embodiment of FIG. 1, there is a fuel assembly storage pool 60 shown, which is filled with coolant. This coolant can be via a line 61 with a non-return valve 62 are circulated with the aid of the pump 17 via the recooler 22 and a line 64, which via a valve 65 leads back into the fuel assembly storage pool 60. Therefore, the fuel element storage pool can with the help of the dry cooler 20: The same arrangement also enables the fuel in the fuel assembly storage pool 60 to be fed in existing cooling water in the emergency cooling line 24 and in the other lines connected to the branch 66 ..

The line 64 is connected via a valve 67 to a spray device 68, which is located in the upper region of the reactor building is arranged. The spray device 68 can condense steam that develops in the reactor building when hot cooling water from the reactor pressure vessel 1 or the primary circuit 8 into the reactor building, i.e. into the interior of the Safety envelope 20 occurs.

In Fig. 2 are structural details in a longitudinal section of the reactor pressure vessel 1 and the attached To see emergency cooling facilities. One recognizes in particular, that at the top of the core container 4, the open-top channel 27 is supported, at least for the most part around the The circumference of the core container 4 extends so that the through the

Connection 71 of the hot coolant line 9 emergency cooling water flowing in into the vapor space above the core 5

'• 409841/0558

- 10 -

- 10 - VPA 73/9414

can be sprayed. With the aid of spray nozzles 72, which are directed towards the core container 4 on the underside of the channel 27 are, and of suitable, not shown slots on the upper edge of the channel 27, which are to be similar, from each other lead separate fine jets, the emergency cooling water, directed against the core container 4 so that an intensive vapor binding takes place without much in the core itself new steam is formed. . '

The emergency cooling water is directed inside the reactor pressure vessel in such a way that it is heated by the steam on the inside of the core container 4 runs downwards without to meet the hot reactor core 5 in its .Zentrum. The core container 4 acts as a drain line that carries the emergency cooling water discharges along the edge of the reactor core.

The design of the line 46a with the two flange connections 47 and 48 is shown in Pig. 2 can also be seen in more detail, and although the line 46a is pivotably supported in the area between the flanges 47, 48 on the lower part of the flange connection 47, so that the cover 2 with the connecting piece 49 is free after the upper part of the flange connection 48 has been pivoted away can be withdrawn.

It can also be seen in FIG. 2 that the check valve 50 is supported within the pressure vessel cover 2. That Valve 50 is shown in Fig. 3 in a section. A hollow steel ball 75 is used as the closure body, which is pressed against the seat 76 of the valve housing divided at 77. Support ribs 78 ensure a free passage for the ball 75 'which can fall under the action of gravity if there is no excess pressure in the reactor pressure vessel 1 is present.

In FIG. 2, the check valve 50 is followed by the vertically openable plug connection 51 at the bottom. It leads to one Ring line 80 at the upper edge of the core structure 6, from which

4 0 9 8 4 1/0558

- 11 - VPA 73/9414

from individual fuel elements in the reactor core with the help of the feed pipes 52 can be acted upon. The feed line to the feed pipes 52 takes place via spray pipes 55, as their Extension of the feed pipes are to be seen in this embodiment. The junction between spray tubes 55 and feed pipes 52 are shown in detail in FIG. An elbow leads from the spray line 55 79 to hollow centering pins 81 of individual fuel assemblies. From there the emergency coolant is drawn through hollow plugs and channels in the head 83 of the fuel assembly to the feed tubes 52 forwarded, which are formed by unused control rod guide tubes.

On the right-hand side of FIG. 2, it is shown above that the distribution line 80 'can also be fed via a plug connection 51' which leads directly to the connector 49 '. The check valve 50 'is then seated outside the cover 2. It forms ^{a siphon with the line 46a 1} , which prevents the transport of heat through the hot coolant rising upwards.

In Fig. 5 it is drawn in a detail that the emergency cooling line 46a also directly into the reactor pressure vessel can lead. Inside the reactor pressure vessel 1, the emergency coolant is in turn releasable in a vertical direction Plug connection 85 forwarded so that the connecting line 86 together with the fuel element change upper plate 87 of the core structure 6 can be removed. The line 86 can be closed via a line 80 as in FIG Spray pipes 55, feed pipes 52 or lead to a spray device similar to the channel 27.

There is a further possible embodiment of the invention in that several, mutually redundant emergency cooling systems are connected to the respectively assigned emergency cooling lines (46a, 46b, 46c) are connected. . * ■

18 claims
5 figures

409841/0 558

Claims (1)

- 12 - VPA 73/9414 Claims 11. ) Nuclear reactor, in particular pressurized water reactor, with a reactor pressure vessel which contains a reactor core and has at least two lines with main coolant pumps which lead to a steam generator, and a system for introducing emergency cooling water in the event that one of the lines breaks, characterized in that 'At least one further emergency cooling line (46a, 46b, 46c) in a space above the reactor core (5) within the reactor pressure vessel (1) or in the line (9, 14) between the reactor pressure vessel (1) and the steam generator (10) or in the Steam generator (10) leads itself and that the emergency coolant emerging from this emergency cooling line predominantly flows to the edge of the reactor core (5) and / or bypassing the reactor core (5) to the break point of the line. 2. Nuclear reactor according to claim 1 with a collecting space in the steam generator, from which the main coolant to the reactor pressure vessel flows back, characterized in that a spray device (57) is provided in the collecting space (12), which is connected to the emergency cooling line. 3 · Nuclear reactor according to claim 1 or 2 with one of the reactor core comprehensive core container, characterized in that the emergency coolant from one with the emergency cooling line (46a) connected or from the emergency cooling line (46b) through the main coolant line (9) supplied spray device (27, 55) is sprayed against the core container (4) above the reactor core (5). 4 · Nuclear reactor according to claim 3 »characterized in that .that the spray device vertically extending spray pipes (55) with lateral, directed towards the core container (4) Includes spray openings. AO984 1/0558 -13- - 13 - VPA 73/9414 5. Nuclear reactor after. Claim 3> characterized in that that the spray device comprises a channel (27) which is directed on its underside against the core container (4) Has spray openings (72). 6. Nuclear reactor according to claim 3, 4 or 5> characterized in that that the spray device (27, 55) with the core structure (6) and / or the cover (2) of the reactor pressure vessel (1) is connected. 7 · Nuclear reactor according to one of claims 1 to 6, characterized characterized in that additional feed pipes (52) lead into the reactor core (5). 8. Nuclear reactor according to claim 4 and 7, characterized in that that the feed pipes are technically parallel to the spray pipes (55). 9 »Nuclear reactor according to claims 4 and 7, characterized in that that the feed pipes (52) are designed as an extension of the spray pipes (55). 10. Nuclear reactor according to claim 7, 8 or 9 »characterized in that that the feed pipes (52) are connected via hollow throttle bodies (82). 11. Nuclear reactor according to one of claims 7 to 10, characterized in that several groups of feed pipes (52) are distributed over the cross section of the reactor core (5). 12. Nuclear reactor according to one of claims 7 to 11 with a safety feed pump, characterized in that the safety feed pump (44) only delivers into the feed pipes (52) and the spray pipes (55). 841/0558 - 14 - ■ '- - H-- VPA 73/9414 13. Nuclear reactor according to claim 12, characterized in that that the safety feed pump (44) concentrated Boric acid solution in the feed pipes (52) promotes. 14 · Nuclear reactor according to one of Claims 1 to 13, characterized in that an emergency cooling line (46a) passes through the lid (2) of the reactor pressure vessel (.1) leads. 15 · Nuclear reactor according to claim H, characterized in that the emergency cooling line (46a) has a check valve (58) inside the cover (2). 16. Nuclear reactor according to claim 14 or 15, characterized through a siphon above the lid (2). 17 · Nuclear reactor according to one of claims 1 to 16, characterized by plug connections (51) in the course of the emergency cooling lines within the reactor pressure vessel (1), which can be released in the vertical direction. 18. Nuclear reactor according to one of claims 1 to 17, characterized in that the emergency cooling lines (46a, 46b, 46c) are connected to an elevated tank (40) arranged above the reactor pressure vessel (T). 409 841/0558 AS Blank page