DE19543827C1 - Light water reactor with coolant flow throttle system - Google Patents

Abstract

Light water reactor (1), esp. a boiling water reactor, has a pressure vessel (2), a reactor core (3), and a core mantle (4) with inlets (5) and outlets (6) for coolant, where the novelty is that, above the core (3), the core mantle (4) has a coolant outlet port (9) with a throttling device (10) which can be moved to increase or reduce the area for coolant flow, and which can be used to control the flow of coolant through the core (3). Also claimed are methods for regulating, and for rapidly reducing the power output of a light water reactor by use of the above throttling device.

Description

The invention relates to a light water reactor, in particular another a boiling water reactor, with a reactor pressure vessel ter, a reactor core and one enclose the reactor core the kernmantel, which kernmantel within the reactor pressure vessel is arranged and at least one inlet opening and has an outlet for core coolant, and a method for regulating the reactor output of a Light water reactor.

The circulation of core coolant, especially cooling water in a light water reactor, e.g. B. a boiling water reactor or a pressurized water reactor, he can in different ways consequences. In a natural circulation reactor, the coolant is on due to a density difference between that in the reactor core located coolant and that in an outside of the Reak coolant in the backflow chamber kept in a natural circulation. Is inside the reactor core the coolant is warmer than inside the backflow space and in a boiling water reactor due to vapor bubble formation much easier. With light water reactors with such a The above-mentioned forced circulation of the core coolant are circulation pumps provided that a flow through the Core and thus cause cooling of the same. By Control of the circulation pumps can be independent of the location of controls of the core cooling retracted into the reactor core medium throughput can be set. This independent one position of the core coolant throughput enables a favorable operating behavior of the light water reactor, in particular also in the control of abnormal operating conditions.  

DE-AS 18 04 371 is a sodium-cooled core described reactor, the arranged in respective cooling channels Has fuel elements for generating thermal energy. The Flow through the cooling channels with the coolant, the sodium, is regulated individually via the respective flow controller. These are in the form of panels. The regulation takes place so that all flow controllers are always at the same time and on che type are operated. This is supposed to last a long time Period burning of the fuel assemblies counter act to the power distribution in the reactor core to adapt to this burn. The throughput rain described only refers to the direct regulation of the Coolant throughput in the cooling channels of the fuel assemblies and has the fullest possible use of the thermi fuel energy by taking into account the changing over time physical, in particular thermal, properties of the fuel elements to the target. The The special coolant guidance with the same aim serves the same purpose a bimetal such as that described in U.S. Patent 4,588,549 or through attachments placed on the reactor core, as from German Auslegeschrift 1293929 and from EP 0389232 A2 are known. Furthermore, in DE 32 15 122 C1 a throttle plate arranged in the middle of the reactor core and in European patent EP 0125325 31 one the control rods enclosing throttle sleeve to limit the flow of the coolant described.

The object of the invention is a light water reactor special a boiling water reactor, specifying its core coolant throughput quickly, reversibly and with simple Means is changeable, so that a change, in particular a quick reduction that enables reactor performance becomes. At the same time, a procedure for regulating the Reactor output specified, which is independent of a  Regulation of the reactor power by retracting Control rods can be carried out in the reactor core.

According to the ge on a light water reactor task solved in that a light water reactor with a reactor pressure vessel, a reactor core and one the core shell surrounding the reactor core is provided, the core jacket within the reactor pressure vessel is arranged and at least one inlet opening and one Has outlet opening for core coolant, the outlet opening  assigned a flow cross-section and at least one Dros selector element geodetically provided above the reactor core is through which the flow cross section for controlling the Core coolant throughput is changeable.

By changing the flow cross section, by the heated cooling water flowing through the reactor core streams is a quick and reversible change in Reactor performance, in particular a reduction guaranteed. Especially in a boiling water reactor, in which by Auf heating the cooling water in the reactor core a steam water mixture is formed when the current is reduced mungsquerschnittes a heating of the cooling water in the Reactor core with additional steam formation, as a result a quick lei of the negative vapor bubble coefficient reduction in performance is achieved. Due to the changeable current a maximum possible outflow of the Steam-water mixture limits, which makes the light water craze cannot generate more energy in the medium and long term, than is bound in the outflowing steam-water mixture. Becomes In the short term, more steam is generated in the reactor core than through can flow out the flow cross-section, so there is an Er increase in the pressure in the steam-water mixture taken space. This causes the inflow of cooling water through the inlet opening into the reactor core changed or possibly even cooling water from the reactor core pressed out, so that the moderation of the Brenn emitted neutrons reduced and thus flat if the reactor power drops.

By changing the flow cross section can during almost normal operation of the light water reactor instantaneous change in power output can be achieved. The Adjustment of the reactor power is almost as quick like changing the flow area. Thus, the Reactor output independent of other control methods  the reactor power, such as the introduction of neutron absorption control rods in the reactor core or the change of Speed of appropriate coolant pumps can be regulated. The light water reactor thus has a diverse Power regulation, in particular through an instantaneous Use both for power control in normal operation as well as when an accident occurs.

The throttle element is preferably designed so that it can be operated in a passive manner and the flow cross-section, especially in the event of an accident, is reduced. This will increase the inherent security of the Light water reactor reached.

The variable flow cross section is preferably geodetically above of the reactor core. It has at least two partial crosses cuts, one of which partially or completely through the Throttle element is lockable. Here, each partial cross cut its own independently operable throttle element be assigned. Through two or more partial cross sections with a corresponding design of the throttle element or the throttle elements ensures that at least one as large ßer flow cross-section remains open that a sufficient cooling of the reactor core takes place. It can also by at least two partial cross sections a simple and fine adjustable power control of the light water reactor be performed.

The variable flow cross section is preferably in a jacket surface of one extending along a major axis Attachment of the core jacket and / or in the cross-sectional area of the essay. Such an arrangement of the flow cross-section tes is easy to manufacture by mechanically and under ther mechanical components, particularly stable components other hollow cylinders and pipes, accessible. In addition, here a simple redirection and distribution of the  Flow of the cooling water or the steam-water mixture be enough.

The throttle element is preferably one in the cylindrical Attachment of hollow cylinders movable along the main axis, through which the flow cross section at least in the lateral surface is at least partially lockable. A hollow cylindrical Dros selelement ensures a free flow of the cooling water or the steam-cooling water mixture along the main axis through the cross-sectional area of the attachment. So can even with a complete closure of the outer surface through this cross-sectional area a sufficient amount of Cooling water or steam-water mixture for cooling the reactor flow through the core. By shifting the Hohlzylin who can along the major axis in the cylindrical segment completely run over the outer surface of the attachment and for a flow can be blocked. This is a con continuous or discreet, with small increments, ver change in the jacket-side flow cross-section bar. It is thus done analogously to a shift of the new tron-absorbing control rods between the fuel elements, a quasi-continuous power control of light weight serreactor.

The throttle element can alternatively or additionally also as rotatable flap or run as a slider, what ins especially with rectangular channels for guiding the cooling water or the steam-water mixture is advantageous.

The throttle element is preferably passive in one of the streams close or completely close the cross-section Movable position. This can be done in particular through exploitation the gravitational force. The throttle element is here too preferred during normal operation in a Posi tion with high potential energy and is so out led that there was a movement to a position with lower  can carry potential energy. During normal It is operated by holding elements such as mechanical supports or at least one, preferably several, electro-magnets held in the position of high potential energy. When open in the event of an accident, these holding elements give the Dros Sel element for a movement into the lower pots position free energy in a passive way. At a Incident, which leads to a power failure to the choke element-holding electro-magnets lose them Magnets generate their magnetic forces and thus give the choke element free. It is also possible to use electric magnets like this interpret that they are theoretically possible in a large number Incidents, ensure release of the throttle element.

The light water reactor is preferably a natural circulation filter water reactor, especially large electrical power from 600 MW to 1300 MW, preferably 1000 MW. Such a The light water reactor thus has a power rain development by retracting control rods via a diversified Power regulation through regulation of the steam-water mixture, which emerges from the reactor core.

The on a process to regulate the reactor power a light water reactor, especially a boiling water reactor, directed task, is solved in that a light water reactor with a reactor pressure vessel, a reactor core and one enclosing the reactor core Kernmantel, which Kernmantel within the reactor pressure container is arranged and at least one inlet opening and has an exit opening through which the core coolant water flows into or out of the core jacket flows, a flow cross associated with the outlet opening cut over a throttle element is changed, whereby the Throughput of the core coolant and thus the reactor output is regulated.  

It is also a method for quick performance reduction a boiling water reactor, especially in the event of an accident, achieved in that when an accident occurs the throttle element the flow cross-section almost instantaneously downsized. As a result, the pressure of the steam water sches in the kernmantel increased, so that the inflow of cooling water hindered into the core jacket or even cooling water the core jacket is pushed out. The power generation can be greatly reduced in the short term and long term be limited to a low value, which at for example at 10% of the nominal power of the light water freak tors or possibly below. After a quick and great The flow cross-section is automatically reduced table a time-dependent setting of the core coolant rate and the pressure in the kernmantel to a new one because of stationary value. How fast these new stationary ones Values assumed depend on the size of the flow area geodetically above the reactor core, an ent Mixing steam and cooling water and that of the steam-what volume of space taken up by the mixture. A comparative wise small flow range affects the setting of the stationary value in a positive way, in particular a Swinging around the stationary value quickly dampened, which makes it Stability behavior is influenced favorably.

Based on the drawing, in one embodiment Light water reactor with variable discharge cross-section as well as the procedure for regulating the performance of light items serreactor, in particular a boiling water reactor closer described. It does not show to scale in schematic presentation

Fig. 1 shows a longitudinal section through a reactor pressure vessel of a boiling water reactor,

Fig. 2 shows a longitudinal section through the geodetically lowest area of a reactor pressure vessel of a boiling water reactor and

Figure 3 is a magnified image. Shown in FIG. 1.

Components required for the explanation of the light water reactor and the method according to the invention are shown here only. The meaning of identical reference characters in Fig. 1, Fig. 2 and Fig. 3 is the same in each case.

In Fig. 1, a reactor pressure vessel 2 of a boiling water reactor 1 is shown in a longitudinal section. The reactor pressure vessel 2 is stretched along a main axis 18 and completely encloses a reactor core 3 . The reactor core 3 is arranged in a core jacket 4, which is likewise stretched along the main axis 18 . Geodetically below the reactor core 3 , the core jacket 4 has inlet openings 5 for core coolant 7 , cooling water. Geodetically above the reactor core 3 , the core jacket 4 merges at an outlet opening 6 into a circular cylindrical chimney-shaped attachment 4 a, which has a steam-water mixture space 8 for the core 3 heated and partially evaporated in the reactor 7 bil det. The circular cylindrical attachment 4 a has a flow cross section 9 made up of two partial cross sections 9 a, 9 b, one partial cross section 9 b representing the cross sectional area 17 of the circular cylindrical attachment 4 a and the other partial cross section 9 a through part of the lateral surface 11 of the attachment 4 a is formed. Through the partial cross-sections 9 a, 9 b, the flow of the steam-water mixture is divided into a plurality of individual partial outlet openings 6 a, to each of which a steam separator (cyclone) 12 closes. Geodetically above the partial cross sections 9 a, a throttle element 10 , which is designed as a circular cylindrical hollow cylinder 21 , is arranged in the attachment 4 a. This hollow cylinder 21 is held by several, in particular three, arranged on the attachment 4 a electro-magnets 22 in an "open" positive that it does not block the partial cross-sections 9 a. When switching off the electric current flowing through the electric magnet 22 , the throttle element 10 falls due to the gravitational effect along the main axis 18 into the attachment 4 a and blocks the partial cross sections 9 a. As a result, the entire flow cross-section 9 is preferably reduced so that only a quantity of steam-water mixture can flow out through the still open part cross-section 9 b, which is required for reliable cooling of the reactor core 3 . As a result of the quasi-constant flow cross-section 9 , the proportion of vapor bubbles increases in the reactor core 3 , whereby the moderation of the nuclear chain reaction is significantly reduced. This results in a power reduction of the boiling water reactor to 10% or less of its nominal thermal capacity. By an appropriate arrangement or control of the electro-magnet 22 , it is also possible to move the throttle element 10 in predeterminable discrete steps along the main axis 18 , so that a quasi-continuous power regulation of the boiling water reactor can be carried out. It is also possible to move the throttle element 10 via corresponding unillustrated mechanical devices, such as cables, gears, or lifting rods in a predeterminable manner. Due to this well-defined displacement of the throttle element 10 , there is a change in the flow cross-section 9 for the partially evaporated cooling water 7 flowing out of the reactor core 3 . The cooling water 7 flows, as represented schematically by the flow arrows 14 , through the inlet openings 5 in the core jacket 3 . A control of the outflowing steam-water mixture via the throttle element 10 causes a quick, reversible and realizable with simple means control of the reactor power, which is used diversely for control by means of retractable in the reactor core not issued control rods. This also enables a diversified rapid shutdown of the light water reactor.

The chimney-like attachment 4 a of the core jacket 4 can have a diameter of about 2.5 m to 3 m and widens at its geodetically upper end, so that the steam-what can mix mainly radially radially outward. It gets there in a variety of steam separators 12 , in particular 300 to 350 in particular. The part of the steam-water mixture which continues to flow through the part of the attachment 4 a which runs along the main axis 18 passes through a substantially smaller number of steam separators, in particular approximately 20, from the core jacket 4 . The throttle element 10 which can be displaced along the main axis 18 and which is arranged geodetically above half of the partial cross sections 9 a has, for example, a diameter of 2.5 m and a length of 1 m. In a complete closure of the partial cross-sections 9 a through the throttle element 10 is a volume flow through the steam separator 20 still open, 12 each about 0.5 m / s for example, is achievable. This would correspond to a removable thermal output of around 550 MW. At full reactor power, for example, approx. 2800 MW thermal output is generated. Shutting off the partial cross sections 9 a by falling the throttle element 10 is achieved in less than 1 s. As a result, a reduction in the reactor output can be achieved in a significantly shorter time than by switching off a coolant circulating pump or by completely moving the control rods into the reactor core.

For continuous power control of the boiling water reactor 1 , the throttle element 10 formed as a hollow cylinder 21 can be designed such that, analogously to a control valve, with a displacement along the main axis 18, a linear relationship between the displacement and the steam throughput through the partial cross sections 9 a is achieved. For this purpose, the throttle element 10 can also have a reduction or increase in its diameter over its height, as a result of which additional forces directed along the main axis 18 as a result of pressure differences, eg. B. to increase the sealing force, can be generated.

According to FIG. 2, shafts 19 extending parallel to the main axis 18 are provided in the steam-water mixture space 8 , which is enclosed by the attachment 4 a. A part of the shafts 19 can be closed by a respective pivotable pivot 13 . The sum of the cross-sectional areas of the shafts 19 forms the entire flow cross-section 9, wel cher is divided into partial cross-sections 9 a and 9 b. Here, the partial cross-sections 9 a represent the cross-sectional areas of the shafts 19 , which can be closed by a respective flap 13 . The flap 13 is held in a position approximately parallel to the main axis 18 during normal operation of the boiling water reactor 1 , so that it leaves the partial cross section 9 b largely free. When an abnormal operating state occurs, the flap 13 is released from a holder (not shown), for example via a magnetic switch, and, as a result of the pressure exerted by the steam / water mixture, is brought into a section 9 a closing position. It can be held firmly in addition to the pressure on it by a locking device. By an almost instantaneous obstruction of partial cross-sections 9a, the whole of the steam-water mixture flow available to Strö flow cross-section is 9 b is reduced to the partial cross-section 9, so that only a part can suddenly flow out of the steam-water mixture. This results in an additional steam formation in the reactor core 3 , which is accompanied by a drastic reduction in the power of the boiling water reactor 1 . You dewasserreaktor 1 with a partially shut-off flow cross-section 9 thus has a particularly fast diverse Schnellab circuit in the event of an abnormal operating condition, which is passive.

Fig. 3 shows on an enlarged scale a section of the sentence 4 a in the region of the throttle element 10 with an electro magnet 22nd The electro-magnet 22 is arranged on the set 4 a and connected to a parallel to the main axis 18 push rod 24 which protrudes from the top 4 a. The push rod 24 is connected outside of the attachment 4 a with a drive 23 through which the push rod 24 and thus the electro-magnet 22 can be moved along the main axis 18 . The electro-magnet 22 exerts a holding force on a correspondingly designed plate 25 of the throttle element 10 through its electro-magnetic field. During normal operation of the electromagnet 22 , the throttle element 10 is thus held via the electromagnet 22 and the push rod 24 . When the push rod 24 is displaced, there is also a displacement of the throttle element 10 along the main axis 18 .

The invention is characterized by a light water reactor, in particular a boiling water reactor, the core jacket an outlet for outflow from the reactor core Has steam-water mixture, which has a variable flow mation cross section is assigned. The flow cross section is changeable by a passive throttle element, esp special quickly shrinkable, so that from the reactor core outflowing amount of the steam-water mixture is adjustable. This allows the steam content in the reactor core and above the steam bubble coefficient the reactor power quickly and set safely. The core jacket is preferred on the downstream side executed with a hollow cylindrical attachment, which has radial openings in its geodetically upper end. These radial openings are through one inside the up set of movable hollow cylinder lockable. Is the Hollow cylinder geodetically above the radial openings orders, he can due to the gravitational effect the radia open openings completely in less than a second lock. It thus remains for the steam-water mixture  an outflow only the free cross-sectional area of the Hollow cylinder. By quickly locking the radial Opening the amount of steam-water mixture flowing out be drastically reduced to a quasi instantaneous lei reducing the boiling water reactor to 10% or less its nominal power. The procedure, especially with a passive throttle element, is therefore suitable especially for a quick shutdown of a boiling water freak tors.

Claims (11)

1. Light water reactor ( 1 ), in particular boiling water reactor, with a reactor pressure vessel ( 2 ), a reactor core ( 3 ) and a core jacket ( 3 ) surrounding the core jacket ( 4 ), which core jacket ( 4 ) is arranged within the reactor pressure vessel ( 2 ) and Has at least one inlet opening ( 5 ) and one outlet opening ( 6 ) for core coolant ( 7 ), the outlet opening ( 6 ) being assigned a flow cross section ( 9 ) and at least one throttle element ( 10 ) being provided geodetically above the reactor core ( 3 ) , through which the flow cross-section ( 9 ) for regulating the core coolant medium throughput can be changed. 2. Light water reactor ( 1 ) according to claim 1, in which the variable flow cross-section ( 9 ) is geodetically above the reactor core ( 3 ) and has at least two partial cross-sections ( 9 a, 9 b), at least one of which is partially or entirely through the throttle element ( 10 ) can be locked. 3. light water reactor ( 1 ) according to claim 1 or 2, wherein the variable flow cross-section ( 9 ) in the lateral surface ( 11 ) along a main axis ( 18 ) directed cylindrical set ( 4 a) of the core jacket ( 4 ) and / or Cross-sectional area ( 17 ) of the attachment ( 4 a). 4. light water reactor ( 1 ) according to claim 3, wherein the Dros selelement ( 10 ) in the cylindrical attachment ( 4 a) along the main axis ( 18 ) displaceable hollow cylinder ( 21 ) through which the flow cross-section ( 9 ) in the lateral surface ( 11 ) is at least partially lockable. 5. Light water reactor ( 1 ) according to one of claims 1 to 3, in which the throttle element ( 10 ) is a rotatable flap ( 13 ) or a slide. 6. Light water reactor ( 1 ) according to one of the preceding claims, in which the throttle element ( 10 ) can be moved passively into a position reducing the flow cross-section ( 9 ) or completely closing position, in particular taking advantage of the gravitational effect. 7. Light water reactor ( 1 ) according to one of the preceding claims, in which the throttle element ( 10 ) is held by a magnet ( 22 ) during normal operation in a flow cross-section ( 9 ) opening position and in the event of a malfunction by switching off the magnet ( 22 ) assumes a flow cross-section ( 9 ) at least partially blocking position. 8. Light water reactor ( 1 ) according to one of the preceding claims, which is a natural circulation boiling water reactor. 9. A method for regulating the reactor output of a light water reactor ( 1 ), in particular a boiling water reactor, with a reactor pressure vessel ( 2 ), a reactor core ( 3 ) and a core jacket ( 4 ) enclosing the reactor core ( 3 ), which core jacket ( 4 ) within the Reaktordruckbehäl ters is disposed (2) and having at least one inlet opening (5) and an outlet opening (6) through which the core cooling water flows into the core shroud and flows out, wherein an exit opening (6) flow cross-section associated Strö (9) via a Throttle element ( 10 ) is changed, whereby the throughput of the core coolant ( 7 ) and thus the reactor power is regulated. 10. A method for fast power reduction of a boiling water reactor, aktorkern with a reactor pressure vessel (2), a Re (3) and a reactor core (3) surrounding the core jacket (4), which core jacket (4) is arranged within the reactor pressure vessel (2) and has at least one inlet opening ( 5 ) and one outlet opening ( 6 ) through which the core coolant flows into or out of the core jacket ( 4 ), the core coolant ( 7 ) being geodetically above the reactor core ( 3 ) through a flow cross section ( 9 ) flows, which is significantly reduced in the event of an accident by a throttle element ( 10 ) compared to the existing size during normal operation. 11. The method according to claim 10, in which the flow cross-section ( 9 ) through the throttle element ( 10 ) is reduced to a minimum size required to ensure the cooling of the reactor core ( 3 ).