DE2159196A1 - Reactivity control in water cooled reactors - using fluid neutron absorber - Google Patents

Abstract

A control system applicable to water cooled reactors in which an immiscible neutron absorbing fluid e.g., boric acid is used in varying concentration to effect reactivity changes. The fluid is supplied from an external tank to zircon containments in empty fuel or control channels within the core and the differential pressure between fluid supply and reactor coolant manipulated to vary the extent of coolant displacement by the fluid and the core reactivity. The zircon containments are basically similar for fuel and control channels comprising a closed outer tube and concentric inner tube with an open bottom end. Fluid supply is to the inner tube and coolant displacement is effected through a discharge orifice at the top of the annulus formed by the inner and outer tubes. Radial and axial trimming and quicker power raising are facilitated.

Description

Process for the reactivity control of nuclear reactors with device for carrying out the method The invention relates to a method for Reactivity control of nuclear reactors and a device for carrying out the Process in which a more or less neutron absorbing Liquid from an external source into the one filled with water as a coolant Reactor is passed.

When regulating the power of a nuclear reactor, in a known manner Control rods and flowing fluids used. Both are used for targeted absorption of neutrons.

It has already been proposed for regulating the reactivity of nuclear reactors a neutron absorbing liquid such as boric acid a pipe system that is separated from the reactor coolant and penetrates the reactor core to direct. The regulation takes place in such a way that neutron-absorbing liquid higher or lower concentration is passed through the pipe system.

The known type of regulation requires a separate pipe system, that is complex and expensive.

Since both supply and return lines must be laid here are only small pipe diameters possible. This limits the response time of the system.

The double lines must lead out of the reactor separately will. They must also be tight both to the outside and to one another. When losing weight the pressure vessel hood, both lines must be interrupted and then tight again get connected.

The pressure difference between the control fluid and the coolant forces the pipe wall to be very thick with high neutron absorption. By the required Due to the number of pipes and their sealants, the system is susceptible to malfunctions. In addition, there may be

Delays in refueling.

The object of the invention is therefore to create a method for the reactivity control of nuclear reactors, in which on the reactor separately penetrating pipe system can be dispensed with.

The device required to carry out the procedure should be designed to be simple and easy to install, as well as largely trouble-free be.

In the case of a method, the task set is the one mentioned at the beginning Genus solved in that the neutron-absorbing liquid passed into containers and when the load changes from the containers by replenishing water or neutron absorbing materials Liquid of other concentration in the coolant or due to coolant counter pressure ~ outside is pushed to outside the reactor.

The proposed method is the neutron absorbing Liquid in open communication with the Reactor coolant. this is particularly advantageous because the reactors mentioned at the beginning Kind of devices for withdrawing the neutron-absorbing liquid anyway the reactor coolant are present. In the event of a shutdown, the salary increases neutron-absorbing liquid in the coolant only a little, since the volume of the. Control medium is very low compared to the volume of the coolant. After a shutdown the reactor can therefore quickly be run up to full load again.

The regulation according to the invention can also be used for rapid shutdown can be used for radial and axial power trimming of the nuclear reactor. Specific Control rods, for example gray and part-length, can be omitted.

An apparatus for performing the method is that the containers are arranged in empty control rod guide tubes and each is made of a container shell with a base and an opening at the top and a coaxially arranged therein, form an annular space together with the container jacket Inner tube exist, which is open at the foot and for connecting at the head.

bond formed for a supply line leading to the source is.

As a further development of the above-mentioned device is provided that each container is between one at the bottom of the associated control rod guide tube supported spring or a tubular bellows or the like. And one as a connection of the inner tube extends with the supply line serving throttle body. It is useful that the throttle body and an extension of the inner tube can be moved relative to one another and are designed for releasable connection and that the connecting means consists of a between a spiral thickening of the tanning and the Container head displaceable, in the position resting on the container head, by a bayonet device o. The like. Lockable sleeve and one arranged in the throttle body for gripping of the free shell of the extension formed detent spring exist7 which at Establishing the connection from the end thickening of the extension tube and at Loosen the connection from the sleeve, to slide over the end thickening, spreadable is.

However, the containers can also be in positions provided for fuel assemblies occupy and have the size of fuel assemblies as well as with channels for passage be provided with coolant.

Finally, it can be useful to have both containers in the reactor empty control rod guide tubes, as well as in intended for fuel assemblies, however, to arrange fuel element-free positions.

Because between the reactor coolant and the neutron absorbing If there is constant pressure equalization in the liquid, the supply line and container walls can are made relatively thin. As a result, there is also little neutron absorption a.

Leaks in the system are largely insignificant.

Expensive sealants can therefore be dispensed with.

When using detachable connections between the containers and their feed lines, the containers can be used when the fuel element is changed in the reactor remain as they do not hinder the removal and insertion of fuel assemblies.

The device is functionally reliable to a high degree, even when it is heavy Accidents in which the core IDia structures are displaced because they are not rigid links between the containers and their supply lines to allow relatively large shifts.

In the drawing, exemplary embodiments of the invention are shown, on the basis of which the method and the devices for carrying out the method explained.

They show: FIG. 1: a longitudinal section through a nuclear reactor. 2: a cross section through a fuel assembly with fuel rods and control rod guide tubes Fig. 3: a longitudinal section through a container Fig. 4: a longitudinal section through a container arranged in an empty control rod guide tube Fig. 5: a longitudinal section through a relative to a throttle body axially displaceable trained container Fig. 6: a perspective view of a container, which can be arranged in the reactor instead of a fuel assembly.

The inventive regulation takes place in such a way that the example Boric acid neutron absorbing liquid, the one for the desired Absorption has a set concentration of one outside the nuclear reactor 2 located source 1 through a feed line in container 3, 4 from, for example Zircon material is pressed. The containers 3, 4 can be placed in empty control rod guide tubes 4a and / or be arranged at positions 3a provided for fuel rods. At a Load change is either water or boric acid of higher or lower concentration nachgeschoben, where - with the liquid located in the containers into the fuel elements surrounding coolant crowded and, there is heavily diluted.

To change the concentration of boric acid in the containers 3.4 can also be followed the opposite way, that coolant under appropriate Pressure is set under which the liquid in the containers 3, 4 is directed against its inflow path outside the reactor.

The liquid flowing into the container 3, 4, enteric boric acid or water on one side, or detergent on the other side, should the in Displace the containers 3, 4 standing liquid column as possible without mixing. It must also be avoided that the container evenly from one end to the fill others, as this creates an unbalanced axial load in the fuel elements in the vicinity would result. The containers therefore have the following training: They consist of a container jacket 6 with a bottom 6a and an opening 7 on the top side in the container jacket 6, an inner tube 8 is arranged coaxially, which with the container jacket 6 forms an annular space 9-forms. The inner tube 8 is open at the foot and has a connection piece at the head lo for a supply line leading to the source 1 (not shown).

The control fluid, boric acid or water, flows during a control action from the source 1 through the supply line and the connecting piece 10 into the inner tube 8 and displaces the liquid located there into the annular space 9 and then through the opening 7 into the coolant. To avoid a large number of supply lines several pipe containers can be connected to a common supply line.

The regulation is also possible so that coolant through the opening 7 pressed into the container and the one located there Column of liquid is pushed through the ufleitungsleitung outside of the reactor. There she can be broken down into ihoe constituents water and boric acid.

The formation of the container results in a mixing of the therein located liquid column with the after flowing liquid or the inflowing Coolant largely avoided and-also a uniform filling of the ends (Fig. 3).

The arrangement of containers in empty tax discharge pipes 4a is made so that the also consists of a container shell 6 and a concentrically arranged therein inner tube 8 existing container 4 between a on the bottom of the control discharge pipe 4a supported spring ii or a tubular bellows o. Like. And a throttle body 12 extends (Fig. 4) The container 4 can when changing of the fuel assemblies by a device attached to a gripper of the fuel assembly loading machine is arranged to be removed, with which individual container 4 or all to one Fuel element belonging container 4 pulled out and possibly used elsewhere can be.

Pulling up the fuel assembly loading machine for removal w d insertion the container 4 can then be omitted if the throttle body 12 and an extension 13 of the inner tube 8 is designed to be displaceable relative to one another and to be releasably connected are. In this case, the container 4 when changing the fuel assembly with the upper Core framework 2a pulled out of the core. The connecting means required for this consist of one between an end thickening 14 of the extension 13 and the Head: of the container 4 displaceable, in the one resting on the container head Position by a Bayonettv 0 rri ohtung 15 or the like. Lockable sleeve 16 and from one arranged in the throttle body 12 to encompass the free Coat the extension 13 formed detent spring 17.

When the connection is made, the detent spring 17 is removed from the end thickening 14 spread and then engages around the free jacket of the extension 13. The release the connection takes place in such a way that first the sleeve 16 is rotated, wherein a pin 15a arranged on the extension 13 out of engagement with the sleeve 16 comes, which is then pushed against the end thickening 14 and here the Detent spring 17 spreads so far that it when lifting the throttle body over the end thickening 14 can slide.

To carry out the process, it is also possible to keep empty containers Control rod guide tubes 4a and / or to be arranged in positions that are for fuel assemblies are provided.

In Fig. 5, a container 3 is shown, which the size of a Has fuel assembly and arranged at intended position for fuel assemblies can be (Fig. 1). The container 3 is box-shaped and has channels for passage from KUhlxittel (not shown).

The arrangement of such containers in positions of fuel assemblies is useful if z. B. too few fuel elements available due to fuel element damage are.

The supply lines for the containers can be in support pillars passed through the upper core frame 2a and on its flow-free upper side too few pipes protruding through the hood of the pressure vessel are pulled together.

The containers can also be provided with separate feed lines instead of divisions rods can be provided in different axial positions. By this arrangement results in a saving of control rod drives.

Groups of containers can act as gray control rods take over, which also saves drives.

Groups of part-length tubular vessels are used for axial power trimming and normal-length tubular vessels are suitable for radial power trimming.

6 claims 1 figure

Claims (6)

Patent claims 0 method for at least partial reactivity control of nuclear reactors, in which a change in concentration more or less neutron absorbing liquid from an external source into the water is passed as a coolant-filled reactor, characterized in that the Neutron-absorbing liquid is fed into the container (3, 4) and when the load changes from the containers (3, 4) by replenishing water or neutron absorbing Liquid of other concentration in the coolant, or through coolant back pressure is pushed outside the reactor (2). 2. Apparatus for performing the method according to claim 1, characterized characterized 'that the container (4) in empty control rod guide tubes (4a) are arranged and each consist of a container jacket (6) with a base (6a) and a head-side opening (7) and a coaxially arranged therein, together with the container shell (6a) an annular space (9) forming the inner tube (8) exist, which Open at the foot and at the head for connection to a supply line leading to the source (1) is trained. 3. Apparatus according to claim 2, characterized in that each Container (4) between one at the bottom of the associated control rod guide tube (4a) supported spring (-11) or a tubular bellows or the like. And one as a connection of the inner tube (8) with the supply line serving throttle body (12) extends. 4. Apparatus according to claim 2 and 3, characterized in that der'Drosselkörper (12) and an extension '(13) of the inner tube (8) against each other are designed to be displaceable and releasable and the connecting means the end one between an end thickening (14) of the extension (13) and the container head displaceable, in the position resting on the container head, by a bayonet device or the like lockable sleeve (16) and one arranged in the throttle body (12), locking spring (17) designed to encompass the free jacket of the extension (13) exist, which when making the connection from the end thickening (14) of the extension tube (13) and when loosening the connection from the sleeve, (16) for passing over the end thickening, is spreadable. 5. Apparatus for performing the method according to claim 1, characterized characterized in that the containers (3) for fuel elements provided positions (3a) occupy and have the size of fuel rods and with channels for passage are provided with coolant. 6. Device for carrying out the method according to claims 1 to 5, characterized in that in the reactor both containers (4) in empty control rod guide tubes, (4a) and container (3) in intended for fuel assemblies, but without fuel rods Positions (3a) are arranged.