DE1194991B - Safety device to avoid the ejection of fuel cartridges when emptying vertical channels of a nuclear reactor - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

G 21

German class: 21 g - 21/20

Number: 1194 991

File number: E 23723 VIII c / 21 g

Filing date: October 22, 1962

Opening day: June 16, 1965

The invention relates to a safety device to avoid the ejection of fuel cartridges when emptying vertically arranged Reactor channels in which a cooling gas flows under pressure.

It is well known that have heterogeneous power reactors, especially those with thermal neutrons work, a large number of vertical channels incorporated in the moderator, in which the fuel elements are stacked and in which a high pressure gas circulates which the dissipation of the heat generated by the cleavage reaction is guaranteed.

The upper and lower ends of these channels are through during normal operation of the reactor strong organs are closed, which are generally referred to as "locking pieces" and are intended for this purpose are to hold the entirety of the fuel elements of each channel in place without to prevent the passage of the cooling gas. In order to empty a reactor channel under these conditions to be able to carry out and replace the used fuel elements with new ones, it is especially necessary on the side of the reactor from which the fuel elements are removed are supposed to pull back the breechblock. It can now easily happen that the fuel elements under the influence of the pressure difference between the channel ends in an uncontrolled manner Be ejected from the canal and either suffer damage or damage in the process on the duct wall. Naturally, this damage is particularly great if it is in a partially emptied channel only a few fuel elements are located, their low weight the gas pressure cannot keep the equilibrium.

The object of the invention is therefore to move the channel to be emptied in the direction of its outlet to limit acting gas pressure to such a value during the emptying process that he is no longer able to conjure up any unintentional shifting even of individual fuel elements. A secondary requirement is that this pressure limitation should be automatic and without the use of movable and therefore subject to wear parts can be made.

According to the invention, this object is achieved in that each channel wall opens at its end opposite the supply side for the cooling gas. has openings of a certain size, which are in communication with a secondary channel through which to Safety device to prevent fuel cartridges from being ejected when emptying vertical channels of a nuclear reactor

Applicant:

Electricite de France (Service National), Paris

Representative:

Dipl.-Ing. R. Beetz and Dipl.-Ing. K. Lamprecht, Patent Attorneys, Munich 22, Steinsdorfstr. 10

Named as inventor:

Pierre Dequenes,

La Celle Saint Cloud, Seine-et-Oise (France)

Claimed priority:

France of November 15, 1961 (879 076) -

Reduction of the pressure drop along the fuel elements to the reactor channel from the main cooling circuit branched gas portion is supplied.

In the case of a reactor with vertical channels in which the removal of the fuel elements from the top and the main flow of the cooling gas from bottom to top through the channels is directed, the diverted cooling gas portion from the bottom of the reactor is the secondary channels fed through a horizontal gap, for example in the heat shield that the forms upper cover of the moderator stack of the reactor. This branched cooling gas portion is also Introduced into the interior of the channel only after the fuel elements that are in the upper part lying, are pulled out.

In a first embodiment, the gap is into which the portion of cooling gas diverted from the side walls of the reactor is introduced, assigned to all channels together.

According to a second embodiment, the channels are divided into adjacent groups, each group having a central channel in which, if necessary, a control rod slides; the branched-off cooling gas portion, which can be fed to each group, is in this case by a central channel for the control rod arranged, supplied in cross-section annular passage.

In this way, a safety device is obtained that controls emptying and loading of a channel when the reactor is in operation

509 580/233

Claims (1)

3 4 possible, with the ejection of fuel elements still present fuel element not from the th without any outside of the canal can be pushed out. In FIG. 2 Ordered organs are avoided. it is assumed that the channel 3 is completely with Further advantages and details of a safe fuel elements is filled, the one on top of the other heitsvorrichrung according to the invention result from 5 pelt are. At the top of the fuel element the following description of an execution stage, at the height of the passage of the channel for example. through the reflector, there is a note card 1 shows schematically a reactor with an ink 19; this cartridge 19 has the same shape and Safety device according to a first dimension like the fuel elements, contains each management example according to the invention; OK, not a fissile material. The top of the F i g. 2 shows on an enlarged scale the upper channel 3 is provided with a closure piece 18, Part of a reactor channel according to FIG. 1; the seal between the channel and the F i g. 3 shows a further embodiment of an outer surface of the closure piece, for example Safety device according to the invention. takes place by means of the sealing rings 20. In FIG. 1 is a schematic representation of an atomic reactor with 15. During normal reactor operation, the association shows an active core 1, which on the circumference with the end piece 18 covers the feed openings 12 for a cover or with a reflector 2. The main flow of the cooling gas runs around can be seen. The active core consists of a mode- the fuel elements in the channel 3 from below rator structure (for example made of graphite), in its upward and exits at the upper part after vertical channels the fuel elements flow under the closure piece.
are brought. Only a single one of these channels is shown when fuel elements are to be unloaded and denoted by the reference number 3. the closure piece is pulled out, whereby the inlet openings 12 above and below the active core are exposed. The two plates 4 and 5 are provided, which form a heat-branched cooling gas component that enters the channel and forms a shield for the moderator structure. The 35 and causes a reduced pressure drop along the reactor core is located inside a gas-tight fuel element in the channel 3. To the extent that the housing 6. The cooling gas, for example carbon, as the extraction takes place, the main acid grows, is under pressure into the interior of the housing 6 gas flow, which flows around the fuel elements and is introduced via a line 7 and tries to lift it upwards via a line, again more and more tion 8 after passing through the channels 3 in 30 until it reaches a throughput value reached, which is withdrawn again even in the direction indicated by the arrows 9 at the moment of removal of the last fuel. A membrane 10 running along the circumference of the element to the value effecting ejection forces the cover 2 to come close, but always slightly below this value, cooling gas to flow through the channels. In the lower remains. Part of the channel 3, which is empty and without fuel, FIG. 3 shows a modified embodiment elements is shown, is a locking piece 11 to represent, in which the horizontal gap 13 is not from Regulation of the coolant throughput provided. The circumference of the reactor is supplied with cooling gas, At the upper part of the channel 3 there is a certain pressure loss, rather than an annular cross-section caused by the fact that the invention 21, which advantageously around the control rods 23 according to a branched-off cooling gas flow through pipes 22 leading around openings 40 of the reactor gen 12 is directed into the channel. These are refrigerant gas. In this exemplary embodiment, the reactants are is distributed to the individual reactor channels through gate channels in the manner of a regular network, a horizontal gap 13 distributed in the upper so that each for receiving a control shield is arranged; the branched cooling rod reserved channel or pipe a group gas component flows through lateral supply lines 14 45 of channels assigned to the fuel elements included along the path indicated by the arrows 15. The above solution then allows one to the gap 13. easier sealing of the upper thermal seal F i g. 2 shows in detail the construction of the pre-shielding against the cooling gas. It is sufficient to set the direction to avoid the ejection of the combustion space 13, which is one of the groups of Kanästoffelemente. In this figure, the upper end 50 is assigned and in which one of the ring-shaped channels 3 is shown, which opens centrally after penetrating the passage, to be laterally closed off by a sheet 24 running on the circumference of the reflector 2 and the upper thermal shielding; hiermung4 flows out over this. This latter is subdivided by adjacent groups from one another by partition walls 16, whereby a fluidically separated,
Suitable passage 17 for various lines or 55 In the context of the invention, further AusRohre are kept free, which are not shown, since examples of management are possible,
they are not important to the invention; this line ...
genes are only for monitoring the reactor of claims:
Channel to channel important. Under the passage 17 is 1st safety device to avoid a horizontal gap 13 according to the invention for ejecting fuel elements when a branched off amount of cooling gas is removed from vertically arranged reactor channels. The openings 12, through which the coolant flows under pressure because the branched cooling gas component flows into the channel, are characterized in that each channel is drilled into the channel wall and is regularly distributed around its circumference on its supply side for the cooling. In addition, the diameter of the openings at the end opposite the gas is dimensioned in such a way that the pressure drop along the correct size is reduced with a secondary fuel element to such an extent that the ducts are in communication through the fuel elements or the only one in the Duct reduction of the pressure drop along the combustion Substance elements of the reactor channel, a gas portion shown by the main cooling circuit is fed. 2. Apparatus according to claim 1, characterized in that the provided in the channel wall Openings closed during normal operation by a removable closure piece are. 3. Apparatus according to claim 1, characterized in that the secondary channels in a horizontal Manifold gap open in the upper thermal shield of the reactor in the The height of the openings in the channel wall is arranged. 4. Apparatus according to claim 3, characterized in that the side channels on the side Perimeter of the reactor are arranged. 5. Apparatus according to claim 3, characterized in that the secondary channels of in cross section annular passages are formed, which are the ones for receiving the control rods Surrounding the reactor provided tubes. 6. Apparatus according to claim 5, characterized in that each annular passage in the Center of a channel group is arranged, with the seal between adjacent groups in the horizontal distributor gap by means of one running along the perimeter of the group Sheet metal is made that separates each group from the neighboring groups. Considered publications:
German interpretative document No. 1 075 231. 1 sheet of drawings 509 580/293 6.65 © Bundesdruckerei Berlin