FR2525379A1 - IRRADIATION DEVICE FOR EXPOSING IRRADIED MATERIALS TO THE HEART OF A NUCLEAR REACTOR - Google Patents

Abstract

IN A NUCLEAR REACTOR CROSSED FROM TOP TO BOTTOM THROUGH A REFRIGERANT, THE IRRADIER SAMPLES ARE COOLED DIRECTLY BY THE REFRIGERANT OF THE REACTOR AND CAN NEVER BE CHARGED AND DISCHARGED FROM THE EXPOSURE CHANNEL WHILE THE REACTOR CONTINUES TO OPERATE. THE EXPOSURE CHANNEL, CROSSED BY THE REFRIGERANT, IS CLOSED, ABOVE REFRIGERANT INTAKE SLOTS 7, BY A CAP 16 WHILE THE CHANNEL IS NOT OCCUPIED. THIS PLUG MAY BE COUPLED BY APPROPRIATE MEANS 34, 15 TO THE LOWER END OF AN IRRADIATION CAPSULE 10 AND BE LOWERED WITH THIS CAPSULE IN THE CORE 5 OF THE REACTOR. THE INVENTION IS APPLICABLE TO ALL KINDS OF IRRADIATION, FOR EXAMPLE FOR THE PRODUCTION OF ISOTOPES.

Description

The invention relates to an irradiation device said to the heart (in-core)

  for a nuclear reactor traversed by a refrigerant, comprising a fixed anchored casing tube in the reactor core and surrounding at least one exposure channel for receiving a cylindrical irradiation capsule. Such a device is known from French Patent No. 2,126,079, for example. The casing tube is closed at the bottom and opens at the top again inside the funnel-shaped heart. To insert an irradiation capsule into the casing tube , it is necessary to bring in alignment with this tube a loading arm which passes through the lid of the reactor vessel, after which it is lowered

  in the tube encloses a container containing the material to be irradiated.

  Such an irradiation device only allows loading and unloading during shutdown of the reactor. Moreover, because the shell tube is closed on one side, there are difficulties in cooling the exposed material with As a result, temperatures that are neither well

  defined or can not be influenced effectively from the outside.

  French Patent 2,417,828 also describes a device

  irradiation in the heart where the samples to be irradiated can

  be placed in a fixed installed casing tube in the reactor.

  The samples are suspended from a locking head into which a manipulator arm which can be controlled from a point above the reactor cover is located. This head has latching or latching means in corresponding grooves on the upper edge of the tube wraps and closes this

  tube tightly in locked position.

  In this case also, the insertion and the extraction of the irradiation capsule are only possible when the reactor is stopped, because the manipulator must pass through the lid of the pressure vessel. Moreover, the cooling of the capsules

  poses the same difficulties as with the device mentioned above.

  above. British Patent 2,015,239 discloses a

  irradiation device with an envelope tube which has lateral

  Many of the openings for the passage of the reactor coolant are located in the lateral annular gap between the vessel and the reactor core and are flown or swept by the cold primary coolant.

  cooling is satisfactorily resolved here, the replacement

  As with the above-mentioned devices, it is only possible during shutdown of the reactor, since it is only then that the reactor cover can be opened and the access to the device

irradiation is possible.

  The purpose of the invention is to indicate an irradiation device that is efficiently traversed by the primary refrigerant.

  during operation and with which loading and unloading

  The advantage thus obtained is particularly important for research reactors where very long periods of operation are required between two or more of the capsules during operation of the reactor without disturbing it.

  reactor recharges (between two replacements of fuel elements

  the duration of exposure of the different irradiation capsules is variable and generally much shorter (by

  example for the production of radioisotopes).

  According to the invention, such a device is essentially characterized in that the jacket tube rests partly on the grid or bottom plate of the core, passes through the grid or upper plate of the core and is guided in the reactor vessel lid, that coolant intake slots are provided in the shell tube between the lid and the top plate, while the coolant can exit the jacket tube in the region of the bottom plate of the core, with coolant passages provided between the capsule irradiation and the wall of the exposure channel, that the irradiation capsule is coupled by its lower end to a slightly larger

  diameter that the capsule and the cap has means for

  which cooperate with corresponding means in the region

  the reactor cover for the refrigerated seal

the exhibition channel.

  It is advantageous for the irradiation capsule according to the invention to be detachably coupled by its end.

  superior, to a bar-shaped tool.

  In a preferred embodiment of the invention,

  the envelope tube contains three exposure channels which are

  independently of each other and can therefore also be

  loaded and unloaded completely independently of each other.

  Other features and advantages of the invention

  will be clearer from the following description of a

  non-limiting embodiment, and the accompanying drawings, in which Figure 1 is a partial vertical section of a reactor passing through an irradiation device according to the invention set up in this reactor; Figures 2 to 5 show on a larger scale different details of the representation of Figure 1; and Fig. 6 is a cross-section of the device, showing the three exposure channels according to the preferred embodiment, taken at the height of the exposure position following the

line 6-6 of FIG.

  The irradiation device shown in longitudinal section

  FIG. 1 is installed in a reactor of which only the bottom plate 1 and the upper plate 2 of the core and the top of the pressure vessel 3 with its lid 4 are shown in this figure. The core 5 itself of the reactor is enter

  the two plates or grids 1 and 2 and consists of combustion elements

  The refrigerant, eg water, is introduced from above through the top plate 2 into the core 5 of the reactor and passes through a plate. lower 1 in a heat exchanger not shown to yield the heat absorbed in the heart

of the reactor.

  At the desired exposure position of the core is a fixed casing tube 6, supported in part on the lower plate 1 of the core, passing through the upper plate 2 and extending into the lid 4 above the upper plate 2 of the core, the casing tube 6 has slots 7 of refrigerant inlet The normal reactor refrigerant enters through these slots in the casing tube and leaves it through orifices 8 to

its lower end.

  The casing tube 6 contains in fact three mutually independent irradiation devices, as can be seen in the horizontal section of FIG. 6. Each of these devices is located in a guide tube 9 fixedly mounted in the casing tube, which also has slits- & the height of the slots 7 of the enven-

  loppe and that is also open downstairs.

  The material to be irradiated is constituted in this example of stacks of tube sections 10 Each stack is threaded onto a central support bar 11 and is centered on the axis of this bar by adequate centering protuberances The support bar

  is hollow and is traversed longitudinally with a locking rod 12.

  A stack of tube sections 10 forms with the support bar 11 and the blocking rod 12 an irradiation capsule. FIG. 1 shows such a capsule at three different positions in one of the three irradiation devices or guide tubes. 9: a position

  at the top, an exposure position at the bottom and a posi-

  In the absence of other forces, a spring 13 (see FIG. 4) holds the locking rod 12 at its upper end position, where a collar 14 serves as a support. The locking rod has at its lower end a locking head 34 (see FIG. 5) which cooperates in such a way with snap-on balls 15 on the lower end of the support rod 11. the upper end of a cap 16 that the latter is coupled to the lower edge of the support bar 11 when the locking head 34 pushes the balls 15 in corresponding recesses on the lower edge of the bar

of support.

  The plug 16 is hollow and itself has a locking rod 17 with a locking head 18; in the absence of external forces, a spring 19 pushes the locking rod 17 towards

  the top, so that other snap-in balls 20, are

  on the plug 16, are pushed radially outwards.

  Figures 2 to 6 show the device irra-

  in the situation where it is during the exposure A central control part 21 (see Figure 3) of a tool described thereafter then presses the locking rod 12 inside the support bar Il and pushes this rod against the force of the spring 13 at its lower end position In the same way, the rod 12 then pushes down the locking rod 17 of the cap 16, against the force of the spring 19 at this position, the locking head 34 of the locking rod 12 couples the plug 16 to the support bar, the locking head 18 of the plug 16 does not act on

  the latching balls 20 during this time.

  The mentioned tool is coupled to the support bar 11 by other detent balls 22, penetrating into the upper edge of the bar 11 (FIG. 4), because these balls are prevented from escaping radially towards the liner. This sleeve forms the lower end of the movable control portion 21 of the tool When this part occupies its low position, the sleeve 23 covers the balls 22 and the locking rod 12 of the the support bar 11 is at the same time pushed towards

the bottom.

  The portion 21 of the tool is movable relative to a sleeve 24 is held in the low position, in the absence

  other forces, by a spring 25 (see Figure 2) which is more

  The sheath 24 of the tool surrounds the upper edge of the support bar 11 with its lower end 26 and can be coupled thereto, as indicated by

the balls 22.

  Between the lower end 26 and the head 27 of the tool,

  the sheath 24 and the movable control part 21 of the tool contain

  between them-an elastic seal 28 which, because of its elasticity,

  may participate in the control movements of the movable portion relative to the sleeve liquid refrigerant can not rise between the sleeve 24 and the guide tube 9 because the tool is sealed, in the exposure position and during the loading operations and of

  unloading, by an annular seal 29 (Figure 2).

  The moving part of the tool ends at the top,

  top of the lid 4 of the reactor vessel, by a handle 30 which

  is close to a handle 31 integral with the sleeve 24 of the tool.

  In order to prepare an irradiation cycle, the material to be irradiated, in this case the tube sections 10, is disposed of on

a support bar 11 -

  The exposure channel in which this material is to be inserted is sealed during this preparation by

  a plug 16 "which maintains itself in a locking position

  lage, in the region of the lid 4 of the reactor in the guide tube 9, under the effect of the pressure of the spring 19, by the latching balls

  engaged in a corresponding annular groove of the guide tube 9.

  At this position, a sealing surface 35 of the plug 16 "bears against a corresponding sealing shoulder of the guide tube 9 in the region of the cover 4, so as to close the exposure channel in a sealed manner. , meanwhile, penetrate unhindered through the intake slots 7 in the exhibition channel

  * and come out through the holes 8.

  When the capsule to be irradiated made of the material

  to irradiate, the support bar 11 and the locking rod 12 -

  is placed on such a plug 16 "locked in the lid 4, the support bar is only coupled to this plug when the tool forms the movable portion 21 and the sleeve 24 is placed on the capsule,

  which requires the short approximation of the two handles 30 and 31.

  When the handles are released, the spring 25 pushes the locking rod downwards and first produces the locking of the cap 16 "to the support bar and the locking of the support bar to the support bar.

  the tool and then unlocking the plug 16 "in the guide tube.

  From this moment, the tightness of the channel in which the pressure reigns

  reactor refrigerant is no longer provided by the surface of

  the plug but by the annular seal 39, which then seals during the lowering of the capsule to the exposure position, during the exposure period which makes it

  continued and also during the extraction of the capsule.

  As already mentioned, Figure 1 shows schematically

  three possible positions of the irradiation capsule in the channel 2.

  A loading position (16 "cap), an exposure position

  (cap 16) and a parking position (cap 161).

  When the capsule occupies the exposure position, the cooling water, penetrating through the slots 7 above the upper plate 2 in the guide tube, flows along the lower part of the tool, the 10 to irradiate and the plug 16, a portion of the cooling water entering through slots 33 at the top of the stack of tube sections forming the material 10 to be irradiated, as can be seen in Figure 4 inside the pipe sections, to emerge at the lower end of the stack through openings 32 (FIG. 5). The irradiated material is thus efficiently cooled and on both sides by the reactor coolant. refrigerant is not interrupted during the lifting of the capsule,

  as long as it is below the slits 7 It is therefore

  As far as possible, by means of suitable locking means on the head of the tool, to immobilize the capsule at a parking position where it is already above the upper plate 2 of the core but still below the intake slots 7 At this position, the isotopes are disintegrated rapidly without radiation-harmful to the environment The exposure channel is also sealed at this parking position against the cooling water outlet,

by the annular seal 29.

  Figures 1 to 5 show only one exposure channel inside the casing tube 6 This channel could

  also fill the entire cross-section of the envelope tube 6 Cepen-

  As can be seen in FIG. 6, the device of the example shown comprises three parallel exposure channels, each comprising a stack of tube sections forming the material to be irradiated, a support bar 11, a rod of blocking 12 and a guide tube 9 The three exposure channels are each loaded and unloaded with a separate tool and can be unloaded and loaded completely independently of one another and replacement cycles This gives optimum flexibility of the irradiation cycles, as

  is necessary for the production of the most diverse radionuclides.

  As just described, the invention offers the possibility, for the first time, of producing the irradiation of samples in a pressure vessel with cooling of the samples by the reactor coolant during irradiation and with the possibility of loading the samples, unloading them and bringing them to a parking position independently of the reactor charging cycle. The pressure vessel can be in a pool whose water can not at any time enter in

  contact with the refrigerant running through the exposure channel.

s.

Claims (1)

R E V E N D I C AT IO N S -; 1 irradiation device said heart (in-core) for a nuclear reactor flowing from top to bottom of a refrigerant, comprising a fixed anchored casing tube in the reactor core and -'T 5 -entourant at least one channel exposure device for receiving a cylindrical irradiation capsule, characterized in that the casing tube (6) rests in part on the lower grid or plate (1) (i -from the core, passes through the grid or upper plate ( 2) of the core and is guided in the lid (4) of the tank (3) of the reactor, that * ::, 10 slots (7) of refrigerant intake are formed in the tube * -: "-wrap between the lid and the top plate, while the refrigerant can exit (8) from the jacket tube in the region of the lower core plate, with coolant passages being provided between the irradiation capsule (10-14) and the wall of the exposure channel, that the irradiation capsule is connectable by its end lower than a cap (16) slightly larger in diameter than the cap and the cap has latching means (17 to 20) which cooperate with corresponding means in the region of the lid (4) of the reactor in order to the refrigerant seal of the exposure channel. 2 Device according to claim 1, characterized in that the upper end of the irradiation capsule (10-14) is coupled to a bar-shaped tool. Device according to claim 2, characterized in that the irradiation capsule (10-14) is equipped for ring-shaped irradiation samples (10) and has a bar of central support (11) which is traversed by a locking rod (12) displaceable relative to the samples in the direction of the axis of the channel and producing the coupling of the plug (16) to the capsule. Device according to claim 3, characterized in that the tool consists of two mutually displaceable parts: A, in the direction of the axis of the channel, one of which is formed by a 0 t sheath (24) connectable to the irradiation capsule (10-14) and 1 lmirtre (21) acts in the axial direction on the locking rod (12) of the support bar (11). Device according to any one of claims 1 to 4, characterized in that the casing tube (6) contains three mutually independent exposure channels. Device according to any one of the claims   1 to 5, characterized in that the irradiation capsule is capable of being locked at an intermediate position where the capsule (10-14) is already above the upper plate (2) of the heart but   is still below the refrigerant intake slits (7).