WO1997039457A1 - Canister for holding fuel rods containing nuclear fuel - Google Patents

Abstract

A thin-walled canister to hold fuel rods has a base (9) on the canister bottom (3) on which the lower ends of the fuel rods are placed. In addition there is a securing plate (19) to hold the upper ends of the fuel rods down and for which there is an engagement member which can engage in a recess inside the canister wall ( ). In the engaged position the securing plate (19) is supported towards the canister aperture.

Description

description

Canister for holding fuel rods containing nuclear fuel

A canister for receiving spent nuclear reactor fuel elements is known from DOE / RW-0476, "OCRWM Bulletin", summer 1995, in particular pages 1 to 3 and 15. This canister is hollow-cylindrical in shape, has a canister base at one end and the other end a canister opening in which a shielding plate is arranged The canister opening is closed with a plate-shaped inner cover covering the shielding plate and with an outer cover covering this inner cover The canister with the nuclear reactor fuel elements located in the basket can be inserted into a barrel-shaped transfer container and in this transfer container to an intermediate storage facility with concrete shielding for the canister and away from this interim storage facility be transported. The canister can also be deposited with the spent nuclear fuel in a geological repository.

The basket with the nuclear reactor separation elements in the canister must ultimately be supported on the lids with which this canister is closed. In the event of accelerations or decelerations which the known canister experiences during transportation, the lid of the canister is therefore exposed to mechanical stresses which, under certain circumstances, can only be absorbed if the canister and the lid for closing this canister are proportionate are thick-walled. This means not only a high weight for the canister, but also loss of storage space in the canister if the dimensions of the barrel-like transfer container are fixed. The object of the invention is to remedy this and, in particular, to make the canister thin-walled.

This object is achieved according to the invention by a canister according to claim 1.

The wall of this canister is accelerated or decelerated by a nuclear reactor fuel element located in the canister only under tension in the longitudinal direction of the wall, but not under pressure transverse to this longitudinal direction, so that this wall can be made relatively thin. Also, a lid of the canister can not only be relatively thin-walled, but the connection between such a lid and the wall essentially only has the function of a gas-impermeable seal, since the lid also has a nuclear reactor fuel element located in the interior of the canister do not exert any force on the lid when accelerating or decelerating the canister.

Advantageously, at least one tube can be provided which is led from the canister bottom to the chamber opening in the interior of the canister and which loosely engages through the holding plate. Such a pipe can be used to suck water from the interior of the open canister. Such a tube can, however, also be used to blow a gas, in particular air, over the bottom of the interior of the canister in order to dry and possibly also cool the interior and a nuclear reactor fuel element located in this interior after the water has been drawn off.

Conveniently, the canister wall between the latching point and the chamber opening is frustoconically widened towards the canister opening, so that the cover can be seated without play. The invention and its advantages are explained in more detail with reference to the drawing using an exemplary embodiment:

1 shows a canister according to the invention in longitudinal section;

FIG. 2 also shows a longitudinal section of a fuel assembly pool with a canister according to FIG. 1 and a device for closing this canister with a lid;

FIG. 3 shows a longitudinal section of a transport and storage container for several canisters according to FIG. 1.

1 has a hollow-cylindrical can wall 2 and an outwardly curved canister bottom 3 at the lower end. At the top, the canister wall 2 forms an inwardly open, surrounding bead 4, which is located in a plane perpendicular to the longitudinal axis 5 of the canister. Between this bead 4 and a canister opening 6 at the upper end of the canister, the canister wall 2 widens towards the container opening 6 in the form of a frustoconical wall part 2a.

A canister lid 7 is inserted into the canister opening 6. This canister lid 7 is deep-drawn to form a frustoconical collar 8. The frustoconical collar 8 fits snugly against the inside of the frustoconically widening canister wall between the bead 4 and the canister opening 6 at the upper end of the canister. The edge of the frustoconical collar 8 ends with the canister opening 6.

The truncated cone-like collar 8 of the canister cover 7 is fixed to the inside of the truncated cone-like extension 2a of the canister wall 2 via two mutually spaced, mutually parallel, gas-tight circumferential weld seams 2b and 2c. welded. In the center of the canister cover 7, on the outside inside the collar 8 of the cylinder cover 7, there is a hollow cylinder-shaped attack body 9 for handling the canister cover 7.

In the interior of the canister, on the canister base 3, there is an annular base 9 made of stainless steel, in whose ring opening facing the upper end of the canister is inserted the fuel element base 11 of a nuclear reactor fuel element 10, which has a square cross section. In addition to the fuel element base 11, this nuclear reactor fuel element 10 has a fuel element head 12 with a square cross section and fuel rod 13 and control rod guide tubes 14. Each control rod guide tube 14 is screwed at its lower end to the fuel assembly base 11 and with its upper end to the fuel assembly head 12. Furthermore, the fuel assembly 11 with the fuel rods 13 and a lower part of the fuel assembly 12 are enclosed by two angle plates 15, which stand together with the nuclear reactor fuel element 10 on the base 9 within the interior of the canister and whose bending edges are parallel to the longitudinal axis 5 of the canister.

In this way, the angle plates 15 form the wall of a channel with a square cross-section, on the upper edges of which face the opening 6 of the canister, the angle plates 15 are inclined outwards and thus form a kind of funnel 16 as an aid in the insertion of the nuclear reactor fuel element 10 into the canister .

The fuel assembly head 12 has hold-down springs 17. These are helical springs with a spring axis 18 parallel to the longitudinal axis of the nuclear reactor fuel element 10 and thus also to the longitudinal axis 5 of the canister limited. A holding plate 19 compresses the coil springs 17 and braces itself against a snap ring (C-Rmg) 20 m in the direction of the opening 6 of the canister. This snap ring (C-Rmg) 20 is a locking element for the holding plate 19, which is blown into the circumferential bead 4 on the inside of the canister wall 2, ie locked with this canister wall

In the canister interior, two pipes 21 and 22 are led from the canister bottom 3 to the canister opening 6 and covered by the chamber lid 7. Both tubes 21 and 22 pass loosely through the holding plate 19. While the tube 21 with the smaller inside and outside diameter is led through the base 9 and mounts at the deepest point of the canister bottom 3, which is curved outwards, the tube 22 with a larger inside and outside diameter is also through the base 9 led, but it ends above the canister bottom 3 in the annular space of the base 9.

As shown in FIG. 2, a vertical support column 24 is located in a fuel element pool 23 filled with water. This support column 24 carries two superposed arms 25, which belong to a cooker 26.

A canister corresponding to FIG. 1 without a cover 7 and without a holding plate 19 with a vertical longitudinal axis 5 was first inserted into this cooker 26 under water with the aid of a lifting device. Then, using the lifting device, a nuclear reactor fuel element 10 with burnt-out fuel rods 13 was also inserted into the canister through the canister opening 6. The holding plate 19 was then placed on the hold-down springs 17 and pressed under compression of the hold-down springs 17 on the fuel assembly head 12 until the C-Rmg 20 could be blasted into the bead 4. A watertight hood 28 was then placed on an outer flange of the quiver 26 by means of guide bolts 29 located on the outer flange 27. Both at the upper end of the tube 21 with a smaller inside and outside diameter and at the top end of the tube 22 with a larger inside and outside diameter, an end of a U-tube is connected. In Fig. 2 only the U-tube 30 for the tube 22 is shown, but not the U-tube for the tube 21. Such a U-tube 30 is pivoted with its other end about a pivot axis perpendicular to the longitudinal axis of the tube 22 attached bar in the hood 28 and shown in dashed lines in semer starting position in Fig. 2. From this starting position, the U-tube 30 is pivoted about the pivot axis at one end until the other end is docked at the upper end of the tube 22.

While the water is sucked out of the canister arranged in the cooker 26 according to FIG. 1 by the U-tube, which is not shown in FIG. 2 and is docked at the upper end of the tube 21, the water is extracted from the quiver itself and also from the hood 28 Pumped tube, not shown in Fig. 2, which mouths the stove at the bottom of the stove 26 m.

After the water has been sucked out of the cooker 26 and the canister in the cooker 26, hot air is blown into the interior of the canister through the U-tube 30 into the tube 22 and the interior of the canister and the spent nuclear fuel element located there are dried.

The U-tube 30 is then pivoted back into the position shown in dashed lines in FIG. 2, as is the U-tube, not shown, connected to the tube 21.

The cap 7 assigned to the canister in the cooker 26 hangs with its base 9 on a piston rod 31, the piston of which is arranged inside the bell 28 and can be raised and lowered by correspondingly loading the cylinder 32 with compressed air. After the cover 7 has been inserted into the canister opening 6 with the aid of the piston rod 31, the frustoconical collar 8 of the canister cover 7 is welded to the frustoconical wall part 2a of the canister wall 2 with the aid of a welding device 33. This welding device 33 is displaceable on a jacket lime or bevel 34 which is parallel to the jacket line of the frustoconical wall part 2a of the canister wall 2, with which this jacket line or bevel lies in each case in the same plane.

The bevel 34 itself sits on the outside of a hollow cylinder 35, which is placed over a hollow-cylindrical support base 36 inside the hood 28 and its longitudinal axis with the longitudinal axis of the hollow cylinder 35, with the longitudinal axis of the piston rod 31 and with the longitudinal axis of the cooker 26 and the m the canister arranged in the cooker 26 coincides.

There are two bearings 37 between the hollow cylinder 35 and the hollow-cylindrical base 36. On the outside of the hollow cylinder 35 there is a ring gear 38, into which a gear 39 engages, which sits on the shaft of an electric drive motor 40. This electric drive motor 40 is also located within the hood 28. It moves the welding device 33 around the frustoconical wall part 2a of the canister wall 2 of the canister in the cooker 26.

After gas-tight welding of the canister cover 7 to the canister wall 2, air is introduced into the hood 28 through the pipe 30 and then the hood 28 is lifted off the flange 27. The closed canister is then lifted out of the stove 26 under water and inserted into the transport container 41 shown in FIG. 3, which is set up on the bottom of the fuel element pool 23, but is not shown in FIG. 2. If this transport container 41 is filled with canister, it is covered with an inner cover 42. The transport container 41 is then lifted out of the fuel pool 23. From the transport container 41 the water is then suctioned off and the interior of the transport container 41 is dried by evacuation.

An inner cover 42 is then screwed tightly into the opening of the transport container 41 using screw bolts, not shown. Then an outer cover 43 is placed on the opening of the transport container 41 and likewise screwed tight with screw bolts, not shown.

The decontaminated and closed transport container 41 with the canisters located in it can now be stored in an interim storage facility until the radioactivity and the resulting heat emission from the spent nuclear reactor fuel element stored in the canisters have subsided to such an extent that the canisters come out of the transport container 41 can be removed and used unopened, for example in gesture formats of a repository. Here, the canisters are much easier to handle than spent nuclear reactor fuel elements as such and as the transport container 41.

Claims

claims 1.Canister for holding fuel rods containing nuclear fuel, in particular fuel rods (13) which are bundled to form a nuclear reactor fuel element (10), with a base (9) on the canister base (3) for setting up the lower ends of the fuel rod and with a holding plate ( 19) for holding down the top ends of the fuel rod, which is assigned to the latching element, which can be latched at a latching point on the inside of the canister wall (2) and on which, in the latched state, the holding plate (19) ab¬ towards the canister opening is trimmed. 2. Canister according to claim 1 with a locking member, which is in a circumferential bead (4) on the inside of the Kani¬ sterwand (2) seated snap ring (20), which is located on the side facing the canister opening of the holding plate (19) . 3. Canister according to one of claims 1 and 2 with at least one tube (21, 22) which is guided in the interior of the canister from the canister bottom (3) to the canister opening and which loosely engages through the holding plate (19). 4. Canister according to claim 3 with an outwardly arched Canister bottom (3), which has a deepest point in the canister interior, and with a tube (21), which ends at this deepest point. 5. Canister according to claim 3 with a tube (21) which is guided through the base (9). 6. Canister according to claim 1 with a canister wall (2) which extends between the latching point and the canister opening m in the form of a truncated cone-like wall part (2a) to the canister opening hm. 7. Kan _i-edge according to claim 6 ⁱ to a canister lid ⁽⁷⁾ of the Kan _i steroffnung the like to form a frusto ^¬ collar n deep-drawn (8) and m ⁱ t ^t he In ^¬ nense _i te at the collar ⁽⁸⁾ of the canister wall (2) at the ⁱ kegelstumpfart part gen wall _(2a) of said canister wall ⁽²⁾ verschwe ⁱ Sst ^I st. 8. _A canister according to nspruch 7 with a circumferential pivoting ⁱ ßnaht _{(2b, 2c)} betwe en _h the collar (8) of the canister lid ⁽⁷⁾ an ^d the canister wall ^(2).