JPH0820560B2 - Volume reduction guide for long rod assembly - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a long rod which is sparsely hung from an upper structure when it is separated from the upper structure and inserted into a container for high volume reduction storage. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a volume guide device for a long rod assembly that can smoothly and efficiently guide a rod body into a container.

[0002]

2. Description of the Related Art The core of a pressurized water reactor (PWR) is
Hundreds of nuclear fuel assemblies are arranged in a grid pattern.When exchanging nuclear fuel assemblies regularly, a certain proportion of the nuclear fuel assemblies in the core are removed and the remaining nuclear fuel assemblies are arranged. Replace and add a new nuclear fuel assembly as much as it is removed.
At this time, in order to correct the variation in reactivity between the old and new nuclear fuel assemblies coexisting in the core, a burnable poison assembly is inserted in the new nuclear fuel assembly, and the nuclear fuel assembly is replaced. At this time, the burnable poison assemblies are removed from the old nuclear fuel assemblies having the reduced reactivity. The removed burnable poison aggregate has a high level of radioactivity and cannot be discarded as it is. Until the radioactivity disappears after volume reduction processing to reduce the overall volume and increase storage efficiency. , It is semi-permanently stored in a spent fuel pool, isolated from the outside world. These operations are carried out by a series of volume reducing devices that are remotely operated from the bridge crane installed in the spent fuel pit.

FIG. 3 is an illustration of an example of a burnable poison aggregate, and FIG. 4 is an illustration of volume reduction processing of a burnable poison aggregate. There are 17 burnable poison aggregates in Figure 3.
It is applied to a × 17 type nuclear fuel assembly, and in Fig. 4 (a), the whole is schematically shown by being compressed in the longitudinal direction, while Figs. 4 (b) and 4 (c) are shown in Fig. 4 (a). FIG.

Referring to FIG. 3, the burnable poison assembly is formed by suspending a large number of burnable poison rods W on a supporting portion U1 of an upper structure U with nuts U2. The burnable poison rod W is a zircaloy metal tube filled with alumina pellets containing boron and hermetically sealed at both ends. The burnable poison rod W has a slender appearance with a diameter of 9 to 13 mm and a length of about 4 m. , Is positioned at a position according to the distribution of the burnable poison insertion pipe (same as the control rod guide pipe) of the nuclear fuel assembly.

In FIG. 4, the used burnable poison aggregates taken out of the core are rapidly carried into a dedicated pool provided on the plant site, and after being cooled for a certain period, they are remotely operated. The burnable poison rod W is suspended and set in the volume reduction guide device (disassembly basket) G, the burnable poison rod W is separated from the upper structure U in water, and the separated burnable poison rod W is reduced in volume. Guiding device G
215mm x 2 with the upper end opened just below
It is stored together in an elongated rectangular storage container having a length of 15 mm and a length of 4 m, and is stored in water together with this storage container. The volume-reduction guide device G has an inlet I through which a large number of burnable poison rods W sparsely hung on the supporting portion U1 are passed as they are,
An outlet D corresponding to the inlet of the storage container is connected by a cylindrical body including an inclined portion T, three fixing plates K having holes formed according to the distribution of the burnable poison rod W, and the nut removed It has a storage container N of U2 and guides a large number of sparsely suspended burnable poison rods W toward a dense storage state.

[0006]

The volume reduction treatment of burnable poison aggregates is carried out by arranging vertically the storage containers of the burnable poison aggregates and the burnable poison rods W each having a total length of more than 4 m. In order to save the water depth of the pool, the vertical dimension of the volume-reducing guide device G is set in a state in which the burnable poison aggregate is set, that is, the burnable poison at the inlet I of the volume-reducing guide device G. Support unit U1 of the assembly
, The tip of the burnable poison rod W is already reduced in volume at the inclined portion T and is guided to the exit D,
A lock mechanism E that temporarily prevents the rod from falling is attached to this portion. The nut U2 is released for the first time in this state,
Next, the lock mechanism E is also released, and the burnable poison rod W is dropped all at once into the storage container.

However, since the burnable poison rod W is long and easily bends, when the burnable poison aggregate is suspended in the volume reducing guide G, as shown in FIGS. 4 (b) and 4 (c). When the tips of the burnable poison rods W interfere irregularly with each other at the inclined portion T and push in an arch shape inside the inclined portion T, the volume guide device G for reducing the volume of the burnable poison assembly is introduced. You can no longer hang it inside. If this is not done, the burnable poison rod W may be deformed or damaged, so that the burnable poison aggregate is lifted and again suspended in the volume guide apparatus G.

In the conventional burnable poison assembly of the 15 × 15 type nuclear fuel assembly, since the number of burnable poison rods is small, the burnable poison rods interfere with each other. However, the number of burnable poison rods W is large in the new 17 × 17 type nuclear fuel assembly burnable poison assembly, so it is possible to suspend the burnable poison assembly. The loss rate reaches 80%, and as a result of redoing the setting of the burnable poison aggregate to the volume reduction guide device G many times, the efficiency of volume reduction treatment of the burnable poison aggregate is reduced and the volume guide device is reduced. Reduces the reliability of.

According to the present invention, even if the number of burnable poison rods is large, the interference of the burnable poison rods in the inclined portion is small under the condition that the vertical dimension of the volume reduction guide device is maintained at the current state, and the burnable poison rods are small. 1 set of Nab Poison Aggregation
The purpose is to provide a volume reduction guide device that can be completed promptly.

[0010]

A volume reduction guide device for a long rod assembly according to claim 1, which guides a large number of long rods that are sparsely suspended toward a densely packed state. In the volume reduction guide device, the external cylinder member with a volume reduction slope connecting the inlet corresponding to the large number of sparsely suspended long bars and the outlet corresponding to the densely packed state, An inner frame member provided with an inclined portion of the tubular member and having a volume-reducing inclination for separating the guide path of the long rod located inside from the guide path of the long rod located outside.

A volume guiding apparatus for a long rod assembly according to a second aspect is the volume guiding apparatus for a long rod assembly according to claim 1,
The outline of the cross section of the inner frame member is circular, and the long rod positioned outside is easily moved along the outline.

[0012]

In the volume reduction guide device for a long rod assembly according to claim 1,
The inner frame member separates the long rods located inside from the long rods located outside, and the volume reduction inclination of the outer cylinder member exclusively changes the long rods located outside to the dense state. The long bar having the inner frame member whose volume reduction inclination is located inside is guided from the sparse state to the dense state. Therefore, at least in the range of the length of the inner frame member, the long rod positioned inside does not interfere with the long rod positioned outside, and the long rod positioned outside and suspended on the opposite side. Also for each other, the inner frame members interfere with each other and cannot interfere with each other. In the space divided by the inner frame member and the outer cylinder member, the small number of long rods adjacent to each other interfere with each other, and the long rods smoothly transition to a dense state where they contact each other. It is unlikely that it will be pushed into a shape.

According to another aspect of the volume guiding apparatus for a long rod assembly of the present invention, when the long rods located outside interfere with each other in the process of suspending the long rod assembly on the volume guiding apparatus, the inner frame member. The long rods that have contacted with each other slide and move along the contour of the inner frame member, and the long rods are guided to stable positions where the interference state is relatively light.

[0014]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory diagram of a volume reduction guide device for a burnable poison assembly according to the first embodiment. Where (a)
Is a cross-sectional view schematically showing the entire volume reduction guide apparatus compressed vertically, and (b) is a cross-sectional view taken along the line BB of (a), in which the burnable poison assembly is suspended. An additional burnable poison rod is shown.

In FIG. 1 (a), a volume-reduction guide device (disassembly basket) G1 is an inlet I through which a large number of burnable poison rods sparsely hung on a support portion pass through as they are.
And an outlet D corresponding to the inlet of the storage container are connected by a tubular body including an inclined portion T, and a BP rod guide tube S1 having a circular cross section is arranged inside the inclined portion T. Guide tube S
1 is fixed to a lower fixing plate K, and a steady rest F connected to the inner wall of the inclined portion T is attached to the middle portion of the BP rod guide tube S1. 3 placed above the volume reduction guide G1
A large number of holes corresponding to the distribution of the burnable poison rods are formed in the fixed plate K, and each of the burnable poison rods is guided when the aggregate of the burnable poison rods is suspended. The storage container N stores the nuts removed from the burnable poison aggregate.

On the other hand, the vertical dimension of the volume guide apparatus G1 is a bar.
With the navel poison assembly set, that is, with the support portion of the burnable poison assembly placed at the entrance I of the volume reduction guide G1, the tip of the burnable poison rod is already reduced at the inclined portion T. The nut of the burnable poison aggregate is released for the first time in this state until the vertical portion of the exit D is accommodated, and the tip of the burnable poison rod descends to the lock mechanism E. Next, volume reduction guide G
By setting 1 on the storage container and releasing the lock mechanism E, the burnable poison rod is dropped into the storage container all at once.

When the burnable poison aggregate is hung on the volume guide apparatus G1 thus constructed, as shown in FIG. 1 (b), the burnable poison rod W2 located on the inside is BP. The burnable poison rod W, which is guided by the rod guide tube S1 and has its volume reduced independently, is located outside on the way.
There is no opportunity to interfere with 1. On the other hand, the burnable poison rod W1 located on the outer side is reduced in volume along the inner wall of the inclined portion T, but on the way, the burnable poison rod W1 is interfered with by the BP rod guide tube S1 and the burnable poison rod W1 located on the opposite side. There is no opportunity to interfere with each other, and as the burnable poison aggregate is suspended, it is divided into a small number of adjacent burnable poison rods W1 groups, and each group is divided into BP rod guide tubes S1. It is guided along the circular contour of the to a relatively light and stable state of interference.

Therefore, even when the burnable poison assembly of the new 17 × 17 type nuclear fuel assembly is suspended and set in the volume reduction guide G1, the burnable poison rods interfere with each other on the way. It is no longer possible to hang the Burnable Poison Aggregate, and 100% completes the setting once.

FIG. 2 is an explanatory diagram of a volume reduction guide device for a burnable poison assembly according to the second embodiment. Where (a)
Is a sectional view schematically showing the entire volume reduction guide apparatus compressed vertically, and (b) is a sectional view taken along line BB of (a), in which the burnable poison aggregate is suspended. An additional burnable poison rod is shown.

In FIG. 2 (a), a volume-reducing guide device (disassembly basket) G2 is an inlet I through which a large number of burnable poison rods sparsely hung on a supporting portion pass through.
And an outlet D corresponding to the inlet of the storage container are connected by a tubular body including an inclined portion T, and a BP rod guide tube S2 having a rectangular cross section is arranged inside the inclined portion T. Guide tube S
The space inside 2 is divided into four by a partition H, and the entire BP rod guide tube S2 is fixed to a lower fixing plate K. On the three fixing plates K arranged on the upper part of the volume reduction guide device G2,
A large number of holes are formed according to the distribution of the burnable poison rods, and guide each burnable poison rod when the burnable poison aggregate is suspended.
The storage container N stores the nuts removed from the burnable poison aggregate.

On the other hand, the vertical dimension of the volume guide apparatus G2 is a bar.
With the navel poison assembly set, that is, with the support portion of the burnable poison assembly placed at the entrance I of the volume reduction guide G2, the tip of the burnable poison rod is already reduced at the inclined portion T. The nut of the burnable poison aggregate is released for the first time in this state until the vertical portion of the exit D is accommodated, and the tip of the burnable poison rod descends to the lock mechanism E. Next, volume reduction guide G
By setting 1 on the storage container and releasing the lock mechanism E, the burnable poison rod is dropped into the storage container all at once.

When the burnable poison assembly is suspended from the volume guiding apparatus G2 thus constructed, as shown in FIG. 2 (b), the four burnable poison rods located inside are installed. W2 is guided to each of the spaces divided into four by the partition wall H of the BP rod guide tube S2 to be reduced in volume, and there is no chance of interfering with the burnable poison rod W1 located outside. On the other hand, the burnable poison rod W1 located on the outer side is reduced in volume along the inner wall of the inclined portion T.
There is no opportunity to be interfered with by the P rod guide tube S2 and interfere with the burnable poison rod W1 located on the opposite side, and the burnable poison rod W1 is adjacent to the burnable poison rod W1 when the burnable poison aggregate is suspended. While maintaining the above, the volume is aligned between the BP rod guide tube S2 and the inclined portion T and the volume is reduced.

In the above embodiments, only the volume guide device for the burnable poison assembly has been described. However, the present invention is directed to a state in which a large number of long bars sparsely hung are closely packed. It is widely applicable to a volume guide device for a long rod assembly to be guided, and for example, a volume guide device for a burnable poison assembly applied to a nuclear fuel assembly other than 17 × 17 type is of course used. It can also be applied as a volume reduction guide device for spent nuclear fuel rods and spent control rods.

[0025]

According to the volume reduction guide device for a long rod assembly of the present invention, no matter how many long rods are provided in the long rod assembly due to the short vertical dimension of the volume reduction device, for example, , Even if the number of burnable poison rods is large, the interference between the long rods in the volume reduction inclination of the outer cylinder member is light, and therefore,
The work of suspending the long rod assembly on the volume reduction guide device can be performed reliably and quickly.

When the volume guiding apparatus for a long rod assembly of the present invention is applied to the volume guiding apparatus for a burnable poison assembly,
Under the condition that the vertical size of the volume reduction guide is maintained,
No matter how many nable poison rods are provided, interference of the bunnable poison rods in the inclined portion is reduced, and it is possible to reliably complete the setting of the bunnable poison assembly with respect to the volume guide device once. Therefore, the volume reduction work of the burnable poison aggregate can be made efficient, and the reliability of the volume reduction guide device can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a volume reduction guide device for a burnable poison aggregate according to a first embodiment.

FIG. 2 is an explanatory diagram of a volume reduction guide device for a burnable poison assembly according to a second embodiment.

FIG. 3 is an explanatory diagram of an example of a burnable poison aggregate.

FIG. 4 is an explanatory diagram of volume reduction processing of a burnable poison aggregate.

[Explanation of symbols]

 D exit E lock mechanism F steady rest metal fitting I entrance K fixing plate N storage container T slanted portion G1 volume reduction guide device (disassembly basket) S1 BP rod guide tube W1 burnable poison rod W2 burnable poison rod

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G21C 19/33 GDP F 19/37 GDP

Claims (2)

[Claims] 1. A volume reduction guide device for a long rod assembly, which guides a large number of long rods sparsely suspended toward a densely packed state, and corresponds to the large number of long rods sparsely suspended. An outer cylinder member with a volume-reducing inclination that connects the inlet and the outlet corresponding to the densely packed state, and a guide path for an elongated rod that is provided inside the inclined portion of the outer cylinder member and is located inside And an inner frame member with a volume-reducing inclination that separates from the guide path of the long bar located outside. 2. The volume guiding apparatus for a long rod assembly according to claim 1, wherein the cross section of the inner frame member has a circular shape, and the long bar positioned outside is easily moved along the contour. A volume reduction guide device for a long rod assembly, characterized in that