JP2000337777A - Sintering device for powder molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate areas into which an atmospheric gas hardly penetrate and, in addition, to improve the productivity of a sintering device by boring many holes through the side plate and bottom plate of a container for sintering and, at the same time, forming atmospheric gas supplying paths in a skid. SOLUTION: An atmospheric gas which is supplied to a sintering furnace at the time of sintering powder moldings 11 flows in a container 7 for sintering through the top opening of the container 7 and many holes 12 bored through the side plate of the container 7, and filtrates through the bodies 11. Part of the atmospheric gas, on the other hand, is introduced to a skid 6 through atmospheric gas introducing holes 15 formed in the skid guides 10a and 10a of the hearth 10 of the furnace and the long holes of the skid 6, and further flows in the container 7 through a plurality of holes 14 formed through the upper wall surface of the skit 6 and holes 12 made through the bottom plate of the container 7. After flowing in the container 7, the atmospheric gas infiltrates through the powder moldings 11. Therefore, the atmospheric gas is introduced to the deepest portion of the container 7 and makes the removal, etc., of additives added to the moldings 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for sintering powder compacts such as nuclear fuel pellets.

[0002]

2. Description of the Related Art FIG. 2 is a plan view showing a schematic structure of a continuous sintering furnace. An inlet chamber 2 and an outlet chamber 3 are provided at both ends of a sintering furnace 1 extending in the left-right direction. An inlet replacement chamber 4 is provided on the side of the inlet chamber 2, and an outlet replacement chamber 5 is provided on a side of the outlet chamber 3. The hearth of the sintering furnace is made of alumina bricks, and a skid 6 made of a thick plate made of molybdenum is placed and arranged on the hearth, and a large number of UO ₂ molded bodies or Gd ₂ are placed on each skid 6. A box-shaped sintering container 7 loaded with a powder compact such as a UO ₂ compact containing O ₃ is placed, and the compact is pushed through the sintering furnace from the inlet to the outlet by pushing the skid 6 with a pusher. Moved towards.

That is, a sintering vessel 7 loaded with a large number of powder compacts is placed on a skid 6 and an inlet replacement chamber 4 is provided.
When it is inserted into the entrance chamber 2 by the entrance pusher 8
Is pushed into. When the skid 6 on which the sintering vessel 7 is placed is pushed into the inlet chamber 2, the skid 6 is pushed into the sintering furnace 1 by the main pusher 9 at the sintering furnace entrance, and thereby the tip of the The skid 6 is pushed out to the outlet chamber 3. Then, the main pusher 9 retreats, and the next skid 6 is sent into the entrance chamber 2. Thereafter, in the same manner, the sintering vessel 7 and the sintering vessel 7 are sequentially moved in the sintering furnace 1 while the powder compact is sintered.

FIG. 3 is a longitudinal sectional view of the sintering furnace 1. A hearth 10 made of alumina brick is laid on the bottom surface of the sintering furnace 1. A large number of skids 6 made of a thick plate made of molybdenum are arranged in the longitudinal direction, and a sintering container 7 containing a large number of powder compacts 11 is placed on each of the skids 6. Then, as described above, the sintering vessel 7 is mounted together with the skid 6 in the sintering furnace 1.
Is moved in the longitudinal direction.

When sintering nuclear fuel pellets, which are powder compacts, the compacts are sintered at a high temperature exceeding 1700 ° C. in a tunnel-type continuous sintering furnace as described above. It is brought into contact with the atmosphere gas in the furnace to decompose additives in the molded body, remove impurities, and control the O / U ratio by a chemical reaction.

[0006]

As described above, the molded article
Gas generated by decomposition of additives in the tank without problems
Removal or precise control of the O / U ratio,
Gd_TwoO_ThreeEntering UO _TwoOxygen Content Required for Solid Solution Formation
In order to supply air, always use fresh atmospheric gas
Need to keep supplying.

However, the box-shaped sintering container 7 contains a large number of compacts 11 which are densely stacked and accommodated, and the atmospheric gas permeates the sintering container 7 only from above. Therefore, the supply of the atmospheric gas may not always be sufficient.

Therefore, as shown in FIG. 3, a large number of holes 12 are formed in the side plate of the sintering vessel 7 to facilitate the permeation of the atmospheric gas into the sintering vessel 7.

However, since the sintering container 7 is mounted on the thick plate-shaped skid 6 and the bottom plate is formed of a simple plate, the atmosphere gas is sintered from the bottom of the sintering container. It is impossible to infiltrate into the sintering container, and the supply of the atmospheric gas is insufficient at the deep portion of the sintering container 7 indicated by cross-hatching in FIGS. 4 and 5. Due to the insufficient supply of the atmospheric gas, the molded product is exposed to the maximum temperature range without being sufficiently removed and with the O / U ratio being higher than 2.0. However, there is a problem that the additive which has not been exploded decomposes explosively, and sintering progresses rapidly due to a high O / U ratio, and problems such as cracks and deformation may occur in the molded body.

When Gd ₂ O ₃ is added, the oxygen content in the atmospheric gas is not sufficiently supplied to the deep portion of the sintering vessel, and the formation of a sound solid solution is hindered by uneven sintering.
Problems such as a decrease in density and generation of fine cracks occur. To prevent this problem, the supply amount of the atmosphere gas must be increased to increase the amount of gas permeating into the sintering vessel, but increasing the gas flow rate increases the cost and increases the atmosphere gas. Even if it does, there is a problem that it is difficult to sufficiently infiltrate the atmosphere gas into the deep part of the sintering vessel.

In view of the above, the present invention eliminates a region in which atmospheric gas is unlikely to penetrate into a sintering vessel carried into a continuous tunnel furnace, and generates cracks, lowers density, and deforms the sintered body. It is an object of the present invention to provide a sintering apparatus that can prevent the occurrence of the above-mentioned problems and can increase the productivity.

[0012]

According to a first aspect of the present invention, a large number of holes are formed in a side plate and a bottom plate of a sintering container accommodating a large number of powder compacts, and the sintering container is placed thereon. An atmosphere gas supply path is formed in a skid that can be moved on a hearth of a sintering furnace, the atmosphere gas supply path communicating from a side surface to an upper surface.

According to a second aspect of the present invention, in the first aspect, an atmosphere gas introduction hole for introducing an atmosphere gas into the skid is formed in a skid guide portion provided on both sides of the hearth of the sintering furnace. It is characterized by.

[0014]

Embodiments of the present invention will be described below with reference to FIG. In the figure, the same parts as those in FIG. 3 are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 shows a hearth 1 in a sintering apparatus according to the present invention.
FIG. 3 is a cross-sectional view of a skid 6 and a sintering vessel 7 mounted and moved on a hearth 10 of the hearth 10. The hearth 10 has skid guides 10 a extending longitudinally on both side edges thereof.
10a, the skid guides 10a,
A skid passage 10b is recessed between 10a.

A skid 6 on which a sintering vessel 7 is placed is placed on the skid passage 10b of the hearth 10. The sintering vessel 7 has a large number of holes 12 formed not only on its side plate but also on its bottom plate. On the other hand, the skid 6 is formed in a hollow shape, a long hole 13 is formed in the left and right side wall portions along the traveling direction of the skid 6 in the traveling direction, and a plurality of holes 14 are formed in the upper wall portion. . That is,
An atmosphere gas supply path is formed in the skid 6 by a long hole 13, a hollow portion, and a hole 14 and communicates from the side surface to the upper surface.

The two skid guides 1 of the hearth 10
At 0 a and 10 a, an atmosphere gas introduction hole 15 that connects the skid passage 10 b and the outside of the hearth 10 is formed.

The atmosphere gas supplied into the sintering furnace during the sintering of the powder compact 11 passes through the top opening of the sintering vessel 7 and the large number of holes 12 formed in the side plate, and is supplied to the sintering vessel. 7 and penetrate between the powder compacts 11. on the other hand,
Part of the atmosphere gas supplied into the sintering furnace is
The skid guides 10a, 10a are introduced into the skid 6 through the atmosphere gas introduction holes 15 and the long holes 13 of the skid 6, and are further formed into a plurality of holes 14 formed in the upper wall surface and the sintering container 7. The powder also flows into the sintering container 7 from the bottom through the hole 12 formed in the bottom plate, and the powder compact 1
Penetrate between one.

Therefore, the atmospheric gas is sufficiently introduced also into the deepest part in the sintering vessel, so that the additives in the powder compact can be reliably removed.

Therefore, an improvement example with respect to the conventional apparatus regarding the removal of additives in the present invention is shown in (1), an improvement example regarding the control of the O / U ratio is shown in (2), and Gd ₂ O
An improvement example regarding the formation of a solid solution of _3- contained UO ₂ is shown in (3). (1) Examples of Improvement Regarding Additive Removal As described above, in the conventional apparatus, when the powder compact as the object to be processed is densely loaded in the sintering container, the powder located deep in the sintering container is used. In the molded body, the additive is not sufficiently removed, the removal is rapidly performed in a high-temperature portion, cracks are observed, and some elements of the additive are taken into the sintered pellet. Therefore, it is necessary to adjust the filling rate of the object to be processed into the sintering container. However, in the present invention, when C and N, which are the main components of the additive, were analyzed and the appearance of the sintered body was observed, the results shown in the following table were obtained, and no cracks were observed even when densely packed.

[0021]

[Table 1] Note) C and N are the results after heat treatment at 750 ° C for 2 hours.
The results after sintering at 4 ° C. for 4 hours. (2) Improvement example regarding adjustment of O / U ratio An object to be processed manufactured with a powder having a high O / U ratio is converted into an O / U ratio.
If the temperature is brought to the maximum temperature while maintaining a high O / U ratio without adjusting the U ratio, the pellets are deformed or cracked due to rapid sintering or reduction. For this reason, it is necessary to adjust the filling rate of the object to be processed in the sintering container and to adjust the O / U ratio over a sufficient time, which causes a reduction in production efficiency. On the other hand, in the present invention, the O / U ratio can be adjusted in a short time without lowering the production efficiency as shown in the table below.

[0022]

[Table 2](3) Gd_TwoO_ThreeEntering UO_TwoOn solid solution formation of aluminum
Example Gd_TwoO_ThreeEntering UO_TwoWhen sintering the compact,
Of oxygen in the sintering vessel to the depth of the sintering vessel
There is a need. Gd especially added_TwoO_ThreeHigh concentration
The more oxygen content is needed. Therefore, the product in the sintering vessel
Loading capacity is Gd_TwoO _ThreeThe higher the concentration, the lower the sintering volume.
The supply to the deep part of the vessel must be sufficient. However
In the present invention, as shown in the table below,
In addition, a reduction in production efficiency was prevented.

[0023]

[Table 3]

[0024]

As described above, in the present invention, a large number of holes are formed in the side plate and the bottom plate of the sintering vessel, and the skid supporting the sintering vessel communicates from the side to the top. Since the atmosphere gas supply path is formed, the atmosphere gas flows into the sintering vessel through the above-mentioned atmosphere gas supply path and the hole of the sintering vessel bottom plate, and the supply of the atmosphere gas to the deep portion of the sintering vessel is sufficient. Done in Therefore, removal of additives from the powder compact, control of the O / U ratio, and
The solid solution molding of UO ₂ containing d ₂ O ₃ can be reliably performed, and the occurrence of cracks, reduction in density, and deformation of the sintered body can be prevented, and the productivity can be increased.

Further, since the skid moves in the furnace along the skid guide of the hearth, the skid guide portion may act as a barrier to hinder the entry of the atmospheric gas. By forming an atmosphere gas introduction hole in the guide portion, entry of the atmosphere gas can be ensured.

[Brief description of the drawings]

FIG. 1 is a sectional perspective view showing a configuration of a sintering apparatus of the present invention.

FIG. 2 is a plan view showing a schematic configuration of a continuous sintering furnace.

FIG. 3 is a sectional perspective view showing the configuration of a conventional sintering apparatus.

FIG. 4 is a side view showing a region where the supply of atmospheric gas is insufficient in a conventional supply device.

FIG. 5 is a plan view of FIG. 4;

[Explanation of symbols]

 Reference Signs List 1 sintering furnace 6 skid 7 sintering vessel 10 hearth 10a skid guide 11 powder compact 12 hole 13 long hole 14 hole 15 atmosphere gas introduction hole

Claims (2)

[Claims] 1. A sintering container for accommodating a large number of powder compacts, a large number of holes are formed in side and bottom plates, and the sintering container is placed and moved on a hearth of a sintering furnace. An apparatus for sintering a powder compact, wherein an atmosphere gas supply passage communicating from a side surface to an upper surface is formed in the skid. 2. An atmosphere gas introduction hole for introducing an atmosphere gas into a skid is formed in a skid guide portion provided on both sides of a hearth in a sintering furnace.
An apparatus for sintering a powder compact according to claim 1.