JP2926009B2 - Nuclear fuel pellet sintering equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear fuel pellet sintering apparatus, and more particularly to a nuclear fuel pellet sintering apparatus which removes fine dust adhering to an adjustment valve for adjusting a pressure in a sintering furnace.

[0002]

2. Description of the Related Art In general, nuclear fuel pellets are produced by pressing a nuclear fuel powder such as uranium dioxide (UO2), followed by sintering.

FIG. 7 is a view showing a schematic configuration of a nuclear fuel pellet sintering apparatus for sintering the above-mentioned press-formed nuclear fuel pellets. The nuclear fuel pellet sintering apparatus 10 includes a sintering furnace 12 having a pressure relief valve 11. Is provided.

[0004] Hydrogen gas, which is a reducing atmosphere, is continuously supplied to the sintering furnace 12 through a gas supply port 13 connected to a gas supply source (not shown). The hydrogen gas supplied to the sintering furnace 12 by controlling the valve 15 is supplied at a constant pressure (generally 0.02K).
(positive pressure of gf / cm2 or less) to prevent air from entering the sintering furnace 12 and prevent hydrogen gas and oxygen from mixing and causing an explosion.

[0005] As shown in FIG.
A gate element 19 of a gate valve or a globe valve is provided inside the
This moves up and down by rotating a handle 20 provided outside.

The outer periphery of the valve body 19 is formed so as to be in sliding contact with a valve seat surface 21 in the body 18, and the size of the exhaust passage is reduced by the valve body 19 moving up and down with respect to the valve seat surface 21. Adjustments are made.

Reference numeral 22 denotes a pressure gauge for an operator to monitor the pressure in the sintering furnace 12.

[0008]

In order to sinter the nuclear fuel pellets pressed by the nuclear fuel pellet sintering apparatus 10 as described above, a hydrogen gas as a reducing atmosphere is continuously supplied from a gas supply port 13 to a sintering furnace 12. To supply a fixed amount.

At this time, the handle 20 is rotated to adjust the adjustment valve 15.
By moving the valve body 19 up and down to adjust the displacement, the pressure inside the sintering furnace 12 is too low to be negative pressure so that the atmosphere does not enter the sintering furnace 12 and a pressure higher than necessary (for example,
0.03 kgf / cm2 or more).

Therefore, the sintering furnace 12 filled with hydrogen gas as described above is heated to a high temperature of 1600 ° C. or more to sinter the pelletized nuclear fuel pellets.

By the way, during press molding of nuclear fuel powder, the nuclear fuel powder should be stearinized to improve the slip between the die of the molding machine and the uranium dioxide powder and to prevent the nuclear fuel powder from sticking to the die and generating cracks or the like in the molded product. A lubricant such as zinc acid is mixed.

This lubricant is thermally decomposed by the high temperature heat during the sintering, separated into saturated fatty acid and metallic zinc and evaporated,
The hydrogen gas supplied to the sintering furnace 12 is exhausted from the exhaust pipe 14 to the outside of the sintering furnace 12 via the regulating valve 15.

However, in the exhausting process, these saturated fatty acids and the like are gradually cooled and condensed to become fine dust, which adheres to the valve element 19 of the regulating valve 15 which is a particularly narrow exhaust passage, and gradually closes the exhaust passage, thereby increasing the pressure in the furnace. May rise.

The adhesion of the saturated fatty acid or the like is detected by an increase in the pressure of the pressure gauge 22, and when this state is reached, the operator vibrates the adjusting valve 15 with a hammer to shake off the dust and remove it. I have.

However, this method has a problem that the operation becomes very complicated since the pressure gauge 22 is constantly monitored and the operator must vibrate with a hammer to remove dust every time the pressure increases.

Further, when dust adheres to the regulating valve 15, the pressure in the furnace of the sintering furnace 12 increases. However, when the dust is removed, the pressure in the furnace rapidly decreases, and a considerably skilled operator is required. Otherwise, there is a problem that the adjustment valve 15 cannot be adjusted accurately.

In addition, even if such complicated operations and adjustments are performed, the dust may remain in the exhaust passage and eventually block the exhaust passage, making it impossible to adjust the adjustment valve. In some cases, there is a problem that the adjusting valve 15 needs to be disassembled and cleaned, so that more work is required.

Accordingly, an object of the present invention is to provide a nuclear fuel pellet sintering apparatus which simply and surely removes dust adhering to a regulating valve in order to solve the above-mentioned problems. It is.

[0019]

SUMMARY OF THE INVENTION The present invention provides a sintering furnace for sintering pellets formed by press-molding nuclear fuel powder in a reducing atmosphere at a predetermined pressure, and an exhaust pipe connected to the sintering furnace. A pressure detector for detecting the internal pressure of the sintering furnace, in a nuclear fuel pellet sintering apparatus having a regulating valve that adjusts the internal pressure of the sintering furnace and is always open during the operation of the sintering furnace; When the pressure detector detects an increase in the internal pressure of the sintering furnace, a control circuit that generates an intermittent signal based on the detected signal, a solenoid valve that controls intermittent opening and closing based on the intermittent signal of the control circuit, and an intermittent opening and closing of the solenoid valve An injection nozzle for injecting intermittent injection gas is provided at a sliding portion between the valve body of the adjustment valve and the valve seat by control.

[0020]

Furthermore, the present invention is characterized in that the injection nozzle is provided with a plurality of injection holes.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the nuclear fuel pellet sintering apparatus of the present invention will be described below with reference to the drawings.

Since the nuclear fuel pellet sintering apparatus 30 of the present invention is basically the same as the conventional nuclear fuel pellet sintering apparatus 10, the same parts are denoted by the same reference numerals and will not be described in detail.

A pressure detector 31 is attached to the gas supply port 13 so as to detect the pressure inside the sintering furnace 12. A control circuit 32 having a timer is connected to the pressure detector 31, and outputs an intermittent pressure control signal when the pressure in the sintering furnace 12 exceeds a predetermined positive pressure. ing.

An electromagnetic valve 33 connected to a nitrogen gas supply source (not shown) is connected to the control circuit 32. The solenoid valve 33 is opened and closed for a certain period of time in response to a pressure control signal so as to perform intermittent opening and closing.

An injection nozzle 34 is connected to the solenoid valve 33, and the injection nozzle 34 is connected to the body 1 of the regulating valve 15.
8 is screwed obliquely, and nitrogen gas is injected from the injection nozzle 34 toward the valve seat surface 21 of the valve body 19.

The injection nozzle 34 has three injection holes 35a, 35b and 35c as shown in FIGS. 3 and 4, and nitrogen gas is injected around the exhaust passage formed by the valve element 19. , 5 and 6, a large number of injection holes 36a, 36b, 36c.
Nitrogen gas is injected over the entire surface of the.

The operation of the nuclear fuel pellet sintering apparatus 30 according to the present invention will be described.

The sintering furnace 12 is connected to a reducing atmosphere of hydrogen gas and supplied in a constant amount (7 m ³ / Hr).

At this time, the sintering furnace 12 is
While monitoring the furnace pressure, the regulating valve 15 is adjusted to maintain the furnace pressure at a constant value (for example, 0.008 kgf / cm2).

Next, the sintering furnace 12 is heated to a high temperature of 1600 ° C. or more to sinter the nuclear fuel pellets supplied into the sintering furnace 12 to form a sintered body.

At the time of this sintering, the lubricant mixed with the nuclear fuel pellets is thermally decomposed into saturated fatty acids and metallic zinc and evaporates.

The evaporated saturated fatty acid and metallic zinc are exhausted together with hydrogen gas through an exhaust pipe 14 and a regulating valve 15.

In the exhausting process, the vapor of the saturated fatty acid and the metallic zinc is gradually cooled while passing through the exhaust pipe 14 and the regulating valve 15, and forms fine dust in the hydrogen gas. The dust adheres to the valve body 19 of the regulating valve 15 where the exhaust temperature drops rapidly, narrows the exhaust passage, and increases the pressure inside the sintering furnace 12.

Such a rising pressure is detected by the pressure detector 31, and the pressure in the furnace is, for example, 0.01 kgf / cm2.
When the above operation is completed, the control circuit 32 is operated, and the timer is intermittently driven. For example, a pressure control signal that repeats the operation of driving the solenoid valve 33 for 1 second and stopping it for 3 seconds is output to the solenoid valve 3.
3 to control the opening and closing of the solenoid valve 33.

By controlling the opening and closing of the solenoid valve 33, nitrogen gas from the nitrogen gas supply source (nitrogen gas pressure: 1.0 kgf / cm 2)
Is supplied to the injection nozzle 34, and the nitrogen gas supplied to the injection nozzle 34 is intermittently injected toward the dust adhering portion of the valve body 19.

Therefore, dust is blown off by the gas injection, and the blown-down dust is exhausted to the outside of the sintering furnace 12 through the exhaust pipe 14.

By these operations, dust adhering to the regulating valve 15 is constantly removed, and the sintering furnace 12 can be maintained at a predetermined positive pressure to perform a safe operation.

As soon as dust adheres to the valve body 19 and the furnace pressure rises, the pressure detector 31 immediately detects this and removes it.
Need not be adjusted each time.

In addition, complicated operations such as applying a vibration by a hammer and cleaning an adjusting valve, which are conventionally performed, are eliminated, and the sintering furnace can be stably operated for a long period of time.

[0041]

According to the present invention, there is provided a sintering furnace for sintering pellets formed by press-molding nuclear fuel powder in a reducing atmosphere at a predetermined pressure, and a sintering furnace attached to an exhaust pipe connected to the sintering furnace. A pressure detector for detecting the internal pressure of the sintering furnace in a nuclear fuel pellet sintering apparatus having a regulating valve that regulates the internal pressure of the furnace and is always open during the operation of the sintering furnace; Detects an increase in the internal pressure of the sintering furnace, generates a control signal based on the detected signal, a control valve that controls the control of the control circuit based on the control signal, and a control valve that controls the control of the control valve. An injection nozzle for injecting intermittent injection gas is provided at the sliding contact portion between the valve body and the valve seat, so that when the pressure in the sintering furnace increases, the injection nozzle intermittently injects a detection signal detected by a pressure detector. Gas generating valve It is possible to maintain stable operation at all times at a predetermined pressure sintering furnace forcibly remove dust adhering to the valve seat and.

[0042]

Further, when the injection nozzle of the present invention is provided with a plurality of injection holes, dust adhering to the regulating valve can be completely eliminated.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an outline of a nuclear fuel pellet sintering apparatus of the present invention.

FIG. 2 is an enlarged explanatory view showing a cross section of a part near an adjustment valve to which an injection nozzle is attached.

FIG. 3 is a sectional view of a first injection nozzle.

FIG. 4 is a front view of a first injection nozzle shown in FIG. 3;

FIG. 5 is a sectional view of a second injection nozzle.

FIG. 6 is a front view of a second injection nozzle shown in FIG. 5;

FIG. 7 is an explanatory view showing an outline of a conventional nuclear fuel pellet sintering apparatus.

FIG. 8 is an enlarged explanatory view showing a part in the vicinity of the adjustment valve of FIG. 7 in a cross section.

[Explanation of symbols]

 Reference Signs List 10, 30 Nuclear fuel pellet sintering device 11 Pressure relief valve 12 Sintering furnace 13 Gas supply port 14 Exhaust pipe 15 Adjustment valve 17 Exhaust device 18 Body 19 Valve body 20 Handle 21 Valve seat surface 22 Pressure gauge 31 Pressure detector 32 Control circuit 33 Solenoid valve 34 Injection nozzle

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G21C 21/02

Claims (2)

(57) [Claims] 1. A sintering furnace for sintering pellets formed by press-molding nuclear fuel powder in a reducing atmosphere at a predetermined pressure, and an interior of the sintering furnace attached to an exhaust pipe connected to the sintering furnace. In a nuclear fuel pellet sintering device equipped with a regulating valve that regulates pressure and is always open during the operation of the sintering furnace, a pressure detector that detects the internal pressure of the sintering furnace, and the pressure detector A control circuit that generates an intermittent signal based on the detection signal when a rise in the internal pressure of the furnace is detected; a solenoid valve that controls intermittent opening and closing based on the intermittent signal of the control circuit; An injection nozzle for injecting an intermittent injection gas into a sliding contact portion between the nuclear fuel pellet and the valve seat. 2. The nuclear fuel pellet sintering apparatus according to claim 1, wherein the injection nozzle is provided with a plurality of injection holes.