JPH0226200B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drain device for a nuclear fuel bucket.

Fuel buckets are used in equipment to replace spent fuel in nuclear reactors with new fuel.

First, the outline of the reactor fuel exchange system will be explained with reference to FIG. 1. Slopes 5 and 7 are provided so as to straddle a reactor vessel 1 and a fuel storage tank 8. A fuel bucket 3 is connected to a hoisting device 4 through a chain 4a within the ramps 5, 7.

The spent fuel in the nuclear reactor 2 is held by the fuel exchange device 12 and is waiting at the position shown in the figure. On the other hand, the fuel bucket 3 is lowered by the hoisting device 4 and slides down the ramp 5 to just below the fuel exchange device 12, and the spent fuel is stored in the fuel bucket 3.

The fuel bucket 3 containing the spent fuel is lifted up into the movable slope 6 by the hoisting device 4,
Next, the movable slope 6 is swung and connected to the slope 7. In this state, the fuel bucket 3 is slid down and the spent fuel is stored in the storage tank 8.

On the other hand, new fuel stored in the storage tank 8 is stored in the fuel bucket 3 and loaded into the reactor 2 by following the same route in reverse. In this way, old and new fuel are exchanged.

Since spent fuel generates decay heat, the fuel bucket 3 is filled with sodium for cooling. Similarly, the reactor vessel 1 and the storage tank 8 are also filled with sodium for cooling.

After the fuel exchange as described above is completed, the fuel bucket 3 is pulled up into the movable ramp 6, and with the movable ramp 6 vertical, it waits until the next fuel exchange time comes.

During this waiting period, maintenance and inspection of the fuel exchange device is performed. Maintenance inspections include inspections of the fuel bucket's sodium retention function, wheels for sliding down slopes, and inspections of hoisting devices and drive parts of movable slopes.
If repairs are required as a result of the inspection, it will be necessary to move the fuel bucket out of the cell and allow work personnel to enter the cell. At this time, the sodium in the fuel bucket has a high radioactivity level, so in order to take it out of the cell or enter the cell while the sodium is still in the fuel bucket, it is necessary to
Temporary shielding provided for radiation protection of workers is extensive, and the approach distance to the fuel bucket is restricted, making repair work extremely difficult.

During standby, it is therefore required to remotely drain the sodium in the fuel bucket into the reactor vessel, storage tank or ramp. usually,
A method of draining the liquid in the container is to use a drain plug at the bottom of the container, but in fuel buckets, where high reliability is required for the cooling function of spent fuel, the plug may come loose for some reason and cause cooling problems. In the event of an unexpected leak of sodium, the fuel cooling function would be impaired, making it difficult to use a drain plug, and there was no suitable remote sodium drain method.

The present invention has been made in view of the above-mentioned circumstances, and provides a fuel bucket that allows sodium in the fuel bucket to be easily discharged in a reactor vessel, storage tank, or slope without providing a plug at the bottom of the fuel bucket. The purpose is to provide a bucket drain discharge device.

That is, the present invention provides a gas ejection nozzle parallel to the outer periphery of the tip of a siphon tube, attaches the siphon tube to a fuel bucket, and uses the ejector effect produced by ejecting gas from the gas ejection nozzle to emit fuel. The sodium in the fuel bucket is sucked up into the siphon tube, and then the sodium in the fuel bucket is discharged by the siphon effect.

The details of one embodiment of the present invention will be explained below.

In FIG. 2, reference numeral 13 denotes a gas jet nozzle attached parallel to the outer periphery of the tip of the siphon tube 15. 18 is a gas source of argon gas sealed in the reactor vessel 1, the storage tank 8, and the cell 14.
A heat-resistant flexible hose 16 connects the gas source 18 and the gas injection nozzle 13, and the gas from the gas source 18 is ejected from the gas injection nozzle 13 by operating the on-off valve 17.

In Figure 3, a fuel bucket 3 with a rectangular cross section is connected to a slope 5.
This is a diagram showing a state in which the fuel bucket cart 3 slides down, with wheels 9 guided by rails 10 provided inside a cylindrical ramp 5. The siphon pipe 15 shown in FIG. 2 is attached to this fuel bucket 3 as shown.

Next, the operation of the fuel bucket drain discharge device configured as described above will be explained. After completing the fuel exchange, the siphon pipe 15 is first attached to the fuel bucket 3 in the movable ramp 6. Next, the movable slope 6 is swung and connected to the slope 7. In this state, when the on-off valve 17 is opened and gas is ejected from the gas injection nozzle 13, the inside of the siphon tube 15 becomes negative pressure, the sodium in the fuel bucket 3 is sucked, and the inside of the siphon tube 15 is filled with sodium. When the inside of the siphon tube 15 is filled with sodium in this way, a siphon effect occurs, and even if the gas jetting from the gas jetting nozzle 13 is stopped, the sodium inside the fuel bucket 3 is discharged.

In this way, the sodium in the fuel bucket 3 discharged by the siphon effect flows down the movable ramps 6 and 7 and is recovered into the storage tank 8.

The above is a case where the sodium in the fuel bucket 3 is discharged within the movable ramp 6, but it may be slid down to near the storage tank 8 and discharged with the siphon pipe 15 attached to the fuel bucket 3.

After the sodium in the fuel bucket 3 is discharged, it is pulled up into the movable ramp 6 and waits until the next fuel change. Also, inspection and repair will be carried out during this waiting period.

As detailed above, according to the present invention, a gas injection nozzle is provided parallel to the outer periphery of the tip of a siphon tube bent into a U-shape, and gas is ejected from the gas injection nozzle while the siphon tube is attached to a fuel bucket. Since the siphon pipe is filled with sodium to obtain the siphon effect, the sodium in the fuel bucket can be easily, safely, and reliably extracted from any location such as inside the slope or inside the storage tank. This can lower the radioactivity level of workers and contribute to improving the work efficiency of workers.

Furthermore, since a siphon tube is used, there is no need to attach any accessories to the fuel bucket.
This has the effect of not impairing the functions of the fuel bucket such as cooling.

In this way, it has become possible to safely and reliably discharge the sodium in the fuel bucket at any location without impairing the function of the fuel bucket.

In addition, when the fuel bucket 3 has a structure divided into multiple compartments, by increasing the number of these siphon pipes to a plurality, the sodium accumulated in the multiple compartments can be drained with a single drain operation. , and the same effect as described above can be obtained.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view showing the entire fuel exchange device;
FIG. 2 is a side view of a siphon pipe in the fuel bucket drain discharge device of the present invention, and FIG. 3 is a plan view showing a drain discharge device in which the siphon pipe is attached to a fuel bucket in a slope. 1...Nuclear vessel, 3...Fuel bucket, 5,
7...Slope, 6...Movable slope, 8...Storage tank, 1
3... Gas ejection nozzle, 15... Siphon tube,
16...Hose, 17...Opening/closing valve, 18...Gas source.

Claims (1)

[Claims] 1. A gas jetting nozzle is provided parallel to the outer periphery of the tip of the siphon tube, and this siphon tube is attached to a fuel bucket, and gas is jetted from the gas jetting nozzle to remove sodium in the fuel bucket from the siphon tube using the ejector effect. A drain discharge device for a nuclear fuel bucket, characterized in that the sodium in the fuel bucket is sucked up into the tank and then discharged by a siphon effect.