JPH0782114B2 - Dross recovery device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention collects dross such as cutting debris generated during underwater cutting of a reactor pressure vessel in nuclear reactor decommissioning. Regarding the dross recovery device.

(Prior Art) In the case of nuclear reactor decommissioning at a nuclear power generation facility, handling of a highly pressurized nuclear reactor pressure vessel (RPV) due to neutron irradiation from the core due to operation of a power plant has become a problem.

Since the reactor pressure vessel is highly activated, when disassembling by air cutting, scattering of dross such as cutting debris and the presence of radioactive fumes lead to the spread of radiation pollution and the radiation exposure to cutting workers. Volume can be an issue. For this reason, it is considered that the reactor pressure vessel is cut underwater.

By cutting the reactor pressure vessel underwater with water shielding,
It is expected that the diffusion of radioactive fumes and the scattering of dross can be prevented, and the radiation dose received by the cutting operator can be greatly reduced.

The conventional dross recovery device and its surroundings during underwater RPV cutting will be described with reference to FIG.

The dross recovery device expands upward in order to recover the water-filled cylinder 2 in which the reactor pressure vessel 1 is water-filled and the dross 7 generated when the reactor pressure vessel 1 is cut off in water. A container (dross recovery pan 6 and dross recovery hopper 5), a separator 9 for separating the recovered dross 7 from water, and the water separated by this separator 9 is returned to the water-filled cylinder 2 through a filter 10. And a circulation pump 11 for controlling the circulation.

This dross recovery device uses a dross recovery pan 6 and a dross recovery hopper 5 as radioactive dross such as cutting chips and clad generated when the reactor pressure vessel 1 is underwater cut in a water-filled water-filled cylinder 2. Collecting and suction pipe 8,
The dross 7 collected via 8a is guided to the separator 9 where the dross 7 is separated and removed from water. Separator 9
The water from which the radioactive dross 7 is removed through the filter 10 is discharged by the circulation pump 11 and returned to the water-filled cylinder 2.
Prepared for the next recovery of radioactive dross 7.

(Problems to be solved by the invention) When dismantling a reactor pressure vessel due to reactor decommissioning, what is effective in radiating dross such as cutting chips and clad generated during underwater cutting of the reactor pressure vessel? It has been a problem whether the radiation exposure of cutting workers can be further reduced.

The present invention has been made in consideration of the above circumstances, and a dross recovery device capable of effectively recovering radioactive dross generated during underwater cutting of a reactor pressure vessel and significantly reducing the radiation exposure of workers. The purpose is to provide.

[Structure of Invention]

(Means for Solving Problems) A dross recovery device according to the present invention includes a funnel-shaped dross recovery pan, a suction pipe led out from a discharge port provided at the bottom of the dross recovery pan, and the suction pipe. A dross remover connected to the circulation pump, a circulation pump connected to the dross remover, a branch pipe provided on the discharge side of the circulation pump and provided outside the suction pipe to form a double pipe. An injection pipe, a plurality of injection nozzle conduits connected to this injection pipe, an injection nozzle connected to this injection nozzle conduit and provided inside a dross recovery pan to create a swirling flow in the circumferential direction, and the dross to be discharged. It is equipped with an injection nozzle forcibly leading to the outlet.

(Function) This dross recovery device collects dross accumulated in the dross recovery pan of radioactive dross such as cutting chips and clad generated when the reactor pressure vessel is underwater cut in a water-filled water-filled cylinder.
This is effectively collected by the jet nozzles provided in the funnel-shaped dross recovery pan to make a swirling flow in the circumferential direction and the jet flow discharged from the jet nozzle forcibly guiding the dross to the discharge port.

Further, by providing the dross recovery device, when the reactor pressure vessel is underwater cut in the water-filled cylinder, the radioactive dross generated by this underwater cutting is effectively recovered and is not accumulated in the dross recovery pan. Therefore, not only the dross recovery as the secondary waste becomes easy, but also the removal of the accumulated dross becomes unnecessary, and the radiation exposure of the worker can be remarkably reduced.

(Example) Hereinafter, one example of the dross recovery device according to the present invention will be described with reference to the accompanying drawings.

1 and 2 show an embodiment of the dross recovery device according to the present invention. A funnel-shaped dross recovery pan 6A as an inner dross recovery container is installed below the cutting portion in the reactor pressure vessel 1. The dross recovery pan 6A is opened upward to recover dross such as cutting chips and clad cut by the reactor pressure vessel cutting device 3. A discharge port is formed in the lower center of the dross recovery pan 6A, and is connected to a cyclone separator as a dross remover separator through the suction pipe 8A.

In the dross recovery pan 6A of the present invention, the injection nozzles 13a, 13 are provided so as to effectively recover the dross accumulated on the dross recovery pan.
b is installed. The injection nozzle includes an injection nozzle 13a that stirs the dross and an injection nozzle 13b that forcibly guides the dross to the discharge port, and collects the dross effectively. The injection nozzle 13a for stirring the dross is installed so as to inject the dross recovery pan in the shape of a funnel substantially in the circumferential direction, and creates a swirling flow in the circumferential direction. Further, the injection nozzle 13b forcibly guiding the dross to the discharge port is installed facing the discharge port.

Further, as a firing source (water) of the injection nozzle, a part of the discharge flow of the circulation pump of the dross recovery device is used. The supply of water to the injection nozzles 13a and 13b of the dross recovery device of the present invention will be described in detail. The water branched from the downstream side of the circulation pump is guided to the injection pipe 14 in FIG. The injection pipe 14 is a double pipe at the connecting portion with the suction pipe 8A, and the suction pipe 8A is located on the central axis. A coupling 15A is provided at the tip of the injection pipe 14 together with the suction pipe 8A, and this coupling 15A and the coupling 15B on the dross recovery pan 6A side are connected. On the dross recovery pan 6A side, a plurality of injection nozzle conduits 16 are led out from the outside of the double pipe, and the tips thereof are connected to the injection nozzles 13a and 13b of the dross recovery pan 6A. The central axis side of the double pipe is directly opened to the bottom of the dross recovery pan 6A. The couplings 15A and 15B are preferably one-touch couplings.

Next, the operation of the dross recovery device will be described.

The dross 7 having the same level of radioactivity as the reactor pressure vessel 1 hardly remains on the dross recovery pan 6A, so that not only the dross as secondary waste is efficiently recovered but also cutting workers receive it. The radiation dose can be reduced. Further, when the dross recovery pan 6A is removed, the dross 7 is unlikely to accumulate on the upper part of the dross recovery pan 6A, so that the dross removing work is almost unnecessary, and the radiation dose to the worker can be significantly reduced.

〔The invention's effect〕

As described above, the dross recovery device according to the present invention promptly collects radioactive dross generated during underwater cutting of the reactor pressure vessel into the dross recovery container and guides it to the separator, where the radioactive dross is water. The radiation dose received by cutting workers can be greatly reduced because it is separated and collected.

In addition, since it is possible to prevent radioactive dross from accumulating on the upper part of the dross recovery pan, not only can dross as secondary waste be efficiently collected, but also the work of removing the radioactive dross that has fallen on the upper part of the dross recovery pan can be reduced. , The radiation dose received by workers in dross removal work can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the dross recovery device according to the present invention as seen through, FIG. 2 is a view showing a cross section of a dross recovery pan of the dross recovery device shown in FIG. 1, and FIG. FIG. 4 is a diagram showing a conventional dross recovery device. 6A ... Dross recovery pan, 8A ... Suction pipe 11 ... Circulation pump, 14 ... Injection pipe 13a, 13b ... Injection nozzle, 16a ... Injection nozzle conduit 15A, 15B ... Coupling

Claims (1)

[Claims] 1. A funnel-shaped dross recovery pan, a suction pipe led out from a discharge port provided at the bottom of the dross recovery pan, a dross remover connected to the suction pipe, and a dross remover. A circulation pump to be connected, an injection pipe branched from the discharge side of the circulation pump and provided outside the suction pipe to form a double pipe, and a plurality of injections connected to the injection pipe. A nozzle conduit, an injection nozzle that is connected to the injection nozzle conduit and is provided inside a dross recovery pan to create a swirling flow in the circumferential direction, and an injection nozzle that forcibly guides the dross to the discharge port. Dross recovery device.