JPS6140958B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a radioactive substance present in the primary coolant (metallic sodium) in, for example, a liquid sodium cooled fast breeder reactor (hereinafter referred to as FBR).
The present invention relates to a radioactive substance removal device that removes radionuclides such as fission products (hereinafter referred to as FP) or radioactive corrosion products (hereinafter referred to as CP) from coolant.

When a combustion pin in the furnace breaks during FBR operation, the FP generated in the combustion pin is released into the coolant. These released emission FP
is broadly classified into three types: rare gas FP, volatile FP, and nonvolatile FP. Part of the rare gas FP migrates from the upper core plenum into the cover gas, and most of the remaining gas in the coolant repeatedly disintegrates and becomes non-volatile.
It turns into FP and deposits on the inner walls of piping inside the plant. Volatile FPs such as iodine, tellurium, and cesium
is dissolved in the coolant and transferred to the cold trap, where most of it is captured and removed. Non-volatile FP is deposited on the inner wall of the pipe within the blunt shortly after being released from the fuel pin. On the other hand, reactor core structural materials, such as fuel cladding tubes (hereinafter abbreviated as structural materials), are mainly made of stainless steel, and are strongly activated when exposed to high-density neutron irradiation in the core. The main nuclides produced are Cr-51, Mn-54, Fe-59, Co-
58, Co-60, etc. The radioactive structural materials are
Corrosion caused by high-temperature liquid sodium causes CP to be released into the sodium and deposited on the inner walls of plant piping. Many of the deposited non-volatile FPs and CPs have long half-lives and emit strong γ-rays, so
It is dangerous for people to approach the equipment and piping of the primary cooling system, and maintenance and inspection work becomes difficult. especially
In FBR, the contribution of CP is larger than that of FP.

Among these deposited radionuclides, a method has been devised to reduce the subsequent transfer of CP to the plant by installing a trap device mainly made of nickel above the reactor core to capture and remove it through adsorption. . However, with this method, the adsorption capacity of the CP trap device reaches saturation after a certain period of time, and if it is immersed in sodium any longer, it may peel off and migrate to the rear of the primary cooling system. , it was necessary to replace it periodically.

The present invention was made based on the above circumstances, and it captures and removes ferromagnetic and paramagnetic FPs and CPs, and
The object of the present invention is to provide a radioactive material removal device that does not require replacement during the life of the plant.

A magnetic field is applied at a predetermined distance in the direction of flow in the short axis direction of the flat section of the flow tube, which is made of a non-magnetic material and has a flat cross section, through which a fluid of liquid metal, such as liquid sodium, containing a radioactive substance flows. a magnetic field generating section that applies a magnetic field, and a magnetic body provided on one or both sides of the flow tube where the magnetic poles of the magnetic field generating section are opposed so as to protrude above the opposing surface of the magnetic poles and not to come into contact with the opposing magnetic poles. The magnetic pole body is provided to extend along the flow direction so as not to impede the flow of fluid within the flow tube, thereby forming a plurality of gradient magnetic fields within the flow tube. It is a radioactive substance removal device, and in particular, the magnetic pole body has a plate shape that extends along the flow direction of the fluid flowing in the flow tube, and the magnetic pole body has a plate shape that extends along the flow direction of the fluid flowing in the flow tube, and the magnetic pole bodies are arranged alternately in a comb-like shape on both opposing sides of the magnetic pole. It is a radioactive material removal device installed so as not to come into contact with the
In addition, it is a radioactive material removal device in which the above gradient magnetic field is formed in the core exit piping of a liquid metal cooled fast breeder reactor, and furthermore, the cross sectional area of the flat flow tube is the cross sectional area of the primary system main piping of the liquid metal cooled fast breeder reactor. This is a radioactive substance removal device formed to have the same cross-sectional area as the pipe, and generates a magnetic field with a large gradient inside the pipe to capture and remove ferromagnetic and paramagnetic FP and CP.

The invention will be explained in detail below with reference to the drawings. 1st
The figure is a sectional view of an embodiment of the invention. The magnetic pole plates 2 made of a magnetic material are arranged in a comb pattern in the vertical direction of a rectangular pipe 1 made of a non-magnetic material having the same cross-sectional area as the primary sodium main circulation system piping so that they do not come in contact with each other alternately. Install in the direction. Large magnetic poles 4 are provided on both the upper and lower sides of the pipe 1, and a coil 5 is wound around the opposite side where the pipe is installed. coil 5
By passing a current through, the upper and lower magnetic poles 4 are strongly magnetized. Moreover, since the comb-tooth-shaped magnetic pole plates 2 are also strongly magnetized, a large magnetic field gradient is generated between the vertical magnetic pole plates 2. The ferromagnetic and paramagnetic FP and CP flowing in the coolant 3 are strongly attracted to the magnetic pole plate 2 and attracted onto the magnetic pole plate 2.
Since the FP and CP attracted onto the magnetic pole plate 2 are attracted by strong magnetic force, they are not detached by the flow of the coolant. Further, by arranging the magnetic pole plates 2 more closely, the magnetic field gradient can be further increased, and the attractive force is increased.

As mentioned above, the present invention allows the device to serve as a trap for FPs and CPs without having to be replaced during the life of the plant. Furthermore, if the flow of the coolant is disturbed and the chances of it colliding with the magnetic pole plates of the FP and CP are increased, the capture and removal efficiency will be further increased. In particular, many CPs are ferromagnetic, so the effect is tremendous.

Note that the present invention is not limited to the above embodiments. For example, as shown in FIG. 2, a comb-toothed magnetic pole plate 2 may be provided only on one side. Alternatively, the magnetic pole plates 2 may be arranged in a corrugated manner with respect to the coolant flow 6, as shown in FIG. 3, instead of disposing the magnetic pole plates parallel to the flow of the coolant. By doing so, the chances of the FP and CP present in the coolant colliding with the magnetic pole plate 2 are increased, and the capture and removal efficiency is increased.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view showing one embodiment of the present invention, FIG. 2 is a partially cutaway front view showing only the coolant piping section of one embodiment of the present invention, and FIG. FIG. 2 is a partially cutaway top view showing only the coolant piping section of one embodiment. 1... Rectangular primary cooling system piping, 2... Magnetic pole plate,
3... Coolant (sodium), 4... Magnetic pole, 5...
...Coil, 6... Sodium flow.

Claims (1)

[Scope of Claims] 1. A flow tube with a flat cross section made of a non-magnetic material and through which a liquid metal fluid containing a radioactive substance flows, and a predetermined distance in the short axis direction of the flat portion of the flow tube in the flow direction. a magnetic field generating section for applying a magnetic field, and a magnetic field generating section whose magnetic poles protrude onto one or both opposing sides of the flow tube so as not to come into contact with the opposing magnetic poles. A magnetic pole body made of a magnetic material is provided, and the magnetic pole body is provided so as to extend along the flow direction so as not to impede the flow of fluid within the flow tube, thereby generating a plurality of gradient magnetic fields within the flow tube. A radioactive substance removal device characterized by being formed by forming. 2. The magnetic pole bodies are plate-shaped so as to extend along the flow direction of the fluid flowing in the flow tube, and are provided on both opposing sides of the magnetic poles in a comb-like manner so as not to come into contact with each other alternately. A radioactive substance removal device according to claim 1. 3. The radioactive substance removal device according to claim 1, wherein the magnetic pole body is a plate-shaped body formed in a corrugated shape along the flow direction of the fluid flowing in the flow tube. 4. The radioactive material removal device according to claim 1, wherein a gradient magnetic field is formed in a core exit pipe of a liquid metal cooled fast breeder reactor. 5. The radioactive material removal device according to claim 4, wherein the flat flow tube is formed to have the same cross-sectional area as the cross-sectional area of the primary system main piping of a liquid metal cooled fast breeder reactor. 6. The radioactive substance removal device according to claim 1, wherein the liquid metal is liquid sodium.