Patent Description:
As fossil energy is depleted worldwide, nuclear power generation is being used as a major energy source. In such nuclear power generation, a generally-used pressurized water reactor (PWR) nuclear power plant consists of a primary system circulating through a nuclear reactor, a secondary system circulating through a steam generator, and a tertiary system circulating through a condenser. Specifically, in the primary system, pressure is applied to a coolant in a reactor to maintain a pressure of <NUM> atm and <NUM>, and in the secondary system, the coolant passes through tubes of a steam generator and boils water of the steam generator side to generate steam to turn a turbine. In the tertiary system, the steam turns the turbine, and then passes through the condenser and becomes water again and is sent to the steam generator.

Since the reactor of such a pressurized water reactor type of nuclear power plant is contaminated with radioactivity, when the reactor is cut and dismantled, radioactive dust such as aerosol and slag may diffuse and contaminate peripheral devices.

Document <CIT> discloses a disjointing method of the furnace inside structure and the reactor vessel for simultaneously tearing down the reactor vessel and furnace inside structure. Document <CIT> discloses a tank removal method applied, for example, dismantling or removing an existing fuel replacement water tank of a nuclear power plant. Document <CIT> discloses a nuclear waste double block structure.

The present embodiment relates to a nuclear reactor decommissioning system that may prevent contamination of peripheral devices by radioactive dust generated during a decommissioning process thereof.

A nuclear reactor decommissioning system according to an embodiment includes: a cutting device to cut a reactor, a lifting device inserted inside the reactor to lift the reactor, and a shielding device that is positioned between the reactor and the lifting device and blocks radioactive dust generated by the cutting device from spreading.

The lifting device may include a coupling member coupled to the reactor, and an elevating device that is connected to the coupling member and elevates the reactor, and the shielding device may include a shielding tube including a plurality of cylindrical members of different diameters surrounding the elevating device, and a shielding plate positioned on an upper portion of the shielding tube and blocking the reactor from the outside.

The plurality of cylindrical members may have a larger diameter as a distance from the elevating device increases, and respective end portions of the cylindrical member may have catching projections to be caught by respective end portions of adjacent cylindrical member.

The catching projection may include an outer catching projection extending from the cylindrical member to the outside, and an inner catching projection extending from the cylindrical member to the inside.

When the reactor is lifted by the lifting device, at least some of the cylindrical members of the shielding tube may be lifted together.

The shielding plate may include a plurality of ventilation parts positioned between the reactor and the outermost cylindrical member of the shielding tube.

The plurality of ventilation parts may be formed along an edge of the shielding plate.

A dust collecting device connected to the plurality of ventilation parts to collect the radioactive dust may be further included.

According to the embodiment, it is possible to easily adjust a length of a shielding device according to a cutting process of a reactor, by installing a length-adjustable shielding device between the reactor and a lifting device. Therefore, diffusion of radioactive dust generated by a cutting device for cutting the reactor may be easily blocked.

In addition, it is possible to minimize radioactive dust from contaminating a peripheral device or being exposed to a worker, by intensively collecting the radioactive dust through a ventilation part formed on a shielding plate.

The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. As those skilled in the art would realize, the described embodiment may be modified in various different ways, all without departing from the scope of the present invention.

In order to clearly describe the present invention, parts that are irrelevant to the description are omitted, and identical or similar constituent elements throughout the specification are denoted by the same reference numerals.

Further, in the drawings, the size and thickness of each element are arbitrarily illustrated for ease of description, and the present disclosure is not necessarily limited to those illustrated in the drawings.

<FIG> illustrates a cross-sectional view of a nuclear reactor decommissioning system according to an embodiment, <FIG> illustrates an enlarged cross-sectional view of one cylindrical member of <FIG>, and <FIG> illustrates a cross-sectional view of a nuclear reactor decommissioning system according to an embodiment.

As shown in <FIG>, a nuclear reactor decommissioning system according to an embodiment includes a cutting device <NUM> for cutting a reactor <NUM>, a lifting device <NUM> for lifting the reactor <NUM>, a shielding device <NUM> for blocking diffusion of radioactive dust <NUM> generated while cutting the reactor <NUM>, a dust blocking device <NUM> for blocking bioprotective concrete <NUM> surrounding the reactor <NUM> from the outside, and a dust collecting device <NUM> for collecting the radioactive dust <NUM>.

The cutting device <NUM> may include a thermal cutting device, a mechanical cutting device such as a wire saw, or an electrical cutting device such as a laser. However, the cutting device is not limited thereto, and various devices that may cut the reactor are applicable thereto.

The lifting device <NUM> may be inserted into the reactor <NUM> to lift the reactor <NUM>. The lifting device <NUM> may include a coupling member <NUM> coupled to a coupling protrusion 200a to be protruded inside the reactor <NUM>, and an elevating device <NUM> connected to the coupling member <NUM> and lifting the reactor <NUM>.

The coupling member <NUM> has a disk-like shape. However, it is not limited thereto, and various shapes that may be inserted inside the reactor <NUM> to be combined with the reactor <NUM> are applicable.

The elevating device <NUM> may have a rod-like shape that is connected to a central portion of the disk-shaped coupling member <NUM> to lift the coupling member <NUM> together.

The shielding device <NUM> is positioned between the reactor <NUM> and the lifting device <NUM> to be able to block the diffusion of the radioactive dust <NUM> generated by the cutting device <NUM> that cuts an upper end portion <NUM> of the reactor <NUM>. The shielding device <NUM> may include a shielding tube <NUM> including a plurality of cylindrical members 21a, 21b, 21c, 21d, 21e, and 21f of different diameters surrounding the elevating device <NUM>, and a shielding plate <NUM> positioned on an upper portion of the shielding tube <NUM> and blocking the reactor <NUM> from the outside.

In the present embodiment, the shielding tube <NUM> is shown as consisting of six cylindrical members 21a, 21b, 21c, 21d, 21e, and 21f, but is not limited thereto, and it may be configured of cylindrical members in various numbers.

A plurality of cylindrical members 21a, 21b, 21c, 21d, 21e, and 21f forming the shielding tube <NUM> may have a larger diameter as a distance from the elevating device <NUM> increases. Accordingly, as shown in <FIG>, the shielding tube <NUM> may have a stepped shape as a whole when it is not in contact with the elevating device <NUM> of the lifting device <NUM>.

As shown in <FIG> and <FIG>, respective end portions of the cylindrical members 21a, 21b, 21c, 21d, 21e, and 21f may have a catching projection <NUM> to be locked to respective end portions of adjacent cylindrical members 21a, 21b, 21c, 21d, 21e, and 21f. In <FIG>, one cylindrical member 21b will be mainly described in detail. As shown in <FIG>, the catching projection <NUM> may include an outer catching projection <NUM> extending from the cylindrical member 21b to the outside, and an inner catching projection <NUM> extending from the cylindrical member 21b to the inside. In the present embodiment, the outer catching projection <NUM> may be positioned at an upper end portion of the cylindrical member 21b, and the inner catching projection <NUM> may be positioned at a lower end portion of the cylindrical member 21b, based on a direction of gravity.

Therefore, as shown in <FIG>, the inner catching projection <NUM> and the outer catching projection <NUM> of the adjacent cylindrical members 21a, 21b, 21c, 21d, 21e, and 21f contact each other, so that the shielding tube <NUM> has a entirely step shape by gravity.

Therefore, even if the reactor <NUM> is cut by using the cutting device <NUM>, the shielding device <NUM> may block the radioactive dust <NUM> such as slag, fume gas, and aerosol from contaminating the lifting device <NUM>.

<FIG> illustrates a cross-sectional view of one step of decommissioning a reactor using a nuclear reactor decommissioning system according to an embodiment, and <FIG> illustrates a cross-sectional view of a step after that of <FIG>.

As shown in <FIG>, when the reactor <NUM> is lifted by using the lifting device <NUM> in order to cut a middle portion <NUM> of the reactor <NUM> by using the cutting device <NUM>, at least some of the cylindrical members 21a, 21b, 21c, 21d, 21e, and 21f of the shielding tube <NUM> are lifted together. That is, some (21a, 21b, and 21c) of the cylindrical members contacting the coupling member <NUM> of the lifting device <NUM> are lifted together with the lifting device <NUM>. Therefore, some (21a, 21b, and 21c) of the cylindrical members overlap each other, so that a length of the shielding tube <NUM> may be shortened.

That is, in <FIG>, the length of the shielding tube <NUM> has a length of L1, but as shown in <FIG>, when the reactor <NUM> is lifted, the length of the shielding tube <NUM> may have a length of L2 that is smaller than L1.

In this case, the cylindrical members 21a, 21b, 21c, 21d, 21e, and 21f of the shielding tube <NUM> are sequentially lifted together with the elevating device <NUM> from the cylindrical member closest to the elevating device <NUM>. That is, as shown in <FIG>, the three cylindrical members 21a, 21b, and 21c closest to the elevating device <NUM> among the six cylindrical members are first lifted to overlap each other. However, it is not limited thereto, and various numbers of cylindrical members may overlap each other depending on an elevation height of the reactor <NUM>.

In addition, as shown in <FIG>, when the reactor <NUM> is further lifted to cut a lower end portion <NUM> of the reactor <NUM>, all of the cylindrical members 21a, 21b, 21c, 21d, 21e, and 21f forming the shielding tube <NUM> overlap each other. Therefore, a length L3 of the shielding tube <NUM> further decreases.

As such, in the case of cutting from the upper end portion to the lower end portion of the reactor <NUM> while lifting the reactor <NUM>, since the length of the shielding device <NUM> that blocks the elevating device <NUM> from the radioactive dust <NUM> may also be shortened, the shielding device <NUM> may be easily inserted between the elevating device <NUM> and the reactor <NUM>.

The shielding plate <NUM> may include a plurality of ventilation parts 30a positioned between the reactor <NUM> and the outermost cylindrical member 21f of the shielding tube <NUM>. As shown in <FIG>, the plurality of ventilation parts 30a may be formed along an edge of the shielding plate <NUM>. The shielding plate <NUM> may be rotated around the elevating device <NUM> as a central axis. Accordingly, since a position of the ventilation part 30a may be adjusted, the radioactive dust <NUM> may be effectively collected by adjusting the position of the ventilation part 30a according to an amount of the radioactive dust <NUM>.

The dust blocking device <NUM> may block the bioprotective concrete <NUM> surrounding the reactor <NUM> from the outside.

The dust collecting device <NUM> may be connected to the plurality of ventilation parts 30a to collect the radioactive dust <NUM> collected through the ventilation parts 30a. In the present embodiment, the dust collecting device <NUM> is installed on the shielding plate <NUM>, but is not limited thereto, and may be installed at various positions.

Therefore, it is possible to minimize the radioactive dust <NUM> from contaminating peripheral devices or being exposed to workers, by intensively collecting the radioactive dust <NUM> through the ventilation parts 30a formed on the shielding plate <NUM>.

Claim 1:
A nuclear reactor decommissioning system, comprising
a cutting device (<NUM>) to cut a reactor (<NUM>),
a lifting device (<NUM>) inserted inside the reactor (<NUM>) adapted to lift the reactor (<NUM>), which lifting device (<NUM>) includes
a coupling member (<NUM>) coupled to the reactor, and
an elevating device (<NUM>) that is connected to the coupling member (<NUM>) and elevates the reactor (<NUM>),
and
a shielding device (<NUM>) that is positioned between the reactor (<NUM>) and the lifting device (<NUM>) and blocks radioactive dust generated by the cutting device (<NUM>) from spreading
and the shielding device (<NUM>) includes
a shielding tube (<NUM>) including a plurality of cylindrical members (21a, 21b, 21c, 21d, 21e, 21f) of different diameters surrounding the elevating device (<NUM>) and
a shielding plate (<NUM>) positioned on an upper portion of the shielding tube (<NUM>) and blocking the reactor (<NUM>) from the outside.