Patent Description:
Core cooling, decay waste heat and containment cooling of a conventional active nuclear power plant all rely on external power sources. When the entire nuclear power plant is powered off, the above-mentioned heat cannot be conducted out of the containment, which may lead to serious safety accidents. After the Fukushima nuclear accident, passive containment heat removal systems have been extensively studied and applied.

A passive containment heat removal system includes evaporator, condenser, cooling water tank, rising tube, dropping tube and gas collector. As the core equipment of the system, the condenser plays a key role in the realization of the system's function.

A conventional passive condenser adopts a tube bundle-tube sheet-spherical head structure, which requires the heat exchange tube and the tube sheet to be welded and swelled one by one after the tube sheet is drilled. After welding, surface welding seam is non-destructively tested one by one. The spherical head is welded to the tube sheet and in order to facilitate the subsequent maintenance, a manhole must be provided on the spherical head. Tube sheets and spherical heads are often thick, so as to meet the strength requirements. Generally, six circumferential welds are required. Tube sheets and the spherical heads are processed by forgings, which makes the processing technology more complicated and expensive. After the heat exchange tube and the tube sheet are welded, <NUM>% radiographic inspection cannot be carried out. In addition, the spherical head defines a large opening, the flange seal is easy to leak, and there is a sudden change in force.

In view of the foregoing, what is needed therefore is to provide a passive condenser for a nuclear power plant which can make the opening of the containment as small as possible, can ensure the integrity of the containment to the greatest extent, and can perform <NUM>% radiographic inspection.

One object of the present invention is to overcome the disadvantages of the prior art and provide a passive condenser for a nuclear power plant which can make the opening of the containment as small as possible, can ensure the integrity of the containment to the greatest extent, and can perform <NUM>% radiographic inspection.

A nuclear power plant according to the invention comprises the features of claim <NUM>.

According to one aspect of the present invention, the first flanges are welded to the upper collecting tube in a saddle way, and the second flanges are welded to the lower collecting tube in a saddle way.

According to one aspect of the present invention, the upper inclined section is fixedly connected to the first flange by butt welding, and the the lower inclined section is fixedly connected to the second flange by butt welding.

According to one aspect of the present invention, the upper collecting tube and the lower collecting tube each has a cylindrical structure.

According to one aspect of the present invention, the first connector and the second connector each has a large head and a small head.

According to one aspect of the present invention, the heat exchange tube bundle is a C-shaped vertical heat exchange tube bundle.

According to one aspect of the present invention, an angle between the upper inclined section of the heat exchange tube and a horizontal plane is <NUM>-<NUM> degree, and an angle between the lower inclined section of the heat exchange tube and the horizontal plane is <NUM>-<NUM> degree.

According to one aspect of the present invention, the passive condenser further includes a frame assembly for supporting and fixing the upper collecting tube and the lower collecting tube.

According to one aspect of the present invention, the frame assembly is welded with a tube bundle support assembly for fixing and supporting the upper inclined section and the lower inclined section of the heat exchange tube bundle, respectively.

According to one aspect of the present invention, the closed structure of the upper collecting tube and the lower collecting tube is a welded hemispherical head.

According to one aspect of the present invention, the middle connecting section is a vertical section.

Compared with the prior art, the passive condenser for a nuclear power plant of the present invention has the following advantages:.

The passive condenser for a nuclear power plant of the present invention will be described in detail below with reference to the accompanying drawings, in which:.

In order to make the objective, technical solutions and effects of the present invention clearer, the present invention will be further described in detail below in conjunction with accompanying drawings and embodiments. It should be understood that the embodiments described herein are only for explaining the present invention, not for limiting the scope of the present invention.

Referring to <FIG>, a passive condenser for a nuclear power plant according to one embodiment of the present invention includes:.

The upper collecting tube <NUM> is a cylindrical steel tube fixed on the frame assembly <NUM>. The upper collecting tube <NUM> is evenly provided with a number of heat exchange tube steam inlets <NUM>. The upper collecting tube <NUM> passes through the openings in the upper part of the containment <NUM>. The opening on the upper part of the containment <NUM> matches the outer diameter of the upper collecting tube <NUM>, and the outer diameter of the upper collecting tube <NUM> can be adjusted according to different requirements. The inlet end of the upper collecting tube <NUM> is welded and fixed with a first connector <NUM> used for a reducing diameter. The first connector <NUM> has a small head and a large head. The outer diameter of the inlet end is smaller than the outer diameter of the connecting end of the upper collecting tube <NUM>. By using the first connector <NUM>, it can be quickly connected and fixed with adjacent equipment.

The other end of the upper collecting tube <NUM> has a closed structure. In the embodiment as illustrated, the other end is welded with a hemispherical head <NUM> matching the outer diameter of the upper collecting tube <NUM> for sealing. The upper collecting tube <NUM>, the first connector <NUM> and the hemispherical head <NUM> are welded and fixed.

The structure of the lower collecting tube <NUM> has almost the same structure as that of the upper collecting tube <NUM>. The lower collecting tube <NUM> is a cylindrical steel tube whose outer diameter can be adjusted according to the requirements of the nuclear power plant. The lower collecting tube <NUM> is evenly provided with a number of heat exchange pipe condensate return ports (not shown). In order to facilitate the fixed connection of the heat exchange tube <NUM> with the upper collecting tube <NUM> and the lower collecting tube <NUM>, the number and position of the heat exchange tube condensate return ports on the lower collecting tube <NUM> correspond to the number and position of the heat exchange tube steam inlets <NUM>.

The lower collecting tube <NUM> extends through an opening at the lower part of the containment <NUM>, and the opening at the lower part of the containment <NUM> matches the outer diameter of the lower collecting tube <NUM>. The outlet end of the lower collecting tube <NUM> is welded and fixed with a second connector <NUM> used for reducing diameter. The second connector <NUM> has a small head and a large head. The outer diameter of the outlet end is smaller than the outer diameter of the connecting end of the lower collecting tube <NUM>. By using the second connector <NUM>, the lower collecting tube <NUM> can be quickly connect and fix with adjacent equipment.

The other end of the lower collecting tube <NUM> has a closed structure. In the embodiment as illustrated, the other end is welded with a hemispherical head <NUM> matching the outer diameter of the lower collecting tube <NUM> for sealing.

According to the present invention, the upper collecting tube <NUM> and the lower collecting tube <NUM> have a cylindrical structure, with fewer circumferential welds, simpler and more reliable processing technology, and remarkably reduced manufacturing costs. The upper collecting tube <NUM> can effectively buffer and evenly distribute a large amount of inflowing steam. The lower collecting tube <NUM> can effectively collect and buffer the condensate, and discharge the condensate from the outlet end. Due to the simple cylindrical structures of the upper collecting tube <NUM> and the lower collecting tube <NUM>, the opening of the containment <NUM> can be minimized, so as to ensure the integrity of the containment <NUM> to the utmost extent.

Referring to <FIG> and <FIG>, to ensure the connection strength of the upper collecting tube <NUM> and the heat exchange tube <NUM>, and to ensure that <NUM>% radiographic inspection can be carried out, the first heat exchange tube steam inlet <NUM> of the upper collecting tube <NUM> is welded with the first flange <NUM>. The first flange <NUM> defines first through holes <NUM> having the same diameter as that of the heat exchange tube steam inlet <NUM> and communicating with the heat exchange tube steam inlet <NUM>. The first flange <NUM> is welded to the upper collecting tube <NUM> in a saddle manner, and the first flange <NUM> is parallel to the upper inclined section <NUM> of the heat exchange tube <NUM> after welding. The end of the first flange <NUM> away from the upper collecting tube <NUM> is trimmed, that is, the outer diameter of the end of the first flange <NUM> away from the upper collecting tube <NUM> is smaller than the outer diameter of the welding end with the upper collecting tube <NUM>. In order to facilitate welding with the heat exchange tube bundle, the first flange <NUM> has a certain length, and the first flange <NUM> and the upper inclined section <NUM> of the heat exchange tube <NUM> are welded by butt welding.

In order to ensure the connection strength between the lower collecting tube <NUM> and the heat exchange tube <NUM>, and to ensure that <NUM>% radiographic inspection can be performed, a second flange <NUM> is welded to the heat exchange tube condensate return port (not shown) on the lower collecting tube <NUM>. The second flange <NUM> defines second through holes having the same diameter as that of the heat exchange tube condensate return port (not shown) and communicating with the heat exchange tube condensate return port. The second flange <NUM> and the lower collecting tube <NUM> are also welded in a saddle manner, and the second flange <NUM> is parallel to the lower inclined section <NUM> of the heat exchange tube <NUM> after welding. The end of the second flange <NUM> away from the lower collecting tube <NUM> is trimmed, that is, the outer diameter of the end of the second flange <NUM> away from the lower collecting tube <NUM> is smaller than the outer diameter of the welding end with the lower collecting tube <NUM>. In order to facilitate welding with the heat exchange tube bundle, the second flange <NUM> has a certain length, and the second flange <NUM> and the lower inclined section <NUM> of the heat exchange tube <NUM> are welded by butt welding.

The first flange <NUM> and the upper collecting tube <NUM> are welded in a saddle manner, the heat exchange tube <NUM> and the first flange <NUM> are butt welded, the second flange <NUM> and the lower collecting tube <NUM> are welded in a saddle manner, and the heat exchange tube <NUM> and the second flange <NUM> are butt welded. All of the welds can be subjected to <NUM>% radiographic inspection, which improves the safety performance of the equipment.

The first connector <NUM> and the second connector <NUM> each have a large head and a small head. The existing standard parts can be directly welded and fixed to the adjacent upper collecting tube <NUM> and the lower collecting tube <NUM>. The inner diameter of the inlet end of the first connector <NUM> is smaller than the inner diameter of the upper collecting tube <NUM>, and the inner diameter of the outlet end of the second connector <NUM> is smaller than the inner diameter of the lower collecting tube <NUM>. By selecting the first connector <NUM> and the second connector <NUM> to replace the spherical head in the prior art, the opening of the containment <NUM> is as small as possible, so as to ensure the integrity of the containment <NUM> to the utmost extent.

Two ends of the heat exchange tube bundle are respectively welded and fixedly connected to the upper collecting tube <NUM> and the lower collecting tube <NUM>, the inlet of the heat exchange pipe <NUM> is connected with the first through holes <NUM> and the heat exchange tube steam inlet <NUM>, and the outlet of the heat exchange tube <NUM> is connected with the second through hole and the condensate return port of the heat exchange tube communicate. Specifically, the heat exchange tube bundle is a C-shaped vertical heat exchange tube bundle, and each heat exchange tube <NUM> includes an upper inclined section <NUM>, a middle connecting section <NUM>, and a lower inclined section <NUM>. The upper inclined section <NUM> and the end of the first flange <NUM> are fixed by butt welding, and the lower inclined section <NUM> and the end of the second flange <NUM> are fixed by butt welding.

The upper inclined section <NUM> and the lower inclined section <NUM> are inclined slightly downward along the direction of fluid flow, that is, the upper inclined section <NUM> is slightly inclined downward from the upper collecting tube <NUM> to the middle connecting section <NUM>, and the lower inclined section <NUM> is slightly inclined downward from the middle connecting section <NUM> to the lower collecting tube <NUM>. The inclination angle of the upper inclined section <NUM> and the lower inclined section <NUM> (that is, the angle between the heat exchange tube <NUM> and the horizontal plane) is between <NUM>-<NUM> degree. The middle connecting section <NUM> is a vertical section.

The frame assembly <NUM> is welded by a series of section steels, and is mainly used to support and fix the C-shaped vertical heat exchange tube bundle. The upper and lower ends of one side of the frame assembly <NUM> are respectively welded and fixed to the upper collecting tube <NUM> and the lower collecting tube <NUM>, and the bottom of the other side is fixed on the concrete support.

The frame assembly <NUM> also includes a bracket <NUM> for supporting and fixing the upper collecting tube <NUM> and another bracket <NUM> for supporting and fixing the lower collecting tube <NUM>. There are brackets <NUM> in the frame assembly <NUM>, which are located at the opening end and the closed end of the upper collecting tube <NUM>, respectively. To facilitate fixing, a curved backing plate <NUM> matching the outer diameter of the upper collecting tube <NUM> is also provided between the upper collecting tube <NUM> and the bracket <NUM>, and then being fixed by welding. There are two brackets <NUM>, which are respectively located at the opening end and the closed end of the lower collecting tube <NUM>. In order to facilitate fixing, a curved backing plate matching the outer diameter of the lower collecting tube <NUM> is also arranged between the lower collecting tube <NUM> and the bracket <NUM> (not shown), and then fixed by welding.

The frame assembly <NUM> is welded with tube bundle support assemblies <NUM> and <NUM> for fixing and supporting the C-shaped vertical heat exchange tube bundle, wherein the tube bundle support assembly <NUM> is welded to the upper part of the frame assembly <NUM> for fixing and supporting the upper inclined section <NUM>. The tube bundle support assembly <NUM> is welded to the lower part of the frame assembly <NUM> to fix and support the lower inclined section <NUM>. The tube bundle support assemblies <NUM> and <NUM> are plates defining openings. The upper inclined section <NUM> and the lower inclined section <NUM> of the heat exchange tube <NUM> respectively pass through the openings and are fixed to prevent large-scale vibrations during work.

The manufacturing process of the passive condenser for a nuclear power plant of the present invention is detailed as following:.

Claim 1:
A nuclear power plant comprising a passive condenser and a containment, the passive condenser comprising:
an upper collecting tube (<NUM>) defining a plurality of heat exchange tube steam inlets (<NUM>) and having an opening end and a closed end, and the opening end being fixedly connected to a first connector (<NUM>), the upper collecting tube (<NUM>) extending through the containment of the nuclear power plant;
first flanges (<NUM>) defining first through holes (<NUM>) and being arranged at positions of the heat exchange tube steam inlets (<NUM>), the first flanges (<NUM>) being fixedly connected to the upper collecting tube (<NUM>), with the first through holes (<NUM>) being in communication with the heat exchange tube steam inlets (<NUM>);
a lower collecting tube (<NUM>) defining a plurality of heat exchange tube condensate return ports and having an opening end and a closed end, and the opening end being fixedly connected to a second connector (<NUM>), the lower collecting tube (<NUM>) extending through the containment of the nuclear power plant;
second flanges (<NUM>) defining second through holes and being arranged at positions of the heat exchange tube condensate return ports, the second flanges (<NUM>) being fixedly connected to the lower collecting tube (<NUM>), with the second through holes being in communication with the heat exchange tube condensate return ports; and
a heat exchange tube bundle comprising a plurality of heat exchange tubes (<NUM>), each of the heat exchange tubes (<NUM>) comprising an upper inclined section (<NUM>), a middle connecting section (<NUM>) and a lower inclined section (<NUM>), the upper inclined section (<NUM>) being fixedly connected to the first flange (<NUM>), and the lower inclined section (<NUM>) being fixedly connected to the second flange (<NUM>).