Patent Description:
Steam generator is the hub of the primary and secondary circuits of the nuclear power plant, which is used to transfer the heat generated by the reactor to the secondary side to generate steam, and transport the steam to the steam turbine to drive the generator to generate electricity.

The pressure boundary of primary side of the steam generator includes a lower head, a pipe plate and a pipe bundle, wherein the lower head is divided into an inlet water chamber and an outlet water chamber by a separating plate, and the reactor coolant enters through an inlet connecting pipe located on the lower head of the steam generator, flows through the U-shaped heat transfer pipe, and then flows out through the outlet connecting pipeon the lower head.

The pressure boundary of the secondary side of the steam generator includes the pipe plate, the lower cylinder, the conical cylinder, the upper cylinder and the upper head. The water enters the steam generator via the water supply pipe, enters the water supply ring pipe after passing through the water supply pipe, and is sprayed via the nozzles on the water supply ring pipe. After mixed with the saturated water seperated from the steam and water separating device, the water flows into an annular descending channel between the pipe bundle sleeve and the housing, and reaches the secondary side surface of the pipe plate. The water enters the pipe bundle through the gap between the lower end of the sleeve and the secondary side surface of the pipe plate, and the water is heated as it rises through the pipe bundle, and part of the water turns into steam, thereby forming a steam-water mixture. After the steam-water mixture flows out of the top of the pipe bundle, it enters the steam and water separator for coarse separation, enters the dryer for fine separation, and finally outputs dry saturated steam.

Heat transfer pipes of the steam generator constitute the pressure-bearing boundary between the primary and secondary sides, and undertake the function of isolating the radioactive substances of the primary circuit coolant of the reactor. The heat transfer pipe is a seamless steel tube with a wall thickness of about <NUM>. The integrity of the heat transfer pipe must be guaranteed to prevent the heat transfer pipe from breaking and leaking and causing serious contamination of the secondary circuit system.

It is well known that, loosening parts entering the steam generator via the water supply system can cause damage to the heat transfer pipes. The loosening parts vary in size and can enter the steam generator via the J-shaped pipe or spray head on the water supply ring pipe. Under the action of the fluid, the loosening parts enter the descending channel and contact the heat transfer pipes via the opening between the bottom of the pipe bundle sleeve and the pipe sheet, thereby forming dents or continuous impact marks on the surface of the heat transfer pipes. Loosening parts smaller than the gap of the heat transfer pipes may enter the inside of the pipe bundle and stay in the relative stagnation area of the fluid. The remaining loosening parts move with high frequency and small amplitude under the micro-force of the fluid, causing fretting wear on the heat transfer pipes, thereby resulting in reduction of thickness of the pipe wall. Impact dents and fretting wear can, in severe cases, cause heat transfer pipes to rupture, causing unplanned shutdowns of nuclear power plants that require costly repairs. Therefore, it is necessary to provide a device to prevent foreign loosening parts from entering the steam generator and to prevent the entered loosening parts from migrating to the pipe bundle.

At present, the conventional devices for preventing foreign matter from entering the steam generator mainly adopt the screening method, i.e., setting a small diameter J-shaped pipe or an I-shaped pipe with spray holes on the water supply ring pipe. When the size of foreign matter is larger than the inner diameter of the J-shaped pipe or the diameter of the spray hole, it can be intercepted in the water supply pipe. However, foreign objects smaller than the inner diameter of the J-shaped pipe or the diameter of the spray hole can still pass through and enter the steam generator. The loosening parts, such as metal strips, welding rods and metal sheets, may still threat the integrity of the heat transfer pipe.

In view of the foregoing, what is needed therefore is to provide a reliable vertical type steam generator of the pressurized water reactor nuclear power plant and a loosening part capturing device thereof, which can collect the loosening parts entering the steam generator through the water supply ring pipe during the commissioning and operation of the nuclear power plant, prevent the loosening parts from entering the pipe bundle area, and improve the working environment of the heat transfer pipe.

<CIT> relates to a sludge trap, or mud drum, for use in nuclear steam generators, including internal baffles defining multiple laminar flow paths having decreased vertical settling distances.

<CIT> relates to a U-tube steam generator having a dual system for collecting loose parts and sludge.

<CIT> relates to removal of concentrated suspended particulate material from the recirculating carry-over water in a nuclear steam generator.

The present invention provides a loosening part capturing device for a steam generator of a pressurized water reactor nuclear power plant and a vertical type steam generator of a pressurized water reaction nuclear power plate, as defined by the claims.

One object of the present invention is to overcome the disadvantages in the prior art, and to provide a reliable vertical type steam generator of the pressurized water reactor nuclear power plant and a loosening part capturing device thereof, which can collect the loosening parts entering the steam generator through the water supply ring pipe during the commissioning and operation of the nuclear power plant, prevent the loosening parts from entering the pipe bundle area, and improve the working environment of the heat transfer pipe.

According to the present invention, a loosening part capturing device for a steam generator of a pressurized water reactor nuclear power plant is defined in claim <NUM>.

According to one aspect of the present invention, the capturing enclosing plates are welded on the top plate, and two ends of the capturing enclosing plates are respectively welded on outer surfaces of the steam and water separator rising cylinders.

According to one aspect of the present invention, an arc transition is provided between the folding plate and the capturing enclosing plate, and the arc transition has a transition radius of <NUM>-<NUM>.

According to one aspect of the present invention, an angle between the folding plate and the capturing enclosing plate is <NUM>-<NUM> degrees.

According to the present invention, the top plate is provided with center holes and circumferential holes, the capturing enclosing plates are located inside the circumferential holes.

According to one aspect of the present invention, a radius of a projection of the capturing enclosing plate and the folding plate on the top plate is larger than a radius of a projection of a water supply loop spray pipe or a J-shaped pipe of the steam generator.

According to another embodiment of the present invention, a vertical type steam generator of a pressurized water reactor nuclear power plant, including an upper dish-shaped head, an upper cylinder, a conical cylinder, a lower cylinder, a pipe plate and a lower head, the pipe plate being provided with a number of pipe holes, two ends of inverted U-shaped pipe bundle being inserted into the pipe holes and mechanically assembled to the pipe plate to form a pipe bundle havinging a number of inverted U-shaped tubes, the pipe bundle being provided with a sleeve at a periphery thereof and a sleeve top cover thereon, the sleeve, the lower cylinder and the conical cylinder jointly defining an annular channel, wherein the sleeve top cover is provied with a sludge collector, the top plate of the sludge collector is provided with a plurality of steam and water separator rising cylinder and capturing enclosing plates, capturing enclosing plates are arrange between every adjacent steam and water separator rising cylinders on the periphery of the top plate, two ends of each capturing enclosing plate are respectively fixedly connected to outer surfaces of the separator rising cylinders, and one end of each capturing enclosing plates afar from the top plate is provided with a folding plate extending towards a center of the top plate.

According to one aspect of the present invention, the capturing enclosing plates are welded on the top plate, and two ends of the capturing enclosing plates are respectively welded on outer surfaces of the steam and water separator rising cylinder.

According to one aspect of the present invention, the sleeve top cover is provided with holes correspondingly connected with a group of steam and water separator rising cylinders, and the steam and water separator rising cylinders each is provided with rotary blades therein, and steam-water two-phase mixture generated by boiling inside the sleeve flows through the holes of the top plate and enters the steam and water separator rising cylinders, the steam and water undergo a spiral centrifugal motion under the action of the rotary blades, and the steam and water are separated under the centrifugal force.

According to one aspect of the present invention, separated water re-enters a pool provided above the sleeve top cover, and wet steam separated by a primary separator continues to flow upward and is separated and dried again by a dryer, and the steam after secondary separation flows out of the steam generator through a current limiter arranged in a center of the upper dish-shaped head.

According to one aspect of the present invention, recirculating water separated from the steam-water separator is mixed with a water supply pipe and enters the annular channel, and there is a pressure difference between the central area and the peripheral circumferential area of the top plate due to a relatively large fluid flow velocity in the annular channel and a relatively small fluid flow velocity in the central area above the sleeve top cover.

According to one aspect of the present invention, a water supply pipe is provided above the sludge collector, and the water supply pipe has an approximate circular structure, and a diameter of the water supply pipe is smaller than that of the sleeve top cover arranged horizontally inside the steam generator.

According to one aspect of the present invention, an angle between the folding plate and the capturing enclosing plates is <NUM> to <NUM> degrees.

According to the present invention, the top plate is provided with center holes and circumferential holes, and the capturing enclosing plates are located inside the circumferential holes.

According to one aspect of the present invention, a radius of a projection of the capturing enclosing plate and the folding plate on the top plate is larger than a radius of a projection of a water supply loop spray pipe or a J-shaped pipe provided by the steam generator.

Compared with the prior art, the vertical type steam generator of a pressurized water reactor nuclear power plant and loosing part capturing device therefor of the present invention has the following advantages: during the refueling period, the water on the secondary side of the steam generator will be emptied, the capturing enclosing plate and the foling plate can capture the loosening parts on the top plate, to prevent the loosening parts from migrating into the annular channel under the action of fluid. When the steam generator is emptied, the water in the area enclosed by the the capturing enclosing plate and the foling plate can be emptied through the small holes in the central area of the top plate of the sludge collector, which will not affect the in-service work of the top plate of the sludge collector. When water is injected into the empty steam generator, the capturing enclosing plate and the foling plate can capture the loosening parts on the top plate, so as to avoid migration into the annular channel under the action of the fluid, thereby realizing reliable operation of the vertical type steam generator of a pressurized water reactor nuclear power plant.

The vertical type steam generator of a pressurized water reactor nuclear power plant and loosing part capturing device therefor and the technical effects thereof of the present invention will be described in detail with reference to the accompanying drawings and specific embodiments, in which:.

In order to make the objects, technical solutions and technical effects of the present invention clearer, the present invention will be further described in detail below with reference to the specific embodiments and drawings.

Referring to <FIG>, which is a schematic structural diagram of a vertical type steam generator <NUM> of a pressurized water reactor nuclear power plant according to one embodiment of the present invention. In the illustrated embodiment, the steam generator <NUM> is a vertical type shell and pipe heat exchanger including an upper dish-shaped head <NUM>, an upper cylinder <NUM>, a conical cylinder <NUM>, a lower cylinder <NUM>, a pipe plate <NUM> and a lower head <NUM>.

The pipe plate <NUM> is provided with thousands of pipe holes <NUM>, and two ends of the inverted U-shaped pipe bundle <NUM> are inserted into the pipe holes <NUM> and are mechanically connected to the pipe plate <NUM>. The pipe bundle <NUM> forms a heat transfer surface that exchanges heat with the primary circuit, so that the heat of the primary circuit coolant is transferred to the secondary side, and the water on the secondary side is boiled to generate steam.

The seperating plate <NUM> divides the interior of the lower head <NUM> into a first chamber <NUM> and a second chamber <NUM>, forming a pipe header of an inverted U-shaped pipe. The first chamber <NUM> is the primary side fluid inlet chamber, which is connected to the inlet connecting pipe <NUM>. The second chamber <NUM> is the primary side fluid outlet chamber, which is connected to the outlet connecting pipe <NUM>. Therefore, the primary side coolant of the reactor enters the first chamber <NUM> from the inlet connecting pipe <NUM>, enters the second chamber <NUM> through the pipes of the inverted U-shaped pipe bundle <NUM>, and flows out of the steam generator <NUM> through the outlet connecting pipe <NUM>.

A sleeve <NUM> is provided on the periphery of the pipe bundle <NUM>. The sleeve <NUM>, the lower cylinder <NUM> and the conical cylinder <NUM> form an annular channel <NUM>. The top of the sleeve <NUM> is provided with a sludge collector <NUM>. The sludge collector <NUM> is provided with a set of holes <NUM>. The holes <NUM> are correspondingly connected to a set of steam and water separator rising cylinder <NUM>, and the rising cylinders <NUM> are provided with rotary blades <NUM>. The steam-water two-phase mixture generated by the boiling inside the sleeve <NUM> flows through the holes <NUM> on the sleeve top cover <NUM> and enters the rising cylinder <NUM>. Spiral centrifugal motion of the steam-water occurs under the action of the rotary blades <NUM>. The steam and water separate under the action of the centrifugal force. The separated water re-enters the pool above the sludge collector <NUM>. The wet steam separated by the primary separator continues to flow upward through the dryer <NUM> for separation and drying again, and the steam after secondary separation flows out of the steam generator <NUM> through the current limiter <NUM> arranged in the center of the upper dish-shaped head <NUM>.

The water supply pipe <NUM> includes a water supply ring pipe assembly <NUM> and a thermowell assembly <NUM>. The water supply ring pipe assembly <NUM> is located above the thermowell assembly <NUM>, to reduce the thermal stratification effect of the fluid in the pipe. The water supply ring pipe assembly <NUM> has an approximately circular structure and is horizontally arranged inside the steam generator <NUM>. The water supply nozzles <NUM> are welded on the water supply ring pipe assembly <NUM>, and the number of the holes <NUM> and the nozzles <NUM> is calculated and determined according to the flow rate of the main water supply. The nozzle <NUM> is provided with a large number of nozzle holes, and the diameter of the nozzle holes is <NUM>-<NUM>.

Under normal operation and normal operation transient conditions of the steam generator <NUM>, the water level in the steam generator <NUM> needs to ensure that the water supply outlet is submerged. The main water supply of the steam generator <NUM> enters the fluid channel 71a in the water supply ring pipe assembly <NUM> from the fluid channel 72a in the thermowell assembly <NUM>, and flows into the steam generator <NUM> through the fluid channel 73a inside the nozzle. At the same time, due to the small diameter of the opening of the nozzle, the foreign matter entering the water supply can be intercepted by the opening, and the foreign matter larger than the inner diameter of the opening of the nozzle will not enter the steam generator <NUM>. The main water supply entering the steam generator <NUM> via the water supply ring is mixed with the recycled water separated by the separator and the dryer and enters the annular channel <NUM>, enters the pipe bundle <NUM> through the opening <NUM> at the bottom of the sleeve <NUM>, and generates steam by heating and boiling.

Referring to <FIG>, which is a schematic structural diagram of a sludge collector collector <NUM>. The top plate <NUM> of the sludge collector <NUM> is provided with a large number of small center holes 51a in the central area, small circumferential holes 51b in the peripheral peripheral area, and a nunber of steam and water separator rising cylinders <NUM>. The recirculated water separated from the steam-water separator enters the outer space of the rising cylinder <NUM> of the steam-water separator, and most of the recirculated water is mixed with the water supply from the water supply pipe <NUM> and enters the annular channel <NUM>. The fluid flow velocity of the annular channel <NUM> is relatively large, the fluid flow velocity above the sleeve top cover <NUM> is relatively slow, and there is a pressure difference between the central region and the peripheral circumferential region of the top plate <NUM>. The existence of the above-mentioned pressure difference causes a part of the recirculating water to enter the sludge collector <NUM> from the small center holes 51a in the central region of the top plate <NUM>, and flow out from the small circumferential holes 51b in the peripheral peripheral region. Inside the sludge collector <NUM>, the recirculating water flows radially from the center in the direction of increasing radius, and the fluid velocity gradually decreases, so that the sludge particles suspended in the recirculating water are deposited on the inside surface of the sludge collector <NUM>, thereby realizing passive deposition of the sludge.

Capturing enclosing plates <NUM> are provided between every adjacent steam and water separator rising cylinders <NUM> located on the periphery. The capturing enclosing plate <NUM> is welded on the top plate <NUM>, and two ends of the capturing enclosing plate <NUM> are welded on the outer surface of the steam and water separator rising cylinders <NUM> (other fastening methods can be used, such as screw connection or riveting). In this way, the steam and water separator rising cylinders <NUM> and the capturing enclosing plate <NUM> on the periphery of the steam generator <NUM> are jointly enclosed around the outer periphery of the top plate <NUM> of the sludge collector <NUM>. One end of the capturing enclosing plate <NUM> afar from the top plate <NUM> is provided with a folding plate <NUM> extending toward the center of the top cover of the sludge collector <NUM>. In other embodiments of the present invention, an arc transition may also be provided between the folding plate <NUM> and the capturing enclosing plate <NUM>, and the arc transition has a transition radius of <NUM>-<NUM>.

Referring to <FIG>, which is a schematic structural diagram of the loosening parts capturing device. The loosening parts capturing device is set up on the top plate of the sludge collector <NUM>, and includes a capturing enclosing plate <NUM> and a folding plate <NUM> connected thereto. The folding plate <NUM> extends toward the center of the top plate <NUM> of the sludge collector <NUM>. The capturing enclosing plate <NUM> is located inside the circumferential holes 51b of the top plate <NUM> of the sludge collector <NUM>. Therefore, the setting of the capturing enclosing plate <NUM> does not affect the pressure difference between the central area 51a and the peripheral peripheral area 51b of the top plate <NUM>, and does not affect normal functioning of the sludge collector <NUM>.

Compared with the prior art, the vertical type steam generator of a pressurized water reactor nuclear power plant and loosing part capturing device therefor of the present invention has the following advantages:
The radius of a projection of the capturing enclosing plate <NUM> and the folding plate <NUM> on the top plate <NUM> is larger than a radius of a projection of a water supply loop spray pipe or a J-shaped pipe of the steam generator <NUM>. Since the fluid velocity in the center of the pool above the sludge collector <NUM> is relatively small, when foreign matter (such as metal rods, welding rods, and metal sheets) having a size smaller than the inner diameter of the J-shaped pipe or the diameter of the spray hole, enters the steam generator <NUM>, the foreign matter either settles on the top plate <NUM> under the action of gravity or captured by the capturing enclosing plate <NUM> and the folding plate <NUM> before migrating to the annular channel <NUM>.

Claim 1:
A loosening part capturing device for a steam generator (<NUM>) of a pressurized water reactor nuclear power plant, arranged on a top plate (<NUM>) of a sludge collector (<NUM>), the top plate (<NUM>) being provided with a plurality of steam and water separator rising cylinders wherein capturing enclosing plates (<NUM>) fixedly connected to the top plate (<NUM>) are provided between every adjacent steam and water separator rising cylinders (<NUM>) on the periphery of the top plate (<NUM>), two ends of each capturing enclosing plate (<NUM>) are respectively fixedly connected to outer surfaces of the steam and water separator rising cylinders (<NUM>), and one end of each capturing enclosing plates (<NUM>) afar from the top plate (<NUM>) is provided with a folding plate (<NUM>) extending towards a center of the top plate (<NUM>), characterized in that the top plate (<NUM>) is provided with center holes (51a) and circumferential holes (51b), the capturing enclosing plates (<NUM>) are located inside the circumferential holes (51b).