JPS63143403A - Steam generator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention provides a steam generator for use in a pressurized water nuclear reactor, in which the shape of the tube plate is improved to suppress the accumulation of sludge. Regarding the generator.

(Prior Art) A pressurized water nuclear reactor uses a steam generator that converts high-temperature, high-pressure water generated in the reactor into steam to drive a steam turbine.

FIG. 2 shows the structure of a conventional steam generator. A large number of U-shaped heat transfer tubes 3 are arranged inside an inner cylinder 2 of a container 1, supported in places by supports 4. . Both ends of the heat transfer tubes 3 communicate with a primary water inlet 6 or a primary water outlet lower end at the lower end of the container 1 via tube sheets 5, respectively.

A separator 8 and a dryer 9 are installed in the upper half of the container 1. In the figure, reference numeral 10 indicates a secondary water inlet, and 11 indicates a steam l.

High-temperature, high-pressure water generated in a nuclear reactor (not shown) enters the container 1 from the primary water inlet 6, flows through the U-shaped heat transfer tube 3 via the tube plate 5, and exchanges heat with the secondary water. Shun, who has been cooled by the exchange, flows out of the primary water supply "17.

On the other hand, low-temperature secondary water flows into the container 1 from the secondary water inlet 10, descends through the center of the container 1 and the downcomer 12 between the container 1 and the inner cylinder 2, and is turned over on the tube plate 5. , ascends inside the inner cylinder 2. This secondary water receives heat from the high-temperature primary water in the heat transfer tube 3 and becomes high in temperature, but since the pressure angle is approximately constant, the pressure falls below the saturation pressure and boils. This gas-liquid two-phase flow continues to rise and is separated into vapor and liquid (water) by the separator 8, and the liquid descends inside the container again. On the other hand, the dryness of the steam is increased by the rough dryer A79, and then the steam is sent from the steam outlet 11 to the turbine (not shown).

(Problems to be Solved by the Invention) The secondary water 20 that has descended through the center of the heat transfer tube 3 and the downcomer 12 as described above is reversed above the tube plate 5 and rises as shown in FIG. It becomes flow 21.

Since this upward flow 21 is distributed as shown in the secondary water flow line 30 in FIG. A deposit of sludge 40 as shown in FIG. 5 is formed. As shown in FIG.
The sludge 40 is deposited on top, and the top thereof is covered with a sludge 40 as a solid-liquid mixed layer 41. This solid-liquid mixed layer 41 moves up and down somewhat due to the flow, and there is a problem in that chlorine ions in the secondary water are concentrated in these parts, causing localized corrosion spots 3a in the heat exchanger tubes 3. .

[Structure of the Invention] (Means for Solving the Problems) A steam generator according to the present invention separates primary water and secondary water in a steam generator used in a pressurized water nuclear reactor, and also separates primary water and secondary water. The upper surface of the tube plate to which the U-shaped heat exchanger tube is fixed is shaped into a gentle convex shape in accordance with the secondary water flow rate distribution on the tube plate.

(Function) According to the present invention, it is difficult for sludge to accumulate in the stagnant portion of secondary water on the tube sheet of a steam generator, and corrosion of the heat exchanger tubes caused by sludge on the tube sheet can be prevented. can.

(Example) An example of a steam generator according to the present invention is shown in FIG. This figure corresponds to FIG. 3 showing a conventional example, and the upper surface of the tube plate 5 is formed with a convex portion 5a so that the radius R portion where the stagnation portion 31 is likely to occur is raised in a ring shape. .

Note that the other configurations are the same as in FIG. 2.

In the steam generator configured as described above, the downflow 20 from the center of the downcomer 12 and the heat exchanger tubes 3 flows through the tube plate 5.
The flow reverses near the upper surface of the flow and becomes an upward flow 21. In the conventional example, 2
Although a stagnation part 31 is formed due to the flow distribution of the water, the present invention provides a gentle convex part 5a@ there, so that it is possible to prevent sludge from accumulating in this part.

[Effects of the Invention] As described above, according to the present invention, it is possible to eliminate the accumulation of sludge on the tube sheet, and as a result, the localization of the heat exchanger tubes caused by the accumulation of sludge as described above can be eliminated. Corrosion etc. can be prevented. Therefore, the soundness of the heat exchanger tubes can be maintained for a long period of time, the life of the steam generator can be extended, and the reliability can be improved, and inspection work during the service life can be simplified and shortened.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view showing an embodiment of the main parts of the steam generator of the present invention, Fig. 2 is a partially cutaway perspective view showing the overall structure of the steam generator, and Fig. 3 is a conventional steam generator. A vertical cross-sectional view illustrating the shape of the tube sheet and the distribution of sludge deposited thereon, FIG. 4 is an explanatory diagram showing secondary water flow lines at LB in a conventional steam generator, and FIG. Cross-sectional view along the v line, No. 6
The figure is a longitudinal sectional view showing the relationship between heat exchanger tubes and sludge deposited on a tube sheet in a conventional steam generator. 1...... Container 2... Inner tube 3... Heat transfer tube 4... Sabo 1-5. ......Tube plate 5a...Convex portion 6...Primary water inlet lower......Primary water outlet 8... ......Separator 9...Dryer 10...Secondary water inlet 11...Steam outlet 12...・・・・・・Downcomer 20・・・・・・Secondary water downward flow 21・・・・・・Secondary water upward flow 31・・・・・・Stagnation part 40・・・・・・・・・Sludge agent Patent attorney Nori Chika Ken Yudo Hirofumi Mitsumata Figure 1 Figure 2 Figure 4

Claims (2)

[Claims] (1) In a steam generator used in a pressurized water reactor, the upper surface shape of the tube plate that separates primary water and secondary water and fixes a large number of U-shaped heat transfer tubes is A steam generator characterized by a gentle convex shape that matches the water flow distribution. (2) The steam generator according to claim 1, wherein the upper surface at a radius R from the center of the tube plate is convex.