JPH02238201A - Steam generator - Google Patents

Abstract

PURPOSE:To detect at an early stage the sound produced, when a breakage occurs in an inner tube or outer tube, and conveyed by the inner or outer tube by providing a plurality of sound sensors in tube sheets and intermediate tube sheets. CONSTITUTION:An inner tube 103 is enclosed circumferentially by an outer tube 104 with a slight clearance 4 between the two tubes; the outer tube 104 is supported by an upper intermediate tube sheet 107 at the upper end and a lower intermediate tube sheet 108 at the lower end. There are provided sound sensors A, B, C, and D to an upper tube sheet 105, a lower tube sheet 106, the upper intermediate tube sheet 107, and the lower intermediate tube sheet 108 respectively. If a crack is produced in the inner tube 103, steam leaks through the crack in the tube. The abnormal sound produced by the leakage reaches the sound sensors A, B, C, and D through transmission by the inner tube or the outer tube. If the outer tube 104 cracks at some spot, the high- pressure gas from an intermediate plenum 123 or a plenum 124 flows in. Then an abnormal sound likewise reaches the sound sensors through transmission by the inner tube or the outer tube. Thus a crack occurring in the inner tube 103 or the outer tube 104 can be detected at an early stage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a steam generator used, for example, in a fast breeder reactor plant.

(Prior technology) Fast breeder reactor. For example, a tank-type fast breeder reactor that employs a dual cooling system generally has the following configuration. The reactor vessel contains a coolant (eg, liquid metal sodium) and a reactor core.

The reactor core is composed of multiple fuel assemblies, control salaries, etc. The coolant flows upward through the core, and as it does so, its temperature rises due to the heat of nuclear reaction in the core. The humidified coolant flows out above the reactor core and flows into an intermediate heat exchanger installed in the reactor vessel. In this intermediate heat exchanger, it exchanges heat with the secondary coolant, is cooled, and flows out of the intermediate heat exchanger. Then, it flows upward through the core again.

On the other hand, the secondary coolant whose temperature has been raised by exchanging heat with the intermediate heat exchanger is introduced into a steam generator placed outside the reactor vessel, where it is cooled by exchanging heat with the water supply system. The cooled secondary coolant is transferred to the intermediate heat exchanger again. Also, the steam generated through heat exchange is transferred to the steam turbine system and used for power generation.

A shell-and-tube type heat exchanger, which is vertical and has tube sheets at the top and bottom, is normally used as a steam generator. The adopted one will be used. This is shown in Figures 4 to 6.
This will be explained with reference to the figures. FIG. 4 is a sectional view showing the overall structure of the steam generator, and reference numeral 1 in the figure indicates the outer shell.

A plurality of double-pipe heat exchanger tubes 2 are arranged within this outer shell 1. As shown in enlarged views in FIGS. 5 and 6, this double-tube heat exchanger tube 2 includes an outer tube 3 and an inner tube 5 disposed on the inner circumferential side of the outer tube 3 with a slight gap 4 therebetween. It is composed of. The inner tube 5 is supported at its upper and lower ends by an upper tube sheet 6 and a lower tube sheet 7. On the other hand, the outer tube 3 is supported at its upper and lower ends by an intermediate tube sheet 8 and a lower tube sheet 7.

A water inlet plenum 9 is formed at the lower end of the outer shell 1.
A water inlet 10 is formed in this water inlet plenum 9 . A water flow pipe (not shown) is connected to this water inlet 10. Also, as shown in Figure 4, the water inlet plenum 9
There is a manhole 11 installed. On the other hand, outside 11i
A steam outlet plenum 12 is formed at the upper end of i11, and a steam outlet 13 is formed in this steam outlet plenum 12. A steam outlet pipe (not shown) is connected to this steam outlet 13.

A manhole 14 is installed in the steam outlet plenum 12.

A cooling plenum 15 is formed on the lower side of the intermediate tube plate 8 of the outside 1] 1ii11, and a coolant inlet plenum 16 is formed in this coolant inlet plenum 15. A coolant inflow pipe (not shown) is connected to this coolant inlet 16 . On the other hand, a coolant outlet plenum 17 is formed above the lower tube plate 7 of the outer shell 1, and a coolant outlet 18 is formed in this coolant outlet plenum 17. A coolant outflow pipe (not shown) is connected to this coolant outlet 18. In the figure, reference numeral 19 is a bellows inserted into the outer shell 1, reference numeral 20 is an entrance window, and reference numeral 21 is an exit window. Also, reference numeral 23 in FIG. 5 is a groove. This groove 23 is for leak detection and is formed on the outer tube 3 side. In order to form this groove 23, the outer tube 3 has a wall thickness that is approximately the depth of the groove 23 added to the thickness required from the viewpoint of pressure resistance. An intermediate plenum 24 is formed roughly between the upper tube sheet 6 and the intermediate tube sheet 8, and a leak detection nozzle 25 is received in the intermediate plenum 24. A leak detection section (not shown) is connected to this leak detection nozzle 25. Further, the minute gap 4 shown in FIGS. 4 and 5 ranges from several microns to several tens of microns.

According to the above configuration, the high temperature coolant is first supplied to the coolant inlet 1.
6 into the coolant inlet plenum 15 and into the heat exchanger tube bundle through the inlet window 20. The coolant then flows down the outside of the heat transfer tube 2 and passes through the outlet window 21 to the coolant outlet plenum 17.
leaks inside. From there it flows out of the steam generator via the coolant outlet 18 and the coolant outlet pipe. On the other hand, water flows through the water flow pipe and the water inlet 10 into the water flow plenum 9.
flow inside.

From there, it flows into the inner tube 5 of the heat exchanger tube 2 and rises.

At that time, it exchanges heat with the coolant flowing down the outside of the heat transfer tube 2, heats the stomach, and turns into steam. This steam flows out into the steam outlet blemish 12 and is transferred to a turbine system (not shown) via the steam outlet 13 and steam outlet piping to be used for power generation.

In the above configuration, damage to the heat exchanger tubes 2 is detected as follows. First, cracks occur in the inner pipe 5 and water
In the case where steam leaks, the leaked water/steam diffuses through the minute gap 4 and flows upward or downward through the groove 23 formed on the outer tube 3 side. The water/steam flowing upward flows into the intermediate plenum 24 formed between the tube sheets 6 and 8, and flows through the leak detection nozzle 25 to a leak detection device (not shown). This allows damage to the inner tube 5 to be detected by detecting pressure fluctuations or by detecting a leak with a leak detection sensor.

Next, a case where the outer tube 3 is damaged will be explained.

In this case, the gas within the intermediate plenum 24 diffuses within the minute gap 4 and flows out from the damaged portion of the outer tube 3 to the coolant side. Therefore, the gas pressure within the intermediate plenum 24 decreases, and by detecting this, the break 10 of the outer tube 3 is detected. Otherwise, damage to the outer tube 3 is detected by detecting the outflowing gas using a scum detector installed on the coolant side.

(Problem to be solved by the invention) According to the above configuration, there are the following problems.

■ In the case of any breakage, the breakage is detected by detecting the leak through the minute gap 4 between the -b inner tube 5 and the outer tube 3. In this sense, the minute gap 4 is as wide as possible. is valid. However, if it becomes too wide, thermal resistance will increase, leading to an increase in the size of the steam generator. In other words, as the thermal resistance increases, the desired heat transfer performance cannot be provided unless the number of heat transfer tubes 2 is increased. In this sense, designing the minute gap 4 is difficult.

■ Next, the function of the minute gap 4 is the inner pipe 5 or outer pipe 3.
It has a function to prevent cracks that occur from expanding. At the same time, the above-mentioned thermal resistance must be taken into consideration, and it is necessary to provide a state in which the inner tube 5 and the outer tube 3 are not integral but in close contact with each other in terms of metallographic structure. It is difficult.

(2) Even if the minute gap 4 is formed with high accuracy, it will change due to thermal expansion of the inner tube 5 and the outer tube 3, and in that case, there is a problem that the heat transfer performance will deteriorate.

■ If a leak were to occur in the inner tube 5 and outer tube 3 at almost the same time, the coolant and water would react inside the minute gap 4 and generate hydrogen gas. For this reason, the minute gap 4 becomes under high pressure, which may lead to a large leak.

As described above, conventional steam generators have various problems regarding the gap between the inner tube and the outer tube. The present invention has been made in order to solve the above problems, and it is possible to detect damage to heat transfer tubes at an early stage, and to improve safety in the unlikely event that double-pipe heat transfer tubes are simultaneously damaged. An object of the present invention is to provide a steam generator whose performance can be improved and whose size can be reduced.

[Structure of the Invention] (Means for Solving the Problems) The present invention includes an outer shell having a water inlet plenum, a steam outlet plenum, a coolant inlet plenum, and a coolant outlet plenum, and a plurality of outer shells arranged in the outer shell. a heat exchanger tube whose upper and lower ends are supported by a tube sheet installed in the external chamber, through which water flowing into the water inlet plenum flows and becomes steam and flows out to the steam outlet plenum; It is characterized by being equipped with an acoustic sensor.

Further, the heat transfer tube is of a double tube type including an inner tube and an outer tube, and the inner tube and the outer tube are each supported at an upper end and a lower end by an independent tube sheet, and an acoustic sensor is provided on each or a part of the inner tube and the outer tube. The acoustic sensor is characterized in that a piezoelectric element made of lead zirconate titanate (PZT) is used in the low-temperature tube plate portion on the water supply side, and a piezoelectric element made of lithium diobate is used in the high-temperature tube plate portion on the steam side.

(Function) By installing multiple acoustic sensors in the tube sheet and intermediate tube sheet, it is possible to detect early the sound generated when the inner tube or outer tube is damaged and is transmitted through the inner tube or outer tube. . In order to detect sound, there is no need to make a large gap between the inner tube and the outer tube, so the thermal resistance can be reduced and the device can be made smaller. Furthermore, by providing a plurality of acoustic sensors, it becomes possible to determine the location of damage, which facilitates repair.

Furthermore, by using acoustic sensors on the paired tube sheets or the middle tube sheet as transmitters and receivers, abnormalities in the inner tube or outer tube can be detected early, and can also be used for inspection during use. can.

Embodiments) Examples of the steam generator according to the present invention will be described below with reference to FIGS. 1 to 3. FIG. 1 is a longitudinal sectional view showing the overall structure of the steam generator according to this embodiment, and the reference numeral 101 in the figure is
indicates external use. A plurality of double-pipe heat exchanger tubes 102 are arranged within this outer shell 101 . This double-tube heat exchanger tube 102 has a configuration as shown in FIGS. 2 and 3. The reference numeral 103 in the figure is an inner tube, and this inner tube 10
An outer tube 104 is disposed on the outer peripheral side of the tube 3 with a small gap 4 interposed therebetween.

These inner tube 103 and outer tube 104 are made of, for example, Austenite 1-stainless steel or high chrome steel. The inner tube 103 is supported at its upper and lower ends by an upper tube sheet 105 and a lower tube sheet 106.

Further, the outer tube 104 is supported at its upper and lower ends by an upper intermediate tube sheet 107 and a lower intermediate tube sheet 108.

Acoustic sensors A, B, C, and D are installed on both the upper and lower tube plates 105 and 106, and roughly on the upper and lower intermediate tube plates 107 and 108, respectively. FIG. 3 shows a typical example of the upper surface arrangement of the upper tube plate 105, in which a large number of inner tubes 103 are arranged at a triangular pitch, and the acoustic sensor D is connected to each inner tube.
A plurality of them are provided between 03 and 03. Other tube sheets and intermediate tube sheets are similarly provided with acoustic sensors.

A water inlet plenum 113 is formed at the lower end of the outer shell 101, and a water flow pipe 1 is installed in this water inlet plenum 113.
13a is connected. On the other hand, a steam outlet plenum 114 is formed at the upper end of the outer shell 101, and a steam outlet pipe 115 is connected to this steam outlet plenum 114. A coolant inlet plenum 116 is formed below the upper intermediate tube plate 107 of the outer shell 101, and a coolant inflow pipe 117 is connected to the coolant inlet plenum 116. On the other hand, a coolant outlet blenum 118 is formed above the lower intermediate tube plate 108 of the outer shell 101.
This coolant outlet plenum 118 has a coolant outlet pipe 11.
9 is connected.

In the figure, reference numeral Q120 is a bar D- inserted in the outer shell 101, reference numeral 121 is an entrance window, and reference numeral 122 is an exit window. Further, an upper intermediate plenum 123 and a lower intermediate plenum 124 are formed between the upper tube sheet 105 and the upper intermediate tube sheet 107 and between the lower tube sheet 106 and the lower intermediate tube sheet 108, respectively. Upper intermediate plenum 123
A leak detection nozzle 125 is connected to the lower intermediate plenum 124, and a leak detection nozzle 126 is connected to the lower intermediate plenum 124. A leak detection section (not shown) is connected to these leak detection nozzles 125 and 126.

The operation will be explained based on the above configuration. First, there is the normal heat exchange effect, which is almost the same as before. That is, the coolant flows into the coolant inlet brenum 116 via the coolant inlet pipe 117 .

The coolant that has entered the coolant inlet plenum 116 flows into the heat exchanger tube bundle through the inlet window 121 and flows down the outside of the heat exchanger tubes 102 . The coolant flowing down the outside exits through the outlet window 122 into the coolant outlet plenum 118 and exits the steam generator via the coolant outlet piping 119.

Meanwhile, water flows into the water inlet plenum 113 via the water flow pipe 113a. The water flowing into the water inlet plenum 113 flows into the inner tube 103 of the heat transfer tube 102. The water that has flowed into the inner pipe 103 rises within the inner pipe 103. At that time, it exchanges heat with the coolant flowing down the outside of the heat exchanger tube 102 to raise its temperature and turn into steam. The generated steam flows out from the inner pipe 103 into the steam outlet plenum 114, is roughly transferred to a turbine system (not shown) via the steam outflow pipe 115, and is used for power generation.

Next, regarding the action of the acoustic sensor, see Figures 2 and 3.
This will be explained with reference to the figures. First, regarding the case where a crack occurs in the inner tube 103, in this case, water vapor leaks from the damaged portion of the inner tube 103. The abnormal sound accompanying this leakage propagates through the inner tube or outer tube and reaches each acoustic sensor.
Reach C and D. If a crack occurs in the outer tube 104, high pressure gas in the intermediate plenum 123 or 124 will flow in. The abnormal sound at this time similarly propagates through the inner tube or outer tube and reaches each acoustic sensor.

If the inner tube and outer tube are damaged at the same time, a rapid thorium-water reaction occurs, making it easier to detect abnormal sounds.

By the way, since a plurality of Me sensors are provided on each tube sheet or intermediate tube sheet, it is possible to estimate the damage position by determining the strength of the signal obtained from each sensor.

The acoustic sensor can also be used as a transmitter by applying a voltage to the acoustic sensor. For example, if acoustic sensors C and D are used as transmitters and acoustic sensors A and B are used as receivers, it is possible to detect an abnormality because the sound propagation characteristics of cracked heat exchanger tubes are different.

As the acoustic sensor, the lower tube sheet 106 or the lower intermediate tube sheet 108 on the water supply side is used at a low temperature of about 250°C, so it is equipped with a highly sensitive piezoelectric element zirconate titanate (PZT).
) However, since the upper tube sheet 108 or the upper intermediate tube sheet 107 is used at high temperatures, a high temperature piezoelectric element such as lithium diobate is suitable.

It is conventional to provide a pressure gauge or a gas analyzer for leak detection in the intermediate plenum 123 and 124 to supplement and cover the above-mentioned detection function.

According to this embodiment, the following effects are achieved.

(2) Since the occurrence of cracks in the inner tube 103 or the outer tube 104 can be detected at an early stage, it is possible to prevent the spread of the accident.

■ Since the location of damage can be identified, it becomes possible to shorten the number of days required for repair, improving plant operating efficiency.

■ Since the propagation of sound within the inner or outer tube is used to detect damage, there is no need to increase the gap between the two to facilitate the flow of gas, thereby preventing an increase in thermal resistance. Therefore, it is possible to downsize the steam generator.

■ By using acoustic sensors as receivers and transmitters, it is possible to detect changes in sound propagation characteristics due to the occurrence of cracks. If this is carried out as an inspection during the service period, crack U4 letters can be detected before they occur.

Note that the present invention is not limited to application to steam generators having double-pipe heat exchanger tubes. Even if the steam generator has a single tube type heat transfer tube, if the tube sheet is shifted to the right, an acoustic sensor is installed in the tube sheet section. It is also possible to directly detect the leakage point.It is also possible to identify the leak location.

[Effects of the Invention] According to the present invention, it is possible to detect damage to a heat exchanger tube at an early stage, and the spread of an accident can be prevented.

Furthermore, since the location of the damage can be identified, the number of days required for repair can be reduced, and the operating rate of the plant can be improved.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a longitudinal cross-sectional view showing an embodiment of the steam generator according to the present invention, and Fig. 2 is a longitudinal cross-sectional view showing an enlarged portion of the double heat exchanger tube in Fig. 1. , FIG. 3 is a plan view of FIG. 2, FIG. 4 is a vertical sectional view showing a conventional steam generator, FIG. 5 is a perspective view showing the heat transfer tube of the steam generator in FIG. 4, and FIG. 6 is a sectional view showing the heat exchanger tube in FIG. 5. FIG. ...Outer shell...Double tube type heat transfer tube...Inner tube...Outer tube...Upper tube sheet 106...Lower tube sheet 107...Upper intermediate tube sheet 108...Lower Intermediate tube plates 109-112...Acoustic sensors A-D113...
Water inlet plenum 113a...Water flow pipe 114...Steam outlet plenum 115...Steam outflow pipe 116...Coolant inlet plenum 117...Coolant inflow pipe 118...Coolant outlet plenum 119... ... Coolant outflow pipe 120 ... Bellows 121 ... Inlet window 122 ... Outlet window 123, 124 ... Intermediate plenum 125, 1
26... Leak detection nozzle ↑ Chimney 1 Figure Kaya surface Figure Kaya figure Kaya Mu recess

Claims (2)

[Claims] (1) an outer shell having a water inlet plenum and a steam outlet plenum, as well as a coolant inlet plenum and a coolant outlet plenum, and a plurality of outer shells arranged within this outer shell, with their upper and lower ends installed within the outer shell. A steam system characterized by comprising: a heat exchanger tube supported by a tube sheet and through which water flowing into the water inlet plenum flows to become steam and flows out into the steam outlet plenum; and a plurality of acoustic sensors provided in the tube sheet. generator. (2) The heat transfer tube is a double tube type consisting of an inner tube and an outer tube, and the upper and lower ends of the inner tube and the outer tube are supported by independent tube sheets, and each or a part thereof has an acoustic sensor. The acoustic sensor is characterized in that a piezoelectric element made of lead zirconate titanate (PZT) is used in the low-temperature tube plate portion on the water supply side, and a piezoelectric element made of lithium niobate is used in the high-temperature tube plate portion on the steam side. A steam generator according to claim 1.