JPH0648309B2 - Core coolant flow rate measuring device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a core coolant flow rate measuring apparatus, and more particularly to a core coolant flow rate measuring apparatus suitable for being applied to an internal pump reactor.

[Conventional technology]

As described in Japanese Patent Laid-Open No. 58-10692, a conventional core coolant flow measuring device for an internal pump type nuclear reactor has two induction pipes in the vicinity of an internal pump suction / discharge port (inlet / outlet port). The opening of the pressure tube was installed and the differential pressure of the pump was measured.

The measured differential pressure of the pump part was previously measured by the test device.
The flow rate is calculated from the differential pressure based on the correlation between the flow rate obtained for each pump speed and the pump section differential pressure.

[Problems to be solved by the invention]

In the above-mentioned prior art, an opening of a pressure guiding tube is installed near the inlet / outlet of the pump at the differential measurement position of the pump, and consideration is given to the influence of the suction flow and the discharge flow near the inlet / outlet of the pump on the differential pressure of the pump. However, the flow rate measurement method is apt to be affected by the flow of the pump portion depending on the flow path configuration on the suction and discharge side of the pump and the operating state of the pump, and there is a problem in terms of accuracy and reliability as a flow rate measuring method.

That is, in the method of obtaining the flow rate from the pump differential pressure based on the correlation between the pump differential pressure and the flow rate obtained in advance by the test apparatus, the correlation between the pump differential pressure and the flow rate is equal or constant between the actual machine and the test apparatus. However, if the pump differential pressure near the inlet and outlet of the pump, which is easily affected by the flow of the pump, has different flow configurations on the suction and discharge sides of the pump between the actual machine and the test equipment, or the pump operating state changes. In such a case, there was a problem that the correlation between the pump differential pressure and the flow rate obtained by the test device cannot be directly applied to the actual machine, and even if it is applied, the error becomes large and it is unstable.

An object of the present invention is to solve the above-mentioned problems of the prior art and to accurately measure the core coolant flow rate. An object of the present invention is to provide a core coolant flow rate measuring device.

[Means for solving problems]

The above-mentioned object is that the first pressure detection port is located at a position more than twice the diameter of the diffuser of the internal pump on the upstream side of the internal pump, and the first pressure detection port is formed between the shroud and the reactor vessel. First to detect the pressure in the flow path
A pressure detection pipe and a control rod guide pipe arranged at a position lower than the core in the shroud are arranged in an area formed between the control rod guide pipe located at the outermost periphery and the shroud. A second pressure having a second pressure detection port, the second pressure detection port being formed in the shroud and located above an upper end of an opening for guiding the coolant discharged from the internal pump into the shroud. This can be achieved by providing a detection pipe, a means for obtaining a differential pressure between the respective pressures detected by the first and second pressure detection pipes, and a means for obtaining a core coolant flow rate based on the differential pressure.

[Action]

Since the first pressure detection port of the first pressure detection pipe is arranged at a position at least twice the diameter of the diffuser of the internal pump on the upstream side of the internal pump and detects the pressure in the descending flow path, The pressure on the upstream side of the internal pump can be accurately measured without being affected by the flow turbulence generated near the inlet of the internal pump. Further, the second pressure detection port of the second pressure detection pipe is arranged in a region formed between the control rod guide pipe located at the outermost periphery of the control rod guide pipe below the core in the shroud and the shroud. And is located above the upper end of the opening (formed in the shroud) that guides the coolant discharged from the internal pump into the shroud. Therefore, the flow turbulence near the outlet of the internal pump and the control rod The pressure on the downstream side of the internal pump can be accurately measured without being affected by the turbulence of the flow due to the guide tube.

Therefore, the core coolant flow rate can be accurately obtained.

〔Example〕

FIG. 1 shows a core coolant flow rate measuring apparatus which is a preferred embodiment of the present invention applied to a boiling water reactor.

First, the schematic structure of a boiling water reactor will be described. A reactor pressure vessel 1 has a reactor core 2 formed with a large number of fuel assemblies 3 loaded therein. A lower end portion of the fuel assembly 2 is held by a fuel support fitting 4 supported by a lower core support plate 5. The upper end of the fuel assembly 2 is held by the core upper lattice plate 6. The upper core lattice plate 6 is attached to a core shell 7 surrounding the core 2. The core shroud 7 is installed at the upper end of a shroud 8 attached to the bottom of the reactor pressure vessel 1 by a shroud leg 9. The lower core support plate 5 is attached to the upper end of the shroud 8. A large number of control rod guide tubes 10 are installed in the lower plenum 15 existing below the lower core support plate 5 in the shroud 8. A control rod (not shown) inserted into the core 2 moves up and down in the control rod guide tube 10, and the upper end of the control rod guide tube 10 penetrates the lower core support plate 5. An annular downcomer channel 11 is formed between the outer surfaces of the core shell 7 and the shell 8 and the inner surface of the reactor pressure vessel 1.

The internal pump 12 is arranged below the downcomer channel 11 and attached to the partition plate 14. The internal pump 12 is connected to a motor 13 arranged outside the reactor pressure vessel 1 by a shaft that penetrates the reactor pressure vessel 1.

Due to the rotation of the internal pump 12, the cooling water descends through the downcomer flow path 11 and is pressurized by the internal pump 12, opens the opening 16 and flows into the lower plenum 15. This cooling water is supplied into the fuel assembly 3 through the fuel support fitting 4.

The flow rate of the cooling water supplied into the core 2 is measured by the core coolant flow rate measuring device 20. The core coolant flow rate measuring device 20 has pressure guiding pipes 21 and 22, a differential pressure detector 23, a flow rate calculator 24, and a display device 25. Impulse tube 21
And 22 are connected to the differential pressure detector 23. The pressure guide tubes 21 and 22 are provided in an annular region 27 formed between the outer side and the side surface of the control rod guide tube 10 located at the outermost periphery of the group of the control rod guide tubes 10 and the inner surface of the shroud 8 in the reactor pressure. It is inserted through the bottom of the container 1. In FIG. 2, a circle 28 indicated by a chain double-dashed line is obtained by connecting the outer side surfaces of the control rod guide tube 10 located at the outermost circumference. The annular region 27 is formed between the circle 28 and the shell 9. The pressure guiding tube 21 connects the shroud 9 to the shroud 9
The pressure detecting end 2 of the pressure guiding pipe 21.
1A is open to the downcomer flow path 11 at a position above the internal pump 12. The pressure detecting end 22 </ b> A of the pressure guiding tube 22 opens in the annular region 27 at a position above the opening 16. Although not shown, the pressure guiding tubes 21 and 2
2 is supported on the inner surface of the shroud 9 by supporting members at several positions in the axial direction thereof. As shown in FIG. 2, the paired pressure guiding pipes 21 and 22 are provided at four positions in the circumferential direction of the shroud 9 corresponding to the four internal pumps. Four differential pressure detectors 23 are provided, and a pair of pressure guide tubes 21 and 22 are connected to each differential pressure detector 23. The four differential pressure detectors 23 are connected to one flow rate calculator 24. The pressure detecting end 21A of the pressure guiding pipe 21 and the pressure detecting end 22A of the pressure guiding pipe 22 are, as shown in FIG. 3 (a view taken along the line III-III in FIG. 2), the axial center of the internal pump 12 or It is arranged so as to coincide with the extension line of the axis. The pressure detection end 21A is connected to the internal pump 1 from the upper end of the internal pump 12.
The two diff users are arranged at positions more than twice the diameter d (FIG. 4).

The flow rate calculator 24 stores characteristics showing the relationship between the differential pressure ΔP _T and the flow rate Q _T as shown in FIG. The characteristics shown in FIG. 5 are obtained in advance by a test device, and the internal pump 6 is connected to the inlet pipe and the outlet pipe of the test device so that the internal pump is supplied from the inlet and the outlet of the internal pump, respectively. The relationship between the pressure difference (differential pressure ΔP _T ) at the position twice the diameter of the Diff user and the discharge flow rate (Q _T ) of the internal pump measured by the flow meter installed on the outlet side pipe. Shows.

The pressure guiding pipe 21 detects pressure at a position upstream of the internal pump 12 described above at the pressure detection end 21A, and the pressure guiding pipe 22 is downstream of the internal pump 12 described above at the pressure detection end 22A. To detect the pressure. The differential pressure detector 23 obtains the differential pressure of each pressure measured by the pressure guiding tube 21 and the pressure guiding tube 22. The differential pressures obtained by the four differential pressure detectors 23 (the differential pressures corresponding to the four internal pumps 12 as described above) are calculated by the flow rate calculator 24.
Entered in. The flow rate calculator 24 calculates the average value of the four input values of the differential pressure, and based on this average value of the differential pressure, the fifth value is calculated.
The corresponding flow rate Q _T is determined from the characteristics shown in the figure. The flow rate Q _T thus obtained corresponds to one internal pump 12. Accordance connexion, performing the calculation of 10Q _T flow calculator 24 for determining the core coolant flow rate is by connexion supplied to tens internal pumps 12. The obtained core coolant flow rate is displayed on the display device 25. The flow rate calculator 24 can also determine the discharge flow rates of the corresponding four internal pumps 12 based on the four differential pressures detected in the four pairs of pressure guiding pipes 21 and 22. By thus determining the discharge flow rates corresponding to the four internal pumps 12, it is possible to know the circumferential flow rate distribution of the shroud 8 flowing into the lower plenum 15 from the downcomer flow passage 11.

Since the pressure detection end 21A is arranged on the upstream side of the inlet of the internal pump 12 by more than twice the diameter of the Diffuser, a swirling flow or the like generated near the inlet of the internal pump 12 as shown in FIG. The pressure on the upstream side of the internal pump 12 can be accurately measured without being affected by the turbulence of the flow. The cooling water discharged from the internal pump 12 flows into the lower plenum 15 through the openings 16 formed between the shroud legs 9, so that swirling occurs near the discharge port of the internal pump 12 shown in FIG. Disturbances in the flow disappear. Therefore, the pressure detection end 22A is located downstream of the opening 16 in the lower plenum 1.
By providing the inside of 5, it is possible to accurately measure the pressure on the downstream side of the internal pump 12. In particular, by disposing the pressure detecting end 22A in the annular region 27, the pressure detecting end 22A accurately measures the pressure in the lower plenum 15 without being affected by the turbulence of the cooling water flow due to the control rod guide tube 10. can do. In this embodiment as described above, the pressure difference between the inlet side and the outlet side of the internal pump 12 can be accurately obtained, and the core cooling water flow rate can be accurately obtained.

In this example, the differential pressure ΔP _T and the flow rate Q obtained by the test apparatus were used.
_The flow rate of the core cooling water can be obtained by substantially using the characteristic indicating the relationship with _T as it is.

Even if the pipe connected to the water level measurement nozzle 12 is attached to the differential pressure detector 23 instead of the pressure guiding pipe 21, the effects of the above-described embodiment can be obtained.

By providing each of the ten internal pumps 12 with a pressure detecting pipe formed by combining the pressure guiding pipe 21 and the pressure guiding pipe 22, the core coolant flow rate can be measured with higher accuracy.

〔The invention's effect〕

According to the present invention, the first pressure detection port of the first pressure detection pipe is
It is arranged at a position more than twice the diameter of the diffuser of the internal pump on the upstream side of the internal pump to detect the pressure in the descending flow passage, and the second pressure detection port of the second pressure detection pipe is in the shroud. Is located below the core of the control rod guide pipe in the region formed between the outermost control rod guide pipe and the shroud, and guides the coolant discharged from the internal pump into the shroud. Since it is located above the upper end of the shroud opening, the accuracy of the core coolant flow rate can be measured the next time, which makes it possible to improve the safety of the core and to consider the coolant flow rate error. The power loss due to flowing more than necessary can be reduced, and the economic efficiency is improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of a core coolant flow rate measuring apparatus which is a preferred embodiment of the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. Fig. 2 is a view taken along the line III-III, Fig. 4 is an enlarged view of the vicinity of the internal pump of Fig. 1, Fig. 5 is a characteristic diagram showing the relationship between differential pressure and flow rate, and Fig. 6 is the vicinity of the internal pump. It is explanatory drawing which shows the flow state. 1 ... Reactor pressure vessel, 2 ... Reactor core, 8 ... Shroud, 11 ... Downcomer passage, 12 ... Internal pump, 15 ... Lower plenum, 16 ... Opening, 20 ...
Core coolant flow rate measuring device 21, 22 ... Pressure guiding tube, 21
A, 21B ... Pressure detection end.

Claims (1)

[Claims] 1. A nuclear reactor vessel, a shroud provided in the nuclear reactor vessel and surrounding a reactor core, and the same circumference at the bottom of an annular downward flow path formed between the shroud and the nuclear reactor vessel. In a device for measuring a core coolant flow rate of a nuclear reactor having a plurality of internal pumps arranged at equal intervals, when a circle in which the plurality of internal pumps are arranged is divided into four quadrants. In each quadrant, the pressure at the following two positions in at least one position is detected and the differential pressure is obtained, and (a) the influence of the pressure fluctuation due to the turbulent flow caused by the internal pump on the upstream side of the internal pump. (B) Position between the control rod guide pipe located at the outermost periphery and the shroud among the control rod guide pipes arranged in the shroud below the core in each quadrant Request A core coolant flow rate measuring device, wherein the core coolant flow rate is obtained based on the average value of the differential pressures.