Control rod insertion test device and control rod insertion test method

Abstract

To provide a control rod insertion test device that can perform a control rod insertion test relatively easily while considering pressure losses in scram piping in a control rod drive system that drives two or more control rods with a single hydraulic control unit.SOLUTION: A control rod insertion test device includes: a hydraulic control unit; scram piping which is connected to the hydraulic control unit; a control rod drive device connected to the scram piping; and a control rod inserted into a container when a piston of the control rod drive device moves due to the water pressure of drive water transmitted by the hydraulic control unit. The scram piping is branched so as to connect the single hydraulic control unit with the multiple control rod drive devices. During the control rod insertion test, the pressure loss in the branched scram piping is adjusted to a predetermined value.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to the configuration of a control rod insertion test apparatus and a test method for evaluating the insertability of control rods in nuclear reactors, and in particular to a technology that is effective when applied to a control rod drive system in which multiple control rod drive devices are connected to one hydraulic control unit. [Background technology]

[0002] Boiling water reactors are designed to insert control rods into the reactor core and automatically shut down in the event of a large earthquake. During an earthquake, the fuel assemblies placed in the reactor core vibrate in a bow shape, causing the control rods to come into contact with the fuel assemblies, which can result in a delay in control rod insertion time compared to when there is no earthquake. For this reason, control rod insertion is one of the important evaluation items in the seismic design of nuclear power generation facilities.

[0003] On the other hand, in order to reduce the construction costs of nuclear power plants, an improved control rod drive mechanism that reduces the number of hydraulic control units that drive the control rods is being considered. One example of an improved control rod drive mechanism is a system in which two control rod drive mechanisms are connected to one hydraulic control unit via scram piping, and one hydraulic control unit drives two control rod drive mechanisms.

[0004] Background art in this technical field includes, for example, technology such as that in Patent Document 1. Patent Document 1 discloses "a control rod insertion seismic test device including a water pressure control unit, a plurality of scram pipes connected downstream of the water pressure control unit, a control rod drive mechanism connected downstream of some of the scram pipes, a flow control valve connected downstream of the remaining scram pipes, and a control device that controls the flow control valve." [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-114440 A Summary of the Invention [Problem to be solved by the invention]

[0006] When two or more control rods are connected to one hydraulic control unit, there is a possibility that differences in the insertion times of those control rods during scram (emergency shutdown) may occur. This difference is thought to be caused by differences in the mass of the control rods and differences in pressure loss in the scram piping.

[0007] In an actual reactor, pressure loss has a certain range depending on the length of the scram piping, the angle of the bend, the number of bends, etc., so in order to evaluate the scram performance in more detail using a test device, it is effective to confirm the effect of differences in pressure loss.

[0008] However, if the pressure loss range to be confirmed is set broadly, the number of test cases will naturally increase. In addition, the test conditions will become more complex as the number of control rods connected to one hydraulic control unit increases. This means that the labor required to adjust the pressure loss in the scram piping during control rod insertion tests and to replace the equipment required for such adjustments will become enormous, and an efficient testing method is therefore required.

[0009] In the above Patent Document 1, the pressure loss difference in the scram piping as described above is not taken into consideration, and there is room for improvement.

[0010] Therefore, an object of the present invention is to provide a control rod insertion test device and a test method thereof that enable a control rod insertion test to be performed relatively easily while taking into account the pressure loss in the scram piping in a control rod drive system in which two or more control rods are driven by one hydraulic control unit. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention provides a hydraulic control unit, a scram piping connected to the hydraulic control unit, a control rod drive mechanism connected to the scram piping, and a control rod that is inserted into a vessel when a piston of the control rod drive mechanism moves due to the hydraulic pressure of driving water transmitted from the hydraulic control unit, wherein the scram piping is branched so as to connect one of the hydraulic control units to a plurality of the control rod drive mechanisms, and during a control rod insertion test, the pressure loss of the branched scram piping is adjusted to a predetermined value.

[0012] The present invention also provides a control rod insertion test method using a control rod insertion test apparatus having scram piping branched to connect one hydraulic control unit and a plurality of control rod drive devices, comprising the steps of: (a) performing a control rod insertion analysis before a control rod insertion test; (b) determining a combination of pressure losses in the scram piping for a pressure loss investigation range of the branched scram piping based on the insertion analysis performed in the step (a); and (c) setting the pressure loss of the branched scram piping to the combination of pressure losses in the scram piping determined in the step (b) during a control rod insertion test. Effect of the Invention

[0013] According to the present invention, it is possible to realize a control rod insertion test device and a test method thereof that enable a control rod insertion test to be performed relatively easily while taking into account the pressure loss in the scram piping in a control rod drive system in which two or more control rods are driven by one hydraulic control unit.

[0014] This enables efficient control rod insertion testing.

[0015] Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0016] [Figure 1]FIG. 1 is a diagram showing a schematic configuration of a control rod insertion test device according to a first embodiment of the present invention. [Diagram 2] 2 is a flowchart showing a control rod insertion test method according to the first embodiment of the present invention. [Diagram 3] FIG. 2 is a diagram showing an image of pressure loss in the scram piping and control rod insertion time according to the first embodiment of the present invention. [Figure 4] FIG. 11 is a diagram showing an image of pressure loss in scram piping and control rod insertion time according to Example 2 of the present invention. [Diagram 5] FIG. 11 is a diagram showing an image of pressure loss in scram piping and control rod insertion time according to Example 3 of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same components are designated by the same reference numerals, and detailed description of overlapping parts will be omitted.

[0018] In addition, the present invention is applicable to cases where two or more control rods are driven by one hydraulic control unit, but for ease of explanation, the following description will be given using as an example a control rod drive system in which two control rods are driven by one hydraulic control unit.

[0019] To facilitate understanding of the present invention, a detailed description of a boiling water reactor and a control rod insertion test will first be provided.

[0020] In control rod insertion tests in nuclear reactors, performance verification and life tests against required specifications are generally carried out on the equipment that makes up the control rod insertion system, such as the hydraulic control unit, control rod drive mechanism, and scram piping, by connecting them in the same manner as in the actual equipment.

[0021] Boiling water reactors are equipped with a control rod drive mechanism to drive the control rods inside the reactor. The control rod drive has two functions: one is the drive function for controlling the reactor's power output and reactivity, and the other is the function to rapidly insert the control rods into the reactor core when an emergency shutdown of the reactor is required, such as in the case of an earthquake, i.e., the scram function.

[0022] To achieve a scram, high-pressure water that has been stored in advance in a hydraulic control unit is generally used. High-pressure nitrogen gas is stored in the hydraulic control unit, and by releasing it all at once, the piston of the accumulator connected to the nitrogen gas container is pushed out, generating high-pressure water, which travels from the hydraulic control unit through the scram piping to the control rod drive mechanism. The high-pressure water pushes up the piston in the control rod drive mechanism, and the control rod connected to the piston is inserted into the reactor.

[0023] The hydraulic control unit and scram piping, control rod drive mechanism, control rods, etc. related to scram are called the control rod drive system. In current advanced boiling water reactors, a control rod drive system that sends high-pressure water to two control rod drive mechanisms per hydraulic control unit, and a control rod drive system that sends high-pressure water to one control rod drive mechanism per hydraulic control unit are mixed.

[0024] Scram is one of the safety features of a nuclear reactor, and tests are being conducted to evaluate the scram performance of a control rod drive system in which one hydraulic control unit, similar to that of a real reactor, sends high-pressure water to two control rod drive mechanisms.

[0025] There are several items to check in scram performance, one of which is to confirm that the control rod insertion time is within a target time.

[0026] For example, by simulating the high temperature and pressure conditions inside an actual reactor, which corresponds to the most conservative conditions, setting the pressure loss in the scram piping to its maximum value, the accumulator pressure in the hydraulic control unit to its minimum value, and setting both control rods to their initial state as fully withdrawn, it can be confirmed that the insertion time of the control rods is within the target time with a sufficient margin, thereby confirming that scram performance is fully guaranteed.

[0027] Although it has been confirmed that current nuclear reactors are sufficiently safe, there is a demand for further improvements in safety. EXAMPLES

[0028] First Embodiment A control rod insertion test apparatus and a control rod insertion test method according to a first embodiment of the present invention will be described with reference to FIGS.

[0029] Fig. 1 is a diagram showing a schematic configuration of a control rod insertion test apparatus according to this embodiment. Fig. 2 is a flowchart showing a control rod insertion test method according to this embodiment using the control rod insertion test apparatus shown in Fig. 1. Fig. 3 is a diagram showing an image of pressure loss in the scram piping and control rod insertion time.

[0030] As shown in FIG. 1, the control rod insertion test apparatus of this embodiment mainly comprises a test vessel 101, two sets of simulated fuel assemblies 102 contained in the test vessel 101, two control rod guide tubes 103 connected to the two sets of simulated fuel assemblies 102, two control rods 104 respectively arranged inside each control rod guide tube 103, two control rod drive mechanisms 105 connected to the two control rods 104, a heater 106 and a pump 107 connected to the test vessel 101, a nitrogen gas vessel 108 filled with nitrogen gas, an accumulator (pressure storage vessel) 109, scram piping 110, 110a, 110b, a scram valve 111, two valves 112a, 112b, and a control unit 113 that controls the scram valve 111 and the valves 112a, 112b.

[0031] Two sets of mock fuel assemblies 102 are contained inside a liquid-filled test vessel 101, and the test vessel 101 is equipped with a control rod guide tube 103 and a control rod drive mechanism 105 that inserts control rods 104 in the control rod guide tube 103 between the mock fuel assemblies 102.

[0032] A piston (not shown) in the control rod drive mechanism 105 moves due to the hydraulic pressure of the driving water transmitted from a hydraulic control unit (nitrogen gas container 108 and accumulator 109), thereby inserting the control rod 104 into the container (dummy fuel assembly 102 in FIG. 1).

[0033] A heater 106 and a pump 107 are connected to the test vessel 101, and the liquid in the test vessel 101 is heated and pressurized, thereby making it possible to simulate the temperature and pressure in a nuclear reactor.

[0034] A hydraulic control unit consisting of a nitrogen gas container 108 storing pressurized nitrogen gas and an accumulator 109 is connected to the control rod drive mechanism 105 via scram piping 110. The scram piping 110 branches into scram piping 110a and scram piping 110b along the way, and is connected to each of the control rod drive mechanisms 105.

[0035] Between the scram piping 110 and the control rod drive mechanism 105, a scram valve 111 and valves 112a, 112b for adjusting the pressure loss in the scram piping 110a and the scram piping 110b are arranged.

[0036] Using FIG. 2, we will explain a method for efficiently conducting a confirmation test for the control rod insertion time.

[0037] First, in step S201, the investigation range of the pressure loss in the scram piping 110a, 110b is set in advance.

[0038] Next, in step S202, an analysis is performed to evaluate the control rod insertion time, etc., for the control rod drive system having such scram piping 110a, 110b.

[0039] In this analysis, in addition to analysis using an analytical model that uses a computer to simulate the dynamic water pressure changes in the driving water of the control rod drive system, simple desk calculations can also be used.

[0040] Thereafter, in step S203, the pressure losses in the scram piping 110a, 110b in the control rod insertion test are set based on the analysis results in step S202.

[0041] Then, in step S204, the pressure loss in the scram piping 110a, 110b of the control rod insertion test device is adjusted to a set value, and a control rod insertion test is carried out.

[0042] In step S201, any range can be set as the investigation range of the pressure loss in the scram piping 110a, 110b.

[0043] Examples of the investigation range for the pressure loss in the scram piping 110a, 110b include a range set based on the pressure range of the scram piping in an actual boiling water reactor, and a pressure loss range of the scram piping estimated from the distance between the water pressure control unit room and the control rod drive mechanism of the boiling water reactor.

[0044] An example of a method for setting the pressure loss in the scram piping in a control rod insertion test will be described with reference to Fig. 3. Fig. 3 shows an example in which the control rod insertion time is confirmed by analysis for a survey range 201 of the pressure loss in the scram piping.

[0045] In the graph 301, the pressure loss in the two scram pipes 110a, 110b and the control rod insertion time are plotted on the axis.

[0046] In a control rod insertion test, if the pressure loss in the scram piping is set so as to obtain the slowest insertion time and the control rod insertion time is checked, then an evaluation will be made on the safe side. Therefore, if there is a point 302 in graph 301 where the control rod insertion time is maximum, then the pressure loss in the scram piping can be set using valves 112a, 112b of the control rod insertion test equipment so as to obtain pressure losses A, B in the scram piping at that point.

[0047] It should be noted that the creation of graph 301 is not necessarily required for the present invention, and the axis of the graph showing the pressure loss in the scram piping may be an indicator equivalent to the pressure loss in the scram piping, such as the length of the scram piping or the fluid resistance coefficient. The pressure loss in the scram piping used in the control rod insertion test may be set under the same concept in a chart format other than graph 301.

[0048] As described above, the control rod insertion test equipment of this embodiment includes a hydraulic control unit (nitrogen gas container 108 and accumulator 109), scram piping 110, 110a, 110b connected to the hydraulic control unit, a control rod drive mechanism 105 connected to the scram piping, and a control rod 104 that is inserted into the container (mock fuel assembly 102 in Figure 1) by the piston of the control rod drive mechanism 105 moving due to the hydraulic pressure of the driving water transmitted from the hydraulic control unit, and the scram piping is branched so as to connect one hydraulic control unit and multiple control rod drive mechanisms 105, and in the control rod insertion test, the pressure loss of the branched scram piping 110, 110a, 110b is adjusted to a predetermined specified value.

[0049] In addition, an insertion analysis of the control rod 104 is performed before the control rod insertion test, and the insertion analysis is used to determine the combination of pressure losses in the scram piping that results in the slowest control rod insertion time within the pressure loss investigation range of the branched scram pipings 110, 110a, and 110b, and the pressure loss in the scram piping during the control rod insertion test is set to the determined combination of pressure losses in the scram piping.

[0050] This makes it possible to realize a control rod insertion test apparatus and a test method thereof that enable a control rod insertion test to be performed relatively simply while taking into account the pressure loss in the scram piping, thereby enabling an efficient control rod insertion test. EXAMPLES

[0051] Second Embodiment With reference to FIG. 4, a control rod insertion test apparatus and a control rod insertion test method according to a second embodiment of the present invention will be described.

[0052] FIG. 4 is a diagram showing an image of pressure loss in the scram piping and control rod insertion time in this embodiment, which corresponds to a modified example of the first embodiment (FIG. 3).

[0053] In the graph 401, the range in which the control rod insertion time is later than time T1 is set as the pressure loss range 402 in the scram piping.

[0054] In a control rod insertion test, a safe evaluation can be performed by setting the pressure loss in the scram piping so that the insertion time is delayed and checking the control rod insertion time, so the pressure loss in the scram piping can be set using the valves 112a, 112b of the control rod insertion test equipment so as to cover the pressure loss range 402 in the scram piping including the point at which the insertion time is slowest.

[0055] At this time, since the pressure loss in the scram piping can only be set discretely in the control rod insertion test equipment, it is sufficient to set the pressure loss in the scram piping at intervals sufficient to grasp the characteristics within the pressure loss range 402 of the scram piping.

[0056] As described above, in the control rod insertion test apparatus of this embodiment, an insertion analysis of the control rod 104 is performed before the control rod insertion test, and the control rod insertion time is obtained by the insertion analysis within the pressure loss investigation range of the branched scram pipings 110, 110a, 110b, and a combination of pressure losses in the scram piping associated with the control rod insertion time within a certain range from the maximum value of the control rod insertion time is obtained, and the obtained combination of pressure losses in the scram piping is set as the pressure loss in the scram piping during the control rod insertion test. EXAMPLES

[0057] Third Embodiment With reference to FIG. 5, a control rod insertion test apparatus and a control rod insertion test method according to a third embodiment of the present invention will be described.

[0058] FIG. 5 is a diagram showing an image of pressure loss in the scram piping and control rod insertion time in this embodiment, which corresponds to yet another modified example of the first embodiment (FIG. 3).

[0059] In the graph 501, since the investigation range 201 of the pressure loss in the scram piping is large, there is a region where the control rod insertion time is equal to or longer than the target time T2.

[0060] In this case, in the control rod insertion test, a safe evaluation is possible by setting the pressure loss in the scram piping so that the insertion time is delayed and checking the control rod insertion time, so the pressure loss in the scram piping can be set using the valves 112a, 112b of the control rod insertion test equipment so as to cover the frame in which the control rod insertion time is T2 and the pressure loss range 502 in the scram piping that is within the region of the control rod insertion time T3 that is shorter than T2.

[0061] At this time, since the pressure loss in the scram piping can only be set discretely in the control rod insertion test equipment, it is sufficient to set the pressure loss in the scram piping at intervals sufficient to grasp the characteristics within the pressure loss range 502 of the scram piping.

[0062] As described above, in the control rod insertion test apparatus of this embodiment, an insertion analysis of the control rod 104 is performed before the control rod insertion test, and the control rod insertion time is calculated by the insertion analysis for the pressure loss investigation range of the branched scram pipings 110, 110a, 110b. A combination of pressure losses in the scram piping that correlates the control rod insertion time with the control rod insertion time within a certain range from the target time is calculated, and the calculated combination of pressure losses in the scram piping is set as the pressure loss in the scram piping during the control rod insertion test.

[0063] The present invention is not limited to the above-described embodiments, and includes various modified examples. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the configurations described. It is also possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace a part of the configuration of each embodiment with another configuration. [Explanation of symbols]

[0064] 101...Test container 102…Simulated fuel assembly 103...Control rod guide tube 104…Control rod 105...Control rod drive mechanism 106…Heater 107…Pump 108...Nitrogen gas container 109…Accumulator 110, 110a, 110b…Scram piping 111…Scram valve 112a, 112b... Valve 113...Control unit 201…Scope of investigation into pressure loss in scram piping 301,401,501…Graph 302: Maximum control rod insertion time of graph 301 402…Pressure loss range of scram piping 502...Scram piping pressure loss range.

Claims

1. A water pressure control unit; A scram pipe connected to the water pressure control unit; A control rod drive mechanism connected to the scram piping; a control rod that is inserted into a vessel by a piston of the control rod drive mechanism being moved by the hydraulic pressure of the driving water transmitted from the hydraulic control unit, the scram piping is branched so as to connect one of the water pressure control units to a plurality of the control rod drive mechanisms, 2. A control rod insertion test apparatus comprising: a control rod insertion test device for adjusting a pressure loss in the branched scram piping to a predetermined value during the control rod insertion test.

2. The control rod insertion test apparatus according to claim 1, Conducting an insertion analysis of the control rod before a control rod insertion test; A combination of pressure losses in the scram piping that results in the slowest control rod insertion time is obtained by the insertion analysis within the pressure loss investigation range of the branched scram piping; A control rod insertion test device, characterized in that the pressure loss in the scram piping during the control rod insertion test is set to the combination of the pressure losses in the scram piping obtained above.

3. The control rod insertion test apparatus according to claim 1, Conducting an insertion analysis of the control rod before a control rod insertion test; The insertion analysis is used to determine a control rod insertion time for a pressure loss investigation range of the branched scram piping; A combination of pressure losses in the scram piping associated with the control rod insertion time within a certain range from a maximum value of the control rod insertion time is obtained; A control rod insertion test device, characterized in that the pressure loss in the scram piping during the control rod insertion test is set to the combination of the pressure losses in the scram piping obtained above.

4. The control rod insertion test apparatus according to claim 1, Conducting an insertion analysis of the control rod before a control rod insertion test; The insertion analysis is used to determine a control rod insertion time for a pressure loss investigation range of the branched scram piping; A combination of pressure losses in the scram piping that is associated with the control rod insertion time within a certain range of the reference time is obtained; A control rod insertion test device, characterized in that the pressure loss in the scram piping during the control rod insertion test is set to the combination of the pressure losses in the scram piping obtained above.

5. A control rod insertion test method using a control rod insertion test device having scram piping branched to connect one water pressure control unit and a plurality of control rod drive devices, comprising: (a) performing a control rod insertion analysis before a control rod insertion test; (b) determining a combination of pressure losses of the scram piping based on the insertion analysis performed in the (a) step, within the pressure loss investigation range of the branched scram piping; (c) setting the pressure loss of the branched scram piping to the combination of the pressure loss of the scram piping obtained in the (b) step during a control rod insertion test; A control rod insertion test method comprising the steps of:

6. The control rod insertion test method according to claim 5, A control rod insertion test method, characterized in that in the step (b), a combination of pressure losses in the scram piping that results in the slowest control rod insertion time is obtained.

7. The control rod insertion test method according to claim 5, In the step (b), a control rod insertion time is calculated for a pressure loss investigation range of the branched scram piping based on the insertion analysis performed in the step (a); A control rod insertion test method comprising: determining a combination of pressure losses in a scram piping related to the control rod insertion time within a certain range from a maximum value of the control rod insertion time.

8. The control rod insertion test method according to claim 5, In the step (b), a control rod insertion time is calculated for a pressure loss investigation range of the branched scram piping based on the insertion analysis performed in the step (a); A control rod insertion test method, comprising: determining a combination of pressure losses in a scram piping that is associated with a control rod insertion time within a certain range of a reference time from the reference time.

Images