JPS6156800B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a control rod position detection device for a nuclear reactor for determining the position of a control rod in a nuclear reactor. In a boiling water reactor (BWR), multiple fuel assemblies are housed within the reactor core. , which regulates the neutron flux within the nuclear reactor. This control rod insertion/removal is performed by operating a hydraulic drive system based on commands from the operator's switch operation, and as the control rod is inserted, the neutron flux decreases, and conversely, as the control rod is withdrawn, the neutron flux decreases. The bundle is configured to increase. During actual reactor operation, control rod operating procedures are predefined in order to prevent fuel damage due to local concentration of neutron flux, and operators must Operate the control rods according to the specified operating procedure while checking the position of the control rods. The position of each control rod is detected and processed by a control rod position detection device, and based on the position information obtained from this, the operator operates the control rod according to the prescribed procedure using operating procedure monitoring equipment such as a computer. Control rod operations are monitored, and if the operating procedures are violated, control rod operation is prohibited. If a nuclear reactor is operated based on incorrect positional information about the reactor's control rods, there is a risk that it will lead to uneven consumption of nuclear fuel, reduced operational efficiency, and even a serious accident. Therefore, it is necessary to accurately detect the position of the control rod and to promptly detect erroneous position information. Figure 1 is a schematic diagram of the BWR control rod position detection mechanism. The nuclear reactor 101 is housed in a reactor containment vessel 102, and a plurality of fuel assemblies 1 in the reactor 101
A control rod 104 is inserted between the two. In reality, there are over a hundred control rods, but only one control rod is illustrated here. There is a control rod drive mechanism 105 at the bottom of the control rod 104, and the control rod 104 is inserted into the reactor core by pushing up the hydraulic piston 106 therein from below.
The control rod 104 is pulled out by pushing down the control rod 104 from above. Inside the control rod drive mechanism, there is an index tube 107 as a movable part and a position detection probe 108 as a fixed part. Information regarding the vertical position of the control rod is transmitted from the position detection probe 108 to the control rod position detection device 100 as probe data 109. sent and processed. FIG. 2 is a detailed view showing the position detector portion within the control rod drive mechanism of the BWR of FIG. 1. The position detector part is the index tube 10.
7. Consists of a collect finger 110 and a position detection probe 108. index tube 1
07 is movable, and when raised in the direction of the illustrated arrow in FIG. 2, the control rod connected to the upper part is inserted into the reactor core. The control rod 104 is inserted into a notch 111 on the side of the index tube 107.
is fixed by being hooked onto the collect finger 110. The position detection probe 108 is fixed and has reed switches 112 to 116 incorporated therein. The vertical position of control rod 104 is detected by actuation of reed switches 112-116 in position probe 108 by magnet 117 incorporated in index tube 107. From the fully inserted (FI) position to the fully withdrawn (F.
O) Reed switches 112-115 are provided so that the notches between the positions correspond to even values from 00 to 48. Furthermore, a reed switch 116 is installed to detect overtravel (OT), which means a state in which the control rod 104 and the control rod drive mechanism are disconnected. These reed switches 112-1
16 are connected in a matrix as shown in Fig. 3, and depending on the operation of the reed switch, one of the signal lines of the vertical axis (V ₁ to V ₃₂ ) and the horizontal axis (H ₁ to _{H 16} ) is connected. The electric potential changes, and the vertical position of the actuated reed switch, ie, the control rod, is detected by this electric potential change. For example, the position detection probe rises and the position detection reed switch 11 is attached to the magnet 117.
When the reed switch 115 and the reed switch 115 for detecting the fully withdrawn position reach each other, (FO) and (48) shown in FIG. 3 are turned on. Note that the reed switches at odd number (ODD) positions from 01 to 47 are all connected in parallel. Table 1 shows the correspondence between the intersection points of the vertical and horizontal axes where the potential changes and the control rod positions. In Figure 1

[Table] As shown, the full insertion (FI) position and the 00 position, and the full withdrawal (FO) position and the 48 position are each at the same vertical position. In Figure 3, when fully inserted, V ₁ and
The potentials of V ₃₂ and H ₁ and H ₄ change simultaneously, and the potentials of V ₁ and V ₂ and H ₁ and H ₈ change simultaneously during full withdrawal. Therefore, code conversion is performed as shown in Table 2 for the horizontal axis and Table 3 for the vertical axis.

【table】

【table】

[Table] In Tables 2 and 3, "1" means that a potential change was detected in the corresponding signal line,
“0” means that no potential change was detected. Thus, the horizontal signal lines shown in Table 2
Any one of H ₀ to _{H 16} becomes “1”,
In addition, it becomes a meaningful code only when any one of the vertical signal lines V ₀ to _{V 33} shown in Table 3 becomes “1” (hereinafter, the signal of the signal line that becomes “1” level will be referred to as “1”). (This is called a valid signal, and other signals such as H ₃ , H ₆ , V ₅ are called invalid signals). FIG. 4 is a block diagram of a code conversion circuit that takes in a horizontal signal H _i and a vertical signal V _i and performs code conversion. _Each signal of the horizontal signal lines H ₁ to _{H 16} shown in FIG.
V ₃₂ is taken into the vertical axis decoder 2. The water axis decoder 1 receives effective signals H ₀ , H ₁ , H ₂ , H ₄ , H ₅ ,
The vertical axis _decoder 2 outputs valid signals _{V 0 ,} V ₁ , _{V 2 , V 3} , V ₄ ,
It outputs V ₈ , V ₁₆ , V ₃₂ , V ₃₃ and an invalid signal (N _SV ). The effective signals outputted from each decoder are outputted simultaneously from any one of the eight rows in Tables 2 and 3. The invalid signals _NSV and _NSH of both decoders are taken into the FAULT signal generation circuit 3,
It is determined whether or not two "1" levels occur simultaneously in each row of the contents of Tables 2 and 3, and if two "1" levels exist simultaneously, a FAULT signal is output. In this case, the horizontal side and vertical side are each output independently. FIG. 5 is a block diagram of the notch number generator.
The notch number generating section corresponds to the part that converts the combination of horizontal and vertical axis signal lines after code conversion into the control rod position, that is, the number of notches. The notch number generation section includes a notch number generation circuit 4, a 10th notch storage register 5, and a 1st notch storage register 6. The 10th notch is stored in the 10th notch storage register 5, and the 1st notch is stored in the 1st notch storage register 6 using a BCD code. The notch number generating circuit 4 also has a function of outputting a number indicating a defective notch number, for example, "69" instead of the notch number, when a FAULT signal is generated. Table 4 shows the vertical position of the control rod 104 detected by the position detection device having the above function. In Table 4, the intersection of the horizontal side after code conversion and the vertical side after code conversion is shown as the vertical position of the control rod. Note that the position information marked with * in the table is determined by the FAULT signal shown in FIG. 5, and means erroneous control rod position information that is not actually defined. For example, if reed switches at positions "18" and "38" operate at the same time, the code will be converted to V ₂ and H ₅ and "08" will be displayed. The reason why such a FAULT signal is generated is that only invalid signals are detected independently in the horizontal and vertical directions, so even if two or more reed switches fail, they still operate normally. There is. Causes of reed switch failure include:
Contact welding may occur due to being placed in a high temperature atmosphere.

[Table] Yes. An object of the present invention is to provide a control rod position detection device for a nuclear reactor that detects simultaneous operation of two or more reed switches and improves reliability. The present invention eliminates the above-mentioned conventional drawbacks by providing invalid code detection means capable of detecting invalid codes generated by combining horizontal and vertical signals. FIG. 6 is a block diagram showing an embodiment of the present invention. The horizontal position signal H _i (H ₁ to _{H 16} ) and the vertical position signal V ₁ (V ₁ to _{V 32} ) are taken into decoders 1 and 2 as in the case of FIG. In addition, the valid signal H
_j and V _j are similarly outputted and sent to the notch number generation circuit 4. Similarly, invalid signals N _SH and N _SV are FAULT
A FAULT signal is generated by the signal generation circuit 3. Detection of invalid codes is performed by an invalid code detection circuit 7 which receives invalid signals N _SH and N _SV as input signals. FIG. 7 is a detailed block diagram of the embodiment of FIG. 6. The invalid code detection circuit 7 receives valid signals H ₀ , H ₅ , H ₉ , H 16 from the horizontal decoder 1, and inputs valid signals V ₀ , H ₁₆ from the vertical decoder 2, respectively.
Each of V ₁ , V ₃ , and V ₃₃ is input. These signals are selected because they correspond to the signal outputs marked with * in Table 4. Therefore, if the position signal marked with * can be deleted, the erroneous signal will not be output. Specifically, an invalid code detection signal is generated at the *marked part, and based on this signal,
When a FAULT signal is generated, the number "69" indicating a defect in the number of notches is generated as data to prevent the generation of erroneous position information. FIG. 8 is a circuit diagram of the invalid code detection circuit 7. H ₀ , H ₅ , H ₉ , H ₁₆ , V ₀ from each decoder,
Each output of V ₁ , V ₃ , and V ₃₃ is divided into four groups. In other words, an exclusive OR circuit 71 whose inputs are H ₀ and V ₀ , an exclusive OR circuit 72 whose inputs are H ₅ and V ₃₃ , and an exclusive OR circuit whose inputs are H ₉ and V ₃ . Configure each route of the sum circuit 73 and the AND circuit 74 which inputs H ₁₆ and V ₁ , detects the occurrence of the * mark signal, and generates an invalid code regardless of the output of any of the four routes. The output is taken out via an OR circuit (OR) 75. By providing such an invalid code detection circuit 7, the control rod position marked with *, which is the erroneous position information shown in Table 4, is detected as an invalid code, and a FAULT signal is generated. Therefore, the vertical position of the control rod as shown in Table 5 is detected. Fifth
As shown in the table, all *-marked information in Table 4 is replaced with "69" data, which means a defective number of notches, and it can be seen that the conventional drawbacks are solved. FIG. 9 is a block diagram showing another embodiment of the present invention. When vertical axis signals V ₁ , V ₂ , V ₄ , V ₈ , V ₁₆ , V ₃₂ are combined with horizontal axis signals H ₁ , H ₂ , H ₄ , H ₈ , H ₁₆
It is also possible to store the FAULT data (information marked with * in Table 4) in a storage element (for example, ROM 8).

[Table] As described in detail above, according to the embodiments of the present invention, it is possible to detect all failures that occur in the position detection probe in which two or more reed switches in an abnormal combination operate simultaneously, and to detect faulty control rods. Since position information is no longer given, great effects can be obtained in terms of reactor operation and safety. As is clear from the above, according to the present invention, it is possible to prevent the generation of erroneous control rod position information due to multiple operations of the detection switch.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the BWR control rod position detection mechanism, Figure 2 is a detailed front view of the position detection part of the mechanism in Figure 1, Figure 3 is a wiring diagram of the position detection reed switch, and Figure 4 is FIG. 3 is a block diagram of a code conversion circuit that processes the signal generated by the reed switch, FIG. 5 is a block diagram of the notch number generator, and FIG. 6 is a block diagram of an embodiment of the present invention.
FIG. 7 is a detailed block diagram of the embodiment shown in FIG.
The figure is a circuit diagram of the invalid code detection circuit 7, and FIG. 9 is a block diagram showing another embodiment of the present invention. 100... Control rod detection device, 105... Control rod drive mechanism, 107... Index tube, 108...
Position detection probe, 110...Collection finger,
111...Notch, 112...Full insertion position detection reed switch, 113, 114...Position detection reed switch, 115...Full extraction position detection reed switch,
116... Overtravel position detection reed switch, 1... Horizontal axis decoder, 2... Vertical axis decoder, 3... FAULT signal generation circuit, 4... Notch number generation circuit, 5, 6... Memory register, 7... Invalid code detection circuit, 8 …ROM.

Claims (1)

[Claims] 1. In a nuclear reactor control rod position detection device that detects the longitudinal position of a control rod in a nuclear reactor based on an opening/closing means that generates an output signal corresponding to the position, a horizontal axis decoder and a vertical axis decoder that output a valid signal and an invalid signal corresponding to an error position to each of the horizontal axis and vertical axis position signals generated in response to a change in the position of the control rod; and both decoders. an invalid code detection circuit that outputs an invalid code for a combination that generates an error position when each of the valid signals output from the above is combined; and an output of the invalid code detection circuit and the output from both of the decoders. A control rod position detection device for a nuclear reactor, comprising: an error signal generation circuit that outputs error position information based on both invalid signals.