JPS59216091A - Control system of control rod - 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]

[Technical Field of the Invention] The present invention relates to a control rod control system for a boiling water nuclear reactor. [Technical background of the invention and its problems]? The Li5 rising water reactor sea is equipped with a control rod withdrawal monitoring device 12 to monitor the power increase caused by control rod withdrawal 1- during power operation. In order to increase output, when a certain control rod is selected, a plurality of fixed in-core neutron detectors (hereinafter referred to as 0 and this selected L P RM
to take the average value of the signals from the control frame, and when that value exceeds the average value before withdrawal by a predetermined value, send a control rod withdrawal prevention signal to prevent withdrawal of the control frame, thereby preventing control rod withdrawal. From 1-, the increase in output is below a predetermined level.

[Equipped with a double press function. FIG. 1 is a diagram showing an example of the arrangement of L P RM in a conventional device C. As is clear from this figure, 1-1 the withdrawal control rod 1 selected as described above (IA in the figure is
2. Shows the state of the withdrawn control rod during scram. ), 16 LPIs (M, i.e., fixed in-reactor neutron detectors) are arranged in a lattice pattern C2, marked by a circle 2 and a triangle 3. Second self e
[has been. ) This I, PRM is divided into two systems, for example, the A system and the B system. Eight LPRMs are assigned to each system. The A and B systems have different signal intensities -
It has one characteristic of controlling persimmon pulling. The joint axis in Fig. 2 indicates the signal concealment of L P RM, and the horizontal axis indicates the control rod withdrawal position (with the withdrawal distance of the selected control rod, 0 points indicates the full insertion position, and the l unit moving to the right (the pull-out distance increases as the distance increases). The characteristics when all LPRMs are normal and both A and B systems are operating are shown in Figure 2 (a) and (b).
) as shown by the solid lines AI and Bl, the responses of both systems are shown by the dotted lines A2. It is faster compared to B2. If a perpendicular line is drawn from the intersection of the characteristic curves of solid lines Al and Bl and a preset withdrawal prevention level gauze L (indicated by a two-dot chain line), control rod withdrawal prevention positions al and bl are obtained. Therefore, the aforementioned control rod withdrawal prevention No. 1 is sent out from the thread of the A system or the B system that reaches the above-mentioned intersection earlier. By the way, the output of the LPRM varies depending on the control rod withdrawal. Among these variations (2), some are unfavorable from the point of view of preventing control rod withdrawal.For example, due to a malfunction, an extremely large output or a small output than the average value may occur when the control rod This is the second cause of erroneous pulling out of the control rod.
Bypassing or disabling M, the preferred LPR
C2 is configured to output a control rod withdrawal prevention signal based only on the output signal from M. Therefore, in some cases, one of the A and B systems may be completely C
Double passes may occur. This is what the A-system bypass or B-system bypass described in Table 1 C-U means. Table 1 When the system is bypassed, the response of the system is generally C2 worse than in the normal case, that is, when no bypass is performed. Among the broken LPRMs in the system, in Fig. 1, the LPRM that shows a good response is close to the withdrawn control rod 1.
If 2 or 3 is bypassed, the response will also be poor. This case is called a worst-case bypass. Table 1 shows the pull-out prevention positions in various cases, and this table (-
, m1n (al, bl) or min (ag
, bz) means to take the smaller value of al+b1 or the smaller value of "B+b2". Dotted lines A 2 and B 2 in Figure 2 (a) and (b)
The fc characteristic curve shown in FIG. 1 shows the worst case bypass characteristics of each group. As can be seen from Figure 2, during R bad bypass, the control rod pullout position moves to az for A system and to b2 for B system, and when normal! − The response state is considerably worse than that of In this way, in the conventional device, each group and (two specific LPs)
When the RM is bypassed, the response deteriorates, and an improvement has been desired. Further, in a nuclear reactor where high safety is required, the deterioration of response due to the bypass described above is undesirable because it reduces the safety margin. In the case of operation in which the control rods on the collar are operated at the same time, the number of L P RMs to be detected increases. For example, when operating four control rods at the same time, 16X4
= Detection of 64 LPRMs is required for control rod withdrawal monitoring, which complicates the configuration of the monitoring device. The purpose is to amend (a) and (b). (b) Doubling threads and certain LPRMs are bypassed and
, the response deteriorates and the amount of output increase increases. (b) When operating (withdrawing) a number of control rods at the same time,
The circuit for detecting changes in core status becomes complicated. Therefore, the monitoring thread becomes complicated. In other words, the control rod withdrawal monitoring device must not detect changes in the core state (local output) in the setting of (i?'F volume withdrawal length). The purpose is to ensure functionality. [Summary/Summary of the Invention] The misfire 14 includes a reactor core, a control rod that is pulled out and inserted into this reactor core, a control rod drive mechanism for this control rod, and this control f? ! flit, a control rod control device that controls the motion mechanism;
The control rod axial position detection device for the control rod, the L position detection device for the control rod axial direction, and the control rod control device receive signals from the control rod control device and transmit the control rod withdrawal prevention position signal to the control rod control device C.
Control rod withdrawal monitoring device for two people 6. In a control rod control system equipped with a control rod withdrawal monitoring device C and a process computer that inputs the axial power distribution of the adjacent reactor assembly, the control rod withdrawal monitoring device A target control rod selection circuit receives a control rod axial position signal from the rod axial position detection device and a control rod selection signal from the control rod controller, and a control rod 5 and two adjacent fuel assemblies to be extracted from the process computer. A characteristic conversion circuit that creates fr, valley pull length characteristics using the body's axial output distribution signal, and this characteristic conversion 1r! A control rod withdrawal prevention position that outputs a control rod withdrawal prevention position signal to the control rod control equipment, which is determined using the allowable withdrawal length characteristics from the L path and the withdrawal control rod axial position signal from the target control rod selection circuit. A control rod control system comprising a setting circuit. [Embodiment of Irradiation Ql] An embodiment of the present invention will be described with reference to the drawings below. FIG. 3 shows a control rod drive system for a boiling water reactor using the control rod withdrawal monitoring device 4 according to the present invention. In the interior 52 of the core 5 shown in FIG. 3, a large number of extraction control rods 1 as shown in FIG. 1 are stored. In the figure, the control rod that is not pulled out is omitted and not shown. The withdrawal control rod 1 is pulled out and inserted by a control rod drive mechanism 6 (2) provided below the reactor core 5. This control rod drive mechanism 6 is controlled by a control rod control equipment 7. The control equipment 7 inputs the control rod operation signal S1 and the control rod withdrawal/stop positioning signal S2, and outputs the control rod drive signal S.
3 and control rod selection signals 84, 84A. The control rod drive signal S3 is sent to the control rod drive mechanism 6C1, the control rod selection signal S4 is sent to the control rod withdrawal monitoring device 4, and the control rod selection signal S4A is sent to the process computer ill2. This control rod withdrawal monitoring device 4 detects the control rod axial position, the control rod axial position signal S5 sent from the detection device 10, and the axial direction of the fuel assembly 12 adjacent to the selected control rod sent from the process computer 11. The output distribution signal S6 and the control rod selection signal S4 from the control rod controller are inputted, and the control rod withdrawal prevention position signal S2 is outputted to the control rod control equipment 7. The process computer 11 inputs the control rod selection signal 84A sent from the control rod control device 7, and outputs an axial power distribution signal S6 of the fuel fruit assembly 12 that momentarily contacts the selected control rod. FIG. 4 shows in detail the structure of the control rod withdrawal monitoring device 4 according to the present invention shown in FIG. 3. In this FIG. 4, the target control rod selection circuit 8 is the control rod P4
Select the extraction control rod 1 according to the selection amount 84C, and o! The selected withdrawal control rod axial position signal 85A is sent to the control rod withdrawal prevention position setting circuit 9. 120 fuel assemblies 1 adjacent to the selective extraction control rod 1 sent out from the 13-process calculator 11 of the sweet erectile conversion circuit;
Using the directional output distribution signal S6, a permit withdrawal technique characteristic 1/hand is created, and this 6'[musket withdrawal length characteristic signal S7 is sent to the control rod withdrawal prevention position setting circuit 9. In this control σl 4ii3 withdrawal prevention position setting circuit 9, the allowable withdrawal length characteristic (that is, the relationship between the control rod initial axial position 1st P■ and the allowable withdrawal length ΔL) signal S7 and the withdrawal υ;
Using the axial position signal 85A, the Kyoya pulling technique ΔL is determined. Pull-out control side] Rod initial axial position signal S5
A and the allowable withdrawal length ΔL, a withdrawal prevention position is set, and this is sent to the control rod control device 7 as a withdrawal prevention position signal S2. The characteristic conversion circuit 131- has the basic allowable pull-out length characteristic 50 shown in FIG. 5i and the basic axial direction output distribution 6 shown in FIG.
0 is inside the paper, and these are used to determine the axial power distribution of the fuel assembly 12 adjacent to the extracted control rod 1.
The lp characteristic of the allowable pulling length of If PAB is the relative output, and the relative output in the axial direction of the welded fuel is PAc, then the pullout at f break is f!
Set with LB X PAB Ac. At other axial positions, the e' capacity pull-out length is determined in the same manner, and the allowable pull-out length characteristics of the pull-out control rod are created. The pull-out prevention position is set as a value obtained by subtracting the allowable pull-out length obtained from the above-mentioned allowable pull-out length characteristics (relationship between control rod initial axial position Pl and 11-Answer pull-out length ΔL) from the initial axial position. . In other words, if the position in the J4VI+ direction of the rod is "I+" and the rod pull-out length corresponding to this PI is △L, then the pull-out prevention position PB is set to be PB: PI-△L. In the control rod control system of the present invention configured as follows, 22 withdrawal control rods 1 are selected during output operation.When the control rod operation signal s1 is input to the control rod restraint device 7, the control rod withdrawal monitoring device A control rod selection signal S4 is sent to the target control rod selection circuit 8 of No. 4, and a control rod selection signal S4A of the process computer 11C is sent to the target control rod selection circuit 8.
Based on this control rod selection signal 84, a necessary extraction control rod 1 is selected, and an initial axial position signal S5 of the extraction control rod 1 is sent to the control rod extraction prevention position setting circuit 9. On the other hand, in the process computer l], the control rod selection signal S4A
Based on the axial power distribution No. 46 S6 of the fuel 12 adjacent to the withdrawn control rod 1, j! ilj ;j+3141
Pull-out monitoring device TS, 4 characteristic quick turn times kN113 to 2 speeds. In the characteristic conversion circuit 13, the axial output distribution signal 85
Based on this, the allowable withdrawal length characteristics of the withdrawal control rod 1 are created and the signal s7 is sent to the control rod withdrawal prevention position setting circuit 9I. This control persimmon pulling prevention position setting time ll'? -+9, based on the initial axial position signal S5, the initial axial position flP1 is set to the corresponding allowable pull-out length ΔL, and the control rod pull-out prevention position PB is determined from the initial axial position and the allowable pull-out length.
Set. This position is sent to the control rod control device 7 as the control rod withdrawal monitoring device S2. In the control rod control device 7, when the control rod operation signal S1 instructs the withdrawal beyond the withdrawal prevention position inputted by the control rod withdrawal prevention position signal s2, the control rod control device 7 performs the withdrawal at the prevention position of the withdrawal 1/f4 stop position nt signal s2. Control is performed to prevent withdrawal of the control rod. FIG. 9 shows the output increase characteristic when using the device of the present invention in comparison with the case of a conventional device. In the figure, PI indicates the initial axial position of the withdrawal control rod, and PI indicates the withdrawal prevention position when the device of the present invention is used or when the conventional device is used and the entire L I) RM is normal. The output increase amount is △
It is Pl. Further, P2 indicates a pull-out prevention position when a certain system and a secondary LPRM are bypassed in a conventional device, and the amount of increase in output at that time is ΔP2. Therefore, the amount of increase in output when using the device of the present invention is the same as the total L P of the conventional device regardless of the bypass state of the detector (-
As in the case where Rkl is normal, it can be reliably suppressed to a sufficiently low level. Two effects of changing the allowable pull-out length according to the initial axial position (g), which are features of the present invention, will be explained below. In the core of a boiling water reactor, the output in the axial direction is 4
5 is smaller at the top and bottom of the core and larger at the center of the core. Therefore, when the control rod is pulled out by the same length, the output external view △P is shown on the vertical axis. The initial axial position of the control rod to be pulled out is determined on the horizontal axis.
As shown in the figure, core center 'r1. In l,
The amount of local power increase is large, whereas in the upper and lower parts of the core where the power is small, the power increase 't1 is small. Therefore, when using the system of the present invention, it is possible to reduce the allowable pull-out length at the center of the core and increase the allowable pull-out length at the top and bottom of the core, as shown in Figure 5 (1). ? +1 city!, the first one because Mitomo withdrawal is prevented.
As shown in Figure J, a constant increase in output can be suppressed regardless of the initial axial force orientation of the No. 2 control rod. In addition, the adoption of the control rod control system of the present invention [Secondly, when multiple control rods are withdrawn at the same time, even if a control rod is erroneously withdrawn during power operation, the core detection system is not used. At this position, the control rod is prevented from being pulled out easily.
Excessive increase in output can be prevented. [) #, bright effect] As stated above, the control rod control system of the present invention has the following effects:
Since control rod withdrawal is prevented using the relationship between the initial control rod position and allowable withdrawal length based on the axial power distribution of the process computer, the bypass state of the LPRM, the number of control rods to be withdrawn, and the initial control rod position 1rt ( Even if control rods are withdrawn during power operation, there is a small amount of fuel that can be used to limit the increase in power output to an appropriate constant amount by reliably preventing control rod withdrawal. It is possible to maintain a thermal margin and improve the reliability and safety of boiling water reactors.

[Brief explanation of the drawing]

Fig. 1 is a layout diagram of a punched control rod and a fixed type in-reactor neutron detector, Fig. 2 is a signal strength-control rod drawing position characteristic diagram of a conventional device, and Fig. 3 is a boiling water type atom according to the present invention 52. Figure 4 is a block diagram showing the configuration of the control rod withdrawal monitoring device according to the present invention, and Figure 5 is a diagram showing the control rod drive system of the reactor. 6 is a basic allowable withdrawal length characteristic diagram, and FIG. 6 is a basic D%j+ direction output force distribution diagram that is integrated into the control rod withdrawal monitoring device according to the present invention. FIG. Fig. 9 shows a method of converting the output distribution in the axial direction of the gap to the allowable pull-out length. -t Q!J characteristic diagram, Figure 10 shows the output increase when the IbIJ control rod is pulled out by the same length fit-control OI
The I rod initial position characteristic diagram and FIG. 11 are the output rise Jk-control persimmon initial position (M bell characteristic diagrams) when the device of the present invention is used.・Control rod withdrawal monitoring device 65...Reactor core 6...Control rod drive (actuation structure 7...Control rod control device 8...Phantom control/selection circuit 9...Control rod withdrawal prevention position setting circuit 10...・Control rod axial position detection device 11 ・Process detection 1 machine 12 ・Hf group for instantaneous contact with withdrawal control rod 13 ・Characteristics conversion circuit Sl ・Control 8 operation 4g No. S2・...Le control rod withdrawal prevention position fe1 signal S3...?1ilJ control rod drive signal S4...Control rod selection signal S4A...iV control rod selection signal S5...Control rod axial position movement, signal S 5 A... Pull-out control rod axial position signal S6...
Axial output distribution No. 4i S7... Acceptance and withdrawal length characteristic signal Representative Patent attorney Nori Kei Chika (and 1 other person) Figure 7 (Top) (+4-Center) (Part 1)
Cow 'll'& UjhJ7JjKRImiki H・ark
(JUt# (ITL), PI Figure 8 (Part 1) (Middle * Part J
(T part ji axial direction - mortar) A, 4 (Oroka f I 1t)
Figure 9

Claims (2)

[Claims] (1) What is the core of a nuclear reactor, the control rods that are pulled out and inserted into this core, and these controls? A fourth control rod driver for the 1lII rod, a control rod control device that controls this control rod drive mechanism, a control rod axial position detection device for the control rod, and this control rod nib.
A control rod withdrawal monitoring device which receives the 1δ signal from the above side (fi'l rod control device) and sends a control @I rod withdrawal prevention position signal to the control device made by the JII control rod control device, and this control rod. In a control rod control system equipped with a rod withdrawal monitoring device (-a process monitoring system that inputs the axial power distribution of the fuel assembly in contact with the control rod f), the control rod withdrawal monitoring device monitors the control rod axial position. The target control rod selection circuit receives the control rod axial position from the detection device (No. A characteristic conversion circuit that creates an allowable pull-out length characteristic using the axial output distribution signal of the aggregate, the allowable pull-out length characteristic from this characteristic converter circuit, and a pull-out control rod axial position signal from the target control Its J selection circuit. 1. A control rod control system comprising: a control rod withdrawal prevention position setting circuit that outputs a control rod withdrawal prevention position signal determined using the control rod withdrawal prevention position signal to a control rod control device. (2) The allowable pull-out length characteristic of the characteristic conversion circuit is set using the basic allowable pull-out length characteristic and the basic axial direction output distribution built into the characteristic conversion circuit.
Control rod control system 0