JPS6142238B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a control system for a heavy water-moderated nuclear reactor, and in particular to an output control device that can quickly stabilize the reactor output after a large change in reactor output. It was thought that the role of nuclear power plants in conventional power supply systems was to mainly share the base load and always operate at rated output. but,
In the future, there will be a need for instantaneous output changes in response to power system frequency fluctuations and output changes for system frequency control. However, in heavy water-moderated reactors with small power coefficients, such rapid power changes have never been done in practice because it becomes difficult to control the Xe reactivity if the power level is changed significantly. . Figure 1 is a diagram showing the change in output and Xe concentration when the output level of a conventional heavy water-moderated reactor is changed instantaneously. The horizontal axis shows time (hr), and the vertical axis shows the Xe concentration.
The concentration is shown in ×10 ¹⁵ n/cc, and the reactor power is shown in %. The above n/cc represents the number of Xe molecules per cubic cm. If a nuclear reactor that is currently operating at 100% output is suddenly drastically reduced to 45% output, the reactor output will rapidly drop below 45% as shown by line 51 and eventually shut down. On the other hand, the Xe concentration increases once as shown by the line 52, reaches a maximum concentration after about 5 hours, and then gradually decreases. Figure 2 is a diagram showing the changes in output and Xe concentration when the output level of a conventional heavy water-moderated nuclear reactor is lowered by fine control rod manipulation, and the horizontal and vertical axes are the same as in Figure 1. Showing the same unit. Line 53 is 24 while moving control rods in and out from 100% reactor output.
It shows the change in output when gradually lowered to 45% after an hour. A line 54 shows how the Xe concentration changes at this time. In this way, in conventional heavy water-moderated reactors, if the output is suddenly reduced, the reactor will shut down due to a sudden increase in the It was necessary to lower it. In addition, when control rod operations are performed that drastically change the power level in a short period of time in order to shorten the descent time, there is the disadvantage that locally excessive power peaks are caused, reducing fuel economy. Ta. On the other hand, it is also effective to change the concentration of liquid poison in the heavy water moderator in order to control the Xe reactivity, but in this case, the poison removal tower and poison supply tower must be operated, so the effect is The drawback was that it took a long time to reach the reactor core, making it easy to misjudge control timing. The present invention aims to provide an output control device that can instantaneously change the output level significantly without causing local excessive peak output, and its characteristics include controlling the Xe reactivity. The purpose of the present invention is to provide a poison system operation prediction calculation device for operating a poison concentration control device in a timely manner without time delay, thereby controlling the output of a nuclear reactor. FIG. 3 is a system diagram illustrating a power control device for a heavy water-moderated nuclear reactor, which is an embodiment of the present invention.
Roughly dividing the diagram, there is a poison system operation prediction calculation device 23 in the upper part, a central control room 22 in the middle, and a reactor core 1 and poison circulation system of a heavy water-moderated nuclear reactor in the lower part. When the typewriter 19 of the input/output device 33 installed in the central control room 22 is started, the poison system operation prediction calculation device 23 is activated. When the output level fluctuation range to be changed is set in the output level fluctuation setter 31, the signal is input to the poison system operating method selection device 26. The poison system operating method selection device 26 reads the current nuclear power generator output from the reactor output recorder 30 connected to the generator output digital meter 18, and calculates the
The temporal change in reactivity is predicted by activating the Xe reactivity calculation device 29. Further, the result is output and displayed on the typewriter 19 or cathode ray tube display device 20 of the input/output device 33. The Xe reactivity calculation device 29 consists of a transient Xe concentration storage device 24 and a Xe concentration signal converter 25, and
The concentration storage device 24 stores information when the output level is changed as shown in FIGS. 4 to 13, which will be explained later.
Temporal changes in Xe concentration are memorized. The temporal change in the Xe concentration corresponding to the output level change instructed by the poison system operating method selection device 26 is a transient Xe
Since it can be known from the concentration storage device 24, it is transmitted to the poison system operating method selection device 26 as a reactivity signal via the Xe concentration signal converter 25. FIG. 14 is a diagram showing the relationship between Xe concentration and Xe reactivity, and a reactivity signal can be obtained depending on the relationship in this diagram. As will be explained later, the degree of fuel consumption differs depending on whether the reactor operation is from the beginning (BOC) to the end (EOC), so the reactivity signal value will differ. The poison system operating method selection device 26 activates the poison reactivity calculation device 32. The poison reactivity calculation device 32 is the poison system operation pattern storage device 2.
8 and a poison concentration signal converter 27, which converts various operation patterns stored in the poison system operation pattern storage device 28 into reactivity signals via the poison concentration signal converter 27 to select a poison system operation method. It is loaded into the device 26 and selects the optimum operating pattern for controlling the above-mentioned transient Xe reactivity. This selected poison system operation pattern is transferred from the poison system operation method selection device 26 to the input/output device 33.
and is output and displayed on the typewriter 19 and cathode ray tube display device 20. 15 to 23 show various operating patterns of the poison concentration adjustment system stored in the poison system operating pattern storage device 28. This will also be explained later. As mentioned above, poison system operation prediction calculation device 23
The poison concentration control device is operated according to the optimum poison system operation pattern predicted in the above. That is, when it is necessary to reduce the poison concentration in heavy water, the poison removal tower flow rate control switch 16 on the reactor control panel 21 is set to a predetermined flow rate. Accordingly, the bypass valve 12 is closed, and the two poison supply tower flow control valves 11 are opened to a predetermined opening degree. The heavy water moderator 2 is sent from the core 1 by the heavy water circulation pump 5 and bypasses the poison removal tower 6 to reduce the poison concentration in the heavy water to a predetermined concentration. Thereafter, the water passes through a heavy water purification tower 8 and an automatic poison concentration measuring device 9 and enters a dump tank 40. In contrast to the above, when increasing the poison concentration in heavy water, the poison supply tower flow rate adjustment switch 17 on the reactor control panel 21 is set to a predetermined flow rate. As a result, the poison supply tower flow rate control valve 13
is opened to a predetermined degree to allow a predetermined amount of poison to flow down from the poison supply tower 7 to the dump tank 40. At this time, the bypass valve 12 is opened by the poison removal tower flow rate control switch 16, and the poison removal tower flow rate control valve 11 is closed. Therefore, the heavy water moderator 2 is diverted from the core 1 through a dump tank 40, a heavy water circulation pump 5, and a branch point 41 to the poison concentration control device, and the main flow returns directly to the core 1, and a portion is sent to the heavy water purification tower. 8 and returns to the dump tank 40. Whether each device of the above poison concentration control device is operated according to a predetermined operation pattern is determined by
This information can be determined using the generator output digital meter 18, the flow meter 10, and the poison concentration recorder 15. Further, this detection signal is transmitted to the poison system operating method selection device 26. The poison system operation method selection device 26 predicts the optimum operation pattern again from this signal value, operates each poison system device according to the procedure described above, and adjusts the output level of the reactor to be constant. When the output balance of the reactor is thus obtained, the poison system operation prediction calculation device 23 is stopped by input from the typewriter 19 of the input/output device 33. FIG. 4 is a diagram showing temporal changes in the Xe concentration when decreasing the output level stored in the transient Xe concentration storage device 24, where the horizontal axis shows time in hr, and the vertical axis shows the Xe concentration in ^hr. Shown in n/cc units. line 5
5 is the case where the output is decreased from 100% to 0%, line 56 is the output from 75% to 0%, and line 57 is the output
The line 58 is a curve when the output is decreased from 50% to 0%, and from 25% to 0%. FIG. 5 has a horizontal axis and a vertical axis similar to those in FIG. 4, and is a diagram showing the temporal change in the Xe concentration when the reactor output is changed from a different output state to 25% output. That is, line 59 changes the output from 100% to 25%,
Line 60 goes from 75% output to 25%, line 61 goes from 50% output
to 25%, line 63 starts from 0% output and increases to 25%
This is a curve when changing the output. A point 62 where these four curves connect indicates the 25% output saturation Xe concentration. Similarly, Figure 6 is based on different outputs of the reactor.
This is a diagram showing the temporal change in Xe concentration when changing from 100% output to 50%.
Line 65 is a curve for changing from 75% output to 50%, line 67 is a curve for changing from 25% output to 50%, and line 68 is a curve for changing from 0% to 50% output. A point 66 shared by these four curves indicates the 50% output saturation Xe concentration. Figure 7 shows the case where the reactor power is changed to 75% power; line 69 shows the change from 100% power to 75%, and line 71 shows the change from 100% power to 75% power.
50% output to 75%, line 72 goes from 25% output to 75%
Line 73 is a curve when the output is changed from 0% to 75%. The point 70 that these lines share indicates the 75% power saturation Xe concentration. Figure 8 shows the case where the reactor output is increased to 100% output, line 74 increases from 75% output to 100%, line 75
is from 50% output to 100%, line 76 is from 25% output
100%, and the line 77 is a curve when the output is changed from 0% to 100%. The above is a pattern used at a time when not much time has passed since the start of reactor operation, that is, at BOC. On the other hand, at EOC, when the reactor has been operating for a relatively long time, the operating performance of the reactor is different from BOC, so the patterns shown in FIGS. 9 to 13 are used. All of these patterns from FIG. 4 to FIG. 13 are stored in the transient Xe concentration storage device 24 shown in FIG. 3, and one of them is selected depending on the operating state of the reactor. The curves used in the case of EOC will be explained below. Figure 9...When changing the reactor output to 0%, line 78...100% output → 0% Line 79...75% output → 0% Line 80...50% output → 0% Line 81... 25% output → 0% Figure 10... When changing the reactor output to 25%, line 82... 100% output → 25% output Line 83... 75% output → 25% output Line 84... 50% Output→25% output Line 85...Output 0%→25% output Point 86...25% output saturation Xe concentration Figure 11...When changing the reactor power to 50%, Line 87...100% output→ 50% output Line 88...75% output → 50% output Line 89...25% output → 50% output Line 90...Output 0% → 50% output Point 91...50% output saturation Xe concentration Figure 12... ...When changing the reactor output to 75% Line 92...100% output → 75% output Line 93...50% output → 75% output Line 94...25% output → 75% output Line 95...Output 0 % → 75% output Point 96... 75% output saturation Xe concentration Figure 13... When changing the reactor power to 100%, line 97... 75% output → 100% output Line 98... 50% output → 100% output Line 99...25% output → 100% output Line 100...Output 0% → 100% output Point 101...100% output Saturation Xe concentration A diagram showing the relationship between the generated Xe concentration and Xe reactivity, where the horizontal axis shows the Xe concentration in ×10 ¹⁵ n/cc,
The vertical axis shows the Xe reactivity in (%) Δk units. The solid line 102 is for BOC, and the dashed line 103 is for EOC. This diagram shows BOC and
This shows that in EOC, the amount of Xe produced differs, so the Xe reactivity also takes on different values. line 10
The numerical value attached to the key-shaped symbol marked 2,103 indicates the output percentage of the reactor. Next, FIGS. 15 to 23 show poison-based driving patterns stored in the poison-based driving pattern storage device 28. The horizontal axis of these figures shows time in sec, and the vertical axis shows the concentration of ^B10 in ppm.
and B ¹⁰ when poison liquid is supplied.
It represents the change in concentration of . Figure 15 shows the change in concentration of ^B10 when poison liquid is supplied for 4 seconds and then waited for 5 minutes.Curve 104 is the curve 104 between the reactor core 1 and the heavy water circulation pump 5 in Figure 3. In the dump tank 40
Curve 105 is the concentration of ^{B 10 in} heavy water at the core 1 inlet. By repeating the addition of poison liquid in this way, the
It can be seen that the concentration of B ¹⁰ increases gradually. Figure 16 shows the results when poison liquid is supplied for 10 minutes.
It shows the concentration change of ^B10 , where curve 106 is the concentration at the core 1 outlet and curve 107 is the concentration at the dump tank 4.
0 concentration, the curve 108 is the concentration at the branch point 41 to the poison concentration control device, and the curve 109 is the concentration at the core 1 described above.
This is the concentration at the inlet. As the poison liquid is supplied, the ^B10 concentration increases, and after the supply is finished, the B10 concentration increases to approximately 10%.
After a minute has passed, the B ¹⁰ concentration in the heavy water at the four locations becomes the same and has become a uniform concentration. Various driving patterns will be explained in the same manner below. Figure 17: Change in concentration of B ¹⁰ when poison removal was performed for 5 minutes at a flow rate of 10 m ³ /hr. Line 110... Exit line 111 of core 1... Dump tank 40 Line 112... Branch point 4 to poison concentration control device
1 Line 113... Inlet of core 1 Figure 18... Change in concentration of B ¹⁰ when poison removal is repeated for 5 minutes at a flow rate of 2 m ³ /hr and then waited for 10 minutes. Line 114... Exit line 115 of core 1... Dump tank 40 Line 116... Branch point 4 to poison concentration control device
1 Line 117... Inlet of core 1 Figure 19... Change in concentration of B ¹⁰ when poison removal is performed for 10 minutes at a flow rate of 2 m ³ /hr and the waiting period is repeated for 10 minutes. Line 118... Exit line 119 of core 1... Dump tank 40 Line 120... Branch point 4 to poison concentration control device
1 Line 121... Inlet of core 1 Figure 20... Change in B ¹⁰ concentration when poison removal is performed for 15 minutes at a flow rate of 2 m ³ /hr and then a 10-minute wait is repeated. Line 122... Exit line 123 of core 1... Dump tank 40 Line 124... Branch point 4 to poison concentration control device
1 Line 125...Inlet of core 1 Figure 21...Change in concentration of ^B10 when continuous poison removal operation is performed at a flow rate of 2 m ³ /hr. Line 126... Exit line 127 of core 1... Dump tank 40 Line 128... Branch point 4 to poison concentration control device
1 Line 129... Figure 22 at the inlet of core 1... Change in B ¹⁰ concentration when continuous poison removal operation is performed at a flow rate of 10 m ³ /hr. Line 130... Exit line 131 of core 1... Dump tank 40 Line 132... Branch point 4 to poison concentration control device
1 Line 133...Inlet of core 1 Figure 23...Change in concentration of ^B10 when continuous poison removal operation is performed at a flow rate of 20 m ³ /hr. Line 134... Exit line 135 of core 1... Dump tank 40 Line 136... Branch point 4 to poison concentration control device
1 Line 137...Inlet of core 1 Light water 3 is contained in the heavy water moderator 2 in the core 1 in Figure 3.
A light water pipe 34 containing 5 is installed to suppress secondary fluctuations in the reactor output due to changes in the Xe concentration in the reactor due to the introduction or removal of poison liquid as described above. I can do it. That is, while monitoring the reactor output recorder 30, the water level of the light water pipe 34 is adjusted to keep the output level constant. For this purpose, the light water pipe 34 is communicated with a light water surge tank 37, and a light water supply pump 36 and light water level control valves 38, 39 are provided in the communication path. The light water level control valves 38 and 39 are operated by the light water pipe water level control switch 14 in the central control room 22. For example, when raising the water level of light water, the light water level control valve 38 is opened by the light water pipe water level control switch 14, the light water supply pump 36 is operated, and the light water in the light water surge tank 37 is sent to the light water pipe 34. On the other hand, when lowering the water level, use the light water level control valve 3.
9 and return the light water 35 to the light water surge tank 37. At this time, the light water supply pump 36 is stopped and the control valve 38 is closed. FIG. 24 is a diagram showing an example of control by the output control device of the heavy water-moderated nuclear reactor shown in FIG. 3, and the horizontal axis represents time. The vertical axis on the left shows the reactor power and control rod density in %, and the concentration of poison B ¹⁰ .
Shown in ppm. Also, the vertical axis on the right is Xe
Concentrations are given in 10 ¹⁵ n/cc and light water levels are given in mm. First, the relationship between each of the above display items and symbols will be summarized. Solid line 140...Reactor power (%) Broken line 141...Control rod density (%) Solid line 142...Concentration of poison ^B10 in heavy water at the inlet of reactor core 1 (ppm) Solid line 143...Poison concentration control device Concentration of ^B10 in heavy water at branch point 41 (ppm) Solid line 144...Xe concentration in core 1 (×10 ¹⁵
n/cc) Solid line 145... Water level of light water 35 in light water pipe 34 (mm) This indicates that the reactor, which was at 100% output, is instantly lowered to the output level of 57% and is immediately maintained in an equilibrium state for operation. As an example of the desired control, when the control rods are rapidly inserted into the reactor core 1 and the control rod density % increases as shown by the broken line 141, the reactor power % rapidly decreases as shown by the solid line 140, and after about 4 hours 57 It stabilizes at %. At this time, the poison concentration control device is operated by the poison system operation prediction calculation device 23 shown in ^FIG .
2,143, the Xe concentration in the reactor core 1 can be controlled as shown by the solid line 144, and the desired output % can be achieved without stopping the reactor.
can be stabilized in a short period of time. Also,
The secondary output level fluctuations due to the introduction of Poison B ¹⁰ liquid are stabilized by more precise adjustment by adjusting the light water level, as shown by the solid line 145. As described above, the power control device for a heavy water moderated nuclear reactor of this embodiment can obtain the following effects by being equipped with a poison system operation prediction calculation device and a light water level adjustment device as shown in FIG. 1. It has become possible to perform reliable follow-up operation against instantaneous changes in reactor output. 2. Local excessive peaks are not caused in the fuel rods when the reactor output changes, and the integrity of the fuel is maintained, and the safety and economic efficiency of the reactor are improved. 3. Poison concentration can be adjusted immediately in response to changes in Xe concentration in the reactor, making it easier to control excessive changes in Xe reactivity. 4 As a comprehensive result of 1 to 3 above, the operation and control of the nuclear reactor becomes easier and the operating rate of the reactor can be improved. In the above embodiment, the secondary change in reactor output due to the introduction of poison liquid was controlled by adjusting the light water level, but instead of the light water pipe 34, a poison pipe containing poison liquid was used. It is also possible to install a water tank in the reactor core and adjust its water level. The power control device for a heavy water reactor of the present invention enables instantaneous and large changes in the output level without causing local excessive peak output, and has the effect of improving the safety and operation rate of the heavy water reactor. There is.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the change in output and Xe concentration when the output level of a conventional heavy water-moderated reactor is drastically reduced instantaneously, and Figure 2 is a diagram showing the output level of a conventional heavy water-moderated reactor. A line diagram showing changes in output and Xe concentration when lowered by fine control rod manipulation, Figure 3 is a system diagram of an output control device for a heavy water-moderated nuclear reactor, which is an embodiment of the present invention, Figure 4 ~ 1st
3 is a diagram showing the change in Xe concentration when the output level changes, stored in the transient Xe concentration storage device 24 in FIG. 3, and FIG. 14 is a diagram showing the relationship between the Xe concentration and the Diagrams showing the relationship, Figures 15 to 23 are diagrams showing the operation pattern of the poison concentration adjustment system stored in the poison system operation pattern storage device 28 of Figure 3, and Figure 24 is a diagram showing the heavy water FIG. 3 is a diagram showing an example of control by a furnace output control device. DESCRIPTION OF SYMBOLS 1... Core, 2... Heavy water moderator, 6... Poison removal tower, 7... Poison supply tower, 9... Automatic poison concentration measuring device, 11, 13... Flow rate control valve, 12... Bypass valve, 14...Light water pipe water level control switch, 15...Poison concentration recorder, 19
... Typewriter, 20 ... Braun tube display device, 21 ... Reactor control panel, 22 ... Main control room, 23 ... Poison system operation prediction calculation device, 24
...Transient Xe concentration storage device, 25...Xe concentration signal converter, 26...Poison system operation method selection device, 2
7...Poison concentration signal converter, 28...Poison system operation pattern storage device, 29...Xe reactivity calculation device, 30...Reactor output recorder, 31...
Output level fluctuation setting device, 32... Poison reactivity calculation device, 33... Input/output device, 34... Light water pipe.

Claims (1)

[Claims] 1. A heavy water-moderated nuclear reactor equipped with a control rod that adjusts the output of the reactor and a poison concentration control device that adjusts the amount of poison in heavy water that is a moderator of the reactor, an output level fluctuation setting device, a poison system operating method selection device that receives a signal from the output level fluctuation setting device and issues an instruction to change the output level;
A Xe reactivity calculation device that calculates the change in Xe reactivity after the output level changes according to the commanded output level of the poison system operating method selection device, and is ideal for controlling the Xe reactivity calculated by the Xe reactivity calculation device. a poison reactivity calculation device that selects a poison-based operation pattern from a stored operation pattern of a poison-based operation pattern storage device that stores a plurality of poison-based operation patterns by activation of the poison-based operation selection device; An output control device for a heavy water reactor, comprising: a control switch for the poison concentration control device that operates according to a poison system operation pattern.