JPS6015914B2 - Reactor thermal output calculation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nuclear reactor thermal output calculation device that detects false neutrons in various parts of the reactor core and calculates the thermal output of the reactor from these neutrons, and in particular, the present invention relates to a nuclear reactor thermal output calculation device that detects false neutrons from various parts of the reactor core and calculates the thermal output of the reactor from the neutrons. This invention relates to improvements in preprocessing means for detected neutron east signals.

As is well known, a nuclear reactor is capable of extracting thermal energy generated by a nuclear fission reaction caused by nuclear fuel absorbing neutrons and converting it into electrical energy or the like.

To safely operate such a nuclear reactor, it is essential to maintain the integrity of at least the nuclear fuel tank, and for this purpose it is necessary to monitor the reactor's thermal output from time to time. In order to monitor the thermal output of a nuclear reactor in a timely manner, a reactor thermal output calculation device is usually used that detects neutrons at various locations within the reactor core and calculates the thermal output of the reactor from this neutron flux. This device calculates thermal output by calculating the neutron east signals detected by multiple fixed neutron detectors installed in the reactor core using a thermal output calculation device. are not uniformly disposed throughout the entire region of the reactor core, but are only installed at the minimum required specific positions. Therefore, in calculating the thermal output based on the signals from these fixed neutron detectors, it is necessary to perform the following signal preprocessing. In other words, since the control pattern has symmetries such as mirror symmetry or rotational symmetry, this symmetry can be used to detect neutron detectors installed at one of the symmetrical positions in the core under the same conditions. The output signal of the front is also used as the signal of the other position, as if the thermal output could be calculated based on the signals from a large number of neutron detectors uniformly distributed throughout the reactor core. Process. Figure 1 a, b and Figure 2 a,
b is a schematic cross-sectional view of the reactor core shown to explain the preprocessing means for the neutron east signal in a conventional device.

Figure 1a is a diagram showing a control pattern with 1/crab mirror symmetry, and Figure 1b is a diagram that uses the symmetry shown in Figure 1a to obtain neutron east signal patterns corresponding to each layer in the reactor core. FIG. In addition, Figure 2a shows a control pattern with 1/4 rotational symmetry, and Figure 2b shows a control pattern for obtaining neutron east signal patterns corresponding to each layer in the core by utilizing the symmetry shown in Figure 2a. FIG. 3 is a diagram showing the relationship of detector usage. Note that one square in Fig. 1 a, b and Fig. 2 a, b indicates a block consisting of four fuel assemblies (hereinafter referred to as a detection block), and the center of the block is the neutron east detection position. The cross section between the corners of each square is the control bar insertion position. In the figure, A, B, and C indicate the difference in the insertion degree of the control rod. In addition, 1 to 8 in the figure indicate the detector numbers that actually exist in the detection block, and 1 to 8
indicates the detector number used in the detection block among the existing detectors. In this way, the output signals of detectors 1 to 8 installed in a specific detection block are
By also using it as a signal for a detection block where no detector exists, a pattern of neutron east signals corresponding to all detection blocks can be obtained. However, the neutron east signal preprocessing means in the conventional apparatus described above has the following problems.

In other words, the level of the neutron east signal detected by the fixed neutron detector is at the center of each detection block where the moderator is interposed, that is, at the center of the gap between the corners of the four fuel assemblies. When the detector is accurately located at the center, the maximum value is reached, and when it is deviated from the center, the bell is lowered by an amount corresponding to the deviation. Therefore, if there is a detector installed at the specific position that is deviated from the center, it will not only affect the detection block itself in which the detector is located, but also other detection blocks that use the detector. Errors also intervene in the neutron east signal for By the way, most of the control patterns of nuclear reactors currently in use have a 1/weak contrast symmetry. Therefore, if the symmetry is fully exploited, the number of detectors available in each detection block should not remain at one. In other words, for at least some detection blocks, signals from two detectors can be used as neutron east signals corresponding to one detection block. However, in the past, even when the control pattern is 1' reflection symmetry, the actual situation is that signal processing has only been performed for the case of 1/many reflection symmetry. The present invention has been made with attention to these points, and its purpose is to provide a significantly more accurate heat output than conventional ones even when some fixed neutron detectors are offset from the center of the detection block. A reactor thermal power calculation device that can perform calculations, maintain extremely reliable operation even if a few detectors fail without losing the thermal output calculation function, and can be manufactured at a relatively low cost. Our goal is to provide the following.

Hereinafter, the present invention will be explained in detail with reference to embodiments shown in the drawings. FIG. 3 is a block diagram showing the configuration of an embodiment of the present invention, and reference numerals 11a to 11n shown at the left end in the figure are a plurality of fixed neutron detectors installed at specific positions within the reactor core. The detection signals from the detectors 11a to 11n are input to the neutron east signal pattern forming device 12. The pattern forming device 12 generates a combination of neutron east signals directly corresponding to each part in the reactor core based on the neutron east signals inputted from the detectors 11a to 11n, and a control rod pattern input device 13 inputs a control rod pattern. The neutron east signal pattern is created by making maximum use of the characteristics of the neutron. Here, it is assumed that the control pattern is symmetrical with respect to 1/1. Therefore, the formed neutron east signal pattern is 1
Since the symmetry of /8 reflection symmetry is fully utilized, the neutron east signal corresponding to at least a part of the position in the core is a combination of the output signals of two neutron detectors. FIGS. 4a and 4b are cross-sectional views of the reactor core showing the relationship in which the detectors are used when forming the neutron east signal pattern by the device 12.

Note that one square in Figure 4 a, b is the same as Figure 1 a, b.
Similarly, a detection block consisting of four fuel assemblies is shown, and 1 to 8 and 1 to 8 also indicate the actual detector number and available detection, as in Figures 1b and 2b. This shows the device number. However, as a result of making maximum use of the symmetry of 1/8 reflection symmetry, the area shown in Figure 4 b... The number is surrounded by a dotted line to clearly indicate that it has increased compared to the case, and the meaning of the number is the same as 1 to 8. When the neutron east signal for each detection block in the signal pattern formed by the neutron east signal pattern forming device 12 is only a signal from a single detector, , this is directly supplied to the heat output calculation device 16 as the first signal SI, and when the signal is from a plurality of (two in this embodiment) detectors, this is supplied as the second signal S2. Maximum signal selection device 1
Supply to 5.

The maximum signal selection device 15 selects the signal showing the largest value for each of the second signals S2 supplied from the signal discrimination device 14, that is, in this embodiment, the larger one of the two signals, and selects this signal. is supplied to the heat output calculation device 16 as a signal S3. The thermal output calculation device 16 has a built-in computer or the like that is programmed in advance to be able to calculate the thermal output from the neutron east signal, and calculates the thermal output from the first predetermined signal S1 and the third signal S3. and output from terminal 17. Note that the signal discrimination device 14 and the maximum signal selection device 15 correspond to means for extracting the maximum neutron east signal of the present invention.

Next, the operation of the apparatus configured as described above will be explained.

In this device, as is clear from Fig. 4b, the signals that can be used as neutron east signals in the detection blocks located on the diagonals M and N of the reactor core are only the signals from a single detector 1 or 5. , the signals available as neutron east signals in most other detection blocks are the output signals from the two detectors. The signal that is finally used as the neutron east signal in the detection block that can use the above two signals is the one that shows a larger value, and the signal S3 becomes the input signal to the thermal output calculation device 16. Therefore, compared to conventional devices, it is possible to calculate heat output very accurately. That is, when the neutron east detector 11 is located at the center of a detection block consisting of four fuel assemblies 21, 22, 23, and 24 as shown in FIG. 5, the level of the neutron east signal is as shown in FIG. The maximum level is L.

However, in reality, there are cases where the neutron east detector 11 is deviated from the center by an amount R, as shown by the broken line in FIG. In such a case, the level of the neutron signal will drop to level L2 as shown in FIG. This is fuel assembly 2
This is due to the fact that the moderating effect of the moderator such as water present in the center of Nos. 1 to 24 is maximum at the center and becomes smaller as the distance from the center increases. Normally, heat output calculation device 1
6 is constructed in such a way that calculations are made assuming that the neutron detector is precisely located at the center of the four fuel assemblies 21 to 24, so the drop in signal level due to the above-mentioned positional deviation is This will result in an error. However, in this device, as mentioned above, the signal that shows the larger value of the two signals is selected and this becomes the input to the heat output calculation device 16, so the heat output can be calculated for the signal that shows the most accurate value. There are things that can be calculated. In other words, even if a low-level signal indicating an inaccurate value is included, this signal is removed in advance, so that accurate heat output calculation can be performed. In addition, with this device, when signals from two detectors can be used, even if one of the signals becomes unavailable due to a malfunction of the detector, the heat output can be calculated using the other signal without any problem. .

Therefore, this device has very high reliability against detector failure. Furthermore, when implementing this device, it is only necessary to improve the part that preprocesses the detected neutron east signal, and there is no need to install a new fixed neutron detector in the reactor core.

In other words, the existing fixed neutron detector can be used as is. Therefore, it has the advantage that it can be manufactured at low cost. Note that the present invention is not limited to the above embodiments. For example, in the above embodiment, the case of 1/8 reflection symmetry was shown, but it can also be implemented in the case of 1'8 rotational symmetry. Furthermore, the degree of symmetry is not limited to 1'8, but can be applied to 1'16 or more. Further, in the embodiment, the means for extracting the maximum neutron east signal include the signal discriminator 14 and the maximum signal selector 1.
5 is shown, but it is not limited to this. The point is that regardless of whether the combination of neutron east signals is from a single detector or from multiple detectors, the maximum neutron east signal transmitted from each part of the reactor core, that is, for each detection block, can be extracted. It is fine as long as it is something. As explained above, the present invention calculates combinations of neutron east signals corresponding to various positions in the reactor core based on neutron east signals detected by a plurality of fixed neutron detectors installed at specific positions in the reactor core. A neutron east signal pattern is created by making maximum use of the symmetry of the control pattern, and the neutron east signal corresponding to at least some of the layers in the core is a combination of signals from multiple neutron detectors. At the same time, the maximum neutron east signal for each light in the core in the signal pattern is extracted to calculate the heat output.

Therefore, according to the present invention, signals from a plurality of detectors can be used as the neutron east signal corresponding to at least a part of the ephemeris of each position in the core, and among those signals, the signal showing the largest value can be used. Since it is input to the thermal output calculation device, even if some of the fixed neutron detectors are shifted from the center of each detection position in the reactor core, it will be significantly easier to use than conventional ones. Accurate heat output calculation can be performed, and even if some of the signals from the available plurality of detectors are not obtained at all, the heat output can be calculated based on the remaining signals without any problem. Therefore, even if a part of the detector fails, the thermal output calculation function will not be lost, and extremely reliable operation can be expected.In addition, it is possible to install a new neutron detector by simply improving the signal processing system. Since it does not require anything, it is possible to provide a nuclear reactor thermal output calculation device that can be manufactured at low cost.

[Brief explanation of the drawing]

Figures 1a, b and 2a, b are schematic cross-sectional views of the reactor core for explaining the signal preprocessing means of a conventional device, and Figures 3 to 6 show an embodiment of the present invention. In the figure, Fig. 3 is a block diagram showing the configuration, Fig. 4 a and b are cross-sectional schematic diagrams of the reactor core showing the usage relationship of the detectors to obtain the neutron east signal pattern, and Fig. 5 is the center of the detection block. FIG. 6 is a schematic plan view showing the positional deviation of the detector relative to the sensor, and FIG. 6 is a waveform diagram showing changes in the detection signal level due to the deviation. 11, 11a to 11n... Fixed neutron detector, 12.
...Neutron East signal pattern forming device, 14...
... Signal discriminator, 13... Control pattern input device, 15... Maximum signal selection device, 16.
...Execution power calculation device, 17...Output terminal, 2
1-24...Fuel assembly. Figure 1 Figure 5 Figure 2 Figure 3 Figure 4 Figure 6

Claims (1)

[Claims] 1. A plurality of fixed neutron detectors installed at specific positions in the reactor core, and corresponding to each position in the reactor core based on neutron flux signals at the specific locations detected by these neutron detectors. A combination of neutron flux signals is created by making maximum use of the symmetry of the control rod pattern, and the neutron flux signal corresponding to at least a part of the core position is a combination of signals from multiple neutron detectors. A device for forming a flux signal pattern, a means for extracting a maximum neutron flux signal for each position in the reactor core in the signal pattern formed by this device, and performing calculations on each maximum neutron flux signal extracted by the means. A nuclear reactor thermal output calculation device comprising: a thermal output calculation device for calculating the thermal output of a nuclear reactor. 2. When the neutron flux signal at each position in the core is a signal from a single neutron detector, the means for extracting the maximum neutron flux signal supplies this signal as the first signal directly to the thermal power calculation device, and When the signal is from a neutron detector, a signal discrimination device that sends out this signal as a second signal, and a signal with the largest value among the second signals sent from this signal discrimination device are selected and heated. 2. The reactor thermal power calculation device according to claim 1, further comprising a maximum signal selection device for supplying to the power calculation device.