JPS6124677B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an input reaction restriction device, and particularly to an input reactivity control device suitable for limiting the magnitude of input reactivity when operating a control rod of a nuclear reactor. It is related to the device.

[Background of the invention]

Nuclear reactors have means for preventing accidents such as reactivity accidents due to excessive reactivity input or fuel damage due to rapid fluctuations in local output in the operation of control rods for adjusting reactivity. There are two methods for this method. The first method is to predict in advance the magnitude of reactivity that will be introduced due to an expected change in control rod pattern (hereinafter referred to as control rod sequence), and then store the allowable control rod sequence in a computer. This monitors whether the order in which the operator operates the control rods matches that order (control rod value minimizer). The second method is to monitor signals from the whole core power meter and local power meter (LPRM) in reactors that allow in-core instrumentation, such as light water boiling reactors (BWRs), and It is determined whether the control rod operation according to the instruction is within the range of the permissible output level and output fluctuation rate.

However, with the first method, it is virtually impossible to change the control rod pattern that is not in the control rod sequence, and even if the monitoring device is deactivated and a special pattern change is required, the predicted injection There is a lot of work involved in calculating the degree of reactivity, making it difficult to respond quickly.
In addition, in the second method, it is necessary to extract a signal of the output level or output fluctuation rate by actually operating the control rods, and it is necessary to extract a signal of the output level or output fluctuation rate by actually operating the control rods. It is impossible to apply this method to reactors that do not have in-core instrumentation or are difficult to implement.

[Purpose of the invention]

An object of the present invention is to easily and quickly determine whether or not the input reactivity due to control rod operations in a nuclear reactor that does not involve changes in control rod patterns that are not in the control rod sequence or in-reactor instrumentation is within an allowable range. It is an object of the present invention to provide an input reactivity limiting device that enables efficient nuclear reactor operation by adding reliability and flexibility to operators' control rod operations.

[Summary of the invention]

The features of the present invention include a storage device that stores the degree of neutron flux distortion in other control rod channels at the approximate reactivity value when a single control rod is inserted in the control rod channel, and a control rod that is instructed by an operator. and an arithmetic unit that calculates the reactivity introduced by changing the pattern based on the reactivity value at the time of inserting the single control rod and the neutron flux distortion degree, and the calculated reactivity is determined as the injection reaction. The purpose is to operate the control rods so that the control rod pattern is specified when the degree of control rods is smaller than the limit value.

Therefore, the apparatus according to the present invention utilizes the fact that the reactivity value of any plurality of control rods can be estimated by combining information obtained by calculating the reactivity value of a single control rod. Since the only calculations required are multiplication, addition and subtraction, it is possible to predict the reactivity to be applied by changing the control rod pattern according to an operator's instruction in an extremely short time.

In other words, the reactivity value when a predetermined control rod is inserted into the control rod channel i in the reactor is Δρ _i ,
At that time, when the degree of distortion of the neutron flux φ in the other control rod channel j is expressed as a _ji (=neutron flux after perturbation/neutron flux before perturbation), the reaction when two control rods are inserted at the same time is The degree value Δρ _ij can be estimated using the following equation.

Δρ _ij =Δρ _i a _ij +Δρ _i a _ji (1) Or, in general, when N control rods are assumed, the equation is as follows.

Note that equation (2) can be obtained as follows. That is, it is assumed that a total of five control rods, one in each of five control rod channels 1 to 5, are operated as shown in FIG. 2 (N=5). At this time, if a control rod is inserted only into control rod channel 1, the reactivity value of control rod channel 1 will be affected only by the operation of that one control rod, and the reactivity value will be Δρ ₁ . Become. However, since control rods are operated in the other four control rod channels 2 to 5, the reactivity value of control rod channel 1 is also affected by the other control rod operations.
The degree of influence is a ₁₂ ×a ₁₃ ×a ₁₄ ×a ₁₅ . Therefore, the reactivity value of control rod channel 1 is: becomes. Reactivity values are determined for each of the other control rod channels in the same manner as above. Therefore, the second
The reactivity value when operating five control rods as shown in the figure is becomes. When operating N control rods, enter N in place of 5 in the above equation.

Now, the reactivity value Δρ _kl that is introduced when any control rod or group of control rods (represented by l, 1l<k) is pulled out from a pattern in which k control rods (1<kN) are inserted is expressed as: think. here Therefore, if information regarding the insertion of a single control rod (Δρ _i , a _ij ) is stored in the computer in advance, the magnitude of the insertion reactivity due to any control rod pattern change can be quickly determined using a simple arithmetic circuit. can be asked for.

Note that in the above explanation, parameters related to the control rod insertion rate are omitted for simplicity, but in an actual system, the insertion rate differs depending on each control rod channel.
In addition, the degree of withdrawal should also be displayed as a "change in insertion rate." In these cases, the portions expressed as control rod channels i and j in the above description may be regarded as multidimensional vectors including the "insertion rate." In addition, when the distortion of the neutron flux (a _ij ) changes depending on the neutron energy group g, the neutron flux of each energy group is calculated using the contribution Δρ _g,i of each energy group contributing to the overall reactivity Δρ _i as a weight. By using the average value a ij of the distortion a _{g, ij} , it is possible to easily predict the reactivity value of multiple control rods or the reactivity change due to a change in control rod pattern using the same method as described above. can.

The aforementioned control rod value minimizer checks whether the control rods are operated in accordance with a predetermined control rod operating means during operation so that changes in the injection reactivity do not become excessive due to changes in the control rod pattern. This is something to check. The injection reactivity, which is the basis for determining the control rod operating procedure, is determined using a three-dimensional core simulator program using various control rod patterns assumed before the reactor is operated. This calculation is more complicated and takes a longer time than the calculation for determining the input reactivity in the present invention.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 shows an example of the configuration of a nuclear reactor control system having an input reactivity limiting device, which is a preferred embodiment of the present invention. The part surrounded by the dotted line is the input reactivity limiting device of this embodiment. That is, information regarding the single control control insertion prepared in advance (Δρ
_i , _aij ) are stored in the storage device 2. Single control rod insertion based on the current control rod pattern stored in the storage device 9 and the changed control rod pattern instructed from the input device 12 provided in the operation console 1 and stored in the storage device 2 The arithmetic device 3 calculates the amount of change in reactivity due to the pattern change using the information regarding the pattern change. A comparison device 5 determines the magnitude of the calculation result and the input reaction limit value stored in the storage device 4. If the amount of change in reactivity calculated by the calculation device 3 exceeds the input reactivity limit value,
This fact is displayed on the display device 11 (or alarm device) of the driving console 1. After seeing this, the operator selects another control rod pattern. When the comparison device 5 determines that the calculated reactivity value does not exceed the input reactivity limit value, the multiplier 61 of the control rod drive mechanism control device 6 functions. The multiplier 61 is
The gate of the signal transmission device 62 is closed based on the result of multiplication with the signal given from the operation instruction button 13 of the driving console 1. That is, when the output signals from the comparator 5 and the operation instruction button 13 are both "1" (the comparator 5 determines that the calculation result of the reactivity value is smaller than the input reactivity limit value, Furthermore, when the operation instruction button 13 is turned on), the gate of the signal transmission device 62 closes. Thereby, the signal transmission device 62 transmits the changed control rod pattern designated by the input device 12 to the control rod drive mechanism 7. The control rods 81 to 83 are provided by the control rod drive mechanism 7 that is driven according to instructions from the signal transmission device 62, and are changed to a new control rod pattern. This new control rod pattern is stored in the storage device 9.

The information that should be prepared in advance is the reactivity value Δρ _i (including insertion rate) for each control rod channel i when a predetermined control rod is inserted.
When planning a dimensional control rod arrangement, the reactivity value Δρ _i (Z _i ) at the insertion rate Z _i (hereinafter the same),
At that time, the distortion of the neutron flux in the other control rod channel j a _ij (in the case of three-dimensional display, a _j (Z _j ) _i
(Z _i ), the same applies below), and the input reaction limit value ΔR
It is. The calculation device 3 calculates the magnitude of the injection reactivity due to a change in the control rod pattern based on equation (3), but it is possible to calculate it digitally or analogously.

As explained above, according to this embodiment, the reactivity change due to any control rod pattern change can be easily determined from the information regarding single control rod insertion prepared in advance, and the result is compared with the limit value. It becomes possible to immediately judge whether or not a specified control rod pattern change is permissible. Therefore, there is no need to memorize a sequence of allowable control rod patterns in advance, and any change in control rod pattern can be made safely and under supervision as required for operation.

The calculation part simply performs four simple arithmetic operations using parameters prepared in advance, and the number of parameters increases only in an arithmetical manner even if the number of control rods increases. That is, if there are N control rod channels, the number of parameters to be prepared is the reactivity value N, the neutron flux distortion ^N2 , and the total number N(N+1). On the other hand, the number of arbitrary combinations of the number of control rods is ^2N , and in an actual nuclear reactor, the number of control rods is 20~
Since there are 50 control rod patterns, it is impossible to calculate the reactivity values of all control rod patterns in advance.
This difference becomes larger as the insertion rate is increased as a parameter. Therefore, by using the input reactivity limiting device according to this embodiment, this was not possible in the past. It becomes possible to "monitor the injection reactivity due to arbitrary control rod pattern changes," which not only improves the safety of the reactor, but also allows for efficient reactor operation by adding a degree of freedom to the operating method. driving can be realized.

〔Effect of the invention〕

According to the present invention, the control rod pattern can be quickly changed to any desired control rod pattern while operating the nuclear reactor. Even with this change, the safety of the nuclear reactor will not be compromised. This increases the degree of freedom in nuclear reactor operation and enables efficient nuclear reactor operation.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a nuclear reactor control system having an input reactivity limiting device, which is a preferred embodiment of the present invention;
FIG. 2 is an explanatory diagram showing how to obtain the reactivity value when operating a plurality of control rods. 1... Operating console, 2, 4... Storage device, 3...
Arithmetic device, 5... Comparison device, 6... Control rod drive controller, 7... Control rod drive mechanism, 61... Multiplier, 62...
Signal transmission device.

Claims (1)

[Claims] 1 A memory device that stores the reactivity value at the time of insertion of a single control rod in the relevant control rod channel and the degree of neutron flux distortion in other control rod channels at that time, and a change in the control rod pattern instructed by the operator. an arithmetic device that calculates the reactivity to be determined based on the reactivity value at the time of insertion of the single control rod and the neutron flux distortion degree stored in the storage device, and the calculated reactivity and the calculated reactivity set in advance. a comparison means for comparing the input reactivity limit value;
a control rod drive control device that outputs a drive signal to a control rod drive device that drives control rods constituting the control rod pattern when the comparison means determines that the injection reactivity is smaller than the injection reactivity limit value; Configured input reactivity limiting device.