JPS5931489A - Reactor core performance calculating device - 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 invention] The present invention relates to a core performance calculation device for a nuclear reactor.

[Technical Background of the Invention] In general, nuclear reactor core performance calculations include current monitoring calculations to monitor whether the core is currently exhibiting the required performance while maintaining its health, and control. There are predictive calculations for creating long-term plans for the core, including rod operations, but in either case, it is required to obtain a highly accurate core power distribution. In order to calculate such a highly accurate output distribution, a positive 4M burnup distribution is required at the current moment for the current monitoring calculation and at the prediction time for the predictive chanting.

Generally, when a core is spatially represented by a set of many nodes, the burnup distribution at time t2 can be expressed by the following equation using the burnup distribution at time t1.

Here, EXPn(t)...burnup of node n at time t Pn(t)...output of node n at time t PTn...weight of uranium at the time of initial core installation of node n, and installed in a conventional nuclear power plant In the process control computer and off-line three-dimensional nuclear thermal-hydraulic calculation, the burnup distribution expressed by equation (I) is calculated using the following equation.

EXPn(t2)=EXPn(t1)+(Pn(t1)
/PTn)・(t2-t1)・・・・・・(II) Equation (II) assumes that the core power distribution is constant from time t1 to t2, but in an actual reactor, As shown in Figure 1, where time is plotted on the horizontal axis and power is plotted on the vertical axis, the power distribution of the reactor core during control rod pattern replacement, load following operation, etc. is shown by curve d in Figure 1. It often changes linearly over time, as shown in Figure 1.

In such a case, the burnup distribution calculated by the above-mentioned formula (II) is as shown in Figures 1 and 2.
Since the core power distribution at time t1 is used as is until time t2, the accuracy of the obtained burnup distribution cannot be said to be sufficient.

Therefore, conventionally, in order to calculate the burnup distribution with high accuracy using equation (II), the calculation method is to divide the period from time t1 to time t2 into several small time intervals as shown in Fig. 3. However, when using this method,
Since the calculation takes a long time, it is not only not responsive, but also the calculation costs are high, making it unsuitable for use as a core monitoring or core prediction calculation device in a nuclear power plant.

[Object of the Invention] The present invention has been made in response to such conventional circumstances;
The purpose of the present invention is to provide a reactor core performance calculation device that is responsive and highly accurate for monitoring and predicting core performance when the output changes linearly over time in a nuclear power plant.

[Summary of the invention} In other words, the present invention provides a power distribution calculation device that calculates the power distribution within a core, a power distribution storage device that stores the power distribution calculated by the power distribution calculation device, and a combustion controller that calculates the burnup distribution. a burnup distribution calculation device; a burnup distribution storage device that stores the burnup distribution calculated by the burnup distribution calculation device;
A controller that controls the power distribution calculation device and the burnup distribution calculation device, and an input that inputs necessary data to the power distribution calculation device and the burnup distribution meter tightening device and displays calculation results via the controller. and an output device, and the power distribution calculation device inputs the count values of the core state data measuring device and the in-core neutron flux measuring device or the core state data from the input/output device, and calculates the burnup from the burnup distribution calculation device. distribution and calculates the power distribution in the core based on the physical model built in the power distribution calculation device in advance, and the burnup distribution calculation device calculates the power distribution from the power distribution storage device and the power distribution calculation device. This is a nuclear reactor core performance calculation device characterized in that the burnup distribution is calculated manually by inputting the burnup distribution from the burnup distribution storage device.

"Embodiment of the Invention" Hereinafter, details of the present invention will be described with reference to an embodiment shown in the drawings.

FIG. 4 shows a core performance calculation device for a nuclear reactor according to an embodiment of the present invention, which includes a data sampler 1, a power distribution meter device 2, and a burnup distribution calculation device 3. , output distribution storage device 4, burnup distribution storage device 5,
It is composed of a controller 6 and an input/output device 7.

That is, the data sampler 1 collects the count values of the neutron east measuring device 10 installed in the core 9 housed in the reactor 8, as well as core current data such as coolant flow rate, reactor pressure, entrance and exit temperatures, control rod positions, etc. Core current data measuring device 1
Enter the count value of 1.

In the case of core monitoring calculation, the power distribution calculation device 2 uses data and
The count values of the neutron flux measurement record 10 and the core current data are input from the core current data measurement record 11 from the sampler 1, or in the case of core prediction calculation, the core current data is input from the input/output device 7 via the controller and roller 6. At the same time, the burn-up distribution calculated by the burn-up distribution storage device 3 or the burn-up distribution stored in the burn-up distribution storage device 5 is input, and the physical model pre-built in the output distribution calculation device 2 is input. Calculate the power distribution of the core based on.

The output distribution storage device 4 stores the calculation results calculated by the output distribution calculation device 2.

The burnup distribution calculation device 3 calculates the output distribution at time t1 stored in the output distribution storage device 4, the output distribution at time t2 calculated by the output distribution storage device 2, and the output distribution stored in the burnup distribution storage device. The burnup distribution at time t1 is input, and the burnup distribution at time t2 is calculated.

The burnup distribution storage device 5 stores the burnup distribution calculated by the burnup distribution storage device 3.

The controller 6 performs various controls on the power distribution calculation device 2, power distribution storage device 4, burnup distribution calculation device 3, and burnup distribution storage device 5 described above.

The input/output device 7 inputs necessary data to the power distribution calculation device 2 and the burnup distribution calculation device 3 via the controller 6 and displays the calculation results.

In other words, as shown in FIG. 1 already mentioned, this reactor core performance calculation device calculates the core current data output distribution and combustion at time t1 when the core power changes linearly with respect to time. Time t2 after △t time from coal distribution
The purpose is to calculate the core performance at

Then, in the in-core performance calculation device of this nuclear reactor, at time t2
In monitoring the current state of the reactor core, the controller 6 is operated automatically or by an operator's operation, and the power distribution calculation device 2 is operated by the controller 6.

The power distribution calculation device 2 started in this way uses the core current data at time t2 from the data sampler 1 and the burnup distribution at time t1 from the burnup distribution storage device 5 as an estimated value of the burnup distribution at time t2. A three-dimensional nuclear-thermal-hydraulic coupling calculation is performed based on a physical model built in the power distribution calculation device 2 in advance to calculate the core power distribution.

For this calculation, see e.g. Tsuiki et al.
．． “Convergence and Acceler
ation of Void Iteration i
n Boiling Water Reactor C
orc Calculations"Nucl, Sci
, Eng, 64, 724-732 (1977).

Note that the stored information in the burnup distribution storage device 5 and the power distribution storage device 4 is cleared at the time of reactor startup. Furthermore, it is not necessary to use the count values of the neutron flux measuring device 10 that are input to the data sampler 1 if the physical model is complete, but since the physical model is usually simplified to some extent to improve responsiveness, In such a case, it can be used for the purpose of correcting the output distribution calculation results. For details on this, please refer to Japanese Patent Application Laid-Open No. 54-40996.
It is stated in

In addition, in the reactor core performance calculation device configured as described above, in the core performance prediction calculation at time t2 at time t1, the controller 6 is manually activated by the operator, and the input/output device 7 of the controller 6 performs the core performance prediction calculation at time t2.
The current state data of the reactor core and the predicted time width Δt are input manually, and these values are input manually to the power distribution calculation device 2 activated by the controller 6.

The power distribution calculation device 2, together with these detectors, obtains the burnup distribution at time t1 from the fuel degree distribution storage device 5 at time t2.
This is input as the estimated value of the burnup distribution at and calculate the core power distribution.

However, in the core power distribution calculated in this way, the estimated value of the burnup distribution used for the calculation is the one at time t1, and the time width Δt between time t1 and t2 is the third Since the time width is considerably larger than that used in the conventional calculation method shown in the figure, it is generally quite different from the true output distribution.

Therefore, in this nuclear reactor core performance calculation device, as shown in the flowchart of FIG. 5, the burnup distribution calculation device 3 is activated by the controller 6 when the calculation of the power distribution in the power distribution calculation device 2 is completed. This burnup distribution calculation device 3 calculates the output distribution at time t2 from the output distribution meter device 2, the output distribution at time t1 from the output distribution storage device 4, and the output distribution at time t1 from the burnup distribution storage device 5. In addition to inputting the burnup distribution in each reactor, △t is input from the clock built into the controller 6 during core monitoring, and △t input from the input/output device 7 by the operator during prediction.
t is input, and the combustion quality distribution at time t2 is calculated by the method shown below.

That is, in general, as shown in Figure 1 already mentioned,
The output of node n at time t1 is Pn(t1), the output at time t2 is Pn(t2), and when the core output changes linearly with time, time t(t1<t<
The output of node n at t2) can be given by the following equation.

Pn(t)=Pn(t1)+ {(Pn(t2)-Pn(t1))/(t2-t1)}・(t-t1)...(III
) By substituting this equation (III) into the above-mentioned equation (I) and performing integration, the following equation is obtained.

EXPn(t2)=EXPn(t1)+(1/2PTn
)・(Pn(t1)+Pn(t2))・(t2−t1)
(IV) Therefore, the burnup distribution calculation device 3 calculates the burnup distribution at time t2 using the equation (IV) obtained in this way.

However, the fuel concentration distribution obtained in this way is the output pn at time t2 used in equation (IV).
(t2) is different from the true output, so it is different from the burnup distribution of the engine.

Therefore, the controller 6 causes the power distribution calculation device 2 and the burnup distribution calculation device 3 to perform repetitions as shown in the flowchart of FIG. 5 in order to obtain the true power distribution and burnup distribution.

That is, the controller 6 starts the output distribution calculation device 2, causes the output distribution calculation device 2 to input the burnup distribution at time t2 from the burnup distribution storage device 5, and calculates the output distribution using this value as the estimated value of the combustion pox distribution. The device 2 is caused to calculate the output distribution at time t2.

The output distribution at time t2 calculated in this way is output to the burnup distribution calculation device 3, and the burnup distribution calculation device 3 calculates the burnup distribution at time t2 based on this.

The controller 6 repeats the output distribution calculation by the output distribution calculation device 2 in this way, and the output distribution calculation device 2
The newly found output distribution is compared with the previously found output distribution, and the difference is determined by, for example, the above-mentioned Ts
When the convergence determination conditions stated in the document by Uiki et al. are satisfied, it is assumed that the true power distribution and burnup distribution have been obtained, and the calculation is terminated.

Note that since this iterative calculation usually converges after several to 10 iterations, the time required to calculate the burnup distribution using this method is reduced to several tenths of that of the conventional method.

The power distribution and burnup distribution obtained in this way are
It is output to the input/output device 7 via the controller 6. In the case of core monitoring, the calculation results of the power distribution by the power distribution calculation device 2 and the calculation results of the burnup distribution by the burnup distribution calculation device 3 are stored in the power distribution storage device 4 and the burnup distribution storage device 5, respectively. , the previously stored content is updated with new content.

Figure 6 shows the predicted calculation results when the reactor core performance calculation device configured as described above is combined with a process control computer installed in a nuclear power plant to provide a prediction function. , in the figure, curve a represents the power distribution obtained by the reactor core performance calculation device described above, and curve b
Curve C shows the output distribution obtained by off-line three-dimensional nuclear thermal-hydraulic calculation using the same time width as that of this device, and curve C shows the output distribution obtained by cutting the time width into small pieces.

As is clear from this figure, the axis of the predicted and calculated power distribution almost coincides with the power distribution shown by curve C, which is considered to be close to the actual core state.

Effects of the Invention As described above, according to the nuclear reactor core performance calculation device of the present invention, burnup distribution can be calculated from time t1 to t2 by linstep as shown in FIG. Therefore, the number of three-dimensional nuclear-thermal-hydraulic coupling calculations and burnup distribution calculations can be reduced, and the calculation time can be reduced to several tenths of that of conventional methods.

In other words, in the conventional method, the third
As shown in the figure, the temporal change in output from time t1 to t2 is divided into fine time axes, the output distribution is made constant on each time axis, three-dimensional nuclear-thermal-hydraulic coupling calculation is performed, and the burnup distribution is compared to the previous one. Since calculations are performed sequentially from the burnup distribution and power distribution in the time range, in order to obtain high accuracy, it is necessary to make the time range smaller and increase the number of calculation steps. In addition, if the cost is very low, changes in burnup distribution and associated changes in core performance can be quickly calculated, and core performance can be evaluated quickly and accurately in monitoring or predicting the current state of the core. It can greatly contribute to the safe and efficient operation of nuclear reactors.

Furthermore, according to the reactor core performance calculation device of the present invention, the effective multiplication factor of the reactor core can be obtained in three-dimensional nuclear-thermal-hydraulic coupling calculation, so it is also possible to predict the criticality of the reactor core due to changes in burnup distribution. It can be done easily.

[Brief explanation of drawings]

Figure 1 is a graph for explaining the burnup distribution calculation method according to the present invention, Figure 2 is a graph when the conventional method is executed with the same calculation steps as the present invention, and Figure 3 is the burnup distribution according to the conventional method. FIG. 4 is a block diagram showing a nuclear reactor core performance calculation device according to an embodiment of the present invention.
Figure 5 is a flowchart showing the burnup distribution calculation method of the reactor core performance calculation device shown in Figure 4;
2 is a graph showing the core average axial output distribution obtained when the reactor core performance calculation device shown in the figure is combined with a process control computer to provide a prediction function. . 1……Data sampler 2……Output distribution calculation device 3……Bunup distribution calculation device 4……Output distribution calculation device 5……Bunup distribution storage device 6…… … Controller 7 … Input/output device 8 … Reactor 9 … Core 10 … Neutron flux measuring device 11 … Core current data measuring device

Claims (1)

[Claims] A power distribution calculation device that calculates the power distribution in the core, a power distribution calculation device that stores the power distribution calculated by this power distribution calculation device, a burnup distribution calculation device that calculates the burnup distribution, and this burnup distribution. a burnup distribution storage device that stores the burnup distribution calculated by the calculation device; a controller that controls the power distribution calculation device and the burnup distribution calculation device; and a burnup distribution storage device that stores the burnup distribution calculated by the calculation device; The power distribution calculation device consists of an input/output device that inputs necessary data to the power distribution calculation device and displays the output results. The core state data is input from the output device, and the burn-up distribution is input from the burnup distribution calculation device, and the power distribution in the core is roughly calculated using the physical model built in the power distribution meter main skin. When the output distribution is inputted from the output distribution storage device and the output distribution calculation device, the burnup distribution calculation device manually calculates the combustion distribution from the burnup distribution calculation device and calculates the burnup distribution in one minute. A nuclear reactor core performance calculation device characterized by: