JPS61105491A - Monitor device for operation region of boiling water type reactor - 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 an operating range monitoring device for a boiling water nuclear reactor that more flexibly controls the output of a nuclear power plant in response to power demand.

[Technical background of the invention and its problems] Nuclear power plants operate at a constant output called single base load operation, avoiding output fluctuations as much as possible, but as the proportion of nuclear power generation in the power system increases. Therefore, there is an increasing need for more flexible output control in response to seasonal or temporal fluctuations in power demand.

However, there are two main types of power control methods for boiling water reactors (hereinafter referred to as BWRs): one is a reactor reaction control method by adjusting the control rod position, and the other is a recirculation flow rate control method.・This is an output control method based on control. Both output side types using control rods #: t1 Since the local power distribution changes significantly before and after control rod operation, it is necessary to plan the control rod operation amount and operation procedure in detail in advance, and it is necessary to plan the control rod operation amount and operation procedure in detail before starting the reactor. It is used for large changes in output level, such as in the case of shutdown, long-term reactivity, and adjustment of output distribution. On the other hand, the output control method using recirculation flow rate control is suitable for controlling the output at any point in time because F) output can be easily controlled simply by controlling the circulation flow rate, and is generally suitable for controlling output in response to load fluctuations. This control method is used for tracking.

By the way, in a BWR, the relationship between the core thermal output and the core flow rate is regulated in order to maintain the integrity of the nuclear fuel and each 1) 4m reactor, and the reactor must be operated within the following range. FIG. 3 is a graph showing this limit range, where the horizontal axis represents the core flow rate and the hood axis represents the core thermal output. In the figure, the t line is the upper limit of the core flow rate.

The m line indicates its lower limit, and the n line is called a rondo block line. Therefore, the area surrounded by these t, m, and n lines (shaded area) becomes the drivable range.

Because of these regulations, even though reactor output can be easily changed using the recirculation flow rate control method,
In reality, it is necessary to operate within the above-mentioned limited range, and changing the output so as not to deviate from this range poses various problems as described below.

That is, as a result of nuclear fission in the reactor core, l-135 and its daughter nuclide, Xe-135, are produced.

Since this Xe-135H is a neutron absorbing material, it causes a decrease in reactivity, and therefore, the core flow 4 required to achieve a predetermined power level V changes depending on how much Xe-135H is accumulated in the reactor core. Also.

The amount of Xe-135 produced changes with fluctuations in output.

Moreover, since the half-life from nuclear fission to the generation of Xe-135 is several hours, it changes with a delay of several hours. In this way, Xe-135 affects output changes, and the amount of Xe-135 produced changes with output changes. Therefore, when changing the output in %BWR, consider the current accumulated amount of Xe-135 and check whether it falls within the limits related to the output car arm 1 elbow. This must be done by determining whether or not deviation from the above-mentioned limit range occurs due to fluctuations in .

By the way, the core performance of a regular nuclear power plant is managed by a process meter Xm. The main role of the process computer is to monitor the current state of the reactor core based on the signals obtained from measurement 6, which measures the state of the reactor. When trying to perform output operations, it is not possible to provide information on whether the requested output change is possible within the limits, which in turn requires detailed offline analysis, making it difficult to actually It is very difficult to operate the BWR flexibly in this way. [Objective of the Invention] The present invention has been made in view of the above circumstances, and it is necessary to constantly monitor the area where the output can be changed in the operation of the BWR. The object of the present invention is to provide a BWR operating range monitoring device that enables flexible output operation by presenting the information to the operator.

[Summary of the Invention] In order to achieve the above object, the present invention includes a measurement system installed in a nuclear reactor and a measurement system that measures core thermal output, core flow rate, and 1-135 based on plant data obtained from this measurement system. X
A current core state estimation device that calculates the accumulated amount of e-135, and an operable region prediction device that uses a core state prediction model to determine the range in which output can be changed based on the data obtained by this current core state estimation device. a storage device for storing respective data obtained by the current core state estimation device and the operable region prediction device; and a display device for displaying the data obtained by the operable region prediction device stored in the storage device. The present invention relates to an operating range monitoring device for a boiling water reactor, comprising:

[Embodiments of the invention] An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention.

As shown in FIG. 1, the operating area monitoring device l of the present invention
t3 receives data from the measurement system 2 installed in the reactor 1 and calculates the current thermal output, core flow rate, Xe-135 and l.
A current core state estimation device 4 that calculates -135 accumulation i;
An operable region prediction device 5 that calculates an output changeable region based on the current core state obtained from this, and a storage device that stores the results obtained by the current core state estimation device 4 and the operable region prediction device 5. lt 6, and a display device 7 that reads out the operable region prediction results from the storage device #6 and presents them to reactor operators.

However, the current core state estimation device 412. The measurement system that measures the state of the reactor receives data such as feed water temperature, feed water flow rate, reactor pressure, core flow rate, etc. Based on that data, the current thermal output is calculated from the meter, the storage device 6, and the previous calculation. The current accumulated amount of l-135°Xe-135 is determined based on the dynamic characteristic equation described later which describes the birth, damage, and extinction of 1-135 and Xe-135. The current accumulated amount of l-135 and Xe-135 thus determined is stored in the storage device 6 together with the thermal output and the core flow rate as the result of estimating the state of the core in the Okura.

Incidentally, the following dynamic characteristic equation for determining the accumulated amounts of Xe-135 and l-135 is known.

-λxxi(t) −'xXt(t)φ1(t) --
-----= (1) Here, X is # degree of Xe-135,
λX is its decay constant, rz is Xe-1 per nuclear fission
The direct generation rate of 35, σx the neutron absorption cross section of FiXe-135, i is the axial node, I is the inclination of l-135, and the decay constant alrX of λl is 1-135 per fission.
, Σj is the fission cross section, and φ is the thermal neutron flux.

Next, the operable range prediction device 5 determines the output changeable range based on the current core state estimation result obtained by the above-mentioned current core state estimation device 4. Here, a prediction model is required to predict changes in core flow rate when the strain level of Xe-135 and reactor power change. The simplest such model is W = F (P, X, Go) −−−−−−−−−−−
----(3) Here, W is the core flow rate.

P is the furnace power.

X is the Xe-135 concentration.

As shown in ◎, which shows the CO adjustment parameter, the furnace output P is calculated in advance through off-line analysis.
, a functional form V representing the relationship between the Xe-135 concentration X and the core flow rate W is determined in advance. However, the adjustment parameter Co is 0, which is determined so that the latest core state estimated by the current core state estimation device 4 matches the above three equations. The following (4) is a predictive model based on a physical model.
) is based on the one-dimensional dispersive equation of Eq. Special Public Service 1987-799
A known model listed in the issue! It can also be used.

1------------= (4) Here, φ is the fast neutron flux M! l is the moving area.

K″′ is an infinite multiplication coefficient, C is a void correction coefficient, and WD.

is the density of water when controlling the reactor power, WDlo.

B1'' [respectively indicates water density and radial leakage at T zero.

And the prediction model is l-135, Xe-13
By combining this with the dynamic characteristic equation that describes the creation and disappearance of 5, it is possible to predict changes in the core flow rate after changing the output. Next, the flow of processing in the drivable region prediction device 5 is shown in FIG.

First, in the initial matching unit IO, values of adjustment parameters are determined so that the prediction model matches the latest core state.

Next, in the change output level setting section 1), the output level candidate is divided into appropriate intervals, for example, 2% rated output, by dividing the range from 100% rated output to 50 1 rated output into appropriate intervals, for example, 2% rated output. If there is a candidate for the next output level in the next output level candidate determination unit 12, the output level from the upper limit to the lower limit is sequentially inputted to the core state offshore prediction s14 as a transformer output level from the current state. Further, if there is no output level candidate, the result of the determination by the output level candidate determination unit 12 is inputted to the output unit 13 . The core state prediction unit 14 is handed over from the latest core state to the change output level setting unit 1) and changes in the core state when the output is changed to the next level.
0 (Here, the above equations (1) and (2) are used as the characteristic equation 8, and the prediction model is The calculation flow for predicting the reactor core state when using the above equation (4) can be done by following the known calculation flow for predicting reactor power described in Japanese Patent Publication No. 1987-799.) Prediction result determination unit 15
In this case, it is determined whether or not the prediction result of the output car flow Hayabusa obtained by the core state prediction unit 14≠5 is within the above-mentioned operation limit range.Therefore, the changed output level setting unit 1) to
As described above, the process of the core result determination unit 15 is repeated until there are no candidates for the output level to be predicted in the changed output level setting unit 1). The output unit 13 writes one or more prediction results together into the storage device 3 shown in FIG.

With the above Ep-order, the process in the drivable region prediction device 2 is completed. The next display device 4 reads the results of the output range prediction side device 2 from the storage device 3, and displays the possible output change range based on the current core state on a display device such as a CRT. Accordingly, the operating range monitoring device f1' of the present invention operates at appropriate time intervals, for example every 15 minutes.

and update the display of possible output change areas.

[Effect of @Ming] As explained above, the operating range monitoring device of the present invention always monitors the range where the output can be changed based on the Mengxin core state.1. This information is presented to the operator, so that the operator can know whether or not it is possible to suddenly increase or decrease the output, and to what extent it is possible to change the output. Able to make instant judgments. Therefore B
It simulates the excellent effect of being able to control the output of the WR to Tokyo according to the power demand.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a diagram showing the flow of processing in the operable range prediction device shown in Fig. 1, and Fig. 3 is a diagram showing the core thermal output in BWR. 01 is a diagram showing a core flow rate control curve...Reactor 2
...Measurement system 3...Operating area monitoring device 4...Lunk core-like hearing and footing device 5...Operable area prediction device 6...Storage device 7...Display device agent Patent attorney Boar Yoshiaki Mata (and 1 other person) Figure 1 Figure 2 Figure 3 Figure p Shinko 1

Claims (1)

[Claims] (1) Estimating the current state of the reactor by calculating the core thermal output, core flow rate, and accumulated amount of I-135 and Xe-135 based on the measurement system installed in the reactor and the plant data obtained from the measurement system. a device, an operable region prediction device that uses a core state prediction model to determine an output changeable region based on data obtained by the current core state estimation device, the current core state estimation device, and the operable region. Boiling water comprising a storage device that stores each data obtained by the prediction device, and a display device that displays the data obtained by the operable range prediction device stored in the storage device. Operating area monitoring device for type nuclear reactors.