JP2670400B2 - Monitoring equipment for nuclear power plants - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monitoring apparatus for a boiling water nuclear power plant, and more particularly to a monitoring apparatus for a thermal limit value which is an operation limiting condition.

[0002]

2. Description of the Related Art In a boiling water nuclear power plant, a method is adopted in which the power is adjusted by changing the core flow rate by extracting / inserting control rods and controlling the recirculation flow rate. In order to ensure the integrity of the fuel, the minimum limit output ratio (Minimu
m Critical Power Ratio (MCPR) and linear power density (Li
ner Hert Generation Ratio (LHGR), a limit value (hereinafter referred to as a thermal limit value) that is allowable in operation is set. Therefore, when the output is changed by the control rod operation or the recirculation flow rate control, sufficient consideration must be taken so as not to deviate from these thermal limit values.

As a means for monitoring these operation limiting conditions, conventionally, a core performance calculation device for calculating an output distribution in the core and obtaining a critical power ratio (CPR) and a linear power density from the power distribution to monitor the power distribution has been used. In addition, the local power monitor (Local P0wer Rang Rang
e Monitoring System, hereinafter abbreviated as LPRM) There is a thermal limit value monitoring device that continuously monitors whether or not the signal exceeds. In the latter case, when the limit value is exceeded, control rod operation or recirculation flow rate control is blocked and output change is interrupted.

[0004]

The conventional thermal limit value monitoring apparatus based on the LPRM signal does not calculate the thermal limit value based on a physical model as performed in a core performance calculation apparatus. Instead, based on the limit power ratio and line power density calculated by the core performance calculation device, the value of the LPRM signal when each reaches the allowable limit value is estimated,
This is set as a limit value for the LPRM signal, and it is continuously monitored that the LPRM signal does not exceed the limit value. This L
The limit value for the PRM signal is corrected by a previously set correcting means so as not to be on the unsafe side as the control rod is operated and the recirculation flow rate is adjusted.

However, according to this method, as the control rod operation amount or the recirculation flow rate adjustment amount after the thermal limit value is calculated by the core performance calculation device becomes larger, the LPRM becomes larger.
The error with respect to the estimated value of the limit value for the signal increases. Also, depending on the state of the core, the error of the limit value may increase even if the operation amount is not so large. Therefore, it is desirable that the update of the LPRM limit value based on the result of the core performance calculation device be performed in a cycle as short as possible.

In particular, when the margin of the thermal limit value is small, there is a possibility that the thermal limit value cannot be sufficiently monitored. For this reason, the calculation of the thermal limit value by the core performance calculation device is performed in a cycle as short as possible in consideration of the capability of the computer. Since the calculation device has various functions in addition to the calculation of the thermal limit value, it is not possible to frequently calculate only the thermal limit value.

Therefore, the calculation cycle of the thermal limit value is at most
Although it can be shortened to only about 10 to 15 minutes, even in this case, the calculation of the thermal limit value occupies a large load ratio in the computer of the core performance calculation device, and the utilization of the computer for other functions is greatly limited. There was a problem to be done.

The object of the present invention is to update the operation limit value at short intervals when the change of the core state quantity is large and when the margin of the thermal limit value is small, and when the change is small and when the thermal limit value is small. If the margin of the thermal limit is large, the frequency of the core performance calculation is suppressed to monitor the thermal limit with high accuracy and to use the computer as much as possible for other functions during the period when the thermal limit has a margin. It is to provide a monitoring device for a nuclear power plant that can be utilized for

[0009]

In a boiling water nuclear power plant in which output control is performed by control rod operation and recirculation flow rate control, process data such as a control rod pattern, core flow rate and LPRM signal is input from the plant to obtain fuel. Core performance calculation device for calculating a thermal limit value which is a constraint condition imposed on the core, a thermal limit value calculated by the core performance calculation device, a control rod pattern at the time of calculation, a core flow rate and L
An operation limit value calculating device for inputting a PRM signal to calculate an operation limit value, and a control rod pattern and a core rod for inputting a control rod pattern, core flow rate, etc. when calculating the operation limit value and the thermal limit value from the operation limit value calculating device Thermal values for continuously inputting current values of process data such as pattern, core flow rate and LPRM signal to monitor the thermal limit value at high speed, and issuing an operation block signal to the reactor output control device as necessary. Limit value monitoring device, and the control pattern at the time of thermal limit value calculation from the core performance calculation device together with inputting monitoring results and monitoring process data used for monitoring from this thermal limit value monitoring device,
A determination device is provided for inputting process data such as the core flow rate and the LPRM signal to determine the necessity of calculating the thermal limit value by the core performance calculation device.

[0010]

The core performance calculation device inputs process data such as control rod pattern, core flow rate and LPRM signal from the plant to calculate the thermal limit value which is a constraint condition imposed on the fuel, and the core performance calculation device After the calculation of the thermal limit value, the operation limit value is input by inputting the thermal limit value calculated by the core performance calculation device, the control rod pattern used in the calculation, the core flow rate and the LPRM signal in the operation limit value calculation device. Is calculated.

As a means for continuously monitoring the thermal limit value while the output is being changed by operating the control rod or the recirculation flow rate, in the thermal limit value monitoring device, the operating limit value calculating device from the operating limit value calculating device operates and the thermal limit value. The control rod pattern and the core flow rate at the time of calculation are input, and the current values of the process data such as the control rod pattern, the core flow rate and the LPRM signal are continuously input from the plant to calculate the operation limit value at the time of calculation and the current state. The thermal limit value is continuously monitored by appropriately compensating for the magnitude of the change in quantity. As a result, when the thermal limit value deviates from the limit value, a signal for interrupting the operation of the reactor output control device is issued.

Further, in the determination device, the monitoring result and the process data used for the monitoring are input from the thermal limit value monitoring device, and the core performance calculation device inputs the control rod pattern at the time of calculating the thermal limit value. , Core flow rate, LPRM
By inputting process data such as signals, the necessity of calculating the thermal limit value by the core performance calculation device is judged, and if it is judged that the preset conditions are satisfied, the core performance calculation device is judged. Even if a request for calculation of the thermal limit value is made and the thermal limit value monitoring device determines that the operation limit value is not exceeded, if the change in the core state quantity is large, the thermal performance calculation device By requesting the calculation of the thermal limit value, the thermal limit value can be monitored with high accuracy by the core performance calculation device.

[0013]

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

As shown in the block diagram of FIG. 1, the LPRM 1a installed in the reactor 1 and the control rod position detector 1
b and the process data such as the core flow rate and the LPRM signal from the control rod patterns from each instrumentation system in the plant such as the core flow rate detector 1c and the like, and the core performance calculation device 2 imposes restrictions on the reactor fuel. Calculate the condition, the thermal limit,
Control rod pattern, core flow rate, LP used in this calculation
Output to the operation limit value calculation device 3 together with the RM signal and the like.
In response to this signal, the operation limit value calculation device 3 calculates the operation limit value and outputs it to the thermal limit value monitoring device 4.

In the thermal limit value monitoring device 4, the operating limit value and the control rod pattern at the time of calculating the thermal limit value, the core flow rate, etc. are input from the operating limit value calculating device 3, and the L
A control rod pattern from each instrumentation system in the plant such as PRM 1a, control rod position detector 1b and core flow rate detector 1c,
By continuously inputting the current values of the process data such as the core flow rate and the local output monitor signal, the operation limit value is appropriately corrected in accordance with the calculation time point and the magnitude of the change in the current state quantity to achieve thermal performance. Monitor limit values continuously. The monitoring result and the process data used for monitoring are output to the determination device 5.

When the monitored thermal limit value deviates from the predetermined limit value, the control rod control device 6 and the recirculation flow rate control disposed around the reactor 1 are controlled. It issues a block signal to the device 7 which blocks the operation.

The determination device 5 receives the output of the thermal limit value monitoring device 4 and the process data such as the control rod pattern, the core flow rate, and the LPRM signal from the core performance calculation device 2 at the time of calculating the thermal limit value. Then, the necessity of calculation of the thermal limit value by the core performance calculation device 2 is judged, and when it is judged that the preset condition is satisfied, the core performance calculation device 2 is thermally It is configured to require calculation of limits. It should be noted that each of the above-mentioned devices is usually composed of a computer except for the detector, and information such as process data is exchanged between the respective devices. Next, the operation of the above configuration will be described.

A control rod pattern, a core flow rate, and a control rod pattern from each instrumentation system in the plant, such as the LPRM 1a, the control rod position detector 1b, and the core flow rate detector 1c installed in the reactor 1.
The process data such as the PRM signal is input and the core performance calculation device 2 normally calculates the core performance such as the thermal limit value at a cycle of once an hour as in the conventional method. When the output is changed by the circulation flow rate control, the calculation is executed based on the request from the determination device 5.

When there is a request from the calculation cycle or the determination device 5, the core performance calculation device 2 inputs process data such as a control rod pattern, a core flow rate, and an LPRM signal from each instrumentation system and is imposed on the fuel. Calculate the thermal limit value that is the constraint. When the calculation of the thermal limit value is completed, the thermal limit value calculated by the core performance calculation device 2, the control rod pattern used for the calculation, the core flow rate, and the L
The PRM signal is transferred to the operation limit value calculation device 3.

In the operation limit value calculation device 3, when the core performance calculation device 2 outputs the thermal limit value, the control rod pattern, the core flow rate, the LPRM signal, etc., the minimum limit output ratio (MCPR) is calculated from these data. ) And maximum line power density (Maximum Liner Hert Generation Ratio, MLHG)
Calculate the operating limit for the thermal limit of R). An example of the calculation formula of the operation limit value is shown by the following formulas (1) and (2).

[0021]

RBCPOi = (RMCPRi / OLMCPR) * LPRMCi (1) RBHGOi = (LIMHGR / RMHGRi) * LPRMHi (2) where RBCPOi; the operation control value for each monitoring area with respect to the minimum limit output ratio RBHGOi; Operation control value for each monitoring area with respect to output density RMCPRi; Minimum limit output ratio for each monitoring area RMHGRi; Maximum line output density for each monitoring area OLMCPR; Minimum allowable output ratio for operation LIMHGR; Operational allowance Maximum value of line power density LPRMCi; average value of LPRM signal for each limit power ratio monitoring area LPRMHi; average value of LPRM signal for each line power density monitoring area

The minimum limit power ratio and the maximum linear power density are set to LP.
When continuously monitoring using the RM signal, each monitoring area is set based on the position of the LPRM 11 as shown in the minimum limit output ratio monitoring area diagram of FIG. That is, the monitoring area 10 for the minimum limit output ratio is the LPRM string
Four control rods 13 surrounded by four rods 12 and 16 rods 14 of the fuel assembly 14 constitute one monitoring region.

The monitoring area for the maximum linear power density is
As shown in the maximum line output density monitoring region diagram of FIG. 3, the minimum limit output ratio monitoring region shown in FIG.
One maximum line power density monitoring area that is divided into areas
15

In order to continuously monitor the thermal limit value during the control rod operation after the thermal limit value is calculated by the core performance calculation device 2 or during the change of the reactor output by the recirculation flow rate control, In the dynamic limit value monitoring device 4, the control rod pattern, core flow rate, etc. at the time of calculating the operation limit value and the thermal limit value are input from the operation limit value calculating device 3, and the control rod pattern is input from each instrumentation system of the reactor 1. , Core flow, LP
The thermal limit value is continuously input by continuously inputting the current value of the process data such as the RM signal and appropriately correcting the operation limit value in accordance with the calculation time point and the magnitude of the change in the current state quantity. Monitor. An example of the correction formula for the operation limit value is shown by the following formulas (3) and (4).

[0025]

RBCPi = RBCPOi * f (CRiO, CRi, WO, W) (3) RBHGi = RBHGOi * g (CRiO, CRi, WO, W) (4) RBCPi; for each monitoring area with respect to the minimum limit output ratio RBHGi after correction of RBHGi; operation limit value after correction for each monitoring area for maximum line power density f; correction function for operation limit value for minimum limit power ratio g; correction function for operation limit value for maximum line power density CRiO: Control rod withdrawal position for each monitoring area when calculating thermal limit value CRi: Control rod withdrawing position for each monitoring area during monitoring WO: Core flow rate when calculating thermal limit value W: Core flow rate during monitoring

The correction functions f and g are given by polynomials of the parameters indicated by the arguments, and the coefficients of the polynomials are determined by using the results of detailed offline core performance calculation prior to the operation. Once the corrected operation limit value is obtained by the above equations (3) and (4), the thermal limit value can be monitored by the following equation.
The steps (5), (6), (7), and (8) are performed.

[0027]

(Equation 3)

If it is determined by the above equation that the limit value is exceeded, the thermal limit value monitoring device 4 prevents the control rod control device 6 and the recirculation flow rate control device 7 from operating. Output block signal.

The determination device 5 is the thermal limit value monitoring device 4 described above.
From the core performance calculator 2, process data such as a control rod pattern and a core flow rate at the time of calculating thermal limit values are input from the core performance calculator 2 to the core performance calculator. It is determined whether the thermal limit value calculation by 2 is necessary.

For this determination, the determination device 5 uses the control rod pattern, the core flow rate and the LPRM which influence the thermal limit value.
A signal or the like is monitored as monitoring process data. First, based on the monitoring result input from the thermal limit value monitoring device 4, the determination device 5 increases the allowable variation range of the monitoring process data when the margin of the thermal limit value is large, while the thermal limit value is increased. If the margin of is small, the allowable change width of the monitoring process data is calculated so that the allowable change width of the monitoring process data is also small. The calculation of the allowable change width is performed based on a relational expression between a margin amount of the thermal limit value set in advance and the allowable change width of each monitoring process data.

Next, the difference between the monitoring process data input from the core performance calculation device 2 at the time of calculating the thermal limit value and the monitoring process data input from the thermal limit value monitoring device 4 is obtained, and each monitoring process is calculated. It is checked whether or not the amount of change in data exceeds the permissible change width calculated in advance. As a result, when it is determined that any one of the monitoring process data has changed within the allowable change width, the core performance calculation device 2 is requested to calculate the thermal limit value.

In this way, even when the thermal limit monitoring device 4 determines that the operation limit has not been exceeded, if the change in the core state quantity is large, the thermal limit value by the core performance calculation device 2 is determined. By requesting the calculation, it is possible to monitor the thermal limit value with high accuracy by the core performance calculation device 2 and to improve the monitoring accuracy of the subsequent continuous monitoring by the thermal limit value monitoring device 4. Become.

[0033]

As described above, according to the present invention, when the thermal limit value is continuously monitored by the simple calculation method using the LPRM signal during the operation of the control rod or the control of the recirculation flow rate, the operation restriction by the core performance calculation device is performed. Unlike the conventional method of initializing the value in a fixed cycle, by determining the necessity of calculating the thermal limit value based on the margin of the thermal limit value and the amount of change in the process data related to the thermal limit value. If the margin of the thermal limit is small, or if the change in the core state quantity is large, the operation limit value is calculated earlier, whereby the margin of the thermal limit value is small, or the core state quantity is calculated. The accuracy of monitoring when there is a large change is improved, and it becomes easier to secure fuel integrity.

Further, when the margin of the thermal limit value is large, or when the change in the core state quantity is small, it is possible to reduce the frequency of calculation of the operation limit value by the core performance calculation device, and thereby the core performance calculation device. There is an effect that the computer of can be effectively used for other functions.

[Brief description of the drawings]

FIG. 1 is a block configuration diagram of an embodiment of a monitoring apparatus for a nuclear power plant according to the present invention.

FIG. 2 is a diagram of a minimum limit output ratio monitoring area of the present invention.

FIG. 3 is a maximum line power density monitoring area diagram of the present invention.

[Explanation of symbols]

1 ... Reactor, 1a, 11 ... LPRM, 1b ... Control rod position detector, 1c ... Core flow rate detector, 2 ... Core performance calculation device,
3 ... Operation control value calculation device, 4 ... Thermal limit value monitoring device, 5
... Judgment device, 6 ... Control rod control device, 7 ... Recirculation flow rate control device, 10 ... Minimum limit output ratio monitoring region, 12 ... LPRM string, 13 ... Control rod, 14 ... Fuel assembly, 15 ... Maximum line power density Monitoring area.

Claims (1)

(57) [Claims] 1. In a boiling water nuclear power plant in which output control is performed by control rod operation and recirculation flow rate control, process data such as control rod pattern, core flow rate and local output monitor signal are input from the plant and imposed on fuel. The core performance calculation device that calculates the thermal limit value that is the constraint condition, the thermal limit value calculated by this core performance calculation device, the control rod pattern at the time of calculation, the core flow rate, the local output monitor signal, etc. are input. Control value calculation device for calculating the operation limit value by inputting the control rod pattern, the core flow rate, etc. at the time of calculating the operation limit value and thermal limit value from the operation control value calculation device, A thermal limit value monitoring device for continuously inputting current values of process data such as a flow rate and a local output monitor signal to monitor the thermal limit value at high speed, and a thermal limit value monitoring device. Process data, such as control rod pattern, core flow rate and local output monitor signal at the time of thermal limit value calculation from the core performance calculation device while inputting the monitoring result from the dynamic limit value monitoring device and the process data used for monitoring A monitoring device for a nuclear power plant, which comprises a determination device for determining whether or not the thermal limit value calculation is performed by the core performance calculation device by inputting