JP2008232879A - Core coolant flow measuring instrument, and core coolant flow measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow precise measurement, by correcting continuously an influence onto flow measurement caused by deposit of a metal ion, a clad or the like in a coolant of a boiling water nuclear reactor. <P>SOLUTION: This core coolant flow measuring instrument has a core flow rate computation processing part 20 and a core flow rate correction processing part 30. The core flow rate computation processing part 20 has the first signal input part 21 for inputting a pump part pressure difference of a recirculation pump, a rotational speed of the recirculation pump, and a coolant temperature, and a core flow rate computing part 22 for computing a core flow rate by a pump part pressure difference measuring method, based on the input values input by the first signal input part 21 and a Q-H characteristic of the recirculation pump. The core flow rate correction processing part 30 has the second signal input part 31 for inputting a metal ion concentration in the coolant, a flow rate deviation estimating part 32 for estimating a flow rate deviation, based on an input value of the metal ion concentration, and a flow rate correcting part 33 for calculating a difference between the core flow rate and the flow rate deviation as a new core flow rate measured value. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an apparatus and method for measuring the core coolant flow rate of a boiling water reactor.

  In the current boiling water nuclear power plant, in order to control the fission amount of nuclear fuel such as uranium generated in the nuclear reactor fuel in the reactor pressure vessel and to effectively remove the heat generated by the fission, The system that forcibly circulates water, which is the material, is adopted.

  If the circulation amount of the reactor coolant, that is, the core flow rate, is large, the amount of bubbles (voids) generated in the reactor core decreases, which increases the moderating effect on fast neutrons generated by fission and promotes fission. , Reactor power increases. On the contrary, when the core flow rate is low, the amount of bubbles increases and the reactor power decreases. In this way, in the boiling water nuclear power plant, the reactor core flow rate is an extremely important physical quantity not only from the viewpoint of safety of reactor cooling but also from the viewpoint of reactor power control, and is measured with high accuracy. Or is required to calculate.

  In addition, a natural circulation boiling water reactor is assumed as one of the future reactors. In this case, the core flow rate is not directly used to control the reactor power, but it is a safety point of view. And it is still an important physical quantity from the viewpoint of efficient operation management such as fuel combustion management, and it is required to measure or calculate with high accuracy as in the case of a forced circulation nuclear reactor.

  There is an improved boiling water nuclear power plant of the type in which a recirculation pump for circulating coolant in the core is built in a reactor pressure vessel. The built-in recirculation pump is called a reactor internal pump (RIP). Feed water fed from the turbine system is injected into a reactor pressure vessel (RPV) through a feed water pipe. The injected feed water is mixed with the saturated water separated by the steam separator in the upper plenum to become subcooled water, and flows between the shroud and the inner wall of the reactor pressure vessel to the downcomer.

  The coolant flowing down the downcomer is pressurized by a plurality of reactor recirculation pumps, passes through the lower grid plate, is heated by the core fuel, and boils. As a result, a two-phase fluid of steam and water flows to the steam separator, where it is separated into saturated water and saturated steam. Saturated water flows to the upper plenum section and is mixed with feed water again. On the other hand, the saturated steam is further sent to the turbine through the steam dryer and the main steam pipe.

  Here, there are roughly two core flow rate measuring methods for the improved boiling water reactor. One is a pump part differential pressure measurement method (referred to as PdP method), and the other is a core support plate differential pressure measurement method (referred to as CPdP method).

  The PdP method measures the pressure difference (pump part differential pressure) between the pump suction part pressure of the recirculation pump 1 and the core inlet part pressure, and the recirculation pump 1 of the recirculation pump 1 previously determined based on the pump part differential pressure. The core flow rate is obtained from the QH (flow rate-lift) characteristic curve.

  This method will be described with reference to FIG. In FIG. 11, the recirculation pump 1 is arrange | positioned at the lower part of the reactor pressure vessel 3, and the coolant outside the shroud 5 is driven below. The coolant that has passed through the recirculation pump 1 passes through the core support plate 6 upward, and is sent to the core portion above it.

  As shown in FIG. 11, the differential pressure between the inlet pressure of the recirculation pump 1 and the core inlet pressure pressurized by the recirculation pump 1 by the pump pressure differential measurement pipe 9 in the reactor pressure vessel 3 (pump portion). The differential pressure ΔPp) is detected and input to the pump unit differential pressure transmitter 10. The pump unit differential pressure ΔPp measured by the pump unit differential pressure transmitter 10 is input to the process computer 11. Further, the RIP rotational speed Ri from the RIP rotational speed detector 12 that detects the rotational speed of the recirculation pump 1 is input to the process computer 11, and the recirculation pump 1 detected by the RPV bottom drain temperature detector 13. The temperature of the reactor coolant passing through (RPV bottom drain temperature) Tb is input.

  The process computer 11 stores in advance a pump QH characteristic curve for each recirculation pump 1 as the pump performance of the recirculation pump 1. This pump QH characteristic curve is a characteristic curve obtained in a factory test, and is held as a fitting equation based on a higher-order linear equation as shown in equation (1). The measured RPV bottom drain temperature Tb, RIP rotational speed Ri, and pump part differential pressure ΔPp are substituted into equation (1) to determine the flow rate Qi of each unit of the recirculation pump 1, and the core flow rate as shown in equation (2) Obtain Wpdp.

Qi = fi (ΔPp, Ri, Tb) (1)
Wpdp = Kp · ΣQi (2)
Here, Kp is a calibration coefficient.

  Next, the CPdP method, which is another core flow rate measurement method, measures the pressure difference (core support plate differential pressure) between the core inlet pressure and the core outlet pressure, and the core support plate differential pressure and reactor average output. From this, the core flow rate is obtained.

  That is, as shown in FIG. 11, the differential pressure on the upper and lower sides of the core support plate 6 is detected by the core support plate differential pressure measuring pipe 14 and is input to the core support plate differential pressure transmitter 15. The core support plate differential pressure (lower lattice plate differential pressure) ΔPcp measured at 15 is input to the nuclear instrumentation system 16. Further, the nuclear instrumentation system 16 receives the neutron flux Φ in the reactor detected by the in-core neutron detector 17. In the nuclear instrumentation system 16, an average value of local outputs in the reactor is obtained based on the detected neutron flux Φ, and an average output A of the reactor is obtained. Then, the core flow rate Wcpdp is obtained by substituting the measured core support plate differential pressure ΔPcp and the average power A of the reactor into the equation (3).

Wcpdp
= Kc · (a + b√ΔPcp + c · ΔPcp) · (d + e · A + f · A ² ) (3)
Here, a, b, c, d, e, and f are constants, ΔPcp is the core support plate differential pressure, A is the average power of the reactor, and Kc is a calibration coefficient.

  On the other hand, in boiling water nuclear power plants, impurities such as metal ions and cladding contained in the reactor coolant adhere to the surface of the pump and the internal structure of the reactor due to the operation of the reactor. There is a possibility that the performance of the reactor will decrease and the flow resistance coefficient of the reactor core will increase over time.

  That is, since the core flow rate Wcpdp obtained by the CPdP method is the core flow rate obtained from the core support plate differential pressure ΔPcp and the reactor power, the change in the reactor power distribution, the cladding into the reactor over time, etc. By the adhesion, the relationship between the core support plate differential pressure ΔPcp and the actual core flow rate changes.

  For this reason, the core flow rate Wcpdp obtained by the CPdP method is obtained with a predetermined accuracy by performing the following calibration. That is, when the deviation between the core flow rate Wpdp and the core flow rate Wcpdp exceeds a predetermined value on the basis of the core flow rate Wpdp obtained by the PdP method not affected by the core state, the core flow rate Wcpdp is adjusted to the core flow rate Wpdp. Accordingly, the calibration coefficient Kc in the equation (3) is reset. Thus, the core flow rate Wcpdp obtained by the CPdP method is also set to a sufficiently accurate core flow rate.

  The core flow rate Wpdp obtained by the PdP method is used for core performance calculation, and the core flow rate Wcpdp obtained by the CPdP method is displayed on a display device (CRT, liquid crystal display device, etc.) and used for monitoring. Is used as a variable to operate the Scrum interlock.

  However, as described above, when the cladding contained in the reactor coolant adheres to the reactor internal structure and not only changes the core support plate differential pressure, but also adheres to the impeller portion of the recirculation pump, etc. The pump performance changes. For this reason, since the relationship between the pump differential pressure ΔPp and the actual core flow rate also changes, the core flow rate by the PdP method cannot be used as a reference.

  For this reason, the core flow rate calculated by the core thermal hydraulic calculation code from the measured value of the core differential pressure or core support plate differential pressure and the measured value of the reactor power is used as the reference flow rate, and the deviation from the calculated reference flow rate is a predetermined value. When the value exceeds the value, the calibration coefficient Kp in the equation (2) and the calibration coefficient Kc in the equation (3) are reset.

  However, the calculation value by the core thermal hydraulic calculation code described above cannot be avoided if the pressure loss characteristic of the core portion changes due to adhesion of cladding or the like to the reactor internal structure. For this reason, the rate of increase in the flow resistance coefficient of the reactor core is determined from the change in the slope of the straight line indicating the correlation between the core differential pressure or the core support plate differential pressure and the pump section differential pressure, and this value is used to determine the core heat A method of correcting a core flow rate calculation value by a hydraulic calculation code (see Patent Document 1 hereinafter, this method is called a differential pressure gradient method) has been devised.

  In addition, the flow rate and temperature values measured at the entrance and exit of the reactor pressure vessel and the thermal energy in the reactor pressure vessel are methods that are not affected in principle by the adhesion of cladding, etc. to the pump and reactor internal structure. A method called a heat balance method has been devised in which the core flow rate is obtained by calculation using an expression describing the balance (see, for example, Patent Document 2).

  Also, the core flow calculated value by the core thermal hydraulic calculation code is compared with the core flow calculated value by the heat balance method, and when the difference exceeds a predetermined size, the core hot water such as the cladding thickness of the fuel surface It has also been devised to adjust the input constant of the force calculation code to correct the core flow rate calculation value by the core thermal hydraulic calculation code (see Patent Document 3).

Separately, the core flow calculated based on the pressure difference between the pump part differential pressure and the core support plate differential pressure and the flow coefficient obtained in advance is used as the reference core flow rate, and the core flow rate by the PdP method and the core flow rate by the CPdP method are used. It has also been devised to calibrate the calculated values by the PdP method and the CPdP method when the deviation between the reference core flow rate exceeds a predetermined value (see Patent Document 4).
JP 2003-57384 A JP 2003-315484 A JP 2001-141874 A JP 11-237493 A

  In the above-described conventional core coolant flow rate measuring device, calibration is performed only after the deviation from the reference core flow rate exceeds a predetermined value, so the indicated value of the core flow rate shows a discontinuous change before and after calibration. There was a problem. In addition, in correcting the deviation from the reference flow rate, no correction based on the measured values of the concentration of impurities such as metal ions and cladding in the reactor coolant is performed. There is a problem that the reason for setting the calibration coefficient is not clear because it is not known whether it is due to adhesion of the above or other causes.

  The present invention has been made in response to such a conventional situation, and continuously corrects the influence on the core flow rate measurement due to adhesion of metal ions, cladding, etc. in the reactor coolant of the boiling water reactor. The purpose is to enable measurement with higher accuracy.

  In order to achieve the above object, a reactor core coolant flow rate measuring device for a boiling water reactor according to the present invention includes a pump unit differential pressure of a recirculation pump that circulates a reactor coolant, a rotational speed of the recirculation pump, and A first signal input unit for inputting a reactor coolant temperature; a pump unit based on an input value input by the first signal input unit and a predetermined QH characteristic curve of the recirculation pump; From the core flow rate calculation processing unit having a core flow rate calculation unit for calculating the core flow rate by the differential pressure measurement method, the second signal input unit for inputting the metal ion concentration in the reactor coolant, and the input value of the metal ion concentration A flow deviation estimation unit for estimating a core flow deviation, a core flow correction unit for calculating a difference between the core flow and the core flow deviation as a new core flow measurement value, and an output unit for outputting the core flow measurement value With the core flow rate correction processor Characterized by comprising a.

  Further, the method for measuring the core coolant flow rate in a boiling water reactor according to the present invention includes a pump section differential pressure of a recirculation pump for circulating the reactor coolant, a rotation speed of the recirculation pump, and a reactor coolant temperature. Based on the first input step to be input, the input value input in the first input step, and the QH characteristic curve of the recirculation pump determined in advance, the core flow rate is measured by the pump unit differential pressure measurement method. A core flow rate calculating step for calculating, a second input step for inputting the metal ion concentration in the reactor coolant, and a flow rate deviation estimating step for estimating the core flow rate deviation from the input value input in the first input step. And a core flow rate correction step for calculating a difference between the core flow rate and the core flow rate deviation as a new core flow rate measurement value, and an output step for outputting the core flow rate measurement value.

  According to the present invention, it is possible to continuously correct the influence on the core flow rate measurement due to adhesion of metal ions, cladding, etc. in the reactor coolant of the boiling water reactor, and more accurate measurement is possible. Become.

  Embodiments of a core coolant flow rate measuring device for a boiling water reactor according to the present invention will be described below with reference to the drawings.

[First Embodiment]
A first embodiment will be described with reference to FIGS.

  In FIG. 1, the present embodiment includes a first signal input unit 21 for inputting a pump unit differential pressure ΔPp of a recirculation pump of a boiling water reactor, a rotational speed Ri of the recirculation pump, and a reactor coolant temperature Tb. A core flow rate calculation processing unit 20 comprising a Wpdp calculation unit 22 for calculating the core flow rate Wpdp by the PdP method based on the input value and a predetermined QH characteristic curve of the recirculation pump, and in the reactor coolant The second signal input unit 31 for inputting the metal ion concentration signal 18 of the gas, the flow rate deviation estimation unit 32 for estimating the core flow rate deviation ΔWpdp from the input value of the metal ion concentration, and the difference between the core flow rate Wpdp and the core flow rate deviation ΔWpdp Is calculated as a new core flow rate estimation value Wc, and a core flow rate correction processing unit 30 including an output unit 34 that outputs the core flow rate measurement value Wc.

  As shown in FIG. 2, the flow rate deviation estimation unit 32 includes a cladding adhesion effect estimation unit 40, a cladding peeling effect estimation unit 41, and a filter unit 42. Details of the configuration of the flow rate deviation estimation unit 32 are shown in FIG. Each of the clad adhesion effect estimating unit 40 and the clad peeling effect estimating unit 41 includes a dead band element 50 or 50 'connected in series and an estimator 51 or 51' using a first-order lag model. However, the dead zone elements 50 and 50 'and the parameters of the estimators 51 and 51' are usually set to different values.

  The operation of the flow rate deviation estimation unit 32 of the first embodiment will be described with reference to FIG. In FIG. 3, the input signal of the core flow deviation estimation unit 32 is a metal ion concentration in the reactor coolant that has the greatest influence on the pump unit differential pressure signal, for example, a chromium ion concentration. The signal input to the cladding adhesion effect estimation unit 40 is first input to the dead zone element 50 having a threshold zone Zp corresponding to the solubility of chromium ions in the dead zone width. The output of the dead band element 50 is input to an estimator 51 configured using a first order lag model. The time constant Tp and the gain Ap, which are parameters of the first-order lag model of the estimator 51, are set in advance so as to reproduce the actual increase phenomenon of the core flow rate deviation. Thus, when the value of the input chromium ion concentration exceeds the threshold value Zp, the output of the estimator 51, that is, the output of the clad adhesion effect estimating unit 40, has a recirculation pump QH characteristic due to clad adhesion. An estimated value of the increase amount of the core flow rate deviation caused by the change of is output.

  The output of the cladding adhesion effect estimation unit 40 is input to the dead band element 50 ′ of the cladding peeling effect estimation unit 41 and the filter unit 42 connected in parallel with the cladding peeling effect estimation unit 41. The dead zone element 50 'has a dead zone width that is the core flow rate deviation value Zm when the recirculation pump QH characteristics start to change due to the adhering clad starting to peel. The output of the dead band element 50 'is input to an estimator 51' configured using a first order lag model. The time constant Tm and the gain Am, which are parameters of the first-order lag model of the estimator 51 ', are set in advance so as to reproduce the saturation phenomenon of the actual core flow rate deviation.

  Thus, when the estimated value of the increase in the core flow deviation input to the cladding peeling effect estimation unit 41 exceeds the threshold value Zm, the output of the estimator 51 ′, that is, the output of the cladding peeling effect estimation unit 41 is An estimated value of the reduction amount of the core flow rate deviation caused by the change of the recirculation pump QH characteristics due to the peeling of the clad is output.

  The filter unit 42 is configured, for example, as a filter having a first-order lag characteristic, and reduces fluctuations unrelated to changes in the core flow rate included in the measurement signal of the chromium ion concentration in the reactor coolant. A value obtained by subtracting the output of the cladding peeling effect estimation unit 41 from the output of the filter unit 42 is output from the flow rate deviation estimation unit 32 as an estimated value ΔWpdp of the core flow rate deviation. The time constant Tf, which is a parameter of the first-order lag characteristic of the filter unit 42, is set to a value such that unnecessary fluctuation does not appear in the estimated value of the core flow rate deviation, and the gain Af is normally set to 1.

  The core flow rate Wpdp calculated by the core flow rate calculation processing unit 20 and the core flow rate deviation estimated value ΔWpdp are input to the core flow rate correction unit 33 shown in FIG. 1, and the core flow rate measurement value Wc corrected by the calculation of equation (4) is given. Is calculated and output from the output unit 34.

Wc = Wpdp−ΔWpdp (4)
An example to which the core flow rate measuring device of this embodiment is applied is shown in FIG. FIG. 4A shows a reference core flow rate regarded as a true core flow rate, and FIG. 4B shows a PdP-based core flow rate Wpdp calculated by the core flow rate calculation processing unit of FIG. 4C shows the chromium ion concentration in the reactor water obtained by the signal input unit 2 in FIG. 1, and the bold line in FIG. 4D is calculated by the flow rate deviation estimation unit 32 in FIG. It is an estimated value of core flow deviation. In FIG. 4 (d), the reference value of the core flow deviation, which is the difference between FIG. 4 (b) and FIG. 4 (a), is indicated by a thin line, but the core flow rate determined from the chromium ion concentration in FIG. 4 (c). It is confirmed that the estimated deviation is in good agreement with the reference value. Here, Zp = Zm = 2, Tp = Tm = 500, Ap = Am = 1.25, Tf = 200, and Af = 1 are given to the parameters shown in FIG.

  According to this embodiment, the concentration of metal ions in the reactor coolant increases and adheres to the impeller portion of the recirculation pump as a cladding, and the recirculation pump Q-H characteristics change, thereby changing the core flow rate by the PdP method. Even when a deviation occurs in the calculated value, correction is continuously performed by directly using the measured value of the metal ion concentration in the reactor coolant. Therefore, only the effect due to the clad adhesion is appropriately corrected, and a discontinuous change does not occur in the corrected core flow rate calculation value.

[Second Embodiment]
Next, a second embodiment of the core coolant flow rate measuring device for a boiling water reactor according to the present invention will be described with reference to FIG. 1, FIG. 2, and FIG. In addition, the same code | symbol is attached | subjected to the structure same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

  The present embodiment is configured as shown in FIGS. 1 and 2 as in the first embodiment, and the cladding adhesion effect estimation unit 40 and the cladding peeling effect estimation unit 41 in FIG. As shown, the dead zone element 50 or 50 'connected in series and an estimator 52 or 52' using a one-input autoregressive model are included. In other words, the configuration of the flow rate deviation estimation unit 32 in the present embodiment is such that the two estimators 51 and 51 ′ in FIG. 3 shown in the first embodiment are each an estimator 52 using a one-input autoregressive (ARX) model. , 52 ′.

  Therefore, as in the first embodiment, the dead zone element 50 of the cladding adhesion effect estimation unit 40 also has a threshold value Zp corresponding to the solubility of the metal ion concentration in this embodiment, and the dead zone of the cladding peeling effect estimation unit 41. The element 50 ′ has a threshold value Zm for starting the cladding peeling phenomenon with respect to the increase in the core flow rate deviation.

  This embodiment is different from the first embodiment in that a one-input autoregressive model is used for the estimators 52 and 52 '. The estimator 52 of the clad adhesion effect estimation unit 40 generates a core flow rate deviation caused by a change in the recirculation pump QH characteristics due to clad adhesion when the input metal ion concentration X exceeds the threshold value Zp. The amount of increase ΔWpdp is calculated by equation (5).

ΔWpdp (k) = B (q) · {X (k) −Zp} / A (q) (5)
^{_{However, A (q) = 1 +}} a 1 q -1 + ··· + a na q -na
B (q) = b ₁ q ⁻¹ +... + B _nb q ^−nb
Here, q is a time shift operator, and k represents time tk. The model parameters a ₁ ,..., A _na , b ₁ ..., B _nb are set in advance so as to reproduce the actual increase phenomenon of the core flow rate deviation. At this time, from among the parameters of the model obtained by changing the orders na and nb, the order and parameter set that minimizes the final prediction error (FPE) calculated by Expression (6) is used.

FPE
= [{1+ (na + nb) / N}] / {1- (na + nb) / N}]. (V / N)
(6)
In Equation (6), N is the number of data points when the actual core flow deviation is increased, and V is the order na, nb and the parameters a ₁ ,..., A _na , b _1.・ ・_Represents the variance of the error of the core flow deviation estimated value calculated by giving b _nb (refer to “Statistical analysis and control of dynamic system” for the FPE concept, for example).

  The estimator 52 ′ of the cladding peeling effect estimation unit 41 can use a one-input autoregressive model that is the same order as the estimator 52 of the cladding adhesion effect estimation unit 40 and is different only in gain A (q).

  As described above, according to the core coolant flow rate measuring device of the present embodiment, a one-input autoregressive model is used instead of the estimator using the first-order lag model of the core coolant flow rate measuring device of the first embodiment. It is expected that the core flow rate deviation generated by the change of the recirculation pump Q-H characteristics due to the adhesion of the clad can be appropriately estimated. .

[Third Embodiment]
Next, a third embodiment of the core coolant flow rate measuring device for a boiling water reactor according to the present invention will be described with reference to FIG. 1, FIG. 2, and FIG.

  The present embodiment is configured as shown in FIGS. 1 and 2 similarly to the first embodiment, but the signal 18 input to the second signal input unit 31 affects the pump unit differential pressure signal. It consists of a plurality of signals such as a plurality of metal ion concentrations in a possible reactor coolant, such as a chromium ion concentration, a nickel ion concentration, an iron cladding concentration, etc.

  A case where the concentrations of two types of metal ions Xa and Xb are input to the second signal input unit 31 will be described as an example. As shown in FIG. 6, the clad adhesion effect estimating unit 40 includes a dead zone element 50a to which the concentration of the metal ion Xa is input, an estimator 51a using a first order lag model to which the output of the dead zone element 50a is input, and the metal ion A dead zone element 50b to which the concentration of Xb is input and an estimator 51b using a first-order lag model to which the output of the dead zone element 50b is input. The clad stripping effect estimation unit 41 and the filter unit 42 are configured in the same manner as in the first embodiment shown in FIG. Therefore, the third embodiment is different from the first embodiment in that the second signal input unit 31 and the cladding adhesion effect estimation unit 40 are configured to process a plurality of metal ion concentration inputs. It is.

  The operation of the cladding adhesion effect estimating unit 40 in this embodiment will be described with reference to FIG. In FIG. 6, the concentration of the input metal ion Xa is first input to a dead zone element 50a having a threshold zone Zpa corresponding to the solubility of the metal ion Xa in the dead zone width. The output of the dead band element 50a is input to an estimator 51a configured using a first-order lag model. The concentration of the metal ion Xb, which is another input, is first input to the dead zone element 50b having a threshold zone Zpb corresponding to the solubility of the metal ion Xb as the dead zone width. The output of the dead band element 50b is input to an estimator 51b configured using a first-order lag model. The sum of the outputs of the two estimators 51a and 51b is output from the cladding adhesion effect estimation unit 40.

  The time constants Tpa and Tpb and the gains Apa and Apb, which are parameters of the first-order lag models of the estimators 51a and 51b, are set in advance so as to reproduce the actual increase phenomenon of the core flow rate deviation. Thus, when the input values of the plurality of metal ion concentrations exceed the respective threshold values Zpa and / or Zpb, the output of the cladding adhesion effect estimating unit 40 includes the concentrations of the metal ions Xa and / or Xb. The recirculation pump Q-H characteristic changes due to adhesion of the clad having increased, and an estimated value of the increase in the core flow deviation caused by this is output.

  As described above, according to the present embodiment, the concentration of a plurality of metal ions in the reactor coolant increases and adheres to the impeller portion of the recirculation pump as a clad, and the recirculation pump QH characteristics are improved. Even when a deviation occurs in the core flow rate calculation value by the PdP method due to the change, the correction is continuously performed by directly using the plurality of measured metal ion concentrations in the reactor coolant. Therefore, only the effect due to the clad adhesion is appropriately corrected, and a discontinuous change does not occur in the corrected core flow rate calculation value.

[Fourth Embodiment]
Next, a fourth embodiment of the boiling water reactor core coolant flow rate measuring apparatus according to the present invention will be described with reference to FIGS. 1, 2 and 7. FIG.

  This embodiment is configured as shown in FIG. 1 and FIG. 2 as in the second embodiment. Here, as in the case of the third embodiment, the signal 18 input to the second signal input unit 31 has a plurality of reactor coolants that may affect the pump unit differential pressure signal. It consists of a plurality of signals such as metal ion concentration, such as chromium ion concentration, nickel ion concentration, iron clad concentration.

  Similarly to FIG. 6 shown in the third embodiment, a case where the concentrations of two types of metal ions Xa and Xb are input to the second signal input unit 31 will be described as an example. As shown in FIG. 7, the clad adhesion effect estimation unit 40 includes a dead zone element 50a to which the concentration of the metal ion Xa is input, a dead zone element 50b to which the concentration of the metal ion Xb is input, and two dead zone elements 50a and 50b. Is an estimator 53 using a multi-input autoregressive model. Moreover, the clad peeling effect estimation part 41 and the filter part 42 are comprised similarly to 2nd Embodiment shown in FIG. Therefore, the fourth embodiment is different from the second embodiment in that the second signal input unit 31 and the cladding adhesion effect estimation unit 40 are configured to be able to process inputs of a plurality of metal ion concentrations. It is.

  The operation of the clad adhesion effect estimation unit 40 in this embodiment will be described with reference to FIG. In FIG. 7, the concentration of the input metal ion Xa is first input to the dead zone element 50a having a threshold zone Zpa corresponding to the solubility of the metal ion Xa in the dead zone width. The concentration of the metal ion Xb, which is another input, is first input to the dead zone element 50b having a threshold zone Zpb corresponding to the solubility of the metal ion Xb as the dead zone width. The outputs of the two dead zone elements 50a and 50b are input to an estimator 53 configured using a multi-input autoregressive model.

  The estimator 53 calculates an estimated value of the increase in the core flow deviation caused by the change of the recirculation pump QH characteristic due to the adhesion of the clad by the calculation formula similar to the formula (5). The output of the adhesion effect estimation unit 40 is used. However, in this case, the right side X of Equation (5) is a column vector whose elements are the concentrations of metal ions Xa and Xb, Zp is a column vector whose elements are threshold values Zpa and Zpb, and the coefficient B (q) is This is a row vector having Bj (q) defined by Expression (7) as an element.

Bj (q) = b _1j q ⁻¹ +... + B _nbj q ^−nb (7)
Here, the model order na of, nb is the value that the FPE of formula (6) to a minimum, the parameters _{a 1, ···, a na,} b 1 ···, b nb are the actual core flow deviation increases A value that can reproduce the phenomenon is set in advance.

  As described above, according to this embodiment, the same effect as that of the third embodiment is expected. That is, the concentration of a plurality of metal ions in the reactor coolant increases and adheres to the impeller portion of the recirculation pump as a clad, and the recirculation pump QH characteristics change, so that the core flow rate calculation value by the PdP method is obtained. Even if a deviation occurs, the correction is continuously performed by directly using a plurality of measured values of the metal ions in the reactor coolant, so that only the effect due to the clad adhesion is appropriately corrected. There is no discontinuous change in the core flow rate calculation.

  Further, in the present embodiment, the core flow deviation is estimated using a multi-input autoregressive model instead of a plurality of estimators using the first-order lag model constituting the cladding adhesion effect estimating unit 40 in the third embodiment. Therefore, it is expected that highly accurate estimation will be possible.

[Fifth Embodiment]
Next, a fifth embodiment of the core coolant flow rate measuring device for a boiling water reactor according to the present invention will be described with reference to FIGS.

  The present embodiment is configured as shown in FIG. 1 as in the first embodiment, and the flow rate deviation estimation unit 32 of FIG. 1 estimates the cladding adhesion effect connected in parallel as shown in FIG. Part 40 and a clad peeling effect estimating part 41. The cladding adhesion effect estimation unit 40 and the cladding separation effect estimation unit 41 are configured as shown in FIG. 9, for example, and the difference between the output of the cladding adhesion effect estimation unit 40 and the cladding separation effect estimation unit 41 is an estimated value of the core flow rate deviation. Is output from the flow rate deviation estimation unit 32.

  The operation of the flow rate deviation estimation unit 32 in this embodiment will be described with reference to FIG. In FIG. 9, the input signal of the core flow rate deviation estimation unit 32 is the metal ion concentration in the reactor coolant that has the largest influence on the pump unit differential pressure signal, for example, the chromium ion concentration, and the operation of the cladding adhesion effect estimation unit 40. Is the same as in the first embodiment.

  On the other hand, unlike the case of the first embodiment, the value of the metal ion concentration is directly input to the cladding peeling effect estimation unit 41. That is, the dead zone element 50 ′ has a dead zone width that is the density Zm when the clad deposited due to an increase in the metal ion concentration starts peeling, and its output is input to an estimator 51 ′ configured using a first-order lag model. The The time constant Tm and the gain Am, which are parameters of the first-order lag model of the estimator 51 ', are set in advance so as to reproduce the actual saturation phenomenon of the core flow rate deviation. Thus, when the metal ion concentration input to the clad peeling effect estimation unit 41 exceeds the threshold value Zm, the output of the estimator 51 ′, that is, the output of the clad peeling effect estimation unit 41 is regenerated by the clad peeling. An estimated value of a decrease amount of the core flow rate deviation caused by the change of the circulation pump QH characteristic is output.

  As described above, according to the core coolant flow rate measuring device of this embodiment, the same effect as that shown in the first embodiment is expected. That is, the concentration of metal ions in the reactor coolant increases and adheres to the impeller portion of the recirculation pump as a cladding, and the recirculation pump QH characteristic changes, so that there is a deviation in the calculated core flow rate by the PdP method. Even if it occurs, correction is continuously performed by directly using the measured value of the metal ion concentration in the reactor coolant. Therefore, only the effect due to the clad adhesion is appropriately corrected, and a discontinuous change does not occur in the corrected core flow rate calculation value.

[Sixth Embodiment]
Next, a sixth embodiment of the core coolant flow rate measuring device for a boiling water reactor according to the present invention will be described with reference to FIG.

  In FIG. 10, the present embodiment includes a first signal input unit 21 ′ for inputting the core support plate differential pressure ΔPcp of the boiling water reactor and the average output A of the reactor, and the core by the CPdP method based on the above input values. A core flow rate calculation processing unit 20 comprising a Wcpdp calculation unit 22 ′ for calculating a flow rate Wcpdp, a second signal input unit 31 for inputting a metal ion concentration 18 in the reactor coolant, and an input value of the metal ion concentration. A flow deviation estimation unit 32 that estimates the deviation ΔWcpdp, a core flow correction unit 33 that calculates a difference between the core flow rate Wcpdp and the core flow deviation ΔWcpdp as a new core flow measurement value Wc, and an output that outputs the core flow measurement value Wc And a core flow rate correction processing unit 30 including the unit 34. The flow rate deviation estimation unit 32 is configured, for example, in the same manner as in FIGS. 2 and 3 shown in the first embodiment.

  Therefore, according to the core coolant flow rate measuring device of the present embodiment, the same correction effect as shown for the core flow rate calculation value by the PdP method in the first embodiment with respect to the core flow rate calculation value by the CPdP method. There is expected. That is, even when the concentration of metal ions in the reactor coolant increases and adheres to the reactor internal structure as a cladding, and the core flow pressure loss characteristics change, there is a deviation in the calculated core flow rate by the CPdP method. The correction is continuously performed by directly using the measured value of the metal ion concentration in the reactor coolant. Therefore, only the effect due to the clad adhesion is appropriately corrected, and a discontinuous change does not occur in the corrected core flow rate calculation value.

  In the natural circulation boiling water reactor assumed as one of the future nuclear reactors, there is a high possibility that a core flow measuring device by the CPdP method will be installed. The device is expected to be applicable.

[Other Embodiments]
The embodiments described above are merely examples, and the present invention is not limited to these. For example, in each of the above embodiments, if the variation in the measured value of the metal ion concentration in the reactor coolant is small, it is not necessary to provide the filter unit 42 in the flow rate deviation estimation unit 32. Furthermore, in a nuclear power plant where the change in the metal ion concentration does not become so large that the core flow rate deviation caused by the change in the core pressure loss characteristic or the recirculation pump QH characteristic shows the saturation characteristic, the flow deviation estimation unit 32. In this case, it is not necessary to provide the clad peeling effect estimating section 41.

  In setting the models used for the estimators 51 to 53, the actual core flow rate deviation may be used. The core flow rate used as a reference at this time is the core by the heat balance method or the differential pressure gradient method. A flow rate can be used.

  In FIG. 1 shown in the first embodiment and FIG. 10 shown in the sixth embodiment, the case where the core coolant flow rate measuring device is configured independently of the conventional measuring device is shown. The processing unit 20 can also use a conventional measuring device as it is. That is, in the case of the core flow rate measuring device using the PdP method, the core flow rate calculation is performed in the process computer 11 as shown in FIG. 11, and the core flow rate correction processing unit 30 in FIG. It is also possible to do it easily. On the other hand, the calculation of the core flow rate by the CPdP method is performed in the nuclear instrumentation system 16, and only the calculation result can be input to the core flow rate correction processing unit 30 in FIG.

The block diagram which shows the structure of 1st Embodiment of the core coolant flow rate measuring apparatus which concerns on this invention. The block diagram which shows schematic structure of the flow volume deviation estimation part in the core coolant flow measuring device of FIG. The block diagram which shows the structure of the flow volume deviation estimation part of FIG. 1 and FIG. It is a time chart which shows the example of the core flow deviation deviation estimation result by 1st Embodiment of the core coolant flow measuring device concerning this invention, (a) is a graph which shows a reference | standard core flow, (b) is a PdP method core. The graph which shows flow volume, (c) is a graph which shows chromium ion concentration, (d) is a graph which shows a core flow rate deviation. The block diagram which shows the structure of the flow volume deviation estimation part in 2nd Embodiment of the core coolant flow measuring device which concerns on this invention. The block diagram which shows the structure of the clad adhesion effect estimation part in 3rd Embodiment of the core coolant flow rate measuring apparatus which concerns on this invention. The block diagram which shows the structure of the clad adhesion effect estimation part in 4th Embodiment of the core coolant flow measuring device which concerns on this invention. The block diagram which shows schematic structure of the flow volume deviation estimation part in 5th Embodiment of the core coolant flow measuring device which concerns on this invention. The block diagram which shows the structure of the flow volume deviation estimation part in 5th Embodiment of the core coolant flow measuring device which concerns on this invention. The block diagram which shows the structure of 6th Embodiment of the core coolant flow rate measuring apparatus which concerns on this invention. Explanatory drawing of the measurement system in connection with the core flow volume measurement of the conventional boiling water reactor.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Recirculation pump, 3 ... Reactor pressure vessel, 5 ... Shroud, 6 ... Core support plate, 9 ... Pump part differential pressure measurement piping, 10 ... Pump part differential pressure transmitter, 11 ... Process computer, 12 ... RIP rotation Number detector, 13 ... RPV bottom drain temperature detector, 14 ... Core support plate differential pressure measurement piping, 15 ... Core support plate differential pressure transmitter, 16 ... Nuclear instrumentation system, 17 ... In-core neutron detector, 18 ... Reactor Underwater metal ion concentration signal, 19 ... Average output of reactor, 20 ... Core flow rate calculation processing unit, 21, 21 '... Signal input unit, 22 ... Wpdp calculation unit, 22' ... Wcpdp calculation unit, 30 ... Core flow rate correction processing 31 ... Signal input unit 32 ... Flow rate deviation estimation unit 33 ... Core flow rate correction unit 34 ... Output unit 40 ... Clad adhesion effect estimation unit 41 ... Clad peeling effect estimation unit 42 ... Fi 50, 50 ', 50a, 50b ... dead zone elements, 51, 51', 51a, 51b ... estimator based on a first-order lag model, 52, 52 '... estimator based on a one-input autoregressive model, 53 ... multi-input self Estimator with regression model

Claims (11)

A core coolant flow measuring device for a boiling water reactor,
A first signal input unit for inputting a differential pressure of the recirculation pump for circulating the reactor coolant, a rotation speed of the recirculation pump, and a temperature of the reactor coolant, and the first signal input unit. A core flow rate calculation processing unit having a core flow rate calculation unit for calculating a core flow rate by a pump unit differential pressure measurement method based on the input value and a predetermined QH characteristic curve of the recirculation pump;
A second signal input unit for inputting a metal ion concentration in the reactor coolant, a flow rate deviation estimation unit for estimating a core flow rate deviation from the input value of the metal ion concentration, and a difference between the core flow rate and the core flow rate deviation. A core flow rate correction unit that calculates a new core flow rate measurement value, and a core flow rate correction processing unit that includes an output unit that outputs the core flow rate measurement value;
A core coolant flow rate measuring device characterized by comprising: A core coolant flow measuring device for a boiling water reactor,
A core flow rate calculation process having a first signal input unit for inputting the core support plate differential pressure and the average power of the reactor, and a core flow rate calculation unit for calculating the core flow rate from the input value by a core support plate differential pressure measurement method. And
A second signal input unit for inputting a metal ion concentration in the reactor coolant, a flow rate deviation estimation unit for estimating a core flow rate deviation from the input value of the metal ion concentration, and a difference between the core flow rate and the core flow rate deviation. A core flow rate correction unit that calculates a new core flow rate measurement value, and a core flow rate correction processing unit that includes an output unit that outputs the core flow rate measurement value;
A core coolant flow rate measuring device characterized by comprising:   The flow rate deviation estimation unit inputs the metal ion concentration in the reactor coolant to the cladding adhesion effect estimation unit, and outputs the cladding adhesion effect estimation unit to the filter unit and the cladding peeling effect estimation unit connected in parallel with the filter unit; The core coolant flow rate measurement according to claim 1 or 2, wherein the difference between the output of the filter unit and the output of the cladding peeling effect estimation unit is output as an estimated value of the core flow rate deviation. apparatus.   The flow deviation estimation unit inputs the metal ion concentration in the reactor coolant to the cladding adhesion effect estimation unit and the cladding peeling effect estimation unit connected in parallel with the cladding adhesion effect estimation unit, and outputs the cladding adhesion effect estimation unit 3. The core coolant flow rate measuring device according to claim 1, wherein a difference between the output of the clad separation effect estimating unit and the output of the cladding peeling effect estimation unit is output as an estimated value of the core flow rate deviation.   The said clad adhesion effect estimation part and a clad peeling effect estimation part each have a dead zone element mutually connected in series, and the estimator by a first order lag model, The Claim 3 or Claim 4 characterized by the above-mentioned. Core coolant flow rate measuring device.   The said clad adhesion effect estimation part and a clad peeling effect estimation part respectively have a dead zone element mutually connected in series, and the estimator by 1 input autoregressive model, The Claim 3 or Claim 4 characterized by the above-mentioned. The core coolant flow rate measuring device described.   The cladding adhesion effect estimation unit includes a plurality of dead band elements each of which receives a plurality of measured values of metal ion concentrations, and a plurality of first-order lag model estimators connected in series to each of the dead band elements. The core coolant flow rate measuring device according to claim 3.   The cladding adhesion effect estimation unit and the cladding peeling effect estimation unit are based on a plurality of dead band elements each having a plurality of measured values of metal ion concentrations as inputs, and a plurality of first order lag models connected in series to each of the dead band elements. The core coolant flow rate measuring device according to claim 4, further comprising an estimator.   The clad adhesion effect estimation unit includes a plurality of dead band elements each receiving measurement values of a plurality of metal ion concentrations, and an estimator based on one multidimensional autoregressive model that receives outputs of the plurality of dead band elements. The core coolant flow rate measuring device according to claim 3, wherein the core coolant flow rate measuring device is provided.   The cladding adhesion effect estimating unit and the cladding peeling effect estimating unit are a plurality of dead zone elements each receiving measurement values of a plurality of metal ion concentrations, and one multi-dimensional autoregressive unit receiving outputs of the plurality of dead zone elements The core coolant flow rate measuring device according to claim 4, further comprising a model estimator. A method for measuring a core coolant flow rate in a boiling water reactor,
A first input step of inputting a pump section differential pressure of the recirculation pump for circulating the reactor coolant, a rotation speed of the recirculation pump, and a reactor coolant temperature;
A core flow rate calculating step for calculating a core flow rate by a pump unit differential pressure measurement method based on the input value input in the first input step and a predetermined QH characteristic curve of the recirculation pump;
A second input step for inputting a metal ion concentration in the reactor coolant;
A flow deviation estimating step for estimating a core flow deviation from the input value inputted in the first input step;
A core flow rate correction step for calculating a difference between the core flow rate and the core flow rate deviation as a new core flow rate measurement value;
An output step of outputting the core flow rate measurement value;
A core coolant flow rate measuring method characterized by comprising:

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