Method of determining flow rates in the channels npu

 

The invention relates to measuring technique and can be used to determine flow rates in the channels of nuclear power plants in the measurement of flow through the turbine flow meters of various types. In the method of flow measurement converts rotary motion of the turbine flow meter in the system of electrical impulses. Create an output signal through a survey of the formed system of electrical impulses with a frequency above the limit f>fCRdetermine the number of pulses during the exposure, determine the coolant flow on the basis of previously obtained according to G (n), where fCR- limit frequency; n is the number of pulses measured during exposure, with frequency fAveThe technical result is an increase in the accuracy of determination of the flow. 2 Il., 1 PL.

The invention relates to measuring technique and can be used to determine flow rates in the channels of nuclear power plants in the measurement of flow through the turbine flow meters of various types.

There is a method of flow measurement consists in measuring the confused who entrusted the dependences G = f(P), where G is the measured flow,P - pressure drop across the constriction device (B. N. Preobrazhenskaya. Thermal measurements and instruments. M: Energy, 1978, S. 434).

The main disadvantage of this method is that when measured by this method is difficult to place a narrowing device in large diameter pipes (channels NPU) and output the pulse tube to the datalogger. When installing an orifice in the channel are large pressure loss.

The closest in technical essence and the achieved result is a way of measuring the flow, namely, that converts rotary motion of the turbine flow meter in the system of electrical impulses that create an output signal by generating a pulse of constant duration, convert it into a current signal, integrating the current signal during the exposure time and determine flow based on pre-obtained according to flow from the output signal G = f(I) (H. A. Dollezhal, I. Y. Emelianov. Channel nuclear power reactor. M: Atomizdat, 1980, S. 140). This method of flow measurement is currently used for measuring the flow in the channels of RBMK. In car-32M and SHADR-8A known and described in (A. H. Dollezhal, I. Y. Emelianov. Channel nuclear power reactor. M: Atomizdat, 1980, S. 140). Let us dwell on the disadvantages of the method relating to the removal of the signal and the actual definition of consumption. In Fig.1 shows a diagram that implements the method.

The main disadvantage of this method is that the accuracy of the flow rate is small. The main error of each measurement channel error due to an error of Shadr and the Tiber. If the first one has a narrow dynamic range and S-shaped nonlinearity of the transformation, the second is the error associated with the nonlinearity of 1/S. Increase measurement error and subsequent units of the national Park and the ISU. In addition, there is also a dynamic component of error determined by the smoothing function of the Tiber and converting the analog signal into a digital code. In addition, over time the output signal of the MIP decreases in amplitude, which is associated with degradation parameters working together Ivan Shadr and MIP. Wear and deformation of the ball lead to fluctuations in the rotational speed at a constant flow. All this leads to a change in the originally received calibration characteristics of the form G=f(I), and change harale be different from the actual.

The technical result, which is aimed invention is to improve the accuracy of determining the flow rate of the coolant that is provided by the fact that create an output signal through a survey of the formed system of electrical impulses with a frequency above the limit f > fCRdetermine the number of pulses during the exposure, determine the coolant flow on the basis of previously obtained according to G (n), where fCR- limit frequency; n is the number of pulses measured during exposure with frequency fCR.

Direct use of a single value of n allows to exclude additional links, chains and conversion algorithms in the measuring channel and associated errors.

Limit frequency fCRis determined on the basis of the analysis of the electrical pulses at the output of magnetic induction converters.

In Fig.2 shows the structural scheme of the measuring system to control the flow of water, which implements the proposed method.

Structurally measuring system that implements the proposed method, Fig.2, consists of two identical independent subsystems, each serving half of the reactor. Each subsystem, Merov also evenly divided into three groups and treated in three independent devices.

The method for determining the flow is as follows.

The rotational movement of the turbine flow meter (SHADR-8A and (or) SHADR-32M) is converted into electrical pulses by using magnetic induction transducer MIP, create an output signal through a survey of the formed system of electrical impulses with a frequency above the limit f > fCR. The latter is achieved by using a comparator that converts the frequency signals into digital signals, which form the signal of the logical units in the register, if the time interval measurements were frequency signal of the MIP. If the signal from the MIP was absent, it generates a signal of logical zero. When generating the output signal is the only condition is that the number of measurement intervals per unit time exceed the maximum pulse repetition rate of the MIP at the maximum flow rate. In our case this condition is met if 50 time intervals per second. Counting pulses in a time interval is carried out by software in the computer, where is a matrix of control of water consumption, presented in a frequency format.

As an example, consider the measurement of rashtrakuta with different values (different frequency pulses MIP) depending on the time of the survey. As can be seen from the table, the improved accuracy is achieved by increasing the measurement time, when taken several times and the values averaged. The averaging procedure is based on the assumption that the error due to random factors and tends to zero when averaged over a large ensemble of samples.

The main error transducers is 1,5%. Taking into account errors generate an output signal (table), the total error of the flow measurement will not exceed 2%. When using the known method of measuring the flow rate, which is currently used in nuclear power plants with RBMK, the error in the determination of the flow rate can reach up to 10%.

Thus, the proposed technical solution by eliminating additional channels of the transducer and associated errors allows to improve the accuracy of flow in channels NPU.

Claims

Method of determining flow rates in the channels of the NPP, namely, that converts rotary motion of the turbine flow meter in the system of electrical impulses, wherein creating the output siprelay the number of pulses during the exposure, determine the flow rate of the coolant based on the previously obtained relation is G(n), where fCR- limit frequency, n is the number of pulses measured during exposure with frequency fCR.

 

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