CN104332193A - Steam-generator water-level measure method based on digitization technology - Google Patents

Abstract

The invention belongs to a process measuring method for a nuclear power plant reactor coolant system, and concretely relates to a steam-generator water-level measure method based on a digitization technology. The method comprises the following steps: step 1, acquiring basic parameters; step 2, acquiring basic measure data; and step 3, calculating the water level. The advantages comprise that after the digitization technology is employed, real-time calculation can be performed on thermal expansion of a steam generator self and the density of water in a descending channel, water vapor and reference pipe water when the steam generator is at different measure conditions, the measure system is guaranteed to be capable of directly measuring the actual water level under any work conditions, the measure precision is improved and the burden of operators is mitigated.

Description

steam generator water level measuring method based on digitization technology

Technical Field

The invention belongs to a process measurement method for a reactor coolant system of a nuclear power plant, and particularly relates to a water level measurement method for a steam generator based on a digital technology.

Background

In a nuclear power plant, the water level of a steam generator must be kept at a proper height, the safe operation of the nuclear power plant is endangered when the water level is too high or too low, the water level must be adjusted to a proper height in time, otherwise, the emergency shutdown of a reactor must be triggered, and therefore, the water level of the steam generator is an important protection, control and post-accident monitoring parameter, and the improvement of the measurement precision is necessary for guaranteeing the safe operation of the nuclear power plant.

The water level of the steam generator is usually measured by a differential pressure method, namely, a differential pressure transmitter is used for measuring the differential pressure between an upper pressure taking port and a lower pressure taking port, and then a signal processing system calculates the actual water level in the steam generator according to the differential pressure. The schematic view of the measuring system is shown in fig. 1.

Because the traditional I & C system of the nuclear power plant adopts a simulation technology, a steam generator water level measurement model is simplified, namely, a certain standard working condition is selected for calibration, and when the calibration is carried out, a transmitter outputs 4mA, a lower water level limit corresponds, and when the transmitter outputs 20mA, an upper water level limit corresponds. For other working conditions, the designer calculates the water level corresponding relation and the correction coefficients off-line, and the operator determines the actual water level according to the correction coefficients, as shown in fig. 2.

Although the operation requirement can be met to a certain extent by adopting off-line calculation, the operation personnel is heavily burdened due to poor precision and slow response, and the adverse effect is caused on the safe and economic operation of the power plant.

With the wide application of the digitization technology, for example, the domestic second-phase nuclear power plant in australia, the ridge and australia adopts a fully digitized instrument control platform, the realization of a complex signal processing method becomes feasible and easier, and therefore, from the perspective of improving the safety of the power plant or the human factor engineering level, the improvement of a steam generator water level calculation method adopted in the traditional nuclear power plant is necessary.

Disclosure of Invention

The invention aims to provide a method for measuring the water level of a steam generator based on a digital technology, which can improve the accuracy of measuring the water level of the steam generator under various working conditions, thereby improving the safety and the economy of a nuclear power plant, optimizing a human-computer interface and reducing the burden of operators.

The invention is realized in this way, a steam generator water level measuring method based on digital technology, which includes the following steps:

the method comprises the following steps: obtaining basic parameters;

step two: obtaining basic measurement data;

step three: and calculating the water level.

The first step comprises the following parameters obtained by field measurement:

1) distance d between upper and lower pressure-taking tubes at 20 DEG C_p；

2) Distance d between the equalizing container and the lower pressure tapping pipe at 20 DEG C_r；

The expansion coefficient C of the steam generator is provided by a manufacturer, and the gravity acceleration g is obtained through actual measurement of a plant site of a power plant and is accurate to 2 bits after a decimal point.

The second step comprises the following steps of,

1) the water level differential pressure delta P is obtained through the water level transmitter,

2) obtaining main steam mass flow Q through main steam system measurement_VSpecific enthalpy E_VPressure P_S，

3) The water supply mass flow Q is obtained by the measurement of a main water supply system_FAnd specific enthalpy E_F，E_RIs the specific enthalpy of the return flow.

The third step comprises the following steps of,

1) calculating the circulation multiplying power R

$R=\frac{Q_F-Q_V}{Q_V}$

2) Calculating the specific enthalpy E of the downcomer water_D

$E_D=\frac{(R-1)E_R+E_F}{R}$

3) Calculating the temperature T of the water in the descending passage_DAnd density ρ_D

According to the specific enthalpy E of the water in the descending channel by a calculation method provided by the International Standard IAPWS-IF97 for the thermodynamic properties of Water and Water vapor_DAnd pressure P_SCalculating the temperature T of the water in the descending passage_DAnd density ρ_D，

4) Calculating reference water density ρ_r

Calculated according to the pressure P, by the calculation method provided by the International Standard IAPWS-IF97 for the thermodynamic Properties of Water and Water vapor_SAnd temperature T of the instrument tube_rCalculating the density rho of water in the instrument tube_rIf the instrument tube has no temperature measurement, T can be taken_r=40℃，

5) Calculating the density ρ of the steam_v

The water vapor in the steam generator is in a saturated state and is calculated according to the steam pressure P by the calculation method provided by the International Standard IAPWS-IF97 for the thermal properties of water and water vapor_SCalculating the density ρ of the steam_v，

6) Calculating the distance D from the balance container to the lower pressure tapping pipe_r

D_r=d_r+C(T_D-20)d_p

7) Calculating the actual water level of the steam generator

<math> <mrow> <mi>H</mi> <mo>=</mo> <mfrac> <mrow> <mfrac> <mi>&Delta;P</mi> <mi>g</mi> </mfrac> <mo>-</mo> <msub> <mi>D</mi> <mi>r</mi> </msub> <mrow> <mo>(</mo> <msub> <mi>&rho;</mi> <mi>V</mi> </msub> <mo>-</mo> <msub> <mi>&rho;</mi> <mi>r</mi> </msub> <mo>)</mo> </mrow> </mrow> <mrow> <msub> <mi>&rho;</mi> <mi>D</mi> </msub> <mo>-</mo> <msub> <mi>&rho;</mi> <mi>V</mi> </msub> </mrow> </mfrac> <mo>.</mo> </mrow> </math>

The invention has the advantages that after the digitization technology is adopted, the density of water, vapor and reference pipe water in the descending channel of the steam generator under different measuring working conditions and the thermal expansion of the steam generator body can be calculated in real time, so that the measuring system can ensure that the actual water level can be directly measured under any working conditions, the measuring precision is improved, and the burden of operators is lightened.

Drawings

FIG. 1 is a schematic view of a measurement system;

FIG. 2 is a diagram illustrating a water level correspondence and a correction factor;

FIG. 3 is a calibration diagram of the corresponding relationship between the measured water level of the steam generator and the actual water level of the transmitter under full power.

In the figure, 1 steam generator, 2 balance container, 3 upper pressure tapping pipe, 4 lower pressure tapping pipe and 5 differential pressure transmitter.

Detailed Description

The invention is described in detail below with reference to the following figures and examples:

the invention aims to solve the technical problem that the digital technology is fully utilized to bring convenience on signal processing, and each physical parameter influencing the water level measurement of the steam generator is brought into the calculation process of a measurement system, so that the aim of accurately measuring the actual water level of the steam generator is fulfilled.

A method for measuring the water level of a steam generator based on a digital technology comprises the following steps:

the method comprises the following steps: obtaining basic parameters

After the measurement system is installed, the following parameters are obtained through field measurement:

1) distance d between upper and lower pressure-taking tubes at 20 DEG C_p；

2) Distance d between the equalizing container and the lower pressure tapping pipe at 20 DEG C_r

The expansion coefficient C of the steam generator is provided by a manufacturer, and the gravity acceleration g is obtained through actual measurement of a plant site of a power plant and is accurate to 2 bits after a decimal point.

Step two: obtaining basic measurement data

1) Obtaining water level differential pressure delta P by water level transmitter

2) Obtaining main steam mass flow Q through main steam system measurement_VSpecific enthalpy E_VPressure P_S

3) The water supply mass flow Q is obtained by the measurement of a main water supply system_FAnd specific enthalpy E_F，E_RIn order to return the specific enthalpy of the flow,

step three: water level calculation

The water level calculation is divided into the following steps:

1) calculating the circulation multiplying power R

$R=\frac{Q_F-Q_V}{Q_V}$

2) Calculating the specific enthalpy E of the downcomer water_D

$E_D=\frac{(R-1)E_R+E_F}{R}$

3) Calculating the temperature T of the water in the descending passage_DAnd density ρ_D

According to the specific enthalpy E of the water in the descending channel, through a calculation method provided by the international standard IAPWS-IF97 for the thermodynamic properties of water and water vapor (other approved approximate fitting formulas can also be used)_DAnd pressure P_SCalculating the temperature T of the water in the descending passage_DAnd density ρ_D。

4) Calculating reference water density ρ_r

By calculation according to the pressure P, using the calculation method provided by the International Standard for thermodynamic Properties of Water and steam IAPWS-IF97 (other approved approximate fitting equations may be used)_SAnd temperature T of the instrument tube_rCalculating the density rho of water in the instrument tube_r. If the instrument tube has no temperature measurement, T can be taken_r=40℃。

5) Calculating the density ρ of the steam_v

The steam in the steam generator is saturated and is calculated according to the steam pressure P by the calculation method provided by the international standard IAPWS-IF97 for the thermodynamic properties of water and steam (other approved approximate fitting equations can also be used)_SCalculating the density ρ of the steam_v。

6) Calculating the distance D from the balance container to the lower pressure tapping pipe_r

D_r=d_r+C(T_D-20)d_p

7) Calculating the actual water level of the steam generator

<math> <mrow> <mi>H</mi> <mo>=</mo> <mfrac> <mrow> <mfrac> <mi>&Delta;P</mi> <mi>g</mi> </mfrac> <mo>-</mo> <msub> <mi>D</mi> <mi>r</mi> </msub> <mrow> <mo>(</mo> <msub> <mi>&rho;</mi> <mi>V</mi> </msub> <mo>-</mo> <msub> <mi>&rho;</mi> <mi>r</mi> </msub> <mo>)</mo> </mrow> </mrow> <mrow> <msub> <mi>&rho;</mi> <mi>D</mi> </msub> <mo>-</mo> <msub> <mi>&rho;</mi> <mi>V</mi> </msub> </mrow> </mfrac> </mrow> </math>

Wherein,

d_p，D_pdistance between upper and lower pressure-tapping pipes

(d_p: at 20 ℃; d_p: under the operating condition)

d_r，D_rDistance from balancing container to lower pressure tapping pipe

(d_r: at 20 ℃; d_r: under the operating condition)

Coefficient of expansion of C steam generator

ρ_DDensity of water in downcomer

ρ_vDensity of steam

ρ_rDensity of water in instrument tube

T_DLowering the temperature of the channel water

T_rTemperature of instrument tube

Q_F,E_FFeed water mass flow and specific enthalpy

Q_R,E_RMass flow and specific enthalpy of return flow

Q_D,E_DReduced channel mass flow and specific enthalpy

Q_V,E_VSteam mass flow and specific enthalpy

R

Multiplying factor of circulation

Differential pressure value measured by differential pressure transmitter at delta P level (high pressure side (H.P) to low pressure side (L.P.))

Actual water level in H steam generator

P_SMain steam pressure

Then there are:

ΔP=[H(ρ_D-ρ_V)+D_r(ρ_V-ρ_r)]g。

Claims (4)

1. A water level measuring method of a steam generator based on a digital technology is characterized in that: it comprises the following steps:

the method comprises the following steps: obtaining basic parameters;

step two: obtaining basic measurement data;

step three: and calculating the water level.

2. The method for measuring water level of a steam generator according to claim 1, wherein the method comprises the following steps: the first step comprises the following parameters obtained by field measurement:

1) distance d between upper and lower pressure-taking tubes at 20 DEG C_p；

2) Distance d between the equalizing container and the lower pressure tapping pipe at 20 DEG C_r；

The expansion coefficient C of the steam generator is provided by a manufacturer, and the gravity acceleration g is obtained through actual measurement of a plant site of a power plant and is accurate to 2 bits after a decimal point.

3. The method for measuring water level of a steam generator according to claim 1, wherein the method comprises the following steps: the second step comprises the following steps of,

1) the water level differential pressure delta P is obtained through the water level transmitter,

2) obtaining main steam mass flow Q through main steam system measurement_VSpecific enthalpy E_VPressure P_S，

3) The water supply mass flow Q is obtained by the measurement of a main water supply system_FAnd specific enthalpy E_F，E_RIs the specific enthalpy of the return flow.

4. The method for measuring water level of a steam generator according to claim 1, wherein the method comprises the following steps: the third step comprises the following steps of,

1) calculating the circulation multiplying power R

$R=\frac{Q_F-Q_V}{Q_V}$

2) Calculating the specific enthalpy E of the downcomer water_D

$E_D=\frac{(R-1)E_R+E_F}{R}$

3) Calculating the temperature T of the water in the descending passage_DAnd density ρ_D

According to the specific enthalpy E of the water in the descending channel by a calculation method provided by the International Standard IAPWS-IF97 for the thermodynamic properties of Water and Water vapor_DAnd pressure P_SCalculating the temperature T of the water in the descending passage_DAnd density ρ_D，

4) Calculating reference water density ρ_r

Calculated according to the pressure P, by the calculation method provided by the International Standard IAPWS-IF97 for the thermodynamic Properties of Water and Water vapor_SAnd temperature T of the instrument tube_rCalculating the density rho of water in the instrument tube_rIf the instrument tube has no temperature measurement, T can be taken_r=40℃，

5) Calculating the density ρ of the steam_v

The water vapor in the steam generator is in a saturated state and is calculated according to the steam pressure P by the calculation method provided by the International Standard IAPWS-IF97 for the thermal properties of water and water vapor_SCalculating the density ρ of the steam_v，

6) Calculating the distance D from the balance container to the lower pressure tapping pipe_r

D_r=d_r+C(T_D-20)d_p

7) Calculating the actual water level of the steam generator

<math> <mrow> <mi>H</mi> <mo>=</mo> <mfrac> <mrow> <mfrac> <mi>&Delta;P</mi> <mi>g</mi> </mfrac> <mo>-</mo> <msub> <mi>D</mi> <mi>r</mi> </msub> <mrow> <mo>(</mo> <msub> <mi>&rho;</mi> <mi>V</mi> </msub> <mo>-</mo> <msub> <mi>&rho;</mi> <mi>r</mi> </msub> <mo>)</mo> </mrow> </mrow> <mrow> <msub> <mi>&rho;</mi> <mi>D</mi> </msub> <mo>-</mo> <msub> <mi>&rho;</mi> <mi>V</mi> </msub> </mrow> </mfrac> <mo>.</mo> </mrow> </math>