CN102269606A - Method for monitoring flow rate of radioactive gas exhaust flow of nuclear power plant - Google Patents

Abstract

The invention discloses a method for monitoring the flow rate of radioactive gas exhaust flow of a nuclear power plant, which comprises the following steps: utilizing a pressure gauge in an EUF (containment filtration and exhaust) system to measure the pressure value p1 before a restricted orifice, acquiring the mass flow rate of the exhaust flow before the restricted orifice from a pipeline design file of the EUF system according to the obtained pressure value p1 before the restricted orifice, and further utilizing a formula shown in the specification to calculate the volume flow rate of the radioactive gas exhaust flow, wherein in the formula, p2 is the absolute pressure of the gas at a monitoring point; T2 is the absolute temperature of the gas at the monitoring point; and RMix is the mixed gas constant of the gas exhaust flow at the monitoring point. Compared with the prior art, pressure data measured by the pressure gauge in the EUF system and pipeline design data of the EUF system are utilized to calculate the volume flow rate of the radioactive gas exhaust flow, so that no additional equipment needs to be added, and the flow rate monitoring problem of the radioactive gas exhaust flow of the nuclear power plant can be ingeniously solved.

Description

Nuclear power station radgas discharge currents flow monitoring method

Technical field

The present invention relates to nuclear power station radgas discharge currents radioactivity monitoring field, especially a kind of easy monitoring method of nuclear power station radgas discharge currents flow.

Background technology

Under major accident, as core meltdown, in order to prevent containment overvoltage breakage, nuclear power plant containment shell filters and exhaust system (being called for short EUF system or U5 system) can discharge the gases at high pressure in the containment in advance, avoiding a large amount of radiomaterials row out of control, ensure the health and safety of the public and the staff of plant area around the nuclear power plant to environment.For the radioactive level (comprising gasoloid and iodine) that reduces gaseous emission, the gas of drawing from containment is arranged to atmosphere after needing filter the EUF system again.See also EUF system flow sketch shown in Figure 1, each equipment and function description thereof are as follows among the figure:

Containment isolating valve 20: isolation containment atmosphere and ambient atmosphere are closed condition under power plant's normal operation, and major accident down can be by operator's manual unlocking when the pressure in the containment 10 reaches 5.2bar (a);

Venturi water scrubber 30: be used for filtering out the most fission products of emission gases;

Metallic filter 40: drop and micron-sized particulate that filtering venturi water scrubber 30 produces;

Restricted orifice 50: when the pressure in the containment 10 changes, make the flow velocity in venturi water scrubber 30 and the metallic filter 40 maintain a lower value, optimize filtration capacity;

Rupture disk 60 and pressure gauge 70:, need to guarantee EUF system and extraneous impermeability for preventing that radgas from passing through the EUF system equipment and pipeline leakage arrives external environment.When the EUF system did not start, equipment from containment isolating valve 20 to rupture disk 60 and pipeline were filled with nitrogen, monitored impermeability with pressure gauge 70.Under the accident conditions, EUF security of system shell isolation valve 20 is opened, and rupture disk 60 is opened after reaching pressure set-point automatically, and radgas is arranged to external environment;

Radioactivity monitoring equipment 80: for EUF system radioactivity gaseous effluent stream under the assessment major accident to the environment and the public's influence, radioactivity monitoring system in the CPR1000 factory (being called for short the KRT system) is provided with a gaseous state radioactivity monitoring equipment 80 at EUF system bleeder line end, can directly measure the volume activity concentration of I-131 and Cs-134 in the discharge currents, and total Gamma activity concentration.

But above EUF system can only monitor the activity concentration of radgas discharge currents.And be the influence of assessment gas discharge currents to the environment and the public, except needs activity concentration data, also need to know the discharging total activity, the discharging total activity can be utilized activity concentration to follow emission flow and drain time to carry out integral and calculating and obtain, and this just need monitor the discharge currents flow.

In view of this, necessaryly provide a kind of method that can carry out easy monitoring to nuclear power station radgas discharge currents flow.

Summary of the invention

The objective of the invention is to: provide a kind of easy nuclear power station radgas discharge currents flow monitoring method, to realize the calculating and the monitoring of discharging total activity.

To achieve these goals, the invention provides a kind of nuclear power station radgas discharge currents flow monitoring method, it utilizes the preceding force value p1 of manometry restricted orifice in the EUF system, according to force value p1 before the restricted orifice that obtains, obtain discharge currents mass rate before the restricted orifice from EUF systematic pipeline design document

Utilize formula again:

${\stackrel{\&CenterDot;}{V}}_2={\stackrel{\&CenterDot;}{m}}_1\frac{T_2{\mathrm{<figure-callout\; id="2"\; label="R\; Mix\; p"\; filenames="HDA0000072267430000021.png"\; state="\{\{state\}\}">R</figure-callout>}}_{\mathrm{Mix}}}{p_{}}$

Calculate the volumetric flow rate of radgas discharge currents, the p in the formula ₂Gas absolute pressure for the place, monitoring point; T ₂Gas absolute temperature for the place, monitoring point; R _MixMixed gas constant for place, monitoring point gas discharge currents.

As a kind of improvement of nuclear power station radgas discharge currents flow monitoring method of the present invention, the gas absolute pressure p at place, described monitoring point ₂Value identical with local atmospheric pressure.

As a kind of improvement of nuclear power station radgas discharge currents flow monitoring method of the present invention, the gas absolute temperature T at place, described monitoring point ₂From EUF systematic pipeline design data, obtain.

As a kind of improvement of nuclear power station radgas discharge currents flow monitoring method of the present invention, the mixed gas constant R of place, described monitoring point gas discharge currents _MixAccording to formula

$R_{\mathrm{Mix}}=\frac{1}{\mathrm{\&Sigma;}\frac{y_i}{R_i}}$

Calculate, wherein R _iBe the gas law constant of every kind of independent gas, y _iPercent by volume for every kind of gas.

As a kind of improvement of nuclear power station radgas discharge currents flow monitoring method of the present invention, the percent by volume y of every kind of gas in the described gas discharge currents _iFrom EUF systematic pipeline design data, obtain.

A kind of improvement as nuclear power station radgas discharge currents flow monitoring method of the present invention, the volumetric flow rate of described radgas discharge currents is calculated and is realized in radioactivity monitoring equipment, radioactivity monitoring equipment has the external analog signal input interface, and force value p1 is input in the radioactivity monitoring equipment by the 4-20mA signal before the restricted orifice that pressure gauge measures.

Compared with prior art, the present invention utilizes manometry is arrived in the EUF system the pressure data and the design data of EUF systematic pipeline, calculate the volumetric flow rate of radgas discharge currents, therefore need not increase extra equipment, solve the monitoring problem of nuclear power station radgas discharge currents flow dexterously.

Description of drawings

Below in conjunction with the drawings and specific embodiments, nuclear power station radgas discharge currents flow monitoring method of the present invention and useful technique effect thereof are elaborated.

Fig. 1 is the EUF system flow sketch of nuclear power station.

Fig. 2 is under the container spray state, the graph of relation of pressure and mass rate before the restricted orifice.

Fig. 3 is under the non-spray state of containment, the graph of relation of pressure and mass rate before the restricted orifice.

Embodiment

In order to find the method that nuclear power station radgas discharge currents flow is monitored, the inventor has at first studied the relation between other parameters in radgas discharge currents flow and the system, and derived the computing formula of volumetric flow rate, below at first the derivation of formula is described.

Volumetric flow rate (the m of unit of place, KRT monitoring point ³/ s) computing formula is as follows:

${\stackrel{\&CenterDot;}{V}}_2=\frac{{\stackrel{\&CenterDot;}{m}}_2}{{\mathrm{\&rho;}}_2}$ ------formula (1), wherein,

ρ ₂Be respectively the mass rate and the gas density at place, monitoring point, unit is respectively kg/s, kg/m ³

According to the principle of mass conservation,

With the gas mass flow before the restricted orifice 50

Equate that gas density can be derived according to The Ideal-Gas Equation, the following equation of characteristic conforms of place, KRT monitoring point emission gases:

p ₂V=mR _MixT ₂------formula (2);

Can release the gas density at place, monitoring point by formula (2) ${\mathrm{\&rho;}}_2=\frac{m}{V}=\frac{p_2}{T_2{R}_{\mathrm{Mix}}}$ ------formula (3);

In formula (2) and formula (3), m is the quality of place, KRT monitoring point emission gases, and unit is kg; V is the volume of place, KRT monitoring point emission gases, and unit is m ³p ₂Be place, KRT monitoring point gas absolute pressure, unit is pa; T ₂Be the gas absolute temperature at place, KRT monitoring point, unit is K; R _MixBe place, KRT monitoring point mixed gas constant, unit is J/ (kg*K).

According to formula (1), the principle of mass conservation and formula (3), can derive KRT monitoring point place volumetric flow rate and calculate formula and be: ${\stackrel{\&CenterDot;}{V}}_2={\stackrel{\&CenterDot;}{m}}_1\frac{T_2{\mathrm{<figure-callout\; id="2"\; label="R\; Mix\; p"\; filenames="HDA0000072267430000021.png"\; state="\{\{state\}\}">R</figure-callout>}}_{\mathrm{Mix}}}{p_{}}$ ------formula (4).

Below will provide the obtaining value method of each parameter in the formula (4).Need to prove, under the major accident, might start the container spray facility, containment atmosphere source item is inequality under spray and non-spray state, cause the value of each parameter in the computing formula also different, will consider respectively that below both of these case comes the volume calculated flow.

p ₂Value: p ₂Be the gas absolute pressure at place, monitoring point, because the place, monitoring point communicates with external environment, this place's gaseous tension approximates atmospheric pressure, therefore, and p ₂Value calculate according to local atmospheric pressure, unit is pa.

T ₂Value: T ₂Gas temperature for the place, monitoring point can obtain from EUF systematic pipeline design data, and unit is K.

R _MixValue: R _MixBe discharge currents mixed gas constant, unit is J/ (kg*K), and computing formula is

R wherein _iBe the gas law constant of every kind of independent gas, y _iPercent by volume for every kind of gas.

Since under container spray and non-spray state, containment Atmospheric components difference, the gas componant behind the EUF system filtration is also inequality, and table 1 is the gaseous mixture composition under the two states of listing according to EUF systematic pipeline design data, R _MixCalculating need contrast the containment state and utilize the data in the table 1 to carry out.

Table 1 discharge currents mixed gas composition

Value:

For discharging current mass flow (unit is kg/s) before KRT monitoring point/restricted orifice 50, when the containment atmospheric pressure changes in 2.6bar (a)～7.3bar (a) scope, mass rate changes with pressure, see also Fig. 2 and shown in Figure 3, can obtain force value p1 and mass rate before the restricted orifice 50 according to EUF systematic pipeline design document

Substantially linear, and p1 can directly obtain from pressure gauge 70.

Above-mentioned flow rate calculation can realize that in radioactivity monitoring equipment 80 radioactivity monitoring equipment 80 has the external analog signal input interface, and force value p1 can be input in the radioactivity monitoring equipment 80 by the 4-20mA signal before the restricted orifice that pressure gauge 70 measures.

In sum, the present invention utilizes existing pressure gauge 70 measures in the EUF system the pressure data and the design data of EUF systematic pipeline, in radioactivity monitoring equipment 80, realize the calculating of radgas discharge currents volumetric flow rate, therefore need not increase extra equipment, solve the monitoring problem of nuclear power station radgas discharge currents flow dexterously.

The announcement of book and instruction according to the above description, those skilled in the art in the invention can also carry out suitable change and modification to above-mentioned embodiment.Therefore, the embodiment that discloses and describe above the present invention is not limited to also should fall in the protection domain of claim of the present invention modifications and changes more of the present invention.In addition, although used some specific terms in this instructions, these terms do not constitute any restriction to the present invention just for convenience of description.

Claims (6)

1. nuclear power station radgas discharge currents flow monitoring method, it is characterized in that: utilize the preceding force value p1 of manometry restricted orifice in the EUF system, according to force value p1 before the restricted orifice that obtains, the discharge currents mass rate from EUF systematic pipeline design data before the acquisition restricted orifice

Utilize formula again:

${\stackrel{\&CenterDot;}{V}}_2={\stackrel{\&CenterDot;}{m}}_1\frac{T_2{R}_{\mathrm{Mix}}}{p_2}$

Calculate the volumetric flow rate of radgas discharge currents, the p in the formula ₂Gas absolute pressure for the place, monitoring point; T ₂Gas absolute temperature for the place, monitoring point; R _MixMixed gas constant for place, monitoring point gas discharge currents.

2. nuclear power station radgas discharge currents flow monitoring method according to claim 1 is characterized in that: the gas absolute pressure p at place, described monitoring point ₂Value identical with local atmospheric pressure.

3. nuclear power station radgas discharge currents flow monitoring method according to claim 1 is characterized in that: the gas absolute temperature T at place, described monitoring point ₂From EUF systematic pipeline design data, obtain.

4. nuclear power station radgas discharge currents flow monitoring method according to claim 1 is characterized in that: the mixed gas constant R of place, described monitoring point gas discharge currents _MixAccording to formula

$R_{\mathrm{Mix}}=\frac{1}{\mathrm{\&Sigma;}\frac{y_i}{R_i}}$

Calculate, wherein R _iBe the gas law constant of every kind of independent gas, y _iPercent by volume for every kind of gas.

5. nuclear power station radgas discharge currents flow monitoring method according to claim 4 is characterized in that: the percent by volume y of every kind of gas in the described gas discharge currents _iFrom EUF systematic pipeline design data, obtain.

6. according to each described nuclear power station radgas discharge currents flow monitoring method in the claim 1 to 5, it is characterized in that: the volumetric flow rate of described radgas discharge currents is calculated and is realized in radioactivity monitoring equipment, radioactivity monitoring equipment has the external analog signal input interface, and force value p1 is input in the radioactivity monitoring equipment by the 4-20mA signal before the restricted orifice that pressure gauge measures.

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