JP2018091806A - Vent flow rate measurement system of reactor containment vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a flow rate without increasing a pressure loss in a piping system and to estimate an emitted radiation while venting a reactor containment vessel.SOLUTION: In order to solve the problem, a vent flow rate measurement system of a reactor containment vessel according to the present invention includes: a vent tube pressure gauge connected to the midpoint of a vent tube connected to the reactor containment vessel and measuring a pressure inside the vent tube; a pressure suppression room pressure gauge for measuring the pressure of a pressure suppression room of the reactor containment vessel; a pressure-mass flow rate converter for converting the pressure into a mass flow rate corresponding to the pressure inside the pressure suppression room measured by a pressure suppression room pressure gauge based on an already integrated pressure-mass flow rate graph; and a computing unit for outputting the mass flow rate obtained based on vapor density and the mass flow rate from the pressure-mass flow rate converter.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a vent flow measurement system for a containment vessel, and more particularly to a vent flow measurement system for a containment vessel suitable for measuring a vent flow rate in order to estimate a released radioactivity during venting of the containment vessel.

  The main purpose of the reactor containment vent flow measurement system installed in the reactor plant is when the pressure in the reactor containment rises above the design pressure in the event of a major accident such as the loss of all AC power, In order to prevent damage to the reactor containment vessel, the internal pressure is released, the reactor containment vessel is depressurized, and the reactor coolant discharged and accumulated in the reactor containment vessel at the time of the serious accident is used as steam. It is to discharge outside the reactor containment vessel and remove the core decay heat after the reactor shutdown.

  In order to monitor the functions of the vent system itself in the event of a serious accident as described above, the vent flow measurement system of the containment vessel has a pressure in the vent pipe on the vent pipe connected to the containment vessel. A pressure gauge for measurement is installed, and the pressure inside the vent pipe is monitored by this pressure gauge, so that it can be confirmed whether or not the reactor containment vessel has been depressurized reliably.

  Importantly, the reactor containment vent flow measurement system may be used in the event of a serious accident involving core damage. That is, when the reactor core is damaged, steam containing radioactive material is released outside the reactor containment vessel through the vent flow measurement system of the reactor containment vessel. Therefore, in order to estimate the released radioactivity at the containment vessel vent, It is necessary to measure the measured radioactivity and vent flow rate, and the vent flow measurement system of the containment vessel is used.

  Normally, the reactor containment vent system is not equipped with equipment that dynamically adjusts the flow rate, so the steam flowing through the containment vent system has a flow rate equivalent to the core collapse heat after the reactor shutdown. It becomes. Therefore, the physical properties of the steam change with the depressurization of the reactor containment vessel, and the steam flow rate changes as the core decay heat attenuates with time.

  A differential pressure type flow meter is usually used for measuring the flow rate of a fluid whose physical property value changes in this way. Since the differential pressure type flow meter uses an orifice plate or a flow nozzle as a flow meter element, a pressure loss occurs when it is incorporated in a piping system.

  Here, the basic structure and operation principle of the differential pressure type flow rate measurement system in the piping system will be described with reference to FIG.

  In FIG. 1, a pipe 2 is provided with a flow meter orifice 3 and pressure guiding pipes 5 a and 5 b. The pressure guiding pipes 5 a and 5 b are installed on the upstream side and downstream side of the flow meter orifice 3 with respect to the fluid flow 1 in the pipe 2 via the main valve 4 and the three-way valve 6, and upstream of the flow meter orifice 3. The pressure on the side and the downstream side is transmitted to the differential pressure transmitter 7. The output from the differential pressure transmitter 7 is input to the square root calculator 8, and the square root calculator 8 uses the fluid density based on the differential pressure data and the opening area of the flow meter orifice 3 to calculate the flow rate signal 9. Converted.

  What is important here is that in the differential pressure type flow rate measurement system in the above-described piping system, the flowmeter orifice 3 becomes a fluid resistance in the piping system, so that the pressure loss of the piping system increases by installing the flowmeter orifice 3. That is.

  Moreover, regarding the differential pressure type flow meter in the piping system, for example, there is one described in Patent Document 1.

  This Patent Document 1 discloses a differential pressure type flow meter that detects pressures in pressure detection devices installed at two locations in the flow direction of a pipe for measuring a flow rate and obtains a flow rate from the differential pressure between them, that is, an orifice, a nozzle, a venturi. In order to obtain a differential pressure type flow meter that can measure the pressure difference (differential pressure) generated before and after the throttle part by inserting a throttle part such as a pipe and can measure the flow rate with high accuracy from the measured differential pressure, Pressure detecting means such as strain gauges and piezo elements are connected to each of the pressure detecting devices, and a conduction path for equalizing the pressure of the fluid applied to each pressure detecting means is provided, and each of the pressure detecting devices is based on the equalized pressure. A configuration is described in which a measurement control device for adjusting a detection value from the pressure detection means is provided.

JP 2000-283810 A

  By the way, the vent flow measurement system of the containment vessel needs to be a system that can discharge more than the flow rate necessary for depressurization of the containment vessel and heat removal from the core decay heat. The upper limit of loss is fixed.

  Therefore, when a flow meter orifice as described above or a throttle part such as an orifice, nozzle, or venturi tube as described in Patent Document 1 is incorporated in the vent flow measurement system of the reactor containment vessel, the flow meter orifice or the throttle part is a fluid. As a result, the flow rate of the piping system decreases, and eventually the installation of a flow meter orifice or a throttle that can become a fluid resistance reduces the performance of the reactor containment vent system.

  The present invention has been made in view of the above-described points, and an object of the present invention is to be able to measure the flow rate without increasing the pressure loss in the piping system and to estimate the released radioactivity at the time of venting the containment vessel. To provide a vent flow measurement system for a containment vessel.

  In order to achieve the above object, the reactor containment vessel vent flow rate measurement system of the present invention houses a reactor pressure vessel containing a core and measures the vent flow rate of a reactor containment vessel equipped with a pressure suppression chamber. A vent pipe pressure gauge that is connected in the middle of the vent pipe connected to the reactor containment vessel and measures the pressure in the vent pipe, and the pressure containment chamber in the reactor containment vessel Pressure-mass to be converted into a mass flow corresponding to the pressure in the pressure suppression chamber measured by the pressure suppression chamber pressure gauge based on a pressure-mass flow rate graph built in advance and a pressure-mass flow graph incorporated in advance The steam is converted into a steam density corresponding to the pressure in the vent pipe measured by the vent pipe pressure gauge based on a flow rate converter and a saturated steam table incorporated in advance, and the steam Characterized in that it comprises a mass flow transducer outputs the volumetric flow rate obtained based on the mass flow rate from the calculator - degrees and the pressure.

  According to the present invention, the flow rate can be measured without increasing the pressure loss in the piping system, and the released radioactivity at the time of venting the containment vessel can be estimated.

It is a figure for demonstrating the basic composition and operating principle of the conventional differential pressure type flow measurement system. It is a schematic block diagram which shows Example 1 of the vent flow volume measuring system of the reactor containment vessel of this invention. It is a schematic block diagram which shows Example 2 of the vent flow volume measuring system of the reactor containment vessel of this invention.

  Hereinafter, the vent flow rate measuring system for a reactor containment vessel according to the present invention will be described based on the illustrated embodiment. In addition, in each Example, the same code | symbol is used for the same component.

  FIG. 2 shows a first embodiment of a vent flow measurement system for a reactor containment vessel according to the present invention.

  As shown in the figure, the reactor containment vessel vent flow rate measurement system of the present embodiment accommodates a reactor pressure vessel 11 containing a core (not shown) and a reactor equipped with a pressure suppression chamber 13. A vent pipe 14 is connected to the containment vessel 12, and a vent is installed in the second pipe system 10 b connected to the middle of the vent pipe 14 and downstream of the vent valve 15 to measure the pressure in the vent pipe 14. A piping pressure gauge 17, a pressure suppression chamber pressure gauge 16 for measuring the pressure in the pressure suppression chamber 13 of the reactor containment vessel 12, and a pressure-mass flow graph 19 installed in advance in the first piping system 10 a. Pressure-mass flow rate converter 18 for converting to a mass flow rate corresponding to the pressure in the pressure suppression chamber 13 measured by the pressure suppression chamber pressure gauge 16, and vent piping based on a saturated steam table incorporated in advance. While converting into the vapor density corresponding to the pressure in the vent pipe 14 measured with the force meter 17, the signal 21 of the volume flow rate obtained based on the vapor density and the mass flow rate from the pressure-mass flow rate converter 18 is output. And a computing unit 20 that is schematically configured.

  That is, the pressure data of the vent pipe 14 from the vent pipe pressure gauge 17 installed on the vent pipe 14 is input to the calculator 20, and the pressure data of the vent pipe 14 is a saturated steam table incorporated in the calculator 20. Is converted into a vapor density corresponding to the pressure.

  The pressure data from the pressure suppression chamber pressure gauge 16 installed in the pressure suppression chamber 13 in the reactor containment vessel 12 is input to the pressure-mass flow rate converter 18, and the pressure-mass flow rate graph 19 incorporated in advance. Thus, the mass flow rate corresponding to the pressure in the pressure suppression chamber 13 is converted. The converted mass flow data is input to the computing unit 20, converted into a volume flow by the vapor density converted from the mass flow data and the pressure data in the vent pipe 14, and output as a volume flow signal 21.

  By adopting such a configuration of the present embodiment, no facility for fluid resistance such as a flow meter orifice is installed in the piping system, so that the reactor containment vessel is not increased without increasing the pressure loss of the piping system. The flow measurement of the vent flow measurement system is possible.

  Therefore, it is possible to estimate the released radioactivity at the time of venting of the containment vessel from the flow rate data measured by the vent flow measurement system of the containment vessel of this embodiment, and other elements in the piping system accompanying the flow meter installation. Therefore, the amount of equipment is not increased.

  Therefore, according to the present embodiment, the flow rate can be measured without increasing the pressure loss in the piping system, and the released radioactivity at the time of venting the containment vessel can be estimated.

  FIG. 3 shows a second embodiment of a vent flow measurement system for a reactor containment vessel according to the present invention.

  The present embodiment shown in the figure has substantially the same configuration as that of the first embodiment shown in FIG. 2, but the upstream side from the connection portion to which the second piping system 10b where the vent piping pressure gauge 17 is installed is connected. That is, a vent filter 22 that removes radioactive substances from the reactor containment vessel 12 is connected to the vent pipe 14 between the connection portion (the vent pipe pressure gauge 17) to which the second pipe system 10b is connected and the vent valve 15. It is different from the first embodiment in that it is installed.

  Even in this configuration of the present embodiment, the same effect as in the first embodiment can be obtained, and the vent pipe pressure gauge 17 is installed on the downstream side of the vent filter 22, so Using the signal 21, it is possible to quantitatively evaluate the effect of the vent filter 22 (how much radioactive material has been removed by the vent filter 22).

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  DESCRIPTION OF SYMBOLS 1 ... Fluid flow in piping, 2 ... Piping, 3 ... Flowmeter orifice, 4 ... Main valve, 5a, 5b ... Pressure guiding pipe, 6 ... Sanki valve, 7 ... Differential pressure transmitter, 8 ... Square root computing unit, 9 ... Flow signal, 10a ... First piping system, 10b ... Second piping system, 11 ... Reactor pressure vessel, 12 ... Reactor containment vessel, 13 ... Pressure suppression chamber, 14 ... Vent piping, 15 ... Vent valve, DESCRIPTION OF SYMBOLS 16 ... Pressure suppression chamber pressure gauge, 17 ... Vent piping pressure gauge, 18 ... Pressure-mass flow rate converter, 19 ... Pressure-mass flow rate graph, 20 ... Calculator, 21 ... Volume flow signal, 22 ... Vent filter.

Claims (3)

A system for storing a reactor pressure vessel containing a reactor core and measuring a vent flow rate of a reactor containment vessel having a pressure suppression chamber,
A vent pipe pressure gauge that is connected in the middle of the vent pipe connected to the reactor containment vessel and measures the pressure in the vent pipe, and a pressure suppression that measures the pressure in the pressure suppression chamber of the reactor containment vessel A chamber pressure gauge, a pressure-mass flow converter for converting into a mass flow rate corresponding to the pressure in the pressure suppression chamber measured by the pressure suppression chamber pressure gauge based on a pressure-mass flow graph incorporated in advance, The vapor density is converted into a vapor density corresponding to the pressure in the vent pipe measured by the vent pipe pressure gauge based on the incorporated saturated vapor table, and the vapor density and the mass flow rate from the pressure-mass flow rate converter are converted into the vapor density. A reactor containment vessel vent flow rate measuring system, comprising: an arithmetic unit that outputs a volume flow rate obtained based on the reactor. In the reactor containment vessel vent flow measurement system according to claim 1,
A vent flow measurement system for a reactor containment vessel, wherein a vent valve is installed in the middle of the vent pipe, and the vent pipe pressure gauge is connected to the vent pipe downstream of the vent valve. In the vent flow measurement system of the containment vessel according to claim 2,
A vent for a reactor containment vessel, wherein a filter for removing radioactive material from the reactor containment vessel is installed in the vent pipe upstream of a connection portion to which the vent pipe pressure gauge is connected. Flow measurement system.

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