A device and method for monitoring reactor core liquid level and cavitation
Through parallel arrangement of coaxial guided radar probes and electromagnetic wave signal transceivers, the real and mixed liquid level of the reactor core is calculated, which solves the problems of inaccurate liquid level monitoring and complex structure in the prior art, and achieves rapid response and continuous Level monitoring provides accurate core level and cavitation information.
Patent Information
- Application Number
- CN201710111721.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2017-02-28
- Publication Date
- 2024-12-17
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
The differential pressure and temperature difference methods used in existing reactors for monitoring liquid levels have high measurement inaccuracy, complex structure, and the need for opening holes may lead to coolant leakage, long response time and can only monitor a single liquid level and cannot be used in the core. Issues of effective working when the two phases of vapor and liquid flow.
Two coaxial guided radar probes arranged in parallel are combined with electromagnetic wave signal transceivers to calculate the core liquid level through the time difference of electromagnetic wave signals. One probe is used to monitor the real liquid level and the other probe is used to monitor the mixed liquid level. The vacuole share enables the acquisition of continuous liquid level and vacuole information without opening holes at the bottom of the pressure vessel.
It realizes rapid and accurate acquisition of core continuous liquid level and cavitation information under reactor start and stop and accident conditions, provides timely operator information, and does not require on-site debugging and verification. It has a simple and reliable structure, which avoids the risk of coolant leakage.
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Figure CN108511094B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a technology for monitoring liquid level and cavitation, and more particularly to an apparatus and method for monitoring liquid level and cavitation in a reactor core. Background Art
[0002] The Three Mile Island accident in the United States showed that under conditions where an accident was caused by reactor water loss, the simple pressurizer water level was difficult to characterize the loop water charge and the liquid level status in the pressure vessel. It was necessary to directly obtain the core liquid level information to assist the operator in determining the core water loss situation and accurately select the accident handling procedures.
[0003] In existing reactor types, instrument systems for pressure vessel liquid level monitoring are generally equipped, and a variety of methods for measuring the liquid level in pressure vessels have been proposed, among which the differential pressure method [1] and the temperature difference method [2] are the two most common methods. The differential pressure method calculates the liquid level by measuring the pressure difference between the bottom and top of the pressure vessel. The differential pressure liquid level measurement system requires at least three pressure transmitters and multiple pressure supply pipelines, and the system structure is quite complex. In the actual application of liquid level calculation, it is necessary to repeatedly check and debug the system before it is put into use to obtain calibration parameters, and it is also necessary to accurately obtain other external parameter information, such as the pressure and temperature of the reactor building. In short, differential pressure liquid level measurement is affected by many factors, including the operating status of the main pump, the temperature of the coolant in the reactor, and the environmental conditions in the containment, and the measurement inaccuracy is relatively large. In addition, the differential pressure method requires opening a hole at the bottom of the pressure vessel to take pressure, which may cause the core coolant to leak, which is obviously not in line with the design concept and requirements of advanced reactors. The temperature difference method is to distinguish the vapor (gas) / liquid phase and then monitor the liquid level at key points based on the difference in heat exchange capacity of metal bodies in the vapor (gas) phase and the liquid phase. The heat transfer (heating) in the temperature difference liquid level measurement method requires a certain amount of time, that is, the response time to the liquid level change is long, and the key component electric heater has the disadvantage of shortening its service life under high pressure and strong radiation environment. In addition, the temperature difference liquid level detector only monitors a single liquid level point and cannot monitor continuous liquid levels. In addition, under accident conditions where the core is in a vapor-liquid two-phase flow, the detector may lose its function. Summary of the invention
[0004] In view of the deficiencies in the prior art, the present invention provides a device and method for monitoring the core liquid level and cavitation. The device and method do not require opening a hole at the bottom of the reactor pressure vessel, have a simple structure, reliable performance, and do not require on-site debugging and verification. They can simultaneously obtain continuous core liquid level and cavitation information under reactor start-up and shutdown conditions and accident conditions, and can also quickly respond to changes in the core liquid level to provide timely and accurate information to the operator.
[0005] According to one aspect of the present invention, a device for monitoring the liquid level and cavitation of a reactor core comprises at least: an electromagnetic wave signal transceiver; two coaxial guided wave radar probes arranged in parallel, whose tops are connected to the electromagnetic wave signal transceiver to share the electromagnetic wave signal transceiver, and the coaxial guided wave radar probes comprise a waveguide rod and a coaxial sleeve, wherein one of the coaxial guided wave radar probes has only a bottom opening to monitor the actual liquid level of the core, and the coaxial sleeve wall of the other coaxial guided wave radar probe has a hole to monitor the mixed liquid level of the core.
[0006] According to another aspect of the present invention, a method for monitoring the liquid level and cavitation of a reactor core comprises at least: connecting two coaxial guided wave radar probes in parallel to an electromagnetic wave signal transceiver, wherein the coaxial guided wave radar probes comprise a waveguide rod and a coaxial sleeve; and monitoring the actual liquid level H of the core by a first coaxial guided wave radar probe of the two coaxial guided wave radar probes. l The first coaxial guided wave radar probe has only a bottom opening so that the coolant in the coaxial sleeve is in liquid phase; the other second coaxial guided wave radar probe among the two coaxial guided wave radar probes monitors the mixed liquid level H of the core. m The wall of the coaxial sleeve of the second coaxial guided wave radar probe is opened so that the coolant fluid inside and outside the coaxial sleeve is connected; the real liquid level H of the core l and mixed liquid level H m Get the core cavitation fraction . BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Figure 1 It is a structural schematic diagram of a device for monitoring the liquid level and cavitation of a reactor core according to the present invention; wherein: 1-signal transmitter, 2-electromagnetic wave signal transceiver, 3-mounting bracket, 4-fixing bracket, 5-first coaxial guided wave radar probe, 6-second coaxial guided wave radar probe, 7-coaxial sleeve, 8-waveguide rod, 9-opening. DETAILED DESCRIPTION
[0008] The present invention is described in detail below with reference to the accompanying drawings. As an example but not a limitation, Figure 1The device for monitoring the liquid level and cavitation of the reactor core shown in the figure includes two coaxial guided wave radar probes 5, 6, which are preferably of equal length and arranged in parallel. The coaxial guided wave radar probes 5, 6 include a waveguide rod 8 and a coaxial sleeve 7 coaxial with the waveguide rod 8. The waveguide rod 8 and the coaxial sleeve 7 of the coaxial guided wave radar probes 5, 6 form an electromagnetic wave transmission structure similar to a coaxial transmission line. The tops of the two coaxial guided wave radar probes 5, 6 are connected to an electromagnetic wave signal transceiver 2, which can transmit and receive electromagnetic wave signals. The top of the electromagnetic wave signal transceiver 2 is connected to a signal transmitter 1, and the signal transmitter 1 and the electromagnetic wave signal transceiver 2 can be designed in an integrated manner and arranged on the outside of the upper head of the pressure vessel. The two coaxial guided wave radar probes 5, 6 can share the electromagnetic wave signal transceiver and the signal transmitter. The core liquid level information is monitored according to the following principle: when the electromagnetic wave emitted by the electromagnetic wave signal transceiver 2 is transmitted in the coaxial guided wave radar probes 5, 6 to reach the coolant liquid surface, a part of the electromagnetic wave will be reflected by the coolant liquid surface and transmitted back to the signal transceiver 2 and received by the signal transceiver 2. The signal transmitter 1 obtains the core liquid level information based on the time difference between the electromagnetic wave emitted and received by the electromagnetic wave signal transceiver 2.
[0009] Figure 1 The two coaxial guided wave radar probes 5 and 6 arranged in parallel have slightly different structures. The wall of the coaxial sleeve 7 of the first coaxial guided wave radar probe 5 has no flow holes, and the coolant can only enter from the bottom opening, so that the coolant in the tube is a pure liquid phase (the liquid level is the real liquid level); while the wall of the coaxial sleeve 7 of the second coaxial guided wave radar probe 6 has a continuous opening 9 in the axial direction, and the opening 9 is used for fluid communication inside and outside the tube, so that the state of the coolant in the tube is the same as the state of the core. The opening 9 is preferably a longitudinal narrow slit, so as to stabilize the flow field in the coaxial sleeve 7 while ensuring the coolant fluid communication inside and outside the coaxial sleeve 7, and prevent the inaccurate liquid level monitoring caused by the fluctuation of the peripheral core liquid level.
[0010] like Figure 1As shown in , two coaxial guided wave radar probes 5, 6 are fixed and positioned axially through multiple fixed brackets 4, and the top of the probe is fixed to the upper head of the pressure vessel through the mounting bracket 3 to meet the seismic requirements. The bottom of the coaxial guided wave radar probe 5, 6 is located below the bottom of the core, meeting the requirements of the continuous liquid level measurement range from the liquid level at the bottom of the core to the full liquid level in the pressure vessel. The main material of the probe is ZIRLO alloy (zirconium-niobium alloy, AP1000 fuel cladding material), or other materials that meet the requirements of corrosion resistance, radiation resistance and long-term operation in high temperature and high pressure environment. Alternatively, if the probe function can be realized and it can work for a long time in the core environment, other materials can be selected to make the probe. Alternatively, if the continuous liquid level measurement range and accuracy requirements can be met, the rod-type probe can be replaced by a cable-type probe or the guided wave sensor can be replaced by a thermal resistor liquid level sensor, etc.
[0011] In the event of an accident, the coolant in the core and the upper area may be in a two-phase fluid state (i.e., a steam (gas)-liquid mixed state). The two-phase fluid may enter the second coaxial guided wave radar probe 6 through the opening 9 on the tube wall of the coaxial sleeve 7 of the second coaxial guided wave radar probe 6, so that the state of the coolant in the tube remains the same as the state of the core. Therefore, the liquid level information of the core monitored by the second coaxial guided wave radar probe 6 should be the mixed liquid level information of the two-phase fluid. However, because the tube wall of the coaxial sleeve 7 of the first coaxial guided wave radar probe 5 is not provided with a flow hole, the liquid level information of the monitored core should be the real liquid level information of the pure liquid phase state. In the event of an accident, if it is assumed that the real liquid level of the core monitored by the first coaxial guided wave radar probe 5 is H l The mixed liquid level in the core monitored by the second coaxial guided wave radar probe 6 is H m , the size of the core cavitation fraction can be calculated This cavitation fraction value represents the total cavitation information of the core and has nothing to do with the local cavitation fraction, core temperature and uneven flow velocity distribution. When there is no two-phase flow in the core, the liquid level monitoring values of the two probes are the same, and the cavitation fraction value is 0.
[0012] The specific implementation process of cavitation information acquisition is as follows: the signal transmitter 1 obtains the core liquid level information according to the time difference between the electromagnetic wave signal transceiver 2 transmitting and receiving the electromagnetic wave. The data processing module of the signal transmitter 1 determines whether the core is in a two-phase flow state and calculates the cavitation fraction value by comparing the core liquid level information monitored by the first coaxial guided wave radar probe 5 and the second coaxial guided wave radar probe 6. When the liquid level values monitored by the two probes are equal, it is considered to be in a single-phase flow state, and the cavitation fraction value is 0; when the liquid level value monitored by the first coaxial guided wave radar probe 5 is less than the liquid level value monitored by the second coaxial guided wave radar probe 6 (that is, the actual liquid level of the core is less than the mixed liquid level), it is determined that the core is in a two-phase flow state. The cavitation fraction value is obtained according to the cavitation fraction calculation formula and combined with the liquid level values monitored by the first and second coaxial guided wave radar probes, and the 4-20mA liquid level and cavitation simulation signals are processed and generated. At the same time, the signal transmitter 1 generates an alarm signal for a key measuring point based on the key liquid point value preset by the user and combined with the real-time liquid level information. According to actual needs, multiple groups of key liquid level measuring points can be freely set, such as the top of the hot pipe section, the bottom of the hot pipe section, the top of the core and the bottom of the core, so as to realize the alarm of multiple key liquid level monitoring points.
[0013] The device and method for monitoring the core liquid level and cavitation proposed in this paper can work simply and reliably, without opening a hole at the bottom of the reactor pressure vessel, without on-site commissioning and verification, and can simultaneously obtain the core continuous liquid level and cavitation information under reactor startup and shutdown conditions and accident conditions and quickly respond to changes in the core liquid level. The signal transmitter also provides alarm signals for key measuring points, further strengthening the monitoring of the accident process under accident conditions and providing timely and accurate information to operators.
[0014] Although the present disclosure has described certain embodiments and generally associated methods, variations and substitutions of these embodiments and methods will be apparent to those skilled in the art. Therefore, the above description of exemplary embodiments does not limit or constrain the present disclosure. Other variations, substitutions, and changes are also possible without departing from the spirit and scope of the present disclosure as defined by the following claims.
[0015] References
[0016] [1] Wang Xin, Kong Fanrun. Principle of core water level measurement in pressurized water reactor nuclear power plant[J]. Science and Technology Horizon, 2013(34):373-373.
[0017] [2] He Zhengxi, Li Fulin, Gou Tuo, et al. Research on temperature difference pressure vessel liquid level detection technology [C] / / China Nuclear Power Research Institute Science and Technology Annual Report. 2011.
Claims
1. A device for monitoring reactor core liquid level and cavitation, comprising at least: Electromagnetic wave signal transceiver; Two coaxial guided wave radar probes are arranged in parallel, and the tops of the two coaxial guided wave radar probes are connected to the electromagnetic wave signal transceiver, so as to share the electromagnetic wave signal transceiver. The coaxial guided wave radar probes include a waveguide rod and a coaxial sleeve, and are characterized in that: One coaxial guided wave radar probe has only a bottom opening to monitor the actual liquid level in the core, and the other coaxial guided wave radar probe has a hole in the coaxial casing wall to monitor the mixed liquid level in the core. Wherein, the radar probe is a rod-type probe or a cable-type probe.
2. The device according to claim 1, characterized in that: It also includes a signal transmitter used in conjunction with the electromagnetic wave signal transceiver to generate a liquid level simulation signal, and / or a cavitation simulation signal, and / or an alarm signal of a key liquid level monitoring point.
3. The device according to claim 2, characterized in that: The electromagnetic wave signal transceiver and the signal transmitter are designed in an integrated manner and are arranged outside the upper head of the pressure vessel.
4. The device according to claim 1, characterized in that: The two coaxial guided wave radar probes are a first coaxial guided wave radar probe and a second coaxial guided wave radar probe of equal length, wherein the first coaxial guided wave radar probe has only a bottom opening to monitor the actual liquid level of the core, and the wall of the coaxial sleeve of the second coaxial guided wave radar probe is provided with openings that are continuous in the axial direction to continuously monitor the mixed liquid level of the core.
5. The device according to claim 4, characterized in that: The continuous openings are longitudinal narrow slits, thereby ensuring the coolant fluid communication inside and outside the coaxial sleeve and stabilizing the flow field inside the tube to prevent the influence of peripheral core liquid level fluctuations.
6. The device according to claim 1, characterized in that: The two coaxial guided wave radar probes are fixed and positioned along the axial direction by a plurality of fixing brackets, and the top ends of the probes are fixed to the upper head of the pressure vessel by mounting brackets, thereby meeting the seismic requirements.
7. The device according to claim 1, characterized in that: The bottom of the coaxial guided wave radar probe is below the bottom of the core, thereby satisfying continuous liquid level monitoring from the liquid level at the bottom of the core to the full liquid level in the pressure vessel.
8. The device according to claim 2, characterized in that: Set multiple groups of key liquid level monitoring points to achieve alarms for multiple key liquid level monitoring points.
9. The device according to claim 1, characterized in that: The main material of the coaxial guided wave radar probe is ZIRLO alloy, or other materials that are corrosion-resistant, radiation-resistant and can work for a long time in a high temperature and high pressure environment.
10. The device according to claim 1, characterized in that: In the case of two-phase flow in the core, if the actual liquid level of the core monitored by the first coaxial guided wave radar probe is H l , and the mixed liquid level in the core monitored by the second coaxial guided wave radar probe is H m , then the void fraction of the core is 11. A method for monitoring reactor core liquid level and cavitation, comprising at least: Connecting two coaxial guided wave radar probes in parallel to an electromagnetic wave signal transceiver, wherein the coaxial guided wave radar probes include a waveguide rod and a coaxial sleeve; The real liquid level H of the core is monitored by the first coaxial guided wave radar probe of the two coaxial guided wave radar probes. l , the first coaxial guided wave radar probe has only a bottom opening so that the coolant in the coaxial sleeve is in liquid phase; The mixed liquid level H of the core is monitored by the other second coaxial guided wave radar probe of the two coaxial guided wave radar probes. m , a hole is opened in the wall of the coaxial sleeve of the second coaxial guided wave radar probe so that the coolant fluid inside and outside the coaxial sleeve is connected; The actual liquid level H in the core l and mixed liquid level H m Get the core cavitation fraction 12. The method according to claim 11, characterized in that: It also includes a signal transmitter used in conjunction with the electromagnetic wave signal transceiver to generate a liquid level simulation signal, and / or a cavitation simulation signal, and / or an alarm signal of a key liquid level monitoring point.
13. The method according to claim 11, characterized in that: The two coaxial guided wave radar probes are a first coaxial guided wave radar probe and a second coaxial guided wave radar probe of equal length, wherein the first coaxial guided wave radar probe has only a bottom opening to monitor the actual liquid level of the core, and the wall of the coaxial sleeve of the second coaxial guided wave radar probe is provided with openings that are continuous in the axial direction to continuously monitor the mixed liquid level of the core.
14. The method according to claim 13, characterized in that: The continuous openings are longitudinal narrow slits, thereby ensuring the coolant fluid communication inside and outside the coaxial sleeve and stabilizing the flow field inside the tube to prevent the influence of peripheral core liquid level fluctuations.
15. The method according to claim 11, characterized in that: The two coaxial guided wave radar probes are fixed and positioned along the axial direction through a plurality of fixing brackets, and the top ends of the probes are fixed to the upper head of the pressure vessel through mounting brackets, thereby meeting the seismic resistance requirements.
16. The method according to claim 11, characterized in that: The bottom of the coaxial guided wave radar probe is below the bottom of the core, thereby satisfying continuous liquid level monitoring from the liquid level at the bottom of the core to the full liquid level in the pressure vessel.
17. The method according to claim 12, characterized in that: Set multiple groups of key liquid level monitoring points to achieve alarms for multiple key liquid level monitoring points.