JP2014041023A - Reactor water-level meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reactor water-level meter capable of measuring a water level without being influenced by variations in a reference water level in a reference level device.SOLUTION: A liquid level forming pipe portion 4 of a measurement pipe LP is connected to a gas phase part in a reactor pressure vessel (RPV) 1 and a liquid layer part at a bottom face of the RPV 1, and the liquid level forming pipe portion 4 is constituted so as to form a liquid level therein. By using an optical fiber temperature sensor 5, a temperature difference arising between the gas phase part and the liquid layer part in the liquid level forming pipe portion 4, and a height position at which the temperature difference is generated are detected. Then, on the basis of the detected height position, a water level of cooling water in the liquid level forming pipe portion 4 (that is, a water level of cooling water in the RPV 1) is calculated.

Description

  The present invention relates to an apparatus for measuring the water level of a nuclear reactor.

  Reactor pressure vessel water level in boiling water reactors is an important monitoring in the reactor monitoring system that plays a role in maintaining and monitoring the reactor water level within an appropriate operating range against changes in operating conditions that may occur during normal operation. It is a parameter. The water level in the reactor pressure vessel is measured by the pressure difference between the gas phase portion and the liquid phase portion. In particular, when the gas phase portion is steam, a reference surface unit is provided for condensing the steam guided from the reactor pressure vessel to form a reference water level. Then, the water level in the reactor pressure vessel is measured by continuously measuring the differential pressure between the head water pressure at the reference water level and the water head pressure at the reactor water level that conveys the pressure on the fluctuating reactor water level side using a differential pressure detector. (See Patent Document 1).

JP 59-178320 A

  In the water level measurement of the reactor pressure vessel of the boiling water reactor described above, it is necessary to form a reference water level with a reference surface device. However, there is a possibility that the accurate water level cannot be measured because the reference water level fluctuates.

  A reactor water level gauge according to the present invention includes an upper piping connected to a gas phase portion in a reactor pressure vessel, a lower piping connected to a liquid layer at the bottom of the reactor pressure vessel, an upper piping, Light having a liquid level forming pipe part that connects between the lower pipe parts to form a liquid level inside, and an optical fiber that is arranged from the upper part to the lower part of the liquid level forming pipe part inside the liquid level forming pipe part A fiber temperature sensor, a light source of pulsed light incident on the optical fiber, a temperature detection unit that detects scattered light generated in the optical fiber, and detects a temperature at an arbitrary position of the optical fiber based on the detected scattered light; The liquid level position that calculates the position where the temperature difference between the gas phase part and the liquid layer part in the liquid level forming pipe part occurs as the liquid level position based on the temperature at the arbitrary position of the optical fiber detected by the temperature detection part Liquid level calculated by the calculation unit and the liquid level position calculation unit Based on the position, characterized in that it comprises a water level information output section for converting the level information of the cooling water in the reactor pressure vessel.

  According to the present invention, the water level can be measured without being affected by the fluctuation of the reference water level in the reference surface device.

Schematic diagram showing a first embodiment of a reactor water level gauge according to the present invention Diagram showing temperature measurement principle using optical fiber temperature sensor The schematic diagram which shows 2nd Embodiment of the reactor water level meter which concerns on this invention The schematic diagram which shows 3rd Embodiment of the reactor water level meter which concerns on this invention The schematic diagram which shows 4th Embodiment of the reactor water level meter which concerns on this invention

--- First embodiment ---
A first embodiment of a reactor water level meter according to the present invention will be described with reference to FIGS. In the present embodiment, an example in which the reactor water level meter according to the present invention is applied to a boiling water reactor (BWR) will be described. FIG. 1 is a schematic diagram relating to water level measurement of a reactor pressure vessel (RPV) using the reactor water level meter of the present embodiment. In addition, in FIG. 1, the structure regarding the water level measurement of a reactor pressure vessel is mainly described among each structure of a boiling water reactor, and the description about the other structure is abbreviate | omitted. In the boiling water reactor according to the present embodiment, a reactor pressure vessel 1 is stored inside a reactor containment vessel 10.

  A reactor core shroud (not shown) is installed inside the reactor pressure vessel 1. In the following description, the reactor pressure vessel is referred to as RPV. A core (not shown) loaded with a plurality of fuel assemblies is disposed in the core shroud. A steam / water separator and a steam dryer (not shown) are disposed in the RPV 1 above the core. A predetermined amount of cooling water is present in the RPV 1. The cooling water in the RPV 1 is supplied to the core from below the core (not shown) by a jet pump or the like.

  The cooling water is heated when passing through the core and becomes a gas-liquid two-phase flow containing water and steam. A gas-water separator (not shown) separates the gas-liquid two-phase flow into steam and water. The separated steam is further dehumidified by a steam dryer (not shown) and used as a drive source for a steam turbine (not shown). The steam discharged from the steam turbine is condensed into water by a condenser (not shown). This condensed water is supplied again into the RPV 1 as feed water. The water separated by the steam separator and the steam dryer falls in the RPV 1 and becomes cooling water.

  The reactor water level meter 100 according to the present embodiment includes a measurement pipe LP, an optical fiber temperature sensor 5, and a processing device 9. The measurement pipe LP has a liquid level forming pipe part 4, an upper pipe part 2, and a lower pipe part 3. The liquid level forming pipe portion 4 is a pipe provided in the reactor containment vessel 10 and extending in the vertical direction. The upper piping part 2 is a pipe that connects the upper part of the liquid level forming piping part 4 and the gas phase part of the RPV 1. The lower piping part 3 is a pipe that connects the lower part of the liquid surface forming piping part 4 and the liquid layer part of the RPV 1. In addition, the lower piping part 3 is connected to the bottom face of RPV1, as shown in FIG.

  In the measurement pipe LP configured as described above, a part of the cooling water in the RPV 1 flows and a liquid level (boundary between the gas phase part and the liquid layer part) is formed inside the liquid level forming pipe part 4. . The height position of the liquid level of the liquid level forming pipe part 4, that is, the water level of the cooling water inside the liquid level forming pipe part 4 is linked with the water level in the RPV 1. Therefore, the water level in the RPV 1 can be estimated (that is, the water level in the RPV 1 can be measured) by measuring the water level of the cooling water in the liquid level forming pipe part 4. Therefore, in the reactor water level meter 100 of the present embodiment, the temperature difference generated between the gas phase part and the liquid layer part in the liquid level forming pipe part 4 using the optical fiber temperature sensor 5 is caused. Detect height position. And the water level (namely, the water level of the cooling water in RPV1) inside the liquid level formation piping part 4 is calculated from the detected height position. The temperature measurement principle using the optical fiber temperature sensor 5 will be described later.

  Specifically, the optical fiber temperature sensor 5 is disposed from the upper part to the lower part inside the liquid level forming pipe part 4. The optical fiber used for the optical fiber temperature sensor 5 is preferably excellent in radiation resistance. The optical fiber temperature sensor 5 is connected to a processing device 9 provided outside the reactor containment vessel 10 via an instrumentation penetration 6 provided in the reactor containment vessel 10. The processing device 9 is provided with a light source 7 and a detection unit 8. The light source 7 generates pulsed light that enters the optical fiber temperature sensor 5.

  The detection unit 8 detects the scattered light inside the optical fiber temperature sensor 5 by the pulsed light generated by the light source 7 and measures the temperature at an arbitrary position of the optical fiber temperature sensor 5. In this way, the detection unit 8 can obtain information on the temperature distribution of the optical fiber temperature sensor 5. Then, in the detection unit 8, based on the obtained temperature distribution information, a position where a temperature difference occurs between the gas phase part and the liquid layer part in the liquid level forming pipe part 4 (that is, cooling water inside the liquid level forming pipe part 4). Water level). The detection unit 8 converts the calculation result into information on the water level of the cooling water in the RPV 1 and outputs the information to the outside.

  FIG. 2 is a diagram for explaining the temperature measurement principle using the optical fiber temperature sensor 5. When pulsed light is incident by the light source 7 provided in the processing device 9, the incident pulsed light is scattered very slightly at each part of the optical fiber (that is, the optical fiber temperature sensor 5). Part of the scattered light returns to the end (incident end) where the light from the optical fiber is incident as backscattered light. The delay time of the backscattered light (the time from when the light pulse is incident until the backscattered light returns to the incident end) depends on the distance of the optical fiber from the position where the scattered light is generated to the incident end. Further, the intensity of the Raman scattered light included in the back scattered light depends on the temperature of the optical fiber at the position where the scattering occurs.

  Therefore, the generation position of the Raman scattered light can be calculated from the propagation speed (known) of the light in the optical fiber and the delay time of the back scattered light. Further, the temperature of the optical fiber at the position where the scattering has occurred can be calculated based on the intensity of the Raman scattered light included in the backscattered light. Therefore, the detection unit 8 of the present embodiment detects backscattered light and measures (calculates) the temperature at an arbitrary position of the optical fiber temperature sensor 5 based on the delay time and intensity of the detected Raman scattered light.

The reactor water level meter 100 of the first embodiment described above has the following operational effects.
(1) The liquid level was formed in the liquid level forming pipe part 4 of the measurement pipe LP connected to the RPV 1. And the height position of the liquid level formed in the liquid level formation piping part 4 was comprised so that the optical fiber temperature sensor 5 might detect. This eliminates the need to detect the pressure difference between the gas phase portion and the liquid phase portion of the RPV 1 water level, so that a reference plane for forming the reference water level is not essential. Therefore, it is possible to eliminate the possibility that the accurate water level in the RPV 1 cannot be measured due to fluctuations in the reference water level, and can contribute to the operation management of the boiling water reactor.

(2) The optical fiber temperature sensor 5 is used to detect the height position of the liquid level formed in the liquid level forming pipe section 4. Thereby, since it is not necessary to provide an electronic circuit with low radiation resistance characteristics inside the reactor containment vessel 10 having a high radiation dose, the reliability of water level measurement can be improved.

(3) The measurement pipe LP is provided inside the reactor containment vessel 10. Thereby, the possibility that the cooling water of the RPV 1 leaks to the outside of the reactor containment vessel 10 can be reduced, and it can contribute to the fail-safety of the boiling water reactor.

(4) By connecting the lower piping part 3 to the bottom surface of the RPV 1, it is possible to lower the measurement lower limit of the water level of the RPV 1 as compared with the case where the lower piping part 3 is connected to the side surface of the RPV 1. Thereby, even if it is a case where the water level of RPV1 falls to the bottom face vicinity of RPV1, it is possible to measure the water level of RPV1.

--- Second Embodiment ---
With reference to FIG. 3, a second embodiment of a reactor water level gauge according to the present invention will be described. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and different points will be mainly described. Points that are not particularly described are the same as those in the first embodiment. The present embodiment is different from the first embodiment mainly in that the liquid level forming pipe section 4 is provided outside the reactor containment vessel 10.

  FIG. 3 is a schematic diagram related to RPV1 water level measurement using the reactor water level gauge 100 of the present embodiment. In addition, in FIG. 3, the structure regarding the water level measurement of RPV1 is mainly described among each structure of a boiling water reactor, and the description about the other structure is abbreviate | omitted. In the reactor water level meter 100 of the present embodiment, the upper piping portion 2 and the lower piping portion 3 of the measurement piping LP are connected to the outside of the reactor containment vessel 10 through the instrumentation penetration 6 provided in the reactor containment vessel 10. Lead to. Then, the upper piping section 2 and the lower piping section 3 are connected to the liquid level forming piping section 4 outside the reactor containment vessel 10.

  As described in the first embodiment, the use of the optical fiber temperature sensor 5 eliminates the need to provide an electronic circuit with low radiation resistance characteristics inside the reactor containment vessel 10. However, even if an optical fiber excellent in radiation resistance is used as the optical fiber temperature sensor 5, it is desirable that the exposure amount of the optical fiber is small. Therefore, the amount of exposure of the optical fiber temperature sensor 5 can be reduced by providing the liquid level forming pipe portion 4 outside the reactor containment vessel 10 as in the present embodiment, so that the durability of the optical fiber temperature sensor 5 can be reduced. Can be improved. Thereby, the reliability of water level measurement can be improved and it can contribute to the operation management of a boiling water reactor.

  Further, by improving the durability of the optical fiber temperature sensor 5, the inspection frequency and replacement frequency of the optical fiber temperature sensor 5 can be reduced, and the maintenance cost can be reduced. Furthermore, by providing the liquid level forming pipe part 4 outside the reactor containment vessel 10, it becomes possible to monitor the liquid level forming pipe part 4 and the optical fiber temperature sensor 5 by a person or a machine, and the maintainability is improved.

--- Third embodiment ---
A third embodiment of a reactor water level meter according to the present invention will be described with reference to FIG. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and different points will be mainly described. Points that are not particularly described are the same as those in the first embodiment. In the reactor water level meter 100 of the present embodiment, a conventional reactor water level meter based on the differential pressure between the water head pressure at the reference water level and the water head pressure at the reactor water level and the optical fiber temperature sensor 5 are mainly used. It differs from the first embodiment in that an RPV1 water level measuring device (reactor water level meter 100) is also provided.

  FIG. 4 is a schematic diagram relating to the water level measurement of the RPV 1 of the present embodiment. In FIG. 4, among the configurations of the boiling water reactor, the configuration related to the water level measurement of the RPV 1 is mainly described, and the description of the other configurations is omitted. A reference plane 11 is further provided inside the reactor containment vessel 10 of the present embodiment. Further, a differential pressure type water level measuring device 12 is further provided outside the reactor containment vessel 10. Since a conventional reactor water level meter using the reference surface unit 11 and the differential pressure type water level measuring device 12 is known, detailed description thereof will be omitted.

  In the present embodiment, a reactor water level meter 100 using an optical fiber temperature sensor 5 is provided as a backup device for a conventional reactor water level meter. In the reactor water level gauge 100 of the present embodiment, the upper pipe part 2 connects the upper part of the liquid level forming pipe part 4 and the gas phase part of the reference surface unit 11. Thereby, the upper part of the liquid level forming pipe part 4 is connected to the gas phase part of the RPV 1 through the gas phase part of the reference surface unit 11.

  By comprising in this way, the backup apparatus of the water level measuring apparatus of RPV1 of a prior art can be provided by simple structure, and it can contribute to operation management of a boiling water reactor.

--- Fourth embodiment ---
A fourth embodiment of a reactor water level gauge according to the present invention will be described with reference to FIG. In the following description, the same components as those in the third embodiment are denoted by the same reference numerals, and different points will be mainly described. Points that are not particularly described are the same as those in the third embodiment. The present embodiment is different from the third embodiment mainly in that the liquid level forming pipe section 4 is provided outside the reactor containment vessel 10.

  FIG. 5 is a schematic diagram relating to the water level measurement of the RPV 1 of the present embodiment. In FIG. 5, among the configurations of the boiling water reactor, the configuration related to the water level measurement of the reactor pressure vessel is mainly described, and the description of the other configurations is omitted. In the reactor water level meter 100 of the present embodiment, the upper piping portion 2 and the lower piping portion 3 of the measurement piping LP are connected to the outside of the reactor containment vessel 10 through the instrumentation penetration 6 provided in the reactor containment vessel 10. Lead to. Then, the upper piping section 2 and the lower piping section 3 are connected to the liquid level forming piping section 4 outside the reactor containment vessel 10.

  As described in the second embodiment, even if an optical fiber having excellent radiation resistance is used as the optical fiber temperature sensor 5, it is desirable that the amount of exposure of the optical fiber is small. Therefore, the amount of exposure of the optical fiber temperature sensor 5 can be reduced by providing the liquid level forming pipe portion 4 outside the reactor containment vessel 10 as in the present embodiment, so that the durability of the optical fiber temperature sensor 5 can be reduced. Can be improved. Thereby, the reliability of the reactor water level meter 100 as a backup device can be improved, and it can contribute to the operation management of a boiling water reactor.

  In the above description, when the RPV 1 water level measuring device of the prior art is provided, the upper part of the liquid level forming pipe part 4 is connected to the gas phase part of the RPV 1 through the gas phase part of the reference surface unit 11. However, the present invention is not limited to this. For example, regardless of the presence or absence of the reference plane device 11, the upper pipe part 2 may be configured to directly connect the upper part of the liquid level forming pipe part 4 and the gas phase part of the RPV 1.

  Each embodiment and modification described above are merely examples, and the present invention is not limited to these contents as long as the features of the invention are not impaired.

  The present invention is not limited to the above-described embodiment, and the upper pipe connected to the gas phase part in the reactor pressure vessel and the lower part connected to the liquid layer part at the bottom of the reactor pressure vessel The pipe part, the liquid level forming pipe part that connects the upper pipe part and the lower pipe part to form a liquid level inside, and the liquid level forming pipe part are arranged from the top to the bottom of the liquid level forming pipe part. An optical fiber temperature sensor having an optical fiber installed, a light source of pulsed light incident on the optical fiber, and scattered light generated in the optical fiber are detected, and at any position of the optical fiber based on the detected scattered light Based on the temperature at the arbitrary position of the optical fiber detected by the temperature detection unit that detects the temperature and the temperature detection unit, the position where the temperature difference between the gas phase part and the liquid layer part in the liquid level forming pipe part occurs A liquid level position calculation unit that calculates the position of A water level information output unit for converting and outputting the water level information of the cooling water in the reactor pressure vessel based on the position of the liquid level calculated by the device calculation unit. It includes the total.

DESCRIPTION OF SYMBOLS 1 Reactor pressure vessel (RPV) 2 Upper piping part 3 Lower piping part 4 Liquid level formation piping part 5 Optical fiber temperature sensor 6 Instrumentation penetration 7 Light source 8 Detection part 9 Processing apparatus 10 Reactor containment vessel 11 Reference surface unit 12 Difference Pressure type water level measuring device 100 Reactor water level meter LP Measuring pipe

Claims (4)

An upper piping connected to the gas phase in the reactor pressure vessel;
A lower piping connected to the liquid layer at the bottom of the reactor pressure vessel;
A liquid level forming pipe part that connects between the upper pipe part and the lower pipe part to form a liquid level inside;
An optical fiber temperature sensor having an optical fiber disposed from the upper part to the lower part of the liquid level forming pipe part inside the liquid level forming pipe part;
A light source of pulsed light incident on the optical fiber;
A temperature detector that detects scattered light generated in the optical fiber and detects a temperature at an arbitrary position of the optical fiber based on the detected scattered light;
Based on the temperature at the arbitrary position of the optical fiber detected by the temperature detection unit, a liquid that calculates the position where the temperature difference between the gas phase part and the liquid layer part in the liquid level forming pipe part occurs as the position of the liquid level A surface position calculation unit;
A water level information output unit that converts the level of the coolant level in the reactor pressure vessel based on the position of the liquid level calculated by the level level calculation unit and outputs the information. Reactor water level gauge. Reactor water level gauge according to claim 1,
A reference surface unit that forms a reference water level by condensing steam introduced from a gas phase portion of the reactor pressure vessel;
Outputs the water level information of the cooling water in the reactor pressure vessel based on the pressure difference between the head pressure at the reference water level formed by the reference plane and the head pressure at the liquid layer of the reactor pressure vessel. And a differential pressure reactor water level meter
The upper piping part is connected to the gas phase part in the reactor pressure vessel through the gas phase part of the reference surface unit by being connected to the gas phase part of the reference surface unit. Reactor water level meter. In the reactor water level meter according to claim 1 or 2,
The reactor water level meter, wherein the liquid level forming part is disposed inside a reactor containment vessel. In the reactor water level meter according to claim 1 or 2,
A reactor water level gauge, wherein the liquid level forming part is disposed outside a reactor containment vessel.

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