JP6366475B2 - Water level measuring device for spent fuel pool - Google Patents

Description

  The present invention relates to an apparatus for measuring a water level of a spent fuel pool of a nuclear power plant.

  As a means of confirming the soundness of a spent fuel pool for storing spent fuel in a nuclear power plant, there is a measurement of the water level of the spent fuel pool. The spent fuel pool stores cooling water and accommodates a spent fuel rack that houses spent fuel assemblies. The spent fuel pool cooling water removes decay heat of the spent fuel and shields radiation. It is necessary to be able to always measure the water level of the cooling water (water level of the spent fuel pool), and it is important to be able to check the water level especially at the time of an accident.

  For this reason, various techniques for measuring the water level of the spent fuel pool have been proposed. For example, Patent Document 1 describes a highly reliable water level measuring device that can operate without being damaged even when an accident occurs. This water level measuring device includes a plurality of water level measuring means having different positions in the depth direction of the liquid tank inside the protective tube.

JP 2013-40822 A

  In the water level measuring device described in Patent Document 1, a protective tube necessary for measuring the water level is fixed to the liquid tank wall by two supporting members (stoppers). One of the two supporting members is fixed to the liquid tank wall below the water surface. The spent fuel pool of the nuclear power plant corresponds to this liquid tank. In order to stably measure the water level of the spent fuel pool, it is desirable that the water level measuring device be fixed to the spent fuel pool wall at the lower part thereof (that is, below the water level of the spent fuel pool). Lining material is attached to the spent fuel pool wall to prevent leakage of cooling water, but if the above support material is fixed to the spent fuel pool wall, the part where the support material is fixed in the event of an earthquake, etc. There is a possibility that a crack will occur in the water, and cooling water leaks from the crack and the water level of the cooling water decreases.

  As described above, the conventional water level measuring device is fixed to the spent fuel pool wall even under the surface of the spent fuel pool, so if a crack occurs in the fixed part, leakage of the cooling water from the spent fuel pool is caused. There is a risk of lowering the coolant level.

  An object of the present invention is to provide a water level measuring device for a spent fuel pool that does not need to be fixed to a spent fuel pool wall below the surface of the spent fuel pool.

  A spent fuel pool water level measuring device according to the present invention comprises a plurality of water level detectors for measuring the level of a spent fuel pool containing cooling water, and a water level detector protective tube storing a plurality of the water level detectors. Prepare. The water level detector protective tube has a structure that can be stored in a spent fuel rack. In the spent fuel pool water level measuring device according to the present invention, the spent fuel rack is accommodated by using a plurality of the water level detectors in a state where the water level detector protective tube is accommodated in the spent fuel rack. The water level of the spent fuel pool is measured.

  ADVANTAGE OF THE INVENTION According to this invention, the water level measuring apparatus of a spent fuel pool which does not need to be fixed to a spent fuel pool wall below the water surface of a spent fuel pool can be provided.

It is a figure which shows the structure of the water level measuring apparatus of the spent fuel pool by Example 1 of this invention. It is a figure which shows a water level detector protective tube. It is a figure which shows the internal structure of a water level detector protective tube. It is a figure which shows the upper part of a water level detector protective tube. It is a figure which shows the lower part of a water level detector protective tube. It is a figure which shows the structure of a water level detector. It is a figure explaining the relationship between a water level detector and the water level of cooling water. It is a figure which shows the example of the output signal of the thermocouple at the time of the heating by a heater wire. It is a figure which shows the structure of the water level measuring apparatus of the spent fuel pool by Example 2 of this invention. It is a figure which shows the structure of the water level measuring apparatus of the spent fuel pool by Example 3 of this invention. In Example 4, it is a figure which shows the optimal installation position to the spent fuel rack of the water level measuring device by this invention. It is a figure which shows the structure of the water level measuring apparatus of the spent fuel pool by Example 5 of this invention. It is a figure which shows the structure of the water level measuring apparatus of the spent fuel pool by Example 6 of this invention. It is a figure which shows the structure of the water level measuring apparatus of the spent fuel pool by Example 7 of this invention. It is a figure which shows the structure of the water level measuring apparatus of the spent fuel pool by Example 8 of this invention.

  A spent fuel pool water level measuring device according to the present invention includes a plurality of water level detectors for measuring the water level of a spent fuel pool containing cooling water, and a water level detector protective tube storing a plurality of water level detectors. The water level of the spent fuel pool in which the spent fuel rack is accommodated is measured in a state where the water level detector protective tube is accommodated in the spent fuel rack. Since the water level detector protection pipe is stored in the spent fuel rack and the water level of the spent fuel pool is measured, it is necessary to fix the water level detector protection pipe to the spent fuel pool wall at a position lower than the water level of the spent fuel pool. There is no. For this reason, a crack is not generated in the spent fuel pool wall due to an earthquake or the like, and the coolant does not leak from the crack and the water level of the spent fuel pool does not decrease.

  Hereinafter, a spent fuel pool water level measuring apparatus according to an embodiment of the present invention will be described with reference to the drawings. Note that in the drawings used in this specification, the same elements are denoted by the same reference numerals, and repeated description of these elements may be omitted. Hereinafter, the water level measuring device for the spent fuel pool is also simply referred to as “water level measuring device”.

  A spent fuel pool water level measuring apparatus according to a first embodiment of the present invention will be described. The water level measuring device according to this embodiment is installed in a spent fuel rack. More specifically, the water level measuring device includes a water level detector protective tube for storing the water level detector, and this water level detector protective tube is accommodated in the spent fuel rack. One or more water level measuring devices are installed in the spent fuel rack.

  FIG. 1 is a diagram illustrating a configuration of a water level measuring apparatus 1 according to the present embodiment. The spent fuel pool 10 contains a spent fuel rack 9 and a cooling water 15 in which the spent fuel rack 9 is immersed. The spent fuel pool 10 may be referred to as a spent fuel pit. The spent fuel rack 9 includes a plurality of storage cells arranged in a lattice pattern, and the spent fuel assemblies are stored in these storage cells. The spent fuel assembly stored in the spent fuel rack 9 is shielded from radiation by removing decay heat of the spent fuel by the cooling water 15.

  In the spent fuel pool 10, a wall lining material 11 and a floor lining material 13 are respectively attached to a spent fuel pool wall 12 and a spent fuel pool floor 14 for the purpose of preventing leakage of the cooling water 15.

  The spent fuel pool 10 includes a weir 16 extending upward from the spent fuel pool floor 14 at a part of the outer periphery. A clearance surge tank 17 is provided adjacent to the weir 16. The skimmer surge tank 17 is a tank for receiving the coolant 15 that has overflowed from the spent fuel pool 10 over the weir 16.

  The water level measuring device 1 includes a plurality of (n in FIG. 1, n is an integer of 2 or more) water level detectors 4-1, 4-2,. A device 6, a cable 7, and a connector 8 are provided. The water level detector protective tube 2 stores the water level detectors 4-1, 4-2,..., 4-n, and the handle 3 is attached to the upper part. The water level detectors 4-1, 4-2,... 4-n are connected to the measurement control device 6 by the cable 7. In the cable 7, a connector 8 connects a portion connected to the water level detectors 4-1, 4-2,..., 4-n and a portion connected to the measurement control device 6. The water level measuring device 1 measures the water level of the spent fuel pool 10 in a state where the water level detector protection tube 2 is housed in the spent fuel rack 9. When a plurality of water level measuring devices 1 are installed in the spent fuel rack 9, one measurement control device 6 may be provided for all the water level measuring devices 1, and each water level measuring device 1 has a measurement control device. 6 may be provided one by one.

  FIG. 2 is a view showing the water level detector protective tube 2. The water level detector protective tube 2 has a structure that can be stored in the spent fuel rack 9, and is stored in the spent fuel rack 9. That is, the water level detector protective tube 2 has a shape and a size that can be stored in the spent fuel rack 9. The shape and size of the water level detector protective tube 2 are preferably the same as the spent fuel assembly housed in the spent fuel rack 9, but the shape and size are not limited to this, and the spent fuel rack 9 is not limited to this shape and size. Any shape and size that can be stored in the storage cell. For example, the shape may be a cylindrical shape, and the overall size may be smaller than the spent fuel assembly stored in the spent fuel rack 9. Moreover, the size of the cross section perpendicular to the length direction of the water level detector protective tube 2 may be the same as or smaller than the size of the cross section perpendicular to the length direction of the spent fuel assembly. The length of the water level detector protective tube 2 may be longer or shorter than the spent fuel assembly as long as the water level of the spent fuel pool 10 can be measured, and can be arbitrarily determined.

  Further, the lower part (particularly the outer shape of the lower part) of the water level detector protective tube 2 can have the same structure as the lower tie plate of the spent fuel assembly housed in the spent fuel rack 9. In FIG. 2, as an example, the water level detector protective tube 2 whose lower part has the same structure as the lower tie plate of the spent fuel assembly is shown. If the lower part of the water level detector protection tube 2 has the same structure as the lower tie plate of the spent fuel assembly, the water level detector protection tube 2 can be easily accommodated in the storage cell of the spent fuel rack 9.

  The handle 3 is used to suspend the water level detector protective tube 2 by a crane (not shown). The water level detector protective tube 2 storing the water level detector 4-1,..., 4-n can be easily installed on the spent fuel rack 9 by hanging the handle 3 attached to the upper part with a crane. It can be easily taken out from the spent fuel rack 9. The cable 7 can be disconnected in the middle due to the presence of the connector 8. The water level measuring device 1 can be easily removed from the spent fuel rack 9 for maintenance by disconnecting the cable 7 in the middle.

  The spent fuel rack 9 may house not only the water level detector protective tube 2 but also the spent fuel assembly. That is, the water level detector protective tube 2 can be stored in an empty storage cell among the storage cells of the used fuel rack 9 in which the used fuel assembly is stored.

  The water level detector protective tube 2 is suspended by the handle 3 and stored in the spent fuel rack 9 in the same manner as the spent fuel assembly. The water level detector protection tube 2 can be stored in the spent fuel rack 9 at any time. For example, the water level detector protective tube 2 can be stored in the fuel rack 9 before or after storing the spent fuel assembly in the spent fuel rack 9. can do.

  FIG. 3 is a diagram showing an internal configuration of the water level detector protective tube 2. The water level detector protective tube 2 includes a plurality (n in FIG. 3) of water level detectors 4-1, 4-2, 4-3,..., 4-n and a plurality (m in FIG. 3, m is 2 or more). ) Support grid plates 22-1, 22-2, 22-3, 22-4, 22-5,... 22-m. m may be equal to or different from n. FIG. 3 shows a case where n = 4 for simplicity.

  The water level detectors 4-1,..., 4-n are installed such that the lengths of the spent fuel pool 10 in the depth direction are different from each other, and the positions of the lower ends of the spent fuel pool 10 in the depth direction are different from each other. . The supporting grid plates 22-1 to 22-m are installed so that the positions of the spent fuel pool 10 in the depth direction are different from each other, and the water level detectors 4-1,. It is a plate-shaped member fixed to. As a result, even if, for example, an earthquake or an impact during transportation occurs, the water level detectors 4-1,.

  The water level detector protective pipe 2 includes water inlets 23 and 24 at the upper and lower parts, respectively. When the water level detector protective pipe 2 is stored in the spent fuel rack 9 and measures the water level of the spent fuel pool 10, The cooling water 15 can flow into the inside from the water flow ports 23 and 24. For this reason, the same water level as the spent fuel pool 10 can be secured inside the water level detector protective tube 2. Since the water level detector protective tube 2 is housed in the spent fuel rack 9, the water level measuring device 1 can also measure the water level at the bottom of the spent fuel rack 9, that is, at the bottom of the spent fuel assembly. is there.

  FIG. 4 is a diagram showing the upper part of the water level detector protective tube 2, and is a configuration diagram of the water level detector protective tube 2 as viewed from the upper part (the handle 3 side). FIG. 5 is a view showing the lower part of the water level detector protective tube 2 and is a configuration diagram of the water level detector protective tube 2 as viewed from below. FIG. 4 shows a case where n = 4 as in FIG. As shown in FIGS. 4 and 5, water inlets 23-1 and 23-2 are provided in the upper part of the water level detector protective pipe 2, and water outlets 24-1 and 24-2 are provided in the lower part of the water level detector protective pipe 2. 24-2 and 24-3 are provided. With these water openings, the cooling water 15 can enter the water level detector protective pipe 2 from the upper part or the lower part, and the same as the spent fuel pool 10 in the water level detector protective pipe 2. It is possible to keep the water level. As a result, the water level around the water level detectors 4-1,..., 4-n is the same as the water level of the spent fuel pool 10, and the water level of the spent fuel pool 10 can be detected by these water level detectors. it can.

  In this embodiment, two water outlets are provided in the upper part of the water level detector protective pipe 2, and three water outlets are provided in the lower part of the water level detector protective pipe 2. The number of water inlets is arbitrary as long as the cooling water 15 can enter the inside of the water level detector protective pipe 2 and can maintain the same water level as the spent fuel pool 10 inside the water level detector protective pipe 2. Can be determined.

  FIG. 6 is a diagram showing the configuration of the water level detector. In FIG. 6, the configuration of the water level detector 4-1 is shown as an example, but the other water level detectors 4-2 to 4-n also have the same configuration as the water level detector 4-1. In FIG. 6, only the lower part (tip part) of the water level detector 4-1 is shown.

  The water level detector 4-1 includes a thermocouple 4-11, a heater wire 4-12a for heating the vicinity of the thermocouple 4-11, a power source for the heater wire 4-12a and the heater wire 4-12a (measurement in FIG. 1). A heater lead wire 4-12b, an insulating material 4-13, and a sheath 4-14 connected to the control device 6) are provided. A widely used K-type or N-type thermocouple can be used as the thermocouple 4-11. A high resistance wire of nickel-chromium alloy is suitable for the heater wire 4-12a. The heater lead wire 4-12b can suppress a voltage required for the power source of the heater wire 4-12a by using a wire having a relatively low resistance such as a copper wire or a nickel wire. The insulating material 4-13 can use an insulating material such as magnesia or alumina, and electrically insulates the thermocouple 4-11, the heater wire 4-12a, and the heater lead wire 4-112b. The sheath 4-14 is made of, for example, stainless steel and houses the thermocouple 4-11, the heater wire 4-12a, the heater lead wire 4-12b, and the insulating material 4-13. The thermocouple 4-11 and the heater lead wire 4-12b are connected to the measurement control device 6 through the connector 8 by the cable 7.

  As shown in FIG. 6, at the lower part (tip part) of the water level detector 4-1, a joining part of two kinds of metals of the thermocouple 4-11 (temperature measuring part 4-11 t of the thermocouple 4-11) and a heater. Line 4-12a is located. The heater wire 4-12a heats the periphery of the temperature measuring unit 4-11t of the thermocouple 4-11.

  The plurality of water level detectors 4-1,..., 4-n stored in the water level detector protection tube 2 are in the spent fuel pool 10 in a state where the water level detector protection tube 2 is stored in the spent fuel rack 9. The positions of the lower ends in the depth direction are different from each other. Therefore, the thermocouple of the water level detector is stored in the spent fuel rack 9 in the water level detector protective tube 2 and when the water level of the spent fuel pool 10 is measured, the position of each temperature measuring unit is the spent fuel pool. 10 different depth directions.

  A method for measuring the water level of the spent fuel pool 10 of the water level measuring device 1 according to this embodiment will be described with reference to FIGS. 7 and 8. FIG. 7 is a diagram for explaining the relationship between the water level detector and the water level of the cooling water 15. The water level of the cooling water 15 in the spent fuel pool 10 is determined between the water level detector 4-1 and the water level detector 4-2. It is a figure which shows the state in between. FIG. 8 is a diagram illustrating an example of an output signal of a thermocouple during heating by a heater wire.

  As shown in FIG. 7, the water level detector protective tube 2 houses the water level detectors 4-1 and 4-2, and the water level detector 4-1 includes a thermocouple 4-11 and a heater wire 4-12a. The water level detector 4-2 includes a thermocouple 4-21 and a heater wire 4-22a. Since the water level of the cooling water 15 is between the water level detector 4-1 and the water level detector 4-2, the lower part (tip portion) of the water level detector 4-1 is in the air, and the water level detector 4-4. The lower part of 2 is in cooling water. That is, the temperature measuring unit 4-11t and the heater wire 4-12a of the thermocouple 4-11 of the water level detector 4-1 are located in the air, and the temperature of the thermocouple 4-21 of the water level detector 4-2 is measured. The part 4-21t and the heater wire 4-22a are located in water.

  The water level is measured by the water level measuring device 1 by measuring a temperature change due to Joule heat generated when the heater wire is energized with a thermocouple. Since this temperature change differs depending on whether or not the cooling water 15 exists around the water level detector, this temperature change is measured to determine whether or not the cooling water 15 is around the water level detector. Thus, the water level of the cooling water 15 can be measured.

  The measurement control device 6 (FIG. 1) applies a predetermined current to the heater wires 4-12a and 4-22a of the water level detectors 4-1 and 4-2, but before this energization (that is, Before heating by the heater wires 4-12a and 4-22a), the measurement control device 6 measures the output signals of the thermocouples 4-11 and 4-21 of the water level detectors 4-1 and 4-2. .

  When the measurement control device 6 supplies a predetermined current to the heater wire 4-12a of the water level detector 4-1, the heater wire 4-12a generates Joule heat. The periphery of the lower part of the water level detector 4-1 is in the air (in the air), and since there is no cooling water 15, the generated Joule heat is not taken away by the cooling water 15, and the heater wire 4-12a The ambient temperature rises relatively high and varies greatly.

  On the other hand, when the measurement control device 6 supplies a predetermined current to the heater wire 4-22a of the water level detector 4-2, the heater wire 4-22a generates Joule heat. The area around the lower part of the water level detector 4-2 is underwater, the generated Joule heat is taken away by the cooling water 15, and the temperature around the heater wire 4-22a rises relatively low and does not change much.

  FIG. 8 shows an output signal 25 that is a response of the thermocouple 4-11 of the water level detector 4-1 and an output signal 26 that is a response of the thermocouple 4-21 of the water level detector 4-2. An example is shown. In the heater heating period from time t1 to t2, the temperature around the heater wire 4-12a rises relatively large, and the temperature detected by the thermocouple 4-11 is relatively high. However, the temperature around the heater wire 4-22a rises relatively small, and the temperature detected by the thermocouple 4-21 is relatively low. 4-21 outputs a signal with a small change like the output signal 26 of FIG.

  The measurement control device 6 measures the output signals 25 and 26 of the thermocouples 4-11 and 4-21, and the thermocouple 4 before energizing the output signals 25 and 26 and the heater wires 4-12a and 4-22a. The output signals of −11 and 4-21 are respectively compared. When the change of the output signals of the thermocouples 4-11 and 4-21 is large before and after energization of the heater wires 4-12a and 4-22a, the lower part of the water level detector equipped with this thermocouple is positioned in the air. If the change is small, it is determined that the lower part of the water level detector including this thermocouple is located in the cooling water. Alternatively, a predetermined threshold is set for the output signals 25 and 26 (FIG. 8) of the thermocouples 4-11 and 4-21, and the output signal 25 is supplied after energizing the heater wires 4-12a and 4-22a. , 26 indicates a value equal to or higher than this threshold value, it is determined that the lower part of the water level detector provided with this thermocouple is located in the air. When a value lower than this threshold value is indicated, the water level provided with this thermocouple is determined. You may make it judge that the lower part of a detector is located in cooling water.

  The measurement control device 6 performs the above-described processing on all the water level detectors 4-1,..., 4-n, and a water level detector in which a change in the output signal of the thermocouple is large before and after energizing the heater wires. Obtain a small water level detector (or a water level detector whose output signal shows a value greater than or equal to the threshold value after energizing the heater wire) and a water level whose lower part is located in the air. A detector and a water level detector whose lower part is located in the cooling water are determined. Then, the measurement control device 6 determines that the water level of the spent fuel pool 10 is between the positions of the lower ends of two water level detectors: a water level detector whose lower part is located in the air and a water level detector whose lower part is located in the cooling water. (To be more precise, the lower end of the water level detector whose lower part is located in the air, and the uppermost water level detector of which the lower part is located in the cooling water. It is determined that it exists between the lower end position of the The measurement control device 6 determines the water level of the spent fuel pool 10 based on the position of the lower end of these two water level detectors and the installation interval (interval of the position of the lower end) in the depth direction of the spent fuel pool 10. And display the determined water level.

  In the example illustrated in FIG. 7, the measurement control device 6 includes a lower end position of the water level detector 4-1 in which the lower part is located in the air and a lower end position of the water level detector 4-2 in which the lower part is located in the cooling water. In the meantime, it is determined that the water level of the spent fuel pool 10 is located. And the measurement control apparatus 6 is based on the position of the lower end of the water level detector 4-1 and the water level detector 4-2 in the depth direction of the used fuel pool 10 and the installation interval thereof, and the spent fuel pool 10. Determine the water level.

  By increasing the number of water level detectors and narrowing the interval between water level detectors in the depth direction of the spent fuel pool 10, the water level measurement resolution of the spent fuel pool 10 can be increased and used. The water level of the fuel pool 10 can be obtained more accurately.

  In addition, as a water level detector, the pressure type water level detector which detects the water pressure of the cooling water 15 with a diaphragm and measures a water level can also be used. When a pressure type water level detector is used, only one pressure type water level detector is installed near the spent fuel pool floor 14. The pressure-type water level detector measures the water pressure of the cooling water 15 with a diaphragm, converts the measured water pressure into an electric signal with a pressure-electric converter, and transmits the electric signal to the measurement control device 6. The measurement control device 6 obtains the water level of the spent fuel pool 10 from the water pressure measured by the pressure-type water level detector using the fact that the water level is proportional to the water pressure. When the pressure type water level detector is used, there is an effect that the water level can be continuously measured in the depth direction of the spent fuel pool 10.

  In the water level measuring device 1 according to the present embodiment, the water level detector protective tube 2 is housed in the spent fuel rack 9, so that it is not necessary to fix the water level detector protective tube 2 to the spent fuel pool wall 12 with a support material. . For this reason, the water level measuring device 1 according to the present embodiment may cause a crack in the spent fuel pool wall 12 due to an earthquake or the like, and the coolant 15 may leak from the crack and the water level in the spent fuel pool 10 may decrease. Has no effect. Furthermore, since the lower part of the water level detector protective tube 2 is fixed to the spent fuel rack 9 in the water level measuring device 1 according to the present embodiment, the water level of the spent fuel pool 10 can be stably measured. Also have.

  A spent fuel pool water level measuring apparatus according to Embodiment 2 of the present invention will be described with reference to FIG. In the water level measuring apparatus according to the present embodiment, a water level detector protective tube for storing a water level detector is installed in a used fuel rack, and a part thereof is supported by a used fuel pool wall.

  FIG. 9 is a diagram showing a configuration of the water level measuring apparatus 1 according to the present embodiment. The water level measuring device 1 according to the present embodiment has the same configuration as that of the water level measuring device 1 (FIG. 1) according to the first embodiment, but the upper portion of the water level detector protective tube 2 is supported by the support material 18 on the spent fuel pool wall 12. This is different from the first embodiment in that it is fixed. In the following description, a configuration different from the first embodiment will be described.

  The support member 18 is a member that connects and fixes the water level detector protection tube 2 to the spent fuel pool wall 12 with hooks or bolts, and is attached to the spent fuel pool wall 12 at a position higher than the upper surface of the weir 16. Therefore, the water level of the spent fuel pool 10 does not reach the position where the support member 18 is attached to the spent fuel pool wall 12. For this reason, even if a crack occurs in the attachment position of the support member 18 to the spent fuel pool wall 12, the cooling water 15 does not leak from the crack. The wall lining material 11 is attached to the spent fuel pool wall 12 so as to surround the connection portion of the support material 18 to the spent fuel pool wall 12.

  By using the support member 18, the water level measuring device 1 according to the present embodiment fixes the lower part of the water level detector protection tube 2 to the spent fuel rack 9 and the upper part to the spent fuel pool wall 12. Therefore, the fixing ability is further enhanced, and the water level of the spent fuel pool 10 can be measured more stably.

  Further, since the support member 18 can be fixed to the water level detector protection tube 2 and the spent fuel pool wall 12 with hooks or bolts, the support member 18 can be easily formed from the water level detector protection tube 2 and the spent fuel pool wall 12. Can be separated. Therefore, the water level measuring device 1 can be easily taken out from the spent fuel rack 9 for maintenance or the like.

  A spent fuel pool water level measuring apparatus according to Embodiment 3 of the present invention will be described with reference to FIG. In the water level measuring apparatus according to the present embodiment, a water level detector protective tube for storing a water level detector is installed in the spent fuel rack, and a part thereof is supported by the upper floor of the spent fuel pool.

  FIG. 10 is a diagram illustrating a configuration of the water level measuring apparatus 1 according to the present embodiment. The water level measuring device 1 according to the present embodiment has the same configuration as the water level measuring device 1 (FIG. 1) according to the first embodiment, but the upper portion of the water level detector protective tube 2 is the upper portion of the spent fuel pool 10 with the support material 19. The point which is being fixed to the floor 27 is different from the first embodiment. In the following description, a configuration different from the first embodiment will be described.

  In the water level measuring apparatus 1 according to the present embodiment, the water level detector protective tube 2 has an L shape having a vertical part and a horizontal part. The vertical portion is stored in the spent fuel rack 9 in the same manner as the water level detector protective tube 2 of the first embodiment. The horizontal portion is provided in the upper portion of the vertical portion and extends to the upper floor 27 of the spent fuel pool 10. The horizontal portion at the top of the water level detector protective tube 2 is fixed to the upper floor 27 of the spent fuel pool 10 by a support member 19. The upper floor 27 is positioned higher than the upper surface of the weir 16.

  The support member 19 is a member that connects and fixes the horizontal portion of the water level detector protective tube 2 to the upper floor 27 of the spent fuel pool 10 with a hook or bolt, and is attached to the upper floor 27. Therefore, even if a crack occurs at the position where the support member 19 is attached to the upper floor 27, the cooling water 15 does not reach this position, so the cooling water 15 does not leak from this crack.

  By using the support member 19, the water level measuring device 1 according to the present embodiment has the lower part (vertical part) of the water level detector protection tube 2 fixed to the spent fuel rack 9 and the upper part of the spent fuel pool 10. Since it is fixed to the upper floor 27, the fixing ability is further enhanced, and the water level of the spent fuel pool 10 can be measured more stably.

  Further, the support member 19 can be fixed to the water level detector protective tube 2 and the upper floor 27 of the spent fuel pool 10 with hooks or bolts, and the worker can easily work on the upper floor 27. . For this reason, the support member 19 is easier to separate the support member 18 from the water level detector protection tube 2 and the spent fuel pool wall 12 in the second embodiment than the water level detector protection tube 2 and the upper floor 27. Can be separated from Therefore, the water level measuring device 1 can be taken out from the spent fuel rack 9 more easily for maintenance or the like.

  In the fourth embodiment, the optimum installation position of the water level measuring device 1 according to the present invention on the spent fuel rack 9 will be described with reference to FIG.

  FIG. 11 is a diagram showing an optimal installation position of the water level measuring device 1 on the spent fuel rack 9, and is a view of the spent fuel pool 10 as viewed from above. In FIG. 11, “■” indicates a position where the water level measuring device 1 is preferably installed in the storage cell 9 a of the spent fuel rack 9. Since one or more water level measuring devices 1 are installed in the spent fuel rack 9, the water level measuring devices 1 are installed at any one or a plurality of positions among the positions indicated by ■ in FIG. It is preferable to do this.

  The water level measuring device 1 is preferably installed on the outermost periphery of the spent fuel rack 9, as indicated by the black square in FIG. That is, the water level detector protective tube 2 of the water level measuring device 1 is preferably housed in a storage cell on the outermost periphery of the storage cells 9 a of the spent fuel rack 9. By installing the water level measuring device 1 on the outermost periphery of the spent fuel rack 9, the length of the cable 7 (see, for example, FIG. 1) can be shortened.

  However, as shown in FIG. 11, it is not preferable to install the water level measuring device 1 at the following position. The spent fuel assembly is moved from the reactor well 20 through the fuel transport passage 21 to the spent fuel pool 10 and stored in the spent fuel rack 9. The presence of the water level measuring device 1 on the travel route of the spent fuel assembly is not preferable because the movement of the spent fuel assembly to the spent fuel rack 9 is restricted. Further, since the coolant 15 that has passed over the weir 16 from the spent fuel pool 10 flows into the skimmer surge tank 17, the water level is measured in the flow path of the coolant 15 from the spent fuel pool 10 to the skimmer surge tank 17. The presence of the device 1 is not preferred.

  For this reason, as shown by ■ in FIG. 11, the water level measuring device 1 includes the region in the vicinity of the connection portion between the fuel transport passage 21 and the spent fuel pool 10 in the outermost periphery of the spent fuel rack 9, and It is preferable not to install in the area near the connecting portion between the weir 16 and the spent fuel pool 10. That is, the water level measuring device 1 is located on the outermost periphery of the spent fuel rack 9 at a position other than the vicinity of the connection portion between the fuel transport passage 21 and the spent fuel pool 10 and between the weir 16 and the spent fuel pool 10. It is preferable to install it at a position other than the vicinity of the connecting portion. When the water level measuring device 1 is installed in this manner, there is no restriction on the movement of the spent fuel assembly to the used fuel rack 9, and the water level measuring device 1 does not need to have a waterproof function or a water resistant function. There is an effect.

  A spent fuel pool water level measuring apparatus according to Embodiment 5 of the present invention will be described with reference to FIG. In the water level measuring apparatus according to the present embodiment, the water level detector protective tube for storing the water level detector is installed in the extended spent fuel rack.

  FIG. 12 is a diagram illustrating a configuration of the water level measuring device 1 according to the present embodiment. The water level measuring apparatus 1 according to the present embodiment has the same configuration as the water level measuring apparatus 1 (FIG. 1) according to the first embodiment, but the water level detector protective tube 2 is installed in the extended type spent fuel rack 28. Is different from the first embodiment. In the following description, a configuration different from the first embodiment will be described.

  The extended spent fuel rack 28 has the same internal structure as the spent fuel rack 9 and is disposed in the spent fuel pool 10 so as to be adjacent to the spent fuel rack 9. That is, the expansion type spent fuel rack 28 includes a storage cell similar to the spent fuel rack 9 and can store the spent fuel assembly and the water level detector protection tube 2 of the water level measuring device 1 in the storage cell. . The extended spent fuel rack 28 can be hung with a crane and placed in the spent fuel pool 10. For example, it can be attached to the spent fuel rack 9 already placed in the spent fuel pool 10 with a hook or the like. .

  If the distance between the spent fuel rack 9 and the spent fuel pool wall 12 is relatively wide, the length of the cable 7 connecting the water level detectors 4-1,..., 4-n and the measurement control device 6 must be increased. Moreover, it may be necessary to support the cable 7 between the water level detector protection tube 2 and the spent fuel pool wall 12, which is not preferable. For this reason, when the interval between the spent fuel rack 9 and the spent fuel pool wall 12 is relatively wide, as shown in FIG. 12, the extended spent fuel rack 28 is attached to the spent fuel rack 9, The water level measuring device 1 is installed in the extended spent fuel rack 28 (the water level detector protective tube 2 is accommodated in the extended spent fuel rack 28). In this way, the distance from the water level detector protection tube 2 to the spent fuel pool wall 12 can be shortened.

  When the extended spent fuel rack 28 is used as in the present embodiment, it is not necessary to increase the length of the cable 7 of the water level measuring device 1, and the cable 7 can be laid in the same manner as in the first embodiment. . Therefore, even if the distance between the spent fuel rack 9 and the spent fuel pool wall 12 is relatively wide, the water level of the spent fuel pool 10 can be measured in the same manner as in the first embodiment.

  A spent fuel pool water level measuring apparatus according to Embodiment 6 of the present invention will be described with reference to FIG. In the water level measuring apparatus according to the present embodiment, a water level detector protective tube for storing the water level detector is installed in the extended type spent fuel rack, and a part thereof is supported by the spent fuel pool wall.

  FIG. 13 is a diagram illustrating a configuration of the water level measuring apparatus 1 according to the present embodiment. The water level measuring device 1 according to the present embodiment has the same configuration as that of the water level measuring device 1 (FIG. 9) according to the second embodiment, and the upper portion of the water level detector protective tube 2 is fixed to the spent fuel pool wall 12 with a support material 18. However, the second embodiment is different from the second embodiment in that the water level detector protective tube 2 is installed in the extended spent fuel rack 28 as in the fifth embodiment.

  Therefore, even if the distance between the spent fuel rack 9 and the spent fuel pool wall 12 is relatively wide, the expanded spent fuel rack 28 is attached to the spent fuel rack 9 in the same manner as in the fifth embodiment. It is possible to measure the water level of the spent fuel pool 10 by installing the water level measuring device 1 in the spent fuel rack 28. Further, as in the second embodiment, the lower portion of the water level detector protective tube 2 is fixed to the extended type spent fuel rack 28 and the upper portion is fixed to the spent fuel pool wall 12, so that the fixing capability is further increased. As a result, the water level of the spent fuel pool 10 can be measured more stably. As a result, even if the distance between the spent fuel rack 9 and the spent fuel pool wall 12 is relatively wide, the water level of the spent fuel pool 10 can be measured as in the second embodiment.

  A spent fuel pool water level measuring apparatus according to Embodiment 7 of the present invention will be described with reference to FIG. In the water level measuring apparatus according to the present embodiment, a water level detector protective tube for storing a water level detector is installed in the extended type spent fuel rack, and a part thereof is supported on the upper floor of the spent fuel pool.

  FIG. 14 is a diagram showing a configuration of the water level measuring apparatus 1 according to the present embodiment. The water level measuring device 1 according to the present embodiment has the same configuration as the water level measuring device 1 (FIG. 10) according to the third embodiment, and the upper portion of the water level detector protective tube 2 is the support material 19 and the upper floor of the spent fuel pool 10. However, the water level detector protective tube 2 is different from the third embodiment in that the water level detector protective tube 2 is installed in the extended spent fuel rack 28 as in the fifth embodiment.

  Therefore, even if the distance between the spent fuel rack 9 and the spent fuel pool wall 12 is relatively wide, the expanded spent fuel rack 28 is attached to the spent fuel rack 9 in the same manner as in the fifth embodiment. It is possible to measure the water level of the spent fuel pool 10 by installing the water level measuring device 1 in the spent fuel rack 28. Similarly to the third embodiment, the lower part of the water level detector protective tube 2 is fixed to the extended spent fuel rack 28 and the upper part is fixed to the upper floor 27 of the spent fuel pool 10, so The water level of the spent fuel pool 10 can be measured more stably. As a result, even if the distance between the spent fuel rack 9 and the spent fuel pool wall 12 is relatively wide, the water level of the spent fuel pool 10 can be measured as in the third embodiment.

  A spent fuel pool water level measuring apparatus according to an eighth embodiment of the present invention will be described with reference to FIG. In Examples 1 to 7 described above, one or a plurality of water level measuring devices 1 are installed in the spent fuel rack 9. In this embodiment, a plurality of water level measuring devices 1 are installed in the used fuel rack 9. However, only one measurement control device 6 is installed, and the water level detectors 4-1, 4-2,..., 4-n stored in the plurality of water level detector protection tubes 2 are all one measurement control device. 6 is connected. In the following description, a configuration different from the above embodiment will be described.

  FIG. 15 is a diagram illustrating a configuration of the water level measuring device 1 according to the present embodiment. In FIG. 15, as an example, the case where two water level measuring devices 1 are installed in the spent fuel rack 9 is shown. For simplicity, the water level measuring device 1 includes a water level detector protective tube 2 and a water level detector 4-1. Only 4-2,..., 4-n are shown. Each of the water level detector protective tubes 2 (2a and 2b) includes n (n is an integer of 2 or more) water level detectors 4-1, 4-2, ... 4-n (4-1a, 4-2a, ...). 4-na and 4-1b, 4-2b,..., 4-nb) are stored.

  As described in the first embodiment, in each of the water level detector protection pipes 2, the water level detectors 4-1,..., 4-n have different lengths in the depth direction of the spent fuel pool 10, and spent fuel. The pool 10 is installed such that the positions of the lower ends in the depth direction are different from each other. This is because the water level of the spent fuel pool 10 is measured by the internal structure (FIGS. 6 and 7) under the water level detectors 4-1,.

  In the present embodiment, the water level detectors 4-1a,..., 4-na and 4-1b,..., 4-nb in the plurality of water level detector protection tubes 2a and 2b are the lengths in the depth direction of the spent fuel pool 10. Are different from each other, and the positions of the lower ends of the spent fuel pool 10 in the depth direction are all different from each other. That is, the thermocouples of the water level detector are all different from each other in the depth direction of the spent fuel pool 10 at the positions of the respective temperature measuring units. The output signals from the thermocouples located at the lower part (tip) of the water level detectors 4-1a,..., 4-na, 4-1b, ... 4-nb are transmitted to one measurement control device 6. As described in the first embodiment, the measurement control device 6 uses these output signals and the water level detectors 4-1a,..., 4-na, 4-1b,. The water level of the spent fuel pool 10 is determined based on the position of the lower end of -nb and the installation interval (interval of the position of the lower end).

  In the present embodiment, the water level of the used fuel pool 10 is measured by using a plurality of water level measuring devices 1 and making the positions of the lower ends of the water level detectors different in the depth direction of the used fuel pool 10. The resolution can be increased, and the water level of the spent fuel pool 10 can be obtained more accurately.

  The embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention described in the claims.

  For example, in the above-described embodiments, the configuration of the apparatus and the system is described in detail and specifically for easy understanding of the present invention, and the present invention is not necessarily limited to the one having all the configurations described. It is not something. Moreover, it is possible to replace a part of the configuration of a certain embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of a certain embodiment. Moreover, it is also possible to add, delete, or replace another configuration for a part of the configuration of each embodiment.

  DESCRIPTION OF SYMBOLS 1 ... Water level measuring device, 2 ... Water level detector protective tube, 3 ... Handle, 4-1, ... 4-n ... Water level detector, 4-11, 4-21 ... Thermocouple, 4-11t, 4-21t ... Thermocouple temperature measuring section, 4-12a, 4-22a ... heater wire, 4-12b ... heater lead wire, 4-13 ... insulating material, 4-14 ... sheath, 6 ... measurement control device, 7 ... cable, DESCRIPTION OF SYMBOLS 8 ... Connector, 9 ... Used fuel rack, 9a ... Storage cell, 10 ... Used fuel pool, 11 ... Wall lining material, 12 ... Used fuel pool wall, 13 ... Floor lining material, 14 ... Used fuel pool floor 15 ... cooling water, 16 ... weir, 17 ... skimmer surge tank, 18, 19 ... support material, 20 ... reactor well, 21 ... fuel transport passage, 22-1 ... 22-m ... support grid plate, 23, 23-1, 23-2 ... Water outlet, 24, 24-1, 24-2 24-3 ... passing Mizuguchi, 25, 26 ... output signal of the thermocouple, 27 ... upper floor of the spent fuel pool, 28 ... extended spent fuel racks.

Claims (8)

A plurality of water level detectors for measuring the water level of a spent fuel pool containing cooling water;
A water level detector protective tube storing a plurality of the water level detectors,
The water level detector protective tube has a structure that can be stored in a spent fuel rack,
In a state where the water level detector protective tube is stored in the used fuel rack, the water level of the used fuel pool in which the used fuel rack is stored is measured using a plurality of the water level detectors.
A water level measuring device for a spent fuel pool, characterized in that   2. The water level measuring device for a spent fuel pool according to claim 1, wherein the water level detector protective tube has the same shape and size as a spent fuel assembly housed in the spent fuel rack. The water level detector protective pipe is provided with water inlets at the top and bottom,
2. The spent fuel according to claim 1, wherein the cooling water can flow into the water level detector protective pipe from the water outlet in a state where the water level detector protective pipe is housed in the spent fuel rack. Pool water level measuring device. The spent fuel pool comprises a weir;
2. The spent fuel pool water level measuring device according to claim 1, wherein the water level detector protective pipe is fixed to a wall or an upper floor of the spent fuel pool by a support material at a position higher than an upper surface of the weir.   2. The water level measuring device for a spent fuel pool according to claim 1, wherein the water level detector protective tube is housed on an outermost periphery of the spent fuel rack. 3. Each of the plurality of water level detectors includes a thermocouple,
The water level measuring device measures the water level of the spent fuel pool based on the temperature measured by the thermocouple,
2. The thermocouple according to claim 1, wherein in the state where the water level detector protection tube is housed in the spent fuel rack, the positions of the respective temperature measuring units are different from each other in the depth direction of the spent fuel pool. The used fuel pool water level measuring device. A plurality of the water level detector protective tubes,
A plurality of the water level detector protective tubes each store a plurality of the water level detectors,
Each of the plurality of water level detectors includes a thermocouple,
The water level measuring device measures the water level of the spent fuel pool based on the temperature measured by the thermocouple,
2. The thermocouple according to claim 1, wherein in the state where the water level detector protection tube is housed in the spent fuel rack, the positions of the respective temperature measuring units are different from each other in the depth direction of the spent fuel pool. The used fuel pool water level measuring device.   The water level measuring device for a spent fuel pool according to any one of claims 1 to 7, wherein the plurality of water level detectors are fixed to the water level detector protective tube by a plurality of plate-like members.

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