JP2014052258A - Radiation measurement apparatus of nuclear reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a state of a fused material in a reactor containment vessel with high accuracy in a radiation measurement apparatus of a nuclear reactor.SOLUTION: A reactor containment vessel 11 is provided with detectors 40, 50 that are mountably supported by its work hole 11a. As the detectors 40, 50, provided are: detector bodies 41, 51 formed by a radiation shield material; a plurality of radiation penetration holes 41c, 51c formed in lower parts of the detector bodies 41, 51; and a plurality of radiation detectors 42, 54 provided in the lower parts of the detector bodies 41, 51 facing the plurality of radiation penetration holes 41c, 51c.

Description

  The present invention relates to a nuclear radiation measurement apparatus for quickly confirming the state of a melt falling from a core when a severe accident occurs in a nuclear power plant.

  For example, a nuclear power plant having a pressurized water reactor (PWR) uses light water as a reactor coolant and a neutron moderator to produce high-temperature and high-pressure water that does not boil throughout the reactor core. Water is sent to a steam generator to generate steam by heat exchange, and this steam is sent to a turbine generator to generate electricity. And a steam generator transmits the heat | fever of the high temperature / high pressure primary cooling water from a nuclear reactor to secondary cooling water, and generates water vapor | steam with secondary cooling water.

  In such a nuclear power plant, the reactor containment vessel is erected on a solid ground such as a rock, and a plurality of compartments are partitioned inside by reinforced concrete. A nuclear reactor is suspended and supported at the center of the concrete structure that defines the compartment, and a cavity is defined below the reactor. This nuclear reactor is configured such that a predetermined number of fuel assemblies in a lattice shape formed by a plurality of fuel rods and a predetermined number of control rods are stored in a reactor pressure vessel.

  When a loss of coolant accident (LOCA) or a transient event (transient) occurs in a nuclear power plant configured in this way, an emergency core cooling device is activated to cool the core inside the reactor vessel. The heat generated in is sufficiently removed. However, if this emergency core cooling device fails, the core cannot be cooled, the core inside the reactor vessel is melted, and molten material such as molten fuel breaks the reactor vessel and penetrates the lower part. Fall into the cavity of the containment vessel. In general, in preparation for such an accident, when the melt in the core flows out of the reactor vessel, the molten melt is received in the cavity and cooled with cooling water to ensure safety. .

  As a technique for monitoring state information in a nuclear reactor, for example, there is one described in Patent Document 1 below.

Japanese Patent Laid-Open No. 10-039083

  When the nuclear reactor accident mentioned above occurs and the core melt flows out of the reactor vessel, it is necessary to know at an early stage and accurately what position the melted out flow is and in what state. .

  The present invention solves the above-described problems, and an object of the present invention is to provide a nuclear radiation measurement apparatus that can detect the state of a melt in a reactor containment vessel with high accuracy.

  In order to achieve the above object, a radiation measurement apparatus for a reactor according to the present invention includes a detector main body formed of a radiation shielding material and capable of being supported and installed in a work hole of a reactor containment vessel, and a front portion of the detector main body And a plurality of radiation detectors provided inside the detector body so as to be opposed to the plurality of radiation through holes.

  Therefore, since the detector main body is supported by the work hole of the reactor containment vessel and a plurality of radiation through holes are provided for the plurality of radiation detectors, when there is a melt in the reactor containment vessel, Radiation can enter and detect each radiation detector through each radiation through hole, and the state of the melt in the reactor containment vessel can be detected with high accuracy based on the detection results of the plurality of radiation detectors. .

  In the nuclear radiation measurement apparatus of the present invention, a map forming apparatus is provided that forms a radiation concentration map in the reactor containment vessel based on detection results detected by the plurality of radiation detectors.

  Therefore, the map forming device can properly grasp the state of the melt in the reactor containment vessel by forming the radiation concentration map in the reactor containment vessel based on the detection result detected by each radiation detector. Can do.

  In the radiation measurement apparatus for a reactor according to the present invention, a support rod that is inserted into a work hole of the reactor containment vessel and is supported so as to be movable in a horizontal direction, and a first moving device that can move the support rod are provided. The detector body is supported by the tip of the support rod.

  Therefore, since the detector main body can be moved in the horizontal direction via the support rod by the first moving device, the plurality of radiation detectors can detect radiation from the melt from a plurality of different positions, and The state of the melt in the furnace containment vessel can be grasped three-dimensionally.

  In the nuclear radiation measurement apparatus of the present invention, a moving body provided at the tip of the support rod and supported to be movable in the vertical direction, and a second moving apparatus capable of moving the moving body are provided, The detector main body is supported by the moving body.

  Therefore, since the detector main body can be moved in the vertical direction via the moving body by the second moving device, the detector main body can be moved to a desired position to perform the detection work.

  In the nuclear radiation measurement apparatus of the present invention, the detector main body has a spherical front part, and the plurality of radiation through holes are formed along a radiation direction.

  Therefore, radiation in a three-dimensional direction can be measured by a plurality of radiation detectors, and workability can be improved.

  According to the nuclear radiation measurement apparatus of the present invention, a detector main body formed of a radiation shielding material and capable of being supported and installed in a work hole of a reactor containment vessel, and a plurality of radiations formed at the front of the detector main body Since the through hole and the plurality of radiation detectors provided in the detector main body so as to face the plurality of through holes are provided, the state of the melt in the reactor containment vessel can be detected with high accuracy. .

FIG. 1 is a schematic configuration diagram illustrating a nuclear power plant according to a first embodiment. FIG. 2 is a schematic diagram illustrating a radiation measurement apparatus for a nuclear reactor according to Embodiment 1 of the present invention. FIG. 3 is a front view of the nuclear radiation measurement apparatus according to the first embodiment. FIG. 4 is a cross-sectional view of a detector in the nuclear radiation measurement apparatus according to the first embodiment. FIG. 5 is a cross-sectional view of a modification of the detector in the nuclear radiation measurement apparatus according to the first embodiment. FIG. 6 is a schematic diagram illustrating a nuclear radiation measurement apparatus according to Embodiment 2 of the present invention.

  Exemplary embodiments of a radiation measuring apparatus for a reactor according to the present invention will be described below in detail with reference to the accompanying drawings. In addition, this invention is not limited by this Example, Moreover, when there exists multiple Example, what comprises combining each Example is also included.

  1 is a schematic configuration diagram illustrating a nuclear power plant according to a first embodiment, FIG. 2 is a schematic diagram illustrating a radiation measurement apparatus for a nuclear reactor according to a first embodiment of the present invention, and FIG. 3 is a nuclear reactor according to the first embodiment. FIG. 4 is a cross-sectional view of a detector in the nuclear radiation measurement apparatus of the reactor of the first embodiment, and FIG. 5 is a modification of the detector in the nuclear radiation measurement apparatus of the first embodiment. It is sectional drawing.

  The nuclear reactor of Example 1 uses light water as a reactor coolant and a neutron moderator, boils this light water in the core to generate steam, and sends this steam directly to a turbine generator to generate electricity. It is a nuclear reactor (BWR: Boiling Water Reactor).

  In the nuclear power plant having the boiling water reactor according to the first embodiment, as shown in FIG. 1, the reactor containment vessel 11 stores therein a boiling water reactor 12, and this boiling water reactor. 12, a plurality of cooling water pipes 13 and a recirculation pump 14 are provided. The boiling water reactor 12 has a large number of fuels 15 and control rods 16 disposed therein, and a steam / water separator 17 disposed above the fuel 15. Accordingly, light water is heated and boiled as cooling water by the fuel 15 in the boiling water reactor 12, and only the steam is separated by the steam separator 17.

  The boiling water reactor 12 is connected to a steam turbine 19 via a cooling water pipe 18, and a generator 20 is connected to the steam turbine 19. The steam turbine 19 has a condenser 21, to which a water intake pipe 22 and a drain pipe 23 for supplying and discharging cooling water (for example, seawater) are connected. 22 has the circulating water pump 24, and the other end part is arrange | positioned in the sea with the drain pipe 23. FIG. The condenser 21 is connected to the boiling water reactor 12 through a cooling water pipe 25, and a water supply pump 26 is provided in the cooling water pipe 25.

  Therefore, the steam generated in the boiling water reactor 12 is sent to the steam turbine 19 through the cooling water pipe 18, and the steam turbine 19 is driven by this steam to generate power by the generator 20. The steam that has driven the steam turbine 19 is cooled using seawater in the condenser 21 to become condensed water, and is returned to the boiling water reactor 12 through the cooling water pipe 25.

  By the way, when a coolant loss accident or the like occurs, the emergency core cooling device operates to cool the core of the boiling water reactor 12, but if this emergency core cooling device fails, the core cannot be cooled. Then, the melted fuel (debris) A such as fuel breaks the reactor vessel, passes through the lower part, and falls to the reactor containment vessel 11. In this case, the melt A that has fallen into the reactor containment vessel 11 is cooled by cooling water to ensure safety, but it is possible to grasp at an early stage where and what state the melt has flowed out. There is a need to.

  Therefore, in the first embodiment, as shown in FIG. 2, the state of the melt A in the reactor containment vessel 11 can be detected by the radiation measuring device 31. This radiation measuring device 31 can be attached to the nuclear reactor containment vessel 11, and can detect the position and amount of the melt A inside by inserting a detector from the work hole 11a formed in the side portion. .

  In the radiation measuring apparatus 31, as shown in FIG. 3, the support member 32 can be fixed by fitting into the work hole 11 a of the reactor containment vessel 11, and the support rod 33 penetrates the support member 32. It is supported movably. The support rod 33 penetrates from the outside to the inside of the reactor containment vessel 11 and is disposed along the horizontal direction. The first moving device 34 is, for example, a rack and pinion mechanism, and is installed in a flange portion 11b formed outside the reactor containment vessel 11. The first moving device 34 is moved along the longitudinal direction (horizontal direction) of the support rod 33. Can be moved back and forth. The support rod 33 and the first moving device 34 may be a telescopic mechanism.

  The second moving device 35 is, for example, a winch and is installed in the flange portion 11b of the reactor containment vessel 11, and a plurality of traction cables (moving bodies) 36 penetrate the support member 32 and pass through the nuclear reactor. It is pulled out inside the storage container 11. The traction cable 36 is disposed along the support rod 33, and is disposed below by a guide roller 37 provided at the distal end portion of the support rod 33, and a traction member 39 is connected via a suspension member 38. Yes. The pulling member 39 has a detector 40 detachably attached to the lower part thereof.

  Therefore, when the first moving device 34 is driven, the support rod 33 can be moved along the horizontal direction, and the detector 40 attached to the tip can be moved along the radial direction in the reactor containment vessel 11. . Further, when the second moving device 35 is driven, the pulling cable 36 can be pulled out and wound up, and the detector 40 can be moved in the vertical direction (vertical direction) in the reactor containment vessel 11.

  The detector 40 detects gamma rays (γ rays) and neutron rays (neutrons) as radiation. In this detector 40, as shown in FIG. 4, the detection basic body 41 has a cylindrical shape having a hollow portion 41a and is formed of a radiation shielding material such as lead or concrete. In the detector body 41, a plurality of radiation detectors 42 are fixed to the hollow portion 41a. The radiation detectors 42 can detect gamma rays or neutron rays, and are arranged in the hollow portion 41a of the detector main body 41 at a predetermined interval along the horizontal plane direction and fixed to the bottom portion 41b. The detector main body 41 is formed with a plurality of radiation through holes 41c facing the radiation detectors 42 at the bottom 41b, that is, the front in the detection direction.

  Further, the plurality of radiation detectors 42 are connected to the signal cable 43 and are disposed along the support rod 33 through the detection basic body 41, as shown in FIG. 3, to the outside of the reactor containment vessel 11. It has been extended. The control device 44 is provided in a control room or the like provided outside the reactor containment vessel 11, to which signal cables 43 from a plurality of radiation detectors 42 are connected, and detection results are input. The control device 44 functions as a map forming device that forms a radiation concentration map in the reactor containment vessel 11 based on the detection result of each radiation detector 42. The control device 44 is connected to a monitor 45 and can display the detection result of each radiation detector 42 and the radiation concentration map in the reactor containment vessel 11.

  The detector 40 has a hollow cylindrical shape, and a plurality of radiation detectors 42 are arranged at predetermined intervals along the horizontal direction. However, the present invention is not limited to this configuration. For example, as shown in FIG. 5, in the detector 50, the detector main body 51 has a hemispherical shape having a hollow portion 51 a, and includes an outer shield 52 and an inner shield 53. In this case, the outer shield 52 is made of, for example, lead or concrete, and the inner shield 53 is made of polyethylene containing boric acid or the like. In the detector main body 51, a plurality of radiation detectors 54 are fixed to a hollow portion 51a. The radiation detector 54 can detect gamma rays or neutron rays, and a plurality of the radiation detectors 54 are arranged in the hollow portion 51a of the detector main body 51 at a predetermined interval along the spherical direction, and the spherical portion 51b (inner shield 53). It is fixed to. The detector main body 51 has a plurality of radiation through-holes 51c facing the radiation detectors 54 in the spherical surface portion 51b, that is, the front portion in the detection direction.

The detectors 40 and 50 measure gamma rays and neutron rays generated from the melt A falling in the reactor containment vessel 11. As a detector for measuring γ-rays, for example, measurement by a passive γ method is possible, and a detector such as a germanium semiconductor detector or a NaI scintillator can be used. The detector measures the neutron beam, for example, those capable of measurement by passive neutron method, the He-3 counters, BF ₃ counters, and counters, such as fission counter tube, a detector such as a liquid scintillator Can be used.

  In this case, the detectors 40 and 50 may be configured by configuring the plurality of radiation detectors 42 and 54 from γ-ray detectors or from neutron beam detectors. Further, as the plurality of radiation detectors 42 and 54, both a γ-ray detector and a neutron beam detector may be arranged.

  The control device 44 is composed of a numerical operation device such as a computer, and has, for example, a γ-ray data processing unit, a neutron beam data processing unit, a radioactivity concentration calculation unit, a radiation concentration map calculation unit, and a storage unit. doing. The γ-ray data processing unit calculates the radiation concentration of the γ-ray emitting nuclide such as Cs-137 by processing the data received from the detectors 40 and 50. More specifically, the area of the peak corresponding to the γ-ray emitting nuclide such as Cs-137 is obtained from the spectrum of γ-rays output from the detectors 40 and 50, and the radioactivity concentration of the γ-emitting nuclide such as Cs-137 is obtained from this area. Is converted. The neutron beam data processing unit calculates the radiation concentration of neutron emitting nuclides such as Cm-244 by processing the data received from the detectors 40 and 50. More specifically, the radioactivity concentration of a neutron emitting nuclide such as Cm-244 is converted from the neutron beam count value output by the detectors 40 and 50.

  The radiation concentration map calculation unit calculates the two-dimensional or three-dimensional radiation in the reactor containment vessel 11 based on the radioactive concentration of the γ-ray emitting nuclide such as Cs-137 or the radiation concentration of the neutron emitting nuclide such as Cm-244. Create a density map. In this case, a three-dimensional radiation concentration map can be created by moving the detectors 40 and 50 in the horizontal direction and measuring radiation from at least two different positions. The storage unit stores the created radiation density map as time data. The monitor 45 can display the radiation density map obtained by the control device 44.

  Therefore, as shown in FIGS. 2 and 3, when the core in the boiling water reactor 12 is melted and the melt A such as the molten fuel breaks the reactor vessel and falls into the reactor containment vessel 11, The operator detects the state of the melt A in the reactor containment vessel 11 using the radiation measuring device 31. First, the worker attaches the radiation measuring device 31 to the work hole 11 a of the reactor containment vessel 11. Next, the operator drives the first moving device 34 and moves the support rod 33 along the horizontal direction, thereby moving the detector 40 along the radial direction in the reactor containment vessel 11. Stop at the horizontal position. Further, the worker drives the second moving device 35 and pulls out the traction cable 36, thereby moving the detector 40 along the vertical direction in the reactor containment vessel 11 and stops at a predetermined horizontal position.

  Subsequently, the worker operates the control device 44 and starts radiation measurement by the detector 40 (50). That is, gamma rays and neutron rays are emitted as radiation from the melt A, and since this radiation has a straight traveling property, it enters from each radiation through hole 41c of the detection basic body 41, and each radiation detector. 42 can detect this radiation. Then, the detection result by each radiation detector 42 is sent to the control device 44 via the signal cable 43. The control device 44 calculates the radioactivity concentration by processing the data received from the detector 40.

  When the first measurement using the radiation measuring device 31 is completed, the operator drives the first moving device 34 and moves the support rod 33 along the horizontal direction, thereby moving the detector 40 into the reactor containment vessel. It moves along the radial direction in 11 and stops at a horizontal position different from the previous time. Here, the worker again calculates the radioactivity concentration by processing the data received from the detector 40. In this case, each of the moving devices 34 and 35 has a position sensor that detects the moving position of the support rod 33 and the pulling amount of the traction cable 36, and the control device 44 detects the detector based on the detection result of the position sensor. 40 positions can be grasped.

  Then, the control device 44 creates a three-dimensional radiation concentration map based on the radioactivity concentrations at two different positions. By displaying the created radiation concentration map on the monitor 45, the operator can grasp where the melt A that has fallen into the reactor containment vessel 11 is, and how much is present. .

  As described above, in the reactor radiation measuring apparatus according to the first embodiment, the detectors 40 and 50 that can be supported in the working hole 11a of the reactor containment vessel 11 are provided, and the radiation shielding material is used as the detectors 40 and 50. Detector bodies 41, 51 formed by the above, a plurality of radiation through holes 41c, 51c formed in the lower part of the detector bodies 41, 51, and a plurality of radiation through holes 41c, in the lower part of the detector bodies 41, 51, A plurality of radiation detectors 42 and 54 provided to face 51c are provided.

  Therefore, if there is a melt A in the reactor containment vessel 11, the radiation from the melt A can enter and detect the radiation detectors 42 and 54 through the radiation through holes 41c and 51c. Based on the detection results of the radiation detectors 42 and 54, the state of the melt A in the reactor containment vessel 11 can be detected with high accuracy.

  In the nuclear reactor radiation measuring apparatus according to the first embodiment, a control device 44 is provided as a map forming apparatus that forms a radiation concentration map in the reactor containment vessel 11 based on detection results detected by the plurality of radiation detectors 42 and 54. ing. Therefore, the control device 44 forms a radiation concentration map in the reactor containment vessel 11 and displays it on the monitor 45, so that the worker properly grasps the state of the melt A in the reactor containment vessel 11. be able to.

  In the nuclear radiation measurement apparatus according to the first embodiment, the support member 32 supported by the work hole 11a of the reactor containment vessel 11, the support rod 33 supported by the support member so as to be movable in the horizontal direction, and the support rod The first moving device 34 capable of moving 33 is provided, and the detectors 40 and 50 are supported on the tip of the support rod 33. Accordingly, since the detectors 40 and 50 can be moved in the horizontal direction via the support rod 33 by the first moving device 34, the plurality of radiation detectors 42 and 54 can emit radiation from the melt A from a plurality of different positions. And the state of the melt in the reactor containment vessel 11 can be grasped three-dimensionally.

  In the radiation measurement apparatus for a nuclear reactor according to the first embodiment, a traction cable 36 is disposed along the support rod 33, and the traction cable 36 can be pulled by the second moving device. , 50 are connected. Accordingly, since the detectors 40 and 50 can be moved in the vertical direction by the second moving device 35 via the traction cable 36, the detectors 40 and 50 can be moved to desired positions to perform detection work.

  In the nuclear reactor radiation measurement apparatus according to the first embodiment, the detector main body 50 has a hemispherical shape, and a plurality of radiation through holes 51c are formed along the radiation direction. Therefore, radiation in a three-dimensional direction can be measured by the plurality of radiation detectors 54, and workability can be improved.

  FIG. 6 is a schematic diagram illustrating a nuclear radiation measurement apparatus according to Embodiment 2 of the present invention. In addition, the same code | symbol is attached | subjected to the member which has the function similar to the Example mentioned above, and detailed description is abbreviate | omitted.

  In the second embodiment, as shown in FIG. 6, the state of the melt A in the reactor containment vessel 11 can be detected by the radiation measuring device 61. This radiation measuring device 61 can be attached to the reactor containment vessel 11 and can detect the position and amount of the melt A inside by inserting a detector from a work hole 11a formed in the side portion. .

  The radiation measuring device 61 includes a support member 62, a fixing flange 63, and a detector 64. The support member 62 can be fitted into the work hole 11 a of the reactor containment vessel 11 from the outside, and is positioned by fixing the integrally formed fixing flange 63 to the reactor containment vessel 11.

  The detector 64 detects gamma rays (γ rays) or neutron rays (neutrons) as radiation, and the basic structure is the same as the detector 50 of the first embodiment. That is, a plurality of radiation detectors are arranged in the hollow portion of the hemispherical detector main body, and a plurality of radiation through holes are formed in the spherical portion so as to face each radiation detector.

  Therefore, when the core in the boiling water reactor 12 is melted and the melt A such as the melted fuel breaks the reactor vessel and falls into the reactor containment vessel 11, the operator uses the radiation measuring device 61. The state of the melt A in the reactor containment vessel 11 is detected. First, the worker attaches the radiation measuring device 61 to the work hole 11 a of the reactor containment vessel 11. Next, the worker operates a control device (not shown) and starts radiation measurement by the detector 64. In this case, for example, the radioactivity concentration at two different positions can be detected by allowing the detector 64 to move (rotate) vertically or horizontally. Then, the control device creates a three-dimensional radiation concentration map based on the radioactivity concentration at two different positions and displays it on the monitor, so that the position of the melt A that has fallen into the reactor containment vessel 11 is displayed. Or how much is there.

  As described above, in the reactor radiation measuring apparatus according to the second embodiment, the detector 64 that can be mounted in the work hole 11a of the reactor containment vessel 11 is provided. Therefore, if there is a melt A in the reactor containment vessel 11, the detector 64 can detect the radiation from the melt A, and the state of the melt A in the reactor containment vessel 11 can be accurately determined. Can be detected.

  In the above-described embodiments, the detector has a hollow cylindrical shape or a hollow hemispherical shape, but is not limited to this shape, and may be a cubic shape or a spherical shape.

  In addition, the reactor radiation measurement apparatus of the present invention has a detector for measuring radiation, but may also be equipped with a reflector, camera, thermometer, gas concentration meter, water sampling device, etc. Good.

DESCRIPTION OF SYMBOLS 11 Reactor containment vessel 12 Boiling water reactor 19 Steam turbine 20 Generator 31, 61 Radiation measuring device 32, 62 Support member 33 Support rod 34 First moving device 35 Second moving device 36 Towing cable (moving body)
39 Pulling member 40, 50, 64 Detector 41, 51 Detector main body 41c, 51c Radiation through hole 42, 54 Radiation detector

Claims (5)

A detector body that is formed of a radiation shielding material and can be supported and installed in the work hole of the reactor containment vessel;
A plurality of radiation through holes formed in a front portion of the detector body;
A plurality of radiation detectors provided facing the plurality of radiation through holes in the detector body;
A radiation measurement apparatus for a nuclear reactor characterized by comprising:   The reactor radiation measurement apparatus according to claim 1, further comprising a map forming device that forms a radiation concentration map in the reactor containment vessel based on detection results detected by the plurality of radiation detectors.   A support rod that is inserted into the work hole of the reactor containment vessel and is supported so as to be movable in the horizontal direction, and a first moving device that can move the support rod are provided, and the detector body includes the support rod The reactor radiation measurement apparatus according to claim 1, wherein the radiation measurement apparatus is supported by a tip portion of the reactor.   A moving body provided at the tip of the support rod and supported to be movable in the vertical direction and a second moving device capable of moving the moving body are provided, and the detector body is supported by the moving body. The radiation measurement apparatus for a nuclear reactor according to claim 3, wherein:   5. The nuclear reactor radiation according to claim 1, wherein a front portion of the detector body has a spherical shape, and the plurality of radiation through holes are formed along a radial direction. 6. Measuring device.

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