JP6578958B2 - Method and apparatus for storing radioactive waste - Google Patents

Description

  The present invention relates to a method and apparatus for storing radioactive waste.

  Radioactive waste such as fuel debris discharged from nuclear power plants at the time of an accident is stored in a reinforced concrete building in a metal container called a canister, for example, to remove decay heat It is cooled for a predetermined period.

  In addition, there exist patent document 1 and patent document 2 as what shows the general technical level relevant to the storage method and apparatus of the said radioactive waste, for example.

JP 2004-184390 A JP 2004-264162 A

  However, in any of the inventions disclosed in Patent Document 1 and Patent Document 2, the canister is simply stored in a concrete container, and only an abnormality is detected by detecting temperature or pressure. There was room for improvement in further improving reliability.

  On the other hand, in the radioactive waste, hydrogen may be generated during storage due to, for example, radiolysis of water. In particular, in the case of radioactive waste such as fuel debris, water may be added in the process of cooling or crushing, and depending on the water content, hydrogen is likely to be generated in the subsequent storage process. In general, when the hydrogen concentration reaches a specified value (for example, 4% by volume) or more, it enters the combustible region. Therefore, it is necessary to suppress the hydrogen concentration below the specified value. However, in the invention disclosed in Patent Document 1 and the invention disclosed in Patent Document 2, no consideration has been given to the hydrogen concentration inside the canister.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a radioactive waste storage method and apparatus capable of improving the reliability related to the storage of radioactive waste.

The present invention includes a waste enclosing step of enclosing radioactive waste in a canister;
A canister enclosing step in which the canister enclosing the radioactive waste in the waste enclosing step is encapsulated in a sealed monitoring container so that the internal pressure of the sealed monitoring container is a negative pressure;
A container storing step of storing the sealing monitoring container in which the canister is sealed in the canister sealing step in a shielding concrete room;
A cooling step of cooling and cooling the container for sealing monitoring stored in the shielding concrete room in the container storing step;
An internal pressure monitoring step of monitoring the internal pressure of the sealing monitoring vessel that is cooled by ventilation in the cooling step;
Leakage detection that detects the presence of leakage from the canister by sampling and analyzing the internal gas of the sealing monitoring container when the internal pressure of the sealing monitoring container monitored in the internal pressure monitoring process changes beyond a threshold value This relates to a method for storing radioactive waste that is performed in the process.

  In the radioactive waste storage method, in the waste sealing step, after the radioactive waste is heated in a state where the radioactive waste is put in from the opening of the canister, water is expelled from the inside of the canister. The canister may be welded so as to cover the opening with a lid member having a hydrogen / oxygen recombination catalyst and a water vapor absorbing material attached to the inner surface.

On the other hand, the present invention provides a canister for enclosing radioactive waste,
A hermetically sealed container that encloses the canister enclosing the radioactive waste so that the internal pressure is negative;
A shielded concrete room for storing the container for sealing monitoring;
A cooling device for ventilating and cooling the container for sealing monitoring stored in the shielding concrete room;
An internal pressure monitoring device for monitoring the internal pressure of the container for sealing monitoring that is cooled by ventilation with the cooling device;
Leakage detection that detects the presence or absence of leakage from the canister by sampling and analyzing the internal gas of the sealing monitoring container when the internal pressure of the sealing monitoring container monitored by the internal pressure monitoring device changes beyond a threshold value And a radioactive waste storage device equipped with a device.

In the radioactive waste storage device, by heating the radioactive waste put inside from the opening of the canister, a heater for expelling water from the inside of the canister;
And a lid member which is disposed so as to cover the opening with respect to the canister from which water is expelled from the inside by the heater and has a hydrogen / oxygen recombination catalyst and a water vapor absorbing material attached to the inner surface.

  The radioactive waste storage device may include a neutron absorber disposed inside the canister.

  The neutron absorber may be disposed so as to cover the inner wall surface of the canister.

  Further, the neutron absorbing material may extend radially from the inner wall surface of the canister and be arranged at intervals in the circumferential direction of the canister.

  According to the method and apparatus for storing radioactive waste of the present invention, it is possible to achieve an excellent effect that the reliability related to storage of radioactive waste can be improved.

It is a flowchart which shows each process performed in the Example of the storage method and apparatus of the radioactive waste of this invention. It is a flowchart which shows the detail in the internal pressure monitoring process performed in the Example of the radioactive waste storage method and apparatus of this invention, and the leak detection process. It is the schematic which shows the waste enclosure process in the Example of the storage method and apparatus of the radioactive waste of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic which shows the neutron absorber arrange | positioned inside the canister in the Example of the radioactive waste storage method and apparatus of this invention, Comprising: (A) is a neutron absorber so that the inner wall surface of a canister may be covered. FIG. 4B is a side sectional view and a plan sectional view showing an example in which a neutron absorbing material is disposed so as to project radially from the inner wall surface of the canister. It is the schematic which shows the canister enclosure process in the Example of the storage method and apparatus of the radioactive waste of this invention. It is the schematic which shows the container for sealing monitoring stored in the shielding concrete room in the Example of the storage method and apparatus of the radioactive waste of this invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  1 to 6 show an embodiment of a radioactive waste storage method and apparatus according to the present invention.

  In the case of the present embodiment, as shown in FIG. 1, the waste sealing process P1, the canister sealing process P2, the container storing process P3, the cooling process P4, the internal pressure monitoring process P5, and the leakage detection process P6 are performed. It has become.

  The waste enclosing step P1 is a step of enclosing a radioactive waste Rw such as fuel debris in the canister 1 (see FIG. 3). In the waste enclosing step P1, as shown in FIG. 3, the radioactive waste Rw is heated by a heater H in a state where the radioactive waste Rw is put through the opening 1a of the canister 1, whereby the canister 1 I try to expel water from the inside. Thereafter, a lid 4 having a hydrogen / oxygen recombination catalyst 2 and a water vapor absorbing material 3 attached to the inner surface is welded to the canister 1 so as to cover the opening 1a.

  Here, a neutron absorber 5 (see FIG. 4) is disposed inside the canister 1. The neutron absorber 5 can be arranged in a cylindrical shape so as to cover the inner wall surface of the canister 1, for example, as shown in FIG. Further, the neutron absorber 5 is constituted by a plate-like member, for example, as shown in FIG. 4B, projects radially inward from the inner wall surface of the canister 1, and extends in the circumferential direction of the canister 1. You may make it arrange | position at intervals. In addition, as the said neutron absorber 5, the sintered material which added the boron oxide to the aluminum alloy powder and heat-processed can be used, for example. 3, 5 and 6, the neutron absorbing material 5 shown in FIG. 4 (A) or 4 (B) is assumed to be disposed, and the neutron absorbing material 5 is not shown. ing.

  In the canister sealing step P2, the canister 1 in which the radioactive waste Rw is sealed in the waste sealing step P1 is placed in the sealing monitoring container 6 (see FIG. 5) so that the internal pressure of the sealing monitoring container 6 becomes negative. This is a sealing process. The sealing monitoring container 6 is interposed between a container body 6a in which the canister 1 is stored, a sealing lid 6b that covers an opening of the container body 6a, and the sealing lid 6b and the container body 6a. A gasket 6c and a fastening member 6e such as a bolt and a nut for attaching a sealing lid 6b to the flange portion 6d of the container body 6a are provided. The sealing monitoring container 6 is designed to make the internal pressure negative by sucking with a vacuum pump from a port not shown.

  The container storing process P3 is a process of storing the sealing monitoring container 6 in which the canister 1 is sealed in the canister sealing process P2 in the shielding concrete chamber 7 (see FIG. 6). As shown in FIG. 6, the shielding concrete chamber 7 is closed by a shielding lid 7a in a state where the sealing monitoring container 6 is stored.

  The cooling process P4 is a process in which the hermetic monitoring container 6 stored in the shielding concrete chamber 7 is cooled by ventilation in the container storing process P3. As shown in FIG. 6, the shielding concrete chamber 7 includes an air intake 8 a formed at the bottom thereof, and a flow passage 8 b through which air introduced from the intake 8 a is circulated to the outer periphery of the sealing monitoring container 6. And an air discharge port 8c formed in the upper part so as to lead out the air flowing through the flow passage 8b to the outside, thereby cooling the air through the hermetic monitoring container 6 stored in the shielding concrete chamber 7 A device 8 is configured. The cooling device 8 may have any configuration as long as it can cool the sealing monitoring container 6.

  The internal pressure monitoring step P5 is a step of monitoring the internal pressure 9p of the sealing monitoring container 6 that is ventilated and cooled in the cooling step P4. As shown in FIG. 6, a sampling port 9a is attached to the shielding lid 7a of the shielding concrete chamber 7, and a pressure detection tube 9b penetrating the sampling port 9a and the sealing lid 6b of the sealing monitoring container 6 is provided. A pressure gauge 9c is attached to the pressure detection tube 9b. Thereby, the internal pressure monitoring device 9 is configured to monitor the internal pressure 9p of the sealing monitoring container 6 that is cooled by ventilation by the cooling device 8.

  In the internal pressure monitoring process P5, an operation shown in step S1 described later in the flowchart of FIG. 2 is performed.

  In the leakage detection process P6, when the internal pressure 9p of the sealing monitoring container 6 monitored in the internal pressure monitoring process P5 changes beyond a threshold, the internal gas in the sealing monitoring container 6 is sampled and analyzed, This is a step of detecting the presence or absence of leakage from the canister 1. As shown in FIG. 6, the sampling tube 10a is branched from the middle portion of the pressure detection tube 9b, and an on-off valve 10b is provided in the middle portion of the sampling tube 10a, and the sealing monitoring detected by the pressure gauge 9c is provided. A controller 10d that outputs an open signal 10c to the on-off valve 10b based on the internal pressure 9p of the container 6 is provided. As a result, when the internal pressure 9p of the sealing monitoring container 6 monitored by the internal pressure monitoring device 9 changes beyond a threshold value, the internal gas in the sealing monitoring container 6 is sampled and analyzed, so that A leak detection device 10 that detects the presence or absence of a leak is configured.

  In the leak detection step P6, operations shown in steps S2 to S6 described later in the flowchart of FIG. 2 are performed.

  Next, the operation of the above embodiment will be described.

  First, in the waste sealing step P1, as shown in FIG. 3, when the radioactive waste Rw is heated by the heater H in a state where the radioactive waste Rw is put through the opening 1a of the canister 1, the inside of the canister 1 Water is expelled from. Thereafter, the lid 4 having the hydrogen / oxygen recombination catalyst 2 and the water vapor absorbing material 3 attached to the inner surface is welded to the canister 1 so as to cover the opening 1a.

  Here, as shown in FIG. 4 (A) or FIG. 4 (B), the canister 1 is provided with a neutron absorber 5 so that the fission chain reaction due to recriticality of the radioactive waste Rw occurs. Is prevented. As shown in FIG. 4A, when the neutron absorber 5 is disposed so as to cover the inner wall surface of the canister 1, the radioactive waste Rw has a high heat generation, and the neutron absorber 5 becomes a heat insulator. When the internal temperature rise of the canister 1 is concerned, the neutron absorbing material 5 projects radially inward from the inner wall surface of the canister 1 and extends in the circumferential direction of the canister 1 as shown in FIG. It is preferable to dispose them at equal intervals, because an increase in the internal temperature of the canister 1 is suppressed. However, the neutron absorbers 5 do not necessarily need to be arranged at regular intervals in the circumferential direction of the canister 1, and the intervals may be appropriately selected.

  Subsequently, in the canister enclosing step P2, the canister 1 in which the radioactive waste Rw is encapsulated in the waste enclosing step P1 is applied to the sealing monitoring vessel 6 so that the internal pressure of the sealing monitoring vessel 6 is negative as shown in FIG. It is sealed so that it becomes pressure. After the canister 1 is stored in the container body 6a, the seal monitoring container 6 is covered with a sealing lid 6b so that the opening of the container body 6a is kept airtight by the gasket 6c. The canister 1 is sealed by tightening the sealing lid 6b with a fastening member 6e such as a bolt and a nut against the flange portion 6d of the container body 6a while suctioning from a port not shown.

  Next, in the container storing step P3, the sealing monitoring container 6 in which the canister 1 is sealed in the canister sealing step P2 is stored in the shielding concrete chamber 7 as shown in FIG. The shielding concrete chamber 7 is closed by a shielding lid 7a in a state in which the sealing monitoring container 6 is stored.

  Thereafter, in the cooling process P4, the sealing monitoring container 6 stored in the shielding concrete chamber 7 in the container storing process P3 is ventilated and cooled by the cooling device 8. As shown in FIG. 6, the inside of the shielding concrete chamber 7 is such that air introduced from an air intake port 8 a formed at the bottom thereof flows through the flow passage 8 b and is led out from the discharge port 8 c to the outside. Ventilated and cooled.

  In the internal pressure monitoring step P5, the internal pressure 9p of the sealing monitoring container 6 that is ventilated and cooled in the cooling step P4 is monitored. As shown in FIG. 6, the internal pressure 9p of the sealing monitoring container 6 is detected by a pressure gauge 9c attached to a pressure detection tube 9b constituting the internal pressure monitoring device 9, and is input to the controller 10d. Then, it is determined whether or not the internal pressure 9p of the sealing monitoring container 6 has changed beyond a threshold value (see step S1 in FIG. 2).

  Further, in the leak detection step P6, when the internal pressure 9p of the sealing monitoring container 6 monitored in the internal pressure monitoring process P5 changes beyond a threshold, the internal gas in the sealing monitoring container 6 is sampled and analyzed. (See step S2 in FIG. 2), the presence or absence of leakage from the canister 1 is detected (see step S3 in FIG. 2). Sampling of the internal gas in the sealing monitoring container 6 is performed from the sampling pipe 10a by opening the on-off valve 10b when an open signal 10c is output from the controller 10d constituting the leak detection device 10 to the on-off valve 10b. Is called.

  When there is a leak from the canister 1 as a result of sampling and analyzing the internal gas of the sealing monitoring container 6, the canister 1 having a leak is identified and shown by the confinement and appearance inspection of each canister 1. It is stored in a non-overpack (see step S4 in FIG. 2). After the decontamination, the healthy canister 1 is stored again in the sealing monitoring container 6 (see step S5 in FIG. 2).

  If there is no leakage from the canister 1 as a result of sampling and analyzing the internal gas of the sealing monitoring container 6, the sealing monitoring container 6 is replaced after confirming the maintenance of the sealing function by confinement / visual inspection of each canister 1. Is performed (see step S6 in FIG. 2).

  As a result, in this embodiment, since the internal pressure 9p of the sealing monitoring container 6 is monitored in a state where the sealing monitoring container 6 in which the canister 1 is sealed is stored in the shielding concrete chamber 7, the canister 1 must Even if the internal gas leaks, it can be confined in the hermetic monitoring container 6, and the reliability can be further enhanced as compared with the inventions disclosed in Patent Document 1 and Patent Document 2. Furthermore, adhesion of moisture, sea salt, rust, and other particles to the canister 1 can be prevented, and corrosion of the canister 1 can be prevented to maintain soundness.

  On the other hand, the radioactive waste may generate hydrogen during storage due to, for example, radiolysis of water. In this embodiment, water is expelled from the inside of the canister 1 due to heating by the heater H. Generation of hydrogen due to radiolysis of water is suppressed. Further, since the hydrogen / oxygen recombination catalyst 2 and the water vapor absorbing material 3 are attached to the inner surface of the lid 4 covering the opening 1a of the canister 1, hydrogen is not removed completely due to radiation decomposition of water. Even if generated, the hydrogen is recombined with oxygen by the hydrogen / oxygen recombination catalyst 2 to become water vapor, and is absorbed by the water vapor absorbent 3. As a result, the hydrogen concentration inside the canister 1 is suppressed to less than the specified value, and the combustible region is prevented from entering.

  Thus, it is possible to improve the reliability related to the storage of the radioactive waste Rw.

  In the case of the storage method of the present embodiment, the canister 1 is heated by heating the radioactive waste Rw with the radioactive waste Rw put in the opening 1a of the canister 1 in the waste enclosure step P1. After the water is expelled from the inside, a lid 4 having a hydrogen / oxygen recombination catalyst 2 and a water vapor absorbing material 3 attached to the inner surface is welded to the canister 1 so as to cover the opening 1a. With this configuration, the radioactive waste may generate hydrogen during storage due to radiolysis of water, etc., but since water is expelled from the inside of the canister 1 by heating, the radiolysis of water is performed. The generation of hydrogen due to the above is suppressed. Further, even if hydrogen is generated due to radiolysis of water that has not been completely expelled, the hydrogen / oxygen recombination catalyst 2 attached to the inner surface of the lid member 4 covering the opening 1a of the canister 1 causes the hydrogen Is recombined with oxygen by the hydrogen / oxygen recombination catalyst 2 to form water vapor, which is absorbed by the water vapor absorber 3. As a result, the hydrogen concentration inside the canister 1 is suppressed to less than the specified value, and the combustible region is prevented from entering.

  Further, in the storage device of the present embodiment, a canister 1 for enclosing the radioactive waste Rw, and a sealing monitoring container 6 for enclosing the canister 1 in which the radioactive waste Rw is encapsulated so that the internal pressure 9p is negative. , A shielding concrete chamber 7 for storing the sealing monitoring container 6, a cooling device 8 for cooling and cooling the sealing monitoring container 6 stored in the shielding concrete chamber 7, and a sealing monitoring for ventilation cooling by the cooling device 8. When the internal pressure 9p for monitoring the internal pressure 9p of the container 6 for monitoring and the internal pressure 9p of the container 6 for sealing monitoring monitored by the internal pressure monitoring apparatus 9 changes beyond a threshold value, the internal gas of the container 6 for sealing monitoring is changed. A leak detection device 10 that detects the presence or absence of leak from the canister 1 by sampling and analyzing is provided. If comprised in this way, the reliability improvement regarding storage of radioactive waste Rw can be aimed at.

  In the case of the storage device of the present embodiment, the heater H for expelling water from the inside of the canister 1 by heating the radioactive waste Rw put inside from the opening 1a of the canister 1; A canister 1 from which water is expelled from the inside by a heater H is provided so as to cover the opening 1a, and a hydrogen / oxygen recombination catalyst 2 and a water vapor absorbing material 3 are attached to the inner surface of the lid 4. ing. With this configuration, the radioactive waste may generate hydrogen during storage due to radiolysis of water or the like. However, since water is expelled from the inside of the canister 1 by heating by the heater H, Generation of hydrogen due to radiolysis of the gas is suppressed. Further, since the hydrogen / oxygen recombination catalyst 2 and the water vapor absorbing material 3 are attached to the inner surface of the lid 4 covering the opening 1a of the canister 1, hydrogen is not removed completely due to radiation decomposition of water. Even if generated, the hydrogen is recombined with oxygen by the hydrogen / oxygen recombination catalyst 2 to become water vapor, and is absorbed by the water vapor absorbent 3. As a result, the hydrogen concentration inside the canister 1 is suppressed to less than the specified value, and the combustible region is prevented from entering.

  In the case of the storage device of this embodiment, a neutron absorber 5 is provided inside the canister 1. If comprised in this way, the fission chain reaction by the recriticality of radioactive waste Rw is prevented.

  Further, in the case of the storage device of this embodiment, the neutron absorber 5 is disposed so as to cover the inner wall surface of the canister 1. Even if comprised in this way, the fission chain reaction by the recriticality of the radioactive waste Rw is prevented.

  Further, in the case of the storage device of the present embodiment, the neutron absorbing material 5 projects radially from the inner wall surface of the canister 1 and is disposed at intervals in the circumferential direction of the canister 1. Even if comprised in this way, when the nuclear fission chain reaction by the recriticality of the radioactive waste Rw is prevented, and furthermore, the heat generation of the radioactive waste Rw is high and the internal temperature of the canister 1 is concerned, the canister 1 The neutron absorber 5 that protrudes in the radial direction from the inner wall surface of 1 and is disposed at intervals in the circumferential direction of the canister 1 is effective in suppressing an increase in the internal temperature of the canister 1.

  In addition, the radioactive waste storage method and apparatus of the present invention are not limited to the above-described embodiments, and various changes can be made without departing from the scope of the present invention.

1 Canister 1a Opening 2 Hydrogen / Oxygen Recombination Catalyst 3 Water Vapor Absorbing Material 4 Lid Material 5 Neutron Absorbing Material 6 Seal Monitoring Container 7 Shielding Concrete Room 8 Cooling Device 9 Internal Pressure Monitoring Device 9p Internal Pressure 10 Leakage Detection Device H Heater P1 Waste Enclosing process P2 Canister enclosing process P3 Container storage process P4 Cooling process P5 Internal pressure monitoring process P6 Leak detection process Rw Radioactive waste

Claims (7)

Waste enclosing process for enclosing radioactive waste in a canister;
A canister enclosing step in which the canister enclosing the radioactive waste in the waste enclosing step is encapsulated in a sealed monitoring container so that the internal pressure of the sealed monitoring container is a negative pressure;
A container storing step of storing the sealing monitoring container in which the canister is sealed in the canister sealing step in a shielding concrete room;
A cooling step of cooling and cooling the container for sealing monitoring stored in the shielding concrete room in the container storing step;
An internal pressure monitoring step of monitoring the internal pressure of the sealing monitoring vessel that is cooled by ventilation in the cooling step;
Leakage detection that detects the presence of leakage from the canister by sampling and analyzing the internal gas of the sealing monitoring container when the internal pressure of the sealing monitoring container monitored in the internal pressure monitoring process changes beyond a threshold value A method of storing radioactive waste that includes the following steps:   In the waste sealing step, the radioactive waste is heated in a state in which the radioactive waste is put through the opening of the canister to expel water from the inside of the canister, and then the canister is supplied with hydrogen / oxygen. The method for storing radioactive waste according to claim 1, wherein a lid member attached to the inner surface with a recombination catalyst and a water vapor absorbing material is welded so as to cover the opening. A canister for enclosing radioactive waste;
A hermetically sealed container that encloses the canister enclosing the radioactive waste so that the internal pressure is negative;
A shielded concrete room for storing the container for sealing monitoring;
A cooling device for ventilating and cooling the container for sealing monitoring stored in the shielding concrete room;
An internal pressure monitoring device for monitoring the internal pressure of the container for sealing monitoring that is cooled by ventilation with the cooling device;
Leakage detection that detects the presence or absence of leakage from the canister by sampling and analyzing the internal gas of the sealing monitoring container when the internal pressure of the sealing monitoring container monitored by the internal pressure monitoring device changes beyond a threshold value A radioactive waste storage device comprising: A heater for expelling water from the inside of the canister by heating the radioactive waste put inside from the opening of the canister;
A lid member disposed so as to cover the opening with respect to the canister from which water is expelled from the inside by the heater and having a hydrogen / oxygen recombination catalyst and a water vapor absorbing material attached to the inner surface. Radioactive waste storage equipment.   The radioactive waste storage device according to claim 3 or 4, further comprising a neutron absorber disposed inside the canister.   The radioactive waste storage device according to claim 5, wherein the neutron absorber is disposed so as to cover an inner wall surface of the canister.   The radioactive waste storage device according to claim 5, wherein the neutron absorbing material projects radially from an inner wall surface of the canister and is disposed at intervals in a circumferential direction of the canister.

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