Dryer and method for a radioactive material storage container

Abstract

To provide a device and method for drying a radioactive substance storage container, which allow for minimizing an increase in device size by simplifying a structure.SOLUTION: A drying device for a radioactive substance storage container provided herein comprises a discharge line for discharging gas inside the radioactive substance storage container, a dry vacuum pump provided in the discharge line, an inert gas supply line for supplying an inert gas to the inside of the radioactive substance storage container, and a gas supply unit for supplying a carrier gas to a side upstream of the dry vacuum pump in a gas flow direction in the discharge line.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a drying device and method for a radioactive material storage container that dries the inside of a container for storing radioactive materials such as radioactive waste.

Background Art

[0002] Radioactive waste such as spent fuel generated in a nuclear reactor of a nuclear power plant is stored in a radioactive material storage container, transported to a storage facility, a reprocessing facility, etc., and stored or reprocessed. The operation of storing radioactive waste in a radioactive material storage container is performed, for example, in a fuel pool. That is, the radioactive material storage container is submerged in the water of the fuel pool, and the radioactive waste in the water of the fuel pool is stored in the radioactive material storage container. Then, the radioactive material storage container is lifted from the fuel pool to the work floor, the internal water is drained, and then the inside is vacuum-dried.

[0003] Conventionally, the drying operation of a radioactive material storage container evacuates the air inside the radioactive material storage container with an oil rotary pump (oil vacuum pump) for vacuum drying. However, depending on the type of gas to be exhausted, it is difficult for a dry vacuum pump to obtain a sufficient exhaust speed.

[0004] Therefore, as a drying device for a radioactive material storage container using two types of inert gases, for example, there is a technique described in Patent Document 1 below. The container drying device described in Patent Document 1 supplies helium gas and nitrogen gas having a molecular weight larger than that of helium gas into the radioactive material storage container, and discharges the helium gas inside the radioactive material storage container by being entrained in nitrogen gas by a dry vacuum pump. According to the conventional drying device for a radioactive material storage container, the exhaust ​​​​​​​​​By using easily discharged nitrogen gas as a carrier gas, helium gas that is difficult to discharge can be easily discharged.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Conventional drying devices for radioactive substance storage containers require a helium gas supply line for supplying helium gas and a nitrogen gas supply line for supplying nitrogen gas, resulting in a complex structure and a problem of the device becoming large-sized.

[0007] The present disclosure solves the above-described problems and aims to provide a drying device and method for a radioactive substance storage container that suppresses the enlargement of the device by simplifying the structure.

Means for Solving the Problems

[0008] The drying device for a radioactive substance storage container of the present disclosure for achieving the above object includes an exhaust line for discharging the gas inside the radioactive substance storage container, a dry vacuum pump provided in the exhaust line, an inert gas supply line for supplying an inert gas into the radioactive substance storage container, and a gas supply unit for supplying a carrier gas upstream of the dry vacuum pump in the gas flow direction in the exhaust line.

[0009] Further, the drying method for a radioactive substance storage container of the present disclosure involves supplying an inert gas into the radioactive substance storage container. ​​​​​​​​A step of supplying a predetermined amount of gas, and evacuating the gas containing the inert gas inside the radioactive substance storage container from an exhaust line by a dry vacuum pump, and if the pressure or pressure correlation value inside the radioactive substance storage container does not decrease to a predetermined pressure set in advance, a step of supplying a carrier gas to the upstream side in the gas flow direction from the dry vacuum pump in the exhaust line. And a step of evacuating the gas containing the inert gas inside the radioactive substance storage container from an exhaust line by a dry vacuum pump, and if the pressure or pressure correlation value inside the radioactive substance storage container does not decrease to a predetermined pressure set in advance, a step of supplying a carrier gas to the upstream side in the gas flow direction from the dry vacuum pump in the exhaust line. And a step of evacuating the gas containing the inert gas inside the radioactive substance storage container from an exhaust line by a dry vacuum pump, and if the pressure or pressure correlation value inside the radioactive substance storage container does not decrease to a predetermined pressure set in advance, a step of supplying a carrier gas to the upstream side in the gas flow direction from the dry vacuum pump in the exhaust line. And a step of evacuating the gas containing the inert gas inside the radioactive substance storage container from an exhaust line by a dry vacuum pump, and if the pressure or pressure correlation value inside the radioactive substance storage container does not decrease to a predetermined pressure set in advance, a step of supplying a carrier gas to the upstream side in the gas flow direction from the dry vacuum pump in the exhaust line. It has.

Advantages of the Invention

[0010] According to the drying device and method of the radioactive substance storage container of the present disclosure, it is possible to suppress the enlargement of the device by simplifying the structure. According to the drying device and method of the radioactive substance storage container of the present disclosure, it is possible to suppress the enlargement of the device by simplifying the structure.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0012] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited by this embodiment, and when there are a plurality of embodiments, those configured by combining each embodiment are also included. In addition, components in the embodiments include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those within a so-called equivalent range. Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited by this embodiment, and when there are a plurality of embodiments, those configured by combining each embodiment are also included. In addition, components in the embodiments include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those within a so-called equivalent range. Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited by this embodiment, and when there are a plurality of embodiments, those configured by combining each embodiment are also included. In addition, components in the embodiments include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those within a so-called equivalent range. Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited by this embodiment, and when there are a plurality of embodiments, those configured by combining each embodiment are also included. In addition, components in the embodiments include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those within a so-called equivalent range. Are included.

[0013] [First Embodiment] <Dryer for Radioactive Material Storage Container> FIG. 1 is a schematic configuration diagram showing a dryer for a radioactive material storage container according to the first embodiment.

[0014] In the first embodiment, as shown in FIG. 1, the dryer 10 for a radioactive material storage container includes an exhaust line 11, a dry vacuum pump 12, an inert gas supply line 13, and a gas supply unit 1 4.

[0015] The dryer 10 for a radioactive material storage container is for drying the inside of the radioactive material storage container 100. The radioactive material storage container 100 stores radioactive waste such as spent fuel generated in a nuclear reactor of a nuclear power plant.

[0016] The radioactive material storage container 100 is, for example, a cask and has a body portion 101 and a lid portion 102. The body portion 101 has an opening formed at the upper part and a bottom provided at the lower part, and has a cylindrical shape. The body portion 101 is made of carbon steel or stainless steel having a gamma-ray shielding function, and a resin (neutron shielding body) containing boron or a boron compound having a neutron shielding function is disposed on the outside. The lid portion 102 has, for example, a primary lid and a secondary lid. The primary lid is detachable from the opening of the body portion 101, and the secondary lid is detachable from the outside of the primary lid. The primary lid maintains the negative pressure inside the body portion 101 to prevent leakage of the filled gas, and shields radiation (gamma rays) emitted from the radioactive material stored inside. Further, the primary lid is provided with a resin (neutron shielding body) on the secondary lid side. The secondary lid has a pressure monitoring boundary pressurized against the atmosphere between the secondary lid and the primary lid.

[0017] An atomic power plant has a reactor building installed on the site. The reactor building has a reactor installed inside, and a fuel pool is provided where cooling water is stored and used fuel can be immersed. Also, a decontamination pit 111 is provided adjacent to the fuel pool in the reactor building, and an operation floor 112 is provided adjacent to the decontamination pit 111 and located above the upper surface of the cooling water in the fuel pool.

[0018] A processing pit for loading fuel is provided adjacent to the fuel pool in the reactor building. Cooling water is stored in the processing pit. The radioactive material storage container 100 has its lid part 102 removed first, and then its body part 101 is submerged in the water of the processing pit. In this state, a crane is used to store the used fuel in the water of the fuel pool into the body part 101. Next, after installing a primary lid at the opening of the body part 101, the radioactive material storage container 100 is lifted from the processing pit using a crane, placed on the decontamination pit 111, and the lid part 102 is fixed to the body part 101. Then, after discharging the water filled inside the radioactive material storage container 100, it is vacuum dried. The drying device 10 for the radioactive material storage container is used for the vacuum drying operation inside the radioactive material storage container 100. The drying device 10 for the radioactive material storage container is provided on the operation floor 112.

[0019] The radioactive material storage container 100 is provided with a vent line 103 and a drain line 10 4 on the lid part 102. The vent line 103 is inserted through the lid part 102 in the thickness direction and communicates the upper end part of the body part 101 inside and outside the radioactive material storage container 100. The drain line 1 04 is inserted through the lid part 102 in the thickness direction and communicates the lower end part of the body part 101 inside and outside the radioactive material storage container 100.

[0020] The exhaust line 11 has one end connected to the vent 103 in the lid portion 102 of the radioactive substance storage container 100. The exhaust line 11 is provided with a vacuum drying unit 21. The vacuum drying unit 21 has a cold trap 22, a filter 23, and a dry vacuum pump 12. The other end of the exhaust line 11 is connected to the exhaust treatment system of the reactor building. The cold trap 22 is provided with a refrigerant supply line 24 to which a refrigerant is supplied. The cold trap 22 condenses the water vapor exhausted through the exhaust line 11 by the refrigerant supplied from the refrigerant supply line 24 and removes it as a solid or a liquid.

[0021] The filter 23 removes harmful substances from the gas exhausted through the exhaust line 11. The dry vacuum pump 12 exhausts the gas such as air and water vapor remaining in the radioactive substance storage container 100 by applying an exhaust pressure (vacuum pressure) to the radioactive substance storage container 100 through the exhaust line 11. Here, the dry vacuum pump 12 is a mechanical vacuum pump that does not use lubricating oil or liquid in the vacuum chamber of the pump. As the dry vacuum pump 12, for example, a screw type dry vacuum pump or a roots type dry vacuum pump is applicable. Therefore, when the dry vacuum pump 12 operates, the exhaust pressure acts on the upper part inside the radioactive substance storage container 100 through the exhaust line 11. Then, the gas inside the radioactive substance storage container 100 is exhausted through the exhaust line 11. At this time, the gas discharged from the radioactive substance storage container 100 to the exhaust line 11 has the water vapor condensed by the cold trap 22 and removed as a solid or a liquid, and the harmful substances contained therein are removed by the filter 23.

[0022] ​​​​​​​​​​ is obtained.

[0023] One end of the inert gas supply line 13 is connected to the radioactive substance storage container 100 side from the vacuum drying unit 21 (cold trap 22) in the exhaust line 11. The inert gas supply A three-way valve 25 is provided at the connection part of the line 13 and the exhaust line 11. The inert gas supply Line 13 has an inert gas supply source 26 connected to the other end. The inert gas is, for example, he lium gas, and the inert gas supply source 26 stores helium gas. The inert gas supply Source 26 is, for example, a cylinder. The inert gas supply line 13 is provided with a first opening / closing device 27 . The first opening / closing device 27 can adjust the supply amount of helium gas flowing from the inert gas supply source 26 to the inert gas supply line 13 . The first opening / closing device 27 measures the volume of the inert gas flowing from the inert gas supply line 13 to the volume measurement unit, and when the preset volume is reached, it cuts off the flow. The first opening / closing device 27 is, for example, a mass flow controller having a function as a valve and volume measurement and calculation functions. Note that the first opening / closing device 27 may be a stop valve or a flow rate adjustment valve. Therefore, when the first opening / closing device 27 is opened, the helium gas of the inert gas supply source 26 is inactivated

[0024] Gas is supplied from the inert gas supply line 13 and the exhaust line 11 through the vent line 103 to the upper part of the radioactive substance storage container 100. At this time, by controlling the opening and closing of the first opening / closing device 27 , the supply amount of helium gas supplied to the radioactive substance storage container 100 can be adjusted . . .

[0025] The gas supply unit 14 is in the gas flow direction from the dry vacuum pump 12 in the exhaust line 11 A carrier gas is supplied to the upstream side of . In the first embodiment, the carrier gas is air. The gas supply unit 14 has a gas supply line 31 and a second on-off device 32. The gas supply line 31 has one end connected to the exhaust line 11 and the other end open to the atmosphere. The gas supply line 31 has one end connected to the downstream side in the gas flow direction of the cold trap 22 and the filter 23 in the exhaust line 11, that is, the connection portion 33 between the filter 23 and the dry vacuum pump 12.

[0026] The gas supply line 31 is provided with a second on-off device 32. The second on-off device 32 can adjust the supply amount of the carrier gas supplied from the gas supply line 31 to the exhaust line 11. The second on-off device 32 is, for example, a flow rate adjustment valve or a stop valve. The gas passage area of the gas supply line 31 is set smaller than the gas passage area of the exhaust line 11. The gas passage area of the gas supply line 31 is the passage area of the second on-off device 32 when the second on-off device 32 is opened. The gas passage area of the exhaust line 11 is the passage area between the filter 23 and the gas supply line 31 in the exhaust line 11.

[0027] Although the carrier gas is air, it is not limited to air. The carrier gas may be a gas containing a gas having a molecular weight larger than that of helium gas, which is an inert gas, or an inert gas. In this case, the gas supply line 31 may be connected to a cylinder as a carrier gas supply source at the other end open to the atmosphere.

[0028] Therefore, when the dry vacuum pump 12 is operated, the exhaust pressure is radiated through the exhaust line 11. ​​​​​​​​The pressure acts on the inside of the active material storage container 100 and also on the gas supply line 31. When the second opening / closing device 32 is opened, outside air is sucked in from the other end of the gas supply line 31. That is, the gas inside the radioactive material storage container 100 is exhausted through the exhaust line 11. At the same time, outside air is taken into the exhaust line 11 through the gas supply line 31. , and is exhausted together with the gas inside the radioactive material storage container 100.

[0029] The control device 41 is capable of controlling the operation of the dry vacuum pump 12 and the first opening and closing device 2. 7 and the second opening / closing device 32. A pressure gauge 42 is provided on the radioactive material storage container 100 side of the pressure gauge 25. A total of 42 measurement results are input. At this time, the three-way valve 25 in the exhaust line 11 outputs the The pressure on the side of the radioactive material storage container 100 is equal to the pressure inside the radioactive material storage container 100. Therefore, it can be inferred that the measurement result of the pressure gauge 42 is the internal pressure of the radioactive material storage container 100. It is determined.

[0030] The control device 41 controls the flow of the carrier gas (air) from the gas supply line 31 to the exhaust line 11. That is, the control device 41 controls the supply start timing. The gas supply line 31 supplies the gas to the exhaust line 11 based on the pressure inside the storage container 100. The control device 41 sets the start time of supplying rear gas (air). When the inside of the radioactive material storage container 100 is depressurized by the pump 12, the radioactive material storage container 100 If the internal pressure does not drop to a preset pressure, the exhaust gas will be discharged from the gas supply line 31. The supply of carrier gas (air) to the line 11 is started. When the pressure reduction rate inside the substance storage container 100 becomes equal to or less than a preset predetermined pressure change rate, the supply of carrier gas (air) from the gas supply line 31 to the exhaust line 11 may be started. Furthermore, when a preset predetermined time has elapsed since the start of depressurization inside the radioactive substance storage container 100 by the dry vacuum pump 12, the control device 41 may start the supply of carrier gas (air) from the gas supply line 3 1 to the exhaust line 11.

[0031] <Method for drying a radioactive substance storage container> FIG. 2 is a flowchart showing a method for drying a radioactive substance storage container.

[0032] The method for drying a radioactive substance storage container includes a step of supplying a predetermined amount of inert gas (helium gas) into the radioactive substance storage container 100, a step of exhausting the gas containing the inert gas inside the radioactive substance storage container 100 by the dry vacuum pump 12, and a step of supplying carrier gas (air) to the upstream side in the gas flow direction from the dry vacuum pump 12 in the exhaust line 11 when the pressure or pressure correlation value inside the radioactive substance storage container 100 does not decrease to a preset predetermined pressure. It has.

[0033] Here, the pressure correlation value is pressure, pressure change rate, and time. That is, when the pressure inside the radioactive substance storage container 100 does not reach the predetermined pressure, or when the pressure reduction rate inside the radioactive substance storage container 100 becomes equal to or less than the predetermined pressure change rate, or when a predetermined time has elapsed since the dry vacuum pump 12 started operating, the supply of carrier gas to the inside of the radioactive substance storage container 100 is started.

[0034] Specifically, as shown in FIGS. 1 and 2, in step S11, the radioactive material storage container 100 is transported to the processing pit. The reactor building is provided with a processing pit adjacent to the fuel pool. The radioactive material storage container 100 has its body 101 immersed in the cooling water of the processing pit. In step S12, the operator uses a crane to store the spent fuel immersed in the fuel pool into the body 101 of the radioactive material storage container 100 in the processing pit. When a predetermined amount of spent fuel is stored in the radioactive material storage container 100, in step S13

[0035] a lid 102 is installed on the body 101 of the processing pit. In step S14, using a crane the radioactive material storage container 100 containing the spent fuel is transported from the processing pit to the decontamination pit 11 1. Here, the lid 102 is fixed to the body 101. Then, in step S15 a drain line is connected to the drain line 104 of the radioactive material storage container 100, and the water filled inside the radioactive material storage container 100 is discharged from the drain line. Note that the drainage method of the radioactive material storage container 100 is not limited to this method. For example, gas such as air may be supplied to the inside of the radioactive material storage container 100, and the internal water may be pushed out and discharged from the drain line. It may also be possible.

[0036] When the water is discharged from the inside of the radioactive material storage container 100, in step S16, an exhaust line 11, an inert gas supply line 13, and a gas supply unit 14 are connected to the radioactive material storage container 100. Then, the operator performs an operation for drying the radioactive material storage container 100 on the control device 41. First, the control device 41 operates the dry vacuum pump 12 to apply an exhaust pressure from the exhaust line 11 to the inside of the radioactive material storage container 100. Then, the radioactive material storage container 100 The container 100 has the water vapor remaining inside being suctioned to the outside together with air and exhausted, and the internal pressure decreases. When the pressure inside the radioactive substance storage container 100 decreases, the boiling point of the water remaining inside decreases, and it evaporates into water vapor in an environment close to normal temperature. This water vapor is exhausted through the exhaust line 11 by the exhaust of the dry vacuum pump 12. At this time, the three-way valve 25 connects the exhaust line 11 and blocks the communication between the exhaust line 11 and the inert gas supply line 13 to be in a state. When the inside of the radioactive substance storage container 100 is depressurized to a predetermined pressure, the operation of the dry vacuum pump 12 is stopped.

[0037] In step S17, the control device 41 controls the first opening / closing device 27 to open, and supplies the helium gas from the inert gas supply source 26 through the inert gas supply line 13 and the exhaust line 11 to the inside of the radioactive substance storage container 100 from the vent line 103. At this time, the three-way valve 25 connects the radioactive substance storage container 100 side of the exhaust line 11 and the inert gas supply line 13, and blocks the vacuum drying unit 21 side of the exhaust line 11. By supplying helium gas to the inside of the radioactive substance storage container 100, the inside of the radioactive substance storage container 100 is cooled . When the radioactive substance storage container 100 is filled with a predetermined amount of helium gas, the control device 41 controls the first opening / closing device 27 to close and stops the supply of helium gas to the radioactive substance storage container 100. The supply amount of helium gas to be supplied to the radioactive substance storage container 100 is determined by the volume of the radioactive substance storage container 100. The first opening / closing device 27 closes when the amount of helium gas flowing to be supplied to the radioactive substance storage container 100 flows through. Note that if the first opening / closing device 27 is a stop valve or a flow rate adjustment valve, the pipe diameters and pressures of the inert gas supply line 13 and the exhaust line 11 0 is cooled. When the radioactive substance storage container 100 is filled with a predetermined amount of helium gas, the control device 41 controls the first opening / closing device 27 to close and stops the supply of helium gas to the radioactive substance storage container 100. The supply amount of helium gas to be supplied to the radioactive substance storage container 100 is determined by the volume of the radioactive substance storage container 100. The first opening / closing device 27 closes when the amount of helium gas flowing to be supplied to the radioactive substance storage container 100 flows through. Note that if the first opening / closing device 27 is a stop valve or a flow rate adjustment valve, the pipe diameters and pressures of the inert gas supply line 13 and the exhaust line 11 controls the first opening / closing device 27 to close and stops the supply of helium gas to the radioactive substance storage container 100. The supply amount of helium gas to be supplied to the radioactive substance storage container 100 is determined by the volume of the radioactive substance storage container 100. The first opening / closing device 27 closes when the amount of helium gas flowing to be supplied to the radioactive substance storage container 100 flows through. is determined by the volume of the radioactive substance storage container 100. The first opening / closing device 27 closes when the amount of helium gas flowing to be supplied to the radioactive substance storage container 100 flows through. 00 closes when the amount of helium gas flows through. Note that if the first opening / closing device 27 is a stop valve or a flow rate adjustment valve, the pipe diameters and pressures of the inert gas supply line 13 and the exhaust line 11 are such that if the first opening / closing device 27 is a stop valve or a flow rate adjustment valve, the pipe diameters and pressures of the inert gas supply line 13 and the exhaust line 11 By means of force, the supply amount of helium gas to the radioactive substance storage container 100 may be converted into the opening time of a stop valve or a flow rate adjustment valve in advance through design, calculation, experiment, etc. It may be converted into the opening time of a stop valve or a flow rate adjustment valve in advance through design, calculation, experiment, etc.

[0038] In step S18, the control device 41 operates the dry vacuum pump 12 again and applies the exhaust pressure from the exhaust line 11 to the inside of the radioactive substance storage container 100. Then, the radioactive substance storage container 100 exhausts the helium gas and water vapor remaining inside to the outside, and the internal pressure decreases. At this time, the three-way valve 25 communicates the exhaust line 11 and blocks the communication between the exhaust line 11 and the inert gas supply line 13. It operates the dry vacuum pump 12 again and applies the exhaust pressure from the exhaust line 11 to the inside of the radioactive substance storage container 100. Then, the radioactive substance storage container 100 exhausts the helium gas and water vapor remaining inside to the outside, and the internal pressure decreases. At this time, the three-way valve 25 communicates the exhaust line 11 and blocks the communication between the exhaust line 11 and the inert gas supply line 13. It operates the dry vacuum pump 12 again and applies the exhaust pressure from the exhaust line 11 to the inside of the radioactive substance storage container 100. Then, the radioactive substance storage container 100 exhausts the helium gas and water vapor remaining inside to the outside, and the internal pressure decreases. At this time, the three-way valve 25 communicates the exhaust line 11 and blocks the communication between the exhaust line 11 and the inert gas supply line 13. In step S18, the control device 41 operates the dry vacuum pump 12 again and applies the exhaust pressure from the exhaust line 11 to the inside of the radioactive substance storage container 100. Then, the radioactive substance storage container 100 exhausts the helium gas and water vapor remaining inside to the outside, and the internal pressure decreases. At this time, the three-way valve 25 communicates the exhaust line 11 and blocks the communication between the exhaust line 11 and the inert gas supply line 13. In step S18, the control device 41 operates the dry vacuum pump 12 again and applies the exhaust pressure from the exhaust line 11 to the inside of the radioactive substance storage container 100. Then, the radioactive substance storage container 100 exhausts the helium gas and water vapor remaining inside to the outside, and the internal pressure decreases. At this time, the three-way valve 25 communicates the exhaust line 11 and blocks the communication between the exhaust line 11 and the inert gas supply line 13.

[0039] In step S19, the control device 41 determines whether the internal pressure of the radioactive substance storage container 100 measured by the pressure gauge 42 has decreased to a predetermined pressure set in advance. Specifically, the control device 41 determines whether the internal pressure of the radioactive substance storage container 100 has decreased to the predetermined pressure within a predetermined time set in advance. Here, if it is determined (No) that the internal pressure of the radioactive substance storage container 100 has not decreased to the predetermined pressure, in step S20, the second opening / closing device 32 is controlled to open while the operation of the dry vacuum pump 12 is continued. Then, the exhaust pressure in the exhaust line 11 acts on the gas supply line 31, and external air is inhaled into the gas supply line 31 and supplied to the exhaust line 11. In step S19, the control device 41 determines whether the internal pressure of the radioactive substance storage container 100 measured by the pressure gauge 42 has decreased to a predetermined pressure set in advance. Specifically, the control device 41 determines whether the internal pressure of the radioactive substance storage container 100 has decreased to the predetermined pressure within a predetermined time set in advance. Here, if it is determined (No) that the internal pressure of the radioactive substance storage container 100 has not decreased to the predetermined pressure, in step S20, the second opening / closing device 32 is controlled to open while the operation of the dry vacuum pump 12 is continued. Then, the exhaust pressure in the exhaust line 11 acts on the gas supply line 31, and external air is inhaled into the gas supply line 31 and supplied to the exhaust line 11. In step S19, the control device 41 determines whether the internal pressure of the radioactive substance storage container 100 measured by the pressure gauge 42 has decreased to a predetermined pressure set in advance. Specifically, the control device 41 determines whether the internal pressure of the radioactive substance storage container 100 has decreased to the predetermined pressure within a predetermined time set in advance. Here, if it is determined (No) that the internal pressure of the radioactive substance storage container 100 has not decreased to the predetermined pressure, in step S20, the second opening / closing device 32 is controlled to open while the operation of the dry vacuum pump 12 is continued. Then, the exhaust pressure in the exhaust line 11 acts on the gas supply line 31, and external air is inhaled into the gas supply line 31 and supplied to the exhaust line 11. In step S19, the control device 41 determines whether the internal pressure of the radioactive substance storage container 100 measured by the pressure gauge 42 has decreased to a predetermined pressure set in advance. Specifically, the control device 41 determines whether the internal pressure of the radioactive substance storage container 100 has decreased to the predetermined pressure within a predetermined time set in advance. Here, if it is determined (No) that the internal pressure of the radioactive substance storage container 100 has not decreased to the predetermined pressure, in step S20, the second opening / closing device 32 is controlled to open while the operation of the dry vacuum pump 12 is continued. Then, the exhaust pressure in the exhaust line 11 acts on the gas supply line 31, and external air is inhaled into the gas supply line 31 and supplied to the exhaust line 11. In step S19, the control device 41 determines whether the internal pressure of the radioactive substance storage container 100 measured by the pressure gauge 42 has decreased to a predetermined pressure set in advance. Specifically, the control device 41 determines whether the internal pressure of the radioactive substance storage container 100 has decreased to the predetermined pressure within a predetermined time set in advance. Here, if it is determined (No) that the internal pressure of the radioactive substance storage container 100 has not decreased to the predetermined pressure, in step S20, the second opening / closing device 32 is controlled to open while the operation of the dry vacuum pump 12 is continued. Then, the exhaust pressure in the exhaust line 11 acts on the gas supply line 31, and external air is inhaled into the gas supply line 31 and supplied to the exhaust line 11. In step S19, the control device 41 determines whether the internal pressure of the radioactive substance storage container 100 measured by the pressure gauge 42 has decreased to a predetermined pressure set in advance. Specifically, the control device 41 determines whether the internal pressure of the radioactive substance storage container 100 has decreased to the predetermined pressure within a predetermined time set in advance. Here, if it is determined (No) that the internal pressure of the radioactive substance storage container 100 has not decreased to the predetermined pressure, in step S20, the second opening / closing device 32 is controlled to open while the operation of the dry vacuum pump 12 is continued. Then, the exhaust pressure in the exhaust line 11 acts on the gas supply line 31, and external air is inhaled into the gas supply line 31 and supplied to the exhaust line 11. In step S19, the control device 41 determines whether the internal pressure of the radioactive substance storage container 100 measured by the pressure gauge 42 has decreased to a predetermined pressure set in advance. Specifically, the control device 41 determines whether the internal pressure of the radioactive substance storage container 100 has decreased to the predetermined pressure within a predetermined time set in advance. Here, if it is determined (No) that the internal pressure of the radioactive substance storage container 100 has not decreased to the predetermined pressure, in step S20, the second opening / closing device 32 is controlled to open while the operation of the dry vacuum pump 12 is continued. Then, the exhaust pressure in the exhaust line 11 acts on the gas supply line 31, and external air is inhaled into the gas supply line 31 and supplied to the exhaust line 11. In step S19, the control device 41 determines whether the internal pressure of the radioactive substance storage container 100 measured by the pressure gauge 42 has decreased to a predetermined pressure set in advance. Specifically, the control device 41 determines whether the internal pressure of the radioactive substance storage container 100 has decreased to the predetermined pressure within a predetermined time set in advance. Here, if it is determined (No) that the internal pressure of the radioactive substance storage container 100 has not decreased to the predetermined pressure, in step S20, the second opening / closing device 32 is controlled to open while the operation of the dry vacuum pump 12 is continued. Then, the exhaust pressure in the exhaust line 11 acts on the gas supply line 31, and external air is inhaled into the gas supply line 31 and supplied to the exhaust line 11.

[0040] When the dry vacuum pump 12 operates, the radioactive substance storage container 100 exhausts the helium gas and water vapor remaining inside to the outside, and the internal pressure decreases. At this time, the downstream side of the exhaust line 11 from the dry vacuum pump 12 is at atmospheric pressure, and the upstream side of the dry vacuum pump 12 is When the dry vacuum pump 12 operates, the radioactive substance storage container 100 exhausts the helium gas and water vapor remaining inside to the outside, and the internal pressure decreases. At this time, the downstream side of the exhaust line 11 from the dry vacuum pump 12 is at atmospheric pressure, and the upstream side of the dry vacuum pump 12 is When the dry vacuum pump 12 operates, the radioactive substance storage container 100 exhausts the helium gas and water vapor remaining inside to the outside, and the internal pressure decreases. At this time, the downstream side of the exhaust line 11 from the dry vacuum pump 12 is at atmospheric pressure, and the upstream side of the dry vacuum pump 12 is The flow side becomes a low pressure equivalent to that of the radioactive substance storage container 100. The dry vacuum pump 12 applies a vacuum pressure (exhaust pressure) by rotating a rotor disposed inside the casing. However, when the upstream pressure becomes extremely low with respect to the pressure on the downstream side of the rotor, the gas on the downstream side of the rotor flows back to the upstream side of the rotor through the gap between the casing and the rotor, and a circulating flow is generated here. Then, it becomes difficult for the dry vacuum pump 12 to apply an appropriate vacuum pressure to the upstream side of the exhaust line 11. Therefore, when the control device 41 detects that the pressure inside the radioactive substance storage container 100 becomes difficult to decrease due to the generation of a circulating flow by the dry vacuum pump 12, the control device 41 opens the second opening / closing device 32 and supplies external air from the gas supply line 31 to the exhaust line 11 on the upstream side of the dry vacuum pump 12. Then, the differential pressure between the downstream side and the upstream side of the dry vacuum pump 12 in the exhaust line 11 becomes smaller, the circulating flow disappears, and the vacuum pressure generated by the operation of the dry vacuum pump 12 can be appropriately applied from the exhaust line 11 to the inside of the radioactive substance storage container 100. At this time, since air containing nitrogen gas with a large molecular weight has a property of a large intermolecular force, it is easy to obtain a sufficient exhaust speed in the dry vacuum pump 12. Therefore, air can be used as a carrier gas for discharging the helium gas inside the radioactive substance storage container 100, and the helium gas, which is difficult to discharge by air, can be efficiently discharged. After supplying external air from the gas supply line 31 to the exhaust line 11 in step S20, the process returns to step S19, and the control device 41 measures the pressure of the radioactive substance storage container 100 again by the pressure gauge 42.

[0041]

[0042] Determine whether the internal pressure of the storage container 100 has dropped to a predetermined pressure. Here, radioactive substances If it is determined (No) that the internal pressure of the radioactive substance storage container 100 has not dropped to the predetermined pressure, as described above, the process of step S20 is continued. On the other hand, if it is determined (Yes) that the internal pressure of the radioactive substance storage container 100 has dropped to the predetermined pressure, in step S21, the second opening and closing device 32 is controlled to close, and the supply of air from the gas supply line 31 to the exhaust line 11 is stopped As described above, the process of step S20 is continued. On the other hand, if it is determined (Yes) that the internal pressure of the radioactive substance storage container 100 has dropped to the predetermined pressure, in step S21, the second opening and closing device 32 is controlled to close, and the supply of air from the gas supply line 31 to the exhaust line 11 is stopped As described above, the process of step S20 is continued. On the other hand, if it is determined (Yes) that the internal pressure of the radioactive substance storage container 100 has dropped to the predetermined pressure, in step S21, the second opening and closing device 32 is controlled to close, and the supply of air from the gas supply line 31 to the exhaust line 11 is stopped As described above, the process of step S20 is continued. On the other hand, if it is determined (Yes) that the internal pressure of the radioactive substance storage container 100 has dropped to the predetermined pressure, in step S21, the second opening and closing device 32 is controlled to close, and the supply of air from the gas supply line 31 to the exhaust line 11 is stopped As described above, the process of step S20 is continued. On the other hand, if it is determined (Yes) that the internal pressure of the radioactive substance storage container 100 has dropped to the predetermined pressure, in step S21, the second opening and closing device 32 is controlled to close, and the supply of air from the gas supply line 31 to the exhaust line 11 is stopped As described above, the process of step S20 is continued. On the other hand, if it is determined (Yes) that the internal pressure of the radioactive substance storage container 100 has dropped to the predetermined pressure, in step S21, the second opening and closing device 32 is controlled to close, and the supply of air from the gas supply line 31 to the exhaust line 11 is stopped As described above, the process of step S20 is continued. On the other hand, if it is determined (Yes) that the internal pressure of the radioactive substance storage container 100 has dropped to the predetermined pressure, in step S21, the second opening and closing device 32 is controlled to close, and the supply of air from the gas supply line 31 to the exhaust line 11 is stopped As described above, the process of step S20 is continued. On the other hand, if it is determined (Yes) that the internal pressure of the radioactive substance storage container 100 has dropped to the predetermined pressure, in step S21, the second opening and closing device 32 is controlled to close, and the supply of air from the gas supply line 31 to the exhaust line 11 is stopped

[0043] The predetermined pressure is, for example, 700 Pa, which is the pressure at which the moisture content in the gas composition inside the radioactive substance storage container 100 becomes 10% by weight or less. According to the Japan Atomic Energy Society Standards, as a calculation example of the oxidation and hydrogen adsorption amount of the fuel cladding tube, if the moisture content in the gas composition inside the metal cask is limited to 10% (mass), based on the cask design, the oxidation and hydrogen adsorption amount of the fuel cladding tube will be negligible and will not affect the fuel, as described The predetermined pressure is, for example, 700 Pa, which is the pressure at which the moisture content in the gas composition inside the radioactive substance storage container 100 becomes 10% by weight or less. According to the Japan Atomic Energy Society Standards, as a calculation example of the oxidation and hydrogen adsorption amount of the fuel cladding tube, if the moisture content in the gas composition inside the metal cask is limited to 10% (mass), based on the cask design, the oxidation and hydrogen adsorption amount of the fuel cladding tube will be negligible and will not affect the fuel, as described The predetermined pressure is, for example, 700 Pa, which is the pressure at which the moisture content in the gas composition inside the radioactive substance storage container 100 becomes 10% by weight or less. According to the Japan Atomic Energy Society Standards, as a calculation example of the oxidation and hydrogen adsorption amount of the fuel cladding tube, if the moisture content in the gas composition inside the metal cask is limited to 10% (mass), based on the cask design, the oxidation and hydrogen adsorption amount of the fuel cladding tube will be negligible and will not affect the fuel, as described The predetermined pressure is, for example, 700 Pa, which is the pressure at which the moisture content in the gas composition inside the radioactive substance storage container 100 becomes 10% by weight or less. According to the Japan Atomic Energy Society Standards, as a calculation example of the oxidation and hydrogen adsorption amount of the fuel cladding tube, if the moisture content in the gas composition inside the metal cask is limited to 10% (mass), based on the cask design, the oxidation and hydrogen adsorption amount of the fuel cladding tube will be negligible and will not affect the fuel, as described The predetermined pressure is, for example, 700 Pa, which is the pressure at which the moisture content in the gas composition inside the radioactive substance storage container 100 becomes 10% by weight or less. According to the Japan Atomic Energy Society Standards, as a calculation example of the oxidation and hydrogen adsorption amount of the fuel cladding tube, if the moisture content in the gas composition inside the metal cask is limited to 10% (mass), based on the cask design, the oxidation and hydrogen adsorption amount of the fuel cladding tube will be negligible and will not affect the fuel, as described The predetermined pressure is, for example, 700 Pa, which is the pressure at which the moisture content in the gas composition inside the radioactive substance storage container 100 becomes 10% by weight or less. According to the Japan Atomic Energy Society Standards, as a calculation example of the oxidation and hydrogen adsorption amount of the fuel cladding tube, if the moisture content in the gas composition inside the metal cask is limited to 10% (mass), based on the cask design, the oxidation and hydrogen adsorption amount of the fuel cladding tube will be negligible and will not affect the fuel, as described

[0044] <Pressure change of the radioactive substance storage container> Figure 3 is a time chart showing the drying method of the radioactive substance storage container.

[0045] As shown in FIGS. 1 and 3, when the inside of the radioactive substance storage container 100 is depressurized to a predetermined pressure by the operation of the dry vacuum pump 12, at time t1, the dry vacuum pump 12 is stopped As shown in FIGS. 1 and 3, when the inside of the radioactive substance storage container 100 is depressurized to a predetermined pressure by the operation of the dry vacuum pump 12, at time t1, the dry vacuum pump 12 is stopped (Turn it OFF). Here, the first opening / closing device 27 is controlled to open, and the supply of helium gas to the radioactive substance storage container 100 is started, and at time t2, the supply of helium gas is stopped. Then , the internal pressure of the radioactive substance storage container 100 rises. At time t3, when the internal pressure of the radioactive substance storage container 100 reaches the pressure P0 (substantially atmospheric pressure), the dry vacuum pump 12 is operated so that helium gas, water vapor, etc. remaining inside the radioactive substance storage container 100 are exhausted to the outside and the internal pressure decreases.

[0046] However, as described above, since helium gas has the property of having a small intermolecular force, it is difficult to discharge it from the radioactive substance storage container 100 by the dry vacuum pump 12. Therefore, the decrease in the internal pressure of the radioactive substance storage container 100 becomes slow, and the gas exhaust speed from the radioactive substance storage container 100 decreases. At time t4, the rate of decrease in the internal pressure of the radioactive substance storage container 100 approaches 0 , and the gas exhaust speed also approaches 0. Therefore, at this time t4, the second opening / closing device 32 is controlled to open to supply carrier gas (air) to the upstream side of the dry vacuum pump 12. The timing to start the supply of the carrier gas is preferably when the rate of decrease in the internal pressure of the radioactive substance storage container 100 becomes equal to or less than a preset predetermined pressure change rate. However, since the timing when the rate of decrease in the internal pressure of the radioactive substance storage container 100 becomes equal to or less than the predetermined pressure change rate

[0047] is determined according to the volume of the radioactive substance storage container 100, when the internal pressure of the radioactive substance storage container 100 does not decrease to the predetermined pressure within a predetermined time, the supply of nitrogen gas may be started. Also, when a predetermined time has elapsed after the dry vacuum pump 12 is operated ​​Then, the supply of the carrier gas (air) may be started. This predetermined pressure is, for example, 700 Pa, and is the pressure at which the moisture content in the gas composition inside the radioactive substance storage container 100 becomes 10% by weight or less.

[0048] At time t4, when the carrier gas (air) is supplied to the upstream side of the dry vacuum pump 12, the internal pressure of the radioactive substance storage container 100 drops suddenly. Then, at time t5, when the internal pressure of the radioactive substance storage container 100 drops to the predetermined pressure, the second opening / closing device 32 is closed and the operation of the dry vacuum pump 12 is stopped. After that, after the time for checking whether the inside of the radioactive substance storage container 100 is dried has elapsed, between time t6 and time t7 the first opening / closing device 27 is controlled to open, and a predetermined amount of helium gas is supplied into the radioactive substance storage container 100, and the drying operation of the radioactive substance storage container 100 is completed. This predetermined pressure is, for example, 0.08 Pa.

[0049] [Second Embodiment] FIG. 3 is a schematic configuration diagram showing a drying device for a radioactive substance storage container according to the second embodiment. Note that members having the same functions as those in the above-described first embodiment are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0050] In the second embodiment, as shown in FIG. 3, a drying device 10A for a radioactive substance storage container includes an exhaust line 11, a dry vacuum pump 12, an inert gas supply line 13, and a gas supply unit 14A.

[0051] One end of the exhaust line 11 is connected to the vent 103 of the lid portion 102 of the radioactive substance storage container 100. The exhaust line 11 is provided with a vacuum drying unit 21. The vacuum ... The drying unit 21 includes a cold trap 22, a filter 23, and a dry vacuum pump 12. The other end of the exhaust line 11 is connected to an exhaust treatment system.

[0052] The inert gas supply line 13 has one end connected to the vacuum drying unit 21 in the exhaust line 11. (Cold trap 22) is connected to the radioactive material storage container 100 side. A three-way valve 25 is provided at the connection between the supply line 13 and the exhaust line 11. The inlet 13 is connected at the other end to an inert gas supply source 26. The inert gas is, for example, The inert gas supply source 26 stores helium gas. The line 13 is provided with a first opening and closing device 27 .

[0053] The gas supply unit 14A controls the flow of gas from the dry vacuum pump 12 in the exhaust line 11. The gas supply unit 14A supplies a carrier gas to the upstream side of the gas supply line 51. The gas supply line 51 has one end connected to the exhaust line 11 and the other end connected to the exhaust line 11. The gas supply line 51 has one end connected to the exhaust line 11 and the other end opened to the atmosphere. The upstream side of the cold trap 22 and the filter 23 in the gas flow direction, i.e., the cold The radioactive material storage container 100 is connected to a connection portion 53 between the trap 22 and the radioactive material storage container 100.

[0054] The gas supply line 51 is provided with a second opening and closing device 52. The second opening and closing device 52 The amount of carrier gas supplied from the supply line 51 to the exhaust line 11 can be adjusted. The opening and closing device 52 is, for example, a flow control valve or a stop valve. The area is set to be smaller than the gas passage area of ​​the exhaust line 11.

[0055] Also, check valves 54 and 55 are provided to prevent the backflow of gas from the gas supply line 51 through the exhaust line 11 to the radioactive substance storage container 100 side. The check valve 54 is provided between the three-way valve 25 and the connection part 53 in the exhaust line 11. The check valve 54 allows the flow of gas from the radioactive substance storage container 100 side to the vacuum drying unit 21 side, and blocks the flow of gas from the vacuum drying unit 21 side to the radioactive substance storage container 100 side. The check valve 55 is provided between the connection part 53 and the second opening / closing device 52 in the gas supply line 51. The check valve 55 allows the flow of gas from the second opening / closing device 52 side to the exhaust line 11 side, and blocks the flow of gas from the exhaust line 11 side to the second opening / closing device 52 side. Therefore, when the dry vacuum pump 12 is operated, the exhaust pressure acts on the inside of the radioactive substance storage container 100 through the exhaust line 11 and also acts on the gas supply line 51. At this time, when the second opening / closing device 52 is opened, external air is sucked in from the other end of the gas supply line 51. That is, the gas inside the radioactive substance storage container 100 is exhausted through the exhaust line 11, and external air is taken into the exhaust line 11 through the gas supply line 51 and exhausted together with the gas inside the radioactive substance storage container 100. The control device 41 can control the operation of the dry vacuum pump 12 and can also control the opening and closing of the first opening / closing device 27 and the second opening / closing device 52. The control device 41 receives the measurement result of the pressure gauge 42. The control device 41 controls the start timing of the supply of carrier gas (air) from the gas supply line 51 to the exhaust line 11. That is, the control device 41 is such that when the pressure gauge 42 measures The check valve 54 is provided between the three-way valve 25 and the connection part 53 in the exhaust line 11. The check valve 54 allows the flow of gas from the radioactive substance storage container 100 side to the vacuum drying unit 21 side, and blocks the flow of gas from the vacuum drying unit 21 side to the radioactive substance storage container 100 side. The check valve 55 is provided between the connection part 53 and the second opening / closing device 52 in the gas supply line 51. The check valve 55 allows the flow of gas from the second opening / closing device 52 side to the exhaust line 11 side, and blocks the flow of gas from the exhaust line 11 side to the second opening / closing device 52 side. Therefore, when the dry vacuum pump 12 is operated, the exhaust pressure acts on the inside of the radioactive substance storage container 100 through the exhaust line 11 and also acts on the gas supply line 51. At this time, when the second opening / closing device 52 is opened, external air is sucked in from the other end of the gas supply line 51. That is, the gas inside the radioactive substance storage container 100 is exhausted through the exhaust line 11, and external air is taken into the exhaust line 11 through the gas supply line 51 and exhausted together with the gas inside the radioactive substance storage container 100.

[0056] Therefore, when the dry vacuum pump 12 is operated, the exhaust pressure acts on the inside of the radioactive substance storage container 100 through the exhaust line 11 and also acts on the gas supply line 51. At this time, when the second opening / closing device 52 is opened, external air is sucked in from the other end of the gas supply line 51. That is, the gas inside the radioactive substance storage container 100 is exhausted through the exhaust line 11, and external air is taken into the exhaust line 11 through the gas supply line 51 and exhausted together with the gas inside the radioactive substance storage container 100. Also, when the dry vacuum pump 12 is operated, the exhaust pressure acts on the inside of the radioactive substance storage container 100 through the exhaust line 11 and also acts on the gas supply line 51. At this time, when the second opening / closing device 52 is opened, external air is sucked in from the other end of the gas supply line 51. That is, the gas inside the radioactive substance storage container 100 is exhausted through the exhaust line 11, and external air is taken into the exhaust line 11 through the gas supply line 51 and exhausted together with the gas inside the radioactive substance storage container 100. When the second opening / closing device 52 is opened, external air is sucked in from the other end of the gas supply line 51. That is, the gas inside the radioactive substance storage container 100 is exhausted through the exhaust line 11, and external air is taken into the exhaust line 11 through the gas supply line 51 and exhausted together with the gas inside the radioactive substance storage container 100. When the second opening / closing device 52 is opened, external air is sucked in from the other end of the gas supply line 51. That is, the gas inside the radioactive substance storage container 100 is exhausted through the exhaust line 11, and external air is taken into the exhaust line 11 through the gas supply line 51 and exhausted together with the gas inside the radioactive substance storage container 100. When the second opening / closing device 52 is opened, external air is sucked in from the other end of the gas supply line 51. That is, the gas inside the radioactive substance storage container 100 is exhausted through the exhaust line 11, and external air is taken into the exhaust line 11 through the gas supply line 51 and exhausted together with the gas inside the radioactive substance storage container 100. When the second opening / closing device 52 is opened, external air is sucked in from the other end of the gas supply line 51. That is, the gas inside the radioactive substance storage container 100 is exhausted through the exhaust line 11, and external air is taken into the exhaust line 11 through the gas supply line 51 and exhausted together with the gas inside the radioactive substance storage container 100.

[0057] The control device 41 can control the operation of the dry vacuum pump 12 and can also control the opening and closing of the first opening / closing device 27 and the second opening / closing device 52. The control device 41 receives the measurement result of the pressure gauge 42. The control device 41 controls the start timing of the supply of carrier gas (air) from the gas supply line 51 to the exhaust line 11. That is, the control device 41 is such that when the pressure gauge 42 measures The control device 41 can control the operation of the dry vacuum pump 12 and can also control the opening and closing of the first opening / closing device 27 and the second opening / closing device 52. The control device 41 receives the measurement result of the pressure gauge 42. The control device 41 controls the start timing of the supply of carrier gas (air) from the gas supply line 51 to the exhaust line 11. That is, the control device 41 is such that when the pressure gauge 42 measures The control device 41 can control the operation of the dry vacuum pump 12 and can also control the opening and closing of the first opening / closing device 27 and the second opening / closing device 52. The control device 41 receives the measurement result of the pressure gauge 42. The control device 41 controls the start timing of the supply of carrier gas (air) from the gas supply line 51 to the exhaust line 11. That is, the control device 41 is such that when the pressure gauge 42 measures The control device 41 can control the operation of the dry vacuum pump 12 and can also control the opening and closing of the first opening / closing device 27 and the second opening / closing device 52. The control device 41 receives the measurement result of the pressure gauge 42. The control device 41 controls the start timing of the supply of carrier gas (air) from the gas supply line 51 to the exhaust line 11. That is, the control device 41 is such that when the pressure gauge 42 measures Based on the pressure inside the radioactive substance storage container 100, the start time of supplying carrier gas (air) from the gas supply line 51 to the exhaust line 11 is set. Specifically, when the pressure inside the radioactive substance storage container 100 is reduced by the dry vacuum pump 12, the control device 41 does not start supplying carrier gas (air) from the gas supply line 51 to the exhaust line 11 until the pressure inside the radioactive substance storage container 100 drops to a preset predetermined pressure. When the inside of the radioactive substance storage container 100 is filled with helium gas, the control device 41 operates the dry vacuum pump 12 to apply an exhaust pressure from the exhaust line 11 to the inside of the radioactive substance storage container 100. Then, the radioactive substance storage container 100 exhausts helium gas and water vapor remaining inside to the outside, and the internal pressure decreases. And if the internal pressure of the radioactive substance storage container 100 has not dropped to the predetermined pressure, the control device 41 continues to operate the dry vacuum pump 12 and controls the second opening / closing device 52 to open. Then, the exhaust pressure of the exhaust line 11 acts on the gas supply line 51, and outside air is inhaled into the gas supply line 51 and supplied to the exhaust line 11. When the pressure inside the radioactive substance storage container 100 is reduced by the dry vacuum pump 12, the control device 41 does not start supplying carrier gas (air) from the gas supply line 51 to the exhaust line 11 until the pressure inside the radioactive substance storage container 100 drops to a preset predetermined pressure. Based on the pressure inside the radioactive substance storage container 100, the start time of supplying carrier gas (air) from the gas supply line 51 to the exhaust line 11 is set. Specifically, when the pressure inside the radioactive substance storage container 100 is reduced by the dry vacuum pump 12, the control device 41 does not start supplying carrier gas (air) from the gas supply line 51 to the exhaust line 11 until the pressure inside the radioactive substance storage container 100 drops to a preset predetermined pressure. Based on the pressure inside the radioactive substance storage container 100, the start time of supplying carrier gas (air) from the gas supply line 51 to the exhaust line 11 is set. Specifically, when the pressure inside the radioactive substance storage container 100 is reduced by the dry vacuum pump 12, the control device 41 does not start supplying carrier gas (air) from the gas supply line 51 to the exhaust line 11 until the pressure inside the radioactive substance storage container 100 drops to a preset predetermined pressure.

[0058] When the inside of the radioactive substance storage container 100 is filled with helium gas, the control device 41 operates the dry vacuum pump 12 to apply an exhaust pressure from the exhaust line 11 to the inside of the radioactive substance storage container 100. Then, the radioactive substance storage container 100 exhausts helium gas and water vapor remaining inside to the outside, and the internal pressure decreases. And if the internal pressure of the radioactive substance storage container 100 has not dropped to the predetermined pressure, the control device 41 continues to operate the dry vacuum pump 12 and controls the second opening / closing device 52 to open. Then, the exhaust pressure of the exhaust line 11 acts on the gas supply line 51, and outside air is inhaled into the gas supply line 51 and supplied to the exhaust line 11. When the inside of the radioactive substance storage container 100 is filled with helium gas, the control device 41 operates the dry vacuum pump 12 to apply an exhaust pressure from the exhaust line 11 to the inside of the radioactive substance storage container 100. Then, the radioactive substance storage container 100 exhausts helium gas and water vapor remaining inside to the outside, and the internal pressure decreases. And if the internal pressure of the radioactive substance storage container 100 has not dropped to the predetermined pressure, the control device 41 continues to operate the dry vacuum pump 12 and controls the second opening / closing device 52 to open. Then, the exhaust pressure of the exhaust line 11 acts on the gas supply line 51, and outside air is inhaled into the gas supply line 51 and supplied to the exhaust line 11. When the inside of the radioactive substance storage container 100 is filled with helium gas, the control device 41 operates the dry vacuum pump 12 to apply an exhaust pressure from the exhaust line 11 to the inside of the radioactive substance storage container 100. Then, the radioactive substance storage container 100 exhausts helium gas and water vapor remaining inside to the outside, and the internal pressure decreases. And if the internal pressure of the radioactive substance storage container 100 has not dropped to the predetermined pressure, the control device 41 continues to operate the dry vacuum pump 12 and controls the second opening / closing device 52 to open. Then, the exhaust pressure of the exhaust line 11 acts on the gas supply line 51, and outside air is inhaled into the gas supply line 51 and supplied to the exhaust line 11. When the inside of the radioactive substance storage container 100 is filled with helium gas, the control device 41 operates the dry vacuum pump 12 to apply an exhaust pressure from the exhaust line 11 to the inside of the radioactive substance storage container 100. Then, the radioactive substance storage container 100 exhausts helium gas and water vapor remaining inside to the outside, and the internal pressure decreases. And if the internal pressure of the radioactive substance storage container 100 has not dropped to the predetermined pressure, the control device 41 continues to operate the dry vacuum pump 12 and controls the second opening / closing device 52 to open. Then, the exhaust pressure of the exhaust line 11 acts on the gas supply line 51, and outside air is inhaled into the gas supply line 51 and supplied to the exhaust line 11. When the inside of the radioactive substance storage container 100 is filled with helium gas, the control device 41 operates the dry vacuum pump 12 to apply an exhaust pressure from the exhaust line 11 to the inside of the radioactive substance storage container 100. Then, the radioactive substance storage container 100 exhausts helium gas and water vapor remaining inside to the outside, and the internal pressure decreases. And if the internal pressure of the radioactive substance storage container 100 has not dropped to the predetermined pressure, the control device 41 continues to operate the dry vacuum pump 12 and controls the second opening / closing device 52 to open. Then, the exhaust pressure of the exhaust line 11 acts on the gas supply line 51, and outside air is inhaled into the gas supply line 51 and supplied to the exhaust line 11. When the inside of the radioactive substance storage container 100 is filled with helium gas, the control device 41 operates the dry vacuum pump 12 to apply an exhaust pressure from the exhaust line 11 to the inside of the radioactive substance storage container 100. Then, the radioactive substance storage container 100 exhausts helium gas and water vapor remaining inside to the outside, and the internal pressure decreases. And if the internal pressure of the radioactive substance storage container 100 has not dropped to the predetermined pressure, the control device 41 continues to operate the dry vacuum pump 12 and controls the second opening / closing device 52 to open. Then, the exhaust pressure of the exhaust line 11 acts on the gas supply line 51, and outside air is inhaled into the gas supply line 51 and supplied to the exhaust line 11. When the inside of the radioactive substance storage container 100 is filled with helium gas, the control device 41 operates the dry vacuum pump 12 to apply an exhaust pressure from the exhaust line 11 to the inside of the radioactive substance storage container 100. Then, the radioactive substance storage container 100 exhausts helium gas and water vapor remaining inside to the outside, and the internal pressure decreases. And if the internal pressure of the radioactive substance storage container 100 has not dropped to the predetermined pressure, the control device 41 continues to operate the dry vacuum pump 12 and controls the second opening / closing device 52 to open. Then, the exhaust pressure of the exhaust line 11 acts on the gas supply line 51, and outside air is inhaled into the gas supply line 51 and supplied to the exhaust line 11. When the inside of the radioactive substance storage container 100 is filled with helium gas, the control device 41 operates the dry vacuum pump 12 to apply an exhaust pressure from the exhaust line 11 to the inside of the radioactive substance storage container 100. Then, the radioactive substance storage container 100 exhausts helium gas and water vapor remaining inside to the outside, and the internal pressure decreases. And if the internal pressure of the radioactive substance storage container 100 has not dropped to the predetermined pressure, the control device 41 continues to operate the dry vacuum pump 12 and controls the second opening / closing device 52 to open. Then, the exhaust pressure of the exhaust line 11 acts on the gas supply line 51, and outside air is inhaled into the gas supply line 51 and supplied to the exhaust line 11.

[0059] Then, the differential pressure between the downstream side and the upstream side of the dry vacuum pump 12 in the exhaust line 11 becomes small, and the exhaust pressure (vacuum pressure) generated by operating the dry vacuum pump 12 acts appropriately on the inside of the radioactive substance storage container 100 through the exhaust line 11. At this time, since air containing nitrogen gas with a large molecular weight has a property of large intermolecular force, it is easy to obtain a sufficient exhaust speed with the dry vacuum pump 12. Therefore, air is used for the radioactive substance storage. Then, the differential pressure between the downstream side and the upstream side of the dry vacuum pump 12 in the exhaust line 11 becomes small, and the exhaust pressure (vacuum pressure) generated by operating the dry vacuum pump 12 acts appropriately on the inside of the radioactive substance storage container 100 through the exhaust line 11. At this time, since air containing nitrogen gas with a large molecular weight has a property of large intermolecular force, it is easy to obtain a sufficient exhaust speed with the dry vacuum pump 12. Therefore, air is used for the radioactive substance storage. Then, the differential pressure between the downstream side and the upstream side of the dry vacuum pump 12 in the exhaust line 11 becomes small, and the exhaust pressure (vacuum pressure) generated by operating the dry vacuum pump 12 acts appropriately on the inside of the radioactive substance storage container 100 through the exhaust line 11. At this time, since air containing nitrogen gas with a large molecular weight has a property of large intermolecular force, it is easy to obtain a sufficient exhaust speed with the dry vacuum pump 12. Therefore, air is used for the radioactive substance storage. Then, the differential pressure between the downstream side and the upstream side of the dry vacuum pump 12 in the exhaust line 11 becomes small, and the exhaust pressure (vacuum pressure) generated by operating the dry vacuum pump 12 acts appropriately on the inside of the radioactive substance storage container 100 through the exhaust line 11. At this time, since air containing nitrogen gas with a large molecular weight has a property of large intermolecular force, it is easy to obtain a sufficient exhaust speed with the dry vacuum pump 12. Therefore, air is used for the radioactive substance storage. Then, the differential pressure between the downstream side and the upstream side of the dry vacuum pump 12 in the exhaust line 11 becomes small, and the exhaust pressure (vacuum pressure) generated by operating the dry vacuum pump 12 acts appropriately on the inside of the radioactive substance storage container 100 through the exhaust line 11. At this time, since air containing nitrogen gas with a large molecular weight has a property of large intermolecular force, it is easy to obtain a sufficient exhaust speed with the dry vacuum pump 12. Therefore, air is used for the radioactive substance storage. It is used as a carrier gas for discharging the helium gas inside the container 100 and is discharged by air. The helium gas, which is difficult to discharge, can be efficiently discharged.

[0060] At this time, since the check valve 54 is provided in the exhaust line 11, the flow of gas from the vacuum drying unit 21 side to the radioactive substance storage container 100 side is blocked. Therefore, the inflow of air into the inside of the radioactive substance storage container 100 is prevented. Also, since the check valve 55 is provided in the gas supply line 51, the flow of gas from the exhaust line 11 side to the second opening / closing device 52 side is blocked. Therefore, the atmospheric discharge of the gas containing radioactive substances is prevented.

[0061] [Operation and Effect of this Embodiment] The drying device for a radioactive substance storage container according to the first aspect includes an exhaust line 11 for discharging the gas inside the radioactive substance storage container 100, a dry vacuum pump 12 provided in the exhaust line 11, an inert gas supply line 13 for supplying an inert gas to the inside of the radioactive substance storage container 100, and gas supply parts 14, 14A for supplying a carrier gas upstream of the dry vacuum pump 12 in the gas flow direction in the exhaust line 11.

[0062] According to the drying device for a radioactive substance storage container according to the first aspect, with an inert gas supplied to the inside of the radioactive substance storage container 100, the dry vacuum pump 12 is operated to apply an exhaust pressure, and a carrier gas is supplied upstream of the dry vacuum pump 12. As a result, the differential pressure between the downstream side and the upstream side of the dry vacuum pump 12 becomes small, and the vacuum pressure generated by the operation of the dry vacuum pump 12 passes through the exhaust line 11 to the radioactive substance storage container 100. Act appropriately inside. Therefore, the gas containing inert gas remaining inside the radioactive substance storage container 100 can be efficiently discharged. As a result, the structure can be simplified and the enlargement of the device can be suppressed. The drying device for a radioactive substance storage container according to the second aspect, the gas supply parts 14, 14A have gas supply lines 31, 51 whose one end parts are connected to the exhaust line 11 and the other end parts are open to the atmosphere. This is for connecting the gas supply lines 31, 51 to the exhaust line 11, so that air can be supplied to the exhaust line 11 and the structure can be simplified.

[0063] The drying device for a radioactive substance storage container according to the second aspect, the gas supply parts 14, 14A have gas supply lines 31, 51 whose one end parts are connected to the exhaust line 11 and the other end parts are open to the atmosphere. This is for connecting the gas supply lines 31, 51 to the exhaust line 11, so that air can be supplied to the exhaust line 11 and the structure can be simplified. This is for connecting the gas supply lines 31, 51 to the exhaust line 11, so that air can be supplied to the exhaust line 11 and the structure can be simplified. This is for connecting the gas supply lines 31, 51 to the exhaust line 11, so that air can be supplied to the exhaust line 11 and the structure can be simplified.

[0064] The drying device for a radioactive substance storage container according to the third aspect, the gas supply parts 14, 14A have second opening and closing devices 32, 52 provided in the gas supply lines 31, 51. Thereby, only when necessary, the second opening and closing devices 32, 52 can be opened and the carrier gas can be supplied from the gas supply lines 31, 51 to the exhaust line 11. Thereby, only when necessary, the second opening and closing devices 32, 52 can be opened and the carrier gas can be supplied from the gas supply lines 31, 51 to the exhaust line 11. Thereby, only when necessary, the second opening and closing devices 32, 52 can be opened and the carrier gas can be supplied from the gas supply lines 31, 51 to the exhaust line 11.

[0065] The drying device for a radioactive substance storage container according to the fourth aspect, a cold trap 22 for condensing and removing water vapor in the gas by a refrigerant and a filter 23 for removing harmful substances in the gas are provided in the exhaust line 11, and the gas supply line 31 is connected to the downstream side in the gas flow direction of the cold trap 22 and the filter 23 in the exhaust line 11. Thereby, the carrier gas is supplied to immediately before the dry vacuum pump 12 in the exhaust line 11 from the gas supply line 31, and the backflow of the carrier gas to the radioactive substance storage container 100 side can be suppressed. Thereby, the carrier gas is supplied to immediately before the dry vacuum pump 12 in the exhaust line 11 from the gas supply line 31, and the backflow of the carrier gas to the radioactive substance storage container 100 side can be suppressed. Thereby, the carrier gas is supplied to immediately before the dry vacuum pump 12 in the exhaust line 11 from the gas supply line 31, and the backflow of the carrier gas to the radioactive substance storage container 100 side can be suppressed. Thereby, the carrier gas is supplied to immediately before the dry vacuum pump 12 in the exhaust line 11 from the gas supply line 31, and the backflow of the carrier gas to the radioactive substance storage container 100 side can be suppressed. Thereby, the carrier gas is supplied to immediately before the dry vacuum pump 12 in the exhaust line 11 from the gas supply line 31, and the backflow of the carrier gas to the radioactive substance storage container 100 side can be suppressed. Thereby, the carrier gas is supplied to immediately before the dry vacuum pump 12 in the exhaust line 11 from the gas supply line 31, and the backflow of the carrier gas to the radioactive substance storage container 100 side can be suppressed.

[0066] The drying device for a radioactive substance storage container according to the fifth aspect is provided in the exhaust line 11 with a cold trap 22 that condenses and removes water vapor in the gas by a refrigerant, and a filter 23 that removes harmful substances in the gas. The gas supply line 51 is connected to the upstream side in the gas flow direction of the cold trap 22 and the filter 23 in the exhaust line 11, and check valves 54 and 55 are provided to prevent the backflow of the gas from the gas supply line 51 through the exhaust line 11 to the radioactive substance storage container 100 side. Thereby, the check valve 54 can suppress the inflow of air into the interior of the radioactive substance storage container 100, and the check valve 55 can suppress the atmospheric discharge of the gas containing the radioactive substance. and a filter 23 that removes harmful substances in the gas. The gas supply line 51 is connected to the upstream side in the gas flow direction of the cold trap 22 and the filter 23 in the exhaust line 11, and check valves 54 and 55 are provided to prevent the backflow of the gas from the gas supply line 51 through the exhaust line 11 to the radioactive substance storage container 100 side. Thereby, the check valve 54 can suppress the inflow of air into the interior of the radioactive substance storage container 100, and the check valve 55 can suppress the atmospheric discharge of the gas containing the radioactive substance. Thereby, the check valve 54 can suppress the inflow of air into the interior of the radioactive substance storage container 100, and the check valve 55 can suppress the atmospheric discharge of the gas containing the radioactive substance.

[0067] The drying device for a radioactive substance storage container according to the sixth aspect is configured such that the gas passage area of the gas supply line 31 is set smaller than the gas passage area of the exhaust line 11. Thereby, the vacuum pressure generated when the dry vacuum pump 12 operates can be appropriately applied to the interior of the radioactive substance storage container 100 from the exhaust line 11, and an appropriate amount of carrier gas can be supplied to the exhaust line 11. and an appropriate amount of carrier gas can be supplied to the exhaust line 11. The drying device for a radioactive substance storage container according to the sixth aspect is configured such that the gas passage area of the gas supply line 31 is set smaller than the gas passage area of the exhaust line 11. Thereby, the vacuum pressure generated when the dry vacuum pump 12 operates can be appropriately applied to the interior of the radioactive substance storage container 100 from the exhaust line 11, and an appropriate amount of carrier gas can be supplied to the exhaust line 11. The drying device for a radioactive substance storage container according to the sixth aspect is configured such that the gas passage area of the gas supply line 31 is set smaller than the gas passage area of the exhaust line 11. Thereby, the vacuum pressure generated when the dry vacuum pump 12 operates can be appropriately applied to the interior of the radioactive substance storage container 100 from the exhaust line 11,

[0068] The drying device for a radioactive substance storage container according to the seventh aspect includes a control device 41 that controls the supply of the carrier gas from the gas supply units 14 and 14A to the exhaust line 11. Thereby, the supply of the carrier gas to the exhaust line 11 can be started at an appropriate timing. The drying device for a radioactive substance storage container according to the seventh aspect includes a control device 41 that controls the supply of the carrier gas from the gas supply units 14 and 14A to the exhaust line 11. Thereby, the supply of the carrier gas to the exhaust line 11 can be started at an appropriate timing. The drying device for a radioactive substance storage container according to the seventh aspect includes a control device 41 that controls the supply of the carrier gas from the gas supply units 14 and 14A to the exhaust line 11. Thereby, the supply of the carrier gas to the exhaust line 11 can be started at an appropriate timing.

[0069] The drying device for a radioactive substance storage container according to the eighth aspect is such that the control device 41, when the pressure inside the radioactive substance storage container 100 does not decrease to a predetermined pressure set in advance, the gas supply unit 1 Start supplying the carrier gas from 4,14A to the exhaust line 11. As a result, when it becomes difficult to exhaust the gas inside the radioactive substance storage container 100 and the internal pressure reaches a predetermined pressure but does not reach it, by supplying the carrier gas to the exhaust line 11 at this time, the exhaust of the gas inside the radioactive substance storage container 100 can be promoted.

[0070] In the drying device for the radioactive substance storage container according to the ninth aspect, the carrier gas has a gas with a larger molecular weight than the inert gas. As a result, since the gas with a larger molecular weight has a large intermolecular force property, it is easy to obtain a sufficient exhaust speed with the dry vacuum pump 12. Therefore, the inert gas inside the radioactive substance storage container 100 can be efficiently exhausted by the carrier gas.

[0071] The drying method for the radioactive substance storage container according to the tenth aspect includes a step of supplying a predetermined amount of inert gas to the inside of the radioactive substance storage container 100, a step of exhausting the gas containing the inert gas inside the radioactive substance storage container 100 from the exhaust line 11 by the dry vacuum pump 12, and a step of supplying the carrier gas to the upstream side in the gas flow direction from the dry vacuum pump 12 in the exhaust line 11 when the pressure or pressure correlation value inside the radioactive substance storage container 100 drops to a predetermined pressure set in advance.

[0072] According to the drying method for the radioactive substance storage container according to the tenth aspect, the differential pressure between the downstream side and the upstream side of the dry vacuum pump 12 becomes small, and the vacuum pressure generated by the operation of the dry vacuum pump 12 acts appropriately on the inside of the radioactive substance storage container 100 through the exhaust line 11. Therefore, the gas containing the inert gas remaining inside the radioactive substance storage container 100 can be efficiently exhausted. As a result, the structure can be simplified and the enlargement of the device can be suppressed.

[0073] In addition, in the above-described embodiment, the gas supply lines 31 and 51 for sucking external air are provided as the gas supply units 14 and 14A, but the present invention is not limited to this configuration. As the gas supply unit, for example, a gas cylinder or a blower may be connected to the other ends of the gas supply lines 31 and 51. Alternatively, a blower or the like for supplying a carrier gas may be directly provided in the exhaust line 11.

[0074] Also, in the above-described embodiment, the position of the gas supply units 14 and 14A may be any position as long as it is in the exhaust line 11 between the radioactive substance storage container 100 and the dry vacuum pump 12.

Explanation of Reference Numerals

[0075] 10, 10A Drying device for radioactive substance storage container 11 Exhaust line 12 Dry vacuum pump 13 Inert gas supply line 14, 14A Gas supply unit 21 Vacuum drying unit 22 Cold trap 23 Filter 24 Refrigerant supply line 25 Three-way valve 26 Inert gas supply source 27 First opening / closing device 31, 51 Gas supply line 32, 52 Second opening / closing device 33, 53 Connection part 41 Control device 42 Pressure gauge 54, 55 Check valve​​​​​​ 100 Radioactive material storage container 101 Barrel part 102 Lid part 103 Vent line 104 Drain line 111 Decontamination pit 112 Work floor

Claims

1. An exhaust line for discharging gas inside a radioactive substance storage container, A dry vacuum pump provided in the exhaust line, An inert gas supply line connected upstream of the dry vacuum pump in the gas flow direction in the exhaust line to supply inert gas to the inside of the radioactive substance storage container, A gas supply unit for supplying carrier gas downstream of the connection part of the inert gas supply line in the exhaust line in the gas flow direction and upstream of the dry vacuum pump in the gas flow direction, A drying device for a radioactive substance storage container comprising the above.

2. The gas supply unit has a gas supply line with one end connected to the exhaust line and the other end open to the atmosphere, The drying device for a radioactive substance storage container according to Claim 1.

3. The gas supply unit has an opening / closing device provided in the gas supply line, The drying device for a radioactive substance storage container according to Claim 2.

4. The exhaust line is provided with a cold trap for condensing and removing water vapor in the gas by a refrigerant and a filter for removing harmful substances in the gas, and the gas supply line is connected downstream of the cold trap and the filter in the exhaust line in the gas flow direction, The drying device for a radioactive substance storage container according to Claim 2 or Claim 3.

5. The exhaust line is provided with a cold trap for condensing and removing water vapor in the gas by a refrigerant and a filter for removing harmful substances in the gas, the gas supply line is connected upstream of the cold trap and the filter in the exhaust line in the gas flow direction, and a check valve is provided to prevent backflow of gas from the gas supply line through the exhaust line to the radioactive substance storage container side, The drying device for a radioactive substance storage container according to Claim 2 or Claim 3.

6. The gas passage area of the gas supply line is set smaller than the gas passage area of the exhaust line, The drying device for a radioactive substance storage container according to any one of Claims 2 to 5.

7. It has a control device for controlling the supply of carrier gas from the gas supply unit to the exhaust line, The drying device for a radioactive substance storage container according to any one of Claims 1 to 6.

8. When the pressure inside the radioactive substance storage container does not drop to a preset predetermined pressure, the control device starts supplying carrier gas from the gas supply unit to the exhaust line. The drying device for a radioactive substance storage container according to claim 7.

9. The carrier gas has a gas with a molecular weight larger than that of the inert gas. The drying device for a radioactive substance storage container according to any one of claims 1 to 8.

10. A step of supplying a predetermined amount of inert gas through an exhaust line into the radioactive substance storage container; A step of exhausting the gas containing the inert gas inside the radioactive substance storage container from the exhaust line by a dry vacuum pump; A step of supplying carrier gas on the downstream side in the gas flow direction from the supply position of the inert gas in the exhaust line and on the upstream side in the gas flow direction from the dry vacuum pump when the pressure or pressure correlation value inside the radioactive substance storage container does not drop to a preset predetermined pressure; A method for drying a radioactive substance storage container, comprising the steps above.

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