JP4102400B2 - Device decontamination method and device decontamination device - Google Patents

Description

  The present invention relates to a decontamination method for equipment that handles heavy water containing tritium and a decontamination apparatus for the equipment.

When heavy water (D ₂ O) is used as a neutron moderator in a nuclear facility, tritium (T, tritium), which is a radioactive substance, is generated and accumulated in heavy water. Such tritium is present in heavy water mainly in the form of tritium water (T ₂ O, TDO). And at the time of periodic inspection, repair, dismantling, etc. of equipment that handles such heavy water, so-called tritium decontamination work that sufficiently removes tritium from the inside of such equipment is performed in order to improve the work environment. Necessary.

Conventionally, as such decontamination work, first, after removing heavy water from the inside of the device, dry air is supplied into the device, and liquid heavy water containing tritium remaining in the device is evaporated from the inside of the device. Remove. In the process of supplying the dry air, it is determined that the evaporation of heavy water in the liquid state is completed when the radiation dose in the air in the device reaches equilibrium or becomes lower than a predetermined set value. Air containing light water (H ₂ O) water vapor is supplied to the inside, and tritium in heavy water adsorbed on the inner surface of the equipment is recovered in the air by isotope exchange reaction with light water, and the tritium is decontaminated from inside the equipment. (See Patent Document 1).
Japanese Patent Laid-Open No. 11-281792

  However, in the conventional method, a great amount of time may be required for decontamination of tritium in the isotope exchange reaction, and in this case, a large amount of waste water containing tritium has been discharged.

  This invention is made | formed in view of the said subject, and it aims at providing the decontamination method and decontamination apparatus of the apparatus which can perform decontamination efficiently and can reduce the amount of waste_water | drain.

  The equipment that handles heavy water inside the reactor facility has a complicated shape and structure, and there are many reservoirs where liquid heavy water tends to accumulate, and the evaporation rate of heavy water from these reservoirs is slow. It takes a considerable amount of time to dry the heavy water in the pool with dry air. And in the conventional method, based on the radiation dose of air in the equipment, the timing of the transition from the drying process by the supply of dry air to the isotope exchange process by the supply of water vapor is determined. Since the evaporation rate of heavy water is slow and it is difficult for the radiation dose of air to rise, there is a case where the process proceeds to the isotope exchange process on the assumption that the evaporation of heavy water in the liquid state in the apparatus is completed even though heavy water remains. Then, by performing the isotope exchange process while liquid heavy water remains in the apparatus in this way, it takes a lot of time for decontamination of tritium by the isotope exchange reaction, and a large amount of water containing tritium is discharged. Was invited.

Therefore, the decontamination method for equipment according to the present invention is a decontamination method for equipment that handles heavy water containing tritium inside. In the decontamination method for equipment, dry gas is supplied to the inside of the equipment to evaporate heavy water containing tritium and at the same time evaporate heavy water. A dry gas supply step for discharging the gas containing the gas from the device, a vacuum drawing step for evacuating the inside of the device after the dry gas supply step, and obtaining a pressure inside the vacuumed device based on the pressure A steam supply determination step for determining whether or not to supply a gas containing light water vapor to the inside of the device, and after it has been decided to supply a gas containing light water vapor to the inside of the device in the water vapor supply determination step And a water vapor supply step of supplying a gas containing light water vapor to the inside of the device.

  According to the decontamination method of the present invention, the inside of the apparatus is evacuated after the dry gas supply step. At this time, the pressure in the device reached by evacuation differs greatly depending on whether or not liquid heavy water remains in the device. For this reason, it is possible to easily determine whether or not heavy liquid water remains in the device based on the pressure in the device, and after confirming that heavy water does not remain, The decision to supply the gas containing can be made. In addition, since water vapor is introduced into the apparatus and an isotope exchange reaction is performed in a state where liquid heavy water does not remain in the apparatus, the time required for the isotope exchange is reduced, and the wastewater discharged at this time is reduced. The amount is reduced.

  Here, in the steam supply determination step, it is preferable to determine the supply of light water steam to the inside of the device when the pressure is lower than a predetermined reference value.

  When liquid heavy water remains in the device, it is difficult to depressurize the device to a vapor pressure lower than this heavy water. Therefore, if the pressure in the device falls below a reference value corresponding to the vapor pressure of heavy water, it can be suitably determined that liquid heavy water containing tritium does not remain in the device, and whether or not to supply water vapor is determined. Easy to determine.

  Moreover, it is preferable to perform a drying process again, when it determines not to supply light water vapor | steam inside an apparatus in a water vapor | steam supply determination process.

  As a result, when liquid heavy water remains in the device, the drying process is performed again, and after removing the liquid heavy water remaining in the device reliably, water vapor is supplied to cause isotope exchange. Can do.

  Here, in the dry gas supply step, it is preferable to further heat the device.

  By heating at least a part of the device, for example, a portion where liquid heavy water is likely to remain, evaporation of liquid heavy water is promoted, and the time required for the dry gas supply process can be shortened. Is done.

  In the water vapor supply step, it is preferable that the dew point of the gas containing the water vapor of light water supplied to the inside of the device is -5 to -15 ° C.

  According to this, the isotope exchange reaction in the apparatus is efficiently performed, and the time required for the isotope exchange can be further reduced.

  Here, it is considered that the isotope exchange reaction caused by the introduction of light water vapor is driven by the difference between the ratio of tritium and light hydrogen in the gas phase and the ratio of tritium and light hydrogen in the adsorption phase. It is also considered that it takes a relatively long time for this isotope exchange reaction to reach equilibrium.

  Therefore, the water vapor supply step includes a supply step of supplying a gas containing a predetermined amount of light water vapor inside the device, and a tritium concentration acquisition step of acquiring information on the tritium concentration in the gas inside the device supplied in the supply step. And a condensing step of condensing the water vapor in the gas and recovering it as a liquid when the concentration of tritium in the gas becomes higher than a predetermined value.

  Thereby, after supplying a predetermined amount of water vapor, the concentration of tritium in the gas is monitored, and this concentration is higher than the predetermined value, that is, the ratio of tritium / light hydrogen in the gas is sufficiently high, so that the isotope exchange reaction is performed. After it becomes difficult to propel, the water vapor in the gas is condensed and recovered. For this reason, compared with always condensing and collecting water vapor containing tritium, the amount of waste water containing tritium can be further reduced.

An apparatus for decontamination of an apparatus according to the present invention is an apparatus for decontamination of equipment that handles heavy water containing tritium, and supplies heavy gas containing tritium at the same time as supplying dry gas to the inside of the equipment to evaporate heavy water. Dry gas supply means for discharging the gas from the equipment, vacuum suction means for evacuating the inside of the equipment, pressure acquisition means for obtaining the pressure inside the evacuated equipment, and water vapor of light water inside the equipment. And a water vapor supply means for supplying a gas containing the water vapor.

  According to the device decontamination apparatus of the present invention, the inside of the device can be evacuated after the dry gas supply step. At this time, the pressure in the device reached by evacuation differs greatly depending on whether or not liquid heavy water remains in the device. For this reason, based on the pressure in the equipment acquired by the pressure acquisition means, it can be determined whether heavy water in the liquid state remains in the equipment, and after confirming that there is no heavy water remaining. It can be determined that a gas containing water vapor is supplied into the device. Then, since no heavy water in the liquid state remains in the equipment, water vapor can be introduced into the equipment to perform the isotope exchange reaction, so the time required for the isotope exchange is reduced, and the drainage discharged at this time is reduced. The amount is reduced.

  Here, the dry gas supply means is provided with a cylindrical body that is filled with an adsorbent and rotated about its axis, and is fixed among the adsorbent that rotates by rotation within the cylindrical body. A gas containing heavy water vapor discharged from the equipment is supplied to the adsorbent passing through the region to adsorb the water vapor to obtain a dry gas, and the adsorbent is spaced apart from the first region in the rotation direction and fixed. It is preferable to regenerate the adsorbent by supplying a regeneration gas to the adsorbent passing through the second region.

  Thus, it has a cylindrical body that holds the adsorbent inside, and by rotating this cylindrical body, it is possible to continuously perform gas adsorption and adsorbent regeneration without switching operation. The dry gas supply means can be reduced in size as compared with conventional dry gas supply means such as a heating regeneration system and a pressure swing regeneration system having two adsorption towers. For this reason, while being able to reduce the installation space of a decontamination apparatus, equipment cost can be reduced. A part of the obtained dry gas can be heated and used as a regeneration gas.

  Moreover, it is preferable to provide the airtight container which accommodates a cylindrical body in an airtight state inside, and the secondary collection | recovery means which collect | recovers the water vapor | steam in an airtight container.

  When drying a gas using the rotating cylindrical body as described above, it is difficult to completely seal the gas containing tritium, and the gas containing tritium may leak from the cylindrical body to the outside. . Therefore, the tritium is prevented from leaking to the outside by accommodating the cylindrical body in the sealed container and collecting the water vapor containing tritium leaked in the sealed container by the secondary recovery means.

  In the present invention, since the inside of the device is evacuated after the dry gas supply step, it is easy to determine whether liquid heavy water remains inside the device based on the pressure inside the evacuated device. It is possible to determine whether or not to supply water vapor to the inside of the device after reliably grasping that no heavy water remains. Then, since no heavy water in the liquid state remains in the apparatus, water is introduced into the apparatus to perform the isotope exchange reaction, so that the time required for the isotope exchange is reduced, and the drainage discharged at this time The amount of is reduced.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a device decontamination method and a device decontamination apparatus according to the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a schematic configuration diagram illustrating a device 10 that is a target for decontamination of tritium and a decontamination apparatus 100 that decontaminates the device 10 according to the present embodiment.

  Although not shown in detail, the device 10 handles heavy water used as a moderator in the heavy water reactor, and includes a pump, piping, and the like.

The decontamination device 100 is a device that removes tritium (T) from the device 10. The decontamination device 100 mainly performs drying by adsorbing water vapor of heavy water containing tritium from the air discharged through the device 10 and drying the air. A device 20, a fan 30 that supplies air dried by the drying device 20 to the device 10, a vacuum pump (evacuation means) 40 for exhausting gas in the device 10, and light water (H ₂ in the device 10). A humidifier (water vapor supply means) 50 for introducing a gas containing water vapor of O) and a condenser 60 for condensing the water vapor adsorbed by the drying device 20 are provided. Most of tritium exists as tritium water (T ₂ O, TDO).

  The drying device 20 includes a drying unit 20a and a regeneration unit 20b. The drying unit 20a is connected to the device 10 via the line L1, introduces air discharged from the device 10 containing heavy water vapor containing tritium, and makes this air contact with the adsorbent in the drying unit 20a. Adsorbs heavy water vapor containing tritium in the air to dry the air. As this adsorbent, for example, silica gel, activated carbon, and molecular sieve can be used.

  The drying unit 20a is further connected to the fan 30 via a line L2, and the fan 30 is connected to the device 10 via a line L3. And the fan 30 supplies the air dried with the drying apparatus 20 to the apparatus 10, and contains the tritium water which adheres in the apparatus 10 or adheres to the oxide film formed in the apparatus 10, and remains. The heavy water in the liquid state is evaporated to move to the air side, and the inside of the device 10 is dried. Here, the line L1, the line L2, and the line L3 are respectively provided with valves 51, 52, and 53 capable of controlling air flow / blocking. The drying device 20 and the fan 30 constitute the dry gas supply means 15.

  On the other hand, a line L4 branched from the drying device 20 side with respect to the valve 52 in the line L2 is connected to the regeneration unit 20b. The line L4 is connected to a heater 23 that heats the dried air introduced from the line L2, and a fan 24 that supplies the heated dry air to the regeneration unit 20b. The regenerator 20b and the condenser 60 are connected by a line L5.

  In the regeneration unit 20b, the adsorbent that has adsorbed water vapor in the drying unit 20a comes into contact with high-temperature dry air as a regeneration gas introduced through the line L4, and the tritium water adsorbed on the adsorbent is removed. The contained heavy water is released from the adsorbent as water vapor, and the adsorbent is regenerated. The regenerated adsorbent is dried again by the drying unit 20a.

  The condenser 60 introduces the water vapor of heavy water containing tritium released from the adsorbent through the line L5, cools the water vapor by water cooling or the like, condenses it into a liquid, and collects it outside via the line L6. At the same time, the air from which moisture has been removed is returned to the portion closer to the drying device 20 than the valve 51 in the line L1 via the line L7.

  The vacuum pump 40 is connected to the device 10 via a line L10 having a valve 55. Further, a pressure gauge (pressure acquisition means) 42 for measuring the pressure in the device 10 is connected to the line L10.

The humidifier 50 is connected to the line L3 by a line L9 including a valve 57, and allows a predetermined amount of light water (H ₂ O) water vapor to be supplied to the gas sent to the device 10 by the fan 30.

  The line L3 is connected to a line L10 including a sampling valve 58 for sampling the gas flowing through the line L3 in order to measure the concentration of tritium in the air flowing through the line L3.

  Further, the decontamination apparatus 100 includes a line L12 that branches from the device 10 side with respect to the valve 51 in the line L1, joins the fan 30 side with respect to the valve 52 in the line L2, and is connected to the valve 59 in the middle. ing. This line L12 enables the exhaust gas from the device 10 to be circulated again to the device 10 by the fan 30 without passing through the drying device 20.

  Moreover, the heater 10 is installed in the apparatus 10 in the site | part where heavy water of a liquid state tends to remain | survive which can raise the temperature of the said site | part.

  Next, a decontamination method in the decontamination system according to the present embodiment will be described with reference to FIGS. 1 and 2.

  In advance, the valve 55, the valve 57, the valve 58, and the valve 59 are closed, and the valve 51, the valve 52, and the valve 53 are opened. In addition, it is assumed that most of the heavy water handled by the device 10 is extracted through a drain valve or the like (not shown).

  First, in order to evaporate and remove heavy water containing tritium remaining in the liquid state in the device 10, dry air is supplied into the device 10 in step S <b> 101. Specifically, the fan 30 is driven while operating the drying device 20 and the condenser 60, and the dry air from the drying device 20 is supplied to the device 10 to evaporate heavy water containing tritium and collect it on the air side. The water vapor contained in the air discharged from the device 10 is absorbed by the drying unit 20a of the drying device 20, and this air is again sent to the device 10 as dry air. Further, the water vapor absorbed by the drying unit 20a is released by the regenerating unit 20b, and the discharged water vapor is covered with the condenser 60 to recover heavy water containing tritium water as a liquid.

  In this step, since it is a so-called closed cycle operation in which drying air circulates, tritium leakage in the drying operation is reduced.

  After such a dry air supply process is performed for a predetermined time, the supply of this dry air is once ended, and a vacuuming process is performed in step S105. In this evacuation step, the valve 51, the valve 52, and the valve 53 are closed, and then the valve 55 is opened and the vacuum pump 40 is operated to discharge gas such as air in the device 10 to reduce the pressure in the device 10. Apply vacuum.

  Then, after performing the evacuation operation for a predetermined time, in step S105, the instruction value of the pressure gauge 42 is referred to and it is determined whether or not to start the water vapor supply process based on this pressure. Here, if liquid heavy water remains in the device 10, it is difficult to depressurize the device 10 to a pressure lower than the vapor pressure of the heavy water, and based on the pressure in the device 10 at the time of depressurization. It is possible to suitably determine whether liquid heavy water remains in the device. And when it is judged that heavy water does not remain | survive, it determines to perform a water vapor | steam supply process.

  Specifically, if the pressure in the device 10 exceeds a reference value set as the same level as the saturated vapor pressure of water, liquid heavy water still exists in the device 10 in the device 10. The process proceeds to step S108 to perform a further dry gas supply process.

  In step S108, the valve 55 is closed again, the valves 51 to 53 are opened, the fan 30, the drying device 20, and the condenser 60 are operated to supply dry air into the device 10 and the liquid remaining in the device 10 The heavy water in the state is further evaporated and recovered. At this time, the heater 12 of the device 10 is operated to increase the temperature of the portion where heavy water is likely to remain in the device 10 to increase the temperature of the heavy water to promote evaporation. And after performing this operation for a predetermined time, it returns to step S103 again and vacuuming is performed, and it is judged whether a water vapor | steam supply process is performed in step S105.

  On the other hand, when the pressure in the device 10 is equal to or lower than the above-described reference value in step S105, there is no liquid heavy water in the device 10, and the process proceeds to an isotope exchange reaction process in which water vapor is supplied into the device 10. It is determined to shift, and the process proceeds to step S107.

In step S107, the valve 55 is closed and the valve 53 and the valve 59 are opened to form a closed loop of the device 10, the line L1, the line L12, the line L2, and the line L3. Further, the valve 57 is opened, air containing a predetermined amount of light water (H ₂ O) water vapor is supplied from the humidifier 50 into the closed loop, and then the valve 57 is closed. Here, it is preferable to set the water vapor amount of light water so that the dew point of the air in the closed loop is −5 to −15 ° C. so that the isotope exchange reaction described later can be performed in a short time.

  In step S109, the fan 30 is driven to circulate air containing light water vapor in the closed loop of the device 10 for a predetermined time. Thereby, the tritium in the heavy water adsorbed on the inner surface of the device 10 and the light water in the circulated air perform isotope exchange, and the adsorbed tritium is recovered in the air.

  The isotope exchange reaction is considered to generate propulsive force due to the difference between the ratio of tritium and light water in the adsorbed water adsorbed on the inner surface of the device 10 and the ratio of tritium and light water in the water vapor in the air. It is done. And if the ratio of tritium in the water vapor | steam in air becomes high, an isotope exchange reaction will hardly advance.

  Therefore, after a predetermined time has elapsed since the start of the circulation of the humidified air, in step S111, the tritium concentration in the circulating air is measured to determine whether the tritium concentration is higher than a predetermined reference concentration.

When the concentration of tritium on the air side is higher than a predetermined reference value, it is considered that the isotope exchange reaction has hardly progressed, and it can be determined that re-isotope exchange by addition of new water vapor is necessary. Here, as the predetermined reference value, for example, a tritium concentration corresponding to the case where the ratio of light hydrogen to tritium in the air is 1: 5 × 10 ⁻⁵ is preferable.

  If it is determined in step S111 that the addition of water vapor is necessary again, the process proceeds to step S115, the valve 59 is closed and the valves 51 and 52 are opened, and the drying device 20 and the condenser 60 are operated. The water vapor of light water containing tritium in the circulating air is condensed and discharged to the outside. Then, returning to step S107, air containing light water vapor is reintroduced into the closed loop, and air containing light water vapor is circulated in step S109 to perform the isotope exchange reaction of tritium adsorbed on the device 10. Do it again.

  On the other hand, if the tritium concentration in the air is equal to or lower than the predetermined reference value in step S111, the process proceeds to step S113, where it is determined whether the tritium concentration in the circulating air has reached a steady state. Specifically, each of the tritium concentrations is measured at different times, and it can be determined that a steady state has been reached if the concentration change during this period is equal to or less than a predetermined value.

  Here, if it is determined that the tritium concentration has not reached a steady state, the process returns to step S109, and this air circulation is continued again to continue further isotope exchange reaction.

  On the other hand, if it is determined that the tritium concentration has reached a steady state, it can be determined that the tritium adsorbed on the device 10 has been sufficiently removed, and thus the process proceeds to step S117 and the valve 59 is closed. The valve 51 and the valve 52 are opened, the drying device 20 and the condenser 60 are operated, and water vapor in the circulating air is condensed and discharged to the outside. Thereby, the water vapor of light water containing tritium is removed from the inside of the device 10, and the decontamination of the device 10 is completed.

  Here, the usefulness of the decontamination method as described above is verified based on the result of decontamination of the equipment using air having a dew point of −15 ° C.

The tritium contained in the oxide film on the inner surface of this device was 2 × 10 ⁵ Bq / cm ² , and the tritium adsorbed on the oxide film was about 200 Bq / cm ² . Tritium contained in the oxide film was dried in about 2 hours by ventilating air having a dew point of −15 ° C. through the decontamination apparatus having the above-described configuration. Then, after grasping that the inside of the device was dried by evacuation, the isotope exchange in the device was performed. To decontaminate tritium which has been adsorbed on the oxide film in the isotope exchange reaction from 200 Bq / cm ² until 20Bq / cm ² took 100 hours.

In order to decontaminate the inner surface of the apparatus to 200 Bq / cm ² or less, it is necessary to promote isotope exchange reaction by contacting with water molecules in the air, but the absolute amount of tritium is small. When humidified air is circulated and passed through the dehumidifying agent as in the prior art, a large amount of waste water containing tritium at a low concentration is generated when the dehumidifying agent is regenerated. On the other hand, when decontamination is performed by the method according to the present embodiment, necessary water can be supplied while monitoring the tritium concentration, and therefore, generation of excess drainage can be prevented. Further, in the method according to the present embodiment, since the inside of the apparatus is confirmed by evacuation and then the isotope exchange is performed, the efficiency is high.

  As described above, in the present embodiment, the inside of the device 10 is evacuated after the dry gas supply step. At this time, the pressure in the device 10 reached by evacuation differs greatly depending on whether or not liquid heavy water remains in the device 10. For this reason, it is possible to easily determine whether or not liquid heavy water remains in the device 10 based on the pressure in the device 10, and after confirming that no heavy water remains in the device 10, It is possible to decide to supply steam. Then, since water vapor is introduced and an isotope exchange reaction is performed in the device 10 in a state where liquid heavy water does not remain in the device 10, the time required for the isotope exchange is reduced, and is discharged at this time. The amount of drainage is reduced.

  In the water vapor supply step, the concentration of tritium in the gas is monitored after supplying a predetermined amount of water vapor, and this concentration is higher than a predetermined value, that is, the ratio of tritium / light hydrogen in the gas is sufficiently high. Since it is difficult to promote the body exchange reaction, water vapor in the gas is condensed and recovered. For this reason, compared with always condensing and recovering water vapor containing tritium, the amount of waste water containing tritium can be further reduced.

  Next, the decontamination apparatus 200 according to the second embodiment will be described with reference to FIG. The decontamination apparatus 200 of this embodiment is different from the decontamination apparatus 100 of the first embodiment in that a drying apparatus 80 having a drying rotor (tubular body) 82 is provided instead of the drying apparatus 20. is there. The drying device 80 and the fan 30 constitute the drying gas supply means 15.

  The drying device 80 includes a main drying device 81 stored in an airtight state in a sealed glove box (sealed container) 89, and a sub-drying device (secondary recovery device) 90 connected to the sealed glove box 89. ing.

  The main drying device 81 sends dry air to the device 10 and dries air containing water vapor from the device 10. The main drying device 81 has a cylindrical shape and is filled with an adsorbent 82 a such as silica gel and the central axis of the cylinder. A drying rotor 82 that can rotate about 83 is provided. The drying rotor 82 is rotated by a motor 91 via a rotating belt 92 that is stretched around the outer periphery of the cylinder. Further, the drying rotor 82 has a honeycomb wall (not shown) extending in the direction of the shaft 83, and the adsorbent 82a is held by the honeycomb wall and air can be circulated in the axial direction. It has become.

  The line L1 of the decontamination apparatus 200 is configured to remove water vapor discharged from the apparatus 10 with respect to the adsorbent passing through the fixed first region 82b on the upper side of the adsorbent 82a that rotates by the rotation of the drying rotor 82. It is connected with respect to the drying rotor 82 so as to supply the contained gas. The line L2 is connected to the drying rotor 82 so as to collect the air introduced from the line L1 and in contact with the adsorbent 82a in the first region 82b of the drying rotor 82 and to be directed to the fan 30. .

  Moreover, the main drying apparatus 81 is provided with the line L4 which branched from the line L2 similarly to 1st embodiment, and to which the heater 23 similar to 1st embodiment was connected in the middle. The end of the line L4 supplies high-temperature dry air to the adsorbent passing through the fixed second region 82c on the lower side of the adsorbent 82a that rotates by the rotation of the drying rotor 82. The adsorbent is regenerated by being connected to the drying rotor 82. In order to efficiently regenerate the adsorbent, the direction of air supplied to the adsorbent 82a of the drying rotor 82 by the line 1 and the direction of air supplied to the adsorbent 82a of the dry rotor 82 by the line L4 are reversed. Direction, and counter-current regeneration is possible. Here, the temperature of the high-temperature dry air as the regeneration gas introduced into the second region 82c is higher than that of the air containing water vapor introduced into the first region 82b by the heater 23.

  The main drying device 81 includes a line L7 that receives air introduced from the line L4 and containing water vapor released from the adsorbent 82a in the second region 82c of the drying rotor 82 by the regeneration operation. This line L7 merges with the line L1, and has a condenser 60 including a fan 24 similar to the first embodiment and a condensed water recovery line L6 similar to the first embodiment. Such a main drying device 81 is capable of drying air to a dew point of about −20 ° C.

  Further, the sub-drying device 90 is a product that condenses and collects water vapor containing tritium that leaks in a slight amount from the main drying device 81 into the sealed glove box 89. The sub-drying device 90 and the main drying device 81 are connected by a line L15 for introducing air from the sealed glove box 89 and a line L16 for returning the air dried by the sub-drying device 90 into the sealed glove box 89. . Such a sub-drying device 90 has two towers filled with an adsorbent, a heat regeneration type (drying device) that performs drying on one side and regeneration on the other side, or pressure regeneration. A (pressure swing) type drying apparatus can be used. The sub-drying device 90 is preferably capable of drying air to a dew point of about −60 ° C.

  Also in the decontamination apparatus 200 of this embodiment, the apparatus 10 can be decontaminated suitably by the main drying apparatus 81 in the same procedure as the first embodiment.

  In addition to this, the main drying apparatus 81 as in the present embodiment can continuously perform adsorption and regeneration without switching operation by rotating the drying rotor 82, and can perform two conventional adsorptions. Compared to drying equipment using a heating regeneration system or pressure swing regeneration system that has towers and alternately switches between adsorption and regeneration in each tower, it is easy to operate and can be reduced in size and equipment costs Becomes lower. This is particularly noticeable when the device 10 is large and the flow rate of dry air increases.

  Specifically, in a thermal swing type drying apparatus having two adsorption towers, the two towers are alternately switched between regeneration and drying, so that the apparatus becomes large and the operation becomes complicated. Further, when the tower is enlarged, the pressure loss when the gas is circulated increases, the blower head becomes high, and the apparatus is further enlarged. On the other hand, in a pressure swing regeneration type drying apparatus having two adsorption towers, switching between the two towers is the same, but regeneration is performed by pressure swing, so the regeneration time is reduced compared to the thermal swing type. The tower itself is miniaturized. However, since high pressure air is required, a compressor is required, and a compressor with high sealing performance increases the equipment size and equipment cost.

  Further, in the main drying device 81 having a rotating part such as the drying rotor 82, it is difficult to completely seal the air flowing in the drying rotor 82, that is, the water vapor of heavy water containing tritium, and in particular, the shaft seal. The water vapor of heavy water containing tritium slightly leaks into the sealed glove box 89 from the part or the like. However, in the decontamination apparatus 200 of the present embodiment, the main drying device 81 is sealed in the sealed glove box 89, and the auxiliary drying device 90 is connected to the sealed glove box 89, so that The leaked tritium is collected by the auxiliary drying device 90 and does not leak outside. Here, the amount of water vapor such as tritium leaking from the main drying device 81 is very small, and the capacity of the sub-drying device 90 is very small, about 1/10 or less of the amount recovered by the main drying device 81. Therefore, a sufficiently small and low-cost drying device can be adopted as the sub-drying device 90, and the entire decontamination device 200 can be reduced in size and cost.

  In addition, nuclear facilities that handle heavy water are often equipped with a small two-column drying device in advance, and by using such a drying device as the sub-drying device 90, this embodiment can be made at a lower cost. And it can be implemented in a space-saving manner.

  In addition, this invention is not limited to the said embodiment, It can take a various deformation | transformation aspect.

  For example, in the above embodiment, heating by the heater 12 is performed for the first time in the second drying step (step S108), but may be performed in the first drying step (step S101).

  In this embodiment, dry air is used as the drying gas, but other dry gases such as dry nitrogen may be used.

It is a figure which shows the decontamination apparatus which concerns on 1st embodiment. It is a figure which shows the flow of the decontamination using the decontamination system of FIG. It is a figure which shows the decontamination apparatus which concerns on 2nd embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Apparatus, 15 ... Dry gas supply means, 40 ... Vacuum pump (evacuation means), 42 ... Pressure gauge (pressure acquisition means), 50 ... Humidifier (water vapor supply means), 82 ... Dry rotor (tubular body) , 82a ... adsorbent, 82b ... first region, 82c ... second region, 89 ... sealed glove box (sealed container), 90 ... sub-drying device (secondary recovery means), 100, 200 ... decontamination device.

Claims (9)

In the decontamination method for equipment that handles heavy water containing tritium internally,
A dry gas supply step of supplying dry gas into the device to evaporate heavy water containing tritium and simultaneously discharging the gas containing evaporated heavy water from the device ;
A vacuuming step of evacuating the inside of the device after the dry gas supply step;
Obtaining a pressure inside the evacuated device, and determining whether to supply a gas containing light water vapor to the inside of the device based on the pressure;
A steam supply step of supplying a gas containing light water vapor into the inside of the device after it is decided to supply a gas containing light water vapor inside the device in the water vapor supply determining step,
A method for decontamination of equipment, comprising:   2. The device decontamination method according to claim 1, wherein, in the water vapor supply determination step, when the pressure is lower than a predetermined reference value, supply of light water vapor to the inside of the device is determined.   3. The device decontamination method according to claim 1, wherein the dry gas supply step is performed again when it is determined that light water vapor is not supplied into the device in the water vapor supply determination step. .   The device decontamination method according to any one of claims 1 to 3, wherein in the dry gas supply step, the device is further heated.   The dew point of the gas containing the water vapor of light water supplied to the inside of the device in the water vapor supply step is set to -5 to -15 ° C. The device according to any one of claims 1 to 4, Decontamination method. The water vapor supply step is a supply step of supplying a gas containing a predetermined amount of light water vapor inside the device;
A tritium concentration acquisition step of acquiring information on the tritium concentration in the gas inside the device supplied in the supply step;
When the concentration of tritium in the gas becomes higher than a predetermined value, a condensing step for condensing water vapor in the gas and recovering it as a liquid;
The device decontamination method according to any one of claims 1 to 5, wherein the device is decontaminated. In decontamination equipment for equipment that handles heavy water containing tritium internally,
A dry gas supply means for supplying a dry gas to the inside of the device to evaporate heavy water containing tritium, and simultaneously discharging the gas containing evaporated heavy water from the device;
Evacuation means for evacuating the inside of the device;
Pressure acquisition means for acquiring the pressure inside the evacuated device;
Water vapor supply means for supplying gas containing light water vapor to the inside of the device;
An apparatus for decontamination of equipment.   The dry gas supply means includes a cylindrical body that is filled with an adsorbent and is rotated about its axis, and is fixed among the adsorbent that rotates by the rotation of the cylindrical body. A gas containing the heavy water vapor discharged from the device is supplied to the adsorbent passing through the region to adsorb the water vapor to obtain the dry gas, and the first region and the rotation of the adsorbent The apparatus for decontamination of equipment according to claim 7, wherein the adsorbent is regenerated by supplying a regeneration gas to the adsorbent passing through a second region that is spaced apart and fixed in the direction. .   The device decontamination apparatus according to claim 8, comprising: a sealed container that houses the cylindrical body in a sealed state; and secondary recovery means that recovers water vapor in the sealed container. .

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