JP5350337B2 - Radioactive waste treatment method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radioactive waste treatment method and apparatus therefor capable of reducing a backwash frequency of a filtering device for filtering supernatant water. <P>SOLUTION: Backwash water containing a waste sludge discharged from a purifying device 5 provided in purifier piping 40 is supplied to a sedimentation tub 8 by a sludge supply pipe 7. Backwash water containing a waste sludge discharged from a filtering demineralizer of a used fuel storage pool purifying system is supplied to the sedimentation tub 8 by a sludge supply pipe 24. Backwash water containing minute iron hydroxide generated from a condensation filtering device 3 provided in water supply piping 32 is guided into a sedimentation tub 25 by a sludge supply pipe 6. Supernatant water containing floating iron hydroxide within the sedimentation tub 25 is heated by a heater 34. The iron hydroxide is aggregated by heating by the heater 34 and becomes an aggregate having a large grain size. Supernatant water containing the aggregate is supplied to a filtering device 27 and collected as a filtered liquid. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a radioactive waste treatment method and apparatus therefor, and more particularly, backwash water generated in a condensate filtration device provided in a water supply pipe of a boiling water nuclear power plant and a purification system pipe for a reactor coolant purification system. The present invention relates to a radioactive waste treatment method suitable for treating a slurry of used ion exchange resin generated from a filtration and desalination apparatus provided in the apparatus and an apparatus therefor.

  In boiling water nuclear power plants, the condensate filtration device provided in the feed water pipe removes the clad that is an iron rust component contained in the feed water, thereby reducing the amount of clad brought into the reactor by the feed water. In addition, the filtration desalination apparatus provided in the purification system piping of the reactor coolant purification system communicated with the nuclear reactor removes radionuclides and cladding contained in the reactor water, which is the cooling water in the reactor, Purifying water. The filtration and desalination apparatus provided in the spent fuel storage pool purification system removes ions and cladding contained in the cooling water in the spent fuel storage pool that stores the spent fuel assembly.

  When the purification performance of these boiling water nuclear power plants is reduced, the performance is improved as follows. In the condensate filtration device (for example, hollow core membrane filter) provided in the water supply pipe, the clad adhering to the filter is removed by backwashing using backwashing water. In each of the filtration desalination equipment installed in the reactor coolant purification system and the spent fuel storage pool purification system, used powder ion exchange resin whose performance has been reduced and has reached the end of its life is removed from the filter member, and a new powder An ion exchange resin is precoated on the filter member.

  Used powder ions discharged from the backwash water generated by the regeneration operation of the condensate filter installed in the water supply piping, the filter demineralizer installed in the reactor coolant purification system and the spent fuel storage pool purification system Exchange resin (waste sludge) and low-conductivity waste liquid (LCW) generated from other nuclear reactor systems and turbine systems are radioactive waste and are processed by a radioactive waste treatment apparatus.

  An example of this radioactive waste treatment apparatus is described in JP-A-11-153696. This radioactive waste treatment apparatus has an LCW treatment system and a backwash water and waste sludge treatment system.

  After the LCW generated from the reactor system and the turbine system is collected in the collection tank, the solid content is removed by the LCW filtration device (hollow core membrane filter), and the ions are removed by the LCW desalination device. The waste liquid discharged from the LCW desalinator is sampled in the LCW sample tank, transferred to a condensate storage tank, and reused as plant water for a boiling water nuclear plant.

  Sludge of waste sludge discharged from the backwash water generated in the condensate filtration device of the water supply pipe, the filtration desalination device of the reactor coolant purification system and the spent fuel storage pool purification system is transferred to the sedimentation separation tank. The The solid content (cladding and waste sludge) contained in the waste liquid is settled and separated in the sedimentation tank, and the supernatant water in the sedimentation tank is supplied to the filtration device. This filtration device separates the floating cladding contained in the supernatant water. The supernatant water from which the clad has been removed is supplied to a collection tank for collecting LCW, and is processed in the above-described LCW processing system. Backwash water including the clad generated by backwashing in the filtration device is transferred to the settling separation tank.

  The clad and waste sludge separated and settled in the above sedimentation tank are sufficiently mixed with supernatant water in the sedimentation tank after the radioactivity is sufficiently attenuated, and are solidified in a slurry state of about 10 w%. It is transferred to.

  The radioactive waste treatment apparatus described in Japanese Patent Application Laid-Open No. 11-153696 includes backwash water generated in a condensate filtration apparatus for water supply piping, and each filtration of a reactor coolant purification system and a spent fuel storage pool purification system. Slurry of waste sludge discharged from the desalinator is collected in one settling tank. The backwash water generated in the condensate filter of the water supply pipe has a very low radioactivity level. On the other hand, the waste sludge discharged from the filtration desalination devices of the reactor coolant purification system and the spent fuel storage pool purification system is the fuel that stores the reactor water and spent fuel assemblies in the reactor. The level of radioactivity increases due to the purification of the cooling water in the storage pool. Collecting the above-described backwash water and waste sludge in one settling tank increases the amount of radioactive waste with a high radioactivity level.

  The radioactive waste treatment apparatus described in JP-A-63-94197 stores waste sludge discharged from a filtration demineralizer provided in a water supply pipe and used ion exchange resin discharged from a demineralizer. The waste sludge with high radioactivity level collected in the tank and discharged from the filtration desalination equipment of the reactor coolant purification system and the spent fuel storage pool purification system is collected in the sedimentation separation tank. For this reason, waste sludge and spent ion exchange resin with low radioactivity levels discharged from the filtration and desalination equipment and desalter provided in the water supply pipe are converted into a reactor coolant purification system and a spent fuel storage pool purification system. Avoid mixing with waste sludge of high radioactivity level discharged from each filtration desalination unit.

  Japanese Laid-Open Patent Publication No. 62-95500 proposes that the backwash water of a non-auxiliary filter is heated to 60 to 100 ° C. and separated by settling.

Japanese Patent Laid-Open No. 11-153696 JP-A-63-94197 JP-A-62-95500

The clad removed by the condensate filtration device provided in the water supply pipe is a condenser that condenses the steam exhausted from the turbine, and the steel material constituting the water supply pipe connected to this condenser is in contact with the condensate. The main component is an iron rust component generated by corrosion, and the chemical form is an iron oxide such as Fe ₃ O ₄ and Fe ₂ O ₃ and an iron hydroxide of FeOOH. Condensate produced by condensation of steam in a condenser of a boiling water nuclear power plant has few impurities, and its water quality is close to that of pure water. Therefore, the supernatant water in the sedimentation separation tank has a water quality close to that of pure water, its conductivity is as low as 1 μS / cm, and the pH value is around 6. Under such conditions, FeOOH, which is an iron hydroxide, may disperse in a colloidal state in the liquid, and precipitation due to gravity may be difficult to occur. In that case, the iron concentration in the supernatant water in the sedimentation tank does not decrease over time, and a considerable amount of clad may be mixed in the supernatant water in the sedimentation tank.

  In the radioactive waste disposal apparatus disclosed in Japanese Patent Application Laid-Open No. 11-153696, the supernatant water in the sedimentation tank is guided to the filtration device, and the clad contained in the supernatant water is removed by the filtration device. Since the supernatant water from which the clad has been removed by the filtration device is supplied to the LCW treatment system, clogging of the LCW filtration device provided in the LCW treatment system can be suppressed, and the backwash frequency of the LCW filtration device can be reduced. However, although clogging of the LCW filtration device can be suppressed, conversely, the filtration device to which the supernatant water in the sedimentation separation tank is supplied is likely to be clogged by a fine clad (FeOOH) on the order of several hundred ppm, and backwashing is performed. Increases frequency.

  In Japanese Patent Application Laid-Open No. 62-95500, backwash water from a condensate filtration device is heated to 60 to 100 ° C. in order to promote sedimentation and separation of the clad. Sedimentation can be accelerated by changing the agglomeration state of the clad by heating without adding a chemical solution. Changes in the agglomeration state of the clad due to heating are affected by the initial particle size and concentration of the clad, or coexisting components, so it may be difficult to perform a stable separation process only by heating and sedimentation.

  An object of the present invention is to provide a radioactive waste treatment method and apparatus capable of reducing the frequency of backwashing of a filtration apparatus for filtering supernatant water.

  A feature of the present invention that achieves the above-described object is that a radioactive waste liquid containing waste sludge discharged from a first purification device that purifies cooling water in a nuclear power plant nuclear reactor is supplied to the first sedimentation separation tank, The backwash water containing the floating cladding discharged from the second purification device for purifying the feed water provided in the water supply pipe is supplied to the second sedimentation separation tank, and the floating cladding in the second sedimentation tank is removed. The supernatant water containing is heated and supplied to the filtration device, a part of the supernatant water supplied in this filtration device is recovered, and the remaining supernatant water containing the floating clad aggregate produced by heating is filtered. To return to the second sedimentation tank.

  Since the supernatant water containing the floating cladding in the second sedimentation separation tank is heated, the floating cladding aggregates into aggregates having a large particle size, and the supernatant water containing these aggregates is supplied into the filtration device. Is done. Even if agglomerates accumulate in the filtration device, a large gap is formed between the accumulated agglomerates, so that an increase in the differential pressure of the filtration device can be suppressed, and the backwash frequency of the filtration device Can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the backwash frequency of the filtration apparatus which filters supernatant water can be reduced.

It is a block diagram of the radioactive waste processing apparatus used for the radioactive waste processing method which is one preferable Example of this invention.

  Inventors examined the method of reducing the backwash frequency of the filtration apparatus which filters the supernatant water of a sedimentation-separation tank described in Unexamined-Japanese-Patent No. 11-153696. The inventors examined heating of the supernatant water containing fine iron hydroxide (FeOOH) described in JP-A-62-95500. In JP-A-62-95500, by heating the supernatant water, iron hydroxide contained in the supernatant water is changed to iron oxide to improve the sedimentation property. The inventors have found that when water containing fine iron hydroxide is heated, the particle size of the fine iron hydroxide is greatly changed by heating. Iron hydroxide, which is a kind of clad contained in the backwash water of the condensate filtration device, is usually fine particles of 1 μm or less, but the water containing this iron hydroxide is heated to, for example, 80 ° C. The iron hydroxide aggregated to increase the particle size, and the particle size became several tens of μm. If only the change in the chemical form of the clad as described in JP-A-62-95500 is not affected, the frequency of backwashing of the filtration device is not significantly affected, but the particle size of iron hydroxide increases due to aggregation. As a result, the time required for the differential pressure of the filtration membrane of the filtration device to increase to the set differential pressure is increased. This is because, when not heated, the particle size of iron hydroxide is small and there are almost no gaps between the iron hydroxide particles deposited on the filtration device. This is because the gap between the aggregates of the iron hydroxide accumulated in the filtration device becomes large and the increase in the differential pressure of the filtration device is suppressed. Based on such new knowledge, the inventors have come up with the idea of heating the supernatant water of the sedimentation tank and supplying it to the filtration device.

  An embodiment of the present invention reflecting such an idea will be described below.

  A radioactive waste processing method according to a preferred embodiment of the present invention will be described with reference to FIG.

  First, an outline of a boiling water nuclear power plant to which the radioactive waste treatment method of this embodiment is applied will be described with reference to FIG. The nuclear reactor 1 is connected to the turbine 2 by the main steam pipe 31, and the condenser 30 is connected to the turbine 2. The condenser 30 is connected to the nuclear reactor 1 by a water supply pipe 32. From the condenser 30 to the reactor 1, a plurality of condensate filtration devices 3, a plurality of condensate demineralizers 4, a low-pressure feed water heater (not shown), a feed pump ( A high-pressure feed water heater (not shown) and a high-pressure feed water heater are provided in this order. The condensate filtration device 3 has, for example, a hollow filter, and the condensate demineralizer 4 is filled with an ion exchange resin. The boiling water nuclear power plant has a recirculation system and a reactor purification system. The recirculation system has a recirculation system pipe 33 provided with a recirculation pump 39. This recirculation piping 33 is connected to the nuclear reactor 1. The nuclear reactor purification system includes a purification system pipe 40, a purification system pump 41, and a purification device 5. The purification device 5 is a filtration desalination device in which a filter member is pre-coated with a powder ion exchange resin. One end of the purification system pipe 40 is connected to the recirculation system pipe 33 upstream of the recirculation pump 39, and the other end of the purification system pipe 40 is connected to the water supply pipe 32.

  Cooling water supplied to the core (not shown) in the nuclear reactor 1 by driving the recirculation pump 39 is heated by heat generated by nuclear fission of nuclear fuel material contained in the fuel assembly loaded in the core. Part becomes steam. This steam is discharged from the nuclear reactor 1 to the main steam pipe 31, supplied to the turbine 2 through the main steam pipe 31, and rotates the turbine 2 connected to a generator (not shown). The generator is also rotated to generate electricity. The steam exhausted from the turbine 2 is condensed by the condenser 30 to become water. This water is supplied to the nuclear reactor 1 through the water supply pipe 32 as water supply. Cladding such as iron hydroxide (FeOOH) contained in the feed water flowing through the feed water pipe 32 is removed by the condensate filtration device 3. Furthermore, ionic impurities contained in the water supply are removed by the condensate demineralizer 4. Thereafter, the feed water is heated by the low-pressure feed water heater and the high-pressure feed water heater, the temperature is raised, the pressure is raised by the feed water pump, and is led to the reactor 1 by the feed water pipe 32.

  A part of the cooling water flowing in the recirculation system pipe 33 flows into the purification system pipe 40 by the drive of the purification system pump 41 and is supplied to the purification device 5. The purification device 5 removes the clad and ions contained in the cooling water. The cooling water purified by the purification device 5 is supplied to the nuclear reactor 1 through the purification system pipe 40 and the water supply pipe 32.

  A radioactive waste treatment apparatus applied to such a boiling water nuclear power plant and used in the radioactive waste treatment method of this embodiment will be described with reference to FIG.

  The radioactive waste treatment apparatus used in the radioactive waste treatment method of this embodiment includes sedimentation separation tanks 8 and 25, supernatant water pumps 10 and 26, a filtration device 27, and a heater 34. The filtration device 27 includes a large number of tubular reverse osmosis membranes (RO membranes) and applies a cross-flow filtration method. A supernatant water discharge pipe 9 provided with a supernatant water pump 10 is connected to the upper part of the sedimentation separation tank 8. A pipe 21 is connected to the supernatant water discharge pipe 9 downstream of the supernatant water pump 10. The pipe 21 is also connected to a high conductivity waste liquid (HCW) treatment system (not shown). A sludge discharge pipe 22 provided with a pump 23 connected to a solid processing system (not shown) is connected to the bottom of the sedimentation separation tank 8. A supernatant water discharge pipe 38 provided with the supernatant water pump 26 is connected to the upper part of the sedimentation separation tank 25 and further connected to the filtration device 27. A return pipe 28 connects the upper portion of the filtration device 27 and the sedimentation tank 25. The supernatant water discharge pipe 38 and the return pipe 28 form a circulation pipe for the supernatant water. A heater 34 is provided in the supernatant water discharge pipe 38 between the supernatant water pump 26 and the filtration device 27. A sedimentation tank 25 is connected to the condensate filtration device 3 by a backwash water discharge pipe 6.

  A sedimentation tank 8 is connected to the purification device 5 by a sludge supply pipe 7. The sedimentation tank 8 is connected to a sludge supply pipe 24 connected to a filtration desalination apparatus (not shown) provided in a spent fuel storage pool purification system (not shown). The spent fuel storage pool purification system filtration desalination device purifies the cooling water in the spent fuel storage pool for storing spent fuel assemblies. This filtration desalination apparatus also pre-coats the powder ion exchange resin to the filter member.

  The LCW processing system includes a collection tank 12, an LCW filtration apparatus (including a hollow core membrane filter, for example) 14, an LCW desalting apparatus 15, and an LCW sample tank 16. The LCW filtration device 14 is connected to a collection tank 12 and an LCW desalting device 15 filled with an ion exchange resin. The LCW sample tank 16 is connected to the LCW desalting apparatus 15. Specifically, the LCW pipe 36 connects the collection tank 12, the LCW filtration apparatus 14, the LCW desalting apparatus 15, and the LCW sample tank 16 in this order from upstream to downstream. The differential pressure gauge 35 measures the differential pressure upstream and downstream of the LCW filtration device 14. A supernatant water discharge pipe 9 is connected to the collection tank 12. A sludge supply pipe 20 connected to the LCW filtration device 14 is connected to the sedimentation separation tank 8. A filtrate supply pipe 29 is connected to the LCW sample tank 16.

  A pipe 42 provided with the pump 17 connects the LCW sample tank 16 and the condensate storage tank 18. A condensate supply pipe 37 provided with a condensate transfer pump 19 is connected to a piping system of a boiling water nuclear power plant, for example, a feed water pipe 32 and a cooling water supply pipe (not shown) of an emergency core cooling system. Is done.

  When the purification device 5 purifies the cooling water in the nuclear reactor 1 and the differential pressure between the upstream and downstream of the purification device 5 increases to a set differential pressure, the filter member in the purification device 5 is precoated. The powder ion exchange resin is removed from the filter member by backwashing water and discharged as sludge to the sludge supply pipe 7 together with backwashing water. The backwash water containing the waste sludge is supplied to the settling separation tank 8 through the sludge supply pipe 7. When one purification device 5 is backwashed, the other purification device 5 in the standby state purifies the cooling water flowing in the purification system pipe 40. In the purification device 5 from which the powder ion exchange resin is removed by the backwash water, a new powder ion exchange resin is precoated on the filter member.

  Even in the filtration and desalination apparatus of the spent fuel storage pool purification system, when the differential pressure rose to the set differential pressure, the powder ion exchange resin was removed from the filter member by the backwash water and removed, as in the purification apparatus 5. Backwash water containing powder ion exchange resin (waste sludge) is supplied to the sedimentation separation tank 8 through the sludge supply pipe 24.

  In the sedimentation / separation tank 8, the clad supplied to the sedimentation / separation tank 8 together with waste sludge and backwash water such as the purification device 5 is sedimented and separated. The clad removed by the purification device 5 and the filtration and desalination device of the spent fuel storage pool purification system contains almost no iron hydroxide. The supernatant water present in the upper part of the sedimentation tank 8 from which the waste sludge and the clad have been separated by sedimentation is discharged to the supernatant water discharge pipe 9 and pressurized by the supernatant water pump 10, and the collection tank 12 by the supernatant water discharge pipe 9 or It is supplied to the HCW processing system through the pipe 21. The supply of the supernatant water to the collection tank 12 or the HCW treatment system is provided in the first on-off valve and the pipe 21 provided in the supernatant water discharge pipe 9 downstream of the connection point between the supernatant water discharge pipe 9 and the pipe 21. This is done by switching the second on-off valve. For example, the conductivity of the supernatant water measured by a conductivity meter (not shown) provided in the supernatant water discharge pipe 9 upstream of the supernatant water pump 10 is not more than the set conductivity that can be supplied to the LCW treatment system. At this time, the first on-off valve is opened and the second on-off valve is closed, and the supernatant water in the sedimentation separation tank 8 pressurized by the supernatant water pump 10 is supplied to the collection tank 12 of the LCW treatment system. When the conductivity of the supernatant water measured by the conductivity meter exceeds the first set conductivity, the second on-off valve is opened and the first on-off valve is closed, and the supernatant water boosted by the supernatant water pump 10 is used. Is supplied to the HCW processing system via the pipe 21.

  The radioactive solid waste such as waste sludge and clad separated and settled in the sedimentation tank 8 is discharged to the sludge discharge pipe 22 by driving the pump 23 and transferred to the solidification processing system after the radioactivity is sufficiently attenuated. And solidified in the drum.

  The collection tank 12 is supplied with low-conductivity waste liquid generated from the nuclear reactor system and the turbine system. The low-conductivity waste liquid in the collection tank 12 containing the supernatant water supplied from the sedimentation / separation tank 8 is pressurized by the pump 13 and supplied to the LCW filter 14, and the solid content contained in the low-conductivity waste liquid is supplied to the LCW filter. 14 is removed. The LCW desalinator 15 removes ions contained in the low-conductivity waste liquid discharged from the LCW filter 14. The low-conductivity waste liquid purified by the LCW filtration device 14 and the LCW desalting device 15 does not contain solid content and ionic components, and is supplied to the LCW sample tank 16 as reused water. The reused water in the LCW sample tank 16 is sampled and measured for electrical conductivity. When the measured electrical conductivity is equal to or lower than the second electrical conductivity setting value that can be reused, the reused water in the boiling water nuclear power plant is recycled. It can be used and transferred to the condensate storage tank 18 by the pump 17 and the pipe 42. The reused water in the condensate storage tank 18 is reused as plant water for a boiling water nuclear plant.

  When the differential pressure upstream and downstream of a certain condensate filtration device 3 rises to a set differential pressure, the condensate filtration device 3 is backwashed, and the solid content ( (Including iron hydroxide) is removed. Backwash water discharged from the condensate filtration device 3 and containing solid content (including iron hydroxide) is supplied to the settling separation tank 25 through the backwash water discharge pipe 6. In the sedimentation separation tank 25, the supplied solid content other than iron hydroxide which is a floating clad (for example, a clad of iron oxide) is settled and separated. The supernatant water containing floating iron hydroxide in the settling tank 25 is discharged into the supernatant water discharge pipe 38 by driving the supernatant water pump 26. The supernatant water is heated to, for example, 80 ° C. by the heater 34 in the supernatant water discharge pipe 38. By heating the supernatant water, the iron hydroxide contained in the supernatant water aggregates to increase the particle size. Supernatant water containing iron hydroxide aggregates having a large particle size is supplied to the filtration device 27. A part of the supernatant water supplied to the filtration device 27 passes through the tubular RO membrane in the filtration device 27 as a filtrate and is discharged to the filtrate supply pipe 29, passes through the filtrate supply pipe 29, and is an LCW sample tank. 16 is reused as plant water.

Since the temperature of the feed water supplied from the condenser 30 to the condensate filtration device 3 through the feed water pipe 32 is low, it is finer and less likely to settle than Fe ₃ O ₄ and Fe ₂ O ₃ (for example, It seems that a large amount of (γ-FeOOH) is produced. As a result, the proportion of iron hydroxide in the clad captured by the condensate filtration device 3 increases, and the proportion of iron hydroxide contained in the backwash water supplied to the settling separation tank 25 also increases.

  A part of a large number of aggregates produced by agglomeration of iron hydroxide contained in the supernatant water is deposited on the surface of the RO membrane in the filtration device 27, and the remaining aggregates contained in the supernatant water are accumulated. Together with the supernatant water, it passes through the tubular RO membrane in the filtration device 27, passes through the return pipe 28, and is supplied into the sedimentation separation tank 25. Each aggregate having a large particle size that has flowed into the sedimentation tank 25 is settled and separated in the sedimentation tank 25.

  The filtration device 27 separates the iron hydroxide aggregate and the supernatant water by a cross-flow filtration method using an RO membrane. In the cross-flow filtration method, the filtration cake deposited on the filtration surface is removed by shearing force due to the flow of the treatment liquid parallel to the surface of the filtration membrane (for example, RO membrane), and the formation of the filtration cake on the filtration membrane surface is minimized. Kept. For this reason, in principle, the cross-flow filtration method can perform highly efficient filtration over a long period of time, even when waste liquids with a high solid content such as cladding are treated, with relatively little clogging of the filtration membrane. It becomes possible.

  However, when processing the waste liquid containing the high concentration clad which is a processing target in this embodiment by the filtration device 27 using the RO membrane, the inventors are concerned about the stable treatment performance of the filtration device 27. embraced. Therefore, the inventors conducted an experiment in which a simulated waste liquid containing a high-concentration clad was treated using a filtration device having an RO membrane. As a result, it was confirmed that the RO membrane was not clogged and could be stably filtered even if the clad concentration exceeded 2000 ppm by the filtration device having the RO membrane. This experiment proved the feasibility of treating waste liquid containing high-concentration clad by a cross-flow filtration method using a filtration membrane.

  After the supernatant water containing the iron hydroxide aggregate is treated for a predetermined period in the filtration device 27, the RO membrane in the filtration device 27 is backwashed, and the aggregate deposited on the inner surface of the RO membrane returns together with the backwash water. It returns to the sedimentation tank 25 through the tube 28. This aggregate is also settled and separated in the sedimentation tank 25. Although not shown in FIG. 1, a sludge discharge pipe 22 is also connected to the bottom of the sedimentation separation tank 25. Solids such as aggregates settled in the settling tank 25 are also sufficiently attenuated in radioactivity, and then discharged to the sludge discharge pipe 22 by driving the pump 23 and transferred to the solidification processing system to be solidified in the drum can. Is done.

  Each solid content settled in the sedimentation separation tanks 8 and 25 may be incinerated instead of being solidified.

  In the present embodiment, since the supernatant water containing the floating clad (fine iron hydroxide) in the sedimentation separation tank 25 is heated by the heater 34, a large number of iron hydroxides having agglomerated and having a large particle size are obtained. Aggregates can be supplied to the filtration device 27. A part of these aggregates is deposited on the inner surface of the RO membrane, which is a filtration membrane in the filtration device 27. However, since the aggregate has a large particle size, a large gap is formed between the aggregates. Supernatant water tends to permeate the RO membrane through these gaps. The formation of a large gap between the aggregates deposited on the inner surface of the RO membrane can suppress an increase in the differential pressure inside and outside the RO membrane. For this reason, the frequency of backwashing the RO membrane in the filtration device 27 can be reduced, and the throughput of the filtration device 27 can be improved.

  Each aggregate that has passed through the RO membrane in the filtration device 27 is introduced into the sedimentation tank 25 and separated by sedimentation. Since the aggregate having an increased particle size is supplied to the RO membrane in the filtration device 27, clogging of the RO membrane is suppressed, the treatment efficiency of the supernatant water by the RO membrane is improved, and the filtrate that permeates the RO membrane. The amount of increases.

  The present embodiment supplies waste sludge and clad discharged from the purification device 5 and the filtration and desalination device of the spent fuel storage pool purification system to the sedimentation separation tank 8 with a high radioactivity level, and the radioactivity level is low. Since the backwash water discharged from the condensate filtration device 3 is supplied to the settling separation tank 25 different from the settling separation tank 8, it is discharged from the purification device 5 and the filtration and desalination device of the spent fuel storage pool purification system. Waste sludge and clad and backwash water discharged from the condensate filtration device 3 are not mixed, and the amount of radioactive waste having a high radioactivity level can be reduced. The radiation shielding of the backwash water discharge pipe 6, the sedimentation separation tank 25, the filtration device 27, the supernatant water discharge pipe 38 and the return pipe 28 is simpler than the radiation shielding of the sludge supply pipes 7 and 24 and the sedimentation separation tank 8. Can be made.

  In this embodiment, waste sludge and clad discharged from the purification device 5 and the filtration and desalination device of the spent fuel storage pool purification system are supplied to the sedimentation separation tank 8 and not supplied to the sedimentation separation tank 25. For this reason, since the supernatant water containing floating iron hydroxide in the sedimentation separation tank 25 is heated by the heater 34, the amount of water heated by the heater 34 is reduced, and the capacity of the heater 34 can be reduced.

  According to this embodiment in which the heating of the supernatant water and the filtration device 27 are combined, the separability change due to the dispersion of the initial state of the floating clad as compared with the sedimentation separation described in JP-A-62-95500. Is relaxed, and a stable process with redundancy becomes possible.

  Further, in this embodiment, the wastewater sludge and the clad discharged from the purification device 5 and the filtration and desalination device of the spent fuel storage pool purification system and the sedimentation tank 8 supplied with the clad and the condensate filtration device 3 were discharged. Since the settling / separation tank 8 to which the backwash water is supplied is separated, the agglomeration state due to the heating of the floating clad contained in the backwash water discharged from the condensate filtration device 3 by the heater 34 is purified. There is no influence of other waste liquids including waste sludge and clad discharged from the apparatus 5 and the filtration desalination apparatus of the spent fuel storage pool purification system.

  By heating the supernatant water, fine iron hydroxide is agglomerated to form agglomerates having a large particle size, and thus a coarse filter can be used. For example, a ceramic filter is one of suitable filters because it is excellent in strength and chemical durability. Ultrafiltration membranes and microfiltration membranes can also be used.

  In the present embodiment, the supernatant water in the sedimentation separation tank 25 may be heated by the heater in the sedimentation separation tank 25, in addition to the heater 34 provided in the supernatant water discharge pipe 38.

  DESCRIPTION OF SYMBOLS 1 ... Reactor, 3 ... Condensate filtration device, 5 ... Purification device, 6, 7, 24 ... Sludge supply pipe, 8, 25 ... Sedimentation separation tank, 9, 38 ... Supernatant water discharge pipe, 10, 26 ... Supernatant water Pump, 12 ... LCW collection tank, 13 ... LCW collection pump, 14 ... LCW filtration apparatus, 15 ... LCW desalting apparatus, 16 ... LCW sample tank, 18 ... condensate storage tank, 27 ... filtration apparatus, 28 ... return pipe, 30 ... main condenser, 32 ... water supply piping, 34 ... heater, 40 ... purification system piping.

Claims (5)

  A radioactive waste liquid containing waste sludge discharged from a first purification device for purifying cooling water in a nuclear power plant nuclear reactor is supplied to a first settling separation tank, and the feed water provided in the water supply pipe of the nuclear power plant is purified. A backwashing water containing floating clad discharged from the second purification device is supplied to the second sedimentation separation tank, and the supernatant water containing the floating clad in the second sedimentation separation tank is heated and filtered. A portion of the supernatant water supplied in the filtration device is recovered, and the remaining supernatant water containing the aggregates of the floating clad produced by the heating is supplied from the filtration device to the second A radioactive waste treatment method, wherein the radioactive waste is returned to a settling tank.   The radioactive waste treatment method according to claim 1, wherein the filtration device uses a filtration membrane for treating the supernatant water.   The radioactive waste treatment method according to claim 1, wherein the treatment of the supernatant water in the filtration device is performed by cross flow filtration.   A first sedimentation / separation tank that receives radioactive waste liquid containing waste sludge discharged from a first purification device that purifies cooling water in a nuclear power plant nuclear reactor, and a first water purification device that purifies feed water provided in a water supply pipe of the nuclear power plant. A second settling / separation tank that receives backwash water containing floating clad discharged from the purification apparatus, a heating device that heats the supernatant water containing the floating clad in the second settling / separating tank, and A filtration device to which the supernatant water containing aggregates of the floating clad produced by heating by the heating device is supplied, a first pipe from which the supernatant water collected by the filtration device is discharged, and the filtration A radioactive waste treatment apparatus, comprising: a second pipe for guiding the supernatant water containing the aggregates discharged from the apparatus to the second sedimentation tank.   The radioactive waste treatment apparatus according to claim 4, wherein the filtration apparatus is a filtration apparatus that performs cross-flow filtration.

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