RU2105366C1 - Water cleaning system for solid radioactive waste cooling ponds - Google Patents

Abstract

FIELD: nuclear power engineering. SUBSTANCE: system has water filtering and demineralizing units, as well as sorption-type water decontaminating unit immersed in cooling pond. Sorption-type cleaning unit is placed between filtering unit and demineralizing unit and has one or more stationary cells with replaceable capsules containing sorbent. Inorganic or composite radionuclide sorbents are used as a rule. System is provided, in addition, with transportation utilities used to convey spent sorbent-containing capsules from pond. EFFECT: improved service life of demineralizing unit, eliminated problem of biological safety of ion-exchange columns, provision for removal of radioactive wastes in solid state. 3 cl, 1 dwg

Description

 The invention relates to nuclear technology and can be used to purify radioactively contaminated water from pools of solid radioactive waste (SRW), in particular, storage tanks for spent fuel from nuclear reactors.

 A known system of water purification of a pool, including a site for sorption water purification from radionuclides, mixed in pool water, and transport communications, which allowed after lowering the unit to lower the device to the bottom of the pool for storage / Application of Japan N 56-12835, 1976. cl. G 21 F 9/06, G 21 F 9/30. Published March 24, 81, N 6-321 /. This system does not require bioprotection, however, it does not allow for comprehensive water treatment - from suspensions, radionuclides and chemical impurities. In addition, the disadvantage of the system is the difficulty of disposing of the device, since as the spent devices accumulate in the pool, it will be necessary to evacuate them. At the same time, the devices are rather cumbersome, since they are non-separable and are dismantled as a whole together with communication lines, so their transportation is difficult.

 A known system for the purification of radioactive contaminated water from cesium radionuclides, including a filtration unit and a site for sorption water purification from cesium on a selective inorganic sorbent / Promotional message company IVO international LTD. - IVO - Cs Treat an effective method for removal of cesium from evaporator concentrates /. The system allows you to effectively purify water from the main radioactive component, but does not provide chemical treatment (desalination) of water. In addition, the system requires serious bioprotection of the sorption columns; difficulties arise with the evacuation of the spent sorbent.

 The closest in technical essence is the pool water purification system, selected as a prototype / Environmental protection at the enterprises of the nuclear industry /. F.Z. Shiryaev, V.I. Karpov, V.M. Krupchatnikov, etc. - M.: Energoizdat> 1982. - p. 145 /. It includes a filtration unit (water purification from mechanical impurities) and a water desalination unit on ion-exchange columns and is used in pools of nuclear power plants and radiochemical plants. All these pools, in addition, are equipped with transport communications for the unloading of solid radioactive waste, however, due to their functional purpose, they have no direct relation to the cleaning system. The water purification system allows for deep water purification from salts and radionuclides, however, it has the following disadvantages: the low capacity of ion-exchange resins for radionuclides of alkaline elements (cesium-137.134), often determining the background radiation of the pool, there is a problem of biosecurity of ion-exchange columns. All this determines the overall low life of the columns before regeneration. In addition, the regeneration generates large volumes of liquid radioactive waste, requiring the organization of their storage and solidification.

 The objective of the invention is to increase the service life of the desalination unit with the removal of the biosecurity problem, the inclusion of radionuclides in a solid matrix and the simplification of the burial operation.

 The task is achieved by the fact that between the filtration unit and the water desalination unit there is a site of sorption water purification from radionuclides determining the radiation background on selective inorganic or composite sorbents, mixed in the pool water and consisting of one or several stationary cells and replaceable cylindrical capsules installed in them with sorbent, moreover, the capsule dimensions correspond to the dimensions of the transport communications containers for the removal of SRW from the pool.

 Comparative analysis with the prototype allows us to conclude that the inventive purification system is additionally equipped with a site for sorption water purification from radionuclides located in the pool water, moreover, transport communications for the removal of SRW are included in the system. Thus, the claimed solution meets the criteria of the invention of "novelty."

 A distinctive feature of the invention lies in the fact that the site of sorption water purification consists of two main parts - one or more stationary cells permanently in the pool, and replaceable capsules with a sorbent installed in the cells, the capsules being loaded with an inorganic or composite sorbent selective for radionuclides determining the radiation background of the pool. Comparison of the proposed solutions with other technical solutions in the art did not reveal in the latter a similar set of distinctive features, which allows us to conclude that the proposed solutions meet the criterion of "inventive step".

 The drawing 1 shows the basic layout of the inventive water treatment system. The system includes a unit for filtering water from mechanical impurities 1, a unit for desalination of water on ion-exchange columns 2, a site for sorption water purification from radionuclides 3, transport communications for removal of solid radioactive waste for disposal 4. A site for sorption treatment 3 is located in the water of pool 5 and consists of one or more stationary cells 6 and replaceable cylindrical capsules 7. The stationary cell 6 consists of a housing 8, a clamping mechanism 9, a sealing plug 10, a lead 11 and a lead 12 lines. The sorption unit 3 is attached to the slit overlap 13 or to the pool wall. Capsules 7 are loaded with inorganic or composite sorbents 14, selective for radionuclides determining the background radiation.

 The inventive system operates as follows. Water from the pool 5 is taken for cleaning and enters the filter 1 to remove mechanical impurities. Purified water from the suspensions via the intake line 11 enters the site of sorption water purification from radionuclides 3 in the upper part of the housing 8 of the stationary cell 6, passes through a layer of selective sorbent 14 in the capsule 7, enters the lower part of the housing 8 of the stationary cell and leaves line 12. The clamping mechanism 9 prevents water from entering the upper part of the housing 8 into the lower part, bypassing the capsule 7, and the sealing plug does not allow water to exit the housing 8 without having been cleaned on the sorbent 14. Next, the water enters the desalination unit 2, oh, in case of shutting it down for prevention (regeneration), it returns to the pool.

 After the capacity of the sorbent 14 is exhausted, cell 6 is opened, the capsule 7 is removed from cell 6 and sent via transport communications 4 to the SRW repository for burial. The dimensions of the capsule 7 correspond to the dimensions of the containers of the existing transport communications 4 for the removal of SRW.

 During the operation of the spent fuel pool assembly (OGVS) holding pools at nuclear power plants or radiochemical plants, the radiation background of water is often determined by the radionuclides of cesium-137 and cesium-134. In this case, composite sorbents of the Selex - CFN or FTsU brands based on transition metal ferrocyanides selective for cesium can be used as sorbents 14.

 When operating pools of exposure to spent ionizing radiation sources based on cobalt-60, inorganic sorbents of the GNG (GGN) type or composite sorbents of the GGNU type based on hydrated nickel oxides can be used.

 In case of water contamination with strontium-90, composite or inorganic sorbents such as ISM, Selex-DMT based on manganese dioxide can be used as capsule 7 loading.

 To remove the capsules 7 for disposal at radiochemical plants, transport communication containers can be used to remove the SFA shanks.

 Thus, the radionuclides determining the background radiation do not reach the desalination unit, and the resource of the latter increases, since it is determined by the exchange capacity of the ion-exchange columns, and not the background radiation at the desalination unit or the filtrate activity. The experiments showed that the use of the proposed solution in the SFA storage pool will lead to an increase in the resource of ion-exchange columns by 2.5 times with an increase in the coefficient of purification from radionuclides by 2-4 times, while it is not necessary to solve the problem of biosecurity and improve sanitary standards for the operation of the desalination unit. Spent capsules with a sorbent are easily removed for burial, because they have the simplest cylindrical shape, are compact, and allow the extension of remote work.

Claims (3)

 1. The water purification system of the pools for holding solid radioactive waste, including nodes for filtering and desalting water, characterized in that the system is additionally equipped with transport communications for removing solid radioactive waste and a site for sorption water purification from radionuclides located in the pool water, and the site for sorption treatment is between the nodes of filtration and desalination of water and consists of one or more stationary cells with replaceable capsules with a sorbent.  2. The system according to claim 1, characterized in that inorganic or composite sorbents selective for radionuclides determining the radiation background of the pool are used as sorbents.  3. The system according to claim 1 or 2, characterized in that after the sorbent capacity is exhausted, replaceable capsules are removed from the pool assembly in the form of solid waste through transport communications to remove solid radioactive waste from the pool.