JPS6080795A - Drying treating method of radioactive waste - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention is directed to a method for recycling waste liquid and slurry waste in the treatment of radioactive waste generated from nuclear power plants, etc. The present invention relates to a method for drying radioactive HD leaves.

[Kimei's background]

Radioactive wastes generated from 13X nuclear power plants and the like include various waste liquids, used ion exchange resins, and waste sludge.

Among these, waste liquid includes recycled waste liquid of ion exchange resin, equipment bottom drain, floor drain (waste liquid from cleaning floors, etc.), etc. These waste liquids are concentrated using concentrators, and become so-called concentrated waste liquid. becomes.

These waste liquids, waste sludge, and used ion exchange resins are transferred from the reactor building to the radioactive waste treatment membrane building, where they are stored in tanks and subjected to various volume reduction treatments.

Conventional treatment methods involve concentrating various waste liquids to form concentrated waste liquids, which are then kneaded with cement and solidified in drums.

?゛The in-situ Vζ solidified by the sound compaction waste liquid cement is the condition for ocean dumping (Notification of the Science and Technology Agency) - axial compressive strength 15
In order to satisfy 0 to 9/cld, etc., a 200 t drum can only hold about 10 t of concentrated waste liquid, and in terms of volume,
When cement solidifies, it doubles in volume compared to when it is liquid.

On the other hand, used ion exchange resin and live sludge are mixed with cement and solidified, and a large number of assimilated products are generated (
Because there are few leaves that can be filled with light during cement assimilation, it is currently stored in a storage tank.

However, storage in tanks is only a temporary measure and cannot be said to be permanent, and there are other issues such as ensuring the integrity of the storage tank and securing a space for the storage tank. It's more limited.

On the other hand, IC, %-, and radiation concomitant 4t (Since the final disposal method of the material has not yet been decided, it is necessary to temporarily store the assimilated substance in Zyte.As a basic policy of our country, the Atomic Energy Commission As a final disposal policy, land disposal and ocean disposal are to be used together, but only the standards (Notice of the Science and Technology Agency) have been established for ocean disposal of solidified cement. There is no consensus among neighboring countries regarding dumping, and there is no prospect of implementation.In addition, as for land disposal, an off-site storage method has been proposed as a method that suits our country's busy schedule. As mentioned above, since the implementation date for rutted road disposal has not yet been decided, the amount of solidified waste will continue to increase and a significant reduction in the volume of generated waste will be necessary.1 However, by reducing the volume of raw perishables, the number of assimilated bodies for final disposal will be reduced, which will also reduce final disposal costs.

Recently, as such volume reduction technology, Powderization Seiyo Processing Technique 61:
r is these l'p(H'ji'j volume reduction process + lc
It is effective, and is beginning to be adopted in some cases.

Currently, in general, h'l emissive waste fruit C proboscis place 111! As a dryer, there is a vertical centrifugal type dryer.
This type of machine, which is used for cars, has excellent powdering performance in reducing the moisture content of the powder produced.

However, since the heat transfer surface is cylindrical and has a rotor blade inside, the long direction is narrow 1).

In this way, there was a drawback that when the dryer became ・I, the structure became redder.

However, in the assimilation process after the 10th process of powdering,
When the permissible moisture content range of the produced powder is wide, it is possible to apply a compact dryer other than the vertical centrifugal thin film tamp due to its drying characteristics. In this case, the dryer should be easy to maintain and be a sealed type.

[Purpose of the invention]

The purpose of this study is to provide a compact drying method with high processing capacity for dry P treatment of radioactive waste.

[Summary of the invention]

The special request of this Sf Ming is revised 91 sex j1. [In the process of drying the proboscis, the Ia waste is attached to the surface of the flowing heat 11% ball and is dried by bringing the ball into contact with a heat medium such as M air, using a ceramic ball as the heat medium ball. tt to the point.

[Embodiments of the invention]

Dry pulverization is an extremely effective method for volume reduction treatment to reduce the amount of radioactive waste generated from nuclear power plants and the like.

At present, vertical thin film dryers are in heavy use1, but although they have excellent drying and pulverizing properties for solutions and slurries, they have poor heat transfer properties. Since the dryer has a cylindrical shape, in order to increase the processing capacity, the heat transfer area must be increased, so the dryer becomes larger in size, and if a tHv, a dynamic motor, etc. are installed, the equipment becomes tall.

As a result, the equipment building becomes large-scale and the building construction cost becomes expensive.

However, Leopard I! ■If precise control of the moisture content of the powder is not required after the pulverization process, it is reasonable to install a compact dryer with a large capacity.

However, the dryer cannot have a sealed structure and must be easy to clean and maintain.

In addition, in order to make the dryer compact (11 pieces),
It is safe to increase the evaporation area and improve heat exchange characteristics.

There is a method of drying that satisfies this condition that uses small-diameter balls as the drying medium.

In this method, the waste liquid is attached to the surface of the heat transfer ball in the dryer, and the ball is completely flowed to increase the evaporation area, and the drying hot air is flowed from the bottom to the top in the dryer.
Heat exchange efficiency can be improved by bringing it into countercurrent contact with a moving object.

In addition, the vertical thin film dryer uses centrifugal force to press the rotary blades against the cylindrical heat-transfer body and dry powder the waste while rotating. It is difficult to avoid wear and tear. Using small-diameter balls as the drying medium -C, allow the balls to flow and move (When drying by sequentially contacting hot air from C onwards, the balls will come into contact with each other due to the flow, but external forces such as centrifugal force, etc.) Because it is not for 1L,
＃i粍 will be significantly reduced.

In addition, the structure of the dryer has only a few moving parts, so it is easy to perform closed granulation, and it is possible to use a closed cycle.

In addition, metal balls are normally used as the drying medium balls, but when bent metal balls have good thermal conductivity, the heat capacity of the dryer increases, but it takes a long time to start up. In addition, the thermal efficiency decreases due to the amount of heat consumed by the metal ball, the weight of the dryer increases, and a large compressive force acts on the lower ball, resulting in increased wear on the dryer shell.

These problems can be solved by using a ceramic ball.

First, ceramic has a thermal conductivity 2.6 times that of metal, and can increase the thermal efficiency of a dryer by about 8%.

Table 1 shows the throughput test results conducted using a small test device. The limit value of processing capacity is when the water content of the produced powder is 10 wt%, and the water content is 15 wt%.
This was carried out using an aqueous solution of thorium oxide.

Table 1 Processing Capacity of Ventilated Ball Dryer Ceramic also has excellent abrasion resistance and is light in weight, so it is possible to reduce the wear of the dryer and the output of the driving force for ball flow.

A specific example of a case where waste generated from a nuclear power plant or the like is dried and pulverized will be described in detail below.

When handling radioactive waste, the inside of the system should be sealed.
Moreover, it is suitable to operate as a closed cycle.

Figure 1 shows the 114 structure of the dryer main body.

The dryer has a hot air jacket on the outside and a header on the inside for blowing out hot air.

The hot air is blown into the dryer from the hot air header inside the dryer via the jacket, rises while sequentially coming into contact with the balls inside the dryer, and is discharged from the exhaust port.

In addition, some of the hot air carries dry and powdered waste,
It also comes out from the powder outlet. Furthermore, instead of discharging the dry powder continuously as described above, it is also possible to attach a valve to the powder discharge port and discharge the powder in batches.

The bottom of the dryer has a conical bottom, and at the top,
The grid-shaped bottom plate of the dryer is removable. In other words, the generated powder passes through this grid-like bottom plate of the dryer and reaches the bottom of the dryer.

In addition, there is a screw conveyor (gamma) in the center of the inside of the dryer (l) that allows all the heat medium balls to flow, and this screw conveyor moves the heat medium balls at the bottom of the dryer to the top of the dryer. As a result, the heated balls are heated by the screw container in the center of the dryer, and
Next, the screw conveyor moves to the surrounding area of the dryer, and the amount that is sucked up from the bottom to the top of the dryer by the conveyor settles and causes convection inside the dryer.

On the other hand, the waste enters the dryer via the waste container 1 pipe, gradually settles, is scattered on the heat medium balls, and adheres to the surface of the heat medium balls. The balls with waste adhered to them settle down one by one and come into countercurrent contact with the hot air supplied from the hot air header at the bottom of the dryer, and the adhered I>'
Evaporate the water from the i64tj. In addition, the waste is compressed and crushed in the process in which the heating medium balls come into contact with each other and are crushed, resulting in an effect that the particle size becomes finer. PfI
3. When the particle size of leafy vegetables becomes finer, the evaporation area increases, which is advantageous for drying. Then, the sufficiently dried waste is peeled off due to contact between the balls as the heating medium balls move, and reaches the bottom of the dryer through the entire bottom plate of the dryer.
Discharge σ7L from the powder discharge port. In addition, even if the water is taken out continuously in this way, it is also possible to collect it at the bottom of the dryer and then discharge it.

During periodic inspections, close the powder discharge port and inject cleaning water from the cleaning water injection line to fill the entire heating medium ball with cleaning water, operate as described above, and check how much waste is inside the dryer. After washing, the powder is collected into the washing water receiving tank via the washing water drain and the powder discharge port.

Next, dry powder formation/stem will be explained.

Figure 2 shows an overview of the system.

The dry pulverization system is composed of a dryer, a condenser, a circulation blower 9 heater, and a pressure regulator as main components.

Since this system handles 1G of anti-corrosive material, each of the above-mentioned devices basically has a sealed structure, and during steady operation,
within the system, specifically li/1. The dry powder handling area is set to a weak negative pressure, and the pressure within this system is adjusted by a carving device, and this pressure -I4 adjustment is controlled by sequentially measuring the pressure within the system.

By maintaining the inside of the system at a weak negative pressure, the device
This makes it possible to further prevent radioactive substances from scattering to the outside. Particularly when handling powder, it is necessary to create a weak negative pressure inside the system to prevent the powder from scattering to the outside.

Further, in the case of a completely closed cycle like this, it is reasonable to use an electric heater as the heat source.

Next, an overview of the system functions will be explained.

First, the hot air from the circulation blower is heated to about 150 to 2 (10 C'y!) by an electric heater and enters the dryer.In the dryer, it comes into countercurrent contact with the heat medium balls one after another. The waste adhering to the heating medium balls absorbs moisture and is discharged through the exhaust port J at the top of the dryer.In addition, the fine waste powder that accompanies the hot air is removed from the waste at the top of the dryer. The amount of powder that is captured and entrained outside the dryer when it is fused with the drying heat transfer ball is reduced.

The hot air (heat medium air) discharged from the dryer is guided to the water scooper. Here, the moisture entrained by the hot air is condensed and recovered. The recovered water is concentrated again and reused. Approximately 20 to 35 tons? The heating medium air cooled to
After removing moisture in a demister, it is recycled again via a blower.

On the other hand, waste is supplied from the waste supply tank to a predetermined forging dryer via a supply pump.

Furthermore, the pressure within the system during steady operation is regulated by a pressure regulator. The dry powder is continuously collected from the powder discharge port at the bottom of the dryer by using a cyclone and a blower.

When cleaning the dryer, close the 3-way valve at the powder outlet.
Washing water is injected from the washing water injection line to fill the inside of the dryer with washing water, and then the screw conveyor is activated to flow the heat medium balls and wash them. After the cleaning operation is completed,
Connect the valve to the pipe to the wash water tank and drain the wash water.

After sufficiently draining the washing water, dry the inside of the dryer by operating the dryer without load. The three-way valve is closed, hot air is supplied to the dryer, and the heat medium balls are made to flow in the screw elevator.

If there is a lot of mist and fine powder entrained in the hot air discharged from the dryer, install a mist separator between the dryer and the condenser to separate the water from the dryer and the dryer. It is also possible to remove entrained mist etc. by bringing the discharged hot air into gas-liquid contact, thereby reducing the HV to the condenser side.
It is possible to significantly reduce the amount of transfer of trade between trade. The stem in this case is shown in FIG.

In Figure 3, the hot air coming out of the dryer comes into contact with the condensed water from the condenser in the mist separator, removes the entrained mist, and enters the water tank to remove the moisture. , enter the drying machine via the floater and heating machine.
, has become.

In addition, in Fig. 2, the hot air coming out of the dryer removes moisture using condensate and cotton, and then enters the dryer 4 & via the circulation blower 1 heating machine f. .

〔Effect of the invention〕

The effects of the present invention are listed below.

(1) By using a ceramic ball as the sb/l smell ball, it is possible to improve durability, improve thermal efficiency, and reduce the weight of the equipment to 75-1'.

(2) It has a large processing capacity for dry infiltration, so it can be made smaller, and the entire system can be made more compact.

(3) By using a closed cycle drying system and maintaining a slightly negative pressure inside the system, radioactive materials can be prevented from scattering outside the system.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an embodiment of the dryer main body structure of the present invention. 1...Electric motor, 2...Tist distributor, 3.
...Waste water spray nozzle, 4...Waste supply line, 5..., Screw conveyor, 6...kA I
(L Helter, 7... 3-way valve, 8... Dryer bottom plate, 9
...Heating medium ball. The second part 1 is a system a[:'J,l] showing an example of the flow of the drying treatment system of the present invention. 1...Waste supply tank, 2...Supply bong, 3.
...Dryer, 4...Condenser, 5...Demister-56
...Pressure adjustment device 1st, 7...filter, 8...f
Shield ring) Lower, 9...Additional 1iA4 number (heater),
10... Floater, 11... Cyclone, 12...
・3-way valve. FIG. 3 shows another example of the drying system flow. 1...Waste supply tank, 2...Supply pump, 3.
... Dryer, 4... Condenser, 5... Themister, 6
...Pressure adjustment all, 7...Filter, 8...
Circulation blower 59...additional heater), 10.
... Floater, 11... Cyclone, 12... 3-way 9V % 13... Mist separation 1 time

Claims (1)

[Claims] 1. In the drying process of radioactive waste, waste is attached to the surface of a flowing heat medium ball, and the ball is brought into contact with a heat medium such as hot air to dry the heat medium ball. A method for drying radioactive waste using ceramic balls as fishing equipment. 2. The method for drying radioactive waste according to claim 1, characterized in that the dryer, water heater, heating source, and floor are in a closed cycle. 3. Claim 2, characterized in that it has a pressure regulating device for maintaining a weak negative pressure in the closed cycle of the dryer, condenser, heater, and blower. radioactive 1
Drying treatment method for rust simulators. 4. A mist barrator is installed between the dryer and the pestle to prevent radioactive waste from transferring to the machine after the dryer. The method for drying radioactive waste as described in paragraph 2.