JPH0776798B2 - Radioactive laundry waste liquid treatment device - Google Patents

Description

Detailed Description of the Invention

 Purpose of the invention

[Industrial applications]

The present invention relates to a treatment device for low-level radioactive waste liquid, particularly laundry waste liquid, generated in a nuclear facility.

[Prior art]

Waste liquid containing a surfactant with low specific activity such as laundry waste liquid generated from a nuclear facility such as a nuclear power plant or shower waste liquid used for washing limbs (hereinafter represented by "laundry waste liquid") is Solids are removed by evaporative concentration, reverse osmosis or a rotary strainer, and then treated with an adsorbent such as activated carbon, if necessary, to remove contaminants and then reused or released. The quality of condensed water obtained by the evaporative concentration method is good, and it contains almost no radioactivity. However, since foaming is inevitable when the waste liquid containing the surfactant is heated and evaporated, it is necessary to use a large-capacity evaporator and an antifoaming agent. Evaporative concentrators have high equipment costs, consume a lot of energy, and require operating costs. The reverse osmosis method uses good quality of treated water and does not consume much energy. It is necessary and has the drawback of increasing the equipment cost. Rotary strainer has 100 ~ 2 built in rotary drum
A 00 mesh screen captures solids. This device can be operated and managed so that backwashing is automatically performed when the filtration differential pressure reaches a specified value, and maintenance and inspection are easy. However, this equipment is also relatively expensive, and a tank for receiving backwash water and auxiliary equipment such as a filter for backwash water treatment are required, so a large space must be secured. I have to. In order to remove radioactivity more safely, it is possible to install an activated carbon adsorption tower after this rotary strainer. In recent years, it has been considered to use a packed bed type filter which is inexpensive and requires a small installation space and uses a filter medium. Since the laundry waste liquid contains a considerable amount of solids,
With conventional filter media, the differential pressure rises quickly and must be replaced in a short period of time. For this reason, the cost of materials and work is high, and there is a risk of exposure to workers. In order to enhance the filtering ability of a filter medium, it has been proposed to put an aggregate of chemical fibers in a net bag and divide it into a number of units for use (JP-A-62-222197). This allows the liquid to flow through the gaps between the units, producing an effect close to that of volumetric filtration, but it is necessary to stack the units in different steps to avoid a short path, and filling the filter media requires manpower. It

[Problems to be Solved by the Invention]

It is an object of the present invention to provide a radioactive waste liquid treatment device using a packed bed type filter, which allows a filled filter medium to be used for a long period of time and can be easily replaced. Structure of the invention

[Means for solving problems]

The radioactive liquid waste treatment device of the present invention is a device for treating radioactive liquid waste with a packed bed type filter, and as shown in a representative example of FIG. 1, a filter medium unit 1 in which a large number of spherical fiber lumps are put in a net bag. Are stacked and packed in the filter cylinder 2 in a line in the filtering direction. The spherical fiber mass used in the present invention is preferably one in which a plurality of fibers are entangled with each other to form a spherical body having a diameter of about 10 to 15 mm. As a commercially available product, there is "Marimo" (trade name) manufactured by Unitika Ltd. in which spherical polyester fibers are used. This product is manufactured by the technology of Japanese Examined Patent Publication No. 62-11637. Net bags, like polyester or polypropylene,
If it is made of a material that is combustible and does not generate harmful gas when burned, the used filter medium can be incinerated as it is, which is advantageous for reducing the volume of radioactive waste.

[Work]

FIG. 1 shows an example of an apparatus suitable for treating a large amount of waste liquid. This device 3 comprises a container 31 and a lid 32 for sealing it.
The inside of the container 31 is divided into upper and lower parts by a tube plate partition plate 33. The upper chamber 34 has a conduit 36 for introducing waste liquid, and the upper opening of the filter cylinder 2 is provided in a watertight manner. The filter cylinder 2 extends from the tube plate partition plate 33 to the lower chamber 35,
It has a perforated plate-shaped filter medium supporting bottom 38, and the side wall thereof is made non-perforated. As a matter of course, for the purpose of large-scale processing, it is preferable to provide a plurality of filter cylinders as illustrated. The filtrate discharged through the filter medium 1 is taken out of the system through the filtrate discharge pipe 37 communicating with the lower chamber 35. A packed bed type filter, which is used by directly filling a container with a filter medium composed of an aggregate of chemical fibers, serves to capture solids substantially only on the upper surface of the packed bed. If it accumulates on the upper surface, the filtration pressure difference becomes high and it cannot be used any more, and the filter medium had to be replaced frequently. Further, solid matter is trapped on the upper surface of the packed bed, and as the packed bed contracts in the height direction, a space is formed between the filter medium and the side wall, and a wall flow may occur, which may cause leakage of solid matter. It was These problems have been alleviated by dividing and filling the filter media into net bags, but have not yet been completely remedied. On the other hand, the filtration of the packed bed filter according to the present invention is performed by a large number of spherical fiber lumps placed in a net bag, and the waste liquid is distributed between the spherical fiber lumps 11 as shown in FIG. As it flows, not only the upper surface of the packed bed,
Large solids are trapped throughout the entire filter medium, ie at the surface of all spherical fiber masses, and small solids are trapped inside. For this reason, the life of the filter medium (filterable period) is much longer than that of the conventional packed-bed type filter and the one using the above-mentioned split net bag type packed layer, and the filter medium is much longer. The replacement frequency can be reduced. Another feature of the present invention is the ease of replacement of the filter media. The fiber lump itself is spherical with a diameter of about 10 to 15 mm and is difficult to handle in a disjointed state, but by putting this in a net bag 12, it can be handled collectively, and as shown in FIG. 1 and FIG. As described above, the filter media 1 need only be put into the filter cylinder one bag at a time and simply stacked, and it is not necessary to consider the filling condition. On the other hand, to take out, it suffices to hook the net bag on some take-out tool and pull it up. Since the processing apparatus of the present invention requires a simple operation for filling and removing the filter medium as described above, the filter medium can be replaced by a remote operation or an automatic apparatus as shown in FIG. 3, for example. The replacement work shown in FIG. 3 will be briefly described as follows. The claw opened from the crane 4 is lowered into the filter cylinder 2 of the packed bed filter 3 with the lid opened, and when the filter medium is reached, the claw is closed and hooked on the net bag 12 to lift the filter medium 1. The crane 4 is moved to a container 5 such as a drum can prepared in advance, the claws are opened, and the used filter medium 1 is dropped into the container 5. If the diameter of the filter medium unit is adapted to the inner diameter of the post-treatment drum, it is easy to handle. Repeated fall to remove all used filter media 1 from filter cylinder 2
Once taken out, a predetermined number of new filter media 1 are put into the filter cylinder 2 manually or by a crane. In this way, the filter medium replacement work can be performed without the worker touching or approaching the filter medium to which the radioactive substance is attached. If the filtrate from which the solid content has been removed through this filtration device is subsequently treated by means such as activated carbon adsorption, the radioactivity can be further reduced. Effects of the Invention The radioactive waste liquid treatment apparatus of the present invention has a long service life of the filled filter medium, and when the waste liquid of a nuclear power plant is used, for example, it may be replaced once or twice a year. Combined with the fact that it itself is easy, operating costs can be reduced. Capital expenditure itself is lower than what has been used so far. Furthermore, the radiation exposure of the worker can be reduced by reducing the number of times the filter medium is replaced and shortening the working time. If the replacement work of the filter medium is remotely controlled or automated, the worker's exposure can be almost eliminated.

[Brief description of drawings]

FIG. 1 is a drawing showing a typical processing apparatus of the present invention, and is a perspective view in which a part is cut away to clarify the internal structure. FIG. 2 is a vertical cross-sectional view schematically showing the flow of waste liquid in the filter cylinder in the treatment apparatus of the present invention. The spherical fiber mass is hatched only for a part thereof. FIG. 3 is a diagram showing a mode in which the processing apparatus of the present invention is used by remote control. 1 ... Filter material 11 ... Spherical fiber block, 12 ... Net bag 2 ... Filter cylinder, 3 ... Packed bed filter 4 ... Crane, 5 ... Container

Claims (3)

[Claims] 1. A device for treating radioactive waste liquid with a packed bed filter, wherein a filter medium unit comprising a large number of spherical fiber lumps put in a net bag is stacked and packed in a filter cylinder in a row in the filtering direction. Processing equipment. 2. The processing apparatus according to claim 1, wherein the radioactive waste liquid is a laundry waste liquid. 3. The processing apparatus according to claim 1, wherein the diameter of the filter medium unit is set to a size adapted to the inner diameter of the post-treatment drum can.