JPS61228395A - Method of treating 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 relates to a radioactive material for drying and pulverizing liquid radioactive waste such as spent ion exchange resin slurry and concentrated waste liquid generated from nuclear facilities such as nuclear power plants. It relates to waste disposal methods.

[Background of the invention]

Nuclear facilities such as nuclear power plants (hereinafter referred to as nuclear facilities)
Liquid radioactive waste, such as slurry and concentrated waste liquid (used ion-exchange resin (hereinafter referred to as waste resin)), has conventionally been subjected to various treatments and management such as cement solidification, asphalt solidification, and tank storage.

However, with the increase in the number of nuclear facilities and the lengthening of their operating history, the amount of radioactive waste that accumulates has become a problem, and there is a strong demand for reducing the volume of waste.

Furthermore, due to the national situation in Japan, where the final disposal policy for radioactive waste has not yet been determined, there has been an increasing demand for long-term stabilization of waste that can withstand interim storage.

In order to meet these demands, we are currently developing dry powdering and granulation that significantly reduces the volume of waste resin slurry and concentrated waste liquid by drying it into powder, and then granulating it to increase the volume reduction effect and stabilize it over the long term. Technology is becoming more practical. In some cases, as an alternative to granulation, a treatment method is being implemented in which powder is mixed and solidified with an assimilated material (such as plastic), which is considered to be sufficient to withstand final disposal.

Regardless of the technology, for liquid radioactive waste such as waste resin slurry and concentrated waste liquid, dry powder processing is considered to be the core treatment method for a long time to come as the latest practical technology. ing.

The outline of the dry powder processing method will be explained below.

Figure 3 shows the flow of conventional dry powder processing equipment. In the dry powder processing equipment, low-concentration waste resin slurry generated at the upstream generation source 1 is collected in a sedimentation separation tank 2, and after sedimentation and separation, the supernatant water is sent to a low conductivity liquid waste treatment system 4 by a decant pump 3. The waste resin is transferred as a waste resin slurry with a predetermined concentration to a waste resin receiving tank 6 by a transfer pump 5, and further transferred to a supply tank 8 by a waste resin receiving pump 7 in a predetermined amount at a predetermined concentration. In addition, the concentrated waste liquid generated in the concentrator 9 is
Similarly, a predetermined amount is transferred to the supply tank.

The waste resin slurry or concentrated waste liquid transferred to the supply tank 8 is supplied to the dryer 11 by the supply pump 10, and the moisture is removed to form a dry powder, which is then sent to the downstream equipment 12 where it undergoes granulation, solidification, etc. Processing is done. Dryer 11
The water removed within the tank becomes steam and is led to the condensate system 13, and after being condensed, is sent to the condensate tank 14. Also, dryer 11
is washed with hot water supplied from the hot water supply device 15 from the viewpoint of both ensuring operational performance and ensuring ease of maintenance and inspection.

This wash water, like the condensed water, is sent to the condensate tank 14. The condensed water and washing water in the condensed water tank 14 are transferred to the high conductivity liquid waste treatment system 17 by the condensed water transfer pump 16. Following the flow of liquid in the drying and pulverization treatment equipment, All of the water that has flowed into the supply tank 8 is transferred to the high conductivity liquid waste treatment system 17 and subjected to concentration treatment again. All the hot water supplied for cleaning will also be transferred to the high conductivity liquid waste treatment system 17 and concentrated again. This is from the perspective of equipment rationalization due to the increased throughput of the high conductivity liquid waste treatment system, that is, the concentrator, which is relatively expensive compared to the low conductivity liquid waste treatment system in terms of equipment costs and operating costs. However, in current dry pulverization equipment, the conductivity of the waste liquid in the condensate tank exceeds the inlet standard of the low conductivity liquid waste treatment system, so the low conductivity Cannot be treated in liquid waste treatment systems.

Moreover, if we pay attention to the solid content flowing into the condensed water tank 14, it is difficult to say that the solid content that flows into the condensed water tank 14 is further dried after passing through the concentrator 9.

As mentioned above, with regard to dry pulverization processing equipment, there are still issues to be solved in terms of rationalization, such as reducing the amount of waste liquid generated and the amount of circulating solids.

Incidentally, a related known example is JP-A-55-142299.
There is a publication number.

[Purpose of the invention]

The purpose of the present invention is to improve the dry pulverization processing equipment so that it can effectively utilize the generated waste liquid, and as a result, the load on the high conductivity liquid waste treatment system is reduced due to the reduction in the amount of generated waste liquid, and the amount of hot water used for cleaning is reduced. It is an object of the present invention to provide a method for treating radioactive waste that can reduce the load on a hot water system due to a reduction in the amount of water and reduce the amount of solid content circulating in the system.

[Summary of the invention]

The present invention was achieved by paying attention to the properties and amount of liquid waste generated at various points during the dry pulverization process.

That is, (1) waste resin slurry is a mixture of waste resin and water, and the waste resin and water can be effectively separated by a simple separation process.

(2) Since the water in the waste resin slurry has low conductivity, it can be treated with a low conductivity liquid waste treatment system. Because the water has been diluted with condensate water generated from the condensate system, its conductivity and solids concentration exceed the acceptance criteria for low conductivity liquid waste treatment systems, but it is not suitable for cleaning water. It fully satisfies the water quality required for water, and even when mixed with separated waste resin and supplied to the dryer,
The amount of increase in solids concentration due to mixing does not significantly affect dryer performance.

(4) Since the waste liquid in the condensed water tank is a mixture of condensed water at about 100°C and washing water at about 60°C, it sufficiently satisfies the water temperature required for hot water for washing.

(5) The amount of waste liquid generated in the condensed water tank is the sum of the amount of water in the waste liquid supplied to the dryer and the amount of hot water supplied for cleaning. When the amount of water is sufficient and is used for both, there is almost no remaining amount and effective reuse can be achieved.

[Embodiments of the invention]

The details of the present invention will be described below. The flow of the dry powder processing equipment according to the present invention is shown in FIG. The part indicated by the thick line in 1 is the part of the present invention.

A separator 18 is installed upstream of the supply tank 8 to separate the waste resin slurry transferred from the waste resin receiving tank 6. 6 The separated waste resin is transferred to the supply tank.

Since the separated water has low conductivity dust, it is transferred to the low conductivity seat body waste treatment system 4 in the same way as the supernatant water of the sedimentation separation tank 2.

A transfer line is installed between the condensed water tank 14 and the supply tank 8 so that the condensed water can be transferred to the supply tank 8.

The transferred condensed water is mixed with the separated waste resin to form waste resin slurry that is supplied to the dryer 11.

A transfer line is provided between the condensed water tank 14 and the hot water supply line to the dryer 11 so that the condensed water can be transferred to the hot water supply line. The transferred condensed water is used as washing water for the dryer 11.

As an alternative method of the present invention, the same result can be achieved by installing the separation device 18 upstream of the waste resin receiving tank 6 and providing a transfer line between the condensed water tank 14 and the waste resin receiving tank 6. Although the functionality is ensured, from the standpoint of equipment operability, it is desirable to install the separation device 18 upstream of the supply tank 8 and to install a transfer line between the condensed water tank 14 and the supply tank 8. .

Furthermore, the degree of separation of waste resin slurry in the present invention is as follows:
From the viewpoint of transportability of dehydrated waste resin, effective use of waste liquid, and performance of the separation device 18, the concentration of waste resin is preferably about 50% to 1t%, but the effects of the present invention can be obtained depending on the degree of separation. . That is, according to the present invention, the object of the present invention can be achieved by performing some kind of separation treatment.

It is also possible to further use each tank as a separator.

As an example of the present invention, a case where the present invention is applied to a radioactive waste treatment facility of a 1 million KW e class boiling water nuclear power plant (hereinafter referred to as BWR) will be described below.

The amounts of waste resin and concentrated waste liquid generated from the 1 million KWa class BWR of this example are approximately as shown in the table below.

The operating conditions of the dry powder processing equipment of this example are as follows.

(1) The number of operating days per year is 250 days.

(2) The waste resin slurry is supplied to the dryer at a concentration of 10 wt%, and the concentrated waste liquid is supplied at a concentration of 25 wt%.

(3) Clean the dryer once a day,
Use 0.5rrl' of water for washing each time.

(4) The entire drying and pulverization processing equipment is washed once every 5 days, and the washing water is used trrt' for each time.

For reference, the amount of waste liquid transferred to the high conductivity liquid waste treatment system and the amount of hot water used in the case where the present invention is not implemented are shown as 465 ri'/year and 150 i/year, respectively.

Example 1 This is a case where a dehydration filter is used as a separation device. Dehydration filters include centrifugal filters, funda filters,
A number of devices such as a draining perforated plate may be used, but in this case, it is possible to achieve a concentration of waste resin of up to about 50 wt% as the degree of separation. That is, in FIG. 1, the quantity from the separator 18 to the supply tank 8 is 240 rn'/year.

By the way, the amount of condensed water and washing water generated in the supply tank is 465 rrr/year, so of this 240 rrr'
/year, 150n? of separated water was returned to the supply tank as make-up water. / year is used as washing water. Therefore, the amount of waste liquid returned to the high conductivity liquid waste treatment system is 7
5rrl'/year, and the amount of hot water used is 0rrl'/year. Moreover, the amount of solids recycled is also about 176 in the case where the present invention is not implemented.

Example 2 A flow sheet of equipment in which a waste resin receiving tank is used as a separation device is shown in FIG. In this example, Example 1
There is no separation device 18; instead, the waste resin receiving tank 6 has the function of a separation device, and a transfer line is provided between the waste resin receiving tank 6 and the low conductivity liquid waste treatment system 4. In this case, the degree of separation is approximately 25 tyt based on the concentration of waste resin.
% (as a mixture of granular and powdered resins).

That is, in FIG. 2, the waste resin is transferred from the waste resin receiving tank 6 to the supply tank 8 at a concentration of 25 υt%. Therefore, the amount of water returned to the low conductivity liquid waste treatment system is 1
80m/year.

By the way, the amount of condensed water and washing water generated in the supply tank is 465 rrr/year, of which 180 rrr/
The separated water is returned to the supply tank as make-up water, and 150 rrl'/year is used as wash water.

Therefore, the amount of waste liquid returned to the high conductivity liquid waste treatment system is 135 rrr/year, and the amount of hot water used is 0 rrr/year. Furthermore, the solid content in ms is also about 1/3 of that in the case where the present invention is not implemented.

-1 Results [Effects of the Invention] The effects of implementing the present invention are as follows.

(1) The amount of waste liquid brought into the high conductivity liquid waste treatment system can be significantly reduced compared to conventional methods, up to 1/6
It can be reduced to a certain degree.

(2) The amount of hot water used for cleaning is approximately 0.

(3) Along with the effect described in (1), the amount of solid content circulating through the liquid waste treatment system can be greatly reduced to about 176 at most.

Of the three effects when implementing the present invention, effect (1)
) will no longer be effective if low conductivity liquid waste and high conductivity liquid waste are collectively treated in the future, but effects (2) and (3) will have exactly the same effect. have

[Brief explanation of the drawing]

FIG. 1 is a flow sheet of a dry pulverization treatment facility for radioactive waste according to the present invention, and FIG. 2 is a flow sheet for a dry pulverization treatment facility for radioactive waste according to an embodiment of the present invention.
FIG. 3 is a flow sheet of a conventional dry powder treatment facility for radioactive waste.

Claims (1)

[Claims] 1. In equipment that has a supply tank for used ion exchange resin slurry generated from nuclear power facilities such as nuclear power plants and dry powders liquid radioactive waste such as concentrated waste liquid, A radioactive waste treatment method characterized by mixing ion exchange resin and condensed water generated from a dryer and supplying the mixture to the dryer. 2. A radioactive waste disposal method according to claim 1, characterized in that a part of the condensed water generated from the dryer is used as washing water for the dryer. 3. A method for treating radioactive waste according to claim 1, characterized in that the used ion exchange resin and condensed water generated from a dryer are mixed in a supply tank.