JP2507477B2 - Radioactive waste treatment system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention relates to a system for treating radioactive metal waste, and particularly to a large amount of waste, and its radioactive level, radioactive type, and shape. The present invention relates to a radioactive waste treatment system capable of efficiently treating various types of radioactive metal waste.

(Prior art) The life of a nuclear power plant is said to be 30 to 40 years,
A nuclear power plant that has reached the end of its life will be dismantled and removed after being sealed and controlled for a certain period. A large amount of radioactive waste is generated during the decommissioning of this nuclear power generation facility in a relatively short period of time, and the generated radioactive metal waste is in the shape, size and dimensions of heat exchangers, tanks, pipes and valves. It has features such as a wide variety of radioactivity levels and types of radioactivity. An extremely large-scale storage facility or disposal facility is required to store, store, or dispose of radioactive metal waste by subjecting these wastes to measurement, discrimination, cutting, decontamination, packaging, etc. At the same time, the exposure of workers associated with processing and the exposure of the public from storage facilities or disposal facilities becomes a problem. On the other hand, although the scale of maintenance and improvement of operating nuclear power generation facilities is small, there is a similar amount of radioactive metal waste generated in Japan as a whole.

Therefore, it has features such as a large variety of shapes, dimensions, radioactivity levels, radioactivity types, etc., which are generated due to decommissioning of nuclear power generation facilities and maintenance and improvement of operating nuclear power generation facilities. Providing an efficient treatment system for radioactive metal waste makes it possible to significantly reduce the amount of radioactive waste generated. In addition, the scale of the radioactive waste storage facility can be reduced, and waste that has been thoroughly decontaminated can be reused until it can be handled as ordinary waste, which enables effective use of resources. . Furthermore, since the amount of radioactive waste generated can be greatly reduced, it is possible to reduce the exposure of workers and the public.

(Problems to be solved by the invention) Until now, radioactive metal wastes have been individually measured, cut, decontaminated, reduced in volume, packed in containers, etc., and systematized as a whole to optimize the system. The efficiency has not been achieved by doing so. Radioactive metal wastes are roughly classified into radioactive metal wastes and radioactive contaminated metal wastes, and decontamination is not possible because radioactive metal wastes have been activated up to the metal base material. Radioactivity can be decontaminated from metal waste by removing an oxide film such as a clad and a part of the base material surface layer. Therefore, it is necessary to distinguish between radioactive metal waste and radioactively contaminated metal waste by the discrimination based on the information from the waste generation site or the radionuclide composition ratio measurement during the measurement process. The cutting process is mainly for packing waste, reducing the volume,
It is implemented to facilitate decontamination. However, an excessive cutting process is useless from the viewpoint of the entire processing system, and therefore a reasonable judgment is required. The decontamination treatment is classified into a chemical decontamination method, a mechanical (physical) decontamination method, a physicochemical decontamination method, and an electrochemical decontamination method, in principle. Decontamination has been developed mainly for system decontamination of primary reactor system and decontamination during service period of equipment. The purpose of these decontamination methods is to remove the oxide film of the decontaminating metal surface without deteriorating the soundness of the metal base material. On the other hand, on the surface of metal waste such as equipment, pipes, valves, etc. that are generated due to decommissioning of nuclear power generation facilities and maintenance / improvement of operating nuclear power generation facilities, clad (Co-60 etc.) etc. It is considered that some oxide films have been deposited for a long period of time and that radioactivity has penetrated into the base material along the crystal grain boundaries. Therefore, decontamination reduces the radioactivity level to the level of general waste. In order to do so, in addition to the conventionally developed decontamination method, a powerful decontamination method that also dissolves the surface layer of the base material is required. Furthermore, there are a wide variety of shapes of these wastes, and the materials are roughly classified into carbon steel and stainless steel, and in order to perform decontamination efficiently, it is rational considering the material, shape, and radioactive contamination level of the waste. A decontamination method is required. In addition, it is necessary to measure the radioactivity level of the waste after the decontamination process and determine whether it is below a predetermined radioactivity level. Regarding the wastes with a predetermined radioactivity level or higher, those with a relatively high radioactivity level need to be reduced in volume as necessary for disposal and then packed in containers.

At this time, depending on the request of the disposal destination, the radioactivity amount (Bq) of the packed waste, nuclide analysis, surface dose (also called surface dose equivalent rate) (Sv / h), weight, etc. are measured. Regarding the various treatments mentioned above, individual or in some cases, a combination of some treatments is being considered, but it is necessary to have a radioactive waste treatment system that is rationalized and efficiently combined. Become.

The present invention has been made in view of the above circumstances, and the purpose thereof is to generate a large amount due to decommissioning of nuclear power generation facilities, maintenance of nuclear power generation facilities, improvement, etc.
To provide a radioactive metal waste treatment system that can be efficiently treated by combining a radioactive metal waste having a wide variety of types and shapes of radioactivity with a treatment method with a rational configuration. is there.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, in the present invention, the radioactive level and the kind of activity of the received radioactive metal waste are measured to measure the waste. A first discriminating process for discriminating the necessity and possibility of cutting and the possibility of decontamination together with shape recognition;
Based on the first discriminating process, a cutting process is performed on those that need and can be decontaminated, and the cut decontaminating waste is cut with the uncut decontaminating waste together with a predetermined radioactivity. After performing decontamination treatment up to the level, the second measurement of the radioactivity level is performed again, and the waste that has been decontaminated to the prescribed radioactivity level and the waste that cannot be decontaminated are measured and discriminated. For the waste that was judged to be unable to be decontaminated up to the prescribed radioactivity level by the measurement of the above, along with the waste that was judged to be decontamination impossible by the first discrimination process, Waste that was determined to have been decontaminated to a very low level according to the second measurement, and then simply disposed of, and waste that was determined to have been decontaminated to the prescribed level according to the second measurement About one Contribute to the disposal or reuse of as waste.

In addition, the volume of waste to be packed in containers is reduced and then packed, and after packing, the radioactivity (Bq), surface dose (also called surface dose equivalent rate) of the container (Sv /
h), perform the weight measurement process.

(Operation) In the system configured in this way, the radioactive level and the type of activity of the received radioactive metal waste are measured and the shape of the waste is recognized to determine whether to perform cutting and decontamination. . The radioactive metal waste determined to be cut is cut into a predetermined shape. Subsequently, the radioactive metal waste determined to be decontaminated is subjected to decontamination processing up to a predetermined radioactivity level according to the radioactivity level, the material, and the shape. After the decontamination process, the radioactivity level of the metal waste is measured, and the decontaminated material below the predetermined radioactivity level is disposed of or reused in the same manner as general waste. Of the radioactive radioactive metal waste that was determined to be impossible to decontaminate in the first measurement and those that were not decontaminated below the prescribed level in the measurement after decontamination, For high-waste materials, those that can be expected to have a volume-reducing effect are subjected to a reducing treatment and then packaged.
After packaging, the radioactive waste (Bq), nuclide analysis, surface dose (also called surface dose equivalent rate) (Sv / h), weight, etc. of the packaged waste are measured and then disposed of, depending on the disposal destination. To be done.

Radioactive radioactive metal waste that was determined to be impossible to decontaminate in the first measurement, and extremely low-level waste that was not decontaminated below the prescribed level in the measurement after decontamination Are simply disposed of.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention. The radioactive metal waste received in the receiving step 1 is for reading information (type, material, etc.) from the waste generation site and a waste transfer container. After the acceptance processing such as the transfer from the, the activity level and the activity type are measured in the measurement processing step 2. Subsequently, in the measurement processing step 2, whether or not decontamination is possible is determined based on the measurement result and the information from the waste generation site, and the decontamination-processable waste is sent to the decontamination processing step 3 for decontamination processing. Impossible waste is sent to the container filling process 6 or the simple disposal 8. Whether or not decontamination is possible here is made based on whether the waste is radioactive radioactive material or contaminated radioactive material, whether the shape of the waste is decontaminating, or whether the level of radioactivity can be expected to have a decontaminating effect. It For the radioactively contaminated metal waste sent to the decontamination treatment step 3, the treatment level for decontamination up to the prescribed radioactivity level is selected based on the result of the measurement treatment step 2 and the information from the waste generation site. And decontamination is performed. After the decontamination treatment, the waste is sent to the measurement treatment step 4 and the radioactivity level is measured again, and it is determined whether the decontamination up to the predetermined radioactivity level has been completed.
Discrimination is performed. As a result, the wastes that have been decontaminated to a predetermined level of radioactivity are either disposed of as ordinary wastes 5 or reused from the viewpoint of effective use of resources. Regarding the wastes that could not be decontaminated to a predetermined radioactivity level, those having a relatively high radioactivity level from the measurement results are sent to the container filling process 6, and those having an extremely low level are simply disposed of 8. In the container filling process 6, after the waste is filled in the container, grout or the like is injected for stabilization treatment, and then storage or disposal 7 is performed.

With the radioactive waste treatment system, the wastes shown in Table 1 were treated, and as a result, the wastes shown in Table 2 were obtained.

Table 1 shows the weight of radioactive metal 1400 tons and contaminated metal 9600 tons in the radioactive metal waste 11000 tons received in the receiving step 1 for each radioactivity level. In addition, Table 2 shows the relationship between the radioactivity level and the weight divided into general waste 7120 tons and radioactive waste 3880 tons after being treated by the radioactive waste treatment system of the above-mentioned embodiment. This is the result of dividing the received waste by the measurement processing step 2 and reducing the amount of radioactive waste and reducing the radioactivity level by the decontamination processing step 3. It was recognized that it can be classified into.

As a result of the above, according to this system, the amount of radioactive wastes with different types of wastes, radioactivity levels, and modes of radioactivity (contamination radioactivity / activated radioactivity) can be reduced (general waste standardization) and It has the effect of reducing the level of radioactivity and being able to sort by disposal destination.

FIG. 2 shows a second embodiment in which the volume reduction processing step 9 is added before the container filling processing step 6 post-disposal processing 7. Devices similar to those in FIG. 1 are designated by the same symbols. The functions of other processing steps are the same as those in the first embodiment.

By carrying out the volume reduction treatment step 9 shown in this embodiment, there is an effect of reducing the number of containers to be disposed, and handling and transportation at the time of disposal are facilitated.

FIG. 3 shows a third embodiment in which the cutting treatment step 10 is added between the first measurement treatment step 2 and the decontamination treatment step 3. Devices similar to those in FIG. 1 are designated by the same symbols. The functions of other processing steps are the same as those in the first embodiment. Cutting process shown in this embodiment
By performing 10, the decontamination efficiency during the decontamination process and the filling efficiency during the container packing process are improved. In particular, the effect of improving decontamination efficiency during decontamination treatment is effective for waste having a complicated shape. Specifically, such as the ease of facing the electrode during electrolytic polishing decontamination, the ease of contact with the strong chemical decontamination solution during the strong chemical decontamination, the ease of contact with the blast material during the blast decontamination, etc. Therefore, it is effective.

Therefore, the effects of reducing the amount of radioactive waste (general waste standardization) and reducing the level of radioactivity described in the first embodiment are further promoted, and the filling efficiency into the container is improved to reduce the number of containers. Has the effect of reducing.

FIG. 4 shows a fourth embodiment in which a measurement processing step 11 for the stored radioactivity, nuclide analysis, surface dose, weight, etc. of the container is added after the container filling processing step 6 in the third embodiment. It is a thing. These measurement processes show specific examples corresponding to the case where the conditions of acceptance and transportation of the disposal destination require. By carrying out the measurement process that satisfies these requirements, it is possible to properly dispose of the waste after the process.

FIG. 5 shows a fifth embodiment in which a volume reduction processing step 9 is added before the container filling processing step 6 in the fourth embodiment. This volume reduction process is performed to compensate for the lack of volume reduction effect due to the cutting process, and specifically, there is a high compression process. At this time, the volume reduction by the cutting process is set to the minimum necessary for easily performing the high compression process, and the volume reduction effect by the high compression process is maximized, whereby the optimization can be achieved. This is because the high compression process is easier than the cutting process. This processing has the effect of further reducing the number of containers in the fourth embodiment and the effect of reducing the load of the cutting processing.

The present invention is not limited to the embodiment shown in FIG. 1 to FIG. 5, and for example, the measurement treatment step 2, the cutting treatment step 10, the decontamination treatment step 3, the measurement treatment step 4, the volume reduction treatment. The process 9 and the container filling process 6 do not have to be one system and may be installed in a plurality of systems. It is obvious that this can further improve the processing capacity. When radioactive waste is mixed with general waste, it is discriminated as general waste by the first measurement processing step 2 and disposed as general waste 5 or reused as shown in FIG. It is obvious from the process chart of FIG.

[Advantages of the Invention] According to the radioactive waste treatment system of the present invention,
Reasonable efficiency of radioactive metal wastes that are generated in large quantities due to decommissioning of nuclear power generation facilities, maintenance and improvement of nuclear power generation facilities, etc., and have extremely different radioactivity levels, types of radioactivity, and shapes. It is handled well. As a result, the amount of radioactive waste can be reduced and the waste can be disposed reasonably because it is disposed. As a result, the radiation exposure of workers and the general public can be reduced, and the waste disposal cost can be reduced.

[Brief description of drawings]

1 to 5 are process diagrams showing a radioactive waste treatment system according to an embodiment of the present invention. 1 …… Receiving treatment process 2 …… Measurement treatment process 3 …… Decontamination treatment process 4 …… Measurement treatment process 5 …… General waste (reuse) 6 …… Containing treatment process 7 …… Disposal 8 …… Simple Disposal 9 …… Volume reduction process 10 …… Cutting process 11 …… Measurement process

Claims (3)

(57) [Claims] 1. A first discrimination for determining the radioactivity level and the type of radioactivity of the received radioactive metal waste, and for recognizing the shape of the waste and discriminating the necessity and the possibility of cutting and the possibility of decontamination. Based on the treatment and the first discriminating process, cutting and decontamination are performed on those that are necessary and possible, and the cut decontaminating waste together with the undecontaminating decontaminating waste is prescribed. After performing decontamination treatment up to the radioactivity level of
It was judged that the decontamination could not be done up to the prescribed radioactivity level by the second measurement by measuring and discriminating between the wastes that could be decontaminated up to the prescribed radioactivity level and the wastes that could not be decontaminated by measuring In addition to the waste judged to be decontaminating by the first discrimination process, the waste with a relatively high radioactivity level is packed in a container and then disposed of. It is characterized in that the wastes judged to be decontaminated are simply disposed of, and the wastes judged to be decontaminated to a predetermined level by the second measurement contributes to the disposal or reuse as general wastes. Radioactive waste treatment system. 2. The radioactive waste treatment system according to claim 1, wherein the waste to be packed in the container is reduced in volume and then packed in the container. 3. The radioactive waste treatment system according to claim 1, wherein after the container is packed, the amount of radioactivity, surface dose and weight of the container are measured.