JPS60146200A - Method of filling 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 method for filling containers with solid radioactive waste, and particularly to a filling method suitable for reducing the volume of waste after filling. Ru. .

[Background of the invention]

The amount of solid waste (mainly metal) generated at nuclear power stations, etc. is increasing due to the increase in the number of power generation plants and the increase in regular inspections and modifications, and the amount of solid waste currently stored in drums is It has reached hundreds of thousands of copies. Also, decommissioning measures (hereinafter abbreviated as decommissioning) after the shutdown of the reactor in the near future
At times, large amounts of (radioactive) waste can be expected to be generated within a short period of time. Disposal of these wastes, such as storage or dumping, is being considered, and therefore reducing the volume of the wastes as much as possible has become an urgent issue. Concerning concentrated waste liquid, powdered or granular used resin, etc., methods of solidifying after pulverization are being considered, and in order to further reduce the volume, it is possible to thermally reduce the volume by acid decomposition, incineration, etc. Research and development is also being conducted on the following. The present invention was developed based on the above background and aimed at reducing the total amount of solid waste generated.

Regarding the conventional filling method for radioactive waste, the filling container is a 200-liter drum specified in Japanese Industrial Standard Z-1600 [Steel Open Drum (200t) J, or various types of steel, φ wood, or concrete. Containers (mainly rectangular) are used, and measures such as shielding the inside or outside of the drum (container) with lead or concrete are taken to ensure the surface dose rate of the container. Surface line with shielding, η
1- The rate is stipulated in the Vehicle Transport Regulations for Radioactive Isotopes, etc.7
200 millirem/hour at the surface of the container, and 10 millirem/hour at a distance of 1 meter from the surface.Special permission has been obtained from the Director-General of the Science and Technology AgencyV(
Therefore, 1000 mrem per hour on the surface of the container,
At a distance of 2 meters from the surface, it is said to be 10 millirem per hour.

In normal waste, 2200 mi II v
1 at a distance of 1 meter from the surface per hour
0 miIJ vm hourly standard is applied and to comply with this standard the following method is adopted.

(1) Necessary and sufficient shielding (build) depending on the radioactive clay filled
1. (2) The total amount of radioactivity (amount of waste) to be filled is limited depending on the shielding (thickness).

(3) Combining (1) and (2) above. .

As an example of evaluating generated waste, let us consider and explain the waste generated during tecommission. As an example of evaluation conditions, 100
During the 40-year design life of a 10,000-kilowatt-class nuclear power plant, 7
It is assumed that the system is operated at an operating rate of 5%. There are various kinds of waste generated during tecommission, but the waste is at the level of crow (
The waste, which is generated as more than 10 microcubes per duram), is generated by activation by neutrons from fuel rods in the vicinity of the reactor core in the reactor pressure vessel.

The main high-V bell waste includes shrouds, core spray spargers, core supports, etc.

Unsuitable level waste (assuming an average radioactivity of 5 x 10' microcuries) is evaluated to be stored in a container with internal dimensions of 1 cubic meter as shown in Figure 1. In this case, if the target waste is cut into pieces of approximately 80 cm according to the internal dimensions of the container using a remote device and then filled, the filling rate into the container will vary depending on the shape of the target waste.
It will be about 3 inches. The shielding thickness necessary to make the surface IIjl゛ rate of the present filling container less than 200 millimeters per hour is about 34 centimeters, as shown in FIG. 2, when the shielding material is iron. Figure 2 shows the R developed by the Japan Nuclear Ship Association.
It was evaluated using AC code.

In the container shown in Fig. 1, ll1 is a (radioactive) waste filling area, 2 is a container structure that also serves as a waste shield, 3 is a waste inlet and a shielding lid space, and 4 is a hook for the container mobile phase. . In this container, the waste filling capacity is 1 cubic meter, and considering the above filling rate, it is possible to fill it with 330 lindres, or about 2.6 tons of waste.

From the above results, when storing 1 cubic meter of high-level waste (approximately 2.6 tons in bulk), it is necessary to use a rectangular container with a side of approximately 1.7 meters (including shielding) (with a weight of approximately 31 tons). tons), and it would be necessary to handle it as waste that is approximately five times the volume and approximately 13 times the weight.

Similarly, radioactive materials near the reactor pressure vessel that are located in locations with low neutron flux (pressure vessel itself, separators, reactor containment vessel itself, etc.) and radioactive materials that are generated as medium- and low-level waste are There are pipes and equipment for systems contaminated by fluids, waste treatment systems, etc. Due to the need for shielding to prevent the spread of contamination and reduce radiation exposure, consideration is being given to storing these medium- and low-level wastes in containers of a different shape from those for the high-level wastes.

A rectangular copper container with internal dimensions of 1.48 meters x 2.98 meters is being considered as a container for books, medium and low novels, and the filled volume of this container is approximately 6.5 cubic meters.

Regarding high-level V-bell waste (average radioactivity concentration ['klO mithalocyri per dalam dalam)], the necessary shielding is applied to the same surface as above and to satisfy the linear radiation rate at a distance of 1 meter from the surface. Evaluating the thickness, as shown in Figure 4, a shielding thickness of approximately 6 centimeters is required, and a volume of approximately 1 cm.
．． It will be necessary to treat it as waste that is twice as heavy and about 1.5 times its weight.

As mentioned above, high level and medium and low level waste are stored separately in containers, which increases the load on waste storage due to the increase in waste volume and weight. This has resulted in an increase in handling work during movement and transportation.

[Purpose of the invention]

An object of the present invention is to provide a filling method that overcomes the above-mentioned drawbacks and reduces the increase in volume and weight of target waste after filling the container.

[Summary of the invention]

(Solid) radioactive waste to be filled into containers is divided into high-level waste with high specific radioactivity and medium-low level waste with low specific radioactivity, based on the difference in the amount of radioactivity contained (VC). In order to reduce the total rate of high-level waste u surface wires,
Although it is necessary to increase the shielding thickness, the present invention is characterized in that the medium-low level waste itself is used as a shield for high-level waste, and the use of new shielding materials other than the target waste is minimized. The feature is that the total volume and total weight of waste after filling the container can be kept small.

[Embodiments of the invention]

First, the principle of the filling method according to the present invention will be explained using FIG. 31. FIG. 3 schematically represents the structure of the filling method according to the present invention. In other words, assuming the entire container has a multilayer structure as shown in Figure 3A, high V-bell waste (11) is placed in the center, medium and low level waste (12) is placed around it, and the container structure and shield is placed around it. Material (14) is installed r+.

In other words, since 11 has a high specific radioactivity, it requires a large shielding thickness, but instead of using a new shielding material for 11, it is possible to use waste 12, which conventionally should be filled in a container with a different shape, instead of using a new shielding material. f17 is used as a shielding material. In this method, 1
2 is also metal waste, and can be expected to have the same effect as new conventional shielding materials, and by applying 12 around 11 in the center, it is possible to increase the distance, which is the principle of reducing radiation exposure. The principles of "distance" and "shielding" are met. 14 is a structure that ensures the integrity of the entire container, and at the same time has a surface dose rate of 20 millirem per hour and a position 1 meter away from the surface as indicated in the regulations for vehicle transportation of radioactive isotopes. It serves as a shield to comply with the wall-to-wall dose rate of 10 millirem/hour. The required shielding thickness of 13 is estimated by filling waste 11 and 12, but it is sufficiently absorbed by 1IFi12, and in fact the required thickness of 14 is the same as that required to absorb the radioactivity of 12. Determined by shielding thickness.

From the above, in the method of the present invention, new μ! except for 13 are created. :
: mNt & chair, total amount of waste after filling the container (B), it is possible to reduce the total amount of M.

As an example of evaluating the surface AIM rate, as in the conventional example, if VC1 radioactivity concentration is 5 x 10' microcuries per Durham high level waste is filled to 11 and the bulk density is 1 cubic meter, σ) and 1- . At this time, considering the shape of the target high-level waste and assuming a filling rate of 33%, the packing density is:
Approximately 2.6 grams per cubic centameter. Change vc1
As for 2 and 7, iron waste with a radioactivity concentration of 10 microguiries per duram is used, and from 11 it is assumed that the surface angle direction is [60 cm jq. At this time, the packing density of 12 [[, approximately 3.9 grams per cubic centimeter]. ” - The required shielding thickness for 14 under the conditions described is 1
i by 1! ! ]11 is due to absorption by 12,
It was evaluated that the results were almost the same as those shown in Figure 4, which were used to evaluate the required shielding thickness for medium- and low-level waste using the conventional method. That is, the shielding thickness required for 14 is:
It is estimated to be approximately 6 centimeters.

As the next evaluation example, a case where the container has a four-fold structure as shown in FIG. 3(B) will be shown. 1 in Figure 3 (B)
1 is high-level waste Q with a radioactivity concentration of 108 microcuries or more, '12 is medium-level waste with a radioactivity concentration of 1 to 103 microcuries per gram σ], and 13 is a radioactive concentration of 1 Microcuries are filled at low levels below every Durham. Also in this evaluation example, 13 is 12,
11σ) As the shielding paulownia, 12 is used as the shielding material of 11, and the same effect as in the evaluation example can be considered.

The British Norwell Institute classification was used to classify radioactivity levels into improved, medium, and low tNe.

Next, the operating method of this filling method will be explained with reference to FIGS. 5 and 6.

In FIG. 5, 11 is cut into the shape of a high-level waste container (24) by a remote cutting device (21). The cut high-level waste (22) is also loaded into the remote transport device (23>K, 24)1. Ru. On the other hand, medium-low level waste is compressed into a plate shape using a high-pressure press or shredded due to its shape and other characteristics.
Shredded with a trowel.

Figure 6 explains the V-trowel filling procedure. In Figure 6,
(31) and (33) are medium-low level waste compressed into a plate shape using a high-pressure press, and (32) is medium-low level waste shredded using a shrender.

In the charging order, 1c (31) first fills the bottom of the filling container. Next, 24 filled with the shredded high-level waste described in FIG. 5 is filled, and then 3
2 is filled. Finally, 33 is filled again and the lid on the top of the container is closed.

After that, the container surface was inspected for contamination and the surface and nitride line percentage at a distance of 1 meter from the surface were confirmed.
recorded. After recording the confirmation, the filled container will be
transported outside the power plant for waste storage or waste dumping. - In the above embodiment, the transportation standard weight of 30 tons on the axle is satisfied.

In the above explanation, compressed plate-shaped waste is placed at the bottom and top.
It is assumed that shredded waste will be filled in the middle part, but depending on the amount of medium and low level waste generated for each type, shredded waste will be filled in the bottom and top, and vice versa, plate-shaped waste will be filled in the middle part. It is also possible.

〔Effect of the invention〕

According to the present invention, as a shielding material for high-level waste, a waste container after filling is used to use medium- and low-level waste that has been filled in other containers in order to minimize the use of new materials. It becomes possible to reduce capacity and weight.

As an example, considering the waste generated during tecommissioning, when processing 50 cubic meters of high-novel waste and 500 cubic meters of medium-low level waste, with the conventional method, the volume after filling the container was approximately 810 cubic meters. According to the filling method of the present invention, the volume is approximately 580 cubic meters, which is a volume reduction of approximately 30%.

Furthermore, by reducing the volume (weight) of waste, it is possible to reduce the number of man-hours required for transporting containers, and it is also possible to reduce the number of waste storage facilities, waste disposal sites, etc. where containers are stored or disposed of.

[Brief explanation of drawings]

Figure 1 is a conceptual diagram showing an example of the shape of each layer of conventional high-level waste filling, and Figure 2 shows the shielding thickness and surface dose rate when high-level waste is filled in a 1 cubic meter internal volume container. Figure 3 is a principle diagram showing a filling method according to an embodiment of the present invention. A graph showing the relationship between the shielding thickness and the surface dose rate in the example, FIG. 5 is a flow diagram showing the procedure for filling the interior with high-level waste in the example of the present invention, and FIG. It is a conceptual diagram which shows the filling order in an example. 2... Shielding material, 4... Container transfer funk, 11
... High level waste, 12 ... Medium (low) level waste, 13 ... Low level waste, 14 ... Shielding material, 2
1... Distant shielding Cm) Day 31!1 (A) iL shielding Ctn) Day 5 3 2

Claims (1)

[Claims] 1. In the method of filling radioactive waste into containers, use a multi-layered structure in which surface waste with a radioactive level is filled in the center, and waste with a low radioactive level is filled on the outside so as to surround highly radioactive waste. A radioactive waste filling method characterized by: