JP2014137253A - Method for treating radiation-contaminated soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating radiation-contaminated soil capable of rationally performing management, treatment, disposal, when soil, vegetation and the like around the outside of an atomic power plant are contaminated by radiation due to an accident or the like at the atomic power plant.SOLUTION: A method for treating radiation-contaminated soil in the outside of a radiation-controlled area such as an atomic power plant comprises the steps of: sorting the radiation-contaminated soil into different contamination levels; and applying treatment or disposal for reducing radioactivity concentration in accordance with the sorted contamination levels.

Description

  The present invention relates to a method for treating radioactively contaminated soil.

  Wastes contaminated with radioactive materials generated in radiation control areas such as nuclear power plants are all classified and managed as radioactive wastes regardless of the contamination level. In this way, the waste generated in the radiation control area is managed as radioactive waste, and finally subjected to a predetermined treatment and then buried in a radioactive waste disposal facility. A series of processing and disposal is completed by this burying disposal (final disposal).

  In general, radioactive waste is usually solidified with cement or the like and subjected to the above-mentioned final disposal.

JP-A-4-245000 JP 2004-77162 A

  By the way, in the accident at the Fukushima Daiichi nuclear power plant, a large amount of contaminated soil was generated around the power plant site. In this way, contaminated soil generated outside the power plant site is collected by decontamination work and stored in a temporary storage site or intermediate storage facility, and after appropriate storage, it is finally stored after about 30 years of storage. To be disposed of.

  Specifically, contaminated soil, etc. is collected through decontamination work such as decontamination of buildings and removal of several centimeters of surface soil, filled in flexible container packs, etc., and accumulated in temporary storage, for up to 3 years. Stored and stored. After that, contaminated soil and the like are received by an intermediate storage facility for processing, and stored and stored for about 30 years.

The Ministry of the Environment has estimated that the amount of contaminated soil, etc. generated by decontamination due to the accident at the Fukushima Daiichi Nuclear Power Station is approximately 28 million m ³ from within Fukushima Prefecture and approximately 13 million m ³ from other regions. The total is estimated to be about 41 million m ³ . This amount corresponds to the amount of about 34 cups of Tokyo Dome and is a very large amount. These large amounts of contaminated soil, etc. are stored in a temporary storage area for about 3 years, then stored in an intermediate storage facility for 30 years, and then subjected to final disposal.

The intermediate storage facility is planned to be treated with contaminated soil with processing equipment. If 28 million m ³ of soil generated in Fukushima Prefecture is stored in a pit with a depth of 10 m, a site of about 2 km x 2 km will be required.

  Providing all such a large amount of contaminated soil for final disposal is a major issue from the viewpoint of final disposal costs and securing a final disposal site. For this reason, it is required to treat such a large amount of contaminated soil appropriately, including recycling, depending on each radioactivity concentration by processing such as separation and decontamination.

  Now, pollutants such as contaminated soil are generated within the power plant site. Therefore, for example, Patent Documents 1 and 2 describe examples in which the radioactive concentration of a contaminant (concrete) is measured and decontamination is performed based on the measurement result.

  As described above, Patent Documents 1 and 2 describe that decontamination is performed according to the radioactive concentration of the pollutant generated in the power plant site. However, there is no disclosure about decontamination according to the radioactive concentration outside the power plant site. It is probable that before the accident at the Fukushima Daiichi NPS, it was not predicted at all that a large amount of contaminated soil would be generated outside the premises.

  By the way, the amount of contaminated soil generated outside the power plant site is much larger than the amount of contaminated soil generated inside the power plant site. Therefore, there is a problem that enormous costs are required to decontaminate these contaminated soils. Therefore, it is very important to decontaminate contaminated soil generated outside the power plant site efficiently and at low cost.

  Therefore, the object of the present invention is to provide a radioactive contaminated soil that can be reasonably managed, treated and disposed of when soil or vegetation in the surrounding area of the nuclear power plant is contaminated with radiation due to a nuclear power plant accident or the like. It is to provide a processing method.

  In order to solve the above problems, the present invention provides a method for treating radioactively contaminated soil outside a radiation control area such as a nuclear power plant, a step of separating the radioactively contaminated soil according to a contamination level, and the separated contamination. And a step of performing treatment or disposal for reducing the radioactivity concentration according to the level.

  According to the present invention, radioactive soil contaminated soil can be rationally managed, treated and disposed of when soil or vegetation in the vicinity of the nuclear power plant is contaminated with radiation due to a nuclear power plant accident or the like. Can provide a method.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is a flowchart which shows the processing method of the radioactive contamination soil which concerns on Example 1 of this invention. It is a flowchart in the case of implementing rough classification and dividing into a low-dose processing line and a high-dose processing line in the former stage of FIG. It is the processing flow figure which provided the judgment step after fractionating by a radioactivity density | concentration at each step. It is a graph which shows the radioactive concentration distribution estimation of contaminated soil. It is a graph which shows the radioactive distribution estimation of the contaminated soil which showed the ratio for which 8000 Bq / kg or less occupies. It is a graph which shows the range at the time of performing the decontamination (DF = 2) process of the decontamination factor 2 to contaminated soil etc. It is a graph which shows the range of the soil at the time of performing attenuation for 5 years to contaminated soil etc. It is the graph which showed the case where a decontamination (DF = 2) process was implemented and it attenuate | damped for 5 years. It is the graph which showed the result of the radioactivity density | concentration when decontamination (DF = 2) was implemented and it attenuate | damped for 30 years. It is a graph which shows the range of the soil of 1,300 Bq / kg or less and the soil of 2,600 Bq / kg or more. It is a graph which shows the range of -1300 Bq / kg of soil. It is a graph which shows the range of the soil of 1,300-2,600Bq / kg. It is a graph at the time of carrying out a decontamination (DF = 2) process and further attenuating for 5 years. It is a graph at the time of carrying out a decontamination (DF = 2) process and further attenuating for 30 years.

  According to various studies, Cs-137 and Cs-134 are the main radioactive substances contained in the contaminated soil and the like, and are present at a ratio of about 1: 1, respectively.

Since Cs-137 and Cs-134 are radioisotopes and have the same chemical characteristics, it is unlikely that this ratio will change. Cs-137 has a half-life of about 30 years, and Cs-134 has a half-life of about 2 years, which initially exist in a ratio of about 1: 1, so about 1/2 in 5 years and about 1 in 15 years. / 3, decays to about 1/4 in 30 years (see Table 1).
[Half-life: the time required for the radioactivity concentration to decay to 1/2]
Cs-137 (half-life 30 years) has a long half-life and cannot be expected to significantly decrease during a storage period of several years, but Cs-134 (half-life 2 years) has a short half-life and can be expected to be sufficiently attenuated. Actually, as described above, since CS-137 and CS-134 are mixed in a 1: 1 ratio, attenuation can be expected even during a storage period of several years.

  It is estimated that the radioactive concentration of the contaminated soil has a distribution as shown in FIG. This is an approximate value calculated by estimating the radioactivity concentration on the ground surface from air dose rate data for each area in Fukushima Prefecture. The radioactivity concentration in the soil has a median of about 10,000 Bq / kg and is distributed around it. Due to the high radioactive contamination area, the distribution is tailed higher.

  In this way, a specific and practical target method can be considered by estimating the specific radioactivity concentration of the contaminated soil.

  On the other hand, unlike the radioactive waste, the contaminated soil and the like can be disposed of or reused at an industrial waste disposal site when the radioactive concentration is below a predetermined value, unlike the radioactive waste. Specifically, contaminated soil of 8,000 Bq / kg or less and incinerated ash of 100,000 Bq / kg or less are allowed to be disposed of at general industrial waste disposal sites. In addition, it is said that concrete pieces can be used as roadbed materials for road and seawall development by taking certain measures if they are 3,000 Bq / kg or less.

  Although these figures may change in the future, contaminated soil, etc. will be reused at appropriate destinations by reducing the radioactivity concentration, disposed at the industrial waste disposal site, or the final disposal site for contaminated soil. I can do it.

As a measure for reducing the radioactivity concentration, there are methods such as attenuation and decontamination of the above-mentioned radioactivity, and it is desired to treat them efficiently by combining them.
[The actual situation of contaminated soil]
The radioactive material contained in the contaminated soil is not uniformly dispersed. The radioactive material released from the Fukushima Daiichi Nuclear Power Station fell uniformly to the surface of the earth in a certain area, but a part of it was washed away by rainwater etc. due to the subsequent rainfall, and part of it was a clay component in the soil. In addition, fine clay components are moved by rainwater and so on. In fact, hotspots with unusually high air dose rates have been found in specific locations. In addition, radioactive materials penetrate into the ground, but according to various surveys, they are adsorbed by soil components such as clay, and most of the radioactive materials remain within a few centimeters of the topsoil.

On the other hand, in the decontamination work, a method of removing top soil at a certain depth is generally adopted. This is because it takes a lot of time and labor to identify a hot spot and remove the soil of only that part. Also, in the removal work of the soil surface layer, it is technically very difficult to remove evenly from the top soil at a depth of several centimeters, and in reality it is removed deeply. For this reason, the radioactive substance in the contaminated soil collected in this way is not uniformly distributed, but is unevenly distributed to some extent.
[Soil decontamination method]
As described above, contaminated soil and the like are different from radioactive waste, and there are various reuse and disposal methods depending on the radioactivity concentration. On the other hand, various methods have been proposed as soil decontamination methods.

  Soil decontamination methods are roughly divided into dry treatment and wet treatment. Dry treatment is to separate the clay component adsorbing radioactive material. Specifically, since the clay component has a fine particle size, it is classified by filtering the fine particle size soil component after drying and pulverizing the soil. The method to do is common. The dry treatment has a merit that it is relatively simple and generates a small amount of secondary waste, but the decontamination coefficient corresponding to the reduction rate of radioactivity tends to be small.

  On the other hand, the wet treatment is a system in which soil is mixed with water and fine clay components having a particle diameter transferred to the liquid phase as a suspended substance are separated as a suspension together with the supernatant water. Although the effect of reducing radioactivity is large, there are disadvantages such as the fact that secondary waste such as waste water is generated, and the treatment is complicated. For this reason, it is reasonable to use these soil decontamination methods properly according to the required radioactivity reduction effect.

  Also, there is a decontamination method called heat separation in the dry process. In this method, a special additive is added to the soil and heated to vaporize and separate the Cs component. In this method, since the radioactive substance moves to the exhaust gas side, it is necessary to remove the radioactive substance from the exhaust gas, and there is a disadvantage that the processing system becomes complicated. However, the radioactive substance removal efficiency is high, and it is necessary to select and use the conditions to be used.

  In addition, wet processing includes a method in which contaminated soil to be treated is treated in an acidic aqueous solution, and Cs adsorbed on the soil is separated from the soil and transferred to a liquid phase to remove radioactive substances from the soil. This method has high decontamination performance, but has the disadvantage that the processing equipment is more complicated and the processing cost is expensive, and it is necessary to carefully determine the conditions of the object to be applied.

  On the other hand, soil radioactivity concentration measurement is required. Since the optimal treatment method (reuse, decontamination, attenuation, etc.) differs depending on the radioactivity concentration, it is necessary to measure and sort out the radioactivity concentration of the soil. Moreover, in order to confirm the decontamination effect, it is necessary to measure the radioactive concentration of the soil.

  As described above, since the radioactivity distribution in the contaminated soil is not uniform and unevenly distributed, the measurement of the radioactivity concentration is necessary for classification based on the radioactivity concentration of the soil. It is important to combine these methods to form an optimum processing system.

  As described above, there are various methods for decontamination, and it is possible to improve the efficiency of decontamination by performing decontamination according to the radioactive concentration, and to reduce the cost of decontamination and the present invention. As a result of the study by the inventors, the following examples were obtained.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is an overall process flow diagram of contaminated soil and the like according to Embodiment 1 of the present invention.

  The final treatment methods for contaminated soil are `` Reuse in general fields (reuse) '', `` Disposal to industrial waste disposal site (industrial waste disposal) '', `` Disposal to contaminated soil final disposal site (final disposal) '' There are three. The cost of these three treatment methods is said to be in the order of reuse <industrial waste disposal <final disposal. For this reason, it is preferable that more soil can be reused, but when the radioactivity concentration is high, treatment (decontamination, attenuation) that lowers the radioactivity concentration is necessary many times, and optimization of the total cost is important. is there. Here, it is necessary to reflect the opinions of local residents, and optimization that takes these into consideration is required.

  The disposal site for final disposal will be new construction and will be expensive because sufficient barrier performance is required. On the other hand, there is a limit to the capacity of industrial waste disposal and existing disposal sites, and a new construction will require considerable costs and labor (including measures for local residents).

  In FIG. 1, the contaminated soil and the like are sorted at a radioactive concentration of 3,000 Bq / kg in step 101 to sort reusable soil. Next, in step 102, the soil is sorted at a radioactivity concentration of 8,000 Bq / kg to sort out soil that can be disposed of industrially. In addition, it is also possible to carry out the measurement of the radioactive concentration in these two steps at a time. The contaminated soil and the like separated by the radioactive concentration measurement and separation in steps 101 and 102 are respectively subjected to “reuse in general fields” or “disposal to industrial waste disposal sites”.

  In the process at step 103, a process for reducing the radioactivity concentration is performed. Treatment methods are broadly divided into decontamination (wet, dry, etc.) and attenuation (storage). In step 104, contaminated soil or the like that has been subjected to these treatments is separated. Next, in step 105, those that can be disposed of are separated.

  It is reasonable to apply the processing methods applied in step 103 in order from the lowest cost method. In general, methods with high radiation removal efficiency are expensive, so it is necessary to determine the order of treatment methods to be applied in consideration of these points. From this point of view, the next method after applying the `` dry method '' It is reasonable to apply the “wet method” to

  When the processing of step 103, step 104, step 105, step 103, and step 106 is repeated, and it is determined that even if the processing in step 103 does not provide a sufficient effect, it is not economically viable. Provided to the “final disposal site”.

  As a method for measuring the radioactivity concentration, a general method is to spread the soil to be measured on a conveyor or the like and measure the radioactivity from the surface of the soil while moving the conveyor. However, even if the radioactivity is measured from the outer surface of the container in a container such as a flexible container pack, the measurement accuracy is inferior, but it can be applied to a certain degree of separation, and can be applied to the coarse classification in the previous stage. It is.

  FIG. 2 is a flow chart in the case where rough sorting is performed and divided into a low-dose processing line and a high-dose processing line in the former stage of FIG.

  In FIG. 2, when the radioactivity concentration difference is large, if soil with a very high radioactivity concentration is mixed with soil with a low radioactivity concentration, contamination that is pulled toward the higher radioactivity concentration of the lower soil is generated. Occur. For this reason, in step 107, the contaminated soil packed in the flexible container pack or the like is roughly separated into a low dose and a high dose by a method such as measurement of the external surface dose rate before unpacking and processed in each dedicated line. It is reasonable to avoid contamination.

  In particular, by performing rough separation by surface dose rate measurement before unpacking, the rough separation apparatus and workers do not touch the high-dose contaminated soil, and contamination and radiation exposure can be avoided. When processing high-dose soil, additional equipment such as shielding and measures to increase decontamination efficiency are provided to improve the accessibility of workers (radioactivity measurement equipment, decontamination equipment, handling / transfer). Device, storage device, etc.). By separating the high-dose and low-dose soil processing lines, there is an advantage that the range of these measures and the number of target devices can be limited. In addition, by separating the high-dose and low-dose soil processing lines in this way, it is possible to make the specifications optimal for each line, such as the shielding structure, the presence or absence of shielding, and the processing method, and optimization of the entire processing equipment ( Economy, work efficiency, processing performance, etc.).

  The soil whose radioactive concentration is high in the coarse classification in step 107 and needs to be processed by the high-dose facility is subjected to the measurement of the radioactive concentration in steps 103a to 105a again, and the economic evaluation is performed again in step 106a.

  Steps 101 to 106 have been described with reference to FIG.

  FIG. 3 is a process flow diagram in which a determination step is provided after separation at each step according to the radioactivity concentration.

  In FIG. 3, reuse is the greatest merit in the final reuse / disposal method. On the other hand, decontamination of contaminated soil that is determined to be unsuitable for reuse in “Step 101” and that can be disposed at the industrial waste disposal site at “Step 102” at a lower cost than that disposed at the industrial waste disposal site. If it can be applied to “reuse in general fields”, it is more reasonable to do so.

  The present embodiment is an example in which such a determination is made in “Step 108”. This is based on the cost of the coping method and the processing cost (decontamination, attenuation, etc.) until it is classified when selecting the final coping method (reuse, industrial waste disposal site, final disposal site). This is because it is necessary to judge.

  Based on the radioactivity concentration distribution (Fig. 4) of the contaminated soil, the amount of contaminated soil, etc., classified into each countermeasure is examined.

Contaminated soil of 8,000 Bq / kg or less can be disposed of at a general work waste disposal site (industrial waste disposal site), and contaminated soil of 3,000 Bq / kg or less is subject to certain conditions (such as soil cover thickness conditions). Consider the case where reuse is possible. Further, the basic flow of processing is considered based on FIG.
[Treatment of contaminated soil of 3000 Bq / kg or less]
FIG. 4 is a graph showing a radioactivity concentration distribution estimation of contaminated soil.

  In FIG. 4, first, contaminated soil or the like is classified into those having a radioactive concentration of 3,000 Bq / kg or less and those having a radioactive concentration higher than that by measuring the radioactive concentration. Those below 3,000 Bq / kg can be reused.

  In “Step 102”, contaminated soil or the like of 8,000 Bq / kg or less is separated. This contaminated soil can be disposed of at an industrial waste disposal site.

  “Step 103” is a process for determining how to reduce the contaminated soil of 8,000 Bq / kg or less to 8,000 Bq / kg or less.

  Fig. 4 is a radioactivity concentration distribution map of contaminated soil estimated based on the air dose rate in the current Fukushima area. The main nuclides are Cs-137 and Cs-134, and the half-life is 2 years. As described above, a significant attenuation of radioactivity cannot be expected in a short time.

  The median of the distribution is 10000 Bq / kg, and the distribution is broader on the side where the radioactivity concentration is higher. This is because there is an area with a high dose although the area is limited. FIG. 5 shows the proportions of 3000 Bq / kg or less and 8000 Bq / kg or less estimated at the present time.

  FIG. 5 is a graph of radioactivity distribution estimation of contaminated soil showing the proportion of 8000 Bq / kg or less.

  In FIG. 5, even the contaminated soil of 3000 to 8000 Bq / kg alone reaches nearly 30%. Disposing all of this amount to an industrial waste disposal site is not a capacity-intensive and practical response, and it is required to reduce the radioactivity concentration to 3,000 Bq / kg or less, which can be reused as much as possible.

  FIG. 6 is a graph showing a range when decontamination (DF = 2) treatment with a decontamination coefficient 2 is performed on contaminated soil or the like.

  FIG. 7 is a graph showing the range of soil when the soil is contaminated for 5 years.

  In FIG. 6 and FIG. 7, in “Step 103”, “˜3,000 Bq / when the decontamination factor 2 is decontaminated (DF = 2) or the decay for 5 years is performed on the contaminated soil or the like. It shows the soil range of “kg” and “3,000 to 8,000 Bq / kg”. In any case, the radioactivity concentration of the contaminated soil or the like is reduced to about half, so the boundary value is about 6,000 Bq / kg or less and 16,000 Bq / kg or less at the current radioactivity concentration.

  As a result, the scope of reusable or industrial waste disposal sites is greatly expanded, with "~ 3,000 Bq / kg" accounting for about 20% of the total, "3,000-8,000 Bq / kg" "Will increase to about 20% of the total. In particular, the ratio of “˜3,000 Bq / kg” is greatly increased from about 0.5% to about 20%, which is four times the original, and the effect is great. In addition, a total of more than 40% of contaminated soil can be reused or simply disposed of, and nearly half of the contaminated soil can be treated.

  FIG. 8 is a graph showing a case where the decontamination (DF = 2) treatment was performed and the sample was further attenuated for 5 years.

  FIG. 8 shows a case where the decontamination (DF = 2) treatment is performed and further attenuated for 5 years. In this case, since the radioactivity concentration is reduced to about 1/4 due to the combined effect, the boundary value is about 12,000 Bq / kg or less and 32,000 Bq / kg or less at the present radioactivity concentration.

  After these treatments, “approx. 3000 Bq / kg or less” is approximately 40%, and “3000 to 8000 Bq / kg or less” is approximately 20%, and the corresponding ratio is further expanded. In particular, the reusable object that becomes “˜3000 Bq / kg or less” contains the median value of the distribution map, and therefore is further greatly enlarged.

  FIG. 9 is a graph showing the results of the radioactivity concentration when decontamination (DF = 2) was performed and further attenuated for 30 years.

  In FIG. 9, in this case, the radioactivity is reduced to about 1/8 of the original. In particular, since the target range of “˜3000 Bq / kg or less” greatly exceeds the median of the contaminated soil generation distribution, about 60% of the total can be reused, a considerable amount of contaminated soil can be reused, It can be seen that the effect is very large. In addition, “3000 to 8000 Bq / kg or less” decreases to about 10%. From this, it can be seen that reducing the radioactivity of DF = 8 or more greatly increases the proportion of contaminated soil of 3,000 Bq / kg or less, and is very effective. Considering that the processing cost naturally increases in order to increase the decontamination coefficient DF, the graph of FIG. 9 has an inflection point in the vicinity of 3 to 40,000 Bq / kg. It turns out that the effect is very large.

  In the above example, the processing cost for reducing the radioactivity is not considered, but if the radioactivity concentration is increased, that is, the processing cost is increased to obtain a large DF, as described above. DF = 8 to 10 is considered as one division range.

  It is considered reasonable that the radioactivity concentration targeted for the high-dose processing line in FIG. 2 of the entire processing flow is 3 to 40,000 Bq / kg or more. In terms of operation, it is also reasonable in terms of cost effectiveness to roughly separate the contaminated soil of 3 to 40,000 Bq / kg, which is the target of the low-dose treatment line, to treat the soil.

Next, we examine the case where the contribution to the air dose rate is divided into values of 1 mSv / year or less for the condition of radioactivity concentration in contaminated soil. The annual exposure dose of 1 mSv / Y is calculated based on the following assumptions.
・ Spent 8 hours outdoors and spend 16 hours indoors.
・ The indoor air dose rate is 40% outdoors.
・ The air dose rate for naturally occurring radionuclides is 0.04 mSv / Y.

  From the above conditions, the air dose rate of 1 mSv / year is 0.23 μSv / hr.

(0.23 μSv / hr-0.04 μSv / hr) × (8 hr + 16 h × 0.4) × 365 days ÷ 1000 mSv / μSv = 1 mSv / Y
At this 0.23 μSv / hr, the soil radioactivity concentration is about 1,300 Bq / kg.

  As a result, contaminated soil of 1,300 Bq / kg or less can be reused, and twice this contaminated soil of 2,600 Bq / kg or less can be easily disposed of at an industrial waste disposal site. consider.

  First, the contaminated soil is classified into those having a radioactivity concentration of 1,300 Bq / kg or less and those having a radioactivity concentration higher than that by measuring the radioactivity concentration. Those below 1,300 Bq / kg can be reused. In the next “Step 102”, contaminated soil of 2,600 Bq / kg or less is separated, and this contaminated soil can be easily disposed of in an industrial waste disposal site. “Step 103” is a treatment process of how to reduce the radioactive concentration of contaminated soil of 2,600 Bq / kg or more.

  FIG. 10 is a graph showing the range of soil of 1,300 Bq / kg or less and soil of 2,600 Bq / kg or more.

  As shown in the graph of FIG. 10, at this stage, those with 1,300 Bq / kg or less are about 1% of the whole, and those with 2,600 Bq / kg or more are about 5%, which is very small as a whole. It is a ratio. In addition, when measuring values with low radioactivity concentration in this way, it is possible to mix the high and low radioactivity concentrations by separating them roughly according to the surface dose rate etc. at the previous stage. (Contamination) can be avoided, contaminated soil that clearly exceeds the reference value can be excluded from the measurement target, and radioactivity concentration measurement and separation work can be performed rationally.

  FIG. 11 is a graph showing the soil range of ˜1,300 Bq / kg.

  FIG. 12 is a graph showing the soil range of 1,300-2,600 Bq / kg.

  In FIGS. 11 and 12, in this figure, in “Step 103”, when the decontamination treatment of decontamination factor 2 or attenuation for 5 years (corresponding to decontamination factor 2) is performed on the contaminated soil, etc. The soil range of "1,300 Bq / kg" and "1,300-2,600 Bq / kg" was shown.

  In either case, the radioactivity concentration of the contaminated soil, etc. is reduced by half, so each boundary value is the current radioactivity concentration "~ 2,600 Bq / kg", "2,600-5,200 Bq / kg" ”, And the ratios are about 5% and about 10% of the total, and a total of about 15% is subject to reuse or simple disposal. However, the rate is still small and further decontamination is required.

  FIG. 13 is a graph when the decontamination (DF = 2) treatment is carried out and further attenuated for 5 years.

  In FIG. 13, when the decontamination (DF = 2) treatment is carried out and further attenuated for 5 years, the total DF = 4 and the radioactivity concentration is reduced to 1/4. Any method is not limited to this.

  By such treatment, the boundary value becomes “˜5,200 Bq / kg” and “5,200 to 10,400 Bq / kg” at the current radioactivity concentration, and the respective ratios are about 15%, less than about 20%. In total, about 35% is subject to reuse or simple disposal. However, the target area does not yet fully contain the median of the distribution map, and it can be seen that further decontamination is effective.

  FIG. 14 is a graph in the case where the decontamination (DF = 2) treatment is carried out and further attenuated for 30 years.

  In FIG. 14, when decontamination (DF = 2) treatment is performed and further attenuated for 30 years, the total DF = 8 and the radioactivity concentration is reduced to 1/8. Any method is not limited to this. By such treatment, the boundary value becomes “10,400 Bq / kg” and “10,400-20,800 Bq / kg” at the current radioactivity concentration, and the respective ratios are about 35% and less than about 20%. In total, about 55% is subject to reuse or simple disposal. In this case, the target range sufficiently includes the median value of the distribution map, and the reusable ratio is 1/3 or more of the whole, and it can be seen that the effect of the treatment is large.

  In the above explanation, examples of decontamination and storage attenuation have been shown to reduce the radioactive concentration of contaminated soil. However, the method of reducing the radioactivity is not limited to these combination examples, and if the radioactive concentration can be reduced. Only decontamination or storage decay may be used.

  Even if the boundary value conditions are 3,000 Bq / kg and 8,000 Bq / kg, respectively, and the above-mentioned example where the boundary value conditions are low and severe, the treatment of DF = 8 Since 70% or less than about 60% of contaminated soil and the like have been subjected to reuse or simple disposal, it can be seen that the effect of decontamination treatment is up to about DF = -10.

  That is, it is reasonable to apply a treatment (decontamination method) that is more expensive but has a greater decontamination effect to the remaining contaminated soil having a high radioactivity concentration of about 30 to 40%. It is reasonable to apply the decontamination treatment from a low-level (small DF value) method. This is because contaminated soil with low radioactivity concentration is expensive and does not require treatment with a large decontamination effect. Therefore, the radioactivity concentration of contaminated soil, etc. is measured and sorted to make it suitable for the contaminated soil. It is preferable to perform treatment (decontamination etc.).

  As described above, according to the present invention, it is possible to rationally manage, treat and dispose of soil and vegetation outside the nuclear power plant due to an accident at the nuclear power plant. The cost required for dyeing can be greatly reduced.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

101 ... Separation of radioactivity concentration,
102 ... fractionation of radioactivity concentration,
103 ... treatment (decontamination / attenuation),
104: Sorting whether or not to reuse,
105: Sorting whether to dispose of industrial waste,
106 ... Economic evaluation,
107 ... coarse separation of contaminated soil,
108 ... Economic evaluation,
109 ... Economic evaluation.

Claims (5)

In a method for treating radioactively contaminated soil outside a radiation control area such as a nuclear power plant,
Separating the radioactively contaminated soil for each contamination level;
A process or disposal for reducing the radioactive concentration according to the classified contamination level;
A method for treating radioactively contaminated soil, comprising: In the processing method of the radioactive contamination soil of Claim 1,
The radioactively contaminated soil is applied in order from the lowest decontamination performance, and the radioactively contaminated soil is treated. In the processing method of the radioactive contamination soil of Claim 1,
A method for treating radioactively contaminated soil, wherein the radioactively contaminated soil is divided into two or more categories according to the radioactive concentration, and then subjected to treatment or disposal / reuse for reducing the radioactive concentration. In the processing method of the radioactive contamination soil of Claim 3,
A method for treating radioactively contaminated soil, characterized in that when determining whether to apply the radioactively contaminated soil, the disposal cost and the capacity of the disposal site are taken into consideration. In the processing method of the radioactive contamination soil in any one of Claim 1 and 3,
A method for treating radioactively contaminated soil, wherein the treatment method for reducing the radioactive concentration of the radioactively contaminated soil is decontamination or attenuation.

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