JP4259340B2 - Construction method of compressed bentonite materials in radioactive waste disposal tunnels - Google Patents

Description

  The present invention relates to a compressed bentonite so that the performance of the compressed bentonite material installed as a buffer material around the radioactive waste can be maintained for a long time in a radioactive waste disposal tunnel for burying radioactive waste in the ground and disposing it. It is related with the construction method of the compression bentonite material which installs material.

  Depending on the level of radioactivity, the radioactive waste is hardened with cement or the like and sealed in a container such as a drum can, or sealed in a container made of carbon steel or the like as a vitrified material mixed with glass. In the state, it is buried inside the tunnel (disposal tunnel) constructed at a depth of about 10m to 1000m underground and disposed of. Specifically, waste with a relatively high radioactivity level is buried at a depth of about several hundred meters to 1,000 m, and relatively low waste is buried at a depth of about several tens of meters to 100 m.

  Filling material between reinforced concrete structures built in the tunnel and the waste and the waste is filled with fillers such as mortar to fix and stabilize the waste, and between the structure and the surrounding ground In order to suppress the ingress of groundwater and the movement of radioactive materials, a buffer material is installed as an artificial barrier.

Bentonite having low water permeability and a property of suppressing water permeation is used as the buffer material (see Patent Document 1 and Patent Document 2), but bentonite as the buffer material alone is used to further reduce water permeability. Or, it is compacted in a state of being mixed with sand and used in a compressed form, the back surface is in close contact with the ground, the surface is covered with concrete or the like, and is not in contact with the outside air (Patent Document 3, Patent Reference 4).
JP 2003-279689 A Japanese Patent Laid-Open No. 2003-255087 JP-A-9-304596 JP 2002-6089 A

  Compressed bentonite materials are placed in an environment that does not come into contact with outside air during use after the installation is completed, so it is considered that the deformation of the performance of compressed bentonite materials will be suppressed after the installation is completed. When it is placed on the floor, it causes drying shrinkage and water absorption swelling, and in all cases, cracks, deformation, deterioration of performance, such as strength reduction, occur, so the installation of the compressed bentonite material from the production to the final underground is completed There is a possibility that the performance will be changed during construction.

  This invention proposes the construction method which does not cause the deformation | transformation of a performance during construction from the said background.

  In claim 1, the bentonite material produced by compressing bentonite or a mixed material of bentonite and sand at high density is subject to fluctuations under the conditions of temperature and humidity in the underground disposal tunnel where it is installed. By providing moisture with a moisture content ratio set in a difficult range in advance, the compressed bentonite material is continuously installed in the circumferential direction of the disposal tunnel along the wall of the disposal tunnel so as to surround the waste, It avoids the exchange of moisture between the compressed bentonite material and the atmosphere, and suppresses the deformation of the performance of the compressed bentonite material during construction.

  In claim 3, after the installation is completed, the compressed bentonite material having an arbitrary water content ratio is continuously installed in the circumferential direction along the wall of the disposal mine so as to surround the waste. Abandoned compressed bentonite having an initial moisture content determined in advance from the relationship between the humidity at each temperature and the optimum moisture content within a range where the moisture content does not easily fluctuate under the temperature and humidity conditions in the disposal tunnel By covering with the material, the contact of the compressed bentonite material with the atmosphere is avoided, and the performance of the compressed bentonite material is prevented from changing during construction.

  In the case of claim 3, since the compressed bentonite material is discarded and covered with the compressed bentonite material, the initial moisture content of the compressed bentonite material is arbitrary. The moisture content of the compressed bentonite material is easy to compact during production (easy to compress), necessary strength during transportation and installation, ensuring heat conductivity to release the heat of waste after disposal tunnel closure, etc. Therefore, the “arbitrary water content ratio” of the compressed bentonite material is determined from these conditions.

  The compressed bentonite material according to claim 1 and the discarded compressed bentonite material according to claim 3 are preliminarily subjected to humidity at each temperature within a range in which the water content ratio hardly changes under the temperature and humidity conditions in the disposal tunnel in which the compressed bentonite material is actually installed. The initial moisture content is determined from the results of long-term exposure tests in a constant temperature and humidity environment, as will be described later. It is determined from the straight line of FIG. 9 showing the relationship between the humidity and the final water content ratio for each temperature, that is, using temperature as a parameter.

  The final moisture content is the size of the moisture content that converges as a result of exposure to a plurality of compressed bentonite materials with different initial moisture content after being exposed for a certain period of time in a constant temperature and humidity environment. It can be said that it is a value of the initial moisture content which does not change even if it is exposed for a long period of time in a constant temperature and constant humidity environment.

  Therefore, the compressed bentonite material in claim 1 and the discarded compressed bentonite material in claim 3 are prepared in advance so as to have this final moisture content as the initial moisture content, and the final moisture content is determined under the same conditions as the constant temperature and constant humidity. By placing the compressed bentonite material or discarded compressed bentonite material in the disposal tunnel below, there is no exchange of moisture between the compressed bentonite material or discarded compressed bentonite material and the atmosphere, so compressed bentonite material or discarded compressed bentonite material The deformation of the performance is suppressed. In the case of claim 3, since there is no exchange of moisture between the discarded compressed bentonite material and the atmosphere, there is no exchange of moisture between the compressed bentonite material covered with the atmosphere and the compressed bentonite material during construction. It is possible to suppress the deformation of the material performance.

  In claim 1, there is no moisture in and out of the compressed bentonite material whose initial moisture content is adjusted at the time of installation of the compressed bentonite material in the disposal mine, and in claim 3, the discarding whose initial moisture content is adjusted Since the contact surface of the compressed bentonite material with the atmosphere is covered with the compressed bentonite material, there is no moisture in and out of the discarded compressed bentonite material and the atmosphere when the discarded compressed bentonite material is installed. There is no fluctuation in the water content of the bentonite material.

For example, if the temperature in the disposal tunnel is 20 ° C and the humidity (absolute humidity) is about 8.6g / m ³ as plotted in Fig. 9, the vertical axis indicating the final moisture content is changed to the compressed bentonite material. If an initial moisture content of about 4.6% is given, fluctuations in the moisture content of the compressed bentonite material are less likely to occur. Similarly, if the temperature in the disposal tunnel is 20 ° C and the humidity (absolute humidity) is about 20.0 g / m ³ , the initial moisture content of the compressed bentonite material is about 11.6% from the vertical axis indicating the final moisture content. Give it.

  Since the final moisture content is considered to be almost proportional to the absolute humidity at a fixed temperature, the absolute humidity is plotted on the horizontal axis with the temperature as a parameter, and the final moisture content is plotted on the vertical axis. If the abscissa (absolute humidity amount) is known, the ordinate (final moisture content) can be obtained, and the optimum initial moisture content to be given to the compressed bentonite material can be determined from the temperature and humidity in the disposal tunnel.

  Conversely, if the ordinate (final moisture content) is determined, the abscissa (absolute humidity) can also be determined. Therefore, the optimum moisture content can be maintained from the initial moisture content given to the compressed bentonite material. The temperature and humidity in the disposal mine can be determined. In claims 2 and 4, air conditioning management is performed based on this relationship to maintain the temperature and humidity in the disposal tunnel within a certain range.

  In claim 2 and claim 4, during construction from the start of installation of compressed bentonite material and discarded compressed bentonite material to completion of installation, the initial moisture content at the time of production of compressed bentonite material is set to a temperature and humidity within the disposal tunnel. By maintaining the temperature and humidity within a certain range, the performance of the compressed bentonite material or the discarded compressed bentonite material is prevented from changing during construction.

  The temperature and humidity in the disposal tunnel are managed by controlling the temperature and humidity of the outside air taken from the ground using an air conditioner in the disposal tunnel.

  Since the initial moisture content of the compressed bentonite material is determined from the relationship between the temperature and humidity in the disposal tunnel and the final moisture content, the temperature and humidity in the disposal tunnel during the construction period determine the initial moisture content of the compressed bentonite material. By maintaining the temperature and humidity within a certain range, there is no change in the environment that causes fluctuations in the initial moisture content of the compressed bentonite material or the discarded compressed bentonite material during construction from the start of installation to the completion of installation. Therefore, it is avoided that the performance of the compressed bentonite material or the discarded compressed bentonite material changes during the construction.

  In claim 1, bentonite or a mixed material of bentonite and sand is manufactured to a high density, and the initial moisture content is set within a range that does not easily fluctuate under conditions of temperature and humidity in the underground disposal tunnel. Since the compressed bentonite material that has been given moisture is installed in the disposal tunnel, there is no exchange of moisture between the compressed bentonite material and the atmosphere, and the performance of the compressed bentonite material is prevented from changing during construction. can do.

  In claim 2, the temperature and humidity in the disposal tunnel are set so that the initial moisture content ratio at the time of production of the compressed bentonite material is determined during the construction from the start of installation of the compressed bentonite material to the completion of installation. In order to maintain a certain range, there is no change in the environment that causes a change in the initial moisture content of the compressed bentonite material during the construction from the start of installation to the completion of the installation, and the performance of the compressed bentonite material changes during construction. It can be avoided.

  In claim 3, immediately after installing the compressed bentonite material having an arbitrary water content, the contact surface of the compressed bentonite material with the atmosphere is within a range in which the water content ratio is less likely to change under the conditions of temperature and humidity in the disposal tunnel, Since it is covered with a discarded compressed bentonite material having an initial moisture content determined in advance from the relationship between the humidity at each temperature and the optimum moisture content, there is no exchange of moisture between the discarded compressed bentonite material and the atmosphere, which is covered by it. Further, there is no exchange of moisture between the compressed bentonite material and the atmosphere, and the performance of the compressed bentonite material can be prevented from changing during construction.

  In claim 4, during the construction from the start of installation of the discarded compressed bentonite material to the completion of installation in claim 3, the temperature in the disposal tunnel is determined so that the initial moisture content at the time of production of the discarded compressed bentonite material is determined. In order to maintain the humidity within a certain range, there is no change in the environment that causes a change in the initial moisture content of the compressed compressed bentonite material during the construction from the start of installation to the completion of the installation. As a result, there is no exchange of moisture between the compressed bentonite material covered with the atmosphere and the atmosphere, and it is possible to suppress or prevent the performance of the compressed bentonite material from changing.

[1] Derivation of the relationship between the humidity at each temperature and the optimum moisture content First, in order to derive the relationship between the humidity at each temperature and the optimum moisture content from Tables 1 to 15 and FIGS. From the bentonite with the specifications shown, we created specimens of multiple compressed bentonite materials with different initial moisture content under conditions of constant temperature and constant humidity, and for each of multiple specimen groups (groups) with different initial moisture contents, Explain the results of exposure tests under different temperature and humidity conditions.

[2] Specimen preparation method The test specimen was bentonite powder and sand (silica sand No. 3 + No. 5) in a mass ratio of 7 to 3 (bentonite: sand = 7: 3), and water was added to adjust the initial moisture content. After adjustment, the density was set to 1.6Mg / m ³ using an Amsler. A VP tube mold (φ = 100 mm, H = 100 mm) was used as the compaction container, and the specimen dimensions after compaction were such that the diameter was φ = 100 mm and the height was H = 50 mm.

[3] Experimental cases Table 2 shows a list of experimental cases.

  The experiment was performed using the exposure conditions (temperature, humidity) and restraint conditions of the specimen and the initial moisture content of the specimen as parameters.

  The temperature is set in two ways: 40 ° C, which is a relatively high temperature, and 20 ° C, which is a room temperature. Humidity is 95% and 80%, which are humid conditions, and approximately 50%, which is equivalent to the natural atmosphere (constant at 20 ° C, without humidity control). Were set in three ways. The initial moisture content of the specimen was set to 3%, 7% corresponding to the natural moisture content, 21% with relatively high saturation (saturation Sr = 82.2%), and 14% in between.

When setting the water content, the optimum water content (ω _opt ) 10.4% (20MPa: 2000 report “Technical reliability of high-level radioactive waste in geological disposal in Japan”) Cycle Development Organization) and the optimum water content ratio (ω _opt ) in dynamic compaction 17.0% (1Ec: 2000 report (supra)).

  As for the restraint condition of the specimen, since it is assumed that the cushioning material is left in a state where the side and bottom are restrained when the execution work is assumed, the bentonite is expected to absorb water easily. An experiment was conducted in which the side and bottom of the specimen were restrained under the conditions of a temperature of 40 ° C. and a humidity of 95% for two types of initial water content ratios of 7% and 14%.

  In Table 2, groups No. 1 to 3 were left unconstrained in an environment with a temperature of 40 ° C. and humidity 80%, and Nos. 4 to 6 were left unconstrained in an environment with a temperature of 40 ° C. and humidity 95%. Groups No. 7 and 8 are groups left unconstrained in an environment with a temperature of 40 ° C and 95% humidity, and Nos. 9 to 11 are groups left unconstrained in an environment with a temperature of 20 ° C and humidity of 48%. is there.

[4] In each experimental case (No. 1 to 11) under the conditions shown in Measurement Table 2, the specimen is left for a period of 0.5 to 3 months as shown below, and the expansion, contraction, cracking, etc. In order to grasp the change, the measurement shown in Table 3 was performed. In the height direction of the specimen, as shown in FIG. 1, the specimen is sliced every 1 cm in height, and the moisture content distribution is measured. In the radial direction, the height direction is as shown in FIG. The water content distribution was measured at three locations in the center portion of each of the center portion, the outer periphery portion, and the intermediate portion in the radial direction.

  The moisture content is measured at the time when 0.5 days, 1 day, 3 days, 1 week, 2 weeks, 1 month, 2 months, 3 months have passed for each case of No. 1 to 11 after leaving the specimen. However, the measurement requires dismantling the specimen and collecting the sample, and the specimen that has been subjected to the moisture content measurement cannot subsequently be used for measurement of height, diameter, mass, etc. Specimens were prepared for the measurement days (0.5 days, 1 day, 3 days, 1 week, 2 weeks, 1 month, 2 months, 3 months later). Table 4 shows the specimen preparation and the measurement intervals.

[5] Specimen creation status Table 5 shows the specimen creation status for each of the specimen sets 1 to 8 in Table 5 to Table 12, and the height, diameter, and mass of the specimen set 8 measured up to 3 months later. Table 13 shows the changes. Specimen set 8 is a set in which the moisture content distribution was measured from 0.5 days to 3 months after the specimen was created.

[6] Experimental Results FIGS. 3 to 5 show the changes over time in the specimen mass, diameter, and height for each of No. 1 to No. 11 cases. Here, only changes over time of specimen sets 6 (measured for one month), 7 (measured for two months), and 8 (measured for three months) over a long measurement period are shown. 3 shows the results of cases No. 1, 4, 7, and 9 with an initial moisture content of 7%, and FIG. 4 shows the results of cases No. 2, 5, 8, and 10 with an initial moisture content of 14%. Shows the results of cases Nos. 3, 6, and 11 with an initial moisture content of 21%.

  Fig. 6 and Table 14 show the time-dependent changes in the moisture content distribution in the vertical direction (the height direction of the specimen) for all cases No. 1 to 11, and Fig. 7 and Table 15 show the horizontal direction for all cases No. 1 to 11 ( The time-dependent changes in the moisture content distribution in the radial direction of the specimen are shown.

[7] Summary
(1) Changes in mass, height, and diameter over time
1) From Table 13 and Figs. 3 to 5, the initial moisture content is 7%, the temperature is 40 ° C, the humidity is 80%, and the temperature is 40 ° C, the humidity is 95% (No. 1, 4, 7). It was confirmed that the specimen absorbed and swelled, and the mass increased. However, even under the same initial moisture content, the specimen dried and contracted and the mass decreased under the environment of temperature 20 ° C. and humidity about 50% (No. 9).

  2) In the other cases (No. 2, 3, 5, 6, 8, 10, 11), it was confirmed that the mass of the specimen was decreasing and that the specimen moved to the dry / shrink side.

  3) Mass increase due to water absorption / swelling is greatest when the initial moisture content is 7%, temperature is 40 ° C, and humidity is 95% (No. 4). The amount of change in mass, diameter, and height is 28.3 g (4.2% ), 0.38 cm (3.8%), and 0.38 cm (7.5%). Figures in parentheses indicate the rate of change relative to the initial value.

  4) Mass loss due to drying / shrinkage is greatest when the initial moisture content is 21%, temperature is 20 ° C, and humidity is about 50% (No. 11). The amount of change in mass, diameter, and height is -108.6g ( -14.2%), -0.17 cm (-1.7%), and -0.12 cm (-2.4%).

(2) Change in moisture content distribution over time
1) The increase in the average water content due to water absorption / swelling is greatest when the initial water content is 7%, the temperature is 40 ° C, and the humidity is 95% (No. 4), and the change in the water content is 3.8% (Table 13). ).

  2) The decrease in the average moisture content due to drying / shrinkage is greatest when the initial moisture content is 21%, the temperature is 20 ° C, and the humidity (about 50%) (No. 11). The change in the average moisture content is -16.3%. (Table 13).

  3) As the moisture content distribution in the vertical direction changed with time, the water absorption and drying started to change from the upper surface of the specimen in contact with the atmosphere, and gradually tended to affect the lower part (Table 14, Fig. 6). .

  4) From the time-dependent change in the moisture content distribution in the horizontal direction, changes in water absorption and drying started from the surface of the specimen in contact with the atmosphere, and there was a tendency to gradually affect the center (Table 15, Fig. 7). ).

(3) About the crack situation
1) In the case of No. 1, 4 and 7 where water absorption / swelling occurred, the degree of cracking varies depending on the moisture content of the specimen and the atmospheric conditions, but the severe moisture initial moisture content is 7%, temperature is 40 ° C, and humidity is 95%. In the case of (No. 4), the most cracking occurred. Cracks occurred in the shape of a turtle shell on the entire surface of the specimen, and in the corners on the top surface, they occurred in a circular shape so that the corners were peeled off. In the case of water absorption / swelling, it was confirmed that the water content ratio inside the specimen also increased. Therefore, it is expected that the strength will decrease to some extent even within the specimen where cracks have not occurred.

  2) In Nos. 2, 3, 5, 6, 9 to 11 where drying / shrinkage occurred, cracks occurred mainly in the shape of a turtle shell on the surface of the specimen. The degree of cracking varies depending on the moisture content of the specimen and the atmospheric conditions. However, cracks penetrating the specimen were also observed at No. 11 with a severe initial moisture content of 21%, temperature of 20 ℃, and humidity (about 50%). It was. It was observed that the through crack had a large crack width at the bottom of the specimen. The surface of the specimen that is in contact with the atmosphere is dried and contracted, and this phenomenon gradually reaches the inside of the specimen (FIG. 8).

  3) In each atmospheric condition, specimens where cracking was not noticeable were also confirmed. No.1 under conditions of 40 ℃ and humidity 80% (initial moisture content 7%), No.5 under conditions of temperature 40 ℃ and humidity 95% (initial moisture content 14%), temperature 20 ℃, humidity approx. This corresponds to the case of No. 9 (initial water content ratio 7%) under the condition of 50%. In these cases, the amount of change in water content is small compared to other cases under the same conditions (Table 14).

(4) Influence of restraint
1) At a temperature of 40 ° C and a humidity of 95%, both No. 4 with an initial moisture content of 7% and No. 7 with a constraint are on the water-absorbing / swelling side. There was no significant difference in changes. However, with regard to cracking, it was observed that cracking was suppressed in No. 7 with restraint (mass change was No. 4: 28.3 g, No. 7: 28.7 g, and the change in average moisture content was No. 7. 4: 3.8%, No. 7: 3.7%) (Table 13).

  2) At a temperature of 40 ° C and a humidity of 95%, both No. 5 with no initial restraint of 14% moisture content and No. 8 with restraint moved to the dry / shrink side. Changes in specimen mass and average water content were slightly small (mass change was No. 5: -14.2 g, No. 8: -9.5 g, change in average water content was No. 5: -3.5%, No 0.8: -2.8%), but there seems to be no significant difference (Table 13).

[8] Relationship between humidity at each temperature and final moisture content (initial moisture content) From the above (4), it can be considered that there is no significant difference in the final moisture content between restrained and unconstrained. Cases No. 1 to 3 (temperature 40 ° C., humidity 80%), No. 4 to 6 (temperature 40 ° C., humidity 95%), No. 9 to 11 (temperature 20 ° C., humidity 48%) From the average value of the water content ratio at the time, the relationship between the humidity and the final water content for each temperature (20 ° C., 40 ° C.) shown in FIG. 9 was determined.

From Table 14, the average final moisture content at a temperature of 20 ° C and a humidity of 48% is 4.6%, and the humidity (relative humidity) of 48% is approximately 8.6 g / m ³ when converted to absolute humidity. Since it is considered proportional, if it is assumed that the relationship between the absolute humidity and the water content ratio at the temperature of 20 ° C. shown in FIG.

Similarly, when the temperature is 40 ° C and the humidity is 80%, the average final moisture content is 9.3%. When the temperature is 40 ° C and the humidity is 95%, the average final moisture content is 10.8%, and the humidity (relative humidity) is 80% and the humidity (relative humidity). ) respectively 95% of the absolute humidity of about 40.8 g / m ^3, because it is 48.0 g / m ^3, the straight line representing the relationship between the absolute humidity and the water content ratio in the case of the temperature 40 ° C. as shown in FIG. 9 is drawn. These straight lines show the optimum water content ratio with respect to the absolute humidity at each temperature in the installation environment of the compressed bentonite material.

From the graph shown in FIG. 9, for example, when the temperature in the underground disposal tunnel is 20 ° C. and the humidity (absolute humidity) is about 8.6 g / m ³ , an initial moisture content of 4.6% is given to the compressed bentonite material. If this is the case, it can be said that the moisture content of the compressed bentonite material is unlikely to vary, so that it is possible to suppress the performance of the compressed bentonite material from changing at least during the construction period.

Compressed bentonite material when the initial moisture content of 4.6% is given to the compressed bentonite material, but the temperature in the underground disposal tunnel is other than 20 ° C and the humidity (absolute humidity) is other than about 8.6 g / m ³ By controlling the temperature and humidity in the disposal tunnel so that the temperature in the disposal tunnel is 20 ° C and the humidity (absolute humidity) is about 8.6 g / m ³ from the start of installation to the completion of installation ( (2) The performance of the compressed bentonite material can be prevented from changing during the construction period.

Compressed bentonite is also used when the temperature in the underground disposal tunnel is other than 20 ° C and the humidity (absolute humidity) is other than about 8.6 g / m ³ while giving the initial moisture content of 4.6% to the compressed bentonite material. Immediately after installing the material, the compression contact of the compressed bentonite material with the atmosphere has a moisture content ratio that is determined by the temperature and humidity conditions in the disposal tunnel and does not cause a change in the moisture content of the compressed bentonite material. By covering with the bentonite material (Claim 3), it is possible to avoid the deformation of the performance of the compressed bentonite material during the construction period.

[9] Construction procedure of compressed bentonite materials Figures 10- (a) to (e) are waste disposal tunnels for burying radioactive waste in the ground and disposing of it as described above. 1) An example of a construction procedure of a compressed bentonite material in which moisture having an initial water content ratio determined in a range in which fluctuation is not likely to occur under conditions of temperature and humidity in 1 is given in advance. A mine tunnel (disposal mine) 1 is a disposal mine for placing a waste body 4 enclosing waste, and is distinguished from a main mine 1A connecting a blower side shaft 8 and a disposal mine 1 shown in FIG. Is done. FIG. 10 shows the case where low-level radioactive waste is targeted.

  Since the compressed bentonite material is installed so as to surround the waste body 4, the compressed bentonite material is manufactured in a form divided into parts in the mine shaft 1, for example, the bottom, the side, and the upper part.

  After the construction of the mine 1 by excavation and lining, prior to the installation of the compressed bentonite material, the bottom and sides of the mine 1 are filled with a backfill material 5 such as backfill soil or concrete.

  After filling the bottom and side backfill materials 5, a bottom compressed bentonite material 61 is installed on the bottom backfill material 5 (a), and the side backfill material 5 is placed on the bottom compressed bentonite material 61. Side compressed bentonite material 62 is installed along the inner circumference (c). In parallel with the installation of the side compression bentonite material 62, a concrete pit 2 is constructed by placing concrete or precast concrete on the bottom compression bentonite material 61 and inside the side compression bentonite material 62 (b, c).

  After the construction of the concrete pit 2 (c), the waste body 4 is placed inside the filler 3 while filling the filler 4 with a cement-based material such as mortar that fixes and stabilizes the waste body 4 inside the concrete pit 2. (D). After the installation of the waste body 4 is completed and the upper part is covered with the filler 3, the upper compressed bentonite material 63 is installed thereon (d). The upper compressed bentonite material 63 is installed so as to straddle the side compressed bentonite materials 62 and 62 on both sides in the width direction of the tunnel 1.

  After the upper compressed bentonite material 63 is installed (d), the backfill material 5 such as backfill soil or concrete is filled thereon, and the installation work of the compressed bentonite material is completed (e).

  FIG. 11 shows a construction procedure of the compressed bentonite material when the compressed bentonite materials 61 to 63 are installed while controlling the air conditioning (temperature and humidity) in the tunnel 1 (Claim 2). The installation procedure of the compressed bentonite materials 61 to 63 is the same as that shown in FIG. The management of air conditioning is continuously performed from the start of installation of the compressed bentonite materials 61 to 63 to the completion of the installation.

  Outside air on the ground is sent to the inside of the tunnel 1 through the ventilation side shaft 8 that communicates the ground with the tunnel 1 or the ventilation duct 9 that is arranged in the ventilation side shaft 8, and the air conditioning that is arranged in the tunnel 1 in the tunnel 1 It is supplied through the duct 10 and discharged from the tunnel 1 to the ground through the exhaust side shaft 11 or the exhaust duct 12.

  On the ground on the ventilation side shaft 8 side, outside air is introduced into the ventilation duct 9 from the outside air introduction device 13 installed on the ground portion of the ventilation side shaft 8. The temperature of the outside air, or the temperature and humidity are once adjusted by an air conditioner 14 connected to the outside air introducing device 13, and the air whose temperature is adjusted or temperature and humidity is adjusted is blown to the tunnel 1 through the ventilation side shaft 8 or the ventilation duct 9. The

  Since the temperature and humidity of the blown air are assumed to rise or fall due to the ground temperature while passing through the ventilation side shaft 8 and the ventilation duct 9, the temperature of the air whose temperature and humidity have changed at the entrance of the tunnel 1. And the humidity are adjusted again by the air conditioner 15 installed at the lower end position of the blower side shaft 8 or the blower duct 9, and the temperature and humidity adjusted air is supplied into the tunnel 1 from the outlet 10 a of the air conditioning duct 10. . When the humidity is adjusted at the entrance of the tunnel 1 at the lower end of the blower side shaft 8 as shown in FIGS. 11 and 12, the humidity adjustment on the ground is not necessarily required.

For example, outside air with a temperature of 9 ° C and relative humidity of 100% RH (absolute humidity 8.818 g / m ³ ) in tunnel 1 is 20 ° C and relative humidity 50% RH (absolute humidity 8.642 g / m ³ ). When the air is to be adjusted and supplied, the outside air introduced into the air duct 9 from the outside air introduction device 13 rises to about 15 ° C. due to the ground temperature before reaching the tunnel 1, and the relative humidity is 60% RH. Since the air conditioner 15 at the lower end of the air duct 9 is considered to decrease to about (absolute humidity amount 7.694 g / m ³ ), the temperature of the blown air is increased by about 5 ° C., and the absolute humidity is slightly increased. Air conditioning should be performed.

FIG. 12 shows an example of a method for air conditioning management in more detail than FIG.
On the ground, outside air is taken in by the outside air introduction device 13, and the temperature of the outside air is adjusted by a temperature controller 16 (corresponding to the air conditioner 14 in FIG. 11) including a heater and a cooling cooler, and the temperature is adjusted from the ground fan 18. The air thus blown is blown to the entrance of the mineway 1 through the blower side shaft 8 or the blower duct 9. When the air is blown, the temperature of the blown air is monitored by the temperature sensor 17 connected to the temperature controller 16, and the temperature is managed so as to be maintained within a certain range. The air is fed back to the temperature controller 16 if it falls outside a certain range.

  The air temperature to be adjusted by the temperature controller 16 is predicted from the outside air temperature and the ground temperature in the ventilation side shaft 8 until reaching the tunnel 1, and then the air conditioner at the entrance of the tunnel 1 in FIG. Equivalent to 15 and set up in the tunnel 1 so that efficient temperature and humidity adjustment can be performed by the temperature controller 20 equipped with a heater and cooling cooler and a humidity controller 21 equipped with a humidifier and dehumidifier Is done.

  If the temperature of the air to be supplied into the tunnel 1 can be accurately adjusted with the temperature controller 16 on the ground in view of changes due to the ground temperature, the temperature controller 20 in the tunnel 1 does not necessarily have to be installed. .

  However, as shown in FIG. 13, a plurality of mine shafts 1 are constructed on one blast side shaft 8, and the blast side shaft 8 and each mine channel 1 are connected by a main mine channel 1A. When the distances to the entrances of the mine shafts 1 are different, there is a difference in the degree of temperature change from the blower side shaft 8 to the entrance of the mine shafts 1. It is appropriate that 20 is installed.

  As described above, the temperature and humidity of the air blown to the entrance of the tunnel 1 are assumed to change due to the supply and release of heat due to the ground temperature while passing through the ventilation side shaft 8 or the ventilation duct 9. Prior to the final temperature / humidity adjustment by the temperature controller 20 and the humidity controller 21, the temperature / humidity of the air sent to the tunnel 1 is measured by the temperature / humidity sensor 19 installed in front of them.

  The air that passed through the temperature / humidity sensor 19 was connected to the temperature and humidity to be supplied into the tunnel 1 based on the measurement result of the temperature / humidity sensor 19 with the temperature controller 20 and the humidity controller 21 adjusted. The air is sent from the blower 22 to the air conditioning duct 10 and supplied into the tunnel 1 from the outlet 10a connected to each place.

  The temperature and humidity of the air supplied into the tunnel 1 are monitored by a temperature / humidity sensor 23 installed around the installation site of the compressed bentonite material in the tunnel 1, and the air is adjusted during the installation period of the compressed bentonite material. The air is sent again from the blower 22 to the air conditioning duct 10 via either or both of the air conditioner 20 and the humidity controller 21. When the temperature controller 20 in the tunnel 1 is not installed, the data measured by the temperature / humidity sensor 23 is fed back to the temperature controller 16 on the ground, and the temperature of the air to be adjusted by the temperature controller 16 based on the data Is set.

  Air supplied into the tunnel 1 from the outlet 10a is discharged to the ground through the exhaust side shaft 11 or the exhaust duct 12 by the exhaust device 24 installed near the exit of the tunnel 1.

  When the temperature of the air supplied into the mine shaft 1 is changed by the ground temperature in the same manner as when passing through the ventilation side shaft 8 or the ventilation duct 9, and it is assumed that the change affects the compressed bentonite material. In some cases, it is necessary to install an exhaust duct 25 in the tunnel 1 and forcibly discharge the air supplied into the tunnel 1 from the outlet 10a.

  FIG. 14 shows the same compression bentonite materials 61 to 63 as shown in FIG. 10, abandoned compression in which moisture having an initial water content ratio determined in a range in which fluctuations are unlikely to occur under conditions of temperature and humidity in the tunnel 1 is given in advance. The construction procedure of the compressed bentonite material in the case of covering the compressed bentonite material with the bentonite material 7 (Claim 3) is shown.

  In this case, as in the case of FIG. 10, after the construction of the mine 1 and the filling of the backfill material 5 to the bottom and sides of the mineway 1, the bottom compressed bentonite material 61 is installed on the bottom backfill material 5, Immediately after that, the surface (upper surface) of the bottom compression bentonite material 61 is discarded and covered with the compression bentonite material 7 (a), and the side compression bentonite material 61 is formed on the bottom compression bentonite material 61 along the inner periphery of the side backfilling material 5. The material 62 is installed (b), and immediately thereafter, the surface (side surface) of the side compressed bentonite material 62 is discarded and covered with the compressed bentonite material 7 (b, c).

  On the other hand, a concrete pit 2 is constructed on the bottom compressed bentonite material 61 and on the inner side of the side compressed bentonite material 62 (b, c), and further, the waste material 4 while filling the concrete pit 2 with a filler 3 such as mortar. (C, d), and the upper part of the waste body 4 is filled with the filler 3 and the upper compressed bentonite material 63 is installed thereon, and immediately after that, the surface (upper surface) of the upper compressed bentonite material 63 is discarded. The installation work of the compressed bentonite material is performed in the manner of covering (d) with the compressed bentonite material 7 and then filling the backfill material 5 such as backfill soil or concrete.

  FIG. 15 shows the inside of the tunnel 1 after the installation of the compressed bentonite materials 61 to 63 is completed. (a) is a longitudinal sectional view of the mine shaft 1 and (b) is a transverse sectional view.

  The invention of claim 4 is the same as the method of the invention of claim 3 shown in FIG. 14 and the method of the invention of claim 2 shown in FIG. 11 and FIG. ), The compressed bentonite materials 61 to 63 and the discarded compressed bentonite material 7 are installed.

It is the perspective view of the test body which showed the measurement location of the moisture content distribution of a height direction. It is a top view of the specimen which showed the measurement location of the moisture content distribution of radial direction. It is the graph which showed the change of the mass, diameter, and height at the time of 1-3 months progress of the specimen with an initial moisture content of 7%. It is the graph which showed the change of the mass, diameter, and height at the time of 1-3 months progress of the specimen with an initial moisture content of 14%. It is the graph which showed the change of the mass, diameter, and height at the time of 1-3 months progress of the specimen with an initial moisture content of 21%. It is the graph which showed the time-dependent change of the moisture content distribution of the perpendicular direction of all the test bodies. It is the graph which showed the time-dependent change of the moisture content distribution of the horizontal direction of all the test bodies. It is the elevation which showed the crack generation situation of the specimen. It is the graph which showed the relationship between the moisture content in the air under 20 degreeC and 40 degreeC, and a final moisture content. (a)-(e) is sectional drawing of the mine shaft which showed the construction procedure of the method of Claim 1. FIG. It is the conceptual diagram which showed the air-conditioning management method by the method of Claim 2. FIG. 12 is a conceptual diagram showing a method for air conditioning management in more detail than FIG. It is the bird's-eye view which showed the relationship between the ventilation side shaft and a disposal tunnel when a plurality of disposal shafts connect to one ventilation side shaft. (a)-(e) is sectional drawing of the mine shaft which showed the construction procedure of the method of Claim 3. FIG. (a) is a longitudinal sectional view showing the inside of a mine shaft where the installation of the compressed bentonite material is completed, and (b) is a transverse sectional view.

Explanation of symbols

1 ... Disposal tunnel, 1A ... Main tunnel, 2 ... Concrete pit, 3 ... Filler, 4 ... Waste body, 5 ... Backfill material,
61 …… Bottom compression bentonite material, 62 …… Side compression bentonite material, 63 …… Top compression bentonite material, 7 …… Discarded compression bentonite material,
8 ... Blower side shaft, 9 ... Blower duct, 10 ... Air conditioning duct, 10a ... Air outlet, 11 ... Exhaust side shaft, 12 ... Exhaust duct, 13 ... Outside air introduction device, 14 ... ... air conditioner (ground), 15 ... air conditioner (in the tunnel),
16 …… Temperature controller, 17 …… Temperature sensor, 18 …… Ground blower, 19 …… Temperature and humidity sensor, 20 …… Temperature controller, 21 …… Humidity regulator, 22 …… Blower, 23 …… Temperature and humidity Sensor, 24 …… Exhaust device, 25 …… Exhaust duct.

Claims (4)

Compressed bentonite material made by compressing bentonite or a mixture of bentonite and sand with high density is used around radioactive waste that is buried and disposed of in the ground. The temperature in the disposal tunnel is obtained by using the relationship between the humidity and the final moisture content at each temperature when exposed for a certain period of time in a constant temperature and constant humidity environment. The final moisture content under the conditions of humidity and humidity is obtained, and the compressed bentonite material produced with this final moisture content as the initial moisture content is continuously circumferentially along the wall of the disposal tunnel so as to surround the radioactive waste. Of compressed bentonite material in a radioactive waste disposal mine installed in an industrial environment.   2. During the construction from the start of installation of compressed bentonite material to the completion of installation, the temperature and humidity in the disposal tunnel are maintained within a certain range so that the initial moisture content at the time of production of the compressed bentonite material becomes the determined temperature and humidity. Construction method of compressed bentonite material in the radioactive waste disposal mine described. Compressed bentonite material made by compressing bentonite or a mixture of bentonite and sand with high density is used around radioactive waste that is buried and disposed of in the ground. A compressed bentonite material having an arbitrary water content ratio after installation is installed along the wall of the disposal tunnel so as to surround the radioactive waste, and continuously installed in the circumferential direction immediately after that, Dispose of the contact surface of compressed bentonite with the atmosphere using the relationship between the humidity at each temperature and the final moisture content when the exposure surface is exposed for a certain period of time in a constant temperature and humidity environment. seeking final moisture ratio under conditions of temperature and humidity in the tunnel, the compression vent in radioactive waste disposal tunnel covering that the final water content in the initial water content ratio discarded compacted bentonite material was made as Construction method of the thread material.   Request to maintain the temperature and humidity in the disposal tunnel within a certain range so that the initial moisture content at the time of production of the discarded compressed bentonite material will be the temperature and humidity during the construction from the start of installation of the discarded compressed bentonite material to the completion of the installation The construction method of the compression bentonite material in the radioactive waste disposal tunnel of claim | item 3.

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