DE102020007175A1 - Arrangement and procedure for the construction of an overactive developed repository for intermediate and high-level radioactive waste - Google Patents

Abstract

The arrangement and the procedure for creating an above-ground, developed repository for intermediate and high-level radioactive waste is new in its entirety. Even in the current legislation on disposal (site selection law, StandAG of 05/05/2017) an alternative possibility of disposal is not mentioned. This repository is characterized by the fact that the safety requirements specified in Section 26 of the Law can be implemented.

Description

Arrangement and procedure for the construction of a repository for intermediate and high-level radioactive waste that is developed above ground.

The hollow concrete sphere (7), d _A = 116 m, in combination with the paraboloid dome (34) is extremely stable due to its shape. A loading earth pressure of 450 m can be removed. The hollow concrete sphere (7) and the paraboloid dome (34) are made of heat-conducting material.

The decay heat from the stored nuclear waste will continue to increase in the first two hundred years. Four LiBr absorption chillers are installed in the building in alternating operation for controlled, even regulation of the temperature. This waste heat can diffuse to the surface via cooling lines (14a) in the concrete shell (8) and further via a paraboloid dome (34) via backfill material from the lignite mines.

In layers close to the surface of the former lignite opencast mines (1a), outside the former glacier fields of the Pleistocene period, these can be used as excavations (2) for the above-ground construction of repository structures. A multi-barrier system can protect the biosphere from exposure to medium-level and high-level radioactive waste. 5. The building with 17 floors and a storage area of 22,000 m ² is designed in such a way that the nuclear waste from a nuclear power plant can be accommodated.

Description:

Construction of an above-ground repository that protects the biosphere from the radiation exposure of medium- and high-level radioactive waste by means of a multi-barrier system. It is characterized in that the heat production rate of the waste from the structure and the structure backfill can diffuse to the surface.

So far, the fuel elements have been transported in containment containers, but have been transported unprotected to the former salt mines (Asse II mine or Morsleben mine) with the well-known problems.

You are breaking new ground in the former ore mine near Salzgitter, "Schacht Konrad". A "repository" for medium-level radioactive waste with negligible heat generation is being developed in deep geological layers.

The existing excavation chambers of the ore mine in the storage fields are filled with waste packages and then the remaining cavities are concreted with salt concrete.

The requirements for an underground repository are anchored in the Site Selection Act (StandAG) of 2017.

The high requirements with regard to the choice of location for the repository in the deep geological layers for the realization of the desired multi-barrier system are difficult to implement because very few host rocks have a homogeneous structure.

The task was to plan a repository for medium and high-level radioactive waste that would ensure sufficient safety over time.

The hollow concrete sphere (7) in combination with a concrete paraboloid dome (34) is statically extremely stable due to its shape. The loading earth pressure of 450 m can be removed.

This building would even survive an external force.

The decay heat from the stored nuclear waste will continue to increase in the first two hundred years. Four LiBr absorption chillers (16) with alternating operation are installed for the controlled, even regulation of the temperature in the hollow concrete sphere (7). The waste heat is released via cooling lines (14a) in the concrete wall (8),

The paraboloid dome (34) is made of thermally conductive material that acts as a heat dome.

In order to meet these high requirements, a structure had to be designed that would protect the biosphere from the radiation exposure of medium- and high-level radioactive waste by means of a multi-barrier system.

The repository must be technically equipped in such a way that the radioactive waste can be retrieved without the direct deployment of personnel. This must also be ensured for future generations.

The basic requirement for this type of storage is monitoring for at least two hundred years, including maintenance of its technical equipment.

In the former lignite open-pit mines (1a), above-ground structures of the repository can be erected. With a depth (1b) of at least 340 m and a cover layer (1c) of 300 m above the crest of the hollow concrete sphere (7), the requirements of the Site Selection Act are met.

Collecting lines (3a) and pumps (3b) are arranged in the excavation pits (2) in addition to the existing opencast mines in order to pump the surface and layer water during the construction period.

A 40 m thick reinforced concrete slab (4a) is produced on the foundation level (4). A spherical cap (5) made of lean concrete is concreted onto this reinforced concrete slab (4a).

A layer of a bentonite-aluminum mixture (6) with a thickness of 0.2 m is applied to the negative mold of the spherical cap (5).

The hollow concrete sphere (7) and the paraboloid dome (34) are produced on this reinforced concrete slab (4a).

The hollow concrete sphere (7) is produced in spherical form with an inner diameter of 100 m, an 8 m thick reinforced concrete wall (8) and an inner and outer 44 mm thick steel shell (8a) from welded structural steel segment plates. These steel plates also form the lost formwork.

A paraboloid dome (34) with a reinforced concrete wall (34a) on a base of 40 m and a dome roof (34b) of 120 m thickness is to be arranged over the hollow concrete sphere (7).

The reinforced concrete wall (8) of the cavity sphere (7) and the wall of the paraboloid dome (34a) are made of mass concrete with a retarder to prevent shrinkage cracks. In contrast to normal concrete, the concrete does not contain any aggregates made from natural stones, but from a mixture of the "large grain", 80 mm of cast iron vermicular graphite balls (8b) (GJV, Compat Graphite Iron, GGI) according to DIN EN 16079 and the "smallest balls" 45 mm made of aluminum balls (8c) (material: AISiMgMn, EN AW-6082). The balls are fractionated according to size and volume (large grain > 67%, smallest grain 20% and cement paste with a water-cement factor of 0.4) in the basic building material concrete of strength class C20/25, with ISORETAD retarder from CEMEX, installed to form a closed to achieve globular packing.

The floor slabs (9) made of reinforced concrete divide the spherical cavity (7) into 17 storeys, and they also stiffen the cavity sphere (7). This creates a storage area of 22,000 m ² .

The walls (10) made of reinforced concrete are arranged in a honeycomb pattern and divide and stabilize the hollow sphere (7).

With the arrangement of the reinforced concrete ceilings (9), a cooling basin H (11a) (hot) is created in the center of the basement. This is used for the underwater storage of 12 HAW glass canisters (12a) with a graphite shielding mold (24).

The waste heat from the 12 glass molds (12a) is used to heat the absorption chillers (16).

In the outer area of the basement there is a decay tank C (11b) (cold) for the underwater storage of 232 HAW glass canisters (12a) with graphite shielding molds. This area is cooled by the absorption chillers (16).

The storage openings and sealing covers (9b) are arranged in the reinforced concrete ceiling (9a) above the basement.

The 1st floor is the distribution level, on which the HAW glass molds (12a) are brought into the cooling basin.

Floors 2 to 16 are intended for the storage of 30,000 glass canisters (12b) MAW of the medium-level radioactive waste with negligible heat generation.

The machine and the controls for the freight elevator are housed on the 17th floor.

The cooling lines (14a) made of ceramic sheet (AvM 1415N from W.E.C. Pritzkow) serve to dissipate the heat of hydration after the reinforced concrete wall (8) has been concreted. After the high-level radioactive waste (12a) and (12b) has been stored, the cooling lines (14a) are used indirectly to dissipate the process heat.

The air conditioning of the ventilation system (17) and the cooling of the cooling basin (11b) are used by 4 standard LiBr absorption chillers (16) with the substance pair water-lithium bromide (H2O/LiBr), with water being the refrigerant and lithium bromide being the solvent. Systems from York International GmbH, type YIA/4C1, or equivalent are used.

Part of the process heat from the cooling basin (11a) is removed in the evaporator and expeller for heating and separating the working fluid in the 2-stage AKM (16).

The system circuit of the 2-stage compact AKM (16) provides an external water circuit in order to be able to dissipate the heat from the absorber and condenser components. By means of a heat exchanger in the aforementioned components and a connection to the cooling water lines (14a) in the reinforced concrete wall (8), a water circuit is established with feed pumps from one AKM to the opposite AKM. The circulation flow in the cooling water pipes (14a) conducts the heat over the reinforced concrete wall (8) to (from the inside out) the steel shell (8b), a layer of bentonite material (6), backfill material of bauxite sedimentary rock (33), concrete paraboloid dome (34), and overburden/backfill material (36) from the former opencast mines (33) conducts the heat to the earth's surface.

"Fresh air ducts" (18) are placed vertically on the inside of the concrete wall (8). Outlet openings on all floors distribute the air over the corridors (19). The used air is returned to the ventilation systems (17) via the shaft (20) of the freight elevator (21).

For transport and storage of the MAW glass molds (12b) with the graphite shielding moldings (24), 8 pieces are stacked per steel container (23).

The containers (23) are distributed and stored on the floors with computer-controlled floor conveyors via a freight elevator (21) located in the core of the hollow concrete sphere (7).

With the dense storage of the cast iron vermicular graphite balls (8b) and the aluminum balls (8c), the particularly high thermal conductivity of the ball material is transferred to the construction of the hollow ball (7) and the paraboloid dome (34).

The heat conduction in the concrete wall (8) and the paraboloid dome (34a) is essentially based on the selection of the aggregates of cast iron vermicular graphite balls (8b) with a thermal conductivity of 50 W/mK and the aluminum "miniature ball" (8c) with a thermal conductivity of 150 W/mK. The thermal diffusivity in the mathematical version is > k = k/ (pcp) > m ² /s. The heat transfer through the walls is determined by the mixture of cast iron and aluminum balls. With 8.7 layers/m (large grain 8 cm, partial coverage > smallest grain 4.5 cm), this results in a theoretical value of 6.341 * 10^-5 m ² /s per layer).

According to statements by Prof. Dr. Gerhard Jentzsch, Jena, the decay heat from the stored nuclear waste will still increase in 200 years. (Prof. Jentzsch is one of the thirty scientists working in the Rah men of the selection process for repository sites (AKEnd) 2002 dealt with the assumed heat input from the repository and made the statements). But ultimately the decay heat depends on the composition of the radioactive fuel rods used. The elements with a short half-life radiate a greater amount of heat. In order to be able to make an assessment, rough calculations were carried out according to the US scientists El-Wakil or Glastone.

Using the example of the Brokdorf nuclear power plant with a final thermal output of 3,900 MW/h, the decay heat after an interim storage period of 25 years amounts to a quantity of heat
S = 1,585 W/s; 5.71 MW/h.

This thermal output must be given off to the surface. This is possible with the concept. The paraboloid dome (34a) fulfills the function of a heat dome.

El-Wakil published the following formula in 1971, the ratio of decay heat to thermal reactor power (operating time since

start of operations, T; time after reactor shutdown, t; according to the ANS standard 1968, American Nuclear Society). $$\text{P}\left(\text{t}\right)\ast \text{P0}=0.095\text{t}-0.26\left[1-\left(1+\text{t/d}\right)-0.2\right]$$

$$3.600\text{MWH/3600 s}=\mathrm{1,083}\text{MW/s//1}\text{.083}\text{.000 W/s}$$

$$\begin{array}{l}\text{P0}\ast \text{P}\left(\text{t}\right)>\mathrm{0,095}*\mathrm{7,88}*10\text{8}]-\mathrm{0,26}*[1-\left(1+\mathrm{1,135}*10\text{9/7}\text{,88*108}\right)-\\ \mathrm{0,2}]=1083000*10-3=1.585\text{W//s //5}\text{,706MW/h}\end{array}$$

Using the example of the Brokdorf nuclear power plant, 1986-2022 / 36 years of operation // 25 years of post-cooling time $$\text{T > 36 years}=1.135\ast 10\text{9s; t=7}\text{,88}\ast \text{108s}$$

$$\mathrm{3,600}\text{MWH/3600s}=\mathrm{1,083}\text{MW/s//1}\text{.083}\text{,000W/s}$$

$$\begin{array}{l}\text{P0}\ast \text{P}\left(\text{t}\right)>0.095*7.88*10\text{8th}]-0.26*[1-\left(1+1.135*10\text{9/7}\text{.88*108}\right)-\\ 0.2]=1083000*10-3=\mathrm{1,585}\text{W//s //5}\text{.706MW/h}\end{array}$$

With the thermal diffusivity of 6.341 * 10^-5 m ² /s, the calculated amount of heat from the radioactive radiation of 1,585 W/s > 5.71 MW/h can be dissipated.

With a special arrangement of the reinforcement (13) made of special steel mats in the form of spherical segments and a braiding of spiral reinforcement cages (13a) with integrated cooling lines (14) in the concrete wall (8), a structurally high-strength structure (7) with a flexural reinforcement of ð = 437 MN/m ² created. The prerequisite for the use of the composite building material of cast iron vermicular graphite balls, the aluminum balls and the basic building material concrete is the same expansion of έc ∼ -2.4*10^3 mm.

The tensile strength of the concrete is further reinforced by vertically guided cladding tubes (13b) with tension wires (13c), which are tensioned after eight concreting sections (40 m) and injected with concrete adhesive of strength class C50/55 and extended for the next section. The tensioning wires (13c) can be tensioned in sections on an attachable mobile steel frame with hydraulic jacks (13d).

The access structure (25) consisting of a steel gate (26) and reinforced concrete gate (27) is on the 7th floor.

In front of the entrance structure (28), an access shaft (29) to the near-surface entrance structure (30) and control building (31) is created, which secures the access shaft (29).

After completion of the storage work, the entrance structure (25) is sealed airtight.

The control lines (32), which are routed into the control building (31), enable the repository to be monitored over a period of five hundred years.

After a review period, the entire excavation pit is dismantled and backfilled. The access shaft (29) is retained for inspection work. Only after about 500 years and the decay of the decay heat, the walls, ceiling and running surface of the access shaft (29) are lined with 10 cm of bentonite-aluminium powder mixture (6) and then concreted with concrete according to the outer shell (8).

A layer of earth (36) of >300 m secures the near-surface entrance structure (30), control building (31) and the access shaft (29).

In the control building (31) 2 diesel emergency generators (38) and fuel storage tanks (39) are installed for the self-sufficient supply of all technical equipment.

• Übersicht
• Schnitt
• Grundriss 7. Obergeschoss
• Grundriss Untergeschoss
• Detail Bewehrungskorb
• Detail Bewehrung der Betonhohlkugel

The invention is presented:

• overview
• cut
• Floor plan 7th floor
• Ground floor plan
• Reinforcement cage detail
• Detail of the reinforcement of the hollow concrete sphere

The advantages resulting from the repository concept are:

With a depth of at least 340 m and a top layer of 300 m above the top of the hollow concrete sphere (7), the most important requirement of the Site Selection Act (StandAG) of 2017 is met. Above-ground exploration is not necessary when choosing a location, as the geological conditions are known.

The safety requirements for the disposal of heat-generating radioactive waste in accordance with the Site Selection Act (StandAG) of May 5, 2017 (Federal Law Gazette I S1074) can be met accordingly.

The large surface of the building and the special composition of the building construction enable a high level of radiation protection and, on the other hand, an effective heat diffusion of the stored intermediate and high-level radioactive waste.

With a technical structure of this type, the knowledge and experience and the quality of the materials can be consistently implemented in accordance with the EN and DIN regulations and their use to form a safe multi-barrier system.

The safety strategies usual in nuclear power plants with the multi-stage principle, redundancy, diversity and fail-safe can be implemented with this disposal concept.

The energy concept is designed in such a way that part of the process heat from the highly radioactive waste in the inner area of the spent fuel pool is used to heat the LiBr absorption chillers. In the outer area of the spent fuel tank, the temperature is reduced by cooling lines.

The ventilation systems limit the room temperature from the 1st to the 17th floor. This reduces the outgassing of the medium-level radioactive waste.

1a

1a lignite opencast mines

1b

1b Teufe (depth of the pit)

1c

1c top layer

2

2 excavation

3a

3a manifolds

3b

3b pumps

4

4 foundation level

4a

4a reinforced concrete slab

5

5 spherical cap

6

6 bentonite material

7

7 hollow concrete sphere

8th

8 concrete wall

8a

8a steel shell

8b

8b cast iron vermicular graphite spheres

8c

8c aluminum balls

9

9 floors

9a

9a floor above basement

9b

9b Storage opening and sealing cover 9b

10

10 reinforced concrete walls

11a

11a cooling pool (hot)

11b

11b cooling pool (cold)

12a

12a glass molds HAW

12b

12b glass molds MAW

13

13 reinforcement steel mesh

13a

13a Reinforcement cage

13b

13b cladding tubes

13c

13c tension wires

13d

13d steel frame with hydraulic jacks

14a

14a cooling lines (external)

14b

14b cooling lines d. ventilation systems

14c

14c cooling lines d. cooling pond

15

15 carbon fiber

16

16 LiBr absorption chillers

17

17 ventilation systems

18

18 "fresh air ducts"

19

19 corridors

20

20 shaft (inside)

21

21 freight elevator (inside)

22

22 Not applicable

23

23 containers

24

24 shielding moldings

25

25 access structure

26

26 steel gate

27

27 concrete gate

28

28 entrance building

29

29 access shaft

30

30 Near-surface entrance structure

31

31 control buildings

32

32 control lines

33

33 Bauxite sedimentary rock

34

34 paraboloid dome

34a

34a wall of the paraboloid dome

34b

34b dome roof

35

35 Not applicable

36

36 earth cover layer

Claims (10)

The arrangement and the procedure for creating an above-ground, developed repository for intermediate and high-level radioactive waste is new in its entirety. Even in the current legislation on disposal (site selection law, StandAG of 05/05/2017) an alternative possibility of disposal is not mentioned. This repository is characterized by the fact that the safety requirements specified in Section 26 of the Law can be implemented. Construction of a repository created above ground, consisting of a multi-barrier system: 2.1 reinforced concrete wall (8), 8 m thick, cavity of a sphere (7) with an inner diameter of 100 m 2.2 steel shell (8a), 44 mm thick, the inside and outside of the Reinforced concrete wall (8) fully assembled and continuously welded 2.3 Paraboloid dome made of concrete (34) with aggregate cast iron vermicular graphite balls (8b) (GJV, Compact Graphite Iron, CGI) and aluminum balls (8c) (material: AISiMgMn, EN AW-6082). At the base 40 m and in the apex area of the cupola roof (34b) 55 m thick 2.4 Between the reinforced concrete sphere and the paraboloid cupola, the filling is made of a plastically deformable material, the bauxite sedimentary rock (33) 2.5 The filling and covering over the apex of the hollow concrete sphere (7 ) secures the minimum thickness of 300 m according to the Site Selection Act. The earth cover layer (36) of the excavation pit in the former lignite mining area is used as overburden material for backfilling and covering. 2.6 The repository is after claim 2 . characterized in that the maximum safety requirements of Section 26 Paragraph 3.1 are met by the design of the different materials, Section 2.1 to Section 2.5. The repository is in claim 1 .1 and 1.3 characterized in that it consists of two combined structures that have proven to be particularly stable due to their geometric shape. The decay heat of the stored nuclear waste is released through cooling lines in the concrete wall (8) 1.1, via bauxite sedimentary rock (33) and in the second step to the wall of the paraboloid dome (34a). This is characterized in that it consists of concrete with aggregate cast iron vermicular graphite balls (8b) and aluminum balls (8c) (material: AISiMgMn, EN AW-6082). The different "large" to "small fraction" in the material composition results in a dense pebble bed packing that has a high thermal conductivity. Which can transport a heat quantity of S = 1,585 W/s to the surface. The concrete hollow ball (7) is characterized in that 17 storeys can be created by dividing the interior space with reinforced concrete ceilings, which have a storage area of 22,000 m ² . This creates the possibility of absorbing the nuclear waste from a switched-off nuclear power plant from HAW and MWA containers. The reinforcement of the concrete shell (8) is characterized in that reinforcement cages (13a) are installed diagonally as in a wickerwork. The reinforcing steel mats (13) of the reinforcement are characterized in that they are preformed in segments. The additional reinforcement of the paraboloid dome (34) is characterized in that it consists of vertical cladding tubes (13b) and prestressed ø 14 mm steel wires (13c). The cooling lines (14a) in the reinforced concrete wall (8) are characterized in that they dissipate the hydration heat during the construction of the structure and the process heat after the storage of the nuclear waste. The air conditioning technology in the cavity of the sphere is required for around 200 years until the decay heat has subsided. It is characterized by the fact that the process heat of the spent fuel tank can be used through the use of absorption chillers.

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