CA2016923A1 - Radioactive material storage structure - Google Patents
Radioactive material storage structureInfo
- Publication number
- CA2016923A1 CA2016923A1 CA 2016923 CA2016923A CA2016923A1 CA 2016923 A1 CA2016923 A1 CA 2016923A1 CA 2016923 CA2016923 CA 2016923 CA 2016923 A CA2016923 A CA 2016923A CA 2016923 A1 CA2016923 A1 CA 2016923A1
- Authority
- CA
- Canada
- Prior art keywords
- tank
- radioactive material
- liner
- liquid
- transfer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Landscapes
- Monitoring And Testing Of Nuclear Reactors (AREA)
Abstract
Abstract A structure is provided for the storage and containment of radioactive material immersed in liquid.
The structure comprises: a tank within which the material and liquid are accommodated; a tank platform supporting the bottom wall of the tank and having a plurality of galleries to provide access to the tank bottom for repair and inspection; a containment liner spaced from the tank;
radioactive shield means outward of the liner and above the upper open end of the tank for enveloping and isolating the material and liquid within a shielding envelope; transfer means for transferring material to and from the interior of the envelope; and handling means within the envelope. The structure is designed to eliminate any leakage of radioactive material or contaminated liquid and to allow for inspection and repair of the tank and liner.
The structure comprises: a tank within which the material and liquid are accommodated; a tank platform supporting the bottom wall of the tank and having a plurality of galleries to provide access to the tank bottom for repair and inspection; a containment liner spaced from the tank;
radioactive shield means outward of the liner and above the upper open end of the tank for enveloping and isolating the material and liquid within a shielding envelope; transfer means for transferring material to and from the interior of the envelope; and handling means within the envelope. The structure is designed to eliminate any leakage of radioactive material or contaminated liquid and to allow for inspection and repair of the tank and liner.
Description
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-- 1 -- .
This invention relates to structures for storing and containing radioactive material immersed in liquid.
Spent radioactive fuel must be stored for long periods of time within which the radioactivity of such waste decays.
In the operation of nuclear power plants, or other facilities using radioactive material, spent fuel and other radioactive waste are produced which require specialized storage to prevent irradiation and contamination during radioactive decay. A commonly preferred form of storage utilizes the shielding and heat dissipation properties of water in storing radioactive material in pools. The radioactive material may be safely handled below the surface of the water by personnel -wearing minimal protective equipment. The heat generated by the radioactive decay of the stored material is dissipated by the convection of the water. Heat is ;~
thereafter transferred to the ambient air above the pool or reduced by immersed heat transfer units. When decayed to a low level of radiation the radioactive material may be permanently disposed of.
Structures containing pools for storage of radioactive material have been constructed in general as part of a power station. Primary and secondary irradiated fuel storage bays in generating stations may have rectangular storage pools lined with panels of carbon steel welded together at their edges to form a water-tight barrier. The panels may comprise a carbon steel plate welded to a frame of steel channels which is embedded in the concrete walls forming the pool. The carbon steel ~ -liner plate may be coated with corrosion resistant paint.
Correct application and continued maintenance of such coatings is required to prevent liner deterioration. , Leakage of such storage pools is difficult to detect and repair since access is limited to the interior of the pool. Water may flow through a crack in the steel plate Z016~?~
pool liner into cracks in the concrete. Detecting and locating the source of leakage from the outer surface of the concrete wall is extremely difficult and costly. To repair the steel plate pool liner the radioactive material must be removed to allow human access involving costly handling which increases the risk of contamination.
Significant quantities of contaminated liquid may penetrate such steel liners, and concrete walls and percolate through the surrounding soil before leakage is 10 detected and repairs are undertaken. -~-Existing storage pools also suffer from the disadvantage that they are physically integrated into a power station facility. The storage period for spent fuel exceeds the power station's viable economic life since the 15 reactors deteriorate under radioactive conditions and must -~ ~-be either abandoned or completely rebuilt. The reactors ~ ~
and related generating equipment also become rapidly --obsolete due to technical advances during the storage period. For these reasons therefore it is disadvantageous to operate the storage facility together with the power generating facility. If it is desirable that a power facility be abandoned or destroyed it is inefficient to -~
maintain the facility merely as a storage facility. If a ~ ;~
power facility is to be reconstructed, the related 25 activity may jeopardize or obstruct the storage function. ;~
Due to the extensive storage period and `
concentration of harmful radioactive materials in such .
, . ~ ~: .
storage facilities the security and integrity of such facilities is critical. Events such as severe - - ~
30 earthquakes, airplane crashes, nuclear explosions, ~ ~-sabotage and aggression are considered as low probability -risks in general but due to their potantially catastrophic consequences such storage facilities must be designed to ` ;~
address these contingencies. Containment of radioactivity ;~
and maintenance of the structural integrity in ''''' "'' ' '" ' 2C)16~
catastrophic circumstances is difficult when the storage facility is structurally integrated into the power facility since vibrations, forces and structural damage may propagate from one part of the structure to another.
The present invention reduces or eliminates the -~
above disadvantages by providing a substantially structurally independent storage facility having a storage ~ ;
tank which is accessible for inspection and repair, within a containment liner to contain any leakage.
In accordance with the invention is provided a structure, for the storage and containment of radioactive -material immersed in liquid, comprising: a tank having side and bottom walls defining a storage area within which said radioactive material and immersing liquid are ~ ~-15 accommodated; a tank platform having an upper surface -supporting the bottom wall of said tank, said tank platform having a plurality of galleries providing access to said tank bottom wall for repair and inspection; a containment liner spaced from said tank and having side and bottom walls to contain said liquid upon rupture of or leakage from said tank, said liner side wall and tank side wall defining a peripheral space therebetween to provide access to said tank side walls for repair and inspection, said liner bottom wall supporting the lower surface of said tank platform; radioactive shield means, outward of said liner and above the upper open end of said tank, for enveloping and isolating said radioactive material and ~immersing liquid within a shielding envelope; transfer means, communicating between an external source of said radioactive material and said envelope, for transferring said radioactive material to and from the interior of said ~-~
envelope; and handling means, within the envelope of said radioactive shield means, for handling said radioactive material within said envelope.
)16~
In order that the invention may be readily understood, an embodiment of the invention will be described by way of example with reference to the accompanying drawings.
Figure 1 is a partially broken away perspective view of a structure in accordance with the invention having a storage facility towards the upper right, and an -associated power generating facility and transfer means toward the lower left of the drawing. ;
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Figure ~ is a sectional view along line 2-2 of Fig. 1.
Figure 3 is a partially broken away plan view along line 3-3 of Fig. 2.
Figures 4 and 5 illustrate an alternative ~;
storage structure roof in plan and elevation respectively wherein a cone shaped structural lattice is constructed (instead of a dome roof as in Figures 1, 2 and 3).
Figure 6 shows the transfer means and handling ~- ;
means in sectional elevation. ~ `
Figure 7 shows the handling means extended to - -~
the bottom of the tank and the inner end of the liquid filled transfer tunnel in sectional elevation.
Figure 8 is a sectional plan view through the transfer tunnel showing the transfer means.
Figure 9 is a perspective view of a stacking frame for stacking trays or modules of spent fuel bundles within the tank.
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In a preferred embodiment the storage structure of the present invention is constructed adjacent a nuclear power generating station. A storage structure may be constructed at an independent site but generally the transport of radioactive material outside containment areas is minimized to avoid contamination risks and reduce the costs involved.
As illustrated in Figure 1 a storage structure 1 may be constructed adjacent a nuclear power generating facility 2. Transfer means including an under water transfer tunnel 3 communicate between the storage structure 1 and the generating facility 2. Within the generating facility 2 radioactive material, such as spent fuel bundles, are stored under water in a conventional rectangular storage pool 4 for approximately six to ten years until radioactive decay has progressed to the stage ~
where long term storage is feasible. referring to Figure -2, radioactive material is transferred under water from the storage pool 4 to transfer means at the outer end of the transfer tunnel 3 using an overhead travelling crane within the generating facility 2. The radioactive material is then transferred through the transfer tunnel 3 under water to the interior of the storage structure 1 as will be described in detail below. Radioactive material originating from other power facilities or operations may be shipped by rail or truck to the loading dock area 5 for eventual storage in the storage structure 1. The material - ~
is shipped in sealed isolating casks which are lifted from ~ -the trucks or rail cars and placed in a transfer pool 6~by the overhead crane. The casks are then opened under water and the radioactive material removed. The radioactive ~
material may be temporarily stored within the transfer -pool 6 or may directly be placed upon the transfer means to be transferred to the interior of the storage structure 1. When the radioactive material has decayed and may be safely disposed of permanently, the above process is -~
2016~
reversed wherein radioactive material is transferred from the storage structure 1 to the transfer pool 6, is placed within shipping casks under water in the transfer pool 6 and is thereafter placed upon trucks or rail cars in the loading dock area 5 to be transported to a disposal site.
The detailed construction of the storage structure for the storage and containment of radioactive ~
material immersed in liquid is illustrated in Figure 2. A ;
tank 7 having a side and a bottom wall 8 and 9 provides within its interior a storage area for the radioactive material and immersing liquid. The tank 7 is preferably constructed of stainless steel plate such as ASTM A 240 Type 304 for superior corrosion resistance. Preferably the tank 7 is cylindrical since the tank 7 may then be ~ ~ ~
15 self supporting and may be constructed according to well ; -known methods. Any shape of tank 7 however may be used in ~ , accordance with the invention such as rectangular or square provided the side walls 7 are braced. The bottom wall 9 of the tank 7 is supported upon a tank platform 10 ~-which has a plurality of galleries 11 providing access to the tank bottom wall 9 for inspection and repair in the event of leakage. In the embodiment illustrated the tank ~-platform 10 comprises a series of parallel reinforced -;~
concrete walls capped by a reinforced concrete slab which supports the tank bottom wall 9. Inspection may be carried out using by personnel wearing suitable protective equipment, by remote control mechanisms or through the use of sound sensors. When leakage is detected repairs to the -~
tank bottom plate 9 may be carried out by injecting sealants or grout, or by removing a portion of the concrete slab, welding the tank bottom plate 9 overhead and thereafter repairing the concrete slab.
To contain contaminated water upon rupture of or -leakage from the tank 7 a containment liner 12 is spaced 35 outward from the tank 7. The containment liner 12 has a ~i;
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side wall 13 and a bottom wall 14, preferably forming a cylindrical welded steel containment tank within which the storage tank 7 is nested. The lower surface of the tank platform 10 is supported upon the liner bottom wall 14.
5 The liner side wall 13 and the tank side wall 8 define a peripheral space 15 between them providing access to the tank side wall 8 for inspection and repair. The containment liner 12 is a secondary containment system which is used only in the event of leakage from the 10 primary containment system namely the tank 7. The containment liner 12 therefore may be constructed of carbon steel possibly coated with a corrosion resistant coating in exposed areas. The galleries 11 of the tank platform 10 and the peripheral space 15 are outwardly 15 connected providing access also to the containment liner 12 for inspection and repair of the liner 12.
Heat generated by the radioactive decay of the stored material is first transferred to the water 16 in which the material is immersed within the tank 7. Due to 20 convection the water 16 is circulated and warmer water 16 accumulates towards the upper surface of the water 16.
Conventional heat transfer devices may be immersed within the tank 7 to cool the upper region of the water 16 ~
maintaining the temperature of the water 16. The -peripheral space 15, galleries 11 and air plenum 17 above the water surface communicate to provide air circulation around the tank 7. The air circulates to additionally 3 cool the water 16 within the tank 7. In the event of ~-failure of the heat transfer device the passive cooling of 30 this air circulation provides a further degree of safety against overheating of the decaying radioactive material.
The upper edge of the tank side wall 8 is located above the water surface and the upper edge of the liner side wall 13 extends above the upper edge of the ~, 35 tank side wall 8. A horizontal annular walkway 18 spans 6~
between the upper portions of the tank side wall 8 and the liner side wall enabling personnel access within the storage structure 1. Preferably the walkway 18 is constructed of open grating to enable air circulation as -described above. In the event of an earthquake, accidental dropping of material, or other catastrophic event, waves may breach the upper edge of the tank side wall 8. It is desirable to dampen such waves and prevent reverberations since the stored radioactive material and ' -~
10 components of the structure 1 may be subjected to dynamic ~ -wave forces causing damage. The water 16 breaching the -upper edge of the tank side walls flows through the open grating of the walkway 18 and is retained within the containment liner 12. The propagation and reflection of waves is thereby reduced and dampened. The water within the containment liner 12 may thereafter be pumped back into the tank 7.
: ~'`
In order to envelope and isolate the radioactive material and immersing liquid within a radioactive ~-~
shielding envelope, radioactive shield means are provided outward of the liner 12 and above the upper open end oP
the tank 7. In a preferred embodiment the radioactive ~ -shield means comprise: a concrete foundation slab 19 ~ `~
beneath the liner bottom wall 14; concrete side walls 20, 25 outward of the liner side wall 13, supported upon the -foundation slab 19 and having a transfer port 21 providing access to the transfer means; and a roof structure 22 having a concrete shielding layer 23 and supported upon the concrete side walls 20. The radiation shield means 30 also include gate means 24, as shown in Figure 6, adjacent - ;
the transfer port 21. The gate means 24 are for opening the transfer port 21 when radioactive material is - -transferred to and from the interior of the shielding envelope and for closing the transfer port 21 to maintain 35 the integrity of the shielding envelope. Preferably the -concrete of the radioactive shielding means is of high ~
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g density having aggregates of magnetite or specularite for their superior radioactive shielding properties.
'':, In the embodiment illustrated in the drawings -the tank 7, liner 12 and concrete side walls 20 are all cylindrical. The liner 12 is used as a form when the concrete side walls 20 are poured either through well known slip forming or block and filler techniques.
Two alternate roof structures 22 are illustrated. Referring to Figure 2 the roof structure may comprise a post-tensional reinforced concrete dome, the concrete of which forms a concrete shielding layer. A
concrete dome is exceptionally strong and capable of withstanding severe catastrophic events, but is relatively expensive to build. Referring to Figures 4 and 5 an 15 alternate composite roof structure 22 is illustrated which -is less expensive than a dome but is less capable of -withstanding severe loadings. The composite roof structure 22 is constructed of an inner cone-shaped -structural steel lattice of radial trusses 25. A
corrugated sheet steel roof deck is outwardly attached to the purlins of the lattice and an outer concrete layer is poured upon the deck. When cured the concrete layer, the deck and lattice act together in a composite manner.
As shown in Figure 2 transfer means communicate ;~
between an external source of radioactive material and the shielding envelope. The transfer means are for transferring radioactive material to and from the interior of the envelope. As described above the external sources of radioactive material may include a transfer pool 6 and storage pool 4. IN the preferred embodiment illustrated the transfer means includes a liquid filled transfer tunnel 3 communicating between the immersing water 16 of the storage area of the tank 7 and the immersing liquid of the transfer pool 6. The tunnel 3 is preferably : - --:::: :.-., '. ~., :,-.~' : ' ' ' ':
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- 10 - ," " ,, , constructed of high density reinforced concrete to provide a radioactive shield during transfer. Referring to Figures 6 and 8 radioactive material 26 is placed upon a shuttle carriage 27 which is supported upon rails 28 within the tunnel 3. Reciprocating means move the carriage 27 between the storage area of the tank 7 and the transfer pool 6. The carriage 27 in its position within the transfer pool 6 is shown in dashed outline. Therefore radioactive material 26 placed upon the carriage 27 is ~ ~ -10 transferred immersed in shielding liquid to and from the -interior of the shielding envelope. Reciprocating means include a mechanical cable drive assembly 29 located, for ease of maintenance and installation, above the liquid level of the transfer pool 6 adjacent the outer end of the tunnel 3. A drive cable 30 is fixed to the carriage 27 and engages the driver assembly 29. A plurality of ;~
immersed cable pulleys 32 engage the drive cable 30 in a closed loop. The drive assembly 29 may reversibly drive the cable 30 to move the carriage 27. The carriage 27 and 20 rails 28 may be supported within the storage area of the ;
tank 7 upon a cantilevered floor portion 32 of the tunnel 3. When the carriage 27 is moved toward the transfer pool 6 the gate means 24 are closed as shown in Figure 7 to --~ -maintain the integrity of the shielding envelope. The gate means 24 also serve to isolate the tank 7 and transfer pool 6. If radioactive material is released into the transfer pool 6, by accidental dropping during handling for example, the spread of radioactive ;~ ~-contamination to the water 16 of the tank 7 may be prevented by moving the gate means 24 to a closed position. -~
Within the envelope of the radioactive shield means handling means are provided for handling radioactive -material between points within the envelope. In the preferred embodiment illustrated in Figure 2 the handling means comprise an overhead crane 33. Since in the storage XOl~
structure 1 shown the tank 7, liner 12 and concrete side walls 20 are cylindrical; the crane runway 34 upon which the crane 33 runs is circular and the crane 33 spans across the centre of the tank 7. Referring to Figures 6 and 7 the crane 33 is constructed having at least one beam 35 (preferably two) spanning the tank 7 with a boogie 36 at each end of the beam 35 supporting the beam 35 upon crane rails of a crane runway 34 connected to the storage structure 1. A trolley 37 has wheels supported upon -trolley rails on the beam 35. A cable hoist 38 is positioned upon the trolley 37. A catwalk 39 is suspended from the beam 35 having a walking platform accessible from the annular walkway 18 enabling a crane operator to follow the load throughout the lifting operation. Figure 6 shows -15 the crane 33 during lifting of a module of radioactive -material 26 from the carriage ~7. To achieve adequate -shielding for the crane operator the material 26 is submerged at least three meters below the surface of the water 16. Figure 7 illustrates the crane 33 extended to its lowest position placing a tray of radioactive material 26 upon the tank bottom plate 9. A telescoping boom 40 is suspended from the trolley 3~. The boom 40 has a lifting cable engaging the cable hoist 38 to lift the radioactive material. Manipulating means 41 at the lower end of the ~;
25 boom 40 allow the crane operator to engage, disengage and -- ~ - -rotate the radioactive material while standing upon the catwalk 39. The manipulating means 41 and a lower portion of the boom 40 are immersed in the water 16 during the lifting operation.
Spent fuel rods are generally packaged for storage into bundles and sealed in a cylindrical casing.
These casings may then be packaged into trays having a single row of casings (as shown in Fig. 7) or into modules having multiple rows of casings in a honeycomb pattern (as shown in Fig. 6). Since the storage structure 1 must withstand earthquakes and other severe catastrophic events ;~
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as well as accommodate accidents during handling of radioactive materials within the tank 7, in a preferred embodiment some of the trays and modules of radioactive material are stored within the stacking frames 42 illustrated in Figure 9. The stacking frames 42 laterally stabilize stacks of trays or modules placed within the ~ i;
water 16 of the tank 7. The stacking frames 42 are made of stainless steel and adjacent frames 42 may be joined ~ ::
together at points along their height for added stability. :
10 Guide rails are provided within the interior of the frame :
-- 1 -- .
This invention relates to structures for storing and containing radioactive material immersed in liquid.
Spent radioactive fuel must be stored for long periods of time within which the radioactivity of such waste decays.
In the operation of nuclear power plants, or other facilities using radioactive material, spent fuel and other radioactive waste are produced which require specialized storage to prevent irradiation and contamination during radioactive decay. A commonly preferred form of storage utilizes the shielding and heat dissipation properties of water in storing radioactive material in pools. The radioactive material may be safely handled below the surface of the water by personnel -wearing minimal protective equipment. The heat generated by the radioactive decay of the stored material is dissipated by the convection of the water. Heat is ;~
thereafter transferred to the ambient air above the pool or reduced by immersed heat transfer units. When decayed to a low level of radiation the radioactive material may be permanently disposed of.
Structures containing pools for storage of radioactive material have been constructed in general as part of a power station. Primary and secondary irradiated fuel storage bays in generating stations may have rectangular storage pools lined with panels of carbon steel welded together at their edges to form a water-tight barrier. The panels may comprise a carbon steel plate welded to a frame of steel channels which is embedded in the concrete walls forming the pool. The carbon steel ~ -liner plate may be coated with corrosion resistant paint.
Correct application and continued maintenance of such coatings is required to prevent liner deterioration. , Leakage of such storage pools is difficult to detect and repair since access is limited to the interior of the pool. Water may flow through a crack in the steel plate Z016~?~
pool liner into cracks in the concrete. Detecting and locating the source of leakage from the outer surface of the concrete wall is extremely difficult and costly. To repair the steel plate pool liner the radioactive material must be removed to allow human access involving costly handling which increases the risk of contamination.
Significant quantities of contaminated liquid may penetrate such steel liners, and concrete walls and percolate through the surrounding soil before leakage is 10 detected and repairs are undertaken. -~-Existing storage pools also suffer from the disadvantage that they are physically integrated into a power station facility. The storage period for spent fuel exceeds the power station's viable economic life since the 15 reactors deteriorate under radioactive conditions and must -~ ~-be either abandoned or completely rebuilt. The reactors ~ ~
and related generating equipment also become rapidly --obsolete due to technical advances during the storage period. For these reasons therefore it is disadvantageous to operate the storage facility together with the power generating facility. If it is desirable that a power facility be abandoned or destroyed it is inefficient to -~
maintain the facility merely as a storage facility. If a ~ ;~
power facility is to be reconstructed, the related 25 activity may jeopardize or obstruct the storage function. ;~
Due to the extensive storage period and `
concentration of harmful radioactive materials in such .
, . ~ ~: .
storage facilities the security and integrity of such facilities is critical. Events such as severe - - ~
30 earthquakes, airplane crashes, nuclear explosions, ~ ~-sabotage and aggression are considered as low probability -risks in general but due to their potantially catastrophic consequences such storage facilities must be designed to ` ;~
address these contingencies. Containment of radioactivity ;~
and maintenance of the structural integrity in ''''' "'' ' '" ' 2C)16~
catastrophic circumstances is difficult when the storage facility is structurally integrated into the power facility since vibrations, forces and structural damage may propagate from one part of the structure to another.
The present invention reduces or eliminates the -~
above disadvantages by providing a substantially structurally independent storage facility having a storage ~ ;
tank which is accessible for inspection and repair, within a containment liner to contain any leakage.
In accordance with the invention is provided a structure, for the storage and containment of radioactive -material immersed in liquid, comprising: a tank having side and bottom walls defining a storage area within which said radioactive material and immersing liquid are ~ ~-15 accommodated; a tank platform having an upper surface -supporting the bottom wall of said tank, said tank platform having a plurality of galleries providing access to said tank bottom wall for repair and inspection; a containment liner spaced from said tank and having side and bottom walls to contain said liquid upon rupture of or leakage from said tank, said liner side wall and tank side wall defining a peripheral space therebetween to provide access to said tank side walls for repair and inspection, said liner bottom wall supporting the lower surface of said tank platform; radioactive shield means, outward of said liner and above the upper open end of said tank, for enveloping and isolating said radioactive material and ~immersing liquid within a shielding envelope; transfer means, communicating between an external source of said radioactive material and said envelope, for transferring said radioactive material to and from the interior of said ~-~
envelope; and handling means, within the envelope of said radioactive shield means, for handling said radioactive material within said envelope.
)16~
In order that the invention may be readily understood, an embodiment of the invention will be described by way of example with reference to the accompanying drawings.
Figure 1 is a partially broken away perspective view of a structure in accordance with the invention having a storage facility towards the upper right, and an -associated power generating facility and transfer means toward the lower left of the drawing. ;
"';"~ ~ '"' '.
Figure ~ is a sectional view along line 2-2 of Fig. 1.
Figure 3 is a partially broken away plan view along line 3-3 of Fig. 2.
Figures 4 and 5 illustrate an alternative ~;
storage structure roof in plan and elevation respectively wherein a cone shaped structural lattice is constructed (instead of a dome roof as in Figures 1, 2 and 3).
Figure 6 shows the transfer means and handling ~- ;
means in sectional elevation. ~ `
Figure 7 shows the handling means extended to - -~
the bottom of the tank and the inner end of the liquid filled transfer tunnel in sectional elevation.
Figure 8 is a sectional plan view through the transfer tunnel showing the transfer means.
Figure 9 is a perspective view of a stacking frame for stacking trays or modules of spent fuel bundles within the tank.
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~.
:
In a preferred embodiment the storage structure of the present invention is constructed adjacent a nuclear power generating station. A storage structure may be constructed at an independent site but generally the transport of radioactive material outside containment areas is minimized to avoid contamination risks and reduce the costs involved.
As illustrated in Figure 1 a storage structure 1 may be constructed adjacent a nuclear power generating facility 2. Transfer means including an under water transfer tunnel 3 communicate between the storage structure 1 and the generating facility 2. Within the generating facility 2 radioactive material, such as spent fuel bundles, are stored under water in a conventional rectangular storage pool 4 for approximately six to ten years until radioactive decay has progressed to the stage ~
where long term storage is feasible. referring to Figure -2, radioactive material is transferred under water from the storage pool 4 to transfer means at the outer end of the transfer tunnel 3 using an overhead travelling crane within the generating facility 2. The radioactive material is then transferred through the transfer tunnel 3 under water to the interior of the storage structure 1 as will be described in detail below. Radioactive material originating from other power facilities or operations may be shipped by rail or truck to the loading dock area 5 for eventual storage in the storage structure 1. The material - ~
is shipped in sealed isolating casks which are lifted from ~ -the trucks or rail cars and placed in a transfer pool 6~by the overhead crane. The casks are then opened under water and the radioactive material removed. The radioactive ~
material may be temporarily stored within the transfer -pool 6 or may directly be placed upon the transfer means to be transferred to the interior of the storage structure 1. When the radioactive material has decayed and may be safely disposed of permanently, the above process is -~
2016~
reversed wherein radioactive material is transferred from the storage structure 1 to the transfer pool 6, is placed within shipping casks under water in the transfer pool 6 and is thereafter placed upon trucks or rail cars in the loading dock area 5 to be transported to a disposal site.
The detailed construction of the storage structure for the storage and containment of radioactive ~
material immersed in liquid is illustrated in Figure 2. A ;
tank 7 having a side and a bottom wall 8 and 9 provides within its interior a storage area for the radioactive material and immersing liquid. The tank 7 is preferably constructed of stainless steel plate such as ASTM A 240 Type 304 for superior corrosion resistance. Preferably the tank 7 is cylindrical since the tank 7 may then be ~ ~ ~
15 self supporting and may be constructed according to well ; -known methods. Any shape of tank 7 however may be used in ~ , accordance with the invention such as rectangular or square provided the side walls 7 are braced. The bottom wall 9 of the tank 7 is supported upon a tank platform 10 ~-which has a plurality of galleries 11 providing access to the tank bottom wall 9 for inspection and repair in the event of leakage. In the embodiment illustrated the tank ~-platform 10 comprises a series of parallel reinforced -;~
concrete walls capped by a reinforced concrete slab which supports the tank bottom wall 9. Inspection may be carried out using by personnel wearing suitable protective equipment, by remote control mechanisms or through the use of sound sensors. When leakage is detected repairs to the -~
tank bottom plate 9 may be carried out by injecting sealants or grout, or by removing a portion of the concrete slab, welding the tank bottom plate 9 overhead and thereafter repairing the concrete slab.
To contain contaminated water upon rupture of or -leakage from the tank 7 a containment liner 12 is spaced 35 outward from the tank 7. The containment liner 12 has a ~i;
~ i . , , 2~
side wall 13 and a bottom wall 14, preferably forming a cylindrical welded steel containment tank within which the storage tank 7 is nested. The lower surface of the tank platform 10 is supported upon the liner bottom wall 14.
5 The liner side wall 13 and the tank side wall 8 define a peripheral space 15 between them providing access to the tank side wall 8 for inspection and repair. The containment liner 12 is a secondary containment system which is used only in the event of leakage from the 10 primary containment system namely the tank 7. The containment liner 12 therefore may be constructed of carbon steel possibly coated with a corrosion resistant coating in exposed areas. The galleries 11 of the tank platform 10 and the peripheral space 15 are outwardly 15 connected providing access also to the containment liner 12 for inspection and repair of the liner 12.
Heat generated by the radioactive decay of the stored material is first transferred to the water 16 in which the material is immersed within the tank 7. Due to 20 convection the water 16 is circulated and warmer water 16 accumulates towards the upper surface of the water 16.
Conventional heat transfer devices may be immersed within the tank 7 to cool the upper region of the water 16 ~
maintaining the temperature of the water 16. The -peripheral space 15, galleries 11 and air plenum 17 above the water surface communicate to provide air circulation around the tank 7. The air circulates to additionally 3 cool the water 16 within the tank 7. In the event of ~-failure of the heat transfer device the passive cooling of 30 this air circulation provides a further degree of safety against overheating of the decaying radioactive material.
The upper edge of the tank side wall 8 is located above the water surface and the upper edge of the liner side wall 13 extends above the upper edge of the ~, 35 tank side wall 8. A horizontal annular walkway 18 spans 6~
between the upper portions of the tank side wall 8 and the liner side wall enabling personnel access within the storage structure 1. Preferably the walkway 18 is constructed of open grating to enable air circulation as -described above. In the event of an earthquake, accidental dropping of material, or other catastrophic event, waves may breach the upper edge of the tank side wall 8. It is desirable to dampen such waves and prevent reverberations since the stored radioactive material and ' -~
10 components of the structure 1 may be subjected to dynamic ~ -wave forces causing damage. The water 16 breaching the -upper edge of the tank side walls flows through the open grating of the walkway 18 and is retained within the containment liner 12. The propagation and reflection of waves is thereby reduced and dampened. The water within the containment liner 12 may thereafter be pumped back into the tank 7.
: ~'`
In order to envelope and isolate the radioactive material and immersing liquid within a radioactive ~-~
shielding envelope, radioactive shield means are provided outward of the liner 12 and above the upper open end oP
the tank 7. In a preferred embodiment the radioactive ~ -shield means comprise: a concrete foundation slab 19 ~ `~
beneath the liner bottom wall 14; concrete side walls 20, 25 outward of the liner side wall 13, supported upon the -foundation slab 19 and having a transfer port 21 providing access to the transfer means; and a roof structure 22 having a concrete shielding layer 23 and supported upon the concrete side walls 20. The radiation shield means 30 also include gate means 24, as shown in Figure 6, adjacent - ;
the transfer port 21. The gate means 24 are for opening the transfer port 21 when radioactive material is - -transferred to and from the interior of the shielding envelope and for closing the transfer port 21 to maintain 35 the integrity of the shielding envelope. Preferably the -concrete of the radioactive shielding means is of high ~
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2016~
g density having aggregates of magnetite or specularite for their superior radioactive shielding properties.
'':, In the embodiment illustrated in the drawings -the tank 7, liner 12 and concrete side walls 20 are all cylindrical. The liner 12 is used as a form when the concrete side walls 20 are poured either through well known slip forming or block and filler techniques.
Two alternate roof structures 22 are illustrated. Referring to Figure 2 the roof structure may comprise a post-tensional reinforced concrete dome, the concrete of which forms a concrete shielding layer. A
concrete dome is exceptionally strong and capable of withstanding severe catastrophic events, but is relatively expensive to build. Referring to Figures 4 and 5 an 15 alternate composite roof structure 22 is illustrated which -is less expensive than a dome but is less capable of -withstanding severe loadings. The composite roof structure 22 is constructed of an inner cone-shaped -structural steel lattice of radial trusses 25. A
corrugated sheet steel roof deck is outwardly attached to the purlins of the lattice and an outer concrete layer is poured upon the deck. When cured the concrete layer, the deck and lattice act together in a composite manner.
As shown in Figure 2 transfer means communicate ;~
between an external source of radioactive material and the shielding envelope. The transfer means are for transferring radioactive material to and from the interior of the envelope. As described above the external sources of radioactive material may include a transfer pool 6 and storage pool 4. IN the preferred embodiment illustrated the transfer means includes a liquid filled transfer tunnel 3 communicating between the immersing water 16 of the storage area of the tank 7 and the immersing liquid of the transfer pool 6. The tunnel 3 is preferably : - --:::: :.-., '. ~., :,-.~' : ' ' ' ':
~ : . ..
: ~ , ~ :: - .
~)15~
- 10 - ," " ,, , constructed of high density reinforced concrete to provide a radioactive shield during transfer. Referring to Figures 6 and 8 radioactive material 26 is placed upon a shuttle carriage 27 which is supported upon rails 28 within the tunnel 3. Reciprocating means move the carriage 27 between the storage area of the tank 7 and the transfer pool 6. The carriage 27 in its position within the transfer pool 6 is shown in dashed outline. Therefore radioactive material 26 placed upon the carriage 27 is ~ ~ -10 transferred immersed in shielding liquid to and from the -interior of the shielding envelope. Reciprocating means include a mechanical cable drive assembly 29 located, for ease of maintenance and installation, above the liquid level of the transfer pool 6 adjacent the outer end of the tunnel 3. A drive cable 30 is fixed to the carriage 27 and engages the driver assembly 29. A plurality of ;~
immersed cable pulleys 32 engage the drive cable 30 in a closed loop. The drive assembly 29 may reversibly drive the cable 30 to move the carriage 27. The carriage 27 and 20 rails 28 may be supported within the storage area of the ;
tank 7 upon a cantilevered floor portion 32 of the tunnel 3. When the carriage 27 is moved toward the transfer pool 6 the gate means 24 are closed as shown in Figure 7 to --~ -maintain the integrity of the shielding envelope. The gate means 24 also serve to isolate the tank 7 and transfer pool 6. If radioactive material is released into the transfer pool 6, by accidental dropping during handling for example, the spread of radioactive ;~ ~-contamination to the water 16 of the tank 7 may be prevented by moving the gate means 24 to a closed position. -~
Within the envelope of the radioactive shield means handling means are provided for handling radioactive -material between points within the envelope. In the preferred embodiment illustrated in Figure 2 the handling means comprise an overhead crane 33. Since in the storage XOl~
structure 1 shown the tank 7, liner 12 and concrete side walls 20 are cylindrical; the crane runway 34 upon which the crane 33 runs is circular and the crane 33 spans across the centre of the tank 7. Referring to Figures 6 and 7 the crane 33 is constructed having at least one beam 35 (preferably two) spanning the tank 7 with a boogie 36 at each end of the beam 35 supporting the beam 35 upon crane rails of a crane runway 34 connected to the storage structure 1. A trolley 37 has wheels supported upon -trolley rails on the beam 35. A cable hoist 38 is positioned upon the trolley 37. A catwalk 39 is suspended from the beam 35 having a walking platform accessible from the annular walkway 18 enabling a crane operator to follow the load throughout the lifting operation. Figure 6 shows -15 the crane 33 during lifting of a module of radioactive -material 26 from the carriage ~7. To achieve adequate -shielding for the crane operator the material 26 is submerged at least three meters below the surface of the water 16. Figure 7 illustrates the crane 33 extended to its lowest position placing a tray of radioactive material 26 upon the tank bottom plate 9. A telescoping boom 40 is suspended from the trolley 3~. The boom 40 has a lifting cable engaging the cable hoist 38 to lift the radioactive material. Manipulating means 41 at the lower end of the ~;
25 boom 40 allow the crane operator to engage, disengage and -- ~ - -rotate the radioactive material while standing upon the catwalk 39. The manipulating means 41 and a lower portion of the boom 40 are immersed in the water 16 during the lifting operation.
Spent fuel rods are generally packaged for storage into bundles and sealed in a cylindrical casing.
These casings may then be packaged into trays having a single row of casings (as shown in Fig. 7) or into modules having multiple rows of casings in a honeycomb pattern (as shown in Fig. 6). Since the storage structure 1 must withstand earthquakes and other severe catastrophic events ;~
,"'', `' ' ''. ' '':
016!~
- 12 - .
as well as accommodate accidents during handling of radioactive materials within the tank 7, in a preferred embodiment some of the trays and modules of radioactive material are stored within the stacking frames 42 illustrated in Figure 9. The stacking frames 42 laterally stabilize stacks of trays or modules placed within the ~ i;
water 16 of the tank 7. The stacking frames 42 are made of stainless steel and adjacent frames 42 may be joined ~ ::
together at points along their height for added stability. :
10 Guide rails are provided within the interior of the frame :
4~ to accurately place the tray~ or module~
' " ~
~'
' " ~
~'
Claims (14)
1. A structure, for the storage and containment of radioactive material immersed in liquid, comprising:
a tank having side and bottom walls defining a storage area within which said radioactive material and immersing liquid are accommodated;
a tank platform having an upper surface supporting the bottom wall of said tank, said tank platform having a plurality of galleries providing access to said tank bottom wall for repair and inspection;
a containment liner spaced from said tank and having side and bottom walls to contain said liquid upon rupture of or leakage from said tank, said liner side wall and tank side wall defining a peripheral space therebetween to provide access to said tank side walls for repair and inspection, said liner bottom wall supporting the lower surface of said tank platform;
radioactive shield means, outward of said liner and above the upper open end of said tank, for enveloping and isolating said radioactive material and immersing liquid within a shielding envelope;
transfer means, communicating between an external source of said radioactive material and said envelope, for transferring said radioactive material to and from the interior of said envelope; and handling means, within the envelope of said radioactive shield means, for handling said radioactive material within said envelope.
a tank having side and bottom walls defining a storage area within which said radioactive material and immersing liquid are accommodated;
a tank platform having an upper surface supporting the bottom wall of said tank, said tank platform having a plurality of galleries providing access to said tank bottom wall for repair and inspection;
a containment liner spaced from said tank and having side and bottom walls to contain said liquid upon rupture of or leakage from said tank, said liner side wall and tank side wall defining a peripheral space therebetween to provide access to said tank side walls for repair and inspection, said liner bottom wall supporting the lower surface of said tank platform;
radioactive shield means, outward of said liner and above the upper open end of said tank, for enveloping and isolating said radioactive material and immersing liquid within a shielding envelope;
transfer means, communicating between an external source of said radioactive material and said envelope, for transferring said radioactive material to and from the interior of said envelope; and handling means, within the envelope of said radioactive shield means, for handling said radioactive material within said envelope.
2. A structure according to claim 1 wherein said radioactive shield means comprise;
a concrete foundation slab beneath said bottom liner wall;
concrete side walls outward said side liner walls, supported upon said foundation slab and having a transfer port providing access to said transfer means;
a roof structure, having a concrete shielding layer, said roof structure supported upon said concrete side walls; and gate means adjacent said transfer port for opening said transfer port when radioactive material is transferred to and from the interior of said envelope, and for closing said transfer port to maintain the integrity of said shielding envelope.
a concrete foundation slab beneath said bottom liner wall;
concrete side walls outward said side liner walls, supported upon said foundation slab and having a transfer port providing access to said transfer means;
a roof structure, having a concrete shielding layer, said roof structure supported upon said concrete side walls; and gate means adjacent said transfer port for opening said transfer port when radioactive material is transferred to and from the interior of said envelope, and for closing said transfer port to maintain the integrity of said shielding envelope.
3. A structure according to claim 2 wherein said tank, liner, and concrete side walls are cylindrical.
4. A structure according to claim 3 wherein said roof structure comprises a post-tensioned reinforced concrete dome.
5. A structure according to claim 3 wherein said roof structure is a composite roof structure comprising:
an inner cone-shaped structural steel lattice of radial trusses;
a corrugated sheet steel roof deck outwardly attached to said lattice; and an outer concrete layer engaging said deck.
an inner cone-shaped structural steel lattice of radial trusses;
a corrugated sheet steel roof deck outwardly attached to said lattice; and an outer concrete layer engaging said deck.
6. A structure according to claim 1 wherein said handling means comprises an overhead crane.
7. A structure according to claim 6 wherein said overhead crane comprises:
a beam spanning said tank;
two bogies at the ends of said beam supporting said beam upon the crane rails of a crane runway connected to said structure;
a trolley having wheels supported upon the trolley rails of said beam, said trolley including a cable hoist;
a catwalk suspended from said beam; and a telescoping boom suspended from said trolley, said boom having a lifting cable engaging said cable hoist to lift said radioactive material, and having manipulating means, at the lower end of said boom, for engaging, disengaging and rotating said radioactive material under the control of an operator located upon said catwalk, said manipulating means and a lower portion of said boom being immersed in said liquid during operation.
a beam spanning said tank;
two bogies at the ends of said beam supporting said beam upon the crane rails of a crane runway connected to said structure;
a trolley having wheels supported upon the trolley rails of said beam, said trolley including a cable hoist;
a catwalk suspended from said beam; and a telescoping boom suspended from said trolley, said boom having a lifting cable engaging said cable hoist to lift said radioactive material, and having manipulating means, at the lower end of said boom, for engaging, disengaging and rotating said radioactive material under the control of an operator located upon said catwalk, said manipulating means and a lower portion of said boom being immersed in said liquid during operation.
8. A structure according to claim 7 wherein said tank and liner are cylindrical, said crane runway is circular and said beam spans across the centre of said tank.
9. A structure according to claim 1 wherein said transfer means comprises;
a liquid filled transfer tunnel communicating between the immersing liquid of said storage area and the immersing liquid of an external source of radioactive material;
a shuttle carriage supported upon rails within said tunnel; and reciprocating means for moving said carriage between said storage area and said external source, whereby radioactive material placed upon said carriage is transferred immersed in liquid to and from the interior of said envelope.
a liquid filled transfer tunnel communicating between the immersing liquid of said storage area and the immersing liquid of an external source of radioactive material;
a shuttle carriage supported upon rails within said tunnel; and reciprocating means for moving said carriage between said storage area and said external source, whereby radioactive material placed upon said carriage is transferred immersed in liquid to and from the interior of said envelope.
10. A structure according to claim 9 wherein said reciprocating means comprise:
a mechanical cable drive assembly located above the liquid level adjacent the outer end of said tunnel;
a drive cable fixed to said carriage and engaging said drive assembly; and a plurality of immersed cable pulleys engaging said drive cable in a closed loop.
a mechanical cable drive assembly located above the liquid level adjacent the outer end of said tunnel;
a drive cable fixed to said carriage and engaging said drive assembly; and a plurality of immersed cable pulleys engaging said drive cable in a closed loop.
11. A structure according to claim 9 wherein said transfer means further comprise:
a liquid filled upwardly open transfer pool communicating with said transfer tunnel; and means for transferring said radioactive material from said external source to the liquid of said transfer pool and from said transfer pool to said shuttle carriage.
a liquid filled upwardly open transfer pool communicating with said transfer tunnel; and means for transferring said radioactive material from said external source to the liquid of said transfer pool and from said transfer pool to said shuttle carriage.
12. A structure according to claim 1 wherein said tank is made of stainless steel.
13. A structure according to claim 1 wherein said liner is made of carbon steel.
14. A structure according to claim 1 wherein said tank platform comprises reinforced concrete.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US49626090A | 1990-03-20 | 1990-03-20 | |
| US496,260 | 1990-03-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2016923A1 true CA2016923A1 (en) | 1991-09-20 |
Family
ID=23971904
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2016923 Abandoned CA2016923A1 (en) | 1990-03-20 | 1990-05-16 | Radioactive material storage structure |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2016923A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102913026A (en) * | 2012-10-31 | 2013-02-06 | 中国十九冶集团有限公司 | Construction method and pouring structure in prestressed tendon position of prestressed coal bin cylinder wall |
| CN107545937A (en) * | 2017-08-25 | 2018-01-05 | 中国核工业华兴建设有限公司 | Nuclear power plant containment shell Leak-tight liner integral type link block structure and its installation method |
-
1990
- 1990-05-16 CA CA 2016923 patent/CA2016923A1/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102913026A (en) * | 2012-10-31 | 2013-02-06 | 中国十九冶集团有限公司 | Construction method and pouring structure in prestressed tendon position of prestressed coal bin cylinder wall |
| CN107545937A (en) * | 2017-08-25 | 2018-01-05 | 中国核工业华兴建设有限公司 | Nuclear power plant containment shell Leak-tight liner integral type link block structure and its installation method |
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