Patent Number: 047012803
Section: description

In the rock 1 there is incorporated a hollow space 2, which is connected to the surface (not shown) via a lift-shaft 3. The lift shaft 3 has one or more levels (one is shown in the drawing). Inside the hollow space 2 there is a hollow construction 4, the outside of which, with a space in between, is completely separated from the walls, ceiling and floor of the hollow space. Construction 4 consists of a permanent material impervious to water, and the interstice or the outer space between the walls of the hollow space and the construction, is filled with a material 5 which is non-impervious to water, for example shingle. In the example shown, the floor of the rock chamber is provided with a draining channel 6, which ends in a basin 7 at the end of the space. An opening 8, shown in FIG. 1 connects the lift-shaft 3 with the interior of construction 4. We shall now describe how the invention provides for permanent storage of the encapsulated radioactive material. Material capsules 9 transported through lift-shaft 3 down to the opening 8, where they are moved by a robot, indicated in FIG. 2, by the numeral 10, into construction 4 and placed at equal intervals in rows on either side of a track 11 for robot 10. Under each material capsule 9 there is collecting and checking vessel 12. The construction should preferably be filled with radioactive material starting from back. When the construction is filled with material capsules, the robot is taken out and raised up through the shaft 3 to ground level or any other suitable level. Then the construction is filled with filling material, for example bentonite, completely enclosing the capsules by means of e.g. channels or similar. Along the middle of the construction, enough space 13 is left for the robot, to enable it to move along the track. If there is likely to be a long period of time between filling of encapsulated radioactive materials, the capsules leaded into the construction should at once be sealed into that part of the construction where they are positioned. The track or passage 13 formed in the bentonite is filled in with a water-displacing material, which must, however, be easy to dig, for example shingle. When construction 4 is filled with material capsules, the construction filled out with bentonite, and the passage filled in with the water-displacing material, opening 8 is sealed up, filled out with material non-impervious to water in front of the opening, and the lower end of the lift-shaft is sealed up at the same height as the construction. The lift-shaft must also be sealed at ground and surface level and possibly at one or more places between. If the construction lies in bed-rock above the level of the ground water, the surface water will be prevented from penetrating the completely water-impermeable construction, which is totally filled anyway, and therefore has no cavities that could collect water, and is fed instead in the water-permeable layer 5 down to basin 7. This can be provided with equipment of known principles enabling samples of the water to be taken from ground level in order to check on contamination from the radioactive material. If the construction is situated under the level of the ground water, basin 7 can be omitted and samples can be taken directly from layer 5, where the ground water will come to rest. But even in this case, it would be preferable to retain basin 7, since it would be thereby possible to collect the water surrounding construction 4, should this be necessary, by emptying basin 7 of the water coming to the basin from water-permeable layer 5. The collecting and checking vessel 12 can likewise be checked in conventional fashion from ground-level with regard to radioactive radiation. As previously mentioned, the checking vessel can either moulded into the bentonite or made accessible from passage 13 and easily removeable for checking. If a material capsule 9 should thus start to leak, this will not be observed until vessel 12 is checked, since this is where the leakage arrives first. If this primary means if checking has been missed or should prove impossible to carring out, there still remains the secondary chance of checking the radioactivity of the water flowing round or surrounding the outside of construction 4. Provisions must be made to allow water to be pumped up from basin 7 or outer room 5. If a leakage is confirmed under a capsule 9 with, for example, the help of control vessel 12, and it is considered necessary to rectify fault, lift-shaft 3 is opened and the robot is lowered down to the construction. The robot breaks its way in through the closed-off opening of the construction, and digs its way forwards through passage 13 along track 11 until it reaches the leaking material capsule. From passage 13 the robot digs the capsule out from the bentonite and transports the capsule to lift-shaft 3. The capsule is transported thereafter through the tunnel to ground-level for further treatment. When it is considered suitable, whether the repaired capsule is returned to its original place with the aid of the robot or not, the interior of the construction is returned to its original condition and the lift-shaft is sealed off again. From the above it will be seen that the invention provides for a permanent storage with secure barriers that provent the encapsulated radioactive material from coming into contact with water outside the external walls of the storage room. It should not be necessary to check the material, but there are simple and safe means of checking. There is no need for ventilation of the construction, and collecting-layer 5 serves for any necessary removal of heat. The layer will withstand relative movement between the rock wall and construction 4. Where suitable, a layer of elastic or plastic material can be placed inside construction 4, i.e. between it and the bentonite, in order to permit a certain movement between the construction and the bentonite, partly because of different coefficients of expansion in the materials. Although the invention is described for use with a robot, it is of course possible to control the equipment manually. The material capsules referred to may consist of conventional material approved by the authorities, and the form of the capsules for the material is such as to fulfil official requirement. The checking mechanisms for measuring the radioactivity of the water are also of types already familiar to technology and, as will be obvious, other measuring equipment can also used for measuring temperature on and inside the construction and for other purposes.