GB2090461A - Storing radio-active waste - Google Patents

Abstract

In storing radioactive waste, material, eg vitrified radio-active waste, a chamber is used wherein an array of vertical elongate thimbles 1 or 1' accommodate canisters 2 of waste such that the cooling air flow within the chamber does not come into contact with canisters 2. The air-flow over the thimbles may be improved by surrounding them with sleeves 8 which are supported on fins 9 to provide an annular coolant channel 10. The canisters are loaded and unloaded via plugged orifices 3. <IMAGE>

Description

SPECIFICATION Improvements in and relating to the storage of radioactive wastes The present invention concerns the storage of radioactive wastes.

It is known to store vitrified radioactive wastes in channels within a shielded chamber or cave. Cooling is achieved by circulating an air flow directly over the wastes. As a result the cooling air can become contaminated and requires efficient and effective filtration before discharge into the atmosphere.

According to the present invention a chamber for the storage of radioactive wastes comprises a shielded cave housing an array of vertical elongate thimbles adapted to receive and enclose the wastes such that a cooling air flow within the cave is isolated from the radioactive wastes within the thimbles. Preferably, each thimble is surrounded by a concentric sleeve to thereby form a plurality of annular flow passages for the cooling air.

The invention will be described further, by way of example, with reference to the accompanying drawings; in which Figure 1 is a sectional elevation of part of a storage chamber for radioactive wastes and showing 2 possible alternative arrangements; and Figure 2 is a section on the line A-A in Fig.

1.

A storage chamber for radioactive wastes comprises a compartment bounded by walls of a shielding material and housing an array of vertical elongate thimbles 1 or 1'-. The thimbles 1 or 1 ' - accommodate canisters 2 of vitrified radioactive wastes and the canisters 2 are loaded and unloaded into and out of the thimbles through openings in the upper wall of the compartment, the openings being closed by removable shielding plugs 3. In Fig.

1, each thimble 1 accommodates 8 individual canisters 2 stacked end to end and it will be realised that this number is merely by way of example.

The lower ends of the thimbles are closed and are supported on pillars 4. At the upper end of each pillar a spigot 5 co-operates with an aperture or recess in the closed end of the associated thimble. The pillars 4 support the thimbles clear of the bottom of the compartment to define a lower plenum chamber 6.

A steel grid or grating 7 is secured to the upper ends of the pillars 4 below the spigots 5 to provide a support for sleeves 8 disposed about the thimbles. The fins 9 on the exterior of each thimble locate the sleeves concentrically about the thimbles to create substantially uniform annular flow passages 10 extending between the lower plenum chamber 6 beneath the grating 7 and an upper plenum chamber 11 beneath the upper wall of the chamber. A grid or web 1 2 can be arranged at the upper ends of the sleeves to provide lateral stability, the grid being anchored to the side walls of the chamber.

The canisters are loaded and unloaded by means of a charge machine (not shown). With the thimble 1, a charge tube is inserted through the aperture in the upper wall upon removal of the plug 3 to bridge the upper plenum and enter the upper end of the associated thimble. In this way the canisters are isolated from the air within the chamber during loading and unloading operations. Upon withdrawal of the charge tube the upper end of the thimble can be closed by a cap to isolate the interior of the thimble.

In the alternative arrangement, the thimbles 1 ' - extend across the upper plenum chamber 11 to the upper wall of the chamber. In this way the interior of each thimble 1 ' - is at all times effectively isolated from the air within the chamber.

The canisters of radioactive wastes fit in static air pockets within the thimbles and cooling air flow is isolated from direct contact with the canisters. The heat emitted by the wastes generates convection currents in the air. The thimbles provide the heat transfer surfaces and the cooling air is funnelled through the annular flow passages 10. As the airflow does not come into direct contact with the wastes the air cannot entrain any contamination which might be present on the surfaces of the canisters. As a result, absolute filters can be avoided at an outlet duct or ducts from the upper plenum and an adequate air flow can result from natural convection avoid the use of fans and achieving a significant saving on capital and operating costs.Further, as the air flows through the annular flow passages 10 it is not required to employ individual gags to correct variations in flow between empty and full thimbles.

1. A chamber for the storage of radioactive wastes comprising a shielded compartment housing an array of vertical elongate thimbles adapted to receive and house the wastes such that a cooling air flow within the cave is isolated from the radioactive wastes within the thimbles.

2. A chamber as claimed in claim 1 in which each thimble is surrounded by a concentric sleeve to therapy form a plurality of annular flow passages for the cooling air.

3. A chamber as claimed in claim 2 in which the thimbles and sleeves are supported with their lower ends clear of the bottom of the compartment.

4. A chamber as claimed in claim 3 in which the upper ends of the thimbles terminate short of filler openings in the upper wall of the compartment.

5. A chamber for the storage of radioactive materials substantially as herein described

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in and relating to the storage of radioactive wastes The present invention concerns the storage of radioactive wastes. It is known to store vitrified radioactive wastes in channels within a shielded chamber or cave. Cooling is achieved by circulating an air flow directly over the wastes. As a result the cooling air can become contaminated and requires efficient and effective filtration before discharge into the atmosphere. According to the present invention a chamber for the storage of radioactive wastes comprises a shielded cave housing an array of vertical elongate thimbles adapted to receive and enclose the wastes such that a cooling air flow within the cave is isolated from the radioactive wastes within the thimbles. Preferably, each thimble is surrounded by a concentric sleeve to thereby form a plurality of annular flow passages for the cooling air. The invention will be described further, by way of example, with reference to the accompanying drawings; in which Figure 1 is a sectional elevation of part of a storage chamber for radioactive wastes and showing 2 possible alternative arrangements; and Figure 2 is a section on the line A-A in Fig. 1. A storage chamber for radioactive wastes comprises a compartment bounded by walls of a shielding material and housing an array of vertical elongate thimbles 1 or 1'-. The thimbles 1 or 1 ' - accommodate canisters 2 of vitrified radioactive wastes and the canisters 2 are loaded and unloaded into and out of the thimbles through openings in the upper wall of the compartment, the openings being closed by removable shielding plugs 3. In Fig. 1, each thimble 1 accommodates 8 individual canisters 2 stacked end to end and it will be realised that this number is merely by way of example. The lower ends of the thimbles are closed and are supported on pillars 4. At the upper end of each pillar a spigot 5 co-operates with an aperture or recess in the closed end of the associated thimble. The pillars 4 support the thimbles clear of the bottom of the compartment to define a lower plenum chamber 6. A steel grid or grating 7 is secured to the upper ends of the pillars 4 below the spigots 5 to provide a support for sleeves 8 disposed about the thimbles. The fins 9 on the exterior of each thimble locate the sleeves concentrically about the thimbles to create substantially uniform annular flow passages 10 extending between the lower plenum chamber 6 beneath the grating 7 and an upper plenum chamber 11 beneath the upper wall of the chamber. A grid or web 1 2 can be arranged at the upper ends of the sleeves to provide lateral stability, the grid being anchored to the side walls of the chamber. The canisters are loaded and unloaded by means of a charge machine (not shown). With the thimble 1, a charge tube is inserted through the aperture in the upper wall upon removal of the plug 3 to bridge the upper plenum and enter the upper end of the associated thimble. In this way the canisters are isolated from the air within the chamber during loading and unloading operations. Upon withdrawal of the charge tube the upper end of the thimble can be closed by a cap to isolate the interior of the thimble. In the alternative arrangement, the thimbles 1 ' - extend across the upper plenum chamber 11 to the upper wall of the chamber. In this way the interior of each thimble 1 ' - is at all times effectively isolated from the air within the chamber. The canisters of radioactive wastes fit in static air pockets within the thimbles and cooling air flow is isolated from direct contact with the canisters. The heat emitted by the wastes generates convection currents in the air. The thimbles provide the heat transfer surfaces and the cooling air is funnelled through the annular flow passages 10. As the airflow does not come into direct contact with the wastes the air cannot entrain any contamination which might be present on the surfaces of the canisters. As a result, absolute filters can be avoided at an outlet duct or ducts from the upper plenum and an adequate air flow can result from natural convection avoid the use of fans and achieving a significant saving on capital and operating costs.Further, as the air flows through the annular flow passages 10 it is not required to employ individual gags to correct variations in flow between empty and full thimbles. CLAIMS

1. A chamber for the storage of radioactive wastes comprising a shielded compartment housing an array of vertical elongate thimbles adapted to receive and house the wastes such that a cooling air flow within the cave is isolated from the radioactive wastes within the thimbles.

2. A chamber as claimed in claim 1 in which each thimble is surrounded by a concentric sleeve to therapy form a plurality of annular flow passages for the cooling air.

3. A chamber as claimed in claim 2 in which the thimbles and sleeves are supported with their lower ends clear of the bottom of the compartment.

4. A chamber as claimed in claim 3 in which the upper ends of the thimbles terminate short of filler openings in the upper wall of the compartment.

5. A chamber for the storage of radioactive materials substantially as herein described with reference to and as illustrated in the accompanying drawings.