GB2165085A

GB2165085A - Improvements in containers for encapsulating wastes

Info

Publication number: GB2165085A
Application number: GB08424566A
Authority: GB
Inventors: Robert Barnby Rigg
Original assignee: British Nuclear Fuels PLC
Current assignee: Sellafield Ltd
Priority date: 1984-09-28
Filing date: 1984-09-28
Publication date: 1986-04-03
Also published as: GB2165085B; GB8424566D0

Abstract

In the encapsulation of wastes with cement or grout so as to form solid blocks suitable for subsequent storage or disposal, the drum is provided with a baffle positioned within the open end thereof adapted to assist the dispersion of the cement grout in the drum and with a closure lid cooperable with the open end of the drum. A mixing paddle can be provided for mixing sludge or slurry waste introduced into the drum with dry cement. A basket can be provided for supporting heavy solid waste in the drum. The baffle, paddle and basket are retained within the wastes introduced into the drum and form a part of the finished solid blocks.

Description

SPECIFICATION Improvements in container for encapsulating wastes The present invention concerns a container for the encapsulation of harmful waste products, in particular radioactive wastes.

According to the present invention a container for the encapsulation of waste products comprises a cylindrical drum open at one end, a false lid positioned within the open end of the drum and a closure lid cooperable with the open end of the drum.

The container is intended for the encapsulation of wastes, which can be solids, sludges or slurries, with cement, cement grout or any other encapsulatiny medium compatible with the drum and waste, whereby to form solid cylindrical blocks sutiable for subsequent storage or disposal. A mixing paddle can be provided for mixing sludge or slurry in the container with dry cement. Similarly, a basket can be provided for supporting heavy solid waste within the container. The false lid, paddle and basket are all "lost" within the container, that is, they remain within the wastes introduced into the container and form a part of the finished solid cylindrical block.

The invention will be described further, by way of example, with reference to the accompanying drawings; in which: Figure 1 is a vertical section through a container; Figure 2 is a detail of part encircled A in Figure 1; Figure 3 is a section through a lid for the container; Figure 4 is a section through one embodiment of a false lid; Figure 5 is a plan of another embodiment of a false lid; Figure 6 is an elevation of a paddle.

A container, as shown in Figure 1, comprises a drum having a base 1 having a peripheral flange 2 to which is welded a cylindrical wall 3. The wall 3 is formed from a rectangular metal sheet or plate welded at 4 to the flange 2 and welded along 5 at the abutting ends of the sheet. A shallow circular groove or channel 6 is formed in the base 1 and a boss or locator piece 7 is welded in position at the centre of the base 1. Rolling hoops 8 are formed in the wall 3 having a profile as shown in Figure 1. A pair of spaced apart, inwardly directed continuous ribs 9 and 10 are formed in the wall 3 adjacent the open end of the drum with the rib 9 extending inwardly beyond the rib 10 and as shown in detail A in Figure 2. A chime ring 11, formed from butt welded tube is conveniently welded to the open end of the drum to act as a stiffener.

A lid 12 (Figure 3) dimensioned to cooperate with the open end of the drum comprises a plate 13 having a peripheral lip 14. A cylindrical skirt 15 scalloped along the top edge, is welded to the underside of the lid 12 at a radius corresponding to the radius of the groove 6 in the base 1. The skirt 15 terminates in an inwardly directed flange 16.

The drum is intended to receive solid wastes or sludges. In the former case a grout is added to the solid waste in order to encapsulate the contents within the drum into a solid block. In the case of a sludge or slurry, dry cement is added to achieve solidification. Solid wastes, in particuiar large items can be supported by a basket within the drum.

For use with grout, the drum is provided with a false lid 18 as shown in Figure 4. The lid comprises an annular plate 19 having an upstanding peripheral lip 20 inclined outwardly at a small angle, for example 10 . An end of a vent or dip pipe 21 is welded to an aperture in the plate 19 and the opposite open end of the pipe 21 can be formed with short slots 22.

In use, the false lid 18 is located in the drum 1 and is supported by the ribs 9 and 10. The dimensions are such that the false lid rests on the larger rib 9 and the lip 20 engages the upper rib 10 such as to secure the lid in position. The vent or dip pipe extends downwardly towards the base of the drum leaving a narrow gap between the drum base and pipe to act as a coarse filter. Solid waste, which can be contained within a basket, is introduced into the drum. Thereafter grout is poured into the drum through the opening in the plate 19 of the false lid, the plate serving to reduce or prevent splash-back. The drum can be agitated to ensure that the grout effectively fills all cavities and gaps between the waste in the drum. Any water or other liquid in the drum can be drawn off through the vent pipe 21.The drum can initially be filled with the grout to a level just below the false lid 18.

After setting, further grout can be introduced to enveloped the false lid and to complete the filling of the drum. The lid 12 is located in position with the skirt 15 immersed in the grout. Upon setting of this further grout the lid 12 is anchored in place.

When the waste to be encapsulated is in the form of sludge or slurry the false lid 25 depicted in Figure 5 is employed in conjunction with a mixing paddle or stirrer 26 as shown in Figure 6. The lid 25 comprises a circular plate 27 having an upstanding peripheral lip 28 to engage between the ribs 9 and 10 on the rum in the same manner as the previously described false lid. Two segments 29, 30 are stamped out of the plate 27 to leave a web 31 extending across a diameter of the plate.

An aperture 32 is formed in the web at the centre of the lid.

The mixing paddle comprises a closed tubular stem 33 to exclude slurry, having paddle arms 34 carrying vanes 35 as shown in Figure 6.

Initially, the paddle 26 is positioned in the drum by locating the end of the stem 33 on the central locator or boss 7 in the base of the drum. Thereafter, the false lid 25 is located in position with the opposite end of the stem being supported by the central aperture 32 in the web 31. Sludge or slurry charged with dry cement is introduced into the drum through the segments in the lid and thoroughly mixed within the drum by means of the paddle. After mixing the contents are allowed to set and the drum is topped up with grout and lid ded with the lid shown in Figure 2 in the same way as described with reference to the encapsulation of solid wastes.

The drums when filled each form a solid block and the drums can be stacked. The rolling hoops are shaped such that the lower surfaces thereof which are substantially normal to the surface of the drum provide a lifting facility whereas the downwardly inclined upper surfaces provide a wash-down facility. The drum lids and paddle can be manufactured from stainless steel.

The drum is intended for the encapsulation of radioactive and like hazardous materials for subsequent storage, transport and disposal.

Claims

1. A container for the encapsulation of waste products comprising a cylindrical drum open at one end, a false lid positioned within the open end of the drum and a closure lid cooperable with the open end of the drum.

2. A container as claimed in claim 1 in which the false lid is provided with a peripheral lip dimensioned to engage between inwardly directed continuous ribs adjacent to the open end of the drum.

3. A container as claimed in claim 2 in which the false lid comprises an annular plate carrying a vent pipe.

4. A container as claimed in claim 2 in which the false lid comprises a circular plate having two segmentai portions stamped out of the plate to leave a diametral web.

5. A container as claimed in claim 4 including a mixing paddle cooperable with the false iid.

6. A container as claimed in any preceding claim in which the closure lid is provided with a cylindrical skirt welded to the underside thereof at a radius corresponding to the radius of a groove in the base of the drum.

7. A container for the encapsulation of waste products substantially as herein described with reference to and as illustrated in the accompanying drawings.