System for posting articles into a containment

Abstract: A sphincter seal (3) to accommodate variations in diameters of drums (15)(17), is employed at a posting port into a containment (1). The seal comprises an annular assembly of inner and outer brush seals (3) between which are sandwiched rings of resilient material. An elastic garter is secured to the resilient rings to resist deformation of the rings through use.

Description: The present invention concerns a port for posting articles into a containment which is maintained at sub-atmospheric pressure. In particular the invention concerns a posting port having a sphincter seal for minimising back diffusion through the port during a posting operation. Systems for posting articles into a containment by means of a posting port having a sphincter seal are known. One such system is described in FR-A-2,049,259 which discloses a means of providing a leaktight connection between the rear of a goods vehicle and an access opening in a building. The access opening is fitted with a removable door and had three flaps of an elastically resilient material which engage the top and sides of the goods vehicle as it passes through the opening, thereby forming a leaktight connection between the vehicle and the interior of the building. The prior art construction is not suitable for use with radioactive wastes. It is an object of the present invention to provide a construction that is so suitable. The present invention accordingly provides a system for posting articles into a containment maintained at sub-atmospheric pressure, comprising a posting port in a wall of the containment having a sphincter seal and a removable lid, the sphincter seal being such as to engage articles posted through the port and to permit an inward air flow into the containment to oppose back-diffusion from the containment, characterised in that the sphincter seal comprises an annular assembly of inner and outer brush seals between which are sandwiched rings of resilient material having a continuous elastic garter secured to the underside thereof. Preferably, each ring of resilient material is divided into sectors which extend radially inwardly beyond the inner radius of the brush seals. The upper annular brushes of the assembly serve to protect the resilient member during the posting operation. The lower annular brushes serve to support the resilient member and help prevent permanent deformation. Both upper and lower brushes restrict the opening in the containment during posting operations. The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figures 1 to 8 depict diagrammatically successive steps in the posting of waste drums into a containment; and Figs 9 and 10 are respectively a plan and section of a sphincter seal used at a posting port into the containment. In Figures 1 to 8, a containment 1 is provided with a posting port 2 through which drums of radioactive waste materials can enter into the containment. The port 2 comprises an annular sphincter seal 3 and a removable lid or cover 4. The lid or cover 4 sealingly engages an inflatable seal 5 mounted in a lip 6 at the outer end of the port 2. Various detectors for controlling the sequence of operation are denoted by the reference numerals 7 to 11 respectively and the function of which will be described in the following description. A platform comprising a roller conveyor assembly 12 is located within the containment 1 below the port 2. A hoist 14 in the form of a fork cooperates with the conveyor assembly 12 such that the fork can pass between rollers 13 of the conveyor assembly. In Figure 1 the hoist is shown in a retracted position. To enter a first drum into the containment, the hoist 14 is raised to its highest position, which will be indicated by position switch 10, the lid or cover 4 is removed to expose the port 2, and a drum 15 supported by a crane or hoist (not shown) is lowered through the port on to the raised hoist 14. This position is depicted in Figure 2. The sphincter seal 3 engages the lower end of the drum 15. The detectors 7,8 and 9 can be infra-red switch devices and in Figure 2 the drum interrupts signals from transmitters to receivers at the detection positions. With the drum 15 on the hoist 14, the hoist is then lowered to lower the drum 15 into the containment until the drum lid 16 is level with or just below the lip 6 as shown in Figure 3. This is indicated by the detector 8 which initiates a signal to interrupt the hoist drive mechanism. The sphincter seal 3 remains at all times in engagement with the drum 15. During normal operation, a drum is always present in the port. This condition is only changed either at commencement of operation or if it becomes necessary to change and renew the sphincter seal. During normal operation a second drum 17, Figure 4, is then lowered by the external crane or hoist to above the drum 15. The drum 17 on breaking the signal at the detector 7 initiates a signal to recommence the hoist drive mechanism. The hoist 14 retracts to lower the drum 15 on to the roller conveyor assembly 12 and the fully withdrawn position of the hoist is indicated by a signal from detector 11 which stops the hoist drive mechanism. The drum 17, still supported by the external crane or hoist is at the same time lowered into the containment 1 and stops when the top of the drum 15 clears the detector 9. This position is shown in Figure 5. The sphincter seal 3 is now in engagement with the surface of the drum 17. In Figure 6, the drum 17 is supported in the port by the external crane or hoist and the first drum 15 is moved off the roller conveyor assembly 12 and through an airlock door (not shown) into a work area within the containment. Thereafter, the airlock door is closed and the hoist 14 is raised again to its highest position as indicated by the detector 10. The drum 17 is lowered on to the hoist 14 and released from the external crane or hoist. This position is shown in Figure 7. The drum 17 is then lowered on the hoist until the detector 8 is again actuated. The lid 4 can then be closed to form a secondary seal arrangement (Figure 8). The drum 17 remains in this position, with the lid closed, until a further drum is ready for transfer through the port into the containment. The lid 4 is then reopened to allow the posting operation to take place. The sequence of operation is then repeated with the drums 17 and the further drum to be entered into the containment. The sphincter seal serves to reduce the opening between the interior of the containment and the atmosphere during posting operations such that the containment ventilation system can maintain an inward linear air flow, typically 1m/sec, thus preventing back diffusion of airborne contamination from the containment. The form of sphincter seal is shown in Figures 9 and 10. The seal 3 is an annular assembly comprising upper and lower brush seals 20 and 21, conveniently nylon brushes, between which are sandwiched rings of natural or synthetic rubber 22, each ring being divided into sectors. The rubber rings extend radially inwardly beyond the inner radius of the nylon brushes. A continuous elastic garter 23 is secured to the underside of the lowermost ring 22 projecting inwardly beyond the lower brush. As a drum is passed through the port the sphincter seal is deformed as indicated in Figures 1 to 8 but at all times maintains a positive contact with the drum over the periphery of the drum. The seal can accommodate changes in diameter of individual drums and also different sizes of drums. The garter 23 serves to resist deformation of the seal during use and ensures that the seal returns to its natural state after passage of a drum through the port.

Claims: A system for posting articles into a containment maintained at sub-atmospheric pressure, comprising a posting port (2) in a wall of the containment (1) having a sphincter seal (3) and a removable lid (4), the sphincter seal (3) being such as to engage articles posted through the port (2) and to permit an inward air flow into the containment (1) to oppose back-diffusion from the containment (1), characterised in that the sphincter seal (3) comprises an annular assembly of inner (21) and outer (20) brush seals between which are sandwiched rings of resilient material (22) having a continuous elastic garter (23) secured to the underside thereof. A system as claimed in Claim 1, wherein each ring of resilient material (22) is divided into sectors which extend radially inwardly beyond the inner radius of the brush seals (20,21).

Inventors: CRITCHLEY RICHARD JEROME, OLDHAM SAMUEL ROY, CRITCHLEY, RICHARD JEROME, OLDHAM, SAMUEL ROY
Applicants: BRITISH NUCLEAR FUELS PLC
Application year: 1988
Main classification: G21F7
IPC codes: G21F9, G21F7