WO1996004660A1

WO1996004660A1 - Drums for the containment and storage of radioactive material

Info

Publication number: WO1996004660A1
Application number: PCT/GB1995/001740
Authority: WO
Inventors: Michael Joseph Burton; Alex Young
Original assignee: British Nuclear Fuels Plc
Priority date: 1994-07-29
Filing date: 1995-07-24
Publication date: 1996-02-15
Also published as: GB9415389D0

Abstract

A drum (1) for the sealed containment and storage of radioactive material, e.g. UO3 powder, has a top portion which comprises an outwardly projecting filling neck (17) through which radioactive material may be applied and which has a lip or scroll (21) at its upper end to facilitate receipt of a cap (29) to seal the radioactive material inside the drum. The filling neck of the drum may have a lip or scroll at its upper end which projects outwardly with respect to the axis of the neck. The drum (1) may have a cap (29) or lid to fit over the mouth of the neck to seal material inside the drum. The cap or lid (29) desirably fits over the said lip or scroll. The cap or lid may comprise a tubular portion closed at one end (35), a skirt (37) being provided attached to the other end, the junction (39) between the tubular portion and the skirt being of curved cross section. The inner surface of the curved portion of the cap or lid may in use be compressed onto the lip or scroll of the drum neck to provide hermetic sealing. The curved portion may have an inner surface which carries an elastomeric ring (41) which facilitates compression of the cap or lid onto the lip or scroll of the drum neck.

Description

Drums for the containment and storage of radioactive material

The present invention relates to drums for the containment and storage of radioactive material.

The purpose of the present invention is to provide a drum in which radioactive material, especially powder such as uranium trioxide, can be safely stored and transported around the world.

Such a drum needs to satisfy amongst other things safety standards as set by the International Atomic Energy Agency (IAEA) .

According to the present invention there is provided a drum for the sealed containment and storage of radioactive material, the drum having a top portion which comprises an outwardly projecting filling neck through which radioactive material may be applied and which has a lip or scroll at its upper end to facilitate receipt of a cap to seal the radioactive material inside the drum.

The filling neck of the drum may have a lip or scroll at its upper end which projects outwardly with respect to the axis of the neck. A .cap or lid may be provided additionally to fit over the mouth of the neck to seal material inside the drum. The cap or lid may fit over the said lip or scroll. The cap or lid may comprise a tubular portion closed at one end, a skirt being provided attached to the other end, the junction between the tubular portion and the skirt being of curved, eg substantially U-shaped, cross-section. The inner surface of the curved portion may in use be compressed onto the lip or scroll of the drum neck to provide hermetic sealing. The inner surface of the curved portion may include a sealing gasket, eg an elastomeric ring. The said skirt may also be crimped onto the underside of the lip or scroll, eg at a number of equispaced regions around the circumference of the skirt.

The lid or cap of the drum may have regions of different reflectivity to provide a recognisable target for an optical detection system as described in a UK Patent Application 9415300.3 (equivalent to a PCT Application of even date) by the present Applicants.

There may be a collar provided around the filling neck the collar having an engagement means which allows the drum to be picked up by a lifting means.

The said engagement means may be an inward facing rim or lip on the collar, the underside of which rim or lip provides an annular surface against which a lifting means such as a single, multiple or annular hook device can engage to provide a lifting action.

Desirably, the drum has a body inside which material is to be stored and, provided beneath the base of the body, a ring or skirt which provides a cylindrical cavity beneath the body. Desirably, the cylindrical cavity has a size such that the collar of an identical drum fits closely inside the ring or skirt whereby a plurality of identical drums may be stacked one on top of another to minimise the space in drum storage facility, occupied by such drums. The collar may have an upwardly projecting inwardly sloping surface having the said lip or rim forming a curved surface at its upper end to facilitate fitting the ring or skirt of one drum over the collar of another drum so as to provide stacking of such drums. Although the said ring or skirt is primarily provided for drum stacking purposes, it also provides stiffness and protects the base of the drum against impact damage.

The collar of the drum may have one or more holes to facilitate drainage of water, eg rainwater, which might otherwise collect in the annular space between the collar and neck of the drum.

The drum may be transported in an overpack as described in UK patent application no. 9415373.1 (equivalent to another PCT Application of even date) by the present Applicants. Such an overpack comprises a lightweight insulating packing material fitted all around the outer surfaces of the drum and its lid, the insulating packing material being contained in an outer container, eg made of steel or other high strength material. The outer container may have one or more folds, eg ribs or swages, which provide enhanced radial stiffness or strength

Advantageously, the outer container may have plugs fitted therein at the said fold(s) to permit venting to the outside atmosphere. The plugs may be designed to be blown to provide venting at a given pressure and/or temperature to the outside atmosphere.

The packing material may comprise a hollow body of packing material and a lid of packing material. The body and lid may have chamfered mating surfaces so as to minimise loss of insulation at the body/lid interface. The interface may in transverse cross-section extend along a slope, eg at 45°, to the axis of the packing material body. Thus, the lower surface and body mating surface of the lid may have a frusto-conical shape whilst the lid mating surface of the body provides an upward sloping ring shape.

The said lightweight packing material may comprise cork. Beneficially, cork is a lightweight porous material which has excellent impact absorption and insulation properties. Additionally, cork chars when it is in contact with a flame and the charring will prevent the drum and its contents from overheating, eg if the drum and overpack where in an environment exposed to a fire.

The said overpack allows a drum containing a radioactive material, eg powder, to be transported safely around the world. The overpack affords suitable protection to the drum against drop, fire and heat and also provides a degree of shielding from radiation emitted by the contents of the drum.

The drum according to the present invention together with the overpack described above provide a package which is suitable to satisfy Type ~AF' regulations of the IAEA. In particular, the drum provides a simple, easy to manufacture design which facilitates remote handling in an automatically operated plant or store. The drum may be employed to store radioactive powder such as U0₃. The drum may be filled with minimum loss of radioactive powder to the surroundings. The drum facilitates stacking in a stable manner which can resist seismic disturbances in a manner which minimises space occupied in a drum store. The drum may be manufactured in a form suitable for storage of powders for many years without corrosion eg by using stainless steel, the body having inherent strength. The filling neck of the drum may be sealed in an automated handling process by a cap which provides an effective seal preventing leakage of material contained therein or ingress of atmospheric gas or moisture.

The said neck of the drum may project from the top of the body of the drum to which the said collar is attached, eg by welding. The top may have ridges to add strength. The said collar may be attached to the top at an outer one of the said ridges. An identification number or code may be marked on the top of the drum, eg by stamping or laser engraving, which identifies the drum and its contents.

Various drum and cap configurations have been used in the prior art for the storage of containment of materials, but those which have been used for radioactive materials are different from the drum of the present invention and those which have been used for non-radioactive materials would not be suitable to satisfy the stringent regulations mentioned above.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which

Figure 1 is a cross-sectional side elevation of a drum embodying the present invention.

Figure 2 is a cross-sectional side elevation of a cap suitable for the drum as shown in Figure 1. Figure 3 is a cross-sectional side elevation of a drum as shown in Figure 1 having another similar drum stacked on top of it.

Figure 4 is a cross-sectional side elevation of a drum as shown in Figure 1 being lifted.

Figure 5 is a cross-sectional side elevation of an outerpack for the drum shown in Figure 1. As shown in Figure 1 a drum 1 is suitable for the safe containment and transport of UO3 powder which may be a recycled product obtained from the reprocessing of spent nuclear fuel. The drum 1 is of generally cylindrical shape with swages 5, 7 to provide added body strength. The body 3 has a base 9 which is concave as viewed from the outside. A ring shaped skirt 11 projects downwardly from the lower end 10 of the outer surface of the body 3 to provide an upturned basin shaped cavity 13 beneath the base 9.

At its upper end the drum 1 has an annular top 15 from which an annular neck 17 projects upwardly. The neck 17 provides a filling mouth 19 shown in brackets in Figure 1 because it is closed by a cap 29 described below. The neck 17 has at its upper end an outwardly projecting overturned or scrolled lip 21. A collar 23 projects upwardly from the periphery of the top 15. The collar has an inwardly sloping portion 23a which terminates at its upper end in an overturned lip 25. A hole 27 is provided in the collar 23 to allow rainwater collecting in the region inside the collar 23 between the neck 17 and the collar 23 to be drained. The top 15 has ridges 15a, 15b and 15c to add strength. The ridge 15c also facilitates attachment, eg by welding of the collar 23 on the top 15.

A cap 29 is employed to seal the filling mouth 19 of the neck 17. The cap 29 is shown before application in Figure 2. The cap 29 comprises a tubular body 31 having a chamfered ring 33 and plate 35 at its lower end. A skirt 37 is formed around the body 31, the skirt 37 being attached to the body 31 by an annular portion 39 of U- shaped cross-section. An elastomer sealing gasket or ring 41 is provided on the inner surface of the portion 39.

In use, the drum 1 is filled with powder, eg U0₃ powder, by an automatic filling machine which delivers the powder through the filling mouth of the neck 17. The cap 29 is then placed loosely on the drum 1, the body 31 being placed in the mouth 19 of the neck 17. The drum 1 and loosely fitted cap 29 are then offered to a capping device (not shown) . This may have a series of jaws evenly spaced around a circular locus around the skirt 37 of the cap 29. The capping device compresses the cap 29 onto the lip and crimps the skirt 37 around the underside of the lip 21 at the positions of the jaws. Figure 1 shows the cap 29 after attachment.

After sealing of the drum 1 by the cap 29 the drum 1 may be stored in a stack of drums. Figure 3 illustrates how such a stack is formed. In Figure 3 the drum 1 as shown in Figure 1 has a further identical drum la stacked on top of it. The drum la has a skirt 11a and cavity 13a identical to the skirt 11 and cavity 13 respectively of the drum 1. The skirt 11a of the drum la provides a close fit over the collar 23 of the drum 1, and the base 9 in its region 10a outside its concave region (forming the cavity 13) of the drum la thereby is supported by the drum 1 at the upturned portion of the collar 23 between the sloping portion 23a and rim 25.

Figure 4 illustrates how the drum 1 may be lifted to facilitate automatic handling and stacking. A lifting device 63 comprises a series of lifting arms 65 suspended from a beam 68. The arms 65 are lowered into the space above the top 15 of the drum 1 between the collar 23 and neck 17. The arms 65 have hands 67 which are located to engage beneath the rim 25. The hands 67 may be pushed inward toward the central axis of the device 63 to clear the rim 25 during lowering of the hands 67 and then pushed outward (eg by spring mechanisms not shown) to engage the rim 25 when beneath the rim 25. Lifting of the drum is then achieved by lifting of the arms 65.

Figure 5 shows an overpack for transport of the drum 1. The drum 1 is shown in phantom outline D. The overpack comprises an outer container 40 containing an inner hollow body 42 of lightweight insulation packing material. The body 42 has a cavity 44 into which the drum 1 is fitted. A cap 43 formed of the same packing material is fitted on top of the body 42. The cap 43 and the body 42 have mating surfaces 58 at an angle of 45 degrees to the axis of the body 42 to minimise heat transfer across the interface between the cap 43 and body 42. The cap 43 is covered by a plate 45 bonded to the cap 43, the plate 45 having a flange 45a which is fixed to the top of the container 40 by bolts 47 provided at various locations around the circumference of the flange 45a.

The overpack shown in Figure 4 protects the drum 1 from heat from external sources. The container 40 has two portions 49 of increased internal diameter primarily to provide radial stiffness and strength. Fusible plugs 53 are provided in the wall of the portions 49. The plugs 53 are designed to be blown at a predetermined gas pressure and/or temperature to allow the built up gas pressure to be released to the outside atmosphere.

The container 40 has a ring or chimb 55 at its lower end formed by folding the edge of the base 40a around the lower edge of the side wall 40b of the container 40 and welding the two, so that the ring or chimb 55 has a thickness three times the thickness of the base 40a and side wall 40b. The ring or chimb 55 protects the base 40a and the lower part of the side wall 40b of the container 40 from damage by impact by suspending it from the floor (not shown) .

Claims

1. A drum for the sealed containment and storage of radioactive material, the drum having a top portion which comprises an outwardly projecting filling neck through which radioactive material may be applied and which has a lip or scroll at its upper end to facilitate receipt of a cap to seal the radioactive material inside the drum.

2. A drum as in Claim 1 and wherein the filling neck of the drum has a lip or scroll at its upper end which projects outwardly with respect to the axis of the neck.

3. A drum as in Claim 1 or 2 and which has a cap or lid to fit over the mouth of the neck to seal material inside the drum.

4. A drum as in Claim 3 and wherein the cap or lid fits over the said lip or scroll.

5. A drum as in Claim 4 and wherein the cap or lid comprises a tubular portion closed at one end, a skirt being provided attached to the other end, the junction between the tubular portion and the skirt being of curved cross-section.

6. A drum as in Claim 5 and wherein the inner surface of the curved portion of the cap or lid is in use compressed onto the lip or scroll of the drum neck to provide hermetic sealing.

7. A drum as in Claim 5 or Claim 6 and wherein the curved portion has an inner surface which carries an elastomeric ring which facilitates compression of the cap or lid onto the lip or scroll of the drum neck.

8. A drum as in Claim 5, 6 or 7 and wherein the said skirt of the cap of lid is in use crimped onto the underside or the lip or scroll of the drum neck.

9. A drum as in Claim 8 and wherein the crimping is at a plurality of equispaced regions around the circumference of the skirt of the cap or lid.

10. A drum as in any one of the preceding claims and which is for the containment and storage of radioactive powder.

11. A drum as in Claim 10 and wherein the said powder is O3 powder.