WO2003017287A2

WO2003017287A2 - Improvements in and relating to containment

Info

Publication number: WO2003017287A2
Application number: PCT/GB2002/003823
Authority: WO
Inventors: Ross Strachen Parker; Michael Bradley
Original assignee: Bnfl (Ip) Ltd
Priority date: 2001-08-20
Filing date: 2002-08-19
Publication date: 2003-02-27
Also published as: GB0120221D0; WO2003017287A3; AU2002321503A1

Abstract

A method of containing contaminating material, feed material handling apparatus and the use of feed material handling apparatus is provided with a view to minimising the possibilities for contaminating material spreading from a high contamination level environment to a low contamination level environment, the two environments being linked by a passage, at least part of the passage being filled with the feed material.

Description

IMPROVEMENTS IN AND RELATING TO CONTAINMENT

This invention is concerned with improvements in and relating to containment, particularly of radiation and / or radioactive materials, within an environment.

A large number of process steps are involved in nuclear fuel manufacture. Particularly where mixed oxide fuel is being produced, some of the steps involve higher levels of radiation than others. Appropriate containment of radioactive material in higher contamination environments needs to be provided to ensure that that contamination does not spread to lower contamination level environments. Minimising the number of higher contamination level environments reduces the costs of plant construction, difficulty of plant operation and the costs and difficulty of plant decommissioning. hi a number of situations within a process plant, material passes from a lower contamination level environment to a higher contamination level environment. Conventionally, such material may be brought in to the environment in bags so as to avoid contamination spreading from the higher contamination level environment to the lower contamination level environment. Such techniques represent an additional complexity in the system, however. Additionally there are potential blockage issues, this is particularly so with materials such as uranium dioxide, which in the powdered form used in nuclear fuel manufacture, has a large surface area and is hydrophilic, thus rendering it susceptible to the formation of clumps and hence process line blockage.

The present invention has amongst its aims the maintenance of containment between high and low contamination level environments. The present invention has amongst its aims the provision of a more reliable and / or less prone to blockage way of achieving containment.

According to a first aspect of the invention we provide a method of containing contaminating material within a first environment, the method including, for at least part of the time, feeding a feed material from a second environment to the first environment, the feed material passing from a feed location in the second environment to a dispensed location in the first environment, at least in part, along a passage and wherein at least a part of the passage is filled with the feed material. The contaminating material may be a radioactive contaminant, toxic contaminant or combination thereof. In particular the contaminating material may be plutonium and / or plutonium oxide and / or nuclear fission products.

The first environment may be a room, cell or glove box.

The method may pass feed material to the dispensed location as a batch process. In particular the method may pass the material to the dispensed location until a predetermined mass of feed material has been delivered to the dispensed location.

The second environment may be a room, cell or glove box.

Preferably the level of radiological or toxic contamination or anticipated contamination in the second environment is lower than in the first environment.

The feed location may include a hopper to which the feed material is initially delivered.

The dispensed location may include a container to which the feed material is delivered. The container may be weighed continuously or periodically during dispensing of the material. Preferably a load cell is used to weigh the container and dispensed material. A mechanism, preferably automated, may be provided for removing and / or replacing a lid of the container. The lid may be removed as the container is introduced to the dispensed location or with the container at the dispensed location or prior to introduction of the container to the dispensed location. The container maybe removed from the dispensed location to a further processing step after the feed material has been dispensed. The dispensed location may be provided within a glove box within the first environment and open thereto. The feed location may be provided within a glove box, for instance the same glove box as the dispensed location is provided within, but is preferably sealed with respect to the interior of that glove box save for the passage. Preferably the feed material is introduced to the feed location through the top of the glove box.

Preferably the feed material passes from the feed location along a passage and then drops, under the force of gravity, to the dispensed location, most preferably into a container. Preferably at least a portion of the passage is substantially horizontally provided. Substantially horizontal may mean an angle of less than 10° to the horizontal, more preferably less than 5° to the horizontal and ideally horizontal.

Preferably at least a part of the passage acts as a feed material mover. The feed material mover may be provided by vibrating part of the passageway, preferably in a manner which causes preferential advancement of the feed material towards the dispensed location. Preferably the feed material mover is provided in a substantially horizontal part of the passage. Substantially horizontal may mean an angle of less than 10° to the horizontal, more preferably less than 5° to the horizontal and ideally horizontal.

Preferably the part of the passage provided with the feed material mover contains a layer of feed material, but is not filled with feed material.

Preferably the part of the passage provided with the feed material mover is provided between the dispensed location and the part of the passage which is filled with the feed material.

The part of the passage which is filled with the feed material may include a substantially horizontal part of the passageway. Substantially horizontal may mean an angle of less than 10° to the horizontal, more preferably less than 5° to the horizontal and ideally horizontal. The part of the passageway which is filled with the feed material may include a substantially vertical part of the passageway. Substantially vertical may mean at an angle of less than 10° from the vertical, more preferably less than 5° from the vertical and ideally vertical. The part of the passageway which is filled with the feed material may include the lower part of a hopper or container. Preferably the hopper or container preferentially channels the feed material towards the passage leading towards the dispensed location. Ideally the part of the passage which is filled with feed material includes a substantially horizontal part of the passage, a substantially vertical part of the passage and the bottom portion of a hopper or container.

Preferably the part of the passage is filled with feed material such that when the feed material advances towards the dispensed location, the feed material advances throughout the entire cross section of the passage.

Preferably at least part of the passage is filled with the feed material all of the time, particularly all of the time between exposure of the first environment to the contaminating material until the decommissioning of the apparatus embodying the method and / or the decommissioning of the first environment.

Preferably the feed location is provided with a feed material amount detector. Preferably the feed material amount detector inhibits the operation of the feed material mover if the amount of feed material falls below or is below a predetermined amount. The predetermined amount may be a predetermined mass and / or level within the feed location.

Preferably the feed location includes a feed material amount detector which activates the addition of further feed material to the feed location if the amount of feed material in the feed location falls below a second predetermined amount. The second predetermined amount may be a mass or level. Preferably the second predetermined amount is higher than the first predetermined amount.

Preferably the feed location includes a feed material amount detector which inhibits the introduction of further feed material to the feed location if the amount of feed material in the feed location exceeds a predetermined third amount. The predetermined third amount may be a mass of feed material or a level of feed material. Preferably the third level is higher than the first and second predetermined amounts.

Preferably the further feed material is introduced to the feed location by a conveying unit, preferably a disc lift system. The conveying unit may be fed from an initial feed location. Preferably the initial feed location is lower than the feed location. Preferably the initial feed location is a hopper. Preferably the initial feed location is provided with an aperture through which the further feed material is introduced. Preferably the further feed material is provided in drums. Preferably the drums are emptied into the initial feed location.

The method may employ a plurality of feed locations and / or initial feed locations and / or conveyors and / or feed material movers and / or passageways to convey feed material to the dispensed location.

According to a second aspect of the invention we provide feed material handling apparatus, the apparatus including a feed location into which the feed material is introduced, a dispensed location to which the feed material is passed, the feed location and dispensed location, at least in part, being connected by a passage along which the feed material passes, the apparatus further including a feed material mover and a feed material amount detector monitoring at least a part of the passage, the feed material detector inhibiting the operation of the feed material mover if the amount of feed in the part of the passage way is below a predetermined amount. The second aspect of the invention may include any of the features, options or possibilities set out above in relation to the first aspect of the invention and / or any of the features, options or possibilities set out elsewhere in this document.

Various embodiments of the invention will now be described, by way of example only, and with reference to the accompanying drawing in which: -

Figure 1 schematically illustrates the process line for material passing from a lower contamination level environment to a higher contamination level environment.

One part of the process for producing mixed oxide nuclear fuels is the introduction of an uranium dioxide feed into the process plant and its measured introduction into the part of the plant containing the plutonium oxides together with which it will form the nuclear fuel product. Plutonium oxides generally represent a higher level of radiological contamination and chemical contamination than uranium dioxide. As a consequence plutonium oxides are handled in part of the process plant which should desirably be kept separate from the uranium dioxide only handling part of the plant.

To achieve this aim of separating the parts of the plant, whilst allowing ready transfer of the uranium dioxide into the relevant part of the plant and maintaining containment for the higher contamination level environment, the present invention uses the type of system illustrated in Figure 1.

In Figure 1 the containment wall 2a and glovebox partition wall 2b are provided to separate higher contamination level environment 4a/b from lower contamination level environment 6a/b is illustrated. The remainder of the containment barrier is generally provided by the superstructure of the building 8 and the glove box structure 10 which spans an opening in the wall 2.

Within environment 6a, generally a cell or room, drums of uranium dioxide 12 are introduced. The drums are manipulated into a discharge position, drum 12a, whereupon the uranium dioxide contained within them falls into hopper 14 (initial feed location). The hopper 14 contains the uranium dioxide 16 prior to its transfer into the glove box structure 10 by disc lift 18. The discharge of the uranium dioxide 16 from the hopper 14 by the disc lift 18 into hopper 22 is automated. Should the level drop below a predetermined level in hopper 14, then additional uranium dioxide 16 is introduced from further drums 12. This process is manually initiated. The level of material within hopper 14 is constantly monitored by level probe 20. The operator manually initiates introduction of UO² when sufficient space is available.

Material conveyed from the hopper 14 by the disc lift 18 is deposited in second hopper 22 (feed location) within the glove box structure 10. Once again a contact probe 24 is provided for the hopper 22 and this automatically stops the disc lift 18 should the hopper 22 become overfilled with uranium dioxide 16.

The hopper 22 funnels down to a pipe 26 which then leads into a horizontal pipe 28 part of which is set up as a vibrating feeder 30 (feed material mover). The vibration feeder 30, when activated, promotes movement of the uranium dioxide 16 along the vibrating feeder 30, pipe 28, pipe 26 and out of the hopper 22. The configuration of the pipes 26 and 28, however, and the level of material in the hopper 22 ensure that a mass of the uranium dioxide 16 always fully fills the initial part of the pipeline. To give optimum feeding of the uranium dioxide by the vibrating feeder 30, however, only a layer 34 of uranium dioxide material is present during that stage.

At the end of the pipe 36 the uranium dioxide 16 discharges into container 38 (dispensed location). An automated unit 40 is provided to remove the lid 42 of the container 38 once it is in the correct position, so as to allow filling. The container 38 is weighed using a load cell 44. The lid 42 is returned to the container 38 once the required amount of uranium dioxide 16 has been delivered. Prior to return of the lid 40 the vibrofeeder 30 is deactivated. In this filled state, the container 38 can pass on to the next part of the process.

Whilst a single hopper 14, disc lift 18, control hopper 22 and vibrofeeder 30 is illustrated in Figure 1 for simplicity sake, a plurality of such components could be provided in parallel to one another, potentially feeding a single container 38 or a plurality thereof. In this way blending of uranium dioxide 16 from different drums 12 can be effected if needed.

Throughout the dispensing of uranium dioxide 16 from the control hopper 22 to the container 38 the level of uranium dioxide 16 is monitored by probe 24a and once it falls below a predetermined level the disc lift is operated to introduce more uranium dioxide 16 to the control hopper 22. In general operation this is sufficient to maintain the level of uranium dioxide 16 in the hopper 22 at a level which maintains the uranium dioxide barrier 32. If for any reason uranium dioxide 16 cannot be introduced into the control hopper 22 in a way which maintains the level, then if the level falls below a further, lower, predetermined level probe 50, then the vibrating feeder 30 is deactivated and can only be reactivated once the level of uranium dioxide 16 within the hopper 22 climbs above a predetermined level. The system thus ensures that the hopper 22 and pipe portions 26 and 28 always have an uranium dioxide plug present within them to maintain containment and prevent the possibility of contamination spreading from the high contamination level environment 4 to the low contamination level environment 6. Additionally as no valves are involved, the risk of blockage or mechanical failure of the valves requiring a replacement is removed.

Claims

CLAIMS:

1. A method of containing contaminating material within a first environment, the method including, for at least part of the time, feeding a feed material, preferably uranium dioxides or uranium dioxide incorporating material, from a second environment to the first environment, the feed material passing from a feed location in the second environment to a dispensed location in the first environment, at least in part, along a passage and wherein at least a part of the passage is filled with the feed material.

2. A method according to claim 1 in which the feed location is provided with a feed material amount detector and the feed material amount detector inhibits the movement of the feed material from the second to the first environment if the amount of feed material falls below or is below a predetermined amount.

3. A method according to any preceding claim in which at least part of the passage is filled with the feed material all of the time between exposure of the first environment to the contaminating material until the decommissioning of the apparatus embodying the method and / or the decommissioning of the first environment.

4. A method according to any preceding claim in which the part of the passage provided with a feed material mover contains a layer of feed material, but is not filled with feed material.

5. A method according to any preceding claim in which the part of the passage which is filled with the feed material may include a substantially horizontal part of the passageway.

6. A method according to any preceding claim in which the part of the passageway which is filled with the feed material may include a substantially vertical part of the passageway.

7. A method according to any preceding claim in which the feed location includes a hopper to which the feed material is initially delivered.

8. A method according to claim 7 in which the part of the passageway which is filled with the feed material includes the lower part of a hopper or container.

9. A method according to any preceding claim in which the part of the passage is filled with feed material such that when the feed material advances towards the dispensed location, the feed material advances throughout the entire cross section of the passage.

10. A method according to any preceding claim in which the dispensed location includes a container to which the feed material is delivered, the container being weighed continuously or periodically during dispensing of the material.

11. A method according to any preceding claim in which the dispensed location is provided within a glove box within the first environment and open thereto.

12. A method according to any preceding claim in which the feed location is provided within the same glove box as the dispensed location is provided within, but is sealed with respect to the interior of that glove box save for the passage.

13. A method according to any preceding claim in which at least a part of the passage acts as a feed material mover, the feed material mover being provided by vibrating part of the passageway.

14. A method according to any preceding claim in which the feed location includes a feed material amount detector which activates the addition of further feed material to the feed location if the amount of feed material in the feed location falls below a second predetermined amount.

15. A method according to any preceding claim in which the feed location includes a feed material amount detector which inhibits the introduction of further feed material to the feed location if the amount of feed material in the feed location exceeds a predetermined third amount.

16. The use of feed material handling apparatus to prevent contamination passing from a high contamination level environment to a low contamination level environment, the apparatus including a feed location into which the feed material is introduced, the feed location being within the low contamination level environment, a dispensed location to which the feed material is passed, the dispensed location being within the high contamination level environment, the feed location and dispensed location, at least in part, being connected by a passage along which the feed material passes, the passage passing from the low contamination level environment to the high contamination level environment and wherein at least part of the passage is filled with the feed material.

17. Feed material handling apparatus, the apparatus including a feed location into which the feed material is introduced, a dispensed location to which the feed material is passed, the feed location and dispensed location, at least in part, being connected by a passage along which the feed material passes, the apparatus further including a feed material mover and a feed material amount detector monitoring at least a part of the passage, the feed material detector inhibiting the operation of the feed material mover if the amount of feed in the part of the passage way is below a predetermined amount.