GB2060466A

GB2060466A - Nuclear Fuel Transport Flask

Info

Publication number: GB2060466A
Application number: GB8029791A
Authority: GB
Original assignee: British Nuclear Fuels Ltd
Current assignee: British Nuclear Fuels Ltd
Priority date: 1979-10-11
Filing date: 1980-09-15
Publication date: 1981-05-07
Also published as: GB2060466B

Abstract

A finned irradiated fuel container (1) has a shroud (3) around the fins (2). Slots are provided at the top and bottom of the shroud so that cooling by the convection flow of air around the fins can take place. The shroud (3) which is coated with high thermal emissivity paint (12) provides both protection from fire and mechanical strength. The container (1) may be rectangular (as shown) or cylindrical (Figs. 2 to 4, not shown). <IMAGE>

Description

SPECIFICATION Flasks This invention relates to flasks for transporting material, particularly but not exclusively irradiated nuclear fuel.

Irradiated nuclear fuel emits heat so that it is desirable that a transport flask be able to dissipate this heat. Since the flask may be exposed to heat from an external source, such as a fire, it is also desirable that the flask inhibit the ingress of heat from the external source to the irradiated fuel. Also, the flask should be able to withstand impacts.

An object of the present invention is to provide a flask which tends to meet these conflicting desiderata.

According to the present invention, a flask for transporting the material comprises a container for the material and a shroud for the container, a passage for air-flow being defined between the container and the shroud.

Preferably, the container is provided with fins.

An advantage of such a flask is that heat generated internally of the container tends to be dissipated by the fins and convective air-flow through the passage, whereas heat from an external source tends to be inhibited from reaching the container by the shroud.

Advantageously, the shroud is fabricated from metal, coated with high thermal emissivity paint.

Two embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a cutaway perspective view of a rectangular flask, Figure 2 is an incomplete perspective view of a cylindrical flask, Figure 3 is an incomplete side view of Figure 2, and Figure 4 is a horizontal section of the cylindrical flask of Figures 2 and 3 and including a modified trunnion fitting.

Reference is directed firstly to Figure 1, wherein a flask may be seen to include a container for irradiated nuclear fuel, generally indicated by 1. The container is provided with fins 2 around its sides. A shroud 3 is arranged around the side of the container 1, a gap being left between the fins 2 and shroud 3. The shroud 3 is attached to the container 1 via attachment points 4, which may be nuts and bolts. The shroud 3 contains holes 6 for trunnions 7 (only one of each being shown), so that the flask may be moved.

The container 1 has an upper lid 9 which may include an impact limiter. The base of the container 1 extends below the shroud 3, so that a gap 10 is provided around the base to allow ingress of cooling air flow 11 through a passage between the container and shroud. The shroud 3 may be painted with a high thermal emissivity paint 12 (only partly shown).

In use of the flask, heat from the contents of the container 1 is dissipated by convection, since air-flow 11 occurs through the gap 10, between the container and shroud around the fins 2 and out at the top of the flask. The cooling fins 2 aid transmission of heat from the container 1 into the air-flow. The shroud 3 is shaped so as to interfere with convective cooling as little as possible, such as by aerodynamic shaping of its leading and trailing edges.

If the flask is exposed to heat from an external source, such as a fire, the shroud 3 intercepts much of the radiant heat from the flames because although it increases in temperature, it radiates heat to the flask surface with much lower effective temperature than if it were not there.

The flames are inhibited from entering the space between the fins, which would otherwise be heated effectively by radiation. The shroud 3 also reduces convective heating because the flames are inhibited from entering the restriced flow area so that gases will cool rapidly by heat transfer to the flask.

Reference is now made to Figures 2, 3 ad 4 which show a cylindrical flask and wherein like reference numerals ta Figure 1 are used for like parts. A container for irradiated fuel is indicated by 21 and the container is provided with fins 22 around its sides. A shroud 23 (only partly shown in Figure 3) is disposed around the sides of the container 21, a gap being left between the fins 22 and the shroud 23. Impact limiters 25 are provided at one or both ends of the flask (only one end being shown).

A longitudinal slot 26 is provided in the base of the shroud 23 to allow ingress of cooling air and a longitudinal slot 27 is provided at the top of the shroud 23 to allow egress of the warm air. Airflow is indicated by arrows 29.

In Figure 4, attentIon is drawn to two alternative forms of attachment of the trunnion 7 to the left and to the right of the Figure, respectively. To the left is the form of trunnion mounting already described and to the right, a form wherein the shroud and fins are cut away to accommodate the trunnion. Also, the shroud is much closer to the fins to the right and in fact is only just clear, although this clearance cannot be seen in the figure.

In use, the cylindrical flask is similar to the rectangular flask in a fire situation. Flames come into contact with the container surface and fins over the area of the top and bottom slots, which are therefore made of minimum size, while allowing sufficient normal convective cooling. The area of direct contact is small in comparison with the whole area.

In some embodiments of the invention, the dimensions of the shroud may be reduced, for example, by having four non-contacting plates arranged over the finned area only of the rectangular flask.

It is to be noted that; temperature of accessible surfaces are reduced in normal operation, heating from isolation is reduced, external contamination of the flask is reduced because the shroud can be fitted after the container leaves contaminated areas, the shroud contributes to the mechanical strength and protection of the flask and there is freer choice of paint for the shroud since decontamination of the latter is not a problem.

From the above description, it can be seen that an improved flask is provided.

Claims

1. A flask for transporting material comprising a container for the material and a shroud for the container, a passage for air-flow being defined between the container and shroud.

2. A flask as claimed in Claim 1, in which the container is provided with fins.

3. A flask as claimed in Claim 1 or 2, in which the shroud is fabricated from metal coated with high thermal emissivity paint.

4. A flask as claimed in any preceeding claim, in which a slot is provided in the shroud whereby supporting trunnions for the flask may be reached externally.

5. A flask as claimed in Claim 1, 2 or 3, in which the shroud is cut away to accommodate a trunnion or carrying the flask.

6. A flask as claimed in Claim 5 when dependent upon Claim 2, in which the fins are cut away to accommodate the trunnion.

7. A flask substantially as hereinbefore described and as shown in Figure 1 of the accompanying drawings.

8. A flask substantially as hereinbefore described and as shown in Figures 2 to 4 of the accompanying drawings.