Radiant energy – Radiation controlling means – Shielded receptacles for radioactive sources
Reexamination Certificate
2002-02-28
2003-10-28
Lee, John R. (Department: 2881)
Radiant energy
Radiation controlling means
Shielded receptacles for radioactive sources
C250S507100, C312S249800, C376S272000, C376S250000, C376S269000, C376S287000, C600S007000, C600S003000, C128S098100, C128S098100
Reexamination Certificate
active
06639236
ABSTRACT:
This application claims priority to Great Britain Application No. 9910998.5 filed on May 13, 1999 and International Application No. PCT/GB00/01831 filed on May 12, 2000 and published in English as International Publication Number WO 00/70624 on Nov. 23, 2000.
This invention relates to a radioactive material container.
In order to prevent radiation escaping from a receptacle containing a radioactive material, it is usual to wrap lead sheeting around the receptacle. This is then followed by binding the lead wrapped receptacle with adhesive plastic tape. This has the inherent disadvantages of making the receptacle heavy, bulky and difficult to handle and is susceptible to leaving gaps in the shielding through which radiation can escape. If the radioactive material is a liquid, then the conventional lead casing will not prevent the liquid from escaping from the receptacle/casing ensemble in the event that the receptacle should fail or break.
In accordance with the present invention a radioactive material container comprises a receptacle characterised in that a coating of lead and a further resilient layer cover a substantial proportion of the receptacle's exterior surface the lead being deposited by an electroplating process.
The lead may be directly coated on the surface of the receptacle. Coating of a sufficient surface area of the receptacle provides for the mitigation of escape of radiation from the container. The electroplating process provides for simple deposition of the required thickness of lead, which is adequately uniform across the surface area of the receptacle. This reduces the weight of the container, which is also consequently easier to handle. The lead may absorb some of the energy of any impulse that is experienced by the container (for example, if the container is dropped), thus decreasing the likelihood of breakage of the receptacle. However its primary function is to prevent or reduce to safe levels transmission of radiation outside of the container.
The lead has a mean thickness in the range 0.01-6 mm, with a preferred mean thickness of 1 to 6 mm. Most preferably the lead thickness is between 1 mm to 2 mm. This provides a sensible degree of protection whilst being reasonably easy to apply and adhere to the receptacle. Furthermore, this is sufficient to provide protection for the user of the container, while retaining lightness and ease of use.
In one embodiment, the receptacle is made of a plastics material. Plastics receptacles are lightweight, readily available and cheap. The plastics material is preferably chosen from one of high density poly(ethylene), poly(propylene), poly(methylpentene) and poly(tetrafluoroethylene).
In another embodiment, the receptacle is made of glass. This material is very strong and does not usually degrade when subjected to radiation.
In a further embodiment, the receptacle is made of a metal. Metals are generally strong, yet tough The metal is preferably aluminium, since this is lightweight.
The resilient layer is especially useful if the receptacle may be damaged by impact or other shock which might result in mechanical breakage of the receptacle and allow leakage of any materials contained therein. Such a layer is particularly advisable where the receptacle is made from glass or a similar fragile material which is easily shattered on impact. By applying a resilient layer the breakage can be prevented or any leakage postponed or reduced by the resilient layer. The resilient layer is preferably applied over the lead. The material of the resilient layer is preferably an epoxy resin. This forms a hard durable and slightly flexible protective barrier which contains the receptacle contents should the receptacle and the lead layer fail. A further advantage of using epoxy resin is its tendency to expand on contact with some radioactive materials thus acting as a warning if the integrity of the receptacle has been breached. This provides a period within which the material is still contained and enables remedial action to be taken for example, transfer to another container. Materials other than epoxy resin suitable for use in the invention will be apparent to those skilled in the art.
In one embodiment, in addition to the lead coating there is at least one further coating of cadmium and one further coating of copper both of which cover a substantial proportion of the exterior surface of the receptacle or the lead. Preferably the receptacle is first coated with at least one layer of cadmium and a layer of copper before the lead is applied. The cadmium and copper layers mitigate the egress of any X-rays. Preferably at least one additional layer of cadmium and an additional layer of copper is provided on top of the lead layer. This forms a sandwich with the lead in the middle. A resilient layer is then provided on top.
In one arrangement of the invention, a substantial proportion or the whole of the exterior surface of the receptacle or lead coating is coated with cadmium and copper layers.
In one embodiment, the cadmium and copper are deposited by an electroplating process, thus enabling all of the coating to be facilitated by electroplating. The electroplated cadmium and copper layers, may have a total range of thickness of between 0.01 and 1 mm.
The receptacle is chosen from one of a syringe, a bottle, a box or a canister.
REFERENCES:
patent: 5734169 (1998-03-01), Saidian
patent: 5748692 (1998-05-01), Burton
patent: 5949084 (1999-09-01), Schwartz
patent: WO 96/36972 (1996-05-01), None
Allen Martyn Charles
Awbery Roy Paul
Erskine Graham John
Low Colin Mark
Hashmi Zia R.
Kilpatrick & Stockton LLP
Lee John R.
Russell Dean W.
The Secretary of State for Defence
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