Cleaning and liquid contact with solids – Processes – Using sequentially applied treating agents
Patent
1998-07-30
2000-09-12
El-Arini, Zeinab
Cleaning and liquid contact with solids
Processes
Using sequentially applied treating agents
134 26, 134 32, 134 33, 134121, B08B 304, B08B 306, B08B 308
Patent
active
061172480
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method and apparatus for cleaning radioactively contaminated material. In particular, but not exclusively, the invention relates to the cleaning of radioactively contaminated filter media containing a glass component in order to render the media suitable for disposal.
BACKGROUND OF THE INVENTION
Before consignment of radioactively contaminated material to a waste disposal facility, for example, a waste landfill site, the contamination on the material must be reduced to below the specified disposal limits of the facility. It is therefore necessary to treat certain materials before disposal in order to ensure that the contamination levels are within the disposal limits.
One known method of treatment includes incineration of the materials. However, a problem has arisen particularly regarding the incineration of used filter media made of or including borosilicate glass fibres contaminated with uranium. Filters having filter media of this type, for example, High Efficiency Particulate Air (HEPA) filters, are used in ventilation systems installed in nuclear fuel processing facilities. The presence of the borosilicate glass fibres results in the encapsulation of uranium during incineration, making it difficult to leach out the uranium from the incinerated product.
It is an object of this invention to provide a method and apparatus for cleaning radioactively contaminated material whereby said material is decontaminated sufficiently to allow safe disposal thereof. It is a particular object of this invention to treat a radioactively contaminated filter medium made of or including glass fibres to render the medium suitable for safe disposal.
BRIEF SUMMARY OF THE INVENTION
According to the invention there is provided a method of cleaning a material contaminated with radioactive substances, the method comprising the steps of inserting said material into a container having one or more apertures, placing the container and the material into a rotatable vessel having one or more apertures, subjecting the material to a leaching cycle comprising supplying a leaching liquid to the inside of said vessel and rotating said vessel whereby said leaching liquid mixes with the contaminated material to dissolve the radioactive substances, terminating the rotation of said vessel and discharging the leaching liquid therefrom, and then subjecting the material to a washing cycle comprising supplying a washing liquid to the inside of the vessel and rotating said vessel to enable the washing liquid to mix with the material, terminating the rotation of the vessel and then discharging the washing material therefrom.
Preferably the material is subjected to at least one further washing cycle.
The material may be subjected to three washing cycles.
Advantageously, the method further includes the step of subjecting the material to a spin-drying operation after discharging the washing liquid from the vessel, comprising rotating the vessel so as to subject the material to a centrifugal force whereby excess liquid is ejected from the material.
A spin-drying operation may be carried out after discharging the leaching liquid from the vessel.
The contaminated material preferably comprises a filter medium which includes a glass component.
The material to be cleaned may be contaminated with radioactive uranium substances.
Preferably the leaching liquid comprises nitric acid and the washing liquid is preferably water.
According to a further aspect of the invention there is provided apparatus for cleaning radioactively contaminated material, said apparatus comprising a container having one or more apertures for receiving said material, a vessel having one or more apertures in which the container containing the material can be placed, drive means for rotating the vessel, means for supplying a leaching liquid to the interior of the vessel and means for supplying a washing liquid to the interior of the vessel.
Preferably the container for receiving the material is permeable.
Advantageously, the container comprises a pe
REFERENCES:
patent: 5434332 (1995-07-01), Cash
Database WPI Week 9117, Derwent Publications Ltd., London, GB & JP 03 063 599, Mar. 19, 1991.
Docrat Ismail Tahera
Greenwood Howard
Rushton Alan
British Nuclear Fuels PLC
El-Arini Zeinab
LandOfFree
Cleaning radioactively contaminated material does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cleaning radioactively contaminated material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cleaning radioactively contaminated material will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-92234