Hazardous or toxic waste destruction or containment – Destruction or containment of radioactive waste – By fixation in stable solid media
Patent
1997-03-05
1998-11-17
Mai, Ngoclan
Hazardous or toxic waste destruction or containment
Destruction or containment of radioactive waste
By fixation in stable solid media
588 18, 588252, 2041574, 422159, 4221863, G21F 900
Patent
active
058390782
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method and apparatus for processing waste materials particularly, though not exclusively, nuclear and other toxic waste materials such as heavy metal containing wastes.
The chemical industry in particular generates large volumes of toxic waste. The nuclear industry in comparison generates far lower volumes of waste but regulations demand even more rigorous treatment of such waste. The waste may be in the form of high level waste or low level waste. All of the waste produced by direct contamination with radio nuclides must either be stored or be processed in some manner to make it safe for storage for long periods of time. One of the methods for treating high level waste is that of vitrification into glass blocks. However, this method, practised by current methods has its own disadvantages in that yet further nuclear waste in the form of crucibles which are consumed during the melting operation is generated and which has to be dealt with. The current process is very effective in treating the waste but is very costly due to the fact that it is a chemical process carried out on highly radioactive material.
Other techniques for containing waste include encapsulation in concrete, and compaction and storage of low level waste such as tools, gloves and clothes for example.
A large proportion of the waste generated is during decommissioning of nuclear installations, such decommissioning becoming increasingly prevalent as nuclear power stations, for example, near the end of their useful lives. Therefore, it is a requirement throughout the world to find a vitrification process which does not produce or at least minimises the generation of so-called secondary waste (i.e. additional waste produced as a result of processing the primary nuclear waste).
It is an object of the present invention to provide a process for the direct vitrification of nuclear waste whilst minimising or eliminating the production secondary waste.
According to a first aspect of the present invention, there is provided a method of treating toxic waste by the vitrification thereof, the method comprising the steps of providing said waste in the form of relatively small pieces; bringing a high intensity light source to bear on said waste and said optional vitrifiable material; said high intensity light source being of sufficient power to cause melting and subsequent vitrification of said waste's and, cooling and storing said vitrified material.
Preferably, said high intensity light source comprises a broad band spectrum of frequencies.
Preferably, said broad band spectrum comprises continuous white light.
Preferably, said high intensity light source comprises a high intensity arc lamp. Such arc lamps are currently available in powers of up to 300 kW continuous optical power and in power densities of up to 2000 W/cm.sup.2.
Arc lamps have particular advantages in that they can be focused or defocused so as to control the power density applied and that the light brought to bear on the waste is spread over a relatively much greater area than, for example, a laser beam.
Further advantages of arc lamps include the fact that they are much more efficient at about 50' energy utilisation compared to 1% energy utilisation for lasers. The capital cost of arc lamps is much lower and they are more compact and much less cumbersome in ancillary equipment required for their operation.
Yet further advantages of arc lamps relate to the nature of the light employed in that white light contains a large proportion of ultra violet light (uv) which is a high energy, low heat light form particularly useful in breaking up potentially dangerous and toxic organic molecules into less harmful molecules due to the action of uv light on the chemical bonds. Therefore, white light generated for arc lamp melting of waste may be particularly useful for dealing with so-called mixed wastes containing such potentially harmful toxic organic chemicals. White light also comprises a significant proportion of infra red light (ir) which is a relatively high h
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Jennings Howard T.
Li Lin
British Nuclear Fuels PLC
Mai Ngoclan
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