Chemistry: electrical and wave energy – Processes and products – Electrostatic field or electrical discharge
Reexamination Certificate
1998-12-21
2001-07-31
Gorgos, Kathryn (Department: 1741)
Chemistry: electrical and wave energy
Processes and products
Electrostatic field or electrical discharge
C204S157200, C422S186000
Reexamination Certificate
active
06267850
ABSTRACT:
This invention concerns improvements in and relating to processing, particularly, but not exclusively to the processing of nuclear fuel materials and materials involved in the nuclear fuel industry.
The production and recycling of fuel grade nuclear fuel and associated materials involve long and complex processes. For instance, starting from mined uranium ore, in general terms the process involves taking the ex-mine grade material and gradually converting and enriching it until it is in a form and of a grade suitable for producing fuel pellets.
Intermediate stages in the overall process route form the starting point for the production of a variety of other materials too.
The basic stages in the overall process are the concentration of the initial uranium oxides as uranyl nitrate hexahydrate; a de-nitration stage to convert the material into UO
3
; a reduction stage to convert the UO
3
to UO
2
; a hydro-fluorination stage to form UF
4
; a further fluorination stage to produce UF
6
; an enrichment procedure by physical or chemical means; and the conversion of UF
6
in its enriched form to ceramic grade UO
2
which is in a suitable form to be formed into fuel pellets.
Recycling of spent fuel similarly involves a series of complex chemical and physical steps to separate the various fission products from the depleted fuel and to upgrade the 235U concentration in the material to a stage where once again it can be employed as fuel by separating out other components present in the used fuel.
The complexities of these processes are also present in other production processing lines involved in or relating to fuel cycles, such as thorium, plutonium and gadolinium amongst other materials. The production of uranium metal, non-enriched, for instance for use in Magnox reactors, also involves complex processing.
Extensive or involved processing is also encountered in the production of other materials outside the immediate nuclear fuel field. For example, the commonly employed production route for titanium, niobium and rhodium metal, amongst others, involves the rendering of the metal containing compounds into an halide form followed by its decomposition from the halide form to the metal.
Substantial processing plants, in terms of their size, capital investment and running costs, are necessary to perform the stages involved in all of these processes. Attendant problems also follow from the various processes and their requirements. For instance, processes involving fluorination involve a complex and hazardous electrolysis process to produce the fluorine required.
The present invention aims to provide an alternative processing route for many processes and/or a process for rendering materials into more useful forms and/or a process for recycling materials, together with apparatus for achieving the processes.
According to a first aspect of the invention we provide a process comprising the steps of:
a) providing a feed, the feed consisting of mixed components;
b) converting said feed into a plasma or ionised form;
c) providing at least one component in at least partially ionised form and at least one different component in at least partially non-ionised form;
d) containing said plasma/ions in a magnetic field; and
e) separating said ionised components from said non-ionised components.
The component desired may be extracted from a mixture of isotopes and/or elements of both metal and non-metal nature. The separation may be complete or partial.
The provision of the feed in a nitrogen containing compound is envisaged, but provision of the feed in a fluorine containing form is particularly preferred. Feed material consisting of uranyl nitrate, uranium hexafluoride, plutonium nitrate, thorium nitrate, depleted uranyl nitrate, depleted uranium hexafluoride or mixtures thereof all represent suitable feed materials. Other suitable feed materials include spent nuclear fuel, uranium tetrafluoride and other metals in halide forms, such as titanium tetrachloride. These materials may be in hydrated form.
The mixed components may consist of two or more different elements; two or more different isotopes of the same element; different elements together with different isotopes of one or more of those elements; or compounds and/or mixtures of compounds incorporating different elements, different isotopes or different isotopes and different elements, and reference in this application to the term components should be taken to include all such possibilities, amongst others, unless stated to the contrary.
The feed may be introduced to the magnetic field as a gas, liquid, solid or mixture of states. A gas feed to the magnetic field is preferred.
The feed may be introduced to the plasma generation means as a gas, liquid, solid or mixture of states.
The feed may be introduced to the ionisation means as a gas, liquid, solid or mixture of states. A gas feed to the ionisation means is preferred, particularly where a plasma generator is not also provided.
The feed may be provided in gaseous form by boiling and/or evaporation and/or sublimation of a solid or liquid initial feed. The conversion to gaseous state may be effected by a furnace, microwave heater or other form of heater means. Preferably the gas is introduced prior to ionisation.
Preferably all, or substantially all, of a given component is ionised. Preferably all, or substantially all, of a given component is not ionised.
Preferably some or all metallic elements present in said feed are lonised. The ionisation of metallic elements with an atomic weight greater than 90 is particularly preferred. Preferably some or all non-metallic elements in said feed are not ionised. Preferably all elements with an atomic weight below 90, most preferably below, 70 and ideally below 60, are left in non-ionised form. It is particularly preferred that elements such as uranium and/or plutonium and/or thorium and/or gadolinium are ionised. It is preferred that elements such as hydrogen and/or fluorine and/or oxygen and/or nitrogen are not ionised. Preferably boron is not ionised. Preferably fission products are not ionised.
The ionisation of the components may be caused by the temperature of the plasma. Additionally or alternatively the ionisation of the components may be caused by the interaction of the components with high energy electrons produced by electron cyclotron resonance.
The extent of ionisation and/or components ionised may be controlled by the energy input of and/or residence time in the electron cyclotron resonance unit.
Preferably the ionisation is controlled by the level of energy input. The level of energy input may be controlled by controlling the temperature of the plasma. Preferably the energy input is not selective between components of the feed. In this way all of the components of the feed are preferably raised to the same energy level. Preferably the ionised and non-ionised feed components are in equilibrium with one another for the prevailing conditions.
The feed material may be converted to a gas and fed to an ECR unit for ionisation. A furnace heater or evaporator may be used to convert the solid or liquid feed to gaseous/vapour form.
In a particular embodiment, therefore, the plasma may convert the feed materials to discrete atoms and electron cyclotron resonance may subsequently give rise to at least partial ionisation, preferably of a selective nature.
The feed may be provided in molecular form and be converted to discrete atoms and/or elemental forms by the plasma generation and/or ionisation means and/or heating means. The conversion to discrete atoms and/or elemental forms may give rise to partial ionisation of one or more of the resulting species. Thus a uranyl nitrate hexahydrate feed may be converted to U, N and H (discrete atomic forms), together with N2 and O2 (elemental forms), as well as U+ (ionised species). Preferably the feed is provided in molecular form and selectively separated as discrete atoms and/or elemental forms from ionised discrete atomic forms and/or elemental forms. This renders the technique applicable to a wider variety of
Bailey Geoffrey Horrocks
Gilchrist Paul
Webster Duncan Alfred
Whitehead Colin
British Nuclear Fuel plc
Gorgos Kathryn
Nicolas Wesley A.
Workman & Nydegger & Seeley
LandOfFree
Separation of isotopes by ionization does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Separation of isotopes by ionization, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Separation of isotopes by ionization will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2566922