Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G56/00—Compounds of transuranic elements
  • C01G56/001—Preparation involving a liquid-liquid extraction, an adsorption or an ion-exchange
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B60/00—Obtaining metals of atomic number 87 or higher, i.e. radioactive metals
  • C22B60/02—Obtaining thorium, uranium, or other actinides
  • C22B60/0204—Obtaining thorium, uranium, or other actinides obtaining uranium
  • C22B60/0217—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes
  • C22B60/0221—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes by leaching
  • C22B60/0226—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes by leaching using acidic solutions or liquors
  • C22B60/0239—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes by leaching using acidic solutions or liquors nitric acid containing ion as active agent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B60/00—Obtaining metals of atomic number 87 or higher, i.e. radioactive metals
  • C22B60/02—Obtaining thorium, uranium, or other actinides
  • C22B60/0204—Obtaining thorium, uranium, or other actinides obtaining uranium
  • C22B60/0217—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes
  • C22B60/0252—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes treatment or purification of solutions or of liquors or of slurries
  • C22B60/026—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes treatment or purification of solutions or of liquors or of slurries liquid-liquid extraction with or without dissolution in organic solvents
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21C—NUCLEAR REACTORS
  • G21C19/00—Arrangements for treating, for handling, or for facilitating the handling of, fuel or other materials which are used within the reactor, e.g. within its pressure vessel
  • G21C19/42—Reprocessing of irradiated fuel
  • G21C19/44—Reprocessing of irradiated fuel of irradiated solid fuel
  • G21C19/46—Aqueous processes, e.g. by using organic extraction means, including the regeneration of these means
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E30/00—Energy generation of nuclear origin
  • Y02E30/30—Nuclear fission reactors
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W30/00—Technologies for solid waste management
  • Y02W30/50—Reuse, recycling or recovery technologies

Definitions

• This invention relates to nuclear fuel reprocessing and is particularly concerned with the separation of uranium, plutonium and neptunium from zirconium and technetium.
• the organic phase is subjected to separation of fission products by solvent extraction before the so-called U/Pu split.
• This process is typically completed in two stages: separation of the fission products, except technetium (e.g. in the so-called
• a concentrated acid feed (ca. 4 - 6 M nitric acid) with high flowrate, relative to the dissolved spent fuel flowrate, is required in the Tc rejection contactors to efficiently backwash technetium.
• the essence of the present invention is that a process or plant for reprocessing or treating spent fuel uses a technique in which both zirconium and technetium as well as other fission products are simultaneously separated from uranium and plutonium.
• the present invention provides a method for treating or reprocessing spent nuclear fuel in which an organic phase is contacted with an aqueous nitric acid phase containing zirconium, technetium and at least one extractable metal selected from uranium, plutonium and neptunium, the aqueous phase having a relatively low acidity and a relatively high flowrate such that the at least one extractable metal is extracted into the organic phase while the zirconium and technetium predominantly remain in the aqueous phase.
• the aqueous phase normally contains other fission products in addition to zirconium and technetium, and these also predominantly remain in the aqueous phase.
• the aqueous phase usually contains all of the uranium, plutonium and neptunium.
• the method normally further comprises contacting the organic phase into which at least one extractable metal has been extracted with a second aqueous nitric acid phase to strip into the second aqueous phase zirconium, technetium and other fission products which have entered the organic phase.
• the second aqueous phase usually becomes incorporated into the first aqueous phase which is contacted with the organic phase.
• the second aqueous phase feed is preferably of intermediate acidity, e.g. has a nitric acid concentration from 2 to 4 M.
• the invention also provides a Purex reprocessing plant in which there are arranged in series along a solvent stream flowpath (i) a unit for extraction of uranium, plutonium and neptunium from an aqueous acid stream containing dissolved spent fuel into the solvent stream while zirconium, technetium and other fission products predominantly remain in the aqueous phase, (ii) a unit for stripping of zirconium, technetium and other fission products from the solvent stream into an aqueous acid phase which passes to the unit (i) where a combination thereof with a dissolved spent fuel feed forms said aqueous acid stream, and, optionally, (iii) a unit for backstripping of acidity from the solvent stream into a low acid strip stream which passes to the unit (ii) where a combination thereof with an intermediate acidity strip stream forms said aqueous acid phase.
• Figure 1 is a standard single cycle Purex flowsheet
• Figure 2 is a partial flowsheet of a Purex reprocessing process incorporating the method of the invention.
• the flowsheet contains the units shown in Tables 1 & 2.
• Figure 2 illustrates a portion of a reprocessing plant which contains apparatus (unit HA) in which is performed a method for treating or reprocessing spent nuclear fuel in which an organic phase, in this case 30 % TBP/OK, is contacted with an aqueous nitric acid phase containing zirconium, technetium and at least one extractable metal selected from uranium, plutonium and neptunium, the aqueous phase having a relatively low acidity and a relatively high flowrate such that the at least one extractable metal is extracted into the organic phase while the zirconium and technetium predominantly remain in the aqueous phase.
• an organic phase in this case 30 % TBP/OK
• the organic stream SI is contacted with an aqueous nitric acid phase comprising the combined aqueous streams Al, A2 and A3 in the unit HA, which is a multi-stage contactor in the illustrated embodiment.
• the organic stream extracts uranium, plutonium and neptunium into the organic phase.
• the fission products including zirconium and technetium remain in the aqueous phase and exit the contactor in PI, the highly active raffmate.
• the nitric acid concentration of the aqueous phase product is preferably within the range of 2 to 4M, preferably 2 to 3M and preferably best at 2.2 M.
• the ratio of the organic phase flowrate to aqueous phase (Al + A2 + A3) flowrate to is preferably 0.7 and 1.5, preferably between 0.8, eg 8.8 to 1.3 and preferably set at 0.91; the preferred numerical parameters are generally applicable to all embodiments of the invention.
• the organic phase loaded with uranium, plutonium and neptunium goes from unit HA to unit HS, in this case a multi-stage contactor unit, where fission products including zirconium and technetium are stripped from the organic phase into a second aqueous nitric acid phase (Al plus A2).
• the organic phase loaded with uranium, plutonium and neptunium goes from unit HS to unit HSS, in this case a multi-stage contactor unit, where acidity is backwashed from the organic phase.
• This is not an essential requirement of the invention because it is performed to reduce the organic phase acidity prior to the U/Pu split. It has little effect on zirconium and technetium stripping from the organic phase.
• the aqueous stream Al is contacted with the organic stream in the unit HSS.
• the aqueous stream is a low acidity (e.g. 0.05 to 0.2 M nitric acid), low flowrate stream so that acid can be stripped from the organic phase.
• the solvent : aqueous flowrate ratio may be from 0.05 to 0.20, depending on the contactor equipment performance.
• the aqueous product of the unit HSS is combined with the aqueous stream A2 and is contacted with the organic stream in the unit HS.
• the aqueous stream A2 is of intermediate acidity (ca. 4 to 2 M nitric acid) although this is not an essential requirement of the invention. It is also of reasonably high flowrate to ensure efficient stripping of fission products including zirconium and technetium.
• the second aqueous phase (combined Al and A2) therefore usually has intermediate acidity, usually from 2 to 4 M, and the ratio of the second organic phase flowrate to aqueous phase flowrate to is usually between 1.0 to 2.0, preferably 1.1 to 2.0 but desirably about 1.3.
• the aqueous product of the unit HS is combined with the aqueous stream A3 and is contacted with the organic stream in the unit HA.
• the aqueous stream A3 is the dissolved spent fuel feed.
• the A3 stream is again of intermediate acidity but normally less than 3 M nitric acid. Optimum performance of this invention is achieved when the acidity of this stream is minimised.
• the invention is not restricted as to the manner in which the organic product II is treated.
• II is sent to a uranium, plutonium split operation, for example a conventional process as used in a commercial plant.
• Table 1 Illustrative flowrates and concentrations for some of the streams shown in Figure 2.
• the method of the invention dispenses with the separation of technetium in technetium rejection contactors. Accordingly, the plant may be smaller, resulting in both environmental and economic benefits. The method also features lower nitric acid inventory so again resulting in both environmental and economic benefits.
• a further benefit of the preferred methods of the invention is that relatively relaxed flowsheet control is possible in the HA/ ⁇ S/HSS contactors.
• the preferred method uses the same solvent inventory but avoids a high uranium loading in the HS contactor cascade. Accordingly, variation in flowrates and feed compositions has significantly less effect on flowsheet performance.
• a yet further benefit enabled by the method of the invention is that excessive zirconium recycle in the HA/ ⁇ S HSS contactors is completely avoided because zirconium is effectively routed to PI, the highly active raffmate. Accordingly, the risk of third phase formation is significantly reduced.
• the invention includes a Purex reprocessing method in which an aqueous acid phase containing dissolved spent fuel is contacted with an organic phase, characterised in that the aqueous phase contacted with the organic phase has a relatively low acidity and a relatively high flowrate such that uranium, plutonium and neptunium are extracted from the aqueous phase into the organic phase while zirconium, technetium and other fission products predominantly remain in the aqueous phase.
• the organic phase and the aqueous phase are contacted in a first contactor unit, and the organic phase is fed from the first contactor unit to a second contactor unit in which it contacts a second aqueous nitric acid phase to strip into the second aqueous phase zirconium, technetium and other fission products which have entered the organic phase, the second aqueous phase being combined with the aqueous acid phase containing the dissolved spent fuel before the latter contacts the organic phase in the first contactor.
• the organic phase is fed from the second contactor unit into a third contactor unit in which the organic phase is contacted with an aqueous low acid strip phase for backwashing of acidity from the organic phase into the low acid strip phase.
• the methods of the invention are typically methods for reprocessing nuclear fuel to form a fissile material optionally in the form of a gel, a powder, a master batch material, a fuel pellet, a fuel pin or a fuel assembly.

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• 1999
  • 1999-05-28 JP JP2000552044A patent/JP2002516810A/ja active Pending
  • 1999-05-28 WO PCT/GB1999/001711 patent/WO1999062824A1/en not_active Application Discontinuation
  • 1999-05-28 EP EP19990925171 patent/EP1091908A1/de not_active Withdrawn

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