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WO1998038647A1 - Dissolution de barres de combustible nucleaire - Google Patents

Dissolution de barres de combustible nucleaire Download PDF

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Publication number
WO1998038647A1
WO1998038647A1 PCT/GB1998/000632 GB9800632W WO9838647A1 WO 1998038647 A1 WO1998038647 A1 WO 1998038647A1 GB 9800632 W GB9800632 W GB 9800632W WO 9838647 A1 WO9838647 A1 WO 9838647A1
Authority
WO
WIPO (PCT)
Prior art keywords
flow path
fuel rod
fuel
flow
liquid
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/GB1998/000632
Other languages
English (en)
Inventor
Timothy Peter Tinsley
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sellafield Ltd
Original Assignee
British Nuclear Fuels PLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by British Nuclear Fuels PLC filed Critical British Nuclear Fuels PLC
Publication of WO1998038647A1 publication Critical patent/WO1998038647A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • 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
    • G21C19/34—Apparatus or processes for dismantling nuclear fuel, e.g. before reprocessing ; Apparatus or processes for dismantling strings of spent fuel elements
    • G21C19/38—Chemical means only
    • 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

Definitions

  • This invention relates to processes for the dissolution of fuel rods which have been used in nuclear power stations, for instance, in LWR/BWR reactors.
  • spent fuel rods by dissolving the active fuel contents.
  • the spent fuel rods are chopped into lengths of approximately the same size and loaded into a basket.
  • the basket is then lowered into a suitable dissolution medium such as aqueous nitric acid.
  • the basket must be left in the dissolution medium until such time as will be necessary to allow the contents of the slowest reacting chopped length to be dissolved.
  • the equipment for carrying out such a process involves moving parts to lower and raise the basket whereas it is preferable with apparatus handling radioactive materials to have as few moving parts as possible.
  • a process for the dissolution of a fuel rod which comprises dividing the fuel rod into substantially equal length parts, maintaining a flow of fuel rod dissolving liquid along an upward flow path, the rate of flow decreasing upwardly along said flow path, introducing said fuel rod parts to the lower end of said flow path, whereby the fuel rod parts move upwardly along said flow path as the spent fuel is dissolved until the fuel parts reach the upper end of the flow path, and separating the fuel rod parts from said liquid.
  • the present invention is based on the principle of elutriation in which a piece of solid material will sink within a liquid unless the liquid is moving at a rate sufficient to overcome this sinking tendency. If the liquid is capable of dissolving the solid material, then the material will flow with the liquid once it has been dissolved sufficiently to reduce its mass to surface area ratio to a level where it becomes buoyant within the flowing liquid.
  • the present invention also provides apparatus for the dissolution of a fuel rod which comprises means for dividing the fuel rod into substantially equal length parts, means for maintaining a flow of fuel rod dissolving liquid along an upward flow path, the rate of flow decreasing upwardly along said flow path, means for introducing said fuel rod parts to the lower end of said flow path, and means for separating from said liquid the fuel rod parts which reach the upper end of the flow path.
  • the flow maintaining means comprises an elongate vessel arranged with its longitudinal axis substantially vertical and having a cross-sectional area which increases in an upward direction over at least a part of the length of the vessel.
  • the liquid may be any suitable liquid for dissolving spent fuel.
  • An example is nitric acid which will dissolve uranium dioxide, the resultant liquid then being suitable for use with the well-known Purex process for treating dissolved spent fuel.
  • Figure 1 is a graph of free flowing terminal velocity against % uranium dioxide present in a "standard" hull
  • Figure 2 shows a vessel suitable for use in a process of the present invention
  • Figure 3 is a graph of vessel internal diameter against uranium dioxide present in the vessel of Figure 2;
  • Figure 4 shows apparatus of the present invention.
  • Figure 1 of the accompanying drawings shows an example plot of V against percentage uranium dioxide for a "standard" hull in water. If a different liquid is used, for example, uranyl nitrate solution the u t will change.
  • Figure 2 shows an example dissolver vessel with a feed diameter of 150mm, the corresponding maximum flow rate for water, using the example hull, being 38m 3 /hr.
  • the terminal velocities and percentages of uranium dioxide at different levels in the vessel for a standard hull in water are indicated in Figure 2.
  • Figure 3 illustrates graphically the relationship between vessel internal diameter and uranium dioxide present in the hulls, again using a standard hull in water.
  • Apparatus 1 includes a vessel 3 which extends upwardly from a relatively narrow base 5 to a relatively wide section 7 about two-thirds of the way up the vessel. Beyond said relatively wide section 7, the width of vessel 3 decreases relatively rapidly until, at the top of vessel 3, the width is about the same as that of the base 5.
  • Vessel 3 forms part of a liquid flow circuit, liquid being fed via pipe 9 extending from the top of vessel 3 to the base 5 of the vessel. Close to base 5 of vessel 3, there is located an entry point 11 for fuel feed. At point 11 fuel feed, in the form of chopped lengths of spent fuel rods, is fed into pipe 9.
  • Adjacent entry point 11 there is located a pump 13 which maintains a flow of liquid around the liquid circuit as indicated by the arrows in pipe 9 and vessel 3. Adjacent pump 13 there is located an outlet 15 for liquid to be extracted from the flow circuit and sent to plant for chemical separation processes to be carried out.
  • hulls separator 17 Between outlet 15 and vessel 3 there is located a hulls separator 17. At separator 17 hulls are caused to be separated from the circulating liquid. The separating hulls can be sent to waste disposal or to a further dissolver unit which is arranged in series with the unit shown in the drawing.
  • a dissolver unit such as that shown in Figure 4, may be made of any suitable material, such as stainless steel.
  • the fuel feed consists of regular chopped fuel rods (including cladding material) of approximately 50 mm length.
  • This fuel feed is desirably free of any additional fuel assembly parts, that is to say, end appendages, wraps, springs and so on.
  • a fuel dismantling stage is therefore preferably provided for dismantling the fuel assemblies and for single pin or bundle shearing of the fuel rods.
  • fuel feed is fed via inlet 11 to pipe 9 and hence to the base 5 of vessel 3.
  • the fuel dissolves in the liquid in vessel 3 and, as the buoyancy increases, the fuel hulls move upwardly within vessel 3 until they have passed the point where the vessel width is increasing (the beginning of section 7), at which point they are carried out of vessel 3 and towards the hulls separator 17.
  • the liquid velocity, and hence the buoyancy of a hull in the liquid, are determined by the size and shape of the vessel 3 as well as the liquid flow rate. These factors are, in practice, determined by the overall arrangement of the processing plant, that is to say, the number of dissolver units in series.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Plasma & Fusion (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Inorganic Compounds Of Heavy Metals (AREA)

Abstract

L'invention concerne un processus permettant la dissolution d'une barre de combustible et consistant à maintenir un débit de liquide de dissolution de la barre de combustible le long d'une voie d'acheminement supérieure dans laquelle le débit diminue au fur et à mesure que le liquide remonte le long de la voie. Les barres de combustible, divisées en morceaux de longueur sensiblement égale, sont insérées au niveau de l'extrémité inférieure de la voie d'acheminement, après quoi, les morceaux de barres de combustible remontent le long de la voie d'acheminement à mesure que le combustible usé est dissout. Lorsque les morceaux de combustible atteignent l'extrémité supérieure de la voie d'acheminement, ils sont séparés du liquide. L'invention concerne également un appareil permettant de réaliser ce processus.
PCT/GB1998/000632 1997-02-28 1998-02-27 Dissolution de barres de combustible nucleaire Ceased WO1998038647A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9704256.8A GB9704256D0 (en) 1997-02-28 1997-02-28 Dissolution of nuclear fuel rods
GB9704256.8 1997-02-28

Publications (1)

Publication Number Publication Date
WO1998038647A1 true WO1998038647A1 (fr) 1998-09-03

Family

ID=10808526

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1998/000632 Ceased WO1998038647A1 (fr) 1997-02-28 1998-02-27 Dissolution de barres de combustible nucleaire

Country Status (2)

Country Link
GB (1) GB9704256D0 (fr)
WO (1) WO1998038647A1 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4278531A (en) * 1978-08-09 1981-07-14 United Kingdom Atomic Energy Authority Apparatus and method for transporting items
US4297324A (en) * 1979-12-18 1981-10-27 Commissariat A L'energie Atomique Apparatus for the continuous processing of compounds in a liquid
US4435363A (en) * 1981-07-02 1984-03-06 Exxon Nuclear Company, Inc. Continuous countercurrent liquid-solids contactor
US4636362A (en) * 1983-07-04 1987-01-13 Deutsche Gesellschaft Apparatus for the continuous treatment of fragmented fuel elements

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4278531A (en) * 1978-08-09 1981-07-14 United Kingdom Atomic Energy Authority Apparatus and method for transporting items
US4297324A (en) * 1979-12-18 1981-10-27 Commissariat A L'energie Atomique Apparatus for the continuous processing of compounds in a liquid
US4435363A (en) * 1981-07-02 1984-03-06 Exxon Nuclear Company, Inc. Continuous countercurrent liquid-solids contactor
US4636362A (en) * 1983-07-04 1987-01-13 Deutsche Gesellschaft Apparatus for the continuous treatment of fragmented fuel elements

Also Published As

Publication number Publication date
GB9704256D0 (en) 1997-04-16

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