PatentDe  


Dokumentenidentifikation EP0722611 13.08.1998
EP-Veröffentlichungsnummer 0722611
Titel VERFAHREN UND EINRICHTUNG ZUR HERSTELLUNG VON RADIOAKTIVEM IOD
Anmelder McMaster University, Hamilton, Ontario, CA
Erfinder HASSAL, Scott, Bradley, Hamilton, Ontario L8S 3W4, CA
Vertreter derzeit kein Vertreter bestellt
DE-Aktenzeichen 69411576
Vertragsstaaten AT, BE, CH, DE, DK, ES, FR, GB, GR, IE, IT, LI, LU, MC, NL, PT, SE
Sprache des Dokument En
EP-Anmeldetag 16.09.1994
EP-Aktenzeichen 949267538
WO-Anmeldetag 16.09.1994
PCT-Aktenzeichen CA9400511
WO-Veröffentlichungsnummer 9510114
WO-Veröffentlichungsdatum 13.04.1995
EP-Offenlegungsdatum 24.07.1996
EP date of grant 08.07.1998
Veröffentlichungstag im Patentblatt 13.08.1998
IPC-Hauptklasse G21G 1/06
IPC-Nebenklasse G21G 4/08   

Beschreibung[en]

The present invention relates to the production of radioactive iodine and, in particular, to a novel procedure and apparatus for effecting the same on a large scale in safety.

Iodine-125 (125I) is a radioactive isotope of iodine with a relatively long half-life of 60 days. This material is used for medical diagnostic studies and for medical and biological research. This iodine isotope is valuable because the radiation it emits is less damaging than that from other isotopes of iodine.

It is known to produce such material by irradiating 124Xe with thermal neutrons, according to the following scheme:

125I decays to form 125Te or may be converted to 126I which decays to 126Te, as follows:
Supplies of 125I isotope are limited and there is an increasing demand for this material. Iodine-126 that is present with 125I is a contaminant. Because of the emission of more damaging radiation by 126I, the Food and Drug Administration, U.S.A., requires that 125I for use in the human body contains less than 5 parts per million of 126I.

According to a first aspect of the present invention, there is provided a method of producing radioactive 125I, characterized by the steps of:

  • feeding 124Xe from a source thereof to an irradiation zone located within an enclosure,
  • irradiating said 124Xe in said enclosure with neutrons to cause the formation of 125Xe therefrom,
  • transferring irradiated gas by pumping from said irradiation zone to a decay zone located within said enclosure and free from neutron flux, and
  • permitting 125Xe to decay to form 125I in said decay zone.

According to a second aspect of the present invention, there is provided an apparatus for producing radioactive 125I, characterized by:

  • a housing which is gas-tight and submersible in a nuclear reactor water pool and defining an interior chamber, said housing having upper and lower separable portions to permit access to said interior chamber,
  • a first enclosure within said chamber arranged to permit neutron irradiation of 124Xe gas contained therein by the nuclear reactor,
  • a second removable enclosure within said chamber connected in interruptible fluid flow relationship with said first enclosure for transfer of irradiated xenon gas from said first enclosure to said second enclosure to permit decay of 125Xe to 125I in said second enclosure free from neutron flux,
  • said second enclosure having valved inlet/outlet port means to permit 124Xe to be received into said apparatus, to permit 125I solution to be discharged from said second enclosure, and to permit the passage of xenon gas between said first and second enclosures,
  • first pump means operably connected to said first enclosure for precipitating 124Xe received into said apparatus through said valved port means when said first and second enclosures are in fluid flow relationship and for providing gaseous xenon in said first enclosure when said first and second enclosures are out of fluid flow relationship, and
  • second pump means operably connected to said second enclosure for precipitating irradiated xenon received from said first enclosure when said first and second enclosures are in fluid flow relationship and for providing gaseous irradiated xenon in said second enclosure when said first and second enclosures are out of fluid flow relationship.

The present invention provides a novel method and apparatus for the production of 125I, which is amenable to large-scale production. The procedure is effected on a batch basis with 124Xe gas being irradiated periodically with a neutron flux over a period of time and permitting 125Xe so provided to be transferred remotely and in safety to a different portion of the apparatus, where the 125Xe decays to form 125I. For example, for a one-week cycle, approximately 5g of 124Xe gas is irradiated for up to about 15 hours a day for three to five days in a flux of approximately 5 x 1012 neutrons cm-2 s-1, to produce about 0.3 TBq (8 Ci) of 125I which is free from 126I.

The quantity of 125I can be increased by irradiating larger amounts of 124Xe or by locating the apparatus in a higher flux. The upper limit of production of 125I using the batch procedure of the present invention is about 0.74 TBq (20 Ci) of 125I per batch, by employing a suitable combination of target amount, neutron flux and irraditation time.

Limits of the individual parameters of the process are irradiating up to 6g of 124Xe, using fluxes of up to 2 x 1013 neutrons cm-2 s-1 and irradiating for up to five 15-hour days.

In the method of the present invention, the location of the decay zone free from neutron flux ensures that the 125I is produced free from 126I.

For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:-

  • Figure 1 is a schematic representation of a submersible apparatus for effecting the process of the present invention;
  • Figure 2 is a schemtatic representation of the gas-handling system associated with the submersible apparatus shown in Figure 1; and
  • Figure 3 is a schematic representation of a iodine recovery station utilized in the production of the 125I.

Referring to the draxings, Figure 1 shows a submersible apparatus 10 which is constructed with provides double containment of materials, except during the interchange of the decay chamber as outlined below. The construction of the submersible apparatus 10 is all metal, welded wherever possible, and employs O-ring seals, so as to be air- and water-tight. The submersible apparatus 10 is used to irradiate 124Xe in one container, to transfer the resulting 125Xe to a separate container for decay to 125I free from neutron flux and to reload the 124Xe for additional irradiations.

The apparatus 10 includes an outer housing 12 which encloses the remaining elements of the apparatus. The outer housing 12 includes a lower fixed housing portion 14 and an upper removable housing portion 16. The lower housing portion 14 is the anchor point for all the structural connections to the other components. In particular, a stage (not shown) secures two cryopumps 32, 34, while filler tubes 40, 42 and extended valve handles 44 connect the lower housing portion 14 to the bulkhead 17 and hold the latter in place. The upper housing portion 16 seals with both the bulkhead 17 and the lower housing portion 14 to provide for double containment of radioactive materials. The upper housing portion 16 is removable from the lower housing portion 14 to permit decay chamber interchange.

Within the housing 12 is located an irradiation chamber 18 in which 124Xe is subjected to neutron irradiation from any convenient source, such as a nuclear reactor, and a decay chamber 20 in which the 125Xe can decay to 125I free from neutron flux. The aforementioned chambers 18, 20 are connected via tubes 22, 24 and can be isolated and/or separated from each other by means of a valve mechanism 28. The valve mechanism is described in more detail below with respect to Figure 2, and may include an optional getter trap.

The irradiation chamber 18 is connected via pipes 22 and 30 to a condenser and cold cell structure 32, which constitutes a cryopump. Similarly, the decay chamber 20 is connected (in this case directly) to a condenser and cold cell structure 34, which also constitutes a cryopump. These cryopumps permit irradiated xenon to be transferred from the irradiation chamber 18 to the decay chamber 20 and decayed xenon to be reloaded from the decay chamber 20 into the irradiation chamber 18. When irradiated xenon is transferred from the irradiation chamber 18 to the decay chamber 20, the optional getter trap associated with valve mechanism 28 captures any volatile iodine which may be carried along with the irradiated xenon. In addition, the optional getter trap can improve the efficacy of the cryopumping process by reducing the partial pressure due to non-condensible gases that are formed during the irradiation. For each cryopump 32, 34, the condenser slides into a sleeve in the cold cell, thus effecting good thermal contact while preserving true double containment, and allowing the decay chamber 20 to be removed from the remainder of the apparatus readily.

The decay chamber 20 includes a main valved connector 36 to permit initial evacuation and periodic removal of any non-condensible gases that are not captured by the optional getter trap. A sniffer port 38 is provided in the bulkhead 17 to permit sampling of the gas inside the housing 12 to ensure an absence of leaks within the system. Filler tubes 40, 42 penetrate the bulkhead 17 to permit remote filling and emptying of the cold cell portion of the cryopumps 32, 34 with liquid nitrogen. Filling of the cold cells with liquid nitrogen may be achieved by connecting a supply tube to a pressurized liquid nitrogen container and inserting the supply tube through the appropriate filler tube 40, 42 to the bottom of the cold cell. Liquid nitrogen levels may be checked with by using thermocouples positioned within the cold cell, or by observing the exhaust from the mouth of the filler tube.

Extended valve handles 44 passing through the bulkhead 17 permit remote operation of the disconnect valve mechanism 28. The penetration of the valve handles 44 through the bulkhead employs rotating seals in order to maintain containment. The valve mechanism 28 comprises two valves 33, 35 that can be remotely actuated, and an optional getter trap 31 located between the valves 33, 35 and which includes an integral valve 37. The upper remotely actuated valve 35 is integral to the decay chamber 20, and has a face-seal disconnect that joins it to valve 37, if the trap is included, or to the lower remotely actuated valve 33, if the trap is excluded. The disconnect allows the decay chamber 20 to be separated from the rest of the apparatus during decay chamber interchange, as described below. If the optional getter trap 31 is included, the valve 37 is left open, except during the decay chamber interchange, when the valve 37 is closed in order to prevent air from entering the getter trap 31 and deactivating the getter. The getter is a material that absorbs certain gases, including hydrogen, oxygen, nitrogen and iodine, while not affecting noble gases, such as xenon. Prior to its first use, and periodically thereafter, the getter requires activation, which is achieved by heating to an elevated temperature for a period of time in vacuum or under an inert gas atmosphere.

A top cap 46, which seats on the upper housing 16, serves to prevent water from entering the cold-cell portion of the cryopumps 32, 34 while the apparatus 10 is maintained submersed in the reactor pool and to provide redundant encapsulation for all the bulkhead welds, fittings and seals. The top 46 is removable for reloading and transfer operations and is provided with a sniffer port 48, which permits radioactive-gas leaks to be detected safely.

The submersible apparatus 10 is kept generally in the pool of a light-water nuclear reactor. The apparatus 10 may be submerged completely and positioned adjacent to the reactor core, in order to effect neutron irradiation of the irradiation chamber 18, or may be partially submerged to a greater or lesser extent adjacent to the edge of the reactor pool, in order to perform other operations.

Figure 2 shows a gas handling and vacuum station 50 employed with the submersible apparatus 10 of Figure 1. The gas handling and vacuum station 50 is used to evacuate the submersible apparatus initially, to add or remove 124Xe and to remove permanent gases from the system, as required.

The gas handling and vacuum station 50 includes a rotary vacuum pump 52, which exhausts through an activated charcoal filter 54 to an exhaust line 56. A diffusion pump 66 is connected to the inlet of the rotary vacuum pump 52. The inlet of the diffusion pump 66 is ultimately connected to the main valved connector 36 of the decay chamber 20, via a valve 58, a flexible tube 60, a dry-ice trap 62 and liquid-nitrogen traps 64. The main valved connector 36 and the valve 58 are joined with face-seal fittings, and constitute a double-valved disconnect. A similar disconnect 74 is provided between the dry ice trap 62 and the liquid nitrogen traps 64.

A 124Xe storage cylinder 68 is connected between the dry-ice trap 62 and the liquid-nitrogen traps 64 by a valve 70. During the initial evacuation of the gas-wetted portions of the submersible apparatus 10 by the diffusion pump 66 and rotary vacuum pump 52, the valve 70 is closed. Xenon-124 is added to the apparatus by first closing valve 72 and then opening valve 70 to permit the desired amount of 124Xe to enter the evacuated apparatus through disconnect 74, dry-ice trap 62, flexible tube 60, valve 58 and main valved connector 36.

When the required amount of 124Xe has been loaded, valve 70 is closed and the 124Xe is cryopumped into the condenser of the lower cryopump 32 in the submersible apparatus 10, whereupon the two remotely-actuated valves 33, 35 of the valve mechanism 28 are closed and the lower cryopump 32 is warmed to room temperature, thus causing the 124Xe to evaporate and expand to fill the irradiation chamber 18, and the connecting tubes 22, 24 and 30. Xenon is removed from the submersible apparatus 10 by cooling the storage cylinder 68 with liquid nitrogen while valve 72 is closed so that the xenon condenses within the storage cylinder 68.

The dry-ice trap 62 serves to capture any volatile iodine and is checked routinely to ensure that iodine that is formed in the apparatus exists in a bound state. The dry-ice trap 62 includes two quartz windows, being relatively transparent to the gamma emissions of 125I, and is of such a design that any 125I so captured within the cold volume of the dry-ice trap 62 is detectable noninvasively by means of a suitable detector that is positioned alternately adjacent to such windows. The liquid nitrogen trap 64 captures any xenon that is not collected in the storage cylinder 68 and also traps any iodine that might pass the dry ice trap 62. A thermocouple pressure gauge 76 is provided in the circuit to effect pressure readings in the milliTorr range, which would allow any problems during transfer to be detected.

The pumping system, comprising the rotary vacuum pump 52 and the diffusion pump 66, is provided with a Penning gauge 78, which monitors the vacuum at the diffusion pump inlet, and is exhausted through the charcoal filter 54. Any radioactivity detected at the filter results in shutdown of the apparatus for investigation of the problem. These elements and procedures ensure complete safety in operation of the equipment.

The iodine recovery station 80 is shown schematically in Figure 3 and includes an enclosing glove box 82, which provides double encapsulation while iodine is washed from the interior of the decay chamber 20 and transferred to a storage and shipping container. Iodine-125 is readily shielded and ample shielding can be provided, as desired.

The glove box 82 is maintained at a slight negative pressure by connection to a line 84 that vents to the building exhaust system through an activated charcoal filter assembly 86. An internal recirculating blower and filter 88 continuously traps any volatile iodine that may be present in the glove box 82. In the event that a radioactive leak is detected, the exhaust flow is halted by closing the damper 90, thus sealing the glove box 82 pending resolution of the problem. The decay chamber 20 and any other required components are loaded into the glove box 82 through a passthrough 92. Other components indicated in Figure 3 include a needle fitting 94, which may be attached to the main valved connector 36 of the decay chamber 20, a heater element 96, which is placed in an integral heater cup of the decay chamber 20, and an evacuated vial 98, which includes a rubber septum closure 100.

In operation of the apparatus depicted in Figures 1 and 2, the gas-wetted portions of the submersible apparatus 10 initially are evacuated through the main valved connector 36 to the ultimate vacuum of the pumping station comprising the rotary vacuum pump 52 and the diffusion pump 66. Liquid nitrogen is introduced into the lower cryopump cold cell 32 through a supply tube that is inserted coaxially into the filler tube 40.

The desired quantity of 124Xe from storage cylinder 68 then is admitted to the submersible apparatus 10 through the main valved connector 36. The 124Xe condenses in the lower cryopump 32. The remotely-activated valves 31, 35 then are closed. Following warming of the lower cryopump 32 with dry air admitted via the supply tube that is within the filler tube 40, the 124Xe evaporates so that approximately 95% of the 124Xe fills the irradiation chamber 18.

The main valved connector 36 then is closed and the gas handling and vacuum station 50 is disconnected from the submersible apparatus 10. The upper housing portion 16 then is situated in place and the top cap 46 is installed.

The submersible apparatus 10 then is fully submerged in the reactor pool and positioned with the irradiation chamber 18 adjacent to the reactor core, thus exposing the 124Xe within the irradiation chamber 18 to the desired neutron flux. The remote location of the decay chamber 20 with respect to the irradiation chamber ensures that the decay chamber is free from neutron flux, which ensures that 126I is not formed. After the scheduled irradiation time has elapsed, the submersible apparatus 10 is moved away from the core and raised until the top cap 46 is above the level of the reactor pool. The air between the bulkhead 17 and the top cap 46 is sampled through the outer sniffer port 48 to ensure that no leakage of radioactive gas has occurred within the apparatus 10.

The top cap 46 then is removed and the upper cryopump cold cell 34 is filled with liquid nitrogen through a supply tube, which is positioned within the filler tube 42. With the upper cryopump 32 operating, the valves 33, 35 are opened, which causes irradiated xenon to pass via tubes 22, 24 into the condenser portion of the upper cryopump 34, where the condenser portion is integral with the decay chamber 20. The valves 33, 35 then again are closed. Dry air is admitted into the cold cell of the upper cryopump 34 via the supply tube which is within the filler tube 42 to cause evaporation of the condensed irradiated xenon within the decay chamber 20. The top cap 46 then is replaced.

The submersible apparatus 10 then is submerged in the reactor pool for the decay period to provide enhanced safety. Any radiation which might escape the apparatus 10 during that period is contained within the reactor pool. Furthermore, the increased hydrostatic pressure due to submersion greatly decreases the probability of such leakage.

Following the decay period, during which radioactive 125Xe decays to radioactive 125I, which deposits on the wall of the decay chamber 20, the submersible apparatus is raised to the surface of the reactor pool and the air again is sampled via the outer sniffer port 48 before removing the top cap 46. The lower cryopump 32 again is started by introducing liquid nitrogen into the cold cell and valves 33, 35 again are open, permitting undecayed xenon to pass from the decay chamber 20 to be condensed in the cryopump 32.

The valves 33, 35 again are closed and the cryopump 32 warmed to cause evaporation of the xenon. The top cap 46 is replaced and the submersible apparatus then is ready for further irradiation. The cycle then is repeated as required to provide the desired quantity of 125I from the initial feed quantity of 124Xe. Generally, about three to five cycles are performed per production run of 125I.

Following the final irradiation and transfer for a production run, the submersible apparatus 10 is left for an extended period submerged in the reactor pool to permit the radioactive xenon to decay by a considerable degree, generally by up to about 90%. The remaining xenon again is condensed by the lower cryopump 32, so that the decay chamber 20 is evacuated of xenon. Following removal of the cap 46, the air inside the submersible apparatus is sampled through the inner sniffer port 38 and, if no radioactive leakage is detected, the submersible apparatus 10 is raised until the upper housing portion 16 is above the reactor pool level.

Next, the upper housing portion 16 is removed. A monitored exhaust flow is provided to collect any radioactive gases that might escape during the period that the double containment is not maintained, with the effluent from such exhaust passing through an activated charcoal filter before being vented to the building exhaust.

The gas-handling and vacuum station 50 then is attached to the main valved connector 36 and the lines evacuated. To verify that the final cryopumping operation with respect to residual xenon was successful, valve 72 is closed and main valved connector 36 opened so that the thermocouple gauge 76 may indicate the pressure within the decay chamber 20. If required, the decay chamber 20 is evacuated through the dry-ice trap 62 and the liquid-nitrogen traps 64 to remove any permanent gases. Following evacuation of any significant quantities of permanent gases, the xenon may be cryopumped back to the irradiation chamber 18 by the procedure described above.

When such pumping is complete, the flexible tube 60 is disconnected from the main valved connector 36, which now is closed, and the two ports that are so exposed are capped. The complete absence of xenon in the decay chamber is confirmed by checking that there is no significant radiation field due to the decay chamber.

If the optional getter trap 31 is present, the integral valve 37 is closed. The extended valve handle 44 is removed from the valve 35, and the decay chamber 20 is detached from the rest of the apparatus 10 at the disconnect between the valves 35 and 37, if the getter trap 31 is included, or between valves 35 and 33, if the getter trap 31 is excluded. The remaining exposed port of the decay chamber 20 and the other port are capped and the decay chamber transported to the iodine recovery station.

A second decay chamber 20 is fitted into the apparatus and the extended valve handle 44 and upper housing portion 16 are replaced. The submersible apparatus 10 then is ready for another production run.

The first decay chamber 20 is moved into the glove box 82 via the passthrough 92, and is secured in an inverted position as shown. A needle fitting 94 is attached to the main valved connector 36 of the decay chamber 20. The needle 94 is pushed through the septum of a large evacuated fill flask (not shown) that contains degassed aqueous sodium hydroxide solution, or other suitable refluxable solvent for 125I, but is otherwise evacuated. The needle 94 is short relative to the length of the flask, and the volume of the flask is sufficient to greatly decrease the pressure within the needle 94 and main valved connector 36. The decay chamber and fill flask are swivelled through 180° so that the needle 94 is immersed in the sodium hydroxide solution. The main valved connector 36 is opened, allowing the desired amount of sodium hydroxide solution to enter the decay chamber 20, whereupon the main valved connector 36 is closed. The quantity of sodium hydroxide solution admitted is determined initially by reference to calibration marks that are inscribed on the neck of the fill flask, adjacent to the rubber septum, and is verified by before and after mass measurements of the fill flask and its contents.

A heater element 96 is positioned within the integral heater cup of the decay chamber 20 and the heater cup is filled with deionized water. When the heater element 96 is energized, pure water evaporates from the sodium hydroxide solution within the decay chamber 20 and condenses upon all internal surfaces, whereupon the water so delivered dissolves any iodine present before dripping back into the pool of sodium hydroxide solution at the bottom of the decay chamber 20. This refluxing process effects an efficient cleansing of the internal surfaces of the decay chamber 20 and causes the iodine to become dissolved in the aqueous sodium hydroxide solution. Following the completion of the refluxing procedure, heating is discontinued and the lower portion of the decay chamber 20 is actively cooled by placing ice in the integral heater cup of the decay chamber 20, thus causing any remaining water vapour in the volume of the decay chamber 20 to condense in the pool of aqueous sodium hydroxide solution.

An evacuated vial 98 is positioned with the needle 94 penetrating the rubber septum 100 and forming a vacuum tight seal. Upon opening the main valved connector 36, the iodine solution passes from the decay chamber 20 through the needle fitting 94 into the vial, which is shielded with lead. If required, valve 35 can be opened briefly in order to admit air and assist in this operation.

Following the loading of the vial 98 with the iodine solution, the main valved connector 36 and the valve 35 are closed, and the needle 94 is carefully withdrawn from the septum 100, which is self-sealing. The 125I solution thus is ready for assaying, subdivision, outer packaging and shipment.

The needle 94 then is detached from the empty decay chamber 20 which then is completely evacuated using the gas-handling and vacuum station 50 in order to remove all traces of moisture. Any iodine not transferred to the vial remains in the decay chamber 20 in a non-volatile state. The dried and evacuated first decay chamber 20 then is ready to be exchanged with the second decay chamber 20 for the following production run.

It will be apparent from the above description of the construction and operation of the submersible apparatus in the production of 125I from 124Xe that the procedure is effected in a highly safe manner and by a procedure whereby the 125I is obtained substantially free from 126I. The materials of construction generally are aluminum and stainless steel and provide a double containment environment against leakage of 125Xe and/or 125I at all stages of the procedure, except during the decay chamber interchange. During the latter operation, the xenon is confined to the irradiation chamber and a monitored exhaust flow is provided in the vicinity of the coupling to protect the operator.

The 35 keV gamma radiation from the 125I is relatively easy to shield, since a 1/10th value layer of lead for 35keV gammas is only 0.lmm. The 4mm stainless steel walls of the decay chamber decrease the radiation fields due to 125I by a factor of 1011.

While radiation from 125Xe is more penetrating, any portion of the apparatus which contains significant amounts of 125Xe is always well below the surface of the reactor pool and hence is effectively shielded.

At the iodine-recovery station 80, the double containment is provided by the glove box 82.

In summary of this disclosure, the present invention provides a novel method of producing radioactive 125I from 124Xe in a safe and effective manner in a novel double-contained apparatus. Modifications are possible within the scope of the claims.


Anspruch[de]
  1. Ein Verfahren zur Herstellung von radioaktivem 125I, gekennzeichnet durch die Schritte:
    • Zufuhr von 124Xe von einer 124Xe-Quelle in einen Bestrahlungsbereich, der in einem geschlossenen Behälter liegt,
    • Bestrahlung des 124Xe in obigem geschlossenen Behälter mit Neutronen, um die Bildung von 125Xe daraus zu bewirken,
    • Fördern von bestrahltem Gas durch Pumpen von dem Bestrahlungsbereich zu einem Zerfallsbereich, der in dem geschlossenen Behälter liegt und nicht dem Neutronenfluß ausgesetzt ist, und
    • Zulassen, daß in dem Zerfallsbereich das 125Xe zerfällt, um so 125I zu bilden.
  2. Das Verfahren nach Anspruch 1, wobei die Zufuhr von 124Xe in den Bestrahlungsbereich vollzogen wird durch:
    • Verbinden der 124Xe-Quelle mit einem Einspeiseeinlaß, der wählbar über eine Fluidströmung in Verbindung mit dem Bestrahlungsbereich und mit einem ersten Kondensationsbereich in dem geschlossenen Behälter steht, und Fließenlassen des 124Xe durch den Einspeiseeinlaß,
    • Kondensieren des zugeführten 124Xe in den ersten Kondensationsbereich und Schließen des Einspeiseeinlasses, und
    • Abdampfen des flüssigen 124Xe von dem ersten Kondensationsbereich zu dem Bestrahlungsbereich hin.
  3. Das Verfahren nach Anspruch 1 oder 2, wobei der Transfer des bestrahlten Gases vollzogen wird durch:
    • Herstellen einer Verbindung über eine Fluidströmung in dem geschlossenen Behälter zwischen dem Bestrahlungsbereich und dem Zerfallsbereich,
    • Kondensieren von bestrahltem Gas, das zwischen dem Bestrahlungsbereich und dem Zerfallsbereich fließt, in einem zweiten Kondensationsbereich in dem geschlossenen Behälter, der mit dem Zerfallsbereich über eine Fluidströmung in Verbindung steht,
    • Beenden der Verbindung über eine Fluidströmung zwischen dem Bestrahlungsbereich und dem Zerfallsbereich, und
    • Abdampfen von kondensiertem bestrahltem Gas von dem zweiten Kondensationsbereich zu dem Zerfallsbereich hin.
  4. Das Verfahren nach einem der Ansprüche 1 bis 3, wobei das nach dem Zerfall von bestrahltem Gas zurückbleibende Gas in den Bestrahlungsbereich übergeführt wird durch:
    • Herstellen einer Verbindung über eine Fluidströmung in dem geschlossenen Behälter zwischen dem Zerfallsbereich und dem Bestrahlungsbereich und einem ersten Kondensationsbereich in dem geschlossenen Behälter,
    • Kondensieren von Restgas, das zwischen dem Zerfallsbereich und dem Bestrahlungsbereich fließt, in dem ersten Kondensationsbereich in dem geschlossenen Behälter,
    • Beenden der Verbindung über eine Fluidströmung zwischen dem Bestrahlungsbereich und dem Zerfallsbereich, und
    • Abdampfen von kondensiertem Gas von dem ersten Kondensationsbereich zu dem Bestrahlungsbereich hin, und
    • Wiederholen der Schritte Bestrahlung, Fördern von bestrahltem Gas und Zulassen des Zerfalls.
  5. Das Verfahren nach einem der Ansprüche 1 bis 4, wobei die Bestrahlung von 124Xe dadurch bewirkt wird, daß der in das Becken eines Leichtwasser-Kernreaktors getauchte geschlossene Behälter einen an den Reaktorbereich angrenzenden Platz erhält, und wobei der Schritt des Zerfallens sich vollzieht, während der geschlossene Behälter an einem Platz in dem Becken belassen wird, wo er eingetaucht ist.
  6. Das Verfahren nach einem der Ansprüche 1 bis 5, wobei nach der Bildung von 125I der Zerfallsbereich von dem geschlossenen Behälter entfernt wird, um aus diesem das 125I gewinnen zu können.
  7. Das Verfahren nach Anspruch 6, wobei das 125I dadurch aus dem Zerfallsbereich entfernt wird, daß eine wäßrige Lösung für 125I dem Zerfallsbereich zugeführt wird, daß ein Hin- und Herfließen von der wäßrigen Lösung in dem Zerfallsbereich bewirkt wird, um festes 125I von internen Oberflächen des Zerfallsbereichs zu entfernen und um eine wäßrige Lösung von der Jodlösung zu bilden, und daß die wäßrige Lösung von dem Zerfallsbereich entfernt wird.
  8. Das Verfahren nach Anspruch 7, wobei die wäßrige Lösung eine wäßrige Natriumhydroxid-Lösung ist.
  9. Eine Vorrichtung zur Herstellung von radioaktivem 125I, gekennzeichnet durch:
    • Ein Gehäuse (12), das gasdicht und in ein Kernreaktor-Wasserbecken eintauchbar ist und eine innere Kammer umgrenzt, wobei das Gehäuse obere (16) und untere (14) trennbare Teile hat, um Zugang zu der inneren Kammer zu ermöglichen,
    • ein erster geschlossener Behälter (18) in der Kammer, der so angeordnet ist, daß er die Bestrahlung mit Neutronen von in ihm enthaltenen 124Xe-Gas durch den Kernreaktor ermöglicht,
    • ein zweiter abnehmbarer geschlossener Behälter (20) in der Kammer, der mit dem ersten geschlossenen Behälter (18) in einer unterbrechbaren Beziehung der Fluidströmung steht, zum Fördern von bestrahltem Xenongas von dem ersten geschlossenen Behälter (18) zum zweiten geschlossenen Behälter (20), um so den Zerfall von 125Xe in 125I in dem zweiten geschlossenen Behälter (20) in Abwesenheit von Neutronenfluß zu ermöglichen,
    • wobei der zweite geschlossene Behälter (20) mit Ventilen versehene Einlaß-/Auslaß-Durchströmvorrichtungen (33, 35, 37) hat, um zu ermöglichen, daß 124Xe in die genannte Vorrichtung (10) aufgenommen werden kann, um zu ermöglichen, daß 125I-lösung von dem zweiten geschlossenen Behälter (20) abgelassen werden kann, und um die Passage von Xenongas zwischen dem ersten (18) und dem zweiten (20) geschlossenen Behälter zu ermöglichen,
    • erste Pumpvorrichtungen (32), die betrieblich mit dem ersten geschlossenen Behälter (18) verbunden sind, zum Bewirken des Hindurchführens von in die genannte Vorrichtung (10) aufgenommenem 124Xe durch die mit Ventilen versehenen Einlaß-/Auslaß-Durchströmvorrichtungen (33, 35, 37), wenn der erste (18) und der zweite (20) geschlossene Behälter in einer Fluidströmungsbeziehung stehen, und zum Bereitstellen von gasförmigem Xenon in den ersten geschlossenen Behälter (18), wenn der erste (18) und der zweite (20) geschlossene Behälter nicht in Fluidströmungsbeziehung stehen, und
    • zweite Pumpvorrichtungen (34), die betrieblich mit dem zweiten geschlossenen Behälter (20) verbunden sind, zum Bewirken des Flusses von bestrahltem Xenon, das von dem ersten geschlossenen Behälter (18) aufgenommen wurde, wenn der erste (18) und der zweite (20) geschlossene Behälter in einer Fluidströmungsbeziehung stehen, und zum Bereitstellen von gasförmigem bestrahltem Xenon in dem zweiten geschlossenen Behälter (20), wenn der erste (18) und der zweite (20) geschlossene Behälter nicht in Fluidströmungsbeziehung stehen.
  10. Die Vorrichtung nach Anspruch 9, wobei die erste (32) und die zweite (34) Pumpvorrichtung erste und zweite Kryo-Pumpvorrichtungen umfassen.
Anspruch[en]
  1. A method of producing radioactive 125I, characterized by the steps of:
    • feeding 124Xe from a source thereof to an irradiation zone located within an enclosure,
    • irradiating said 124Xe in said enclosure with neutrons to cause the formation of 125Xe therefrom,
    • transferring irradiated gas by pumping from said irradiation zone to a decay zone located within said enclosure and free from neutron flux, and
    • permitting 125Xe to decay to form 125I in said decay zone.
  2. The method claimed in claim 1, wherein said feeding of 124Xe to said irradiation zone is effected by:
    • connecting said source of 124Xe to a feed inlet in selectable fluid flow communication with said irradiation zone and with a first condensation zone in said enclosure and flowing said 124Xe through said feed inlet,
    • condensing the feed 124Xe in said first condensation zone and closing said feed inlet, and
    • evaporating the liquid 124Xe from the first condensation zone to said irradiation zone.
  3. The method claimed in claim 1 or 2, wherein said irradiated gas transfer is effected by:
    • establishing fluid flow communication within said enclosure between said irradiation zone and said decay zone,
    • condensing irradiated gas flowing between said irradiation zone and said decay zone in a second condensation zone in said enclosure in fluid flow communication with said decay zone,
    • terminating fluid flow communication between said irradiation zone and said decay zone, and
    • evaporating condensed irradiated gas from said second condensation zone into said decay zone.
  4. The method claimed in any one of claims 1 to 3, wherein, following decaying of irradiated gas, the residual gas is transferred to said irradiation zone by:
    • establishing fluid flow communication within said enclosure between said decay zone and said irradiation zone and a first condensation zone within said enclosure,
    • condensing residual gas flowing between said decay zone and said irradiation zone in said first condensation zone in said enclosure,
    • terminating fluid flow communication between said irradiation zone and said decay zone, and
    • evaporating condensed gas from said first condensation zone into said irradiation zone, and
    • said steps of irradiating, transfer of irradiated gas and permitting decay are repeated.
  5. The method claimed in any one of claims 1 to 4, wherein said irradiation of 124Xe is effected by locating said enclosure submerged in the pool of a light water nuclear reactor adjacent to the reactor zone, and said decaying step is effected while maintaining said enclosure at a submerged location in said pool.
  6. The method as claimed in any one of claims 1 to 5, wherein, following formation of 125I, said decay zone is removed from said enclosure for the recovery of 125I therefrom.
  7. The method claimed in claim 6, wherein said 125I is removed from said decay zone by introducing an aqueous solvent for 125I to the decay zone, effecting a reflux of said aqueous solvent within said decay zone to remove solid 125I from internal surfaces of said decay zone and to form an aqueous solution of the iodine solution, and removing said aqueous solution from said decay zone.
  8. The method claimed in claim 7, wherein said aqueous solvent is an aqueous sodium hydroxide solution.
  9. An apparatus for producing radioactive 125I, characterized by:
    • a housing (12) which is gas-tight and submersible in a nuclear reactor water pool and defining an interior chamber, said housing having upper (16) and lower (14) separable portions to permit access to said interior chamber,
    • a first enclosure (18) within said chamber arranged to permit neutron irradiation of 124Xe gas contained therein by the nuclear reactor,
    • a second removable enclosure (20) within said chamber connected in interruptible fluid flow relationship with said first enclosure (18) for transfer of irradiated xenon gas from said first enclosure (18) to said second enclosure (20) to permit decay of 125Xe to 125I in said second enclosure (20) free from neutron flux,
    • said second enclosure (20) having valved inlet/outlet port means (33, 35, 37) to permit 124Xe to be received into said apparatus (10), to permit 125I solution to be discharged from said second enclosure (20), and to permit the passage of xenon gas between said first (18) and second (20) enclosures,
    • first pump means (32) operably connected to said first enclosure (18) for precipitating 124Xe received into said apparatus (10) through said valved port means (33, 35, 37) when said first (18) and second (20) enclosures are in fluid flow relationship and for providing gaseous xenon in said first enclosure (18) when said first (18) and second (20) enclosures are out of fluid flow relationship, and
    • second pump means (34) operably connected to said second enclosure (20) for precipitating irradiated xenon received from said first enclosure (18) when said first (18) and second (20) enclosures are in fluid flow relationship and for providing gaseous irradiated xenon in said second enclosure (20) when said first (18) and second (20) enclosures are out of fluid flow relationship.
  10. The apparatus claimed in claim 9, wherein said first (32) and second (34) pump means comprise first and second cryogenic pump means.
Anspruch[fr]
  1. Procédé de production de 125I radioactif, caractérisé par les étapes suivantes :
    • l'introduction de 124Xe à partir d'une source de celui-ci dans une zone d'irradiation placée à l'intérieur d'une enceinte,
    • l'irradiation de 124xe dans l'enceinte par des neutrons pour provoquer la formation de 125Xe,
    • le transfert du gaz irradié par pompage de la zone d'irradiation à une zone de désintégration placée dans l'enceinte et dépourvue de flux neutronique, et
    • la désintégration de 125Xe pour la formation de 125I dans la zone de désintégration.
  2. Procédé selon la revendication 1, dans lequel l'alimentation de la zone d'irradiation en 124Xe est réalisée par les opérations suivantes :
    • le raccordement de la source de 124Xe à une entrée d'alimentation en communication qui peut être sélectionnée pour la communication d'un fluide avec la zone d'irradiation et avec une première zone de condensation formée dans l'enceinte, et la circulation de 124Xe par cette entrée,
    • la condensation de 124Xe d'alimentation dans la première zone de condensation et la fermeture de l'entrée d'alimentation, et
    • l'évaporation de 124Xe liquide de la première zone de condensation vers la zone d'irradiation.
  3. Procédé selon la revendication 1 ou 2, dans lequel le transfert du gaz irradié est réalisé par les opérations suivantes :
    • l'établissement d'une communication pour le fluide à l'intérieur de l'enceinte entre la zone d'irradiation et la zone de désintégration,
    • la condensation du gaz irradié qui circule entre la zone d'irradiation et la zone de désintégration dans une seconde zone de condensation placée dans l'enceinte en communication avec la zone de désintégration pour la circulation d'un fluide,
    • la terminaison de la communication d'un fluide entre la zone d'irradiation et la zone de désintégration, et
    • l'évaporation du gaz irradié et condensé de la seconde zone de condensation vers la zone de désintégration.
  4. Procédé selon l'une quelconque des revendications 1 à 3, dans lequel, après la désintégration du gaz irradié, le gaz résiduel est transféré dans la zone d'irradiation par les étapes suivantes :
    • l'établissement d'une communication pour le fluide dans l'enceinte entre la zone de désintégration et la zone d'irradiation et une première zone de condensation dans l'enceinte,
    • la condensation du gaz résiduel circulant entre la zone de désintégration et la zone d'irradiation dans la première zone de condensation dans l'enceinte,
    • la terminaison de la communication entre la zone d'irradiation et la zone de désintégration pour un fluide, et
    • l'évaporation du gaz condensé de la première zone de condensation vers la zone d'irradiation, et
    • les étapes d'irradiation, de transfert du gaz irradié et de désintégration sont répétées.
  5. Procédé selon l'une quelconque des revendications 1 à 4, dans lequel l'irradiation de 124Xe est réalisée par disposition de l'enceinte afin qu'elle soit immergée dans la piscine d'un réacteur nucléaire à eau légère à proximité de la zone du réacteur, et l'étape de désintégration est réalisée avec maintien de l'enceinte à un emplacement immergé dans la piscine.
  6. Procédé selon l'une quelconque des revendications 1 à 5, dans lequel, après la formation de 125I, la zone de désintégration est retirée de l'enceinte pour la récupération de 125I.
  7. Procédé selon la revendication 6, dans lequel 125I est retiré de la zone de désintégration par introduction d'un solvant aqueux de 125I dans la zone de désintégration, par traitement au reflux du solvant aqueux dans la zone de désintégration afin que 125I solide soit retiré des surfaces internes de la zone de désintégration et qu'une solution aqueuse d'une solution d'iode soit formée, et l'extraction de la solution aqueuse de la zone de désintégration.
  8. Procédé selon la revendication 7, dans lequel le solvant aqueux est une solution aqueuse d'hydroxyde de sodium.
  9. Appareil de production de 125I radioactif, caractérisé par :
    • un boîtier (12) qui est hermétique et submersible dans une piscine d'eau d'un réacteur nucléaire et délimitant une chambre interne, le boîtier ayant des parties supérieure (16) et inférieure (14) qui sont séparables afin qu'elles donnent accès à la chambre interne,
    • une première enceinte (18) placée dans la chambre et destinée à permettre une irradiation neutronique de 124Xe gazeux contenu à l'intérieur par le réacteur nucléaire,
    • une seconde enceinte amovible (20) placée dans la chambre raccordée afin qu'elle permette une circulation sans interruption d'un fluide avec la première enceinte (18) pour le transfert du xénon gazeux irradié provenant de la première enceinte (18) vers la seconde enceinte (20) en permettant une désintégration de 125Xe en 125I dans la seconde enceinte (20) en l'absence d'un flux neutronique,
    • la seconde enceinte (20) ayant un dispositif à canal d'entrée-sortie (33, 35, 37) à soupape destiné à permettre la réception de 124Xe dans l'appareil (10), à permettre l'évacuation de la solution de 125I de la seconde enceinte (20) et à permettre le passage du xénon gazeux entre la première (18) et la seconde (20) enceinte,
    • un premier dispositif (32) à pompe raccordé pendant le fonctionnement à la première enceinte (18) et destiné à précipiter 124Xe reçu dans l'appareil (10) par l'intermédiaire du dispositif à canal (33, 35, 37) à vanne lorsque la première (18) et la seconde (20), enceinte sont en communication pour un fluide et afin que du xénon gazeux soit placé dans la première enceinte (18) lorsque la première (18) et la seconde (20) enceinte ne sont plus reliées pour la circulation d'un fluide, et
    • un second dispositif (34) à pompe raccordé pendant le fonctionnement à la seconde enceinte (20) et destiné à précipiter le xénon irradié reçu de la première enceinte (18) lorsque la première (18) et la seconde (20) enceinte sont en communication pour un fluide, et à transmettre du xénon irradié gazeux dans la seconde enceinte (20) lorsque la première (18) et la seconde (20) enceinte ne sont pas en position de communication d'un fluide.
  10. Appareil selon la revendication 9, dans lequel le premier dispositif (32) et le second dispositif (34) à pompe comportent une première et une seconde pompe cryogénique.






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