Method for producing a fraction of Xenon radioisotopes, in particular Xe-133, fraction of Xenon radioisotopes, in particular Xe-133

Abstract

A method for producing a fraction of xenon radioisotopes, comprising the steps of dissolving enriched uranium targets forming a slurry and a gaseous phase containing xenon radioisotopes, isolating the xenon radioisotopes using zeolite doped with silver, preferably chosen from the group consisting of aluminosilicates doped with silver, titanosilicates doped with silver and mixtures thereof, and recovering the fraction of xenon radioisotopes, in particular Xe-133.

Claims

1. A fraction of xenon radioisotopes, wherein the xenon radioisotopes are Xe-133, and wherein the fraction of xenon radioisotopes is a fraction of xenon isotopes recovered from a gas containing contaminants released from dissolution of low enriched uranium targets and having a radiochemical purity of medical use, in the form of a column of zeolite doped with silver, whereon said fraction of xenon radioisotopes is adsorbed, said column containing from 5 g to 10 g of zeolite doped with silver, and wherein the column is conditioned in a sealed and shielded container.

2. The fraction of xenon radioisotopes of claim 1, wherein the zeolite is a titanosilicate zeolite of the ETS type, doped with silver.

3. The fraction of xenon radioisotopes of claim 1, wherein the zeolite is an aluminosilicate zeolite of the chabazite type, doped with silver.

4. The fraction of xenon radioisotopes of claim 1, wherein zeolite doped with silver is a zeolite having an impregnation rate of silver Ag+ between 10% and 45% by weight with respect to the weight of said zeolite.

5. The fraction of xenon radioisotopes of claim 1, wherein the column comprises an inlet for a gas configured for being connected to a dissolver, said inlet being located under the zeolite doped with silver contained in the column, and an outlet for a gas configured for allowing a gas to exit the column in the form of a xenon radioisotope-depleted gaseous phase.

6. The fraction of xenon radioisotopes of claim 5, wherein the column further comprises a second outlet for a gas, said outlet connected to a bulb configured for recovery of the fraction of xenon radioisotopes.

7. The fraction of xenon radioisotopes of claim 1, wherein the fraction of xenon radioisotopes is produced by the steps of: (a) dissolving low-enriched uranium targets by contacting with base to provide an alkaline slurry and a gaseous phase containing xenon radioisotopes, (b) isolating the gaseous phase containing said xenon radioisotopes, and (c) recovering a fraction containing said xenon radioisotopes, wherein the isolation of the gaseous phase containing the xenon radioisotopes comprises a step of adsorbing xenon radioisotopes on a zeolite doped with silver.

8. The fraction of xenon radioisotopes of claim 7, wherein the steps further comprise a step of flushing said alkaline slurry with a rare gas making it possible to drive said gaseous phase containing said xenon radioisotopes for the purpose of isolating it.

9. The fraction of xenon radioisotopes of claim 7, wherein said recovery of a fraction containing said xenon radioisotopes is a step of hot desorbing of said xenon of said zeolite doped with silver.

10. The fraction of xenon radioisotopes according to claim 9, wherein said step of hot desorption is carried out at a temperature comprised between 150° C. and 200° C. or between 160° C. and 170° C.

11. The fraction of xenon radioisotopes of claim 7, wherein said step of adsorbing Xenon radioisotopes on a zeolite doped with silver is carried out at ambient temperature.

12. The fraction of xenon radioisotopes of claim 7, wherein said step of adsorbing xenon radioisotopes on a zeolite doped with silver is carried out at a flow rate of 50 to 400 litres/h, 80 to 120 litres/h, or 100 litres/hour.

13. The fraction of xenon radioisotopes of claim 7, wherein said zeolite doped with silver is contained in a column comprising an inlet and an outlet for a gas, said column comprising from 5 to 10 g of zeolite doped with silver, said inlet for a gas being connected to a dissolver wherein said alkaline dissolution takes place, said inlet for a gas of the column being located under the zeolite doped with silver, contained in the column, said outlet for a gas making possible the exiting from said gaseous phase outlet, said gaseous phase exiting said column in the form of a xenon radioisotope-depleted gaseous phase.

Description

(1) Other embodiments of the method according to the invention are described in the accompanying claims.

(2) The invention also has for object a fraction of xenon radioisotopes, in particular Xe-133 in the form of a column of zeolite doped with silver, conditioned in a sealed and shielded container whereon said fraction of xenon radioisotopes, in particular Xe-133 is adsorbed, said column containing from 5 to 100 g, preferably from 5 to 10 g of zeolite doped with silver.

(3) In a first advantageous embodiment of the fraction of xenon radioisotopes, in particular Xe-133 according to the present invention, said zeolite is an aluminosilicate zeolite of the chabazite type, doped with silver, available for example from the company Alberta Adsorbent Inc. (US).

(4) In a preferred mode of the present invention, said zeolite is a titanosilicate zeolite of the ETS type, preferably ETS-10, doped with silver available for example from the company Alberta Adsorbent Inc. (US).

(5) In a preferred mode of the present invention, said zeolite doped with silver is a zeolite presenting an impregnation rate of silver Ag.sup.+ between 10 and 45% by weight with respect to the weight of said zeolite

(6) In an advantageous alternative, the fraction of xenon radioisotopes, in particular Xe-133 is in the form of a sealed bulb, conditioned in a shielded container, containing said fraction of xenon radioisotopes, in particular Xe-133 in the form of gas.

(7) In yet another advantageous embodiment, said fraction of xenon radioisotopes, in particular Xe-133 is obtained by the method according to the invention.

(8) Other embodiments of the fraction according to the invention are described in the accompany claims.

(9) Other characteristics, details and advantages of the invention shall appear in the description provided hereinafter, in a non-limiting manner.

(10) When uranium 235 is bombarded with neutrons, it forms fission products that have a lower mass and which themselves are unstable. These products generate other radioisotopes via a disintegration cycle. It is especially in this way that the radioisotopes Mo-99, Xe-133 and I-131 are produced.

(11) The low-enriched uranium targets contain an aluminium alloy that contains uranium. The content in enriched uranium with respect to the total weight of uranium is a maximum of 20%, and typically of around 19%. The low-enriched uranium targets are dissolved during an alkaline dissolution phase in the presence of NaOH (at about 4 mol/l or more) and NaNO.sub.3 (at about 3.5 mol/l). During the dissolution, a slurry is formed as well as a gaseous phase of Xe-133. The slurry contains a solid phase mainly formed of uranium and of hydroxides of fission products and a liquid phase of molybdate (MoO.sub.4.sup.−) and of iodine 131 under iodine salts.

(12) The alkaline dissolution phase volume increases with the number of targets, given the very important content in product that cannot be used after dissolution of the targets. The dissolution of the aluminium of the target is an exothermic reaction.

(13) The gaseous phase of Xenon is recovered by isolation using a zeolite, in particular a zeolite doped with silver, preferably chosen from the group consisting of aluminosilicates doped with silver, titanosilicates doped with silver and of their mixtures.

(14) In a first advantageous embodiment of the method according to the present invention, said zeolite is an aluminosilicate zeolite of the chabazite type, doped with silver, available for example from the company Alberta Adsorbent Inc. (US).

(15) In another preferred embodiment of the present invention, said zeolite is a titanosilicate zeolite of the ETS type, preferably ETS-10, doped with silver available for example from the company Alberta Adsorbent Inc. (US).

(16) The zeolite doped with silver is more preferably a zeolite presenting an impregnation rate of silver Ag.sup.+ between 10 and 45% by weight with respect to the weight of said zeolite

(17) During the forming of the slurry, fission products of the uranium are released, certain in soluble forms, others in the form of gas. This is among other things the case with xenon and krypton, which are therefore in a gaseous phase. The gaseous phase exits the liquid medium and remains confined in the sealed container wherein the dissolution takes place. The sealed container comprises a gaseous phase outlet connected to a gaseous phase inlet of a column containing said zeolite doped with silver, isolated from the outside environment, but also an inlet for a purge gas.

(18) The gaseous phase contains ammonia (NH.sub.3) that comes from the reduction of the nitrates and the main gaseous fission products which are Xe-133 and Kr-85

(19) The dissolution is a highly exothermic reaction, which imposes two large refrigerants. However, water vapour is present in the gaseous phase. The gaseous phase is carried away by a vector gas (He or Ar) towards the device for recovering rare gases.

(20) The recovery of xenon is carried out as follows: the gaseous phase leaves the alkaline dissolution sealed container using a carrier gas and is brought to the column containing from 5 to 100 g, preferably from 5 to 10 g of zeolite doped with silver, arranged to collect a fraction of xenon radioisotopes, in particular Xe-133 from a single production. The adsorption of the xenon is carried out at ambient temperature. The flow rate of the supply of the column of zeolite is of about 100 litres/hour.

(21) In an advantageous alternative of the present invention, the method further comprises a step of closing off said column, of disconnecting said column from the dissolution circuit, as well as a conditioning of said column in a sealed and shielded container for the purpose of sending it to a customer.

(22) In another preferred embodiment of the method according to the present invention, said outlet for a gas comprises two outlets, a first allowing for the exiting of said xenon radioisotope-depleted gaseous phase, in particular Xe-133 and a second outlet, connected to a bulb intended to recover said fraction of xenon radioisotopes, in particular Xe-133.

(23) It is understood that the present invention is in no way limited to the embodiments described hereinabove and that many modifications can be made thereto without departing from the scope of the accompanying claims.