Classifications

• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
  • G21F9/04—Treating liquids
  • G21F9/06—Processing
  • G21F9/14—Processing by incineration; by calcination, e.g. desiccation
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
  • G21F9/28—Treating solids
  • G21F9/30—Processing
  • G21F9/301—Processing by fixation in stable solid media
  • G21F9/302—Processing by fixation in stable solid media in an inorganic matrix
  • G21F9/305—Glass or glass like matrix
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
  • G21F9/04—Treating liquids
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
  • G21F9/28—Treating solids
  • G21F9/30—Processing

Definitions

• the invention relates to a method for treating an aqueous nitrate liquid effluent containing nitrates of metals or metalloids, which comprises a calcination step generally followed by a vitrification step of the calcine obtained during said calcination step.
• the nitric aqueous liquid effluent may contain mainly sodium nitrate.
• the technical field of the invention can be defined generally as that of the calcination of liquid effluents, more particularly the technical field of the invention can be defined as the calcination of radioactive liquid effluents for their vitrification.
• the French vitrification process for radioactive liquid effluents comprises two steps.
• the first step is a step of calcining the effluent during which a drying and then a denitration of a portion of the nitrates takes place.
• the second step is a vitrification step by dissolving in a glass of containment the calcine produced during the calcination step.
• the calcination step is generally carried out in a rotary tube heated by an oven electric.
• the solid calcine is ground by an idle bar placed inside the rotating tube.
• the aluminum content in the glass must not be too high and is generally limited to about 15% by weight expressed as Al 2 O 3.
• This method of treating a nitric aqueous effluent by calcination must of course be able to be implemented reliably, reproducibly, regardless of the treated effluent and dilution adjuvant implemented.
• the object of the present invention is to provide a method for treating an aqueous nitrate liquid effluent containing nitrates of metals or metalloids, this process comprising a step of calcining the effluent to transform the nitrates of metals or metalloids into their oxides, which, among other things, meet the needs mentioned above.
• the object of the present invention is still to provide such a method which does not have the disadvantages, limitations, defects and disadvantages of the processes of the prior art and which solves the problems of the processes of the prior art, in particular with regard to the determination of the operating parameters of the process and the optimization of the amount of dilution adjuvant to be added to the effluent.
• a method of treating an aqueous nitrate liquid effluent containing nitrates of metals or metalloids comprising a step of calcining the effluent to transform the nitrates of metals or metalloids to oxides of metals or metalloids, at least one compound selected from nitrates of metals or metalloids and other compounds of the effluent resulting in calcination with a sticky oxide, and a dilution adjuvant comprising at least one metal or metalloid nitrate resulting in calcination with a non - sticky oxide being added to the effluent prior to the calcination step to give a mixture of effluent and dilution adjuvant, wherein mixture checks the two following inequations (I ' (2):
• the mass of all compounds in the mixture could possibly be simplified and replaced by the mass of all the salts of the mixture, including nitrates, expressed in terms of oxides.
• the denominator could be further possibly simplified in both inequations (1) and (2) and replaced by the mass of nitrates of the mixture, expressed in terms of oxides.
• the mass of all the compounds of the mixture leading, when calcined, to sticky oxides, expressed in terms of oxides could possibly be simplified and replaced by the mass of nitrates. and other compounds of the mixture which, upon calcination, are obtained with sticky oxides, expressed in terms of oxides, since the tacky compounds may generally comprise tacky nitrates and other tacky compounds or only other tacky compounds.
• the numerator could possibly be further simplified and replaced by the mass of nitrates in the mixture, which, when calcined, leads to sticky oxides, expressed in terms of oxides.
• the process according to the invention is fundamentally defined by the fact that the addition of the dilution adjuvant chosen from the nitrates of metals or metalloids leading during their calcination to so-called non-sticky oxides, is governed by both inequations (1) (2) mentioned above.
• the dilution adjuvant supply was such that both inequalities were verified, then the calcination of the effluent was possible without any the walls of the calciner, nor any clogging thereof.
• the simple application of this very simple criterion for the addition of the dilution adjuvant, based on the above inequalities, reliably avoids the calciner clogging phenomena.
• a single calcination test regardless of the effluent, makes it possible to optimize the characteristics of the calcine, in particular as regards its granulometry, by simply playing on the heating and on the content of calcination adjuvant, which is generally sugar.
• This simple, reliable criterion is of general application irrespective of the treated effluent generally containing mainly sodium nitrate and the nature of the other sticky and non-sticky compounds contained therein. This criterion also applies regardless of the nature and number of compounds, nitrates, added to the effluent as dilution adjuvants.
• the dilution adjuvant comprises aluminum nitrate and optionally at least one other nitrate of metal or metalloid, this (s) nitrate (s) leading during calcination to at least one non-sticky oxide.
• This at least one other metal or metalloid nitrate is generally selected from iron nitrate and rare earth nitrates.
• iron nitrate and rare earth nitrates have calcination bonding properties close to those of nitrate d aluminum, and that the oxides from these specific nitrates, which are so-called “non-sticky” oxides, can also dissolve in the final glass produced during the subsequent vitrification step.
• a dilution adjuvant preferably comprising a substitution of a portion of the aluminum nitrate, a nitrate selected from iron nitrate and rare earth nitrates thus makes it possible to avoid clogging of the tube of the calcination apparatus during the calcination of effluents generating very tacky oxides, such as solutions with a high sodium content, while minimizing the increase in the quantity of confining glass to be produced during the vitrification step which usually follows calcination.
• iron nitrate and rare earth nitrates have all the excellent properties of nitrate aluminum as to its ability to limit the bonding of calcine, and thus to prevent clogging of the calcination tube, while allowing to increase the rate of charge of the waste and thus to limit the amount of glass to produce.
• the constraints imposed on the glass formulation by the preferred dilution adjuvants according to the invention comprising a specific nitrate selected from iron nitrate and rare earth nitrates are significantly reduced compared to dilution adjuvants consisting solely of aluminum nitrate of made of the lower aluminum intake.
• Iron and rare earth nitrates thus provide an additional advantage during vitrification, in addition to the surprising effects and advantages due to the application according to the process of the invention of the criteria (1) (2) defined above. high.
• Rare earth nitrates are lanthanum nitrate, cerium nitrate, praseodymium nitrate, neodymium nitrate.
• the dilution adjuvant may thus comprise aluminum nitrate and optionally at least one other nitrate selected from iron nitrate, lanthanum nitrate, cerium nitrate, praseodymium nitrate and neodymium nitrate.
• each of the nitrates is free from the point of view of their effectiveness to prevent calcine sticking in the tube and can therefore be adjusted according to their impact on the properties of the confinement glass prepared in a subsequent vitrification step.
• the amount of dilution adjuvant added to the liquid effluent is determined by applying both inequations (1) and (2).
• the effluent is a nitric solution usually containing mainly sodium nitrate and other constituents such as nitrates
• the effluent may also contain "sticky” or “non-sticky” compounds which are not nitrates, generally present in the form of salts, such as phosphomolybdic acid which is a so-called “sticky” compound.
• the process according to the invention allows the calcination without clogging of all kinds of effluents, whatever their nature, and the nature of the nitrates and nitrates sticky contained therein.
• the liquid effluent treated by the process according to the invention contains at least one compound such as a metal or metalloid nitrate leading, during calcination, to a so-called “sticky” oxide, and / or at least one other compound which is not such a nitrate leading during calcination to a so-called "sticky” oxide.
• sticky compounds means compounds, oxides, nitrates known to stick to the walls of "calciner” calcination apparatus and induce clogging phenomena of these calcinators.
• the compound (s) such as the nitrate (s) and / or the other compound (s) which conduct (conduct) during calcination to an oxide (s) whether sticky (s) could they be sodium nitrate, phosphomolybdic acid or boron nitrate or mixtures thereof.
• the content of this or these compound (s) such as the "sticky” nitrate (s) and / or other "sticky” compounds in the effluent, expressed in oxides, relative to the mass total of nitrates contained in the effluent, also expressed in oxides, is generally greater than 35% by weight, or greater than 30% by weight for the sodium nitrate expressed in oxides.
• the process according to the invention makes it possible in particular to calcinate effluents with a high content of compounds such as nitrates and other so-called "sticky" compounds, ie greater than 35% by weight for all of the "sticky" nitrates, or greater than 30% by weight, for sodium nitrate.
• the process according to the invention allows the calcination of high sodium solutions which are very tacky.
• the effluent has a sodium nitrate content, expressed as sodium oxide, relative to the total mass of the nitrates (or possibly, more precisely , relative to the total mass of salts) contained in the effluent, expressed in oxides of greater than 30% by weight, preferably greater than 50% by weight.
• a single calcination test makes it possible to optimize the characteristics. calcinates by varying the heating of the different calciner zones, the calcination aid content (generally) and the rotational speed of the calciner tube.
• the conditions for calcination are generally as follows: temperature reached by the calcine of about 400 0 C.
• This calcination step is generally carried out in a heated rotating tube, preferably up to the desired temperature indicated above, for example by an electric furnace with several independent heating zones.
• Heating zones are more particularly dedicated to evaporation and others to calcination.
• the calcination zones make it possible to heat the calcine at the temperature of 400 ° C.
• the calcination step is carried out at a furnace calcine temperature of about 400 ° C.
• the treatment process according to the invention generally comprises, after the calcination step, a vitrification step of the calcine obtained during this calcination step.
• This vitrification step consists of a reaction between the calcine and a glass frit (preformed glass) to obtain a confinement glass.
• a vitrification step is performed which consists in developing a confinement glass from the melting of the calcine from the calcination step with glass frit.
• the implementation preferably in the dilution adjuvant of iron and rare earth-specific nitrates also advantageously makes it possible to relax the constraints with regard to the formulation of the glass.
• a higher proportion of effluent in the glass can be incorporated when the calcine was obtained using the dilution adjuvant according to the invention in place of a dilution adjuvant consisting solely of aluminum nitrate.
• the high intake of aluminum in the case of a dilution admixture consisting solely of aluminum nitrate tends to harden the calcine and has the consequence of causing a decrease in the reactivity between the calcine and the frit of glass in the vitrification furnace.
• Vitrification consists of a melting reaction between the calcine and the glass frit to form a confining glass. It is made in two types of ovens: indirect induction ovens which consists of heating by four inductors a metal pot into which the sintered / calcined mixture is introduced, and the direct induction furnaces which consist in heating the glass by an inductor through a cooled structure (cold crucible) which allows part of the electromagnetic field and in which is introduced continuously the sintered mixture / calcinate.
• indirect induction ovens which consists of heating by four inductors a metal pot into which the sintered / calcined mixture is introduced
• the direct induction furnaces which consist in heating the glass by an inductor through a cooled structure (cold crucible) which allows part of the electromagnetic field and in which is introduced continuously the sintered mixture / calcinate.
• Example 1 In this example, the calcination of an effluent containing a high content of sodium nitrate is described.
• composition of this effluent is given in Table 1, this composition being expressed in% by weight of the oxides corresponding to the salts contained in the effluent, which are nitrates.
• the percentage of oxides is expressed in relation to the total mass of the oxides corresponding to the salts contained in the effluent.
• the effluent described in Table 1 below is very charged especially in sodium and therefore very sticky.
• an adjuvant (adjuvant 1) is added to the effluent of Table 1 which consists of 100% by weight of aluminum nitrate, expressed as Al 2 O 3 oxide, at the rate of 95.05% by weight of adjuvant expressed as oxide for 100% in mass of effluent expressed in% by weight of the oxides corresponding to the salts contained in the effluent. It should be noted that the amount of adjuvant has been minimized by applying the criteria according to the invention.
• the conditions of calcination are as follows:
• the temperature reached by the calcine is about 400 ° C.
• the speed of rotation of the rotating tube containing the idler bar is 20 rpm
• the calcination aid content is 40 g / L of the effluent mixture with the dilution adjuvant.
• adjuvant 2 preferred according to the invention which consists of 75% by weight of aluminum nitrate expressed as Al 2 O 3 oxide and 25% by weight of iron nitrate expressed as Fe 2 O 3 oxide. This adjuvant is added in the same amount as the adjuvant 1 determined by the same calculations on the basis of the criteria according to the invention.
• Example 1 the vitrification of the calcine obtained in Example 1 is carried out.
• calcine was prepared using an adjuvant ("adjuvant No. 1") consisting solely of aluminum nitrate.
• adjuvant No. 1 consisting solely of aluminum nitrate.
• the range of glass composition that we were able to develop requires a maximum alumina content of 13% by weight in the glass.
• the glass is made from calcine and a glass frit containing 1% by weight of alumina.
• the vitrification was carried out in a cold crucible at 1230 ° C.
• Example 4 In this example, the vitrification of the calcine obtained in Example 2 is carried out. It should be remembered that this calcine was prepared using a preferred adjuvant ("adjuvant # 2") consisting of 75% by weight of sodium salt. aluminum and 25% by weight of iron salt.
• adjuvant # 2 a preferred adjuvant
• the high intake of aluminum by the adjuvant No. 1 tends to harden the calcine and results in a slight decrease in reactivity between the calcine and the glass frit in the vitrification furnace.
• a builder (adjuvant 1) of the prior art which consists of 100% by weight of aluminum nitrate expressed as Al 2 O 3 oxide.
• adjuvant 3 the adjuvant according to the invention in which part of the aluminum nitrate is replaced by nitrates of lanthanum, cerium, neodymium and praseodymium.
• the minimum content of dilution adjuvant to be added to this effluent consisting solely of sodium nitrate expressed as total oxide mass represents 70% in the mixture of the effluent with the dilution adjuvant.
• the conditions of calcination are as follows: Calcinator with two independent heating zones, the temperature reached by the calcine is approximately 400 ° C., the speed of rotation of the rotating tube containing the idler bar is 35 rpm, the calcination aid content is 20 g / L of the effluent mixture with the dilution adjuvant.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Catalysts (AREA)
• Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
• Glass Melting And Manufacturing (AREA)
• Removal Of Specific Substances (AREA)
• Treating Waste Gases (AREA)

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• 2008
  • 2008-12-30 FR FR0859138A patent/FR2940717B1/fr not_active Expired - Fee Related
• 2009
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  • 2009-12-23 RU RU2011131993/07A patent/RU2532413C2/ru active
  • 2009-12-23 ES ES09799361T patent/ES2414161T3/es active Active
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  • 2009-12-23 WO PCT/EP2009/067900 patent/WO2010076287A2/fr not_active Ceased
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