EP0195723A1 - Process and device for conditioning low and middle level radioactive waste solutions with hydraulic binders - Google Patents

Process and device for conditioning low and middle level radioactive waste solutions with hydraulic binders Download PDF

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Publication number
EP0195723A1
EP0195723A1 EP86400591A EP86400591A EP0195723A1 EP 0195723 A1 EP0195723 A1 EP 0195723A1 EP 86400591 A EP86400591 A EP 86400591A EP 86400591 A EP86400591 A EP 86400591A EP 0195723 A1 EP0195723 A1 EP 0195723A1
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EP
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Prior art keywords
volume
borate
crystals
tetrahydrate
calcium borate
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EP86400591A
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German (de)
French (fr)
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EP0195723B1 (en
Inventor
Claude Jaouen
Guy Magnin
Gérard Renault
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Societe Generale pour les Techniques Nouvelles SA SGN
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Societe Generale pour les Techniques Nouvelles SA SGN
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    • 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
    • G21F9/16—Processing by fixation in stable solid media
    • G21F9/162—Processing by fixation in stable solid media in an inorganic matrix, e.g. clays, zeolites
    • G21F9/165—Cement or cement-like matrix

Definitions

  • the present invention relates to a method and a device for the conditioning, by hydraulic binders, of radioactive effluents of low and medium activity.
  • the present invention relates to a particular mode of implementation of batch packaging systems, said mode of implementation being particularly suitable for the use of mobile and transportable stations.
  • the conditioning process according to the invention aims at conditioning, by hydraulic binders, borated radioactive effluents of low and medium activity by chemical pretreatment aiming at the preparation of crystals of calcium borate tetrahydrate, reduction of volume and kneading of the product obtained with at least one hydraulic binder, characterized in that: - said calcium borate tetrahydrate is produced by adding, to the solution to be treated, an amount of lime calculated so as to form borate B203Ca0; the volume reduction operation is carried out by evaporation, under reduced pressure, of the solutions and / or suspensions, said reduced pressure being between approximately 0.1 and 0.3 bar and applied after the phase of preparation of the borate crystals calcium tetrahydrate; - And that said reduction in volume is carried out until the end of the process, a concrete suspension containing from about 30 to about 70% of dry matter.
  • the mixture obtained at the end of crystallization can contain calcium borates having several stages of hydration. This is why, when in the present application, it is indicated that calcium borate tetrahydrate is prepared, it should be understood that the aim will be to prepare this product which proves to be more stable during packaging and in the normal conditions of storage of the packaged product, but that other calcium borates (for example 2.6 or 9 molecules of water) may be present. However, in general, we manage to prepare a mixture of calcium borates in which the borate tetrahydrate represents at least 90% of the borates.
  • volume reduction operation by vacuum evaporation can take place (and preferably takes place to achieve maximum time savings) during the fourth stage of precipitation. It was also indicated that this same operation could take place, if necessary, during the first stage of precipitation, and this is done when the effluents are diluted.
  • volume reduction operation can also take place before the crystallization operation begins and must continue after the fourth stage of the crystallization operation in order to obtain the best reduction in volume. It should indeed be remembered that an aqueous mixture containing between 30 and 70% of dry extract is subjected to concreting (addition of cement).
  • This type of equipment is marketed for example by the company GUEDU (France), the mixing principle used in the corresponding mixer-dryers having been applied to the pharmaceutical and fine chemical industry (mixing, chemical treatments, evaporation under vacuum) as in the field of civil engineering for many years.
  • GUEDU France
  • the mixing principle used in the corresponding mixer-dryers having been applied to the pharmaceutical and fine chemical industry (mixing, chemical treatments, evaporation under vacuum) as in the field of civil engineering for many years.
  • the paste obtained at the end of the volume reduction operation by evaporation under reduced pressure is kneaded, after cooling, with a hydraulic binder. lique. Said paste could previously have been fluidized, either by acidification to pH ⁇ 10, or by addition of a fluidizer, or by addition of an untreated effluent.
  • composition of the concrete obtained (solid / water / binder) is fixed by the following specifications, for a given hydraulic binder: consistency (function of the quantity of liquid in the paste) and mechanical resistance (function of the binder / water ratio).
  • consistency function of the quantity of liquid in the paste
  • mechanical resistance function of the binder / water ratio
  • a mobile conditioning station is equipped with a GUEDU type 2500 mixer drier, with a useful capacity of approximately 1600 1 and of approximately 10 m 2 of total exchange surface.
  • the evaporative capacity under the conditions of use of the process is of the order of 80 kg / h.
  • the precipitation reaction is carried out overall in 5 h, the speed of rotation of the mixer being controlled by the measurement of a viscometer with vibrating needle.
  • the result is a suspension of insoluble calcium borates, mainly in the form of CaO, B 2 O 3 , 6 H 2 0, the reaction yield being 85%.
  • the dry extract at 60 ° C of the solution obtained is approximately 32%.
  • the suspension obtained above is then overconcentrated under an absolute pressure of 0.25 bar, at around 60 ° C., to a dry extract of 45%.
  • the main result is the tetrahydrate CaO, B203, 4 H 2 0 which is stable.
  • the operation takes around 7 hours.
  • CLK cement is added, such that the free water / cement ratio is 1.45.
  • 1160 1 of concrete with density 1.625 are obtained.
  • the total duration of the operating cycle is approximately 13 h. Volume reduction: 1.38 (effluent volume / concrete volume). Processing of the annual production of a section: 20 hours (in equivalent).
  • a GUEDU 2500 1600 l of initial solution is supplied, and it is concentrated by evaporation under vacuum up to 240 g / 1, under a pressure of 0.1 bar absolute, gradually feeding the initial solution so as to maintain the volume constant.
  • the evaporative capacity under these conditions is 120 kg / h. After treatment with 3200 l of initial solution, 1600 l of solution containing 240 g / l of boric acid are obtained, the operation lasting approximately 14 hours.
  • Example 2 The concentrated solution obtained is then treated as in Example 1.
  • the total duration of an operating cycle is of the order of 27 hours.
  • Boric acid is treated at 120 g / l.
  • An installation comprising two GUEDU mixer-dryers : a type 2500, with capacity 1600 1 and exchange surface 10 m 2 , and a type 820, with capacity 500 1, with exchange surface 5 m 2 .
  • phase P1 of the pretreatment and the evaporation are carried out simultaneously under an absolute pressure of 0.25 bar.
  • the evaporative capacity under these conditions is approximately 90 kg / h.
  • This phase lasts approximately 2 h 40 min.
  • the evaporation is then stopped during phase P2 of the pretreatment, ie approximately 2.5 h, then the concentration of the pretreated solution is resumed, under a pressure of 0.1 bar, until obtaining approximately 500 l of concentrated suspension, containing the equivalent of 384 g / l of boric acid, ie a dry extract of approximately 51%
  • This last operation lasts approximately 12 h, or an overall time of this first cycle of 5 p.m.
  • the concentrated solution is then transferred to the GUEDU 820, the evaporating capacity of which will be of the order of 40 l / h.
  • the over-concentration to a dry extract of 56%. The operation lasts approximately 1 hour 30 minutes.
  • the over-concentrated paste is then acidified to P H 8.

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  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Processing Of Solid Wastes (AREA)

Abstract

1. A process for encapsulating low- and medium-level radio-active waste containing borates, by hydraulic cements, by chemical treatment with a view to the preparation of crystals of tetrahydrated calcium borate, reduction in volume and mixing of the product obtained with at least one hydraulic cement, characterized in that : - said tetrahydrated calcium borate is produced by adding to the solution to be treated a quantity of lime calculated so as to form the borate B2 O3 CaO ; - the operation of volume reduction is carried out by evaporation, under reduced pressure, of the solutions and/or suspensions, said reduced pressure being between about 0.1 and 0.3-10**5 Pa bar and applied after the phase of preparation of the crystals of tetrahydrated calcium borate ; - and in that said volume reduction is continued until a concretable suspension is obtained at the end of the process, which contains from about 30 to about 70% of dry matter.

Description

La présente invention concerne un procédé et un dispositif pour le conditionnement, par liants hydrauliques, d'effluents radioactifs de faible et de moyenne activité.The present invention relates to a method and a device for the conditioning, by hydraulic binders, of radioactive effluents of low and medium activity.

Le conditionnement par liants hydrauliques des effluents radioactifs de faible et moyenne activité est pratiqué depuis longtemps dans l'industrie nucléaire, du fait de la simplicité couramment admise des procédés correspondants, et du faible coût du matériau enrobant.The conditioning by hydraulic binders of radioactive effluents of low and medium activity has been practiced for a long time in the nuclear industry, due to the commonly accepted simplicity of the corresponding processes, and the low cost of the coating material.

On rappelle qu'un tel conditionnement doit permettre de fabriquer, à partir d'un effluent chimique donné, un béton stockable dans un milieu et un contexte réglementaire donnés, ladite fabrication devant avoir lieu dans un contexte nucléaire et au moindre coût. Les procédés connus pour réaliser un tel conditionnement comportent en général les étapes suivantes :

  • - un prétraitement chimique faisant passer l'effluent radioactif à conditionner sous une forme bétonnable (solide dispersé dans une phase aqueuse)
  • - une réduction de volume du produit traité
  • - et un malaxage du produit obtenu avec une quantité adéquate de liant pour obtenir le béton.
It is recalled that such conditioning must make it possible to manufacture, from a given chemical effluent, a concrete that can be stored in a given environment and regulatory context, said manufacturing having to take place in a nuclear context and at the lowest cost. The known methods for producing such packaging generally include the following steps:
  • - a chemical pretreatment passing the radioactive effluent to be conditioned in a concrete form (solid dispersed in an aqueous phase)
  • - a reduction in the volume of the product treated
  • - and mixing the product obtained with an adequate quantity of binder to obtain the concrete.

Pour le traitement des effluents boratés, notamment provenant des centrales PWR ; on a déjà préconisé

  • - un système continu basé sur une réduction de volume par évaporation à pression atmosphérique et l'utilisation de mata- xeurs horizontaux ; un tel système est particulièrement adapté aux fortes capacités et aux activités importantes ;
  • - un système discontinu dans lequel la réduction de volume s'effectue par combinaison d'une séparation liquide/solide et une évaporation de la phase liquide, et l'utilisation de malaxeurs industriels à axes verticaux; un tel système est plus particulièrement adapté au traitement des solutions diluées dans des installations fixes.
For the treatment of borated effluents, especially from PWR plants; we have already recommended
  • - a continuous system based on a reduction in volume by evaporation at atmospheric pressure and the use of horizontal mixers; such a system is particularly suitable for high capacities and important activities;
  • - a discontinuous system in which the volume reduction takes place by combination of a liquid / solid separation and an evaporation of the liquid phase, and the use of industrial mixers with vertical axes; such a system is more particularly suited to the treatment of diluted solutions in fixed installations.

La présente invention concerne un mode particulier de mise en oeuvre des systèmes de conditionnement en discontinu, ledit mode de mise en oeuvre étant particulièrement adapté à l'utilisation de stations mobiles et transportables.The present invention relates to a particular mode of implementation of batch packaging systems, said mode of implementation being particularly suitable for the use of mobile and transportable stations.

Le procédé de conditionnement selon l'invention vise au conditionnement, par liants hydrauliques, d'effluents radioactifs boratés de faible et moyenne activité par prétraitement chimique visant à la préparation de cristaux de borate de calcium tétrahydraté, réduction de volume et malaxage du produit obtenu avec au moins un liant hydraulique, caractérisé en ce que : - ledit borate de calcium tétrahydraté est réalisé en ajoutant, à la solution à traiter, une quantité de chaux calculée de façon à former le borate B203Ca0 ; - l'opération de réduction de volume est réalisée par évaporation, sous pression réduite, des solutions et/ou suspensions, ladite pression réduite étant comprise entre 0,1 et 0,3 bar environ et appliquée après la phase de préparation des cristaux de borate de calcium tétrahydraté ; - et que ladite réduction de volume est menée à bien jusqu'à l'obtention, en fin de procédé, d'une suspension bétonnable contenant d'environ 30 à environ 70 Z de matière sèche.The conditioning process according to the invention aims at conditioning, by hydraulic binders, borated radioactive effluents of low and medium activity by chemical pretreatment aiming at the preparation of crystals of calcium borate tetrahydrate, reduction of volume and kneading of the product obtained with at least one hydraulic binder, characterized in that: - said calcium borate tetrahydrate is produced by adding, to the solution to be treated, an amount of lime calculated so as to form borate B203Ca0; the volume reduction operation is carried out by evaporation, under reduced pressure, of the solutions and / or suspensions, said reduced pressure being between approximately 0.1 and 0.3 bar and applied after the phase of preparation of the borate crystals calcium tetrahydrate; - And that said reduction in volume is carried out until the end of the process, a concrete suspension containing from about 30 to about 70% of dry matter.

Le prétraitement mis en oeuvre dans l'invention est connu dans son principe puisqu'il consiste, après une éventuelle neutralisation de l'effluent de façon à amener le rapport molaire Na/B à être voisin de 0,25 , à ajouter de la chaux (sous forme solide ou en solution) de façon à viser la précipitation ultérieure du B203Ca04H20. On sait que la précipitation de ce borate de calcium s'effectue en quatre étapes :

  • - la première consiste, après l'adjonction de chaux, dans la formation, à une température de l'ordre de 60°C, de germes de sels de calcium ; au cours de cette étape le mélange conserve sensiblement une viscosité constante ;
  • - la seconde qui succède à la première, et qui se déroule à la même température, consiste dans la formation de sels mixtes ce qui se traduit par une augmentation progressive notable de la viscosité du mélange.
  • - la troisième, qui succède à la seconde, consiste dans la formation, à une température de l'ordre de 40-50°C, de cristaux de borate de calcium à 4H2O; cette formation de cristaux se traduit par une diminution de la viscosité du mélange (P2)
  • - la quatrième, qui succède à la troisième, consiste dans le mûrissement des cristaux formés; ce mûrissement réalisé également à une température de 40-50°C est constitué en fait par un grossissement progressif des cristaux (P 3).
The pretreatment used in the invention is known in principle since it consists, after possible neutralization of the effluent so as to cause the Na / B molar ratio to be close to 0.25, to add lime (in solid form or in solution) so as to target the subsequent precipitation of B203Ca04H20. We know that the precipitation of this calcium borate takes place in four stages:
  • - the first consists, after the addition of lime, in the formation, at a temperature of about 60 ° C, of calcium salt germs; during this stage the mixture substantially retains a constant viscosity;
  • - The second which follows the first, and which takes place at the same temperature, consists in the formation of mixed salts which results in a notable progressive increase in the viscosity of the mixture.
  • - The third, which follows the second, consists in the formation, at a temperature of about 40-50 ° C, crystals of calcium borate at 4H 2 O; this crystal formation results in a decrease in the viscosity of the mixture (P 2 )
  • - the fourth, which follows the third, consists in the ripening of the crystals formed; this ripening also carried out at a temperature of 40-50 ° C is in fact constituted by a gradual magnification of the crystals (P 3).

Il a été trouvé et cela constitue un autre aspect de la présente invention

  • - d'une part que l'opération de réduction de volume du mélange par évaporation sous pression réduite ne pouvait en aucun cas être réalisée pendant les seconde et troisième étapes de la précipitation du borate de calcium; ladite réduction de volume ne pourra donc intervenir, à ce stade du procédé de conditionnement, que pendant la première et/ou quatrième étape de l'opération de précipitation.
  • - et d'autre part, que l'on pouvait, pour gagner du temps, obtenir la formation du borate de calcium tétrahydraté en passant par l'intermédiaire du borate de calcium hexahydraté; pour ce faire la troisième étape de la précipitation est réalisée à une température comprise entre 10 et 30°C et ce n'est qu'ensuite (quatrième étape) que la température du mélange est portée à 40-50°C; dans ce cas il y aura simultanément, dans cette quatrième étape, formation du borate de calcium tétrahydraté à partir du borate de calcium hexahydraté, grossissement des cristaux du borate de calcium tétrahydraté et,de préférence, réduction du volume du mélange par évaporation sous pression réduite.
It has been found and this constitutes another aspect of the present invention
  • on the one hand, that the operation of reducing the volume of the mixture by evaporation under reduced pressure could in no case be carried out during the second and third stages of the precipitation of calcium borate; said reduction in volume can therefore occur, at this stage of the packaging process, only during the first and / or fourth stage of the precipitation operation.
  • - And secondly, that one could, to save time, obtain the formation of calcium borate tetrahydrate by passing through calcium borate hexahydrate; to do this, the third stage of precipitation is carried out at a temperature between 10 and 30 ° C and it is only then (fourth stage) that the temperature of the mixture is brought to 40-50 ° C; in this case there will be simultaneously, in this fourth step, formation of calcium borate tetrahydrate from calcium borate hexahydrate, magnification of the crystals of calcium borate tetrahydrate and, preferably, reduction of the volume of the mixture by evaporation under reduced pressure .

Par les explications qui prédèdent, on comprend que le mélange obtenu en fin de cristallisation peut comporter des borates de calcium présentant plusieurs stades d'hydratation. C'est pourquoi, lorsque dans la présente demande,on indique que l'on prépare du borate de calcium tétrahydraté, il faut comprendre que l'on visera à la préparation de ce produit qui se révèle e plus stable lors du conditionnement et dans les conditions normales de stockage du produit conditionné, mais que d'autres borates de calcium (par exemple à 2,6 ou 9 molécules d'eau) peuvent être présents. On arrive cependant, d'une façon générale, à préparer un mélange de borates de calcium dans lequel le borate tétrahydraté représente au moins 90% des borates.By the foregoing explanations, it is understood that the mixture obtained at the end of crystallization can contain calcium borates having several stages of hydration. This is why, when in the present application, it is indicated that calcium borate tetrahydrate is prepared, it should be understood that the aim will be to prepare this product which proves to be more stable during packaging and in the normal conditions of storage of the packaged product, but that other calcium borates (for example 2.6 or 9 molecules of water) may be present. However, in general, we manage to prepare a mixture of calcium borates in which the borate tetrahydrate represents at least 90% of the borates.

On a vu que l'opération de réduction de volume par évaporation sous vide pouvait avoir lieu, (et avait lieu de préférence pour réaliser un maximum de gain de temps) pendant la quatrième étape de la précipitation. On a indiqué également que cette même opération pouvait avoir lieu, si nécessaire, pendant la première étape de la précipitation,et ceci est réalisé lorsque les effluents sont dilués.We have seen that the volume reduction operation by vacuum evaporation can take place (and preferably takes place to achieve maximum time savings) during the fourth stage of precipitation. It was also indicated that this same operation could take place, if necessary, during the first stage of precipitation, and this is done when the effluents are diluted.

Mais l'opération de réduction de volume peut également avoir lieu avant que ne commence l'opération de cristallisation et doit se poursuivre après la quatrième étape de L'opération de cristallisation pour obtenir La meiLLeure réduction de volume. IL convient en effet de se rappeler que L'on soumet au bétonnage (adjonction de ciment) un métange aqueux contenant entre 30 et 70 X d'extrait sec.However, the volume reduction operation can also take place before the crystallization operation begins and must continue after the fourth stage of the crystallization operation in order to obtain the best reduction in volume. It should indeed be remembered that an aqueous mixture containing between 30 and 70% of dry extract is subjected to concreting (addition of cement).

Compte tenu de cet objectif et des divers stades auxquels on peut appliquer l'opération de réduction de volume par évaporation sous pression réduite,on peut énoncer les règles et possibilités suivantes:

  • 1. si l'effluent de départ a une concentration en acide borique correspondant à environ 200 à 250 g/1; il est possible de ne pas effectuer de réduction de volume avant la quatrième étape de l'opération de cristallisation. La mise sous pression réduite du mélange aux fins de réduction de volume, sera donc réalisée seulement au cours de ladite quatrième étape et pourra être prolongée au-delà de ladite étape si nécessaire.
  • 2. si l'effluent de départ a une concentration en acide borique inférieure à environ 200g/1, l'expérience a montré qu'il est alors souhaitable d'effectuer également une réduction du volume durant la première phase de l'opération de cristallisation et/ou avant ladite première phase. Cette réduction de volume peut en effet être entreprise sur la solution (ou suspension) d'effluent reçue, avant toute addition de chaux audit effluent, l'avantage d'opérer cette réduction de volume à ce moment du procedé est que l'on peut réduire La pression sur un Liquide chauffé à une température supérieure à 60°C.
Given this objective and the various stages to which the operation of volume reduction by evaporation under reduced pressure can be applied, the following rules and possibilities can be stated:
  • 1. if the initial effluent has a boric acid concentration corresponding to approximately 200 to 250 g / l; it is possible not to carry out a volume reduction before the fourth stage of the crystallization operation. Reducing the mixture under reduced pressure for the purpose of reducing volume will therefore be carried out only during the said fourth stage and may be extended beyond the said stage if necessary.
  • 2. if the initial effluent has a boric acid concentration of less than about 200 g / l, experience has shown that it is then desirable to also carry out a reduction in volume during the first phase of the crystallization operation and / or before said first phase. This reduction in volume can indeed be undertaken on the solution (or suspension) of effluent received, before any addition of lime to said effluent, the advantage of effecting this reduction in volume at this time of the process is that one can reduce The pressure on a Liquid heated to a temperature above 60 ° C.

Dans tous les cas, et quelle que soit la phase de traitement ou la réduction de volume est effectuée, il est entendu que cette réduction est réalisée par mise de la solution ou de la suspension à une pression comprise entre 0,1 et 0,3 bar à la température de ladite solution ou suspension à ladite phase. On conçoit aisément qu'en utilisant l'invention il est possible

  • - soit de viser la préparation d'une suspension bétonnable à environ 30% en poids de matière sèche
  • - soit de viser la préparation d'une suspension bétonnable contenant jusau'à environ 70% en poids de matière sèche,ce qui donnera naissance à un volume de béton inférieur.
In all cases, and whatever the treatment phase or the volume reduction is carried out, it is understood that this reduction is carried out by placing the solution or the suspension at a pressure of between 0.1 and 0.3 bar at the temperature of said solution or suspension in said phase. It is easily understood that by using the invention it is possible
  • - either to aim at the preparation of a concrete suspension at about 30% by weight of dry matter
  • - Either to target the preparation of a concrete suspension containing up to about 70% by weight of dry matter, which will give rise to a lower volume of concrete.

Un avantage essentiel de l'invention est que toutes les opérations peuvent être réalisées dans un seul appareil et éventuellement pour des questions de commodités et de volumes traités dans deux appareils de même type à condition d'utiliser un mélangeur-malaxeur-évaporateur qui soit pourvu:

  • - d'un dispositif (double enveloppe par exemple) de maintien de la température du produit à traiter à une valeur déterminée à l'avance entre 10 et 1000C environ.
  • - d'un agitateur efficace présentant de préférence plusieurs régimes d'agitation et qui puisse être utilisé avec des fluides (ou suspensions) de viscosités très nettement différentes(ces viscosités différentes étant rencontrées dans la période de cristallisation et dans la période de bétonnage)
  • - et d'un dispositif permettant de réaliser dans l'appareil une pression réduite allant de 0,1 à 1 bar. Il est clair, en effet, que, si lopé- tion de réduction de volume est réalisée en amenant la pression à être comprise entre environ 0,1 et environ 0,3 bar, il est possible et parfois souhaitable, pour des raisons de confinement,de réaliser tout ou partie des autres opérations en opérant sous une légère dépression, par exemple à 0,7 ou 0,9 bar.
An essential advantage of the invention is that all the operations can be carried out in a single device and possibly for reasons of convenience. and volumes treated in two devices of the same type provided that a mixer-kneader-evaporator is used which is provided with:
  • - a device (double jacket for example) for maintaining the temperature of the product to be treated at a value determined in advance between 10 and 100 ° C. approximately.
  • - an efficient agitator preferably having several stirring regimes and which can be used with fluids (or suspensions) of very clearly different viscosities (these different viscosities being encountered in the crystallization period and in the concreting period)
  • - And a device allowing to realize in the device a reduced pressure going from 0.1 to 1 bar. It is clear, in fact, that, if the volume reduction operation is carried out by bringing the pressure to be between approximately 0.1 and approximately 0.3 bar, it is possible and sometimes desirable, for reasons of confinement , to carry out all or part of the other operations by operating under a slight depression, for example at 0.7 or 0.9 bar.

Ce type d'appareillage est commercialisé par exemple par la Société GUEDU (France), le principe de malaxage utilisé dans les mélangeurs-sécheurs correspondants ayant été appliqué à l'industrie pharmaceutique et de chimie fine (malaxage, traitements chimiques, évaporation sous vide) comme au domaine du génie civil depuis de nombreuses années.This type of equipment is marketed for example by the company GUEDU (France), the mixing principle used in the corresponding mixer-dryers having been applied to the pharmaceutical and fine chemical industry (mixing, chemical treatments, evaporation under vacuum) as in the field of civil engineering for many years.

La pâte obtenueà la fin de l'opération de réduction du volume par évaporation sous pression réduite, est malaxée, après refroidissement, avec un liant hydraulique. Ladite pâte aura pu antérieurement être fluidifiée, soit par acidification à pH<10, soit par ajout d'un fluidifiant,soit par ajout d'un effluent non traité.The paste obtained at the end of the volume reduction operation by evaporation under reduced pressure is kneaded, after cooling, with a hydraulic binder. lique. Said paste could previously have been fluidized, either by acidification to pH <10, or by addition of a fluidizer, or by addition of an untreated effluent.

La composition du béton obtenu (solide/eau/ liant) est fixée par les spécifications suivantes, pour un liant hydraulique donné : consistance (fonction de la quantité de liquide dans la pâte) et résistance mécanique (fonction du rapport liant/eau). L'extrait sec de la pâte surconcentrée (solide (solide+eau) est donc fixé par ces deux critères, et donnera le volume de condensats à obtenir.The composition of the concrete obtained (solid / water / binder) is fixed by the following specifications, for a given hydraulic binder: consistency (function of the quantity of liquid in the paste) and mechanical resistance (function of the binder / water ratio). The dry extract of the over-concentrated paste (solid (solid + water) is therefore fixed by these two criteria, and will give the volume of condensate to be obtained.

Le type de liant à utiliser sera fonction des spécifications sur le produit final et sera couramment:

  • - du ciment Portland
  • - du ciment à base de laitier de haut fourneau
  • - du ciment à ajouts semi-liants (pouzzolanes, cendres volantes...)
The type of binder to be used will depend on the specifications on the final product and will commonly be:
  • - Portland cement
  • - cement based on blast furnace slag
  • - cement with semi-binding additions (pozzolans, fly ash ...)

Les performances typiques éprouvées tant à l'échelle laboratoire qu'à l'échelle pilote, en inactif ou en actif, sont les suivantes :

  • Réduction de volume
The typical performances tested both on the laboratory scale and on the pilot scale, inactive or active, are the following:
  • Volume reduction

Jusqu'à 420 g H3BO3 par litre de béton, soit une réduction de volume(effluent/bêton) de 3,5 pour un effluent initial à 21.000 ppm de bore. Qualité de l'enrobé (sur la base de 420 g H3B03/1 béton) . résistance à la compression >200 bars après 28 jours de temps de cure en air humide . résistance à l'eau : après 3 mois d'immersion, pas de modification de la résistance mécanique, variation volumique <1% . lixiviation : Co 60 : <10-6 cm/jour <10-4 cm/jourUp to 420 g H 3 BO 3 per liter of concrete, i.e. a reduction in volume (effluent / concrete) of 3.5 for an initial effluent at 21,000 ppm of boron. Quality of the mix (based on 420 g H 3 B0 3/1 concrete). compressive strength> 200 bars after 28 days of curing time in humid air. water resistance: after 3 months of immersion, no change in mechanical resistance, volume change <1%. leaching: Co 60: <10 -6 cm / day <10 -4 cm / day

Les exemples non limitatifs suivants illustrent l'invention.The following nonlimiting examples illustrate the invention.

EXEMPLE 1EXAMPLE 1

On traite de l'acide borique neutralisé à la soude, dans un rapport molaire Na/B = 0,26, et à 240 g/1 en acide borique. On suppose que la production de concentrats pour une tranche PWR 900 MWe est de 2,5 m3/an.Boric acid neutralized with sodium hydroxide, in an Na / B molar ratio = 0.26, and 240 g / l in boric acid is treated. It is assumed that the production of concentrates for a PWR 900 MWe unit is 2.5 m 3 / year.

Une station mobile de conditionnement est équipée d'un malaxeur sécheur GUEDU type 2500, de capacité utile 1600 1 environ et de 10 m2 environ de surface totale d'échange.A mobile conditioning station is equipped with a GUEDU type 2500 mixer drier, with a useful capacity of approximately 1600 1 and of approximately 10 m 2 of total exchange surface.

La capacité évaporatoire dans les conditions d'utilisation du procédé est de l'ordre de 80 kg/h. On alimente 1,6 m3 d'effluent boraté dans l'appareil, puis on introduit la chaux, dans un rapport molaire Ca/B = 0,5. La réaction de précipitation est effectuée globalement en 5 h, la vitesse de rotation du malaxeur étant asservie à la mesure d'un viscosimètre à aiguille vibrante. On aboutit à une suspension de borates de calcium insolubles, principalement sous forme CaO, B2O3, 6H20, le rendement de la réaction étant de 85%. L'extrait sec à 60°C de la solution obtenue est de 32% environ.The evaporative capacity under the conditions of use of the process is of the order of 80 kg / h. 1.6 m 3 of borated effluent are fed into the apparatus, then lime is introduced, in a Ca / B molar ratio = 0.5. The precipitation reaction is carried out overall in 5 h, the speed of rotation of the mixer being controlled by the measurement of a viscometer with vibrating needle. The result is a suspension of insoluble calcium borates, mainly in the form of CaO, B 2 O 3 , 6 H 2 0, the reaction yield being 85%. The dry extract at 60 ° C of the solution obtained is approximately 32%.

On surconcentre ensuite sous une pression absolue de 0,25 bar, à environ 60°C la suspension obtenue précédemment jusqu'à un extrait sec de 45%. On obtient principalement le tétrahydrate CaO, B203, 4H20 qui est stable. L'opération dure environ 7 heures. On ajoute ensuite, après refroidissement, du ciment CLK, tel que le rapport eau libre/ciment soit de 1,45. On obtient après 10 min de malaxage 1160 1 de béton de densité 1,625.The suspension obtained above is then overconcentrated under an absolute pressure of 0.25 bar, at around 60 ° C., to a dry extract of 45%. The main result is the tetrahydrate CaO, B203, 4 H 2 0 which is stable. The operation takes around 7 hours. Then, after cooling, CLK cement is added, such that the free water / cement ratio is 1.45. After 10 min of kneading, 1160 1 of concrete with density 1.625 are obtained.

La durée totale du cycle opératoire est d'environ 13 h. Réduction de volume: 1,38 (volume effluent/volume béton). Traitement de la production annuelle d'une tranche : 20 heures (en équivalent).The total duration of the operating cycle is approximately 13 h. Volume reduction: 1.38 (effluent volume / concrete volume). Processing of the annual production of a section: 20 hours (in equivalent).

EXEMPLE 2EXAMPLE 2

On traite de l'acide borique neutralisé à la soude, dans un rapport molaire Na/B = 0,25 et à 120 g/1 en acide borique.Boric acid neutralized with sodium hydroxide is treated in a Na / B molar ratio = 0.25 and at 120 g / l as boric acid.

Dans un GUEDU 2500, on alimente 1600 1 de solution initiale, et on concentre par évaporation sous vide jusqu'à 240 g/1, sous une pression de 0,1 bar absolu, en alimentant progressivement la solution initiale de manière à maintenir le volume constant.In a GUEDU 2500, 1600 l of initial solution is supplied, and it is concentrated by evaporation under vacuum up to 240 g / 1, under a pressure of 0.1 bar absolute, gradually feeding the initial solution so as to maintain the volume constant.

La capacité évaporatoire dans ces conditions est de 120 kg/h. On obtient, après traitement de 3200 1 de solution initiale, 1600 1 de solution à 240 g/1 d'acide borique, l'opération durant environ 14 heures.The evaporative capacity under these conditions is 120 kg / h. After treatment with 3200 l of initial solution, 1600 l of solution containing 240 g / l of boric acid are obtained, the operation lasting approximately 14 hours.

La solution concentré obtenue est ensuite traitée comme dans l'exemple 1. Dans ce deuxième exemple, la durée totale d'un cycle opératoire est de l'ordre de 27 heures.The concentrated solution obtained is then treated as in Example 1. In this second example, the total duration of an operating cycle is of the order of 27 hours.

EXEMPLE 3EXAMPLE 3

On traite de l'acide borique à 120 g/1.Boric acid is treated at 120 g / l.

On utilise une installation comportant deux malaxeurs-sécheurs GUEDU : un type 2500, de capacité 1600 1 et de surface d'échange 10 m2, et un type 820, de capacité 500 1, de 5 m2 de surface d'échange.An installation is used comprising two GUEDU mixer-dryers : a type 2500, with capacity 1600 1 and exchange surface 10 m 2 , and a type 820, with capacity 500 1, with exchange surface 5 m 2 .

On alimente 1,6 m de solution d'acide borique dans le malaxeur-sécheur type 2500, et l'on neutralise à la soude dans un rapport molaire Na/B = 0,26, on rajoute de la chaux dans un rapport molaire Ca/B = 0,5.1.6 m of boric acid solution is fed into the type 2500 mixer-dryer, and it is neutralized with sodium hydroxide in a Na / B molar ratio = 0.26, lime is added in a Ca molar ratio. / B = 0.5.

On réalise ensuite simultanément la phase P1 du prétraitement et l'évaporation sous une pression absolue de 0,25 bar. La capacité évaporatoire dans ces conditions est de 90 kg/h environ. Cette phase dure environ 2 h 40 min. On arrête ensuite l'évaporation pendant la phase P2 du prétraitement, soit 2,5 h environ, puis on reprend la concentration de la solution prétraitée, sous une pression de 0,1 bar, jusqu'à obtention d'environ 500 1 de suspension concentrée, contenant l'équivalent de 384 g/1 d'acide borique, soit un extrait sec d'environ 51% Cette dernière opération dure environ 12 h, soit un temps global de ce premier cycle de 17 h.Then, phase P1 of the pretreatment and the evaporation are carried out simultaneously under an absolute pressure of 0.25 bar. The evaporative capacity under these conditions is approximately 90 kg / h. This phase lasts approximately 2 h 40 min. The evaporation is then stopped during phase P2 of the pretreatment, ie approximately 2.5 h, then the concentration of the pretreated solution is resumed, under a pressure of 0.1 bar, until obtaining approximately 500 l of concentrated suspension, containing the equivalent of 384 g / l of boric acid, ie a dry extract of approximately 51% This last operation lasts approximately 12 h, or an overall time of this first cycle of 5 p.m.

La solution concentrée est ensuite transférée dans le GUEDU 820 dont la capacité évaporatoire sera de l'ordre de 40 1/h. On finit la surconcentration jusqu'à un extrait sec de 56%. L'opération dure 1h 30 environ.The concentrated solution is then transferred to the GUEDU 820, the evaporating capacity of which will be of the order of 40 l / h. We end the over-concentration to a dry extract of 56%. The operation lasts approximately 1 hour 30 minutes.

La pâte surconcentrée est ensuite acidifiée jusqu'à PH 8.The over-concentrated paste is then acidified to P H 8.

On mélange pendant 10 min avec du ciment CLK 45, dans un rapport eau libre/ciment de 0,8, avec ajout de 3% de plastifiant réducteur d'eau (en poids par rapport au ciment).Mixed for 10 min with CLK 45 cement, in a free water / cement ratio of 0.8, with the addition of 3% of water-reducing plasticizer (by weight relative to the cement).

On obtient 500 1 de béton, de densité 1,78~. Durée totale d'un cycle en supposant un travail en continu : 17 h. Réduction de volume : 3,2.We obtain 500 1 of concrete, density 1.78 ~. Total duration of a cycle assuming continuous work: 17 h. Volume reduction: 3.2.

Claims (6)

1. Procédé de conditionnement, par Liants hydrauliques, d'effluents radioactifs boratés de faible et de moyenne activité par traitement chimique visant à La préparation de cristaux de borate de calcium tétrahydraté, réduction de volume et malaxage du produit obtenu avec au moins un Liant hydraulique, caractérisé en ce que - ledit borate de calcium tétrahydrate est réalisé en ajoutant, à La solution à traiter, une quantité de chaux calcutee de façon à former Le borate B2O3CaO; - L'opération de réduction de volume est réalisée par évaporation, sous pression réduite, des solutions et/ou suspensions, Ladite pression réduite étant comprise entre 0,1 et 0,3 bar environ et appliquée après La phase de préparation des cristaux de borate de calcium tétrahydraté ; - et que Ladite réduction de volume est menée à bien jusqu'à l'obtention, en fin de procédé, d'une suspension bétonnable contenant d'environ 30 à environ 70 % de matière sèche. 1. Process for conditioning, by hydraulic binders, borated radioactive effluents of low and medium activity by chemical treatment aimed at the preparation of crystals of calcium borate tetrahydrate, reduction in volume and mixing of the product obtained with at least one hydraulic binder , characterized in that - Said calcium borate tetrahydrate is produced by adding, to the solution to be treated, a quantity of calcined lime so as to form borate B 2 O 3 CaO; - The volume reduction operation is carried out by evaporation, under reduced pressure, of the solutions and / or suspensions, said reduced pressure being between 0.1 and 0.3 bar approximately and applied after the phase of preparation of the borate crystals calcium tetrahydrate; - And that said reduction in volume is carried out until the end of the process, a concrete suspension containing about 30 to about 70% dry matter. 2. Procédé de conditionnement, par liants hydrauliques, d'effluents radioactifs boratés de faible et de moyenne activité par traitement chimique visant à La préparation de cristaux de borate de calcium tétrahydraté, réduction de volume et malaxage du produit obtenu avec au moins un Liant hydraulique, procédé dans lequet La phase de préparation de cristaux de borate de calcium tétrahydraté comporte une première étape d'adjonction de chaux et de germination, une deuxième étape de formation de sels mixtes, une troisième étape de formation dudit borate et une quatrième étape de mûrissement des cristaux dudit borate, caractérisé en ce qu'une réduction de volume, sous pression réduite est également effectuée durant au moins l'une des première et quatrième étapes, et éventuellement après La phase de préparation des cristaux de borate de calcium tétrahydraté.2. Method of conditioning, by hydraulic binders, borated radioactive effluents of low and medium activity by chemical treatment aimed at the preparation of crystals of calcium borate tetrahydrate, reduction of volume and kneading of the product obtained with at least one hydraulic binder , process in lequet The phase of preparation of calcium borate crystals tetrahydrate comprises a first stage of addition of lime and germination, a second stage of formation of mixed salts, a third stage of formation of said borate and a fourth stage of ripening crystals of said borate, characterized in that a reduction in volume, under reduced pressure is also carried out during at least one of the first and fourth stages, and possibly after the phase of preparation of crystals of calcium borate tetrahydrate. 3. Procédé de conditionnement selon l'une des revendications 1 et 2, caractérisé en ce que Les effluents sont également soumis à une évaporation sous pression réduite avant la phase de formation des cristaux de borate de calcium tétrahydraté.3. Packaging method according to one of claims 1 and 2, characterized in that The effluents are also subjected to evaporation under reduced pressure before the phase of formation of calcium borate crystals tetrahydrate. 4. Procédé seton l'une des revendications 1 à 3, caractérisé en ce que L'ensembLe de La phase de cristallisation est réalisé sous une pression réduite comprise entre environ 0,7 et G.9 bar.4. Method according to one of claims 1 to 3, characterized in that the whole of the crystallization phase is carried out under a reduced pressure of between about 0.7 and G.9 bar. 5. Procédé selon L'une des revendications 1 à 4, caractérisé en ce que La préparation des cristaux de borate de calcium tétrahydraté est réalisée par formation au cours de La troisième étape de borate de calcium hexahydraté, LequeL est ultérieurement, durant Ladite quatrième étape, transformé en borate de calcium tétrahydraté.5. Method according to one of claims 1 to 4, characterized in that The preparation of calcium borate crystals tetrahydrate is carried out by formation during the third step of calcium borate hexahydrate, LequeL is later, during said fourth step , transformed into calcium borate tetrahydrate. 6. Dispositif pour La mise en oeuvre du procédé selon L'une des revendications 1 à 5, caractérisé en ce que Ledit procédé est mis en oeuvre, en discontinu, dans un (ou deux) appareil qui est un méLangeur-maLaxeur-évaporateur et qui comporte un dispositif de maintien de La température, un agitateur à plusieurs régimes d'agitation et efficace avec des fluides de viscosités variables et un dispositif permettant d'y réaliser une pression de 0,1 à 1 bar environ.6. Device for the implementation of the method according to one of claims 1 to 5, characterized in that said method is implemented, discontinuously, in one (or two) apparatus which is a mixer-maLaxer-evaporator and which includes a device for maintaining the temperature, an agitator with several agitation regimes and effective with fluids of variable viscosities and a device making it possible to achieve a pressure of 0.1 to 1 bar approximately.
EP19860400591 1985-03-21 1986-03-20 Process and device for conditioning low and middle level radioactive waste solutions with hydraulic binders Expired EP0195723B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8504222A FR2579360B1 (en) 1985-03-21 1985-03-21 PROCESS AND DEVICE FOR THE CONDITIONING, BY HYDRAULIC BINDERS, OF LOW AND MEDIUM ACTIVITY RADIOACTIVE EFFLUENTS
FR8504222 1985-03-21

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EP0195723A1 true EP0195723A1 (en) 1986-09-24
EP0195723B1 EP0195723B1 (en) 1989-08-02

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Cited By (1)

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Publication number Priority date Publication date Assignee Title
EP0929079A1 (en) * 1997-08-26 1999-07-14 Institute Of Nuclear Energy Research, Taiwan, R.O.C. Method for solidification of boric acid and/or borates solutions

Families Citing this family (3)

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Publication number Priority date Publication date Assignee Title
CN102208225B (en) * 2011-05-19 2013-01-30 清华大学 Method for solidifying radioactive boron-containing residual distillate by Portland cement
JP2013096896A (en) * 2011-11-02 2013-05-20 Toshiba Corp Method and apparatus for treating boric acid containing waste fluid
FR3080112B1 (en) * 2018-04-17 2020-05-01 Onet Technologies Cn PROCESS FOR CONDITIONING BORATE WASTE BY CEMENT

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US3557013A (en) * 1966-04-07 1971-01-19 Emile Detilleux Process for solidifying radioactive wastes by addition of lime to precipitate fluoride
FR2333331A1 (en) * 1975-11-28 1977-06-24 Kernforschung Gmbh Ges Fuer PROCESS FOR AVOIDING DISTURBANCES DURING SOLIDIFICATION OF MATERIALS CONTAINED IN RADIOACTIVE WASTEWATER
US4086325A (en) * 1976-02-13 1978-04-25 Belgonucleaire, S.A. Process for drying solutions containing boric acid
US4409137A (en) * 1980-04-09 1983-10-11 Belgonucleaire Solidification of radioactive waste effluents

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DE2603116C2 (en) * 1976-01-28 1983-01-27 Nukem Gmbh, 6450 Hanau Process for the solidification of radioactive borate-containing aqueous solutions and suspensions
DE3029147A1 (en) * 1980-07-31 1982-02-25 Kraftwerk Union AG, 4330 Mülheim Treatment of radioactive residue of waste liquor contg. borate - by adjusting sodium boron molar ratio during concn. by evapn.

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US3557013A (en) * 1966-04-07 1971-01-19 Emile Detilleux Process for solidifying radioactive wastes by addition of lime to precipitate fluoride
FR2333331A1 (en) * 1975-11-28 1977-06-24 Kernforschung Gmbh Ges Fuer PROCESS FOR AVOIDING DISTURBANCES DURING SOLIDIFICATION OF MATERIALS CONTAINED IN RADIOACTIVE WASTEWATER
US4086325A (en) * 1976-02-13 1978-04-25 Belgonucleaire, S.A. Process for drying solutions containing boric acid
US4409137A (en) * 1980-04-09 1983-10-11 Belgonucleaire Solidification of radioactive waste effluents

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0929079A1 (en) * 1997-08-26 1999-07-14 Institute Of Nuclear Energy Research, Taiwan, R.O.C. Method for solidification of boric acid and/or borates solutions

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FR2579360A1 (en) 1986-09-26
JPS61258198A (en) 1986-11-15
DE3664830D1 (en) 1989-09-07
FR2579360B1 (en) 1992-03-06
EP0195723B1 (en) 1989-08-02

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