FR2759196A1 - APPARATUS USING TANNIN FOR THE TREATMENT OF AN EFFLUENT CONTAINING PLUTONIUM - Google Patents

Abstract

The device which satisfies the regulatory concentration of wastewater, is easy to set up, operates in a simple and compact process, and leaves very little residue after the treatment of the effluent. The treatment process is separated into a treatment system with a high level of radioactivity and a treatment system with a low level of radioactivity. These systems are respectively installed in handling glove boxes (10, 12) connected in series. In the box (10), effluent with a high level of radioactivity coming from an effluent receiving tank (20), is successively supplied to columns of adsorbent (30a, 30b, 30c) filled with insoluble tannin, and the effluent leaving these columns is supplied to a monitoring tank (40a).

Description

I

BACKGROUND OF THE INVENTION

  The present invention relates to an apparatus for

  treatment of an effluent containing plutonium and, more

  in particular, a device using tannin as an adsorbent

  for the treatment of an effluent containing plutonium. DESCRIPTION OF THE TECHNIQUES CONCERNED

  Figure 2 shows a reprocessing process

  spent nuclear fuel. In this retreat process-

  spent nuclear fuel is dissolved in a solution

  tion of nitric acid to transform the component elements into nitrates, after which elements of actinides such as uranium (U) and plutonium (Pu) are separated and

  recovered in the form of their nitrate salts in use

  sant an organic solvent (S101). Then, in the transformation process, the plutonium solution and the recovered uranium solution are mixed, then the nitrates of U

  and Pu contained in the mixed solution are denitrified.

  The UO3, PuO2 powder obtained is coarsely ground and

  calcined to obtain a powder of U306, PuO2 which is

  reduced sequence to obtain a MOX powder of UO2, PuO2

  (S102). Then, in a fuel fabrication step -

  ble, the MOX powder is formed into pellets in a step of

  pressing so as to obtain MOX fuel (S103).

  When the pellets are formed in the pro-

  discontinued fuel manufacturing described above, some

  some of the pellets may be cracked or may contain impurities. These pellets are recovered in the form of debris (S104). These debris are redissolved in nitric acid and extracted with the solvent to remove the

  impurities, after which the debris is recycled to the pro-

  ceasing to manufacture fuel to obtain fuel

MOX target.

  In the plutonium recycling step described above, the plutonium-containing effluent is produced mainly during solvent extraction in the debris recovery step (F104). The specific radioactivity of plutonium per unit weight is 3-4 orders higher

  of magnitude to that of uranium. The relevant regulations

  n the effluent discharge specify radioactivity by

  unit volume of effluent independently of the substance contained therein, so that to satisfy the regulations concerning the effluent, the weight of Pu allowed5 is 3-4 orders of magnitude greater than that of U per vo -

unit lume of effluent.

  In the previous process, as shown for example in FIG. 3, the Pu contained in the effluent is re-

  the radioactivity of the effluent is reduced by coa-10 gulation and precipitation of the substances contained in

  the effluent, then by passing the effluent through a se-

  adsorption columns filled with various adsorbents.

  To describe this more precisely, in a processing apparatus

  tement of conventional effluent such as that shown in FIG. 3, two handling glove boxes which are sealed effluent treatment chambers, are connected in series. The handling glove box 10 is a chamber

  of primary treatment to adsorb Pu in a formal effluent

  radioactive material, while the glove box handling

  tion 12 is a secondary treatment chamber for adsorbing Pu in an effluent whose radioactivity level

  has already been reduced in the handling glove box 10.

  In box 10, an effluent receiving tank 20 is

  used to receive the highly radioactive effluent. The re-

  effluent receiving server 20 provides this effluent for-

  radioactive to a reservoir of coagulation and

  precipitation 60. In the coagulation and pre-

  Cipitation 60, which includes three stages, coa-

  gulants (such as for example chloride coagulants

  ferrous and polymeric coagulants) as well as other reactants

  tifs, and the plutonium is precipitated in the form of hydroxide (co-precipitation). The liquid which floats is then supplied to two adsorption columns 70 filled with grains of active carbon, so as to adsorb the Pu, and the effluent having passed through these

  adsorption columns 70 is supplied to a sur-

  watch 40a. In the monitoring tank 40a, we

  monitors the level of radioactivity in the effluent and performs an inspection to determine if it is safe

  whether or not to supply the effluent to the handling glove box

  tion 12 which is intended to treat effluent at low ni-

  radioactive calf. This is to prevent the handling glove box 12 from being contaminated with effluent with a high level of radioactivity which would prevent the level of

  final radioactivity of the effluent, reaching a vi-

  sée. When effluent with a level of radioactivity

  low predetermined is detected in the sur-

  veillance 40a, this effluent is supplied to an adsorption column

  activated carbon bant impregnated with zinc chloride 80, filled with active carbon impregnated with zinc chloride, in the box

  glove handling 12. In these four adsorption columns

  bant with activated carbon impregnated with zinc chloride 80, we ad-

  releases more Pu into the effluent.

  The effluent which now has a level of radioac-

  even lower activity, is supplied to an adsorption column

  bant with chelate resin 90 in which Pu is adsorbed, and the effluent obtained is supplied to a monitoring tank

  40b. In the monitoring tank 40b, monitoring is

  core the level of radioactivity of the effluent and, if the eff-

  fluent satisfies the regulatory concentration of water

  worn, this effluent is discharged. When the effluent does not

  does not meet the regulatory concentration of wastewater, this effluent is sent to a third treatment chamber in which Pu is still adsorbed and, after the effluent radioactivity level has been further reduced

  way, the effluent is finally discharged.

  However, in the process described above, we

  produced a large amount of mud containing hy-

  Pu dioxide and coagulants as a by-product of coagulation and the precipitation process, so there remained the problem of how to treat and discard

this mud.

  In addition, the process involved implementing

  complex pes such as extraction, dehydration, drying, calcination and storage of a precipitate and,

  as we had to use a number of pro-

  and equipment, the entire milking apparatus

effluent was cumbersome.

  In addition to the process described above, other

  effluent treatment processes are used in ins-

  nuclear fuel processing plants, such as

  example ion exchange, evaporation, heating at mid

  microwave and film separation. However, even in these cases, by-products are still produced

  and, as in the case of the process described above, the pro-

  cures themselves are complicated and require multiple processes and equipment, so that all of

the device is bulky.

  In addition, when adsorbents were used,

  it was difficult to reduce the residual amount

  dual of Pu to an order of magnitude 3 to 4 times weaker

  than that of U per unit volume of effluent, for satis-

  make regulations on effluents. It was therefore necessary to combine several treatment methods

  which made the device even more cumbersome and which increased

  lied construction and operating costs.

SUMMARY OF THE INVENTION

  The object of the present invention is therefore to take into account

  naked of the above problems, to create a milking-

  effluent containing plutonium, which satisfies the regulatory concentration of wastewater, which works

  following a unique and compact process by means of a process

  simple, and leaves little residue after treatment of the effluent.

  To this end, the apparatus for processing an ef-

  fluent containing plutonium, according to the present invention,

  includes the following features.

  (1) Two or more columns of adsorbent

  folds of an insoluble tannin adsorbent, the

to each other.

  As described in Japanese patent published No. Hei.5-66291, an insoluble tannin adsorbs uranium and transuranic elements extremely well. In this context, insolubility means insolubility in water, in an acid or in an alkali. When an effluent containing Pu is passed through two or more columns filled with insoluble tannin, the Pu contained in the effluent is adsorbed by the tannin so that the regulatory concentration can be satisfied by a single process, without it is necessary to use other methods. It also provides a simple, easy-to-do effluent treatment device

  function, and as the tannin has a capacity to

  high Pu sorption, the adsorption column can be made

  bant in a smaller form, which makes all of

  the device more compact than in the previous process.

  In addition, the insoluble tannin is made up of car-

  bone, hydrogen and oxygen so that if the adsorbent

  worn which is no longer able to adsorb Pu is incinerated, this ta-

  nin is transformed into carbon dioxide and water vapor from

  so that it can be discharged safely without conta-

  undermine the environment. The minimal amounts of U and Pu adsorbed by the insoluble tannin are oxidized to give

  uranium oxide and plutonium oxide. These oxides can

  wind for example be processed into MOX powder, so

  than the amount of unusable residue remaining after processing

  effluent can be reduced to extreme levels

mentally weak.

  (2) In the apparatus using tannin for the treatment of an effluent containing plutonium, as described

  in paragraph (1) above, two or more of the co-

  lons of adsorbent described above can be connected in series inside a sealed effluent treatment chamber, two or more of these treatment chambers

  leakproof effluent with different radioactivity levels

  and also being connected to each other

serial.

  The use of two or more

  waterproof effluent treatment makes it possible to adjust different

  radioactive levels for each room. If the effluent treatment was carried out using only one chamber for example, this chamber would be contaminated by the effluent with a high level of radioactivity, so that the final level of radioactivity of the effluent leaving the

  column should not reach the target value. In fact

  killing effluent treatment in two or more chambers

  bres as described above, there is no risk that the effluent (i.e. wastewater) that ultimately leaves the column is exposed to high level radiation so that the regulatory concentration of wastewater cannot be met. As a result, using the apparatus according to the present invention, the regulatory concentration of wastewater is satisfied and, in addition, as the two or more effluent treatment chambers are connected

  effluent treatment can be carried out serially

lesson continues.

  (3) In the apparatus using tannin for the treatment of an effluent containing plutonium, as described in paragraphs (1) and (2) above, the

  waterproof effluent treatment are glove boxes of ma-

  nipulation. When treating the effluent in a glove box

  handling, workers carry out door operations

  so many gloves so that they are not exposed to the ray-

  and that the equipment can be operated by simple procedures. In addition, like the insoluble tannin used

  as an adsorbent in the present invention has a capacity

  high Pu adsorption city, the adsorbent column itself

  even can be made in a smaller form. It therefore adapts easily in a glove box having a width less than twice the length of a worker's hand, so that the machine can be compacted.

effluent treatment.

  (4) In the apparatus using tannin for the treatment of an effluent containing plutonium, as described in paragraphs (1) and (2) above, the adsorbent, already

  used to treat a low level radioactive effluent

  activity, can be recharged in a treatment column

  an effluent with a high level of radioactivity.

  As the adsorbent is reused before incineration-

  tion, the quantity of adsorbent (tannin) is reduced, the inciner-

  ration of spent tannin is minimized and the amount of residue remaining to be treated is kept to a minimum. So this process

  improves workers' exposure to radiation

  and improves cost performance compared to the previous process. (5) In the apparatus using tannin for the treatment of an effluent containing plutonium, as described in any one of paragraphs (1) to (3) above, the insoluble tannin is loaded into cartridges of combustible material, and the adsorbent column is then filled with

  these cartridges in a multistage arrangement.

  This minimizes the splashing of Pu

  when the adsorbent is replaced in the treatment process

  effluent, and the entire cartridge can be incinerated after use. It also minimizes workers' exposure to radiation when the adsorbent columns

  are filled or when their contents are unloaded.

  According to other characteristics of the invention

tion:

  - a monitoring tank, intended to monitor the level

  calf radioactive effluent arriving, is placed between the sealed effluent treatment chambers, and the monitoring tank checks if effluent can

  whether or not it is supplied to a low-level processing chamber

  radioactive calf in the next floor, and provides

  effluent with a low level of predefined radioactivity

finished, on the next floor,

  - a monitoring tank, intended to monitor the level

  calf radioactive effluent arriving, is placed between the sealed effluent treatment chambers, and the monitoring tank checks if effluent can

  whether or not it is supplied to a low-level processing chamber

  radioactive calf in the next floor, and provides

  effluent with a low level of predefined radioactivity

finished, on the next floor.

BRIEF DESCRIPTION OF THE DRAWINGS

  The present invention will be described below in more detail using an embodiment

  presented in the accompanying drawings in which: 5 - Figure 1 is a diagram showing the construction of a

  device using tannin for the treatment of an ef-

  fluent containing plutonium according to the present invention

tion;

  - Figure 2 is a flow diagram of fuel fabrication

  ble MOX from spent nuclear fuel; and FIG. 3 is a diagram showing the construction of an effluent treatment apparatus containing plutonium,

according to the prior art.

  DESCRIPTION OF THE PRESENT INVENTION

  We will now describe a pre-

  of the present invention.

  The apparatus using tannin for the treatment of an effluent containing plutonium, according to the present embodiment, will be described with reference to FIG. 1. The component elements which are identical to those of the apparatus for treating effluent containing plutonium, according to art

  previous, are designated by the same symbols and their des-

cription is not repeated.

  In the effluent treatment apparatus according to the

  present embodiment, two glove boxes for handling

  lation 10, 12 operating in effluent treatment chambers

  fluent waterproof, are connected in series. The handling glove box 10 is a primary processing chamber

  for the adsorption of an effluent with a high level of radioactive activity

  tee, and the handling glove box 12 is a

  secondary treatment for adsorption of Pu in an ef-

  fluent whose radioactivity has already been reduced to a low level in the handling glove box 10. An effluent receiving tank 20 intended to receive an effluent

  having a high level of radioactivity (for example a

  alpha radiation centration = 105-106Bq / ml) is placed

  in the handling glove box 10. The reservoir for

  ception de effluent 20 provides this effluent with a high level of radioactivity to an adsorbent column 30 filled with insoluble tannin. According to this embodiment, three are used

adsorbent columns 30.

  The effluent having passed through the adsorption columns

  bant 30a, 30b, 30c is supplied to a monitoring tank a. In this monitoring tank 40a, the level of radioactivity is monitored and an inspection is carried out to determine whether or not the effluent can be supplied to the handling glove box 12 of the next stage, which consists of

  l0 a treatment chamber with a low level of radioactivity.

  This is done to avoid that highly effluent

  dioactive is supplied to the handling glove box 12, which could contaminate it ("cross contamination") and

  prevent the final level of radioactivity from the

  dye a target value. When it is found that the monitoring tank 40a contains effluent having a predetermined level of radioactivity (for example an alpha radiation concentration = 5.6 Bq / ml), this effluent at low level

  of radioactivity is supplied to a column of adsorbent 50 rem-

  plaice of insoluble tannin, in the handling glove box

  tion 12. A greater quantity of Pu in the effluent is then adsorbed by these two columns of adsorbent 50a, 50b, and the final effluent is supplied to a monitoring tank b. In the monitoring tank 40b, the level of radioactivity of the effluent is monitored and, if the regulatory concentration of the wastewater is satisfied (by corresponding

  for example at a concentration of radiation al-

  pha = 5.6 x 10-2Bq / ml), the effluent is discharged.

  If the effluent does not meet the concentration

  wastewater regulation, a third chamber is used

  of treatment. In this third milking chamber

  we pass the effluent through another column

  filled with insoluble tannin, in which the Pu is new

  adsorbed calf and after this further reduction in

  radioactivity of the effluent, it is discharged.

  According to this embodiment, the effluent

  was processed in two floors with radioactive levels

  different lives. However, the invention is not limited to this arrangement and, on the contrary, the effluent can be passed through a larger quantity of handling glove boxes which are sealed treatment chambers arranged in series, these chambers having a number of radioactivity levels, depending on the level of radio

  effluent activity and the amount of effluent to be treated

  ter. According to this embodiment, a coagulation and precipitation column is not combined with a column of activated carbon adsorbent, as in the apparatus of the

  process according to the prior art. Coagu- mud extraction

  lée and precipitated, in the tank of coagulation and

  precipitation, followed by dehydration, purification

  tion, calcination, packaging in cans and storage, are therefore not necessary so that the whole procedure is easier and the operations are more

  simple. In addition, the addition of reagents is also

  useful, which makes the procedure even easier to carry out. In addition, since the insoluble tannin used in this embodiment has a structure represented by the chemical formula (I) below, the tannin is decomposed by heat (incineration) into carbon dioxide and water vapor, so that only a minimal amount of adsorbed material comprising plutonium is recovered in the form of oxides,

  etc. This reduces the amount of secondary waste products.

res. OH HO- /

HO-- -CO -O

I

OH HO- - COO

  OH To treat the insoluble tannin used in the present invention so as to put it in a form in which it can adsorb metallic elements, one can use a manufacturing process such as that described for example in the Japanese patent published No. Hei 5 066 291

  (Koho). According to this process, condensed tannin powder is dissolved in ammonia, an aqueous solution of alde-

  hyde is mixed with this solution to form a gel-like compound, and this gel-like compound is either aged at room temperature or heated to

  stabilize, so as to obtain a gel-type adsorbent. The mechanism by which the insoluble tannin adsorbs Pu in the present embodiment of the invention

  tion, may appear to be represented by the chemical formula (II) below.

H O \ / \

- -CD - O

* 1Pu

OH HO_ -COOH

Pu (OH) -PU4 ++ 4OH-

OH

  The adsorbent filling column 50 for treatment

  an effluent with a low level of radioactivity, is

  then reloaded in column 30 to treat an effluent with a high level of radioactivity. As the adsorbent is reused

  before being incinerated, the amount of adsorbent (tannin) used

  sée is reduced, the incineration of spent tannin is minimized,

  and the amount of residue remaining to be treated is reduced to half

  minimum. This process improves the exposure levels of the

  radiators, and improves cost performance,

  compared to the process of the prior art.

  According to this embodiment also, the insoluble tannin is loaded into cartridges of combustible material, and the adsorbent columns 30, 50 are then

  filled with these cartridges in a multi-storey arrangement

  multiple. By loading the insoluble tannin into cartridges,

  Pu splashing is minimized when replaced

  places the adsorbent in the ef- treatment process

  fluent. In addition, as these cartridges are produced in a

  combustible material, cartridges can be complete-

  incinerated after use. It also minimizes

  radiation exposure when the adsorption columns

  bant are filled or when their contents are unloaded.

DESCRIPTION OF REAL EXAMPLES

  The present invention will be described below in more detail using specific examples. The effluent treatment apparatus used in these examples has the construction shown in Figure 1 and operates as

described above.

Example 1:

  (1) Target value of the effluent treatment:

  Concentration of alpha radiation after primary treatment

mayor:, 6 Bq / ml or less

  Concentration of alpha radiation after treatment se-

  condaire:, 6 x 10-2 Bq / ml or less (2) Processing conditions:

  Amount of insoluble tannin used.

  Glove box for handling (10) (primary treatment

mayor):

  liters x 2 columns (adsorbent columns 30b, 30c).

  + 10 liters x one column (adsorbent column 30a)

  Glove box for handling 12 (second treatment

daire):

  50 liters x 2 columns (adsorbent columns 50a, 50b).

  Concentration of alpha radiation in the front effluent

treatment: 2.7 x 105Bq / ml.

  pH: adjusted to 6.8 with ammonia

  Flow rate: the effluent is passed at a flow rate of approximately

0.7 liters / hour.

  Quantity of effluent treatment: 200 liters

  (3) Treatment results (average of several experiences

these)

  Concentration of alpha radiation after primary treatment

mayor:, 0 x 10-1 Bq / ml

  Concentration of alpha radiation after treatment se-

condaire: 2.0 x 10-2 Bq / ml

  This confirms that an effluent with a high level of ra-

  dioactivity can be reduced to the target radioactivity level, using an adsorbent column filled only with

insoluble tannin.

Example 2:

  (1) Processing conditions in a manual glove box

  pulation 12 (secondary treatment) low level of ra-

  dioactivity), and amount of adsorption until the adsorbent is replaced. Quantity of insoluble tannin used: 50 liters Quantity of treated effluent: 1500 liters Average alpha radiation concentration of the effluent to be treated: 5 Bq / ml Average alpha radiation concentration of the treated effluent: 2.0 x 10-2 Bq / ml

  The amount of radiation adsorbed is as shown

  felt by the following equation (1): Bq / ml x (1500 x 1000) - 2.0 x 10-2 Bq / ml x (1500 x 1000) = 7.47 x 106 Bq (1) The amount of Pu per liter of adsorbent, taking the specific radioactivity of Pu at 1.5 x 1010Bq, is given by the following equation (2): (7.47 x 106 Bq) / (1.0 x 1010 Bq / g) / 50 = 1.5 x 10-5g (2)

  (2) Processing conditions in the handling glove box

  lation 12 (secondary treatment, low level of radio-

  activity), and amount of adsorption until

the adsorbent is replaced.

  Quantity of insoluble tannin used: 39.2 ml Quantity of treated effluent: 800 ml Average alpha radiation concentration of the effluent to be treated: 1.2 x 104 Bq / ml Average alpha radiation concentration of the treated effluent: 5 Bq / ml (Concentration of alpha radiation from the treated effluent,

  after treatment of 800 ml: 5.6 Bq / ml).

  The amount of radiation adsorbed is as shown

  felt by the following equation (3): (1.2 x 104 Bq / ml x 800) - (5 Bq / ml x 800) = 9.596 x 106 Bq (3) The amount of Pu per liter of adsorbent, in taking the specific radioactivity of Pu at 1.0 x 1010 Bq, is as follows: 9.596 x 106 Bq) / (1.0 x 1010 Bq / g) = / 39.2 x 103 = 2.45 x 10-2g ( 4) From the above results, it has been found that the insoluble tannin used for the treatment with low level of radioactivity can be reused in the treatment

  high level of radioactivity.

  The insoluble tannin used in the

  effluent treatment containing plutonium, according to the pre-

  sente invention, adsorbs uranium extremely efficiently

  and the transuranic elements. Therefore, if we do not-

  ser the effluent through two or more columns filled with insoluble tannin, the Pu contained in the effluent is adsorbed by the insoluble tannin, and the regulatory concentration of wastewater can be satisfied by a single process, without the need for it to combine the process with other processes. The present invention therefore provides an apparatus for

  simple effluent treatment that is easy to operate-

  ner. In addition, as the tannin has a high adsorption capacity,

  vee of Pu, as described above, we can make the adsorption column smaller and make the whole of

  the more compact device, compared to the device of the pro-

assigned according to the prior art.

  The insoluble tannin consists of carbon, hydrogen and oxygen so that, if the spent adsorbent which has lost its adsorption capacity of Pu is incinerated, this adsorbent is converted into carbon dioxide and water vapor which 'you can unload without contaminating the environment. Else

  apart, the minimal amounts of U and Pu that have been adsorbed

  opened by insoluble tannin, are oxidized to give

  uranium oxide and plutonium oxide. These oxides can

  wind for example be processed into MOX powder, so that

  the residue remaining after treatment of the eff-

  fluent can be reduced to extremely small amounts.

Claims (9)

R E V E N D I C A T IONS   1) Device using tannin for the treatment of an ef-   fluent containing plutonium, characterized in that two or more columns of adsorbent (30, 50) filled with an adsorbent comprising insoluble tannin, are connected in series.   2) Device using tannin for the treatment of an ef-   fluent containing plutonium, according to claim 1, characterized in that   the two or more adsorbent columns (30, 50) are left   pectively connected mutually in series in each of two or more sealed effluent treatment chambers (10, 12) having different levels of radioactivity, and   the two or more watertight effluent treatment chambers   ches are also connected to each other in series.   3) Device using tannin for the treatment of an ef-   fluent containing plutonium, characterized in that the sealed effluent treatment chambers (10, 12) are   glove boxes for handling.   4) Device using tannin for the treatment of an ef-   plutonium-containing fluent according to claim 2, characterized in that the sealed effluent treatment chambers (10, 12) are   glove boxes for handling.    ) Apparatus using tannin for the treatment of an effluent containing plutonium, according to claim 1, characterized in that the adsorbent used for the treatment of a low effluent   level of radioactivity is recharged in an ad-   sorbent (30, 50) for the treatment of a high-level effluent radioactive calf.   6) Device using tannin for the treatment of an ef-   plutonium-containing fluent according to claim 2, characterized in that the adsorbent used for the treatment of an effluent with a low level of radioactivity is recharged in a column of ad-   sorbent (30, 50) for the treatment of a high-level effluent radioactive calf.   7) Apparatus using tannin for the treatment of an ef-   fluent containing plutonium according to claim 1, characterized in that the insoluble tannin is loaded into cartridges of combustible material, and each column of adsorbent is filled with these cartridges   in a multi-story layout.   8) Device using tannin for the treatment of an ef-   fluent containing plutonium, according to claim 2, characterized in that the insoluble tannin is loaded into cartridges of combustible material, and each column of adsorbent is folded by these cartridges in   a multi-story layout.   9) Apparatus using tannin for the treatment of an ef-   fluent containing plutonium according to claim 3, characterized in that the insoluble tannin is loaded into cartridges of combustible material, and each column of adsorbent is filled with these cartridges   in a multi-story layout.    ) Device using tannin for the treatment of an ef-   fluent containing plutonium, according to claim 2, characterized in that   a monitoring tank (40) for monitoring the level   radioactive calf from the effluent that arrives, is placed   the sealed effluent treatment chambers, and the monitoring tank (40) checks whether or not effluent can be supplied to a treatment chamber with a low level of radioactivity in the next stage, and provides   effluent with a low level of radioactivity predeter- mined, on the next floor.   11) Apparatus using tannin for the treatment of an ef-   fluent containing plutonium, according to claim 3, characterized in that a monitoring tank (40), intended to monitor the level of radioactivity of the effluent arriving, is placed between the sealed effluent treatment chambers, and the monitoring tank (40) checks whether or not effluent can be supplied to a treatment chamber with low level of radioactivity (30, 50) in the next stage, and supplies effluent having a low level of radioactivity   predetermined, on the next floor.