Alumino-borosilicate glass for the confinement of radioactive liquid effluents, and method for treating radioactive liquid effluents

1. A method for treating a radioactive liquid effluent of medium activity, wherein calcination of said effluent, to which is optionally added a calcination adjuvant, is carried out in order to obtain a calcinate, and a vitrification adjuvant for producing an alumino-borosilicate glass is then added to said calcinate, the vitrification adjuvant having the following composition expressed in percentages by mass:

SiO 2 : 58 to 65

B 2 O 3 : 15 to 19

Na 2 O: 5 to 10

Al 2 O 3 : 0 to 3

Li 2 O: 1 to 4

CaO: 1.5 to 4

ZrO 2 : 0 to 3

Fe 2 O 3 : 2 to 4

NiO: 0 to 2

CoO: 0 to 2,

it is proceeded with the melting of said calcinate and of said vitrification adjuvant in a cold crucible in order to obtain a glass melt, and said glass melt is then cooled down, whereby the alumino-borosilicate glass is obtained having the following composition expressed in percentages by mass based on the total mass of the glass:

a) SiO 2 : 45 to 52

b) B 2 O 3 : 12 to 16.5

c) Na 2 O: 11 to 15

d) Al 2 O 2 : 4 to 13

e) one or more element(s) ETR selected from oxides of transition elements and platinoids: where ETR is in the range of >0 to 5.25;

f) One or more element(s) TRA selected from rare earth oxides and from actinides oxides: where TRA is in the range of 0 to 3.5;

g) ZrO 2 : 0 to 4

h) Other elements AUT of the effluent: where AUT is in the range of 0 to 4;

and the composition of the glass further satisfies all of the following inequations in which the SiO 2 , Al 2 O 3 , B 2 O 3 , Na 2 O, ETR, AUT are expressed in percentages by mass based on the total mass of the glass:

SiO 2 +Al 2 O 3 <61%  (1)

71%<SiO 2 +B 2 O 3 +Na 2 O<80.5%  (2)

B 2 O 3 /Na 2 O>0.9  (3)

0.7 Al 2 O 3 −ETR<5%  (4)

Al 2 O 3 /ETR>2.5  (5)

0.127(B 2 O 3 +Na 2 O)>AUT.  (6)

2. The method according to claim 1 , wherein the other elements constitutive of the effluent (“AUT”) are selected from the following oxides: SO 3 , P 2 O 5 , MoO 3 , and BaO.

3. The method according to claim 1 , wherein the vitrification adjuvant is characterized in that it is in the form of a glass frit.

4. The method according to claim 1 , wherein the vitrification adjuvant is characterized in that it is in the form of a mixture of chemical products, especially of oxides, in the form of powders.

5. The method according to claim 1 , wherein the radioactive liquid effluent of medium activity contains the following elements in the following contents:

Na: from 30 g/L to 80 g/L

B: from 0 g/L to 5 g/L

Mn: from 0 g/L to 1 g/L

Ce: from 0 g/L to 14 g/L

Fe: from 0 g/L to 3 g/L

Ni: from 0 g/L to 1 g/L

Cr: from 0 g/L to 1 g/L

Zr: from 0 g/L to 16 g/L

Mo: from 0 g/L to 10 g/L

P: from 0 g/L to 4 g/L

S: from 0 g/L to 1.7 g/L

Ba: from 0 g/L to 7 g/L

Gd: from 0 g/L to 1 g/L

Tc: 1 g/L or less

Actinides: from 0 g/L to 8 g/L

Platinoids: 1 g/L or less;

the total content of said elements being from 30 g/L to 154.7 g/L.

6. The method according to claim 5 , wherein the radioactive liquid effluent contains the following elements in the following contents:

Na: 55 g/L

B: 2.5 g/L

Mn: 0.5 g/L

Ce: 7 g/L

Fe: 1.5 g/L

Ni: 0.5 g/L

Cr: 0.5 g/L

Zr: 8 g/L

Mo: 5 g/L

P: 2 g/L

S: 0.85 g/L

Ba: 3.5 g/L

Gd: 0.5 g/L

Tc: 1 g/L

Actinides: 4 g/L

Platinoids: 1 g/L;

the total content of said elements being 93.35 g/L.

7. The method according to claim 1 , wherein the calcination adjuvant is selected from aluminium nitrate, iron nitrate, zirconium nitrate, rare earth nitrates, and mixtures thereof.

8. The method according to claim 7 , wherein the calcination adjuvant is a mixture of aluminium nitrate and of iron nitrate.

9. The method according to claim 5 , wherein the Na 2 O/(sum of the oxides in the calcinate) ratio is less than or equal to 0.3.

10. The method according to claim 5 , wherein the vitrification adjuvant is as defined in any one of claims 4 to 5 .

11. The method according to claim 5 , wherein the melting of the calcinate and of the vitrification adjuvant is carried out a temperature from 1,200° C. to 1,300° C. preferably 1,250° C.

12. The method according to claim 1 wherein the oxides of transition elements are selected from Fe 2 O 3 , Cr 2 O 3 , MnO 2 , and TcO 2 .

13. The glass according to claim 1 wherein the platinoids are selected from RuO 2 , Rh, and Pd.

14. The method according to claim 1 wherein the rare earth oxides are selected from La 2 O 3 , Nd 2 O 3 , Gd 2 O 3 , Pr 2 O 3 , and CeO 2 .

15. The method according to claim 1 wherein the actinides oxides are selected from UO 2 , ThO 2 , Am 2 O 3 , PuO 2 CmO 2 , NpO 2 .

16. The method according to claim 8 , wherein the calcination adjuvant mixture of aluminium nitrate and of iron nitrate has the following proportions relating to the contents: 0.66<Al 2 O 3 /(Al 2 O 3 +Fe 2 O 3 )<1 wherein the contents are oxide contents by mass.