CS205905B1 - Borate silicate glass fixation of the concentrated radioactive wastes - Google Patents

Description

The invention relates to borosilicate glass which can be used to fix concentrated radioactive waste.

One way to dispose of radioactive waste is by solidifying and converting it into a vitreous or vitreous crystalline mass that meets the conditions of long-term safe storage.

Several methods of solidifying radioactive wastes and converting them into glass or glassy crystalline mass are known; for example, a mixture of preformed and crushed silica glass and calcined radioactive waste after mixing and melting forms a compact glassy or glassy crystalline mass upon cooling. Of the types of glasses used, borosilicate glasses have proven to be the best, although they have a number of drawbacks, such as they can only contain small amounts of radioactive waste aggregate, and a mixture of borosilicate glasses with radioactive waste calcine requires the high temperature required to produce a homogeneous end product. Such a temperature causes technological difficulties, in particular, increases the corrosion of materials, increases the escape of hazardous radioactive nuclides, etc. In addition, if the concentration of sodium oxide in the radioactive waste exceeds 4%, the phase containing molybdenum is separated. This conditioned phase entrains long-term radionuclides cesium (II) Cs and strontium (II) Sr, and since it is water-soluble, this significantly reduces the efficiency of the fixation process.

205 905

205 905

Said drawbacks can be eliminated or at least substantially reduced by the use of the glasses according to the invention, characterized in that they comprise the following components in a weight concentration: 30.0 to 85.0% SiO2 silica

2.0 to 30.0% alumina

0.5 to 20.0% of at least one oxide selected from the group consisting of titanium dioxide TiOg and zinc oxide ZnO

2.0 to 20.0% boron oxide BgO-j

2.0 to 20.0% of at least one oxide selected from the group consisting of magnesium oxide MgO and calcium oxide CaO

0.2 to 20.0% manganese oxide MnO 0.2 to 20.0% lithium oxide LigO

Glasses of this composition can hold radioactive waste calcinates in a concentration up to 50% by weight. Even at temperatures lower than 1000 ° C, a homogeneous mass can be obtained. When the molten mixture is cooled, the molybdenum-rich phase is not squeezed, even in the presence of sodium NagO in the calcine at a concentration of up to 30% by weight. The leachability of long-term cesium and strontium ions is reduced from 10 up to 10 g.cm.day, reported for the previously used borosilicate glass, containing Q * 2 containing fixed radioactive calcinate, to values of 10 g.cm.day.

The composition of borosilicate glasses according to the invention is explained in more detail in the examples which, however, do not exhaust all possibilities of the invention and the invention can be applied under other conditions.

Example 1

Glass with SiOg concentration 30.0%, AlgO ^ 13.2%, TiOg 12.3%, BgO4 ^ 2.3 MgO 12.3%, MnO 5.7%, LigO 14.2% was ground and mixed with model radioactive waste calcine at a concentration of 30.0% by weight. Calcinate contained, inter alia, sodium oxide NagO at a concentration of 30.0% and molybdenum oxide MoO2 at a concentration of 15.0%. By melting this mixture at a temperature of 950 ° C, a homogeneous product was obtained. Výluhová-; the cesium ^J 'Cs of this product was 8.32 * 10 g.cm · day and the strontium llSr leachability was 6.28 * 10 g.cm · day;

Example 2. !

Glass with SiOg concentration 75.0%, AlgO ^ 2.0%, TiOg 0.5%, BgO ^ H »-’

MgO 2.0%, MnO 3.7 LigO 6.0% was ground and mixed with model radioactive waste calcine at a concentration of 40.0% by weight. Calcinate contained, inter alia, sodium oxide at a concentration of 30.0% by weight and molybdenum oxide MoO2 at a concentration of 15.0% by weight. A homogeneous fixation product was obtained by melting this mixture at 950 ° C. Cesium ^J Cs radionuclide leached from this product at a rate of 6.43.10 g.cm.day; The leacher QO -9 -2 -1 strontium content Sr was 4.23.10 g.cm .day

Example 3

Glass with weight concentration SiOg56.5%, AlgO ^ 6.6%, TiOg 2.0%, ZnO 3.7%, ^B 2 ° 3 MgO 5.7%, MnO 9.0%, LigO 10.7% were ground and mixed with model radioactive waste calcine at a concentration of 50.0% by weight. Calcite contained outside

205 905 other sodium oxide NagO at a concentration of 30.0% by weight and molybdenum oxide MoO 2 at a concentration of 15.0%. A homogeneous product was obtained by melting the mixture at 860 ° C.

1 ^ 7 —8 —2 —1

The leaching rate of cesium ^J 'Cs from this product was 7.38.10 g.cm.day and the rate

Q0-9-2-2 strontium leaching Sr was 6.41.10 ⁷ g.cm.day.

Example 4

Glass batch, composition corresponding to glass with a weight concentration of SiO _{2 of} 46.6%,

Al ₂ O ₃ 5.6%, TiO ₂ 2.0%, B ₂ O ₃ 20.0%, MgO 3.0%, CaO 2.9%, MnO 5.7%, Ia ₂ 0 14.2% , was mixed with model radioactive waste calcine at a concentration of 35.0%. Calcine contained inter alia sodium oxide Ne ₂ O at a concentration of 27.4% and molybdenum oxide at a concentration of 7.9%. A homogeneous product was obtained by melting this mixture at 800 ° C. The leaching of cesium radionuclide from this product was »2-1.1. 90-9-2.1 and 6.54.10 g.cm. Day and the strontium leachability Sr was 7.13.10 g.cm. Day.

Claims (2)

Object of the invention Borosilicate glass for the fixation of concentrated radioactive waste, characterized in that it contains the following constituents in weight concentration: 30.0 to 85.0% of silica Si0 ₂ 2.0 to 30.0% Al ₂ O ₃ 0.5 to 20.0% of at least one oxide selected from the group consisting of titanium dioxide TiO ₂ and zinc oxide ZnO 2.0 to 20.0% boron trioxide B ₂ 0 ₃ 2.0 to 20.0% of at least one oxide selected from the group consisting of magnesium oxide MgO and calcium oxide CaO 0.2 to 20.0% manganese oxide MnO 0.2 to 20.0% lithium oxide LigO