Effect of Fe 2 O 3 /ZnO on Two Glass Compositions for Solidification of Swedish Nuclear Wastes
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FECT OF Fe2 03/ZnO ON TWO GLASS COMPOSITIONS FOR SOLIDIFICATION OF SWEDISH NUCLEAR WASTES J. L. NOGUES* AND L. L. HENCH** *Laboratoire des Verres, Universite des Sciences et Techniques du Languedoc, 34060 Montpellier Cedex (France); **Ceramics Division, Department of Materials Science and Engineering, University of Florida, Gainesville, Florida, USA
INTRODUCTION A recent study concluded that addition of Fe203 to a soda borosilicate nuclear waste glass may significantly reduce damage by water attack due to formation of a Fe-rich film on the glass surface. SiO2 , B2 0 3 , CaO,
However,
differences in
and concentration of fission products in previous glass
compositions make it to Fe203 content.
impossible to ascribe the improved leach resistance solely In the present work,
leaching behavior of two glasses are
compared which differ only by the substitution of Fe203 for some of the ZnO in the glass.
Both glass compositions,
Table 1, are compatible with the French
AVM process2 and contain 9% (by weight) of simulated waste products characteristic of the Swedish nulcear waste program.
EXPERIMENTAL PROCEDURE Leaching was performed at 90'C with deionized water in the MCC-[ Standard Test for Leaching
3
at two ratios of glass surface area (SA)
(V); SA/V = 1.0 cm-I and 0.1 cm-I for times of 1, 3,
7,
to solution volume
14 and 28 dlays.
Leachant solution pH was measured with a microelectrode and solution analysis was performed by: ICP spectroscopy--Si 4+, B 3+, Mo6+; atomic absorption--Fe3+ S.
+
and atomic emission--Na . Normalized average leach rates are reported. All sample surfaces were polished to a 600 grit surface with dry SiC paper and analyzed before and after leaching with infrared reflection spectroscopy (IRRS). 4 ' 5 TheIRRS -l spectra were normalized to a value of 80 for the 1120 cm Si-O-Si molecular stretching vibration of vitreous silica by using a shutter in
the reference beam
of a Perkin-Elmer 467 IR spectrometer.
RESULTS The substitution of Fe203 for ZnO in 41 (3.0% Fe2 0, Si
, B
, Na
3.0% ZnO) and Mo
this pair of glasses results in ABS
having average leach rates nearly 3 times higher for
than ABS 29 (0.6% Fe2 0
6.0% ZnO),
Figs. I and 2.
3
Although the normalized leach rates for A1 + are the same for the two compositions,
3
the normalized rates for Fe + release are three times higher for the
274
TABLE
I
COMPOSITION OFSIMULATED NUCLEAR WASTE (WEIGHT %)
NUCLEARWASTEGLASS COMPOSITIONS (WEIGHT %)
ABS29
ABS41
Si02
52.0
52.0
B203
15.9
15.9
Al203
2.5
2.5
Na20
9.4
9.4
Fe203
0.6
3.0
G
OXID E Cs2 o WEIGHTU
ZnO
6.0
3.0
3.0
3.0
DO2
1.66
1.66
S.W.P*
9
9
BaO y203 Zr0°2
m°O3
2.89
5.11
1.67
14.22
18.1)
La2 03
Nd203
Pr20 3
Ce203
7.89
13.44
4.22
8.33
OKIDE Sao Sb0 20 WETGHT
Li 20
9.78
Sco
0
0.19
0.04
1n°2 8.56
Cd0
-. 11
0.29
Simulated waste products
.-. .....-.............- ........................................ELUL
1 Fig.
• -- --------- Zn
\
LU
3
7
14
DAYS CORROSION
0.12
Ni3
ABS 41 AVERAGE LEACH RATES STATIC LEACHING IN9
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