Chemical Stability of Simiulated HLW Forms in Contact With Clay Media
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Werner. Lutze, editor
CHEI.CAL STABILITY CF SILUA-D HUI1 F01
IN CONTACT WITH CLAY 1,EDIA+
P. VAN ISEGM4B , W. T1',EI-1ANS, R. DE BATISTA, Materials Science Department, S.C.K./C.E.N., B-2400 11L (Belgium); -AlsoRijksuniversitair Centrum, Antwerpen, B-2020 ANTERPEN (Belgium). ABSTRACT The corrosion stability of six simulated 1LW forms proposed by several European countries (five borosilicate glasses and one borosilicate glass ceramic) in contact with different media relating to the clay disposal has been investigated for periods up to 80 days and at a surface area to solution volume ratio of 1 cm-I under non de-aerated conditions. In the reference medium distilled water the corrosion stabilities are largely determined by saturation effects for elements such as Si, Ca, Mg, Sr, Fe and U. Si saturation is found to be enhanced by a large A1 2 0 3 concentration in the glass. In the clay-water mixture these saturation effects are much less predominant. Wet clay attacks the waste forms faster than the clay-water mixture, although the corrosion rates tend to decrease with time in both clay media. In general, no simple Arrhenius-type temnnerature dependence for the corrosion behaviour is found for the interval between 40 and 200 0 C. 1. INTRODUCTION In the Belgian nuclear program the use of borosilicate glasses for the conditioning of liquid high level waste produced by reprocessing plants is considered, in view of eventual disposal in deep geological layers.
To evaluate
the suitability of clay as a disposal medium, possible interaction effects between high level waste glass and clay environments are being investigated so that models for the long-term behaviour of glass in such environmental conditions can be established.
S.C.K./C.E.N. contributes to this evaluation by
carrying out experimental studies of the stability of a number of borosilicate glass ccumpositions in contact with clay environments. Six simulated waste forms are investigated in this context as a part of the current R & D programme of the Commission of the European Camunities on Management and Storage of Radioactive Waste.
Two of them, borosilicate glasses
SAN 60 2519 L3 C2 and SM 58 ILU11 have been designed (in France and in F.R. of Germany, resp.) for the incorporation of the HENC and L&
(high, low enriched
waste concentrates) stored at the Eurochemic plant at -1ol. The borosilicate glasses UK 209 (United Kingdom),
SCN 583020U 2 and SON 641920F 2 (France) and the
glass-ceramic C31 - 3 BC (F.R. Germany) were selected as reference waste forms. They have been studied already during the previous joint CBC programmel.
The
corrosion media investigated include distilled water as reference medium, a clay-water mixture and wet clay.
Tests were performed at different tempera-
'Supported in part by the Camnission of the European Communities
220 0 tures (40, 70, 90, 120, 150, 200 C) under non de-aerated conditions. It
is clear
that for the presently considered storage and disposal concept (i.e. a surface storage of several decades and a canister li
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