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SENSITIVITY OF WASTE GLASS LEACHING TO PARAMETERS OF THE GEOLOGICAL ENVIRONMENT

Objective


The chemical composition and oxidation reduction properties of groundwater significantly affect the solubility of transuranic nuclides released by corrosion from a nuclear glass. The effects of the oxidation reduction potential and carbonate concentration on the alterability and containment properties of R7T7 glass were investigated under semiintegral conditions.
Glass samples, doped with plutonium-239 and neptunium-237, were leached in the presence of environmental materials (sand, clay and granite) in 3 different test media:
a carbonated medium obtained by adding sodium bicarbonate;
an oxidative medium with a 2-bar oxygen partial pressure;
a reducing medium with a 2-bar partial pressure of argon and with the addition of 5% hydrogen.
A large fraction of the released activity was incorporated by the environmental materials present in the conditioning cell, notably by the clay. The actinide concentrations in the interstitial water and the amounts fixed on the granite were low.

The effects of the oxidation reduction potential and carbonate concentration on the alterability and containment properties of R7T7 glass were investigated under semiintegral conditions (ie by leaching glass samples doped with plutonium-239 and neptunium-237 in the presence of environmental materials (sand, clay and granite) in 3 different test media):
a carbonated medium obtained by adding sodium bicarbonate;
an oxidative medium with a 2 bar oxygen partial pressure;
a reducing medium with a 2 bar partial pressure of argon and 5% hydrogen additive.

Under the semiintegral test conditions, the normalised neptunium and plutonium mass losses varied by less than an order of magnitude for the different test media, but the following general tendencies were observed:
NL(Np) carbon dioxide > NL(Np) oxygen > NL(Np) hydrogen;
NL(Pu) oxygen > NL(Pu) carbon dioxide > NL(Pu) hydrogen.

A large fraction of the released activity was incorporated by the environmental materials present in the conditioning cell, notably by the clay. The actinide concentrations in the interstitial water and the amounts fixed on the granite were low.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Commissariat à l'Energie Atomique (CEA)
Address
Centre D'études Nucléaires De La Vallée Du Rhône Cité De Marcoule
30205 Bagnols-sur-cèze
France