RADIOLYSIS OF CLAY-WATER SYSTEMS - APPLICATION TO THE STORAGE OF RADIOACTIVE-WASTE

The long-term storage of radioactive waste buried in deep geological f ormations raises numerous problems due to the radiolysis of the ground . In order to evaluate the consequences of the radiolytic reactions wh ich will take place in the ground, we are studying the effect of gamma irradiation on the clay Fo-Ca 7 and on the clay water. Concerning irr adiation of the solid phase, the lixiviation of Fe2+ in acidic water i ncreases with the dose, probably as a consequence of structural modifi cations.The non-irradiated clay water has reducing properties which ar e diminished upon irradiation. Clay water contains several unidentifie d efficient OH scavengers. As a consequence, the yield of hydrogen per oxide is higher in clay water than in pure water. The mechanism of H2O 2 formation and decay has been studied in clay water and a kinetic sch eme is proposed which allows the computation of the H2O2 amont for dos es up to ca. 20,000 Gy. The efficient scavenging of OH free radicals i s also consistent with a massive radiolytic formation of dihydrogen.