Alpha-radiolysis effects on UO2 alteration in water

The behaviour of UO2/water interface under irradiation has been investigate d as a function of alpha flux using an alpha beam provided by a cyclotron. The effects of alpha-radiolysis on UO2 alteration in aerated deionized wate r were studied by characterizing both the chemistry of irradiated aqueous s olutions and the UO2 surface. Uranium (as uranyl ion UO22+) and hydrogen pe roxide concentration (H2O2) increased whereas pH decreased in the irradiate d solutions when alpha-beam flux increased. The formation of hydrated urani um peroxide (metastudtite UO4. 2H(2)O) on UO2 leached surface was identifie d by X-ray diffractometry. The production of metastudtite can be considered as a direct effect of water radiolysis due to the production of radiolytic species H2O2 since its formation is known to occur out of irradiation via a precipitation reaction between hydrogen peroxide and uranyl ion. From bot h these observations and literature about hydrated uranium peroxide occurre nce, the possibility of metastudtite formation on nuclear spent fuel in sto rage conditions is discussed. (C) 2001 Elsevier Science B.V. All rights res erved.