An Experimental Study on the Influence of Gamma Radiation on Spent Fuel Dissolution in the Presence of a H 2 Atmosphere
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CC9.6.1
An Experimental Study on the Influence of Gamma Radiation on Spent Fuel Dissolution in the Presence of a H2 Atmosphere Javier Quiñones1, Jose Manuel Cobo1, Ángel González de la Huebra1, Aurora Martínez Esparza2 1
Nuclear Fission Department, Ciemat (Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas), Avda Complutense 22, 28040 Madrid, Spain, [email protected] 2 ENRESA (Empresa Nacional de Residuos Radiactivos), C/ Emilio Vargas 7, 28043 Madrid, Spain ABSTRACT Any environmental performance assessment of spent nuclear fuel disposal requires a prediction of the spent fuel matrix alteration rate when contact with groundwater is established. Taking into account the disposal design, the groundwater at the expected depth of the repository are generally reducing. These reducing redox conditions near the spent fuel surface may be changed to oxidising conditions by the radiolysis of water, due to radiation associated with the waste. This study is focussed on determining the influence of the γ radiation on the spent fuel matrix alteration rate under simulated repository conditions. A series of sequential leaching experiments under controlled conditions have been done. The experiments simulate the repository environmental conditions when engineering barriers are degraded and groundwater arrives at the surface of the spent fuel. In these experiments SIMFUEL (SIMulated FUEL) was used as analogue of spent fuel. Two types of leachant (i.e., granitic water and bentonitic-granitic water) were used in the leaching experiments. These experiments were irradiated using γradiation at an industrial irradiation facility with a 60Co source. The results obtained in this study show different behaviour as a function of both the leachant used in the leaching experiments and the initial atmosphere used in the experiments. As a preliminary conclusion of this experimental work, under γ radiation and a small partial pressure of H2 (1 bar) in the first steps of the leaching process has a beneficial effect since U in solution is lower than any other conditions and overall alteration rate is minimized. For experimental times longer than one day, a clear increase of the U in solution is revealed in the experimental run products. INTRODUCTION For Performance Assessment (PA) studies is necessary to predict and model long-term interactions between spent nuclear fuel and groundwater. These investigations usually apply different (thermodynamic and/or kinetic) models, based on experimental studies, in order to predict this behaviour (i.e., to define the dissolution rate of the spent fuel matrix and the rate of release of each radionuclide). The dissolution rate of the spent fuel depends on different parameters including the composition of the spent fuel and the environmental conditions (chemical composition of the groundwater, redox conditions, etc.) to which the spent fuel is exposed.
CC9.6.2
One of these parameters is the influence of the radiation emitted by spent fuel on the leaching dissolution rate [1]. As is rel
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