Trita-KET

A model for studying oxygen depletion in subsurfacefractured rock have been developed. It is based on currentknowledge in several different reasearch disciplines such asgeology, microbiology and hydrology. The model may be a usefultool for predicting oxygen penetration in rock fractures. Thisis important for example in the safety assessment of a deeprock nuclear waste repository. In such a repositroy a reducingenvironment is desirable. Several potential oxygen consumingprocesses, both parallel and serial, were identified, each ofwhich may considerably contribute to the depletion of oxygen.Abiotic as well as microbially mediated oxidation of rockminerals coupled with transport processes, both in thefractures and the rock matrix, were included. The model wasdivided into a number of case studies in which only one or afew processes were studied at a time. The different cases werethen compared so that the relative importance of each processcould be evaluated at different conditions. Even if it would bepossible to model all the processes simultaneously, thisapproach was chosen from result transparency and numericalefficiency reasons. The results show that in a relatively shorttime perspective, when oxidizable minerals are available in thefracture, reaction kinetics are important. In a long timeperspective, however, minerals in and adjacent to the fracturebecome oxidized and matrix diffusion is rate limiting. Lic.-avh. (sammanfattning) Stockholm : Kungliga Tekniska högskolan, 2003 Lic.-avh. (sammanfattning) Stockholm : Kungliga Tekniska högskolan, 2003 A model for studying oxygen depletion in subsurfacefractured rock have been developed. It is based on currentknowledge in several different reasearch disciplines such asgeology, microbiology and hydrology. The model may be a usefultool for predicting oxygen penetration in rock fractures. Thisis important for example in the safety assessment of a deeprock nuclear waste repository. In such a repositroy a reducingenvironment is desirable. Several potential oxygen consumingprocesses, both parallel and serial, were identified, each ofwhich may considerably contribute to the depletion of oxygen.Abiotic as well as microbially mediated oxidation of rockminerals coupled with transport processes, both in thefractures and the rock matrix, were included. The model wasdivided into a number of case studies in which only one or afew processes were studied at a time. The different cases werethen compared so that the relative impor