Radioactive waste management is an international techno-scientific and socio-politic problem. Countries that use radioactivity must manage radioactive waste in safety way in order to safeguard population and environment from radiological risks. Safety assessment techniques are used to evaluate the performance of the disposal facility and its impact on human health and environment, during the lifetime of the facility. The final goal is a qualitative and quantitative estimation of the possible radiological risk due to a radioactive source. Safety assessment studies need continue improvements to be able to manage all involved aspects and the evolution of technological and scientific innovation. For this reason, safety case and safety assessment studies are discussed by the international nuclear scientific and research community. The research activity performed during 2013-2016 PhD years can be included in this context. It was developed in collaboration with ENEA (Italian National Agency for New Technologies, Energy and Sustainable Economic Development), coupling different background knowledge necessary to analyze these multidisciplinary topics. Methodological approaches to study the radionuclide transport in environment were investigated. In particular, the modelling of radionuclide transport in groundwater and subsoil was carried out to predict possible accidental leakage of radionuclides from a nuclear facility into the environment. The thesis is divided in four main topics: the investigation of unsaturated zone (part of the subsoil above the water table level); the analysis of the saturated zone (part of the subsoil below the water table level); the coupling of unsaturated zone and saturated zone models; the introduction of some geochemical aspects. The unsaturated zone is characterized by complex physico-chemical phenomena, that strongly influence water flow and radionuclide transport dynamic. The integration of different techniques, such as isotopic analysis, tracer test, and modelling allowed to estimate the barrier effect of the unsaturated zone, which delays the radionuclide transport towards groundwater. The saturated zone can host aquifers where water is collected for human purposes. For this reason, it must be strictly safeguarded. A step-by-step approach focused on the investigation of groundwater dynamics and radiological source terms was applied and different scenarios were analyzed in order to identify the areas that can be involved by radiological risks. The coupling of unsaturated zone and saturated zone was assessed to be fundamental in the development of safety assessment studies that investigate radionuclide transport into the environment. A methodological approach was proposed and promising results were obtained to spend future effort on this topic. Finally, geochemical aspects were introduced and preliminary information on the interaction between radionuclide and environment were estimated. The applied methodological approaches can be introduced in safety assessment studies of disposal facility to estimate how perform mitigation actions in accident case or how plan radiological and environmental monitoring network.

Modelling of radionuclide transport in groundwater and subsoil for Safety Assessment studies / Testoni, Raffaella. - (2016).

Modelling of radionuclide transport in groundwater and subsoil for Safety Assessment studies

TESTONI, RAFFAELLA
2016

Abstract

Radioactive waste management is an international techno-scientific and socio-politic problem. Countries that use radioactivity must manage radioactive waste in safety way in order to safeguard population and environment from radiological risks. Safety assessment techniques are used to evaluate the performance of the disposal facility and its impact on human health and environment, during the lifetime of the facility. The final goal is a qualitative and quantitative estimation of the possible radiological risk due to a radioactive source. Safety assessment studies need continue improvements to be able to manage all involved aspects and the evolution of technological and scientific innovation. For this reason, safety case and safety assessment studies are discussed by the international nuclear scientific and research community. The research activity performed during 2013-2016 PhD years can be included in this context. It was developed in collaboration with ENEA (Italian National Agency for New Technologies, Energy and Sustainable Economic Development), coupling different background knowledge necessary to analyze these multidisciplinary topics. Methodological approaches to study the radionuclide transport in environment were investigated. In particular, the modelling of radionuclide transport in groundwater and subsoil was carried out to predict possible accidental leakage of radionuclides from a nuclear facility into the environment. The thesis is divided in four main topics: the investigation of unsaturated zone (part of the subsoil above the water table level); the analysis of the saturated zone (part of the subsoil below the water table level); the coupling of unsaturated zone and saturated zone models; the introduction of some geochemical aspects. The unsaturated zone is characterized by complex physico-chemical phenomena, that strongly influence water flow and radionuclide transport dynamic. The integration of different techniques, such as isotopic analysis, tracer test, and modelling allowed to estimate the barrier effect of the unsaturated zone, which delays the radionuclide transport towards groundwater. The saturated zone can host aquifers where water is collected for human purposes. For this reason, it must be strictly safeguarded. A step-by-step approach focused on the investigation of groundwater dynamics and radiological source terms was applied and different scenarios were analyzed in order to identify the areas that can be involved by radiological risks. The coupling of unsaturated zone and saturated zone was assessed to be fundamental in the development of safety assessment studies that investigate radionuclide transport into the environment. A methodological approach was proposed and promising results were obtained to spend future effort on this topic. Finally, geochemical aspects were introduced and preliminary information on the interaction between radionuclide and environment were estimated. The applied methodological approaches can be introduced in safety assessment studies of disposal facility to estimate how perform mitigation actions in accident case or how plan radiological and environmental monitoring network.
2016
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11583/2643122
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