The influence of cover on transportation of radionuclides from low and intermediate level radioactive waste disposal facility

Uporaba radioaktivnih snovi v znanstvene namene, industriji, medicini, ter za pridobivanje jedrske energije povzroča nastajanje radioaktivnih odpadkov. Pred njihovimi škodljivimi učinki se lahko zavarujemo tako, da poskrbimo za njihovo varno odlaganje. Razumevanje transportnih mehanizmov v porozni snovi je ključno, da zagotovimo dolgotrajno varnost odlagališč radioaktivnih odpadkov. S pomočjo matematičnih modelov lahko opišemo podzemne tokove ter možne transporte radionuklidov iz odlagaliča skozi geološke formacije. V teoretičnem delu naloge so opisane fizikalne osnove radioaktivnosti, sistem razvrščanja radioaktivnih odpadkov ter odlagalne možnosti za nizko in srednje radioaktivne odpadke, katerim sledijo podatki o vrstah in količinah radioaktivnih odpadkov v Sloveniji. V nadaljevanju sledijo teoretične osnove toka podzemne vode ter z njo povezani prenosni pojavi v porozni snovi. Eksperimentalni del obsega izdelavo modela odlagališča nizko in srednje radioaktivnih odpadkov. Izdelana sta bila model odlagališča NSRAO brez prekrova ter model odlagališča NSRAO s prekrovom, na podlagi katerih smo primerjali vpliv prekrova na tok vode skozi odlagališče in transport radionuklidov cezija (137Cs) in joda (129I). Modeli in izračuni so bili izdelani s pomočjo programskega paketa HYDRUS-1D.The usage of radioactive substances in science, industry, medicine and nuclear power plants is generating radioactive waste. The only way we can effectively protect ourselves from their deleterious effects is by appropriate waste disposal. In order to secure long-term safety of the disposal facilities, we have to understand the transport mechanisms in porous materials. We can then use mathematical models to describe the underground currents and possible transportation routes of radionuclides from the disposal facilities through geological formations. Theoretical part of the thesis contains the description of physical principles of radioactivity, classification system of radioactive waste and disposal possibilities for low-level and intermediate waste with information on type and quantity of radioactive waste in Slovenia. Theoretical basis of groundwater flow and related phenomena of flow in porous materials is also described. Experimental part describes the making of mathematical models for disposal facilities, that deal with low and intermediate level waste (LILW). First model describes the disposal of LILW without cover, the second describes the disposal of LILW with cover layer. The results were summarized and indicate the influence of cover on groundwater flow through hazardous waste dump and transportation of radionuclides of Caesium (137Cs) and Iodine (129I). Models and calculations were made with HYDRUS- 1D software