Botha, J. F.Van Blerk, J. J.2018-04-052018-04-052000http://hdl.handle.net/11660/8115Thesis (Ph.D. (Geohydrology))--University of the Free State, 2000𝑬𝒏𝒈𝒍𝒊𝒔𝒉 Radioactive waste in South Africa is generated through the nuclear fuel cycle and the application of radioactive materials in industry, science and medicine. The radioactive waste is presently disposed at Vaalputs in Bushmanland and Thabana at Pelindaba in near-surface disposal facilities. No strategy exists at present for the disposal of high level waste. The objective of radioactive waste management and its underlying principles is to ensure that human health and the environment are protected at all times, without imposing an undue burden on future generations. This implies that, before any long-term management strategy of radioactive waste disposal can be implemented, the impact of the disposed waste must be determined as a function of time-a procedure referred to as post-closure safety assessment. In this thesis, a methodology to perform post-closure safety assessments of radioactive waste disposal systems in South Africa and other parts of Africa is described. Not only will it contribute significantly to reassess the suitability of current waste disposal practices, but also lays the foundation for future disposal practices. The proposed methodology-an integrated approach to radioactive waste management-is aimed at: (a) ensuring the safety of the present public and future generations, (b) enhancing the public acceptance of the methodology, (c) keeping the expenditure associated with the implementation of the methodology at a minimum. The methodology recognises the interdependence between operational phase activities and the post-closure behaviour of the disposal system. It is an iterative process that considers site-specific, prospective evaluations of the post-closure phase to ensure that the disposal system will comply with internationally accepted criteria, within reasonable limits. Provision is therefore made to identify the data, design and other needs that will contribute towards the achievement of this objective. The first step in this procedure is to identify those internal and external features, events and processes that can be used to predict how radioactive material may escape from the disposal facility, along which paths will it migrate and how it may impact humans. Various conceptual and mathematical models that can be used to develop appropriate scenarios of these processes and to compare the results with site specific data are discussed in the thesis. The cost to develop a waste disposal system, the disposal of the waste and the pre- and post closure assessments of the system, or so-called nuclear liabilities, can be astronomically high. Combining the post-closure assessment of the system with the decision analysis framework discussed in the thesis can reduce these costs considerably. Post-closure assessments of radioactive waste disposal systems have in the past often been interpreted as an exercise to predict the exact behaviour of the system far into the future. However, as pointed out in the thesis this is not possible, even with the technology available today. The more pragmatic approach, advanced in the thesis, is that modem technology is able to demonstrate to reasonable members of the public that such a system will be safe. Nevertheless it is recognized that the methodology cannot be implemented without the active participation of the public. It is therefore envisaged that the proposed methodology will be implemented with the close co-operation of the public, particularly those living near the site where the disposal system will be implemented.𝑨𝒇𝒓𝒊𝒌𝒂𝒂𝒏𝒔 In Suid Afrika word radioaktiewe afval gegenereer deur die kernbrandstofsiklus en die gebruik van radioaktiewe bronne in die industrie, die wetenskap en geneeskunde. Lae en middel energie radioaktiewe afval word tans weggedoen in oppervlak wegdoeningsfasiliteite by Vaalputs in die Boesmanland en geberg in vlak bergingsfasiliteite by Thabana by Pelindaba. Geen strategie bestaan egter tans vir die wegdoening van hoë energie afval nie. Die doel van radioaktiewe afvalbestuur en die onderliggende beginsels daarvan, is om te verseker dat die mens se gesondheid asook die omgewing te alle tye beskerm word, sonder om onnodige druk op toekomstige geslagte te plaas. Dit impliseer dat, alvorens enige langtermyn bestuurstrategie vir radioaktiewe afval geïmplementeer kan word, moet die impak van die gebergde afval as 'n funksie van tyd bepaal word-'n prosedure waarna verwys word as 'n nasluiting veiligheidsvasstelling (post-closure safety assessment). 'n Metodiek om so 'n nasluiting veiligheidsvasstelling vir radioaktiewe afval wegdoeningsisteme in Suid Afrika en ander dele van Afrika uit te voer, word in hierdie proefskrif beskryf. Nie alleen bied dit 'n beduidende bydrae tot die herevaluering van bestaande wegdoeningsisteme nie, maar verskaf dit ook 'n basis vir toekomstige wegdoeningspraktyke wêreldwyd. Die voorgestelde metodiek-'n geïntegreerde benadering tot radioaktiewe afvalbestuurhet ten doelom: (a) die veiligheid van huidige en toekomstige geslagte te verseker, (b) publieke aanvaarding van die metodiek te bevorder, (c) finansiële uitgawes geassosieer met die implementering van die metodiek te minimeer. Die metodiek aanvaar die interafhanklikheid wat daar bestaan tussen aktiwiteite binne die operasionale fase en die nasluitingsgedrag van die sisteem. Dit is 'n iteratiewe proses wat bestaan uit terrein spesifieke, toekomstige evaluasies van die nasluiting fase, met die doel om te verseker dat die wegdoeningsisteem voldoen aan internasionaal aanvaarbare kriteria, gegee sekere redelike beperkings. Gevolglik word voorsiening gemaak vir die identifisering van data, ontwerp en ander behoeftes wat 'n bydrae saliewer om die doelwit te bereik. Die eerste stap in hierdie prosedure is om alle interne en eksterne eienskappe, gebeurtenisse en prosesse (features, events and processes) te bepaal wat gebruik kan word om te voorspel hoe radioaktiewe materiaal vanuit die wegdoeningsfasiliteit kan ontsnap, langs watter paaie dit sal beweeg en wat die gevolglike impak op die mens sal wees. Verskeie konsepsuele en wiskundige modelle wat gebruik kan word om die prosesse voor te stel en die resultate met terrein spesifieke data te vergelyk, word in die proefskrif bespreek. Die koste om so 'n radioaktiewe afval wegdoeningsisteem te ontwikkel, die wegdoening van die afval en die ondersoeke wat nodig is om vas te stelof so 'n sisteem veilig sal wees, algemeen bekend as kernaanspreeklikheid, kan astronomies hoog wees. Soos aangetoon in die proefskrifkan hierdie kostes egter aansienlik verminder word deur die nasluitingsevaluasie van die sisteem met 'n besluitnemingsanalise raamwerk te kombineer. Nasluitingsevaluasies van radioaktiewe afval wegdoeningsisteme is dikwels in die verlede geïnterpreteer as ' n oefening wat daarop ingestel is om die werklike verre toekomstige gedrag van die sisteem te voorspel. Soos in die proefskrif aangedui word, is dit egter nie moontlik nie, self nie eers met die tegnologie wat vandag beskikbaar is nie. Wat die moderne tegnologie wel in staat is om te doen, is om aan te toon dat so 'nsisteem binne aanvaarbare perke veilig is. 'n Meer pragmatiese benadering word dus in die proefskrif voorgestel, nl. om aan redelike persone aan te dui dat so ' n sisteem wel veilig sal wees. Die metodiek kan dus nie geïmplementeer word sonder die aktiewe deelname van die publiek nie. Die sukses van die voorgestelde metodiek sal dus hoofsaaklik bepaal word deur die samewerking van die publiek, veral dié persone wat naby 'n terrein woon wat vir so 'n wegdoeningsisteem geoormerk is.enRadioactive waste disposal -- South AfricaNuclear power plant -- Waste disposal -- Environmental aspects -- South AfricaRadioactive waste disposal -- Safety measuresThesisUniversity of the Free State