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dc.contributor.advisorPurcelI, W.
dc.contributor.advisorNel, J. T.
dc.contributor.advisorSnyders, E.
dc.contributor.authorNkabiti, Litheko Legapa
dc.date.accessioned2017-06-05T06:33:01Z
dc.date.available2017-06-05T06:33:01Z
dc.date.issued2012-11
dc.identifier.urihttp://hdl.handle.net/11660/6329
dc.description.abstractEnglish: Zirconium occurs in nature as a component of the lithosphere in various molecular fractions within a number of mineral ores. Since its discovery in 1789, many chemical processes have been developed to have zirconium in its pure and malleable form for different uses in various industries. These industries include the nuclear, jewellery, medicine and cosmetic industries. It is considered extremely important in the nuclear industry and is used, for example, in the aligning of nuclear arcs, its chemical and radiation resistance, metallurgical properties as well as its low thermal neutron capture cross section. For this purpose the metal has to be extremely pure (>99.9 %) and devoid of the elements which can render it unusable as fuel rod cladding material in the nuclear reactor. The objectives of this study were to: i) develop an alternative digestion method for zirconium to hydrofluoric acid, ii) develop an effective and efficient analytical method for the multi-element quantification of zirconium and its associated impurities in ultra-pure metal (foil: >99.98 % and rod: >99 %) and zirconium(IV) tetrafluoride samples at threshold and one-tenth of threshold by using commercially available equipment such as ICP-OES, iii) identify and compare the different analytical techniques and iv) determine the LOO/LOO of zirconium and its associated impurities and perform method validation on these analytical methods. Various digestion techniques, including individual mineral acids and their combinations, as well as microwave-assisted digestion were investigated with varying degrees of success. These included bench-top and microwave digestions with sulphuric acid (98 %), phosphoric acid (80 %) and aqua regia (nitric acid (55 %):hydrochloric acid (32 %), 3:1). The bench-top digestions of the zirconium rod samples by mineral acids gave average zirconium recoveries of 100.6 % for the sulphuric acid, 57.6 % and 89.6 % for phosphoric acid and aqua regia respectively, while the average recoveries for the bench-top digestions of the zirconium foil were 101.9 % for the sulphuric acid, 100.8 % and 85.1 % for the phosphoric acid and aqua regia, respectively. Microwave-assisted digestions of the metal samples with these mineral acids gave an average of 88.2 % for the phosphoric acid digestion, 100.2 % and 100.3 % for the sulphuric acid and aqua regia respectively for the zirconium rod digestion. The zirconium recoveries for the metal rod gave average recoveries of 32.7 %, 5.6 % and 97.4 % for phosphoric acid, aqua regia and sulphuric acid, respectively. Excellent recoveries for the zirconium(IV) tetrafluoride dissolutions were obtained at 99.5 % at the optical emission wavelengths of 343.823 nm and 101.7 % at 339.198 nm. Trace elements, which included aluminium, chromium and silicon, were quantified in this sample at 1.9 ppm, 0.1 ppm and 0.5 ppm, respectively. Potassium hexafluorozirconate was obtained by reacting KF and ZrF4 and gave zirconium recoveries of 100.9 % at 343.823 nm and 100.5 % at 339.198 nm. The product was also characterized using IR and the quantification of K using AA. The LOO and LOQ for zirconium were determined to be about 4 ppb at the two most sensitive wavelengths (343.823 nm and 339.198 nm) for the zirconium quantification. The elements were first quantified individually at one-tenth of the threshold and at the threshold of their permissible concentrations in the nuclear grade zirconium. The results obtained ranged from 98 % to 103 %. The elements were then batched into 3 groups which were quantified respectively, followed by their combinations and ultimately all the elements were quantified in a single batch at one-tenth of the threshold and at the threshold. The results obtained ranged from 99 % to 102 % for Group 1 (AI, Cr, Hf and Fe), 98 % to 102 % for Group 2 (B, Cd, Co, Cu and Mn) and 100 % to 102 % for Group 3 (Mo, Ni, Si, Ti, Wand U) at threshold recovery. Recoveries between 98 % and 103 % for Group 1, 99 % and 101 % for Group 2 and 99 and 102 % for Group 3 elements were obtained at one-tenth of the threshold. The quantification results obtained for the element combinations of Groups 1 and 2 at the threshold concentrations ranged from 99 % to 102 %, which were similar also for Groups 1 and 3 combinations while 98 % to 103.5 % were obtained for the Groups 2 and 3 combinations. At one-tenth of the threshold the recoveries were obtained between 98 % and 102 % for Groups 1 and 2, 70 % and 103.5 % for Groups 1 and 3 while 4 % and 102 % were achieved for Groups 2 and 3. In the quantitative analyses of all the elements combined, recoveries between 98.8 % and 102.3 % were obtained at threshold recovery while 97.8 % and 102 % were obtained at one-tenth of the threshold concentrations. Poor recoveries at one-tenth of the threshold for boron, cadmium and uranium were obtained in the quantifications of the element mixtures - this was due to these elements being quantitatively analyzed close to their LOQ's. The experimental results obtained for the quantitative analyses of zirconium and its specified impurities for nuclear purposes were validated using the hypothesis test of the t-statistic value (tcrit of ±2.31 for the pooled results in the quantification of zirconium metal samples and tcrit of ±4.30 for the quantitative analyses of zirconium and its impurities) at 95 % confidence interval to determine the acceptability of the results as recommended by IS017025. Other statistical parameters, such as the accuracy, precision and specificity, were investigated and the results were shown to be reproducible for all the experimental measurements.en_ZA
dc.description.abstractAfrikaans: Sirkonium kom in die natuur voor as 'n komponent van die litosfeer. Dit is teenwoordig in verskeie molekulêre fraksies in seker minerale ertse. Sedert die ontdekking daarvan in 1789, is verskeie chemiese prosesse ontwikkelom sirkonium vir verskillende gebruike in verskeie industrieë in sy suiwerste en mees smeebare vorm te produseer. Hierdie nywerhede sluit in die kern-, juweliersware-, medisyne- en kosmetiese industrieë. Dit word as uiters belangrik in die kernindustrie beskou vir die rig van die kernboë, sy chemiese en radiologiese weerstand, metallurgiese eienskappe en 'n lae-termiese-neutron-opvangsdeursnit. Vir hierdie doel moet die metaal baie suiwer (>99 %) en vry van elemente wees wat dit onbruikbaar kan maak as brandstofstaaf-bekledingsmateriaal in die kernreaktor. Die doel van hierdie studie was om: i) die ontwikkeling van 'n alternatiewe verteringsmetode as fluoorsuur te ondersoek, ii) die ontwikkeling van 'n effektiewe en doeltreffende analitiese metode te ontwikkel vir die multi-element kwantifisering van sirkonium en sy verwante onsuiwerhede in 'n ultra-suiwer metaal (foelie: >99.98 % en staaf: >99 %) en sirkoniumtetrafluoriedmonsters by drempel en 'n eentiende van die drempel deur die gebruik van kommersieel-beskikbare toerusting soos IGP-OES, iii) verskillende analitiese tegnieke te identifiseer en te vergelyk en iv) om uiteindelik die LOO/LOO van sirkonium en sy geassosieerde onsuiwerhede te bepaal en gevolglik die validasie op hierdie analitiese metodes uit te voer. Verskeie verteringstegnieke, insluitende individuele mineralesure en hul kombinasies, sowel as mikrogolfvertering, is met wisselende grade van sukses ondersoek. Dit sluit in laboratoriumskaal- en mikrogolfverterings met swawelsuur (98 %), fosforsuur (80 %) en aqua regia (salpetersuur (55 %):soutsuur (32 %), 3:1). Die laboratoriumskaalverterings van die sirkoniumbasis-monsters deur minerale sure, het gemiddelde opbrengs van 100.6 % vir die swawelsuur, 57.6 % en 89.6 % vir fosforsuur en aqua regia, onderskeidelik gelewer, terwyl die gemiddelde opbrengs vir die vertering van die sirkoniumfoelie 101.9 % vir die swawelsuur, 100.8 % en 85.1 % en vir die fosforsuur en aqua regia, onderskeidelik was. Mikrogolf-gesteunde verterings van die metaalmonsters met hierdie minerale sure het 'n gemiddeld van 88.2 % vir die fosforsuur-vertering, 100.2 % en 100.3 % vir die swawelsuur en aqua regia onderskeidelik vir die sirkoniumstaaf-vertering. Die sirkoniumopbrengs vir die metaalstaaf het 'n gemiddeld van 32.7 %, 5.6 % en 97.4 % vir fosforsuur, aqua regia en swawelsuur, onderskeidelik behaal. Uitstekende opbrengs vir die sirkonium(IV)tetrafluoriedverbindings is verkry teen 99.5 % by optiese emissie golflengte van 343.823 nm en 101.7 % by 339.198 nm. Spoorelemente, wat aluminium, chroom en silikon insluit, is in hierdie steekproef gekwantifiseer op 1.9 dpm, 0.1 dpm en 0.5 dpm, onderskeidelik. Kaliumheksafluorosirkonaat is verkry deur die reaksie van KF met ZrF4, en het sirkoniumopbrengste van 100.9 % by 343.823 nm en 100.5 % by 339.198 nm gelewer. Die produk is ook gekarakteriseer is met behulp van IR en kwantifisering van K met die gebruik van AA. Die LOO en LOO vir sirkonium is bereken as opgeveer 4 dpb by die twee mees sensitiewe golflengtes (343.823 nm en 339.198 nm) vir die sirkonium-kwantifisering. Die elemente is vir die eerste keer individueel gekwantifiseer teen eentiende van die drempel en op die drempel van hul toelaatbare konsentrasies in die kerngraad-sirkonium. Die resultate wat verkry is, het gewissel van 98 % tot 103 %. Daarna is die elemente in 3 groepe verdeel wat onderskeidelik gekwantifiseer is, gevolg deur hul kombinasies en uitendelik is al die elemente in 'n groep op eentiende van die drempel en op die drempel gekwantifiseer. Die resultate wat verkry is, het gewissel van 99 % tot 102 % vir Groep 1 (AI, Cr, Hf en Fe), 98 % tot 102 % vir Groep 2 (B, Cd, Co, Cu en Mn) en 100 % tot 102 % vir Groep 3 (Mo, Ni, Si, Ti, W en U) op drempel. Opbrengs van tussen 98 % en 103 % vir Groep 1, 99 % en 101 % vir Groep 2 en 99 % en 102 % vir Groep 3 elemente is verkry op eentiende van die drempel. Die kwantifiseringsresultate wat verkry is vir die elementkombinasies van Groepe 1 en 2 op die drempelkonsentrasies het gewissel van 99 % tot 102 %, wat dieselfde was vir Groepe 1 en 3 kombinasies, terwyl 98 % tot 103.5 % verkry is vir die Groepe 2 en 3 kombinasies. By eentiende van die drempel is die opbrengs verkry tussen 98 % en 102 % vir Groepe 1 en 2, 70 % en 103.5 % vir Groepe 1 en 3 terwyl 4 % en 102 % verkry is vir Groepe 2 en 3. Tydens die kwantitatiewe analise van al die elemente gekombineer, is opbrengste van tussen 98.8 % en 102.3 % verkry by die drempelherwinning, terwyl 97.8 % en 102 % verkry is op eentiende van die drempelkonsentrasies. Swak opbrengs op eentiende van die drempel is vir die boor, kadmium en uraan verkry in die kwantifisering van die elementmengsels. Die rede hiervoor was dat hierdie elemente kwantitatief nabyaan hul LOO ontleed word. Die eksperimentele resultate wat verkry is vir die kwantitatiewe analise van sirkonium en sy gespesifiseerde onsuiwerhede vir kerndoeleindes, is gevalideer met behulp van die hipotese toets van die t-statistiese waarde (tkril van ± 2.31 vir die gesamentlike resultate in die kwantifisering van sirkonium en sy onsuiwerhede) by 95 % vertroue-interval om die aanvaarbaarheid van die resultate, soos aanbeveel deur die IS017025, te bepaal. Ander statistiese parameters, soos die akkuraatheid, presisie en spesifisiteit, is ondersoek en die resultate blyk herhaalbaar te wees vir al die eksperimentele bepalings.af
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectDetection limitsen_ZA
dc.subjectDigestionen_ZA
dc.subjectDissolutionen_ZA
dc.subjectHigh purityen_ZA
dc.subjectICP-OESen_ZA
dc.subjectImpuritiesen_ZA
dc.subjectMatrix/Matricesen_ZA
dc.subjectNuclear gradeen_ZA
dc.subjectZirconiumen_ZA
dc.subjectZirconium compundsen_ZA
dc.subjectDissertation (M.Sc. (Chemistry))--University of the Free State, 2012en_ZA
dc.titleMethod validation for the quantification of impurities in Zirconium metal and other relevant Zr compounds.en_ZA
dc.typeDissertationen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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