Structural characterization of sulphate and chloride doped glasses for radioactive waste immobilisation

Vaishnav, Shuchi

doi:10.7190/shu-thesis-00114

Cited by 1 publication

(17 citation statements)

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“…3) Very low-level waste (VLLW): This category of waste does not require special containments and isolation, but it does not fall in the category of exempted waste either and, therefore, it is disposed of in near-surface landfill sites with consideration of regulatory and safety provisions set for this kind of waste [5,100,101]. Waste in this category may arise from rehabilitation and dismantling of industrial sites and the mining or processing of ores and minerals.…”

Section: Reprocessing Of Spent Nuclear Fuelmentioning

confidence: 99%

“…Vitrification is defined as a process of incorporating radionuclides in a solid glassy waste form by melting at suitable temperatures [100]. This provides the HLW in a suitable solid form which can be stored and transported for eventual geological disposal.…”

Section: Hlw Immobilisation -Vitrificationmentioning

confidence: 99%

“…This provides the HLW in a suitable solid form which can be stored and transported for eventual geological disposal. Vitrification technology is used by many countries including USA, France, UK, India, Germany, Japan, China, Russia, South Korea for immobilising mainly HLW, however, countries such as USA, Russia and S. Korea have been using it to treat certain LLW and ILW [21,24,100,123]. Borosilicate glasses have been the globally preferred choice for the vitrification of HLW and some LAW since they meet the maximum desirable characteristics of a suitable waste form for long term safe and economic storage while many countries are researching and pursuing alternative waste forms such as glass ceramics (borosilicate glasses are discussed later in this thesis in detail) [10,63,93,112,118,124,125].…”

Section: Hlw Immobilisation -Vitrificationmentioning

confidence: 99%

“…Figure 2.12 shows the glass structure as described by the first three rules, with a tetrahedron labelled MO4. These rules were formulated for glasses made from simple oxides [100,106,145,153]. Zachariasen's rules described the condition required for formation of a glass but several theories and models to explain glass structure took these as their basis [106,154,155].…”

Section: Structure Of Vitreous Silica and Silicate Glassesmentioning

confidence: 99%

“…The theories for alkali/alkaline earth silicate glasses cannot be directly applied to borate or borosilicate glasses, as silicon can exist only in the 4-coordinated state in these glass networks, whereas boron can exist both in trigonal (3-fold coordinated, BO3 triangles) and tetrahedral (4-fold coordinated BO4 tetrahedra) structural units within the glass network [100,106,145]. Before understanding the structure of borosilicate glasses, it is therefore helpful to briefly discuss the structure of borate glasses.…”

Section: Structure Of Vitreous Silica and Silicate Glassesmentioning

confidence: 99%

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Radiation damage effects on the structure and properties of radioactive waste glasses

Rautiyal¹

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The performance assessment of glass matrices currently being used in different nuclear energy producing countries to contain and immobilise high-level waste (HLW) waste is crucial for safe and economic disposal. During the first ~500 years of geological disposal fission products will me the main source or radiation and they decay by beta-gamma emission. We studied different borosilicate glasses used in different countries to immobilise HLW, such as Indian glass (NaBaBSi), UK glasses (LiNaBSi), also called MW- Mixture Windscale, UK-CaZn a modified version of MW, French glass (SON68) and a glass proposed by six collaborating nations, called the International Simple Glass (ISG), to see whether / how irradiation defects are dependent on glass composition. Glasses were externally irradiated using a 60Co gamma source to study the effects of beta-gamma radiation (a gamma emitter loses it energy to atomic electrons they then further interact via coulombic interactions); and by He2+ ion implantation to study the effects of alpha particles. A multi-spectroscopic approach was used to characterise glass specimens before and after irradiation. NaBaBSi and LiNaBSi glasses were irradiated using 60Co gamma photons and we found boron-oxygen hole centres (BOHC), electrons trapped at alkali cations or ET centres and peroxy-radicals (PORs) as common defect in these glasses. In addition, E- or polaron centres which may be related to formation of elemental / metallic sodium colloids formed in NaBaBSi glass. Time-dependent thermal annealing of the irradiated glasses revealed that POR’s are the most thermally stable of the defect centres. BOHC and ET centres were common to SON68, ISG and CaZn glasses. In NaBaBSi, LiNaBSi and SON68 glasses loaded with non-active simulated HLW no sharp and intense signals indicative of radiation-induced paramagnetic defect centres was observed. In the study of NaBaBSi and LiNaBSi glasses doped with 0.19. 0.99, and 4.76 mol% Fe2O3 prepared in an oxidising melting environment, electron paramagnetic resonance (EPR) spectroscopy showed that gamma irradiation induced sharp and intense signals exist for only the 0 and 0.19 mol% Fe2O3 doped samples and disappeared for samples containing higher molar concentrations of Fe2O3. It is postulated that, upon gamma irradiation, in LiNaBSi glass Fe2+ is oxidised to Fe3+ by the capture of holes, whereas in NaBaBSi glass Fe3+ is reduced to Fe2+ due to capture of electrons. Further research is needed to understand the reasons behind these different behaviours.

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Section: Reprocessing Of Spent Nuclear Fuelmentioning

confidence: 99%

Section: Hlw Immobilisation -Vitrificationmentioning

confidence: 99%