Physical properties of glass for immobilization of high level radioactive waste

Mendel, J.E.; Ross, W.A.; Turcotte, R.P.; McElroy, J.L.

doi:10.1016/0191-815x(80)90025-x

“…Blending involves a two-stage decision process: assignment of individual tanks to a given blend and determination of frit requirements. The latter decision depends on the contents of each tank, and is governed by both analytical and empirical glass property models derived for the Hanford tank wastes (9,10). The resulting constraints pertain to the vitrification process -rather than characteristics of the subsequent glass -and include: bounds on the waste component mass fractions; crystallinity requirements; solubility limits; and attributes of the molten glass, including its viscosity, electrical conductivity, and liquidus temperature (8,11,12).…”

Section: Optimizing Vitrificationmentioning

confidence: 99%

Hanford waste blending and the value of research: stochastic optimization as a policy tool

Johnson¹,

Diwekar²

2001

J. Multi‐Crit. Decis. Anal.

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A new optimization framework is applied to management of radioactive wastes stored in belowground tanks at the US Government's Hanford, WA, nuclear fuels facility. Current remediation plans call for vitrification of the tank contents. Blending of the wastes prior to glass formation reduces the amount of material required for processing, therefore decreasing disposal costs. Uncertainty in the tank contents, the error inherent in the glass property models governing vitrification, and computational difficulties, however, render determination of an optimal tankblend assignment a challenge to existing optimization techniques. Previous studies have focused exclusively on minimization of processing and disposal costs, ignoring such management-related dimensions as the value of reducing select sources of uncertainty. Moreover, the stochastic framework employed by these studies could not guarantee that the glass property requirements were met on more than a probabilistic basis. This paper presents a more flexible, efficient, and robust optimization framework that facilitates analysis of the trade-off in reducing select sources of uncertainty. Specifically, the prediction error of the glass property models is found to be more significant than variation in tank component mass fraction estimates, and constraint violations are traced to the need to meet a limited set of glass property characteristics.

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“…The latter decision depends on the contents of each tank, and is governed by both analytical and empirical glass property models derived for the Hanford tank wastes (9,10). The resulting constraints pertain to the vitrification process -rather than characteristics of the subsequent glass -and include: bounds on the waste component mass fractions; crystallinity requirements; solubility limits; and attributes of the molten glass, including its viscosity, electrical conductivity, and liquidus temperature (8,11,12).…”

Section: Optimizing Vitrificationmentioning

confidence: 99%

Hanford waste blending and the value of research: stochastic optimization as a policy tool

Johnson

¹

,

Diwekar

²

2001

Multi Criteria Decision Anal

View full text Add to dashboard Cite

A new optimization framework is applied to management of radioactive wastes stored in belowground tanks at the US Government's Hanford, WA, nuclear fuels facility. Current remediation plans call for vitrification of the tank contents. Blending of the wastes prior to glass formation reduces the amount of material required for processing, therefore decreasing disposal costs. Uncertainty in the tank contents, the error inherent in the glass property models governing vitrification, and computational difficulties, however, render determination of an optimal tankblend assignment a challenge to existing optimization techniques. Previous studies have focused exclusively on minimization of processing and disposal costs, ignoring such management-related dimensions as the value of reducing select sources of uncertainty. Moreover, the stochastic framework employed by these studies could not guarantee that the glass property requirements were met on more than a probabilistic basis. This paper presents a more flexible, efficient, and robust optimization framework that facilitates analysis of the trade-off in reducing select sources of uncertainty. Specifically, the prediction error of the glass property models is found to be more significant than variation in tank component mass fraction estimates, and constraint violations are traced to the need to meet a limited set of glass property characteristics.

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“…Thermal stability of the glass matrix is crucial since glasses are metastable and under some conditions for crystal growth can partially convert to crystalline materials [188]. Each HLW storage canister is filled with molten waste glass by pouring several times.…”

Section: Devitrificationmentioning

confidence: 99%

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

Rautiyal¹

0

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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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Physical properties of glass for immobilization of high level radioactive waste

Cited by 11 publications

References 6 publications

Hanford waste blending and the value of research: stochastic optimization as a policy tool

Hanford waste blending and the value of research: stochastic optimization as a policy tool

Hanford waste blending and the value of research: stochastic optimization as a policy tool

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

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