The role of engineered barriers in a UK repository for intermediate level radioactive waste

Crossland, I. G.

doi:10.1179/030801898789764570

Cited by 6 publications

(7 citation statements)

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“…The current UK concept for the disposal of low-and intermediate-level wastes (L/ILW) involves a mined geological disposal facility (GDF) several hundreds of metres below the surface (Crossland, 1998;Nirex 1989;NDA, 2010). The waste will be encapsulated in a cement grout matrix within steel or concrete containers, and placed in disposal vaults backfilled with a cement-based material.…”

Section: Introductionmentioning

confidence: 99%

A long-term experimental study of the reactivity of basement rock with highly alkaline cement waters: Reactions over the first 15 months

et al. 2016

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A series of long-term laboratory experiments was started in 1995 to investigate longer-term dissolution/precipitation reactions that may occur in the alkaline disturbed zone surrounding a cementitious repository for radioactive waste. They consist of samples of UK basement rock reacting with either Na-K-Ca-OH water ('young' cement porewater) or Ca-OH water ('evolved' cement porewater) at 70°C. This paper summarises results of reactions occurring over the first 15 months. Experiments of both fluid types showed many similar features, though primary mineral dissolution and secondary mineral precipitation were more extensive in the experiments involving Na-K-Ca (younger) cement porefluids compared to more evolved (Ca-rich) cement porefluids. Dissolution of dolomite, and to a lesser extent silicates (most probably K-feldspar, but possibly also mica) occurred relatively rapidly at 70 °C. Dolomite dissolution may have been a key factor in reducing pH values, and may be a key mineral in controlling the extent of alkaline disturbed zones. Dissolution was followed by precipitation of brucite close to dolomite grains, at least two generations of CSH phases

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Section: Introductionmentioning

confidence: 99%

A long-term experimental study of the reactivity of basement rock with highly alkaline cement waters: Reactions over the first 15 months

et al. 2016

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“…Concerns about radioactive contamination originating from nuclear waste disposal have led to an extensive range of research investigations into the confinement of radioactive waste, − the migration of radionuclides in various natural environments, − the influence of microbial effects − and ultimately radionuclide uptake in exposed human populations. , The mobility and fate of radioactive contaminants in engineered and natural environments, as well as in living organisms, is influenced by their chemical speciation in relevant systems, such as chemical forms, oxidation states, and colloid formation. For this reason, the chemical speciation of radioactive contaminants has been extensively investigated. − …”

Section: Introductionmentioning

confidence: 99%

Solution Speciation of Plutonium and Americium at an Australian Legacy Radioactive Waste Disposal Site

Ikeda‐Ohno

Harrison²,

Thiruvoth³

et al. 2014

Environ. Sci. Technol.

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During the 1960s, radioactive waste containing small amounts of plutonium (Pu) and americium (Am) was disposed in shallow trenches at the Little Forest Burial Ground (LFBG), located near the southern suburbs of Sydney, Australia. Because of periodic saturation and overflowing of the former disposal trenches, Pu and Am have been transferred from the buried wastes into the surrounding surface soils. The presence of readily detected amounts of Pu and Am in the trench waters provides a unique opportunity to study their aqueous speciation under environmentally relevant conditions. This study aims to comprehensively investigate the chemical speciation of Pu and Am in the trench water by combining fluoride coprecipitation, solvent extraction, particle size fractionation, and thermochemical modeling. The predominant oxidation states of dissolved Pu and Am species were found to be Pu(IV) and Am(III), and large proportions of both actinides (Pu, 97.7%; Am, 86.8%) were associated with mobile colloids in the submicron size range. On the basis of this information, possible management options are assessed.

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“…Encapsulation and immobilisation in cement-based materials is the favoured method in the UK for the passiva-23 tion of intermediate level radioactive waste (ILW) 1 . Composite cements based on the replacement of OPC with 24 either pulverised fuel ash (PFA) or blast furnace slag (BFS) are commonly used as they offer several advantages 25 over Portland cement, notably a lower heat of hydration.…”

Section: Introduction 22mentioning

confidence: 99%

Mass transport properties of mature wasteform grouts

Wong

Buenfeld²,

Hill³

et al. 2007

Advances in Cement Research

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6Release of gases from intermediate level radioactive wastes encapsulated in cement-based wasteform grouts is a 7 major concern during the interim storage, transportation and operational stage of a phased geological repository 8 system. The ability of the wasteform grout to retain radioactive gases depends on its mass transport properties, 9 which evolve with age, water saturation degree and any degradation. This paper reports the gas diffusion, gas 10 permeation and water absorption (sorptivity) coefficients of two mature wasteform grouts containing 75% pul-11 verised fuel ash or 75% blast furnace slag. Some of the slag grouts were found to be affected by microcracking, 12 and these were subsequently examined using backscattered electron microscopy and quantified using a specifi-13 cally developed image analysis procedure. Prior to transport testing, samples were conditioned in a realistic 14 manner to a range of water saturation levels (10-100%). The mass transport properties were found to be highly 15 dependent on the degree of water saturation, in particular for samples conditioned at relative humidity greater 16 than 55%. The microcracks have a significant effect on permeability, but less influence on diffusion and water 17 absorption. Implications of the results on the effectiveness of these grouts for radioactive waste containment are 18 presented.

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The role of engineered barriers in a UK repository for intermediate level radioactive waste

Cited by 6 publications

References 0 publications

A long-term experimental study of the reactivity of basement rock with highly alkaline cement waters: Reactions over the first 15 months

A long-term experimental study of the reactivity of basement rock with highly alkaline cement waters: Reactions over the first 15 months

Solution Speciation of Plutonium and Americium at an Australian Legacy Radioactive Waste Disposal Site

Mass transport properties of mature wasteform grouts

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