Development of Borosilicate Glass Compositions for the Immobilisation of the UK's Separated Plutonium Stocks

2008 ◽  
Vol 1107 ◽  
Author(s):  
Mike T. Harrison ◽  
Charlie R. Scales

AbstractThe UK inventory of separated civil plutonium is expected to exceed 100 tonnes by 2010. Whilst the majority of this could be used in the manufacture of MOx (Mixed Oxide) fuel in future power generation scenarios, options for the disposal of surplus plutonium are currently being investigated by Nexia Solutions Ltd on behalf of the UK's Nuclear Decommissioning Authority (NDA). One of the options being considered is immobilisation in a durable glass matrix followed by long term storage and subsequent final repository disposal.A preliminary experimental survey assessed a selection of potential glass systems on the basis of Pu-surrogate (cerium) loading, durability, and ease of processing. Following this, a number of borosilicate compositions have been taken forward into a more detailed investigation in order to fully qualify their potential for Pu-immobilisation. The selected compositions are lanthanide borosilicate (LaBS), alkali tin silicate (ATS) and high-lanthanide alkali borosilicate (modified-MW). For this second series of experiments, hafnium was selected as the Pu surrogate, and a study of the potential waste loading as a function of temperature for the three selected compositions is described in this paper. Furthermore, several variations of the LaBS composition were fabricated in order to investigate the effect of total lanthanide content on melting temperature. The benchmark of 10 wt% HfO2 incorporation is achievable for all three glasses with temperatures of 1200, 1300 and 1400 °C required for ATS, modified-MW and LaBS respectively.

2008 ◽  
Vol 1107 ◽  
Author(s):  
Mike T. Harrison ◽  
Charlie R. Scales

AbstractSeveral glass compositions are currently under investigation for immobilisation of the separated PuO2 that has been produced as a result of civil nuclear fuel reprocessing in the UK. Whilst a final decision on the fate of what ultimately will be over 100 tonnes of plutonium has yet to be made, all options for the disposition of this material are currently being investigated by Nexia Solutions Ltd on behalf of the Nuclear Decommissioning Authority (NDA).As one of the immobilisation options, vitrification in borosilicate glass could potentially provide a criticality-safe and stable waste form with durability suitable for long term storage and subsequent repository disposal. From an initial experimental survey of potential candidates, three borosilicate compositions were selected for a more detailed study of the waste loading and chemical durability: lanthanide borosilicate (LaBS), alkali tin silicate (ATS) and high-lanthanide alkali borosilicate (modified-MW). In these inactive tests, hafnium was used as the surrogate for plutonium. This paper describes a range of static leach tests that were undertaken in order to understand the overall durability of the waste forms, as well as the release rates of the Pusurrogate when compared to any neutrons poisons present in the glass. For the LaBS compositions it was found that the release rate of gadolinium was potentially slightly higher than that of hafnium, although both were as low as 10-5 to 10-6 g m2 day-1. The potential implications for long-term repository behaviour are discussed.


Author(s):  
A. V. Chambers ◽  
W. R. Rodwell ◽  
M. Kelly ◽  
A. R. Hoch ◽  
A. J. Baker

In the UK, the need for the long-term management of intermediate-level radioactive wastes arises from the absence of an established deep disposal option. As a consequence there is a requirement to demonstrate the ‘passive safety’ of waste packages in stores over a necessarily lengthy period (perhaps 150 years or more). ‘Passive safety’ is taken here to imply that the waste packages themselves would remain safe without intervention; it is assumed however, that the store building and associated infrastructure would need to be actively maintained and that the store may need to be ventilated. Importantly, methods for waste storage also need to ensure that possible future options for disposal are not foreclosed. An extended period of storage suggests that emphasis will need to be placed by waste producers on understanding a number of issues such as: • the impact of corrosion on container integrity; • the assessment of container vents and other features as a pathway for the release of radioactivity; • the extent to which wastes are conditioned for storage and the selection of appropriate methods; • the generation and behaviour of toxic or flammable gases in the storage facility; and the mitigating steps that might be needed to address adverse impacts (e.g. the type of ventilation that the store requires). In this paper, we review the requirements and current state of knowledge relevant to the assessment of operational releases of radioactive, flammable and toxic gases from wastes in long-term interim storage.


Author(s):  
David Broughton

UKAEA’s mission at its Dounreay establishment in the north of Scotland is to restore the site so that it can be used for other purposes, with a minimal effect on the environment and requiring minimal attention by future generations. A Dounreay Site Restoration Plan (DSRP) has been produced. It sets out the decommissioning and radioactive waste management activities to restore the site within the next 60 years. Management of solid low level radioactive waste (LLW) that already exists, and that which will be produced as the DSRP progresses is an essential site restoration activity. Altogether around 150,000m3 (5.3Mft3) of untreated LLW could arise. This will then need to be treated, packaged and managed, the resulting volume being around 200,000m3 (7Mft3). A project to develop a long term strategy for managing all Dounreay’s existing and future LLW was initiated in 1999. The identification of complete solutions for management of LLW arising from the site restoration of Dounreay, an integrated reactor and reprocessing site, is novel in the UK. The full range of LLW will be encountered. UKAEA is progressing this specific project during a period when both responsibility and policy for UK decommissioning and radioactive waste management are evolving in the UK. At present, for most UK nuclear operators, there are no recognised routes for disposing of significant volumes of decommissioning LLW that has either lower or higher radioactivity than the levels set by BNFL for disposal at the UK national LLW disposal site at Drigg. A large project such as this has the potential to affect the environmental and social conditions that prevail in the area where it is implemented. Local society therefore has an interest in a project of this scale and scope, particularly as there could be a number of feasible solutions. UKAEA is progressing the project by following UK established practice of undertaking a Best Practicable Environmental Option (BPEO) study. UKAEA has no preconceptions of the outcome and is diligently not prejudging issues prematurely. The BPEO process draws experts and non-experts alike into the discussions and facilitates a structured analysis of the options. However to permit meaningful debate those options have to be at first generated, and secondly investigated. This has taken UKAEA two and a half years in technical assessment of options at a cost of around £23/4M. The options and issues have been investigated to the depth necessary for comparisons and valid judgements to be made within the context of the BPEO study. Further technical evaluation will be required on those options that eventually emerge as the BPEO. UKAEA corporate strategy for stakeholder participation in BPEO studies is laid out in “Restoring our Environment”, published in October 2002. This was developed by a joint approach between project managers, Corporate Communications, and discussion with the regulators, government departments and Scottish Executive. An Internal Stakeholder Panel was held in March 2003. The Panel was independently facilitated and recorded. Eight Panel members attended who provided a representative cross-section of people working on site. Two External Stakeholder Panels were held in Thurso at the end of May 2003. A Youth Stakeholder Panel was held at which three sixth form students from local High Schools gave their views on the options for managing Dounreay’s LLW. The agenda was arranged to maximise interactive discussion on those options and issues that the young people themselves considered important. The second External Stakeholder Panel was based on the Dounreay Local Liaison Committee. Additional participants were invited in acknowledgement of the wider issues involved. As the use of Drigg is an option two representatives from the Cumbrian local district committee attended. From all the knowledge and information acquired from both the technical and stakeholder programmes UKAEA will build up the objective line of argument that leads to the BPEO emerging. This will be the completion of this first stage of the project and is planned for achievement in March 2004. Once the BPEO has been identified the next stage will be to work up the applications for the authorisations that will be necessary to allow implementation of the BPEO. Any facilities needed will require planning permission from the appropriate planning authority. The planning application could be called in by a Minister of State or a planning inquiry convened. During this next stage attention will be paid to ensure all reports and submissions are consistent and compliant with regulations and possible future legal processes. Stakeholder dialogue will continue throughout this next stage moving on from disussion of options to the actual developments. The objective will be to resolve as many issues stakeholders might raise prior to the submissions of applications and prior to the regulators’ formal consultation procedures. This will allow early attention to those areas of concern. Beyond the submission of applications for authorisations it is unwise to speculate as nuclear decommissioning will be then organised in the UK in a different way. The Nuclear Decommissioning Authority will most probably be in overall control and, particularly for Dounreay, the Scottish Executive may have developed its policy for radioactive waste management in Scotland.


2008 ◽  
Vol 1107 ◽  
Author(s):  
J J Hastings

AbstractGlobally, the nuclear industry has a large number of legacy wastes that are stored in ponds, silos and tanks that are nearing the end of their design lifetime and hence said wastes need processing. In the UK there are significant quantities of radioactive sludge that have arisen from the corrosion of early Magnox fuel cans which have been stored underwater. As part of the present aggressive clean-up programme these materials will be retrieved, separated, processed and immobilised as dry waste forms for long-term storage. It is envisaged that hydraulic retrieval will be used for these ILW sludges resulting in some activity being released from the sludge phase to the process liquors challenging downstream ion exchange effluent treatment plants.In order to understand this challenge, experiments have been conducted on sludge in ILW storage ponds and during sludge transfer operations to study the activity released from said sludges. In particular the solubility, adsorption behaviour of Sr-90 is discussed and how this and other aspects of the sludge chemistry impact upon the ion exchange effluent treatment process. The novel methodologies employed to obtain this data is also discussed.


Author(s):  
Konstantin N. Kulikov ◽  
Rinat A. Nizamutdinov ◽  
Andrey N. Abramov

From 1959 up to 1991 nine civil nuclear powered ships were built in Russia: eight ice-breakers and one lash lighter carrier (cargo ship). At the present time three of them were taking out of service: ice-breaker “Lenin” is decommissioned as a museum and is set for storage in the port of Murmansk, nuclear ice-breakers “Arktika” and “Sibir” are berthing. The ice-breakers carrying radwastes appear to be a possible source of radiation contamination of Murmansk region and Kola Bay because the ship long-term storage afloat has the negative effect on hull’s structures. As the result of this under the auspices of the Federal Targeted Program “Nuclear and Radiation Safety of Russia for 2008 and the period until 2015” the conception and projects of decommissioning of nuclear-powered ships are developed by the State corporation Rosatom with the involvement of companies of United Shipbuilding Corporation. In developing the principal provisions of conception of decommissioning and dismantling of ice-breakers the technical and economic assessment of dismantling options in shiprepairing enterprises of North-West of Russia was performed. The paper contains description of options, research procedure, analysis of options of decommissioning and dismantling of nuclear ice-breakers, taking into account the principle of optimization of potential radioactive effect to personnel, human population and environment. The report’s conclusions contain the recommendations for selection of option for development of nuclear ice-breaker decommissioning and dismantling projects.


2014 ◽  
Vol 281 (1787) ◽  
pp. 20140669 ◽  
Author(s):  
C. N. Trueman ◽  
G. Johnston ◽  
B. O'Hea ◽  
K. M. MacKenzie

Biological transfer of nutrients and materials between linked ecosystems influences global carbon budgets and ecosystem structure and function. Identifying the organisms or functional groups that are responsible for nutrient transfer, and quantifying their influence on ecosystem structure and carbon capture is an essential step for informed management of ecosystems in physically distant, but ecologically linked areas. Here, we combine natural abundance stable isotope tracers and survey data to show that mid-water and bentho-pelagic-feeding demersal fishes play an important role in the ocean carbon cycle, bypassing the detrital particle flux and transferring carbon to deep long-term storage. Global peaks in biomass and diversity of fishes at mid-slope depths are explained by competitive release of the demersal fish predators of mid-water organisms, which in turn support benthic fish production. Over 50% of the biomass of the demersal fish community at depths between 500 and 1800 m is supported by biological rather than detrital nutrient flux processes, and we estimate that bentho-pelagic fishes from the UK–Irish continental slope capture and store a volume of carbon equivalent to over 1 million tonnes of CO 2 every year.


Author(s):  
Marcella Corocoran ◽  
Martin A. Hamilton ◽  
Colin Clubbe

The UK Overseas Territories (UKOTs) Programme based at the Royal Botanic Garden, Kew (RBG, Kew) has an active training and seed collection programme with local partners in most of the UK’s 16 Overseas Territories. Seeds are banked at the Millennium Seed Bank (MSB) for long-term storage, with a particular focus on endemic and threatened species, contributing to Target 8 of the Global Strategy for Plant Conservation (GSPC). Many of these threatened species have never been in cultivation so horticulture protocols are being developed for each species. Drawing on examples of threatened species from parts of the Caribbean and the Falkland Islands, this paper describes the components of horticulture protocols, from collection through to germination and growth in the first year. It outlines their role and value in the conservation of threatened species. These written protocols together with a short nursery guide are shared with local partners, thereby contributing to Target 3 of the GSPC.


2004 ◽  
Vol 9 (2) ◽  
pp. 85-94 ◽  
Author(s):  
Huangpin Ben Hsieh ◽  
John Fitch ◽  
Dave White ◽  
Frank Torres ◽  
Joy Roy ◽  
...  

The authors have constructed an array of 12 piezoelectric ejectors for printing biological materials. A single-ejector footprint is 8 mm in diameter, standing 4 mm high with 2 reservoirs totaling 76 µL. These ejectors have been tested by dispensing various fluids in several environmental conditions. Reliable drop ejection can be expected in both humidity-controlled and ambient environments over extended periods of time and in hot and cold room temperatures. In a prototype system, 12 ejectors are arranged in a rack, together with an X - Y stage, to allow printing any pattern desired. Printed arrays of features are created with a biological solution containing bovine serum albumin conjugated oligonucleotides, dye, and salty buffer. This ejector system is designed for the ultra-high-throughput generation of arrays on a variety of surfaces. These single or racked ejectors could be used as long-term storage vessels for materials such as small molecules, nucleic acids, proteins, or cell libraries, which would allow for efficient preprogrammed selection of individual clones and greatly reduce the chance of cross-contamination and loss due to transfer. A new generation of design ideas includes plastic injection molded ejectors that are inexpensive and disposable and handheld personal pipettes for liquid transfer in the nanoliter regime. ( Journal of Biomolecular Screening 2004:85-94)


Author(s):  
Elizabeth Robertson ◽  
Stuart Galloway

The Scottish Government’s commitment for 100% of electricity consumed in Scotland to be from renewable, zero-carbon sources by 2020 continues to drive change in the energy system alongside European and UK targets. The growth of renewables in Scotland is being seen at many scales including industrial, domestic and community generation. In these latter two cases, a transition from the current ‘top down’ energy distribution system to a newer approach is emerging. The work of this paper will look at a ‘bottom up’ view that sees community led distributed energy at its centre. This paper uses the modelling tool HESA to investigate high penetrations of distributed generation in the Angus Region of Scotland. Installations of distributed generation will follow Thousand Flowers transition pathway trajectory, which sees more than 50% of electricity demand being supplied by distributed generation by 2050. From this, insights around the technological and socio-political feasibility, consequences and implications of high penetrations of distributed generation in the UK energy system are presented. Results demonstrate the influence that system change will have on regional and local emission levels under four separate scenarios. It is shown that the penetration of distributed generation requires supplementary installations of reliable and long-term storage alongside utilisation of transmission and transportation infrastructures to maximise the potential of distributed generation and maximise whole system benefits. Importantly, there must be a level of co-ordination and support to realise a shift to a highly distributed energy future to ensure there is a strong economic case with a reliable policy backing.


2015 ◽  
Vol 83 (1) ◽  
pp. 125-134 ◽  
Author(s):  
Fatemeh Amighi ◽  
Zahra Emam-Djomeh ◽  
Ashkan Madadlou

The proteolytic stage of the digestion process of white cheese curd was optimised to maximise the angiotensin I-converting enzyme (ACE)-inhibitory activity of the final enzyme-modified cheese (EMC) paste. It was found that bioactive peptides generation in EMC paste was of multi-variable dependent nature and could be optimised by targeted selection of specific component variables. Maximum ACE-inhibitory was obtained by proteolysis at 48 °C for 25 h with 1 g Flavourzyme/kg cheese curd. This bioactive EMC paste was subsequently spray-dried. The drying conditions were optimised to obtain a highly soluble powder to warrant quick and complete hydration, with the lowest water activity to maximise long term storage. The higher the inlet drying air temperature, the greater was the solubility of resultant EMC powder. Differential scanning calorimetry analysis revealed that the highest drying air temperature (200 °C) resulted in a lower glass transition temperature for the potentially bioactive EMC powder.


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