scholarly journals The carbon-14 IPT: an integrated approach to geological disposal of UK wastes containing carbon-14

2015 ◽  
Vol 79 (6) ◽  
pp. 1641-1650 ◽  
Author(s):  
David Lever ◽  
Sarah Vines
Keyword(s):  
Holistic Approach ◽  
Integrated Approach ◽  
Geological Environment ◽  
Geological Disposal ◽  
Carbon 14 ◽  
Disposal Facility ◽  
Working Together ◽  
Integrated Project ◽  
Engineered Barriers ◽  
Design Options

AbstractCarbon-14 is a key radionuclide in the assessment of the safety of a geological disposal facility because of the calculated assessment of the radiological consequences of gaseous carbon-14-bearing species. Radioactive Waste Management Limited has established an Integrated Project Team (IPT) in which partners are working together to develop an holistic approach to carbon-14 management in the disposal system. We have used an 'AND' approach to structure and prioritize our technical work. For a waste stream to be of concern, there has to be a significant inventory, AND carbon-14-bearing gas has to be generated, AND this gas has to be entrained by bulk gas, AND it has to migrate through the engineered barriers, AND it has to migrate through the overlying geological environment (either as gas or in solution), AND there have to be consequences in the biosphere. We are also using this approach to consider alternative treatment, packaging and design options.

Design Options for the UK’s ILW Geological Disposal Facility

2009 ◽  
Author(s):  
Tim Hicks ◽  
Matt White ◽  
Tamara Baldwin ◽  
Neil Chapman ◽  
Fiona Neall ◽  
...  
Keyword(s):  
Public Consultation ◽  
High Level Waste ◽  
Geological Environment ◽  
Spent Fuel ◽  
Geological Disposal ◽  
Disposal Facility ◽  
Wide Range ◽  
The Uk ◽  
High Level ◽  
Design Options

Over the last few years, a major national programme of public consultation has been under way in the UK resulting, in 2006, in the announcement by government of geological disposal as the most appropriate solution for the long-term management of the UK’s long-lived and higher-activity radioactive waste and the launch, in 2008, of an implementation programme. The approach being pursued is to solicit volunteer communities to host a geological disposal facility, which may contain not only intermediate-level waste (ILW) and some low-level waste (LLW), but also high-level waste (HLW), any spent fuel (SF) declared as waste, and potentially other materials that may be declared as waste. These wastes have different physical, chemical, thermal and radiological characteristics, and different concepts will be required to accommodate their disposal, potentially in a single facility. The volunteer approach means that the geological environment that might eventually emerge as the preferred location is not known at the outset. Indeed, the siting process may require evaluation of several different geological environments because the UK has rich geological variability for such a small landmass. Consequently, the Nuclear Decommissioning Authority (NDA), which is charged with designing, developing and implementing a geological disposal facility, has investigated facility designs that could be appropriate for a wide range of host rocks and geological environments. This paper presents the results of a project carried out on behalf of the NDA to collate and report information on concepts for the geological disposal of ILW/LLW; a separate project carried out a parallel evaluation of options for disposing of HLW and SF. Initially, the range of geological disposal facility design options available worldwide for the disposal of ILW/LLW was evaluated. Nine disposal concepts were identified and reviewed that would cater for any geological environment likely to arise in the UK. These concepts have different engineering and operational aspects. The appropriateness of each option for implementation in five different generic geological environments was assessed using expert judgement, with input from the NDA, consultants and the UK regulatory agencies. The paper presents a set of generic designs derived from the study and discusses the key issues that would need to be addressed should any of these designs be considered for implementation in specific geological environments in the UK. The findings of this work are intended to provide a resource to support comparisons of alternative disposal concepts and the identification of designs suitable for the disposal of UK ILW/LLW in different geological environments.

scholarly journals Multiple roles of clays in radioactive waste confinement – introduction

2019 ◽  
Vol 482 (1) ◽  
pp. 1-9
Author(s):  
Simon Norris
Keyword(s):  
Radioactive Waste ◽  
Integrated Approach ◽  
Multiple Roles ◽  
Chemical Contaminants ◽  
Geological Disposal ◽  
Clayey Material ◽  
Engineered Barriers ◽  
Host Rocks ◽  
Term Management

AbstractGeological disposal provides the safe long-term management solution for higher-activity radioactive waste. The development of a repository (or geological disposal facility) requires a systematic and integrated approach, taking into account the characteristics of the waste to be emplaced, the enclosing engineered barriers, and the host rock and its geological setting.Clays and clayey material are important in the development of many national geological disposal systems. Clays exhibit many interesting properties, and are proposed both as host rocks and as material for engineered barriers. Whatever their use, clays present various characteristics that make them high-quality barriers to the migration of radionuclides and chemical contaminants. As host rocks, clays are, in addition, hydrogeologically, geochemically and mechanically stable over geological timescales (i.e. millions of years).

An Integrated Approach to Geological Disposal of UK Wastes Containing Carbon-14

2013 ◽  
Author(s):  
Sarah Vines ◽  
David Lever
Keyword(s):  
Radioactive Waste ◽  
Gas Phase ◽  
Alternative Treatment ◽  
Phase 1 ◽  
Project Team ◽  
Waste Stream ◽  
Second Phase ◽  
Geological Disposal ◽  
Carbon 14 ◽  
Design Options

Carbon-14 is a key radionuclide in the assessment of the safety of a geological disposal facility for radioactive waste because of the calculated assessment of the radiological consequences of gaseous carbon-14 bearing species [i]. It may be that such calculations are based on overly conservative assumptions and that better understanding could lead to considerably reduced assessment of the radiological consequences from these wastes. Alternatively, it may be possible to mitigate the impact of these wastes through alternative treatment, packaging or design options. The Radioactive Waste Management Directorate of the UK’s Nuclear Decommissioning Authority (NDA RWMD) has established an integrated project team in which the partners are working together to develop a holistic approach to carbon-14 management in the disposal system [ii]. For a waste stream containing carbon-14 to be an issue: • There must be a significant inventory of carbon-14 in the waste stream; AND • That waste stream has to generate carbon-14 bearing gas; AND • A bulk gas phase has to entrain the carbon-14 bearing gas: AND • These gases must migrate through the engineered barriers in significant quantities; AND • These gases must migrate through the overlying geological environment (either as a distinct gas phase or as dissolved gas); AND • These gases must interact with materials in the biosphere (i.e. plants) in a manner that leads to significant doses and risks to exposed groups or potentially exposed groups. The project team has developed and used this “AND” approach to structure and prioritise the technical work and break the problem down in a manageable way. We have also used it to develop our approach to considering alternative treatment, packaging and design options. For example, it may be possible to pre-treat some wastes to remove some of the inventory or to segregate other wastes so that they are removed from any bulk gas phase which might facilitate migration through the geosphere. Initially, the project team has undertaken a six month programme of work to examine the current understanding of these aspects and has captured this in the Phase 1 report [ii], in a modelling basis spreadsheet and in scoping assessments, which help us better understand the potential significance of carbon-14. Using the current modelling basis, but ignoring any potential benefits from the geosphere in retarding or preventing gas from reaching the surface, the calculated release of carbon-14 is dominated by: corrosion of irradiated reactive metals (in the operational and early post-closure time frame); corrosion of irradiated stainless steel and leaching of irradiated graphite (in the longer term). The Phase 1 work has shown that there is considerable scope for reducing the calculated radiological consequence for these wastes and a roadmap has been developed for a second Phase of work.

scholarly journals Development of a MEMS Sensor System for In-Situ Monitoring of the Engineered Barrier in a Geological Disposal Facility

2017 ◽  
Author(s):  
Wenbin Yang ◽  
Rebecca J Lunn ◽  
Alessandro Tarantino ◽  
Gráinne El Mountassir
Keyword(s):  
Relative Humidity ◽  
Radioactive Waste ◽  
Swelling Pressure ◽  
Geological Disposal ◽  
Sensing System ◽  
Mems Sensor ◽  
Polyurethane Resin ◽  
Disposal Facility ◽  
Engineered Barriers

Geological disposal facilities for radioactive waste pose significant challenges for robust monitoring of environmental conditions within the engineered barriers that surround the waste canister. Temperatures are elevated, due to the presence of heat generating waste, relative humidity varies from 20% to 100%, and swelling pressures within the bentonite barrier can typically be 2-10 MPa. Here, we test the robustness of a bespoke design MEMS sensor-based monitoring system, which we encapsulate in polyurethane resin. We place the sensor within an oedometer cell and show that despite a rise in swelling pressure to 2 MPa, our relative humidity (RH) measurements are unaffected. We then test the sensing system against a traditional RH sensor, using saturated bentonite with a range of RH values between 50% and 100%. Measurements differ, on average, by 2.87% RH, and a particularly far apart for high values of RH. However, bespoke calibration of the MEMS sensing system using saturated solutions of known RH, reduces the measurement difference to an average of 1.97% RH, greatly increasing the accuracy for RH values close to 100%.

scholarly journals An approach to modelling the impact of 14C release from reactor graphite in a geological disposal facility

2015 ◽  
Vol 79 (6) ◽  
pp. 1495-1503 ◽  
Author(s):  
Charalampos Doulgeris ◽  
Paul Humphreys ◽  
Simon Rout
Keyword(s):  
Near Field ◽  
Significant Proportion ◽  
Reactor Core ◽  
Microbial Reduction ◽  
Gaseous Species ◽  
Geological Disposal ◽  
Carbon 14 ◽  
Reactor Graphite ◽  
Disposal Facility ◽  
The Impact

AbstractCarbon-14 (C-14) is a key radionuclide in the assessment of a geological disposal facility (GDF) for radioactive waste. In the UK a significant proportion of the national C-14 inventory is associated with reactor-core graphite generated by the decommissioning of the UK's Magnox and AGR reactors.There are a number of uncertainties associated with the fate and transport of C-14 in a post-closure disposal environment that need to be considered when calculating the radiological impacts of C-14-containing wastes. Some of these uncertainties are associated with the distribution of C-14-containing gaseous species such as 14CH4 and 14CO2 between the groundwater and gaseous release pathways. As part of the C14-BIG programme, a modelling framework has been developed to investigate these uncertainties. This framework consists of a biogeochemical near-field evolution model, incorporating a graphite carbon-14 release model, which interfaces with a geosphere/biosphere model. The model highlights the potential impact of the microbial reduction of 14CO2 to 14CH4, through the oxidation of H2, on C-14 transport. The modelling results could be used to inform the possible segregation of reactor graphite from other gasgenerating wastes.

Integrated Approach to Modeling Long-Term Durability of Concrete Engineered Barriers in Llrw Disposal Facility

1994 ◽  
Vol 353 ◽  
Author(s):  
J. H. Lee ◽  
D. M. Roy ◽  
B. Mann ◽  
D. Stahl
Keyword(s):  
Pore Solution ◽  
Model Development ◽  
Integrated Approach ◽  
Alkaline Condition ◽  
Near Surface ◽  
Disposal Facility ◽  
Engineered Barriers ◽  
Development Approach ◽  
Concrete Barrier

AbstractThis paper describes an integrated approach to developing a predictive computer model for long-term performance of concrete engineered barriers utilized in LLRW and ILRW disposal facilities. The model development concept consists of three major modeling schemes: hydration modeling of the binder phase, pore solution speciation, and transport modeling in the concrete barrier and service environment. Although still in its inception, the model development approach demonstrated that the chemical and physical properties of complex cementitious materials and their interactions with service environments can be described quantitatively.Applying the integrated model development approach to modeling alkali (Na and K) leaching from a concrete pad barrier in an above-grade tumulus disposal unit, it is predicted that, in a near-surface land disposal facility where water infiltration through the facility is normally minimal, the alkalis control the pore solution pH of the concrete barriers for much longer than most previous concrete barrier degradation studies assumed. The results also imply that a highly alkaline condition created by the alkali leaching will result in alteration of the soil mineralogy in the vicinity of the disposal facility.

An overview of near-field evolution research in support of the UK geological disposal programme

2012 ◽  
Vol 76 (8) ◽  
pp. 2995-3001 ◽  
Author(s):  
T. M. Beattie ◽  
S. J. Williams
Keyword(s):  
Radioactive Waste ◽  
Host Rock ◽  
Near Field ◽  
Radioactive Decay ◽  
Geological Disposal ◽  
Nuclear Decommissioning ◽  
Disposal Facility ◽  
Engineered Barriers ◽  
The Uk

AbstractThe near field, together with the containment and isolation provided by the geosphere, contributes to the long-term safety provided by a geological disposal facility (GDF) after closure. The different engineered barriers can prevent or limit the release of radionuclides and their migration to the undisturbed host rock or geosphere and are expected to fulfil their post-closure safety functions for many thousands to hundreds of thousands of years. They will continue to contribute to containment after their eventual degradation when there would no longer be confidence that they would continue to fulfil all of their safety functions in their totality. By that time, significant radioactive decay will have occurred, substantially reducing the hazard associated with the wastes. Therefore, demonstration of long-term safety requires an understanding of the evolution of the engineered barriers and the consequences for the generic safety functions that the different barriers provide. This paper provides an overview of the research of the Nuclear Decommissioning Authority Radioactive Waste Management Directorate into the evolution of the near field of a GDF.

scholarly journals Laboratory Testing of a MEMS Sensor System for In-Situ Monitoring of the Engineered Barrier in a Geological Disposal Facility

2017 ◽  
Author(s):  
Wenbin Yang ◽  
Rebecca J. Lunn ◽  
Alessandro Tarantino ◽  
Gráinne El Mountassir
Keyword(s):  
Relative Humidity ◽  
Swelling Pressure ◽  
In Situ Monitoring ◽  
Geological Disposal ◽  
Sensing System ◽  
Mems Sensor ◽  
Polyurethane Resin ◽  
Disposal Facility ◽  
Engineered Barriers

Geological disposal facilities for radioactive waste pose significant challenges for robust monitoring of environmental conditions within the engineered barriers that surround the waste canister. Temperatures are elevated, due to the presence of heat generating waste, relative humidity varies from 20% to 100%, and swelling pressures within the bentonite barrier can typically be 2-10 MPa. Here, we test the robustness of a bespoke design MEMS sensor-based monitoring system, which we encapsulate in polyurethane resin. We place the sensor within an oedometer cell and show that despite a rise in swelling pressure to 2 MPa, our relative humidity (RH) measurements are unaffected. We then test the sensing system against a traditional RH sensor, using saturated bentonite with a range of RH values between 50% and 100%. Measurements differ, on average, by 2.87% RH, and are particularly far apart for values of RH greater than 98%. However, bespoke calibration of the MEMS sensing system using saturated solutions of known RH, reduces the measurement difference to an average of 1.97% RH, greatly increasing the accuracy for RH values close to 100%.

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