The Post-Disposal Behaviour of C-14 and Irradiated Graphite
Lead Research Organisation:
University of Huddersfield
Department Name: Sch of Applied Sciences
Abstract
Graphite is a key waste form arising from the decommissioning of nuclear reactors such as the UK's Magnox and AGR nuclear power stations. This graphite contains a range of radioactive contaminants generated during its time in the reactor core. The safe disposal of this graphite is dependent on an understanding of how these contaminants behave in a disposal site. One of the most important contaminant associated with reactor graphite is carbon-14, a radioactive variant of the carbon naturally found in the environment. Carbon-14 is important from a risk point of view since it persists in the environment and can become incorporated into food through interaction with plants of microorganisms. Graphite arising from the decommissioning of nuclear reactors is currently destined for deep geological disposal, which involves burying deep underground which is very expensive. The aim of this project is to get a better understanding of how carbon-14 is incorporated into graphite, how it will be released from graphite under deep geological conditions and how the chemistry and microbiology of carbon-14 influence its transport out of a disposal site and its ultimate contact with people. It is hoped that this improved understanding may result in some graphite being disposed of safely to near-surface facilities and that more realistic estimates of the risks associated with graphite disposal can be made.
Planned Impact
The proposed project represents a step change in current understanding of the technical basis of UK reactor graphite disposal and the disposal of other carbon-14 related waste streams. The empirical data generated will be available for incorporation into carbon-14 gas generation and contaminant transport models employed for dose and risk evaluation. The project will provide (i) a baseline understanding for the distribution of carbon-14 in irradiated reactor graphite and (ii) will subsequently make use of experiments that simulate graphite mobilisation (including carbon-14 partitioning between gas, liquid and solid phases) in post-closure disposal environments and (iii) provide modelling tools to enable the near-field simulation of carbon-14 behaviour and gaseous and aqueous source terms for biosphere assessments. It is anticipated that the knowledge arising from this project would be of direct use to the nuclear industry with specific relevance to the Nuclear Decommissioning Authority (NDA), the EA (SEPA), the operators of Magnox reactor sites, EDF Ltd and operators of the LLWR. The project will also be of interest to the scientific consultancy community who serve the nuclear industry through both experimental and modelling activities. It is also anticipated that this project will directly link with associated work across Europe.
Publications
Charles C
(2022)
The evolution of alkaliphilic biofilm communities in response to extreme alkaline pH values
in MicrobiologyOpen
Doulgeris C
(2018)
An approach to modelling the impact of 14 C release from reactor graphite in a geological disposal facility
in Mineralogical Magazine
Rout SP
(2018)
The Impact of Alkaliphilic Biofilm Formation on the Release and Retention of Carbon Isotopes from Nuclear Reactor Graphite.
in Scientific reports
Payne L
(2018)
Evaluation of the use of magnetic sector secondary ion mass spectrometry to investigate 14 C distribution in Magnox reactor core graphite
in Mineralogical Magazine
Charles CJ
(2017)
Floc Formation Reduces the pH Stress Experienced by Microorganisms Living in Alkaline Environments.
in Applied and environmental microbiology
Rout SP
(2015)
Draft Genome Sequence of Alkaliphilic Exiguobacterium sp. Strain HUD, Isolated from a Polymicrobial Consortia.
in Genome announcements
Rout SP
(2015)
Anoxic Biodegradation of Isosaccharinic Acids at Alkaline pH by Natural Microbial Communities.
in PloS one
| Description | The key findings of the project are: 1. Analysis of 49 reactor graphite samples indicated that graphite exposed to fuel channels had a distinct surface deposit micrometers thick (See publications). This surface deposit was enriched in C-14, with a higher concentration measured on samples originating lower in the fuel channels. The remaining C-14 was split between a surface/near sub-surface fraction originating from nitrogen surface complexes, that may be released slowly in a geological disposal facility (GDF), and a second fraction from nitrogen and C-13 precursors located in the graphite lattice that may never be released. 2. A non-radioactive simulant of the surface deposits described above was established using C-12 and C-13 compounds. These simulants have undergone extensive analysis and comparison with actual reactor graphite deposits. This methodology consistently generated a simulant that compared favourably with the actually deposits and which provided an insight into the conditions required for deposit development (See publications). This is important since the surface deposit seen in the reactors is enriched in C-14 and therefore an understanding of its development may assist the decommissioning of these reactors and inform how reactor graphite may behave once disposed of in a GDF. 3. In order to investigate the behavior of C-14 in a GDF microbial microcosms were established under conditions anticipated to occur within such a facility. These were established from both neutral and alkaline environments, maintained under anaerobic conditions and fed on cellulose degradation products which contained Iso-saccharinic acids (ISA). These microcosms degraded ISA and generated methane, a key process in the release of C-14, up to pH 11.0 (See publications). However, when either simulated reactor graphite or actual reactor graphite was incubated in these microcosms there was no evidence of enhanced C-14 release due to microbial activity. In fact, biofilms formed on the graphite surfaces and microbial mediated calcite precipitation occurred over the surface deposits. These results indicate that microbial activity may not directly impact on the release of C-14 from reactor graphite as has previously been thought and in fact biofilm formation may actually modify C-14 release. 4. A mathematical model was developed (See publications) which integrated current understanding of C-14 release from graphite, with a biogeochemical model able to simulate the microbial processes observed in the microcosms described above. The model included a geosphere model that simulates both aqueous and gaseous releases of C-14 to the environment. Given that the microcosm studies indicated that there was no direct connection between microbial activity and C-14 release the model focused on the indirect impacts associated with the formation/degradation of gases such as hydrogen and methane. It has been suggested that the formation of these gases may entrain C-14 gases and accelerate their transport out of a GDF. This modelling work identified the role of microbial hydrogen consumption as a key controlling factor on C-14 release since it reduces the overall amount of gas generated in a GDF. The microbiology of this process is the subject of follow on research funded by RWM Ltd. |
| Exploitation Route | Information regarding the nature and partitioning of C-14 within Magnox reactor graphite provided by the project provides an insight into the evolution of reactor graphite which can inform other researchers since this project has significantly increased the number of actual samples that have been characterized. Understanding how C-14 is partitioned within graphite will also help to reconcile observational studies on C-14 release from graphite with the physical nature of the materials. This will have implications for modelling studies using C-14 release data and may inform discussions regarding reactor decommissioning and the segregation of wastes in a GDF. The C-13 simulant developed during the project may be used by other researchers wishing to study C-14 and reactor graphite without the need to use actual radioactive materials, significantly reducing the costs and risks associated with reactor graphite research. The microbiological component of the project extended our understanding of the upper pH range for methane generation and provided the first degradation rates for ISAs under strictly anaerobic conditions. These observations regarding methane generation and the reaction rates can both be used in modelling studies on gas generation within GDFs. As such this data is useful for radioactive waste management organisations both within UK and worldwide. |
| Sectors | Energy,Environment,Other |
| URL | http://www.hud.ac.uk/c14-big/ |
| Description | The finding feed into the evaluation of C-14 releases from radioactive wastes and associated disposals. |
| First Year Of Impact | 2017 |
| Sector | Education,Energy,Environment,Other |
| Impact Types | Economic,Policy & public services |
| Description | Industrial Phd Funding |
| Amount | £80,000 (GBP) |
| Organisation | Nuclear Decommissioning Authority NDA |
| Sector | Public |
| Country | United Kingdom |
| Start | 09/2015 |
| End | 03/2018 |
| Description | Resource Recovery and Remediation |
| Amount | £10,000 (GBP) |
| Funding ID | NE/L014211/1 |
| Organisation | Natural Environment Research Council |
| Sector | Public |
| Country | United Kingdom |
| Start | 08/2014 |
| End | 07/2016 |
| Description | Bristol/Kyoto Collaboration |
| Organisation | University of Bristol |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | The C-14 Big project has led to a collaboration between the Interface Analysis Center at the University of Bristol and KURRI (Kyoto University). |
| Collaborator Contribution | This collaboration has led to KURRI submitting a request for funding for a secondment of Drs Scott and Payne to work with them for several months in Japan. The decision is still pending on this submission. |
| Impact | Too early to specify specific outputs, at the moment the project contribution is at a relationship building stage. . |
| Start Year | 2015 |
| Description | C-14 Ridge |
| Organisation | University of Bristol |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | The C-14 RIDGE - Reprocessing of IrraDiated Graphite for Extraction of 14C proposal was developed between the Universitiy of Bristol, UCLan and a Korean university. This was in response to a EPSRC - Korean initiative. This bid was unsuccessful but is being rewritten for future re-submission. |
| Collaborator Contribution | The proposal was developed by team members at Universitiy of Bristol and UCLan. |
| Impact | This collaboration was successful in building relationships between the C-14 Big team and the Korean University sector. |
| Start Year | 2014 |
| Description | C-14 Ridge |
| Organisation | University of Central Lancashire |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | The C-14 RIDGE - Reprocessing of IrraDiated Graphite for Extraction of 14C proposal was developed between the Universitiy of Bristol, UCLan and a Korean university. This was in response to a EPSRC - Korean initiative. This bid was unsuccessful but is being rewritten for future re-submission. |
| Collaborator Contribution | The proposal was developed by team members at Universitiy of Bristol and UCLan. |
| Impact | This collaboration was successful in building relationships between the C-14 Big team and the Korean University sector. |
| Start Year | 2014 |
| Description | Environmental Organic Analysis |
| Organisation | University of Leeds |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | The organic analytical capabilities at the University of Huddersfield that have been developed during the C14-Big project have been utilized during collaborative research with the University of Leeds. This has involved the analysis of environmental samples for organic marker of microbial activity. |
| Collaborator Contribution | The University of Leeds Team provided environmental samples from a chromium contaminated site, they performed a detailed geochemical analysis of the samples and associated molecular microbiological analysis. |
| Impact | This collaboration led to the following publication: W Ding, D I Stewart, P N Humphreys, S P Rout, I T. Burke (2016) Role of an organic carbon-rich soil and Fe(III) reduction in reducing the toxicity and environmental mobility of Chromium(VI) at a COPR disposal site. Science of the Total Environment, 541: 1191-1199. |
| Start Year | 2013 |
| Description | Molecular Biology Research |
| Organisation | University of Liverpool |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | The microcosms established as part of the C14-BIG project have been the basis of a molecular biology collaboration with the Environmental Microbiology group at Liverpool University. Training and advice in the molecular characterization of microbial communities was provided. The contribution made by the University of Huddersfield was the establishment of long term the alkaliphilic microbial microcosms which were then used for C-14 and molecular microbiology investigations. |
| Collaborator Contribution | The Environmental Microbiology Group provided training on modern molecular techniques for the investigation of microbial populations. They also provided advice on analytical techniques, method development, equipment and sequencing services. |
| Impact | This partnership contributed to the following outputs: 1. C J Charles, S P Rout, E J Garratt, K Patel, A P Laws, P N Humphreys (2015) DOI:10.1093/femsec/fiv085 2. S P Rout, C J Charles, C Doulgeris, A J McCarthy, D J Rooks, P Loughnane, A P Laws, P N Humphreys (2015) DOI:10.1371/journal.pone.0137682 3. S P Rout, C J Charles, E J Garratt, A P Laws, J Gunn (2015) DOI:10.1371/journal.pone.0119164 |
| Start Year | 2012 |
| Title | Goldsim biosphere model of C-14 transport |
| Description | A model of C-14 transport through the geosphere was developed in the Goldsim simulation package. The resulting model was passed over to the modelling team of RWM Ltd in order to facilitate a technical discussion and knowledge transfer. |
| Type Of Technology | Software |
| Year Produced | 2014 |
| Impact | The model integrates groundwater and gaseous transport of C-14 species in a manner that allows these processes to be integrated into an environmental safety case. |
| Description | Effect of pH on the microbial degradation |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Participants in your research and patient groups |
| Results and Impact | The poster presentation generated considerable discussion about the work presented and techniques employed with delegates attending the conference. A request to submit a paper to the SGM journal was received. |
| Year(s) Of Engagement Activity | 2014 |
| Description | Effect of pH on the microbial degradation of anaerobic alkaline cellulose degradation products relevant to geological disposal |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | Yes |
| Geographic Reach | International |
| Primary Audience | Participants in your research and patient groups |
| Results and Impact | The presentation advertised the project progress and the capabilities of the team to an international audience of scientists and policy makers. There was considerable interest in the data and approaches employed in the research presented. |
| Year(s) Of Engagement Activity | 2014 |
| Description | Modelling the impact of 14C release from graphite in geological disposal |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | Yes |
| Geographic Reach | International |
| Primary Audience | Participants in your research and patient groups |
| Results and Impact | The presentation generated considerable discussion regarding the modelling of the impacts of C-14 releases from radioactive waste disposal sites. Generated discussion with international experts on C-14 modelling. |
| Year(s) Of Engagement Activity | 2014 |
| Description | Participated in the "Is Nuclear Green?" public engagement event which was part of the Bristol harbour festival (17th-19th July 2015) |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Public/other audiences |
| Results and Impact | The event allowed issues surrounding nuclear energy and the disposal of radioactive waste to be discussed in layman's terms with a wide audience from young children, through secondary and further education students and up to adults, with the range of knowledge varying from those who had little knowledge of the subject to those who had worked in the industry. Overall the event was a success with a large number of the public visiting the exhibition and engaging with members of the team, with the hope that through this some of them learnt the merits of nuclear energy, understand the challenges associated with it and how these are being addressed in the UK. The event served as a catalyst for discussion and awareness raising in members of the general public in the issues surroundings nuclear energy and the disposal of radioactive waste. It also allowed members of the general public to meet and interact directly with scientists and students working in the nuclear arena, an interaction which helped to dispel some of the negative preconceptions regarding the people working in this industry. |
| Year(s) Of Engagement Activity | 2015 |
| Description | Proposal for in-situ measurements of graphite moderated reactor cores to determine concentration and distribution of 14C |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Participants in your research and patient groups |
| Results and Impact | This poster presentation took place at the EPSRC/NDA geowaste meeting held at Loughborough University in July 2013 The poster generated considerable interest in the technology being developed. |
| Year(s) Of Engagement Activity | 2013 |
| Description | The post disposal behaviour of 14C and irradiated graphite |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Participants in your research and patient groups |
| Results and Impact | This was a poster presentation by the UCLAN component of the project at the NDA RWMD - EPSRC Geowaste Meeting, held at Loughborough University, 9th - 11th July 2013. This presentation disseminated the approach developed to generate C-13 based simulants for C-14 present in reactor graphite. |
| Year(s) Of Engagement Activity | 2013 |
| Description | The use of Magnetic Sector Secondary Ion Mass Spectrometry to investigate 14C distribution in Magnox reactor core graphite. |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | Yes |
| Geographic Reach | International |
| Primary Audience | Participants in your research and patient groups |
| Results and Impact | This presentation communicated this aspect of the project to scientists and industry representatives from across Europe. A considerable amount of interest was generated in the results, techniques and technology outlined in the poster. |
| Year(s) Of Engagement Activity | 2014 |
| Description | Towards A Low Carbon Kirklees - local responses to climate change |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Public/other audiences |
| Results and Impact | My involvement generated debate around the role of nuclear energy in providing a low carbon future for the UK. It particularly provided a platform for discussion regarding why national strategies were required alongside local initiatives since nuclear new build can only be achieved at a national level. The most notable impact was through challenging old school green thinking i.e. nuclear can not be green, sine the thrust of my argument was the nuclear was able to make a major contribution to a low carbon future. |
| Year(s) Of Engagement Activity | 2015 |