scholarly journals Evaluation of the corrosion behavior of modern spent nuclear fuels under repository conditions

2021 ◽  
Vol 1 ◽  
pp. 91-93
Author(s):  
Philip Kegler ◽  
Martina Klinkenberg ◽  
Felix Brandt ◽  
Guido Deissmann ◽  
Dirk Bosbach
Keyword(s):  
Corrosion Behavior ◽  
Nuclear Power ◽  
Spent Nuclear Fuel ◽  
Dissolution Behavior ◽  
Dissolution Mechanism ◽  
Dissolution Rates ◽  
Geological Disposal ◽  
Grain Sizes ◽  
Deep Geological Disposal ◽  
Significant Change

Abstract. In Germany it is planned to directly dispose spent nuclear fuel (SNF) from nuclear power plants together with other high-level radioactive wastes (HLW) from former SNF reprocessing (e.g., vitrified waste), in a deep geological repository for heat-generating wastes – the siting process for this repository was started in 2017 and is ongoing. Based on several decades of research, development, and demonstration (RD&D) it is generally accepted at the technical and scientific level that direct disposal of HLW and SNF in deep mined geological repositories is the safest and most sustainable option (CEC, 2011; IAEA, 2004). The current efforts to improve the performance and accident tolerance of fuels in nuclear power generation resulted in an increased utilization of a variety of new types of light-water reactor (LWR) fuels such as fuels doped with Cr, Al, and Si. This doping leads to a significant change of the microstructure of the fuel matrix. The corrosion behavior of these types of fuels under conditions relevant to deep geological disposal has hardly been studied so far; however, this is of crucial importance as the development of a robust safety case for deep geological disposal of SNF requires a solid understanding of its dissolution behavior over very long time scales (up to 1 million years). To fill this knowledge gap, additional systematic studies on modern doped UO2 fuels were needed. Corrosion experiments with SNF cannot entirely unravel all of the various concurring effects of the dissolution mechanism due to the chemical and structural complexity of SNF and its high beta and gamma radiation field during the first 1000 years; moreover, technical restrictions only allow a very limited number of experiments. Therefore, within the EU-DisCo project (https://www.disco-h2020.eu, last access: 11 October 2021), a very ambitious programme of corrosion studies on irradiated Cr and Al/Cr doped fuels was carried out, which was complemented by systematic single-effect dissolution studies (e.g., with respect to doping level, grain size and thermodynamic aspects) performed on carefully prepared and characterized, simplified UO2-based model materials. Here, we present recent results on the dissolution behavior of tailor-made UO2 model materials in accelerated static batch experiments using H2O2 as simulant for radiolytic oxidants, present in long-term disposal scenarios for SNF in failed container conditions due to the alpha irradiation of water. In these dissolution experiments pure UO2 reference pellets exhibiting different densities and grain sizes, as well as Cr-doped UO2 pellets with various Cr-doping levels, produced using different doping methods having different grain sizes, were used. In addition, Nd-doped and industrially produced Cr- and Cr/Nd-doped UO2 pellets were used to determine the influence of these parameters on the dissolution rates. The dissolution experiments were performed under strictly controlled conditions with respect to exclusion of oxygen, temperature control, and exclusion of light. This bottom-up approach was followed to understand how the addition of Cr-oxide into the fuel matrix affects SNF dissolution behavior under repository relevant conditions. The results of the dissolution experiments performed with real SNF and the model materials obtained by the DisCo partners build the basis for numerical simulations on the dissolution behavior of modern SNF. First results of the data evaluation indicate that the addition of dopants and the consequential modification of the fuel matrix does not lead to a significant change of the dissolution behavior of these fuels under repository relevant conditions compared to standard SNF (i.e. dissolution rates agree within an order of magnitude).

scholarly journals Assessment of Permian Zubers as the Host Rock for Deep Geological Disposal

Energies ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2239
Author(s):  
Leszek Lankof
Keyword(s):  
Radioactive Waste ◽  
Rock Salt ◽  
Host Rock ◽  
Nuclear Power ◽  
Spent Nuclear Fuel ◽  
Renewable Energy Sources ◽  
Geological Disposal ◽  
Lithostratigraphic Units ◽  
Deep Geological Disposal

Together with renewable energy sources, nuclear power represents an important contribution to a sustainable energy mix in many countries and has an important impact on sustainable development. Nuclear energy production is also a source of high-level radioactive waste (HLW) and spent nuclear fuel (SNF), which require special concern. Disposal in deep geological formations is one of the solutions for the long-term management of HLW and SNF. It requires the development of a concept ensuring long-term safe isolation of waste and its validation applying the safety case methodology, which is a formal compilation of evidence, analyses and arguments that quantify and justify a claim that the repository will be safe. The results of laboratory testing of a potential repository host rock are an important component of the evidence that helps in the safety assessment of the deep geological disposal concept. This paper presents results of research focused on the physical, geomechanical and sorption properties of the Brown and Red Zuber unit rocks from the Kłodawa Salt Mine in Poland, which together with rock salt are an important component of Polish salt domes. The Brown and Red Zubers are typical evaporite lithostratigraphic units for the Polish part of the Zechstein Basin. They consist of halite (15–85%) and water-insoluble minerals, such as anhydrite, clay minerals, carbonates, quartz and feldspar, which occurred in varying proportions in the tested samples. The properties of the zuber rocks have been compared with those of rock salt, which is considered a suitable host rock for deep geological disposal of radioactive waste.

scholarly journals Overview of the Lithuanian programme for disposal of RBMK-1500 spent nuclear fuel

2015 ◽  
Vol 79 (6) ◽  
pp. 1581-1589 ◽  
Author(s):  
Povilas Poskas ◽  
Asta Narkuniene ◽  
Dalia Grigaliuniene
Keyword(s):  
Nuclear Fuel ◽  
Nuclear Power ◽  
Spent Nuclear Fuel ◽  
Lower Triassic ◽  
Current Status ◽  
Large Power ◽  
Geological Disposal ◽  
Deep Geological Disposal ◽  
Clay Formation ◽  
Geological Formations

AbstractIn Lithuania all the spent nuclear fuel (SNF) came from operation of the Ignalina nuclear power plant with two reactors of RBMK type (RBMK is a Russian acronym for 'Channelized Large Power Reactor' which is a water-cooled graphite-moderated reactor: RBMK-1500). Approximately 22,000 SNF assemblies are due for geological disposal in Lithuania. Currently it is envisaged that SNF will be stored in dry interim storage facilities (new and existing) for at least 50 y prior to possible deep geological disposal.The decision on the final SNF management option (disposal in a national repository, disposal in regional repositories, etc.) has not yet been made but some investigations of the possibilities to dispose of the SNF in Lithuania have been initiated. With the support of Swedish experts, analysis of possible geological formations for SNF disposal was performed and the existence of potentially suitable formations agreed. The geological formations prioritized as prospective include the crystalline rocks in southern Lithuania and two clayey formations: the Lower Triassic clay formation and the Lower Cambrian Baltic Group clay formation, with priority given to the Lower Triassic clay formation.This paper presents the main aspects of the research and other activities undertaken over the past decade in the field of SNF disposal: international cooperation; current status and plans for the Lithuanian national program; further investigations required; and competence developments.

Solubility data in radioactive waste disposal

2007 ◽  
Vol 79 (5) ◽  
pp. 875-882 ◽  
Author(s):  
Hans Wanner
Keyword(s):  
Radioactive Waste ◽  
Human Health ◽  
Nuclear Power ◽  
Spent Nuclear Fuel ◽  
Radioactive Waste Disposal ◽  
Potential Hazard ◽  
Reliable Assessment ◽  
Deep Geological Disposal ◽  
Equilibrium Data ◽  
Natural Barriers

Radioactive waste arises mainly from the generation of nuclear power but also from the use of radioactive materials in medicine, industry, and research. It occurs in a variety of forms and may range from slightly to highly radioactive. It is a worldwide consensus that radioactive waste should be disposed of in a permanent way which ensures protection of humans and the environment. This objective may be achieved by isolating radioactive waste in a disposal system which is located, designed, constructed, operated, and closed such that any potential hazard to human health is kept acceptably low, now and in the future.For highly radioactive waste and spent nuclear fuel, which are the waste types representing the highest potential danger to human health, an effective isolation from the biosphere is considered to be achievable by deep geological disposal. Disposal concepts rely on the passive safety functions of a series of engineered and natural barriers. Since total isolation over extended timescales is not possible, radionuclides will eventually be released from the waste matrix and migrate through the engineered and natural barriers. The assessment of their mobility in these environments is essential for the safety demonstration of such a repository. The solubility of many radionuclides is limited and may contribute significantly to retention. Reliable predictions of solubility limitations are therefore important.Predictions of maximum solubilities are always subject to uncertainties. Complete sets of thermodynamic and equilibrium data are required for a reliable assessment of the chemical behavior of the radionuclides. Gaps in the thermodynamic databases may lead to erroneous predictions. Missing data and insufficient knowledge of the solubility-limiting processes increase the uncertainties and require pessimistic assumptions in the safety analysis; however, these are usually not detrimental to safety owing to the robustness of the multi-barrier approach.

scholarly journals Partitioning and transmutation contribution of MYRRHA to an EU strategy for HLW management and main achievements of MYRRHA related FP7 and H2020 projects: MYRTE, MARISA, MAXSIMA, SEARCH, MAX, FREYA, ARCAS

2020 ◽  
Vol 6 ◽  
pp. 33
Author(s):  
Hamid Aït Abderrahim ◽  
Peter Baeten ◽  
Alain Sneyers ◽  
Marc Schyns ◽  
Paul Schuurmans ◽  
...  
Keyword(s):  
Waste Management ◽  
Nuclear Power ◽  
Power Plants ◽  
Fuel Cycle ◽  
Economic Feasibility ◽  
Potential Contribution ◽  
Spent Fuel ◽  
Geological Disposal ◽  
Deep Geological Disposal ◽  
Partitioning And Transmutation

Today, nuclear power produces 11% of the world's electricity. Nuclear power plants produce virtually no greenhouse gases or air pollutants during their operation. Emissions over their entire life cycle are very low. Nuclear energy's potential is essential to achieving a deeply decarbonized energy future in many regions of the world as of today and for decades to come, the main value of nuclear energy lies in its potential contribution to decarbonizing the power sector. Nuclear energy's future role, however, is highly uncertain for several reasons: chiefly, escalating costs and, the persistence of historical challenges such as spent fuel and radioactive waste management. Advanced nuclear fuel recycling technologies can enable full use of natural energy resources while minimizing proliferation concerns as well as the volume and longevity of nuclear waste. Partitioning and Transmutation (P&T) has been pointed out in numerous studies as the strategy that can relax constraints on geological disposal, e.g. by reducing the waste radiotoxicity and the footprint of the underground facility. Therefore, a special effort has been made to investigate the potential role of P&T and the related options for waste management all along the fuel cycle. Transmutation based on critical or sub-critical fast spectrum transmuters should be evaluated in order to assess its technical and economic feasibility and capacity, which could ease deep geological disposal implementation.

Deep Geological Disposal of Spent Nuclear Fuel and High-Level Waste

2015 ◽  
pp. 367-399
Author(s):  
Želimir Veinović ◽  
Biljana Kovačević Zelić ◽  
Dubravko Domitrović
Keyword(s):  
Nuclear Fuel ◽  
Power Plants ◽  
Spent Nuclear Fuel ◽  
High Level Waste ◽  
Modern World ◽  
Geological Disposal ◽  
Long Term Storage ◽  
Deep Geological Disposal ◽  
Safety Cases ◽  
High Level

Management of Spent Nuclear Fuel (SF) and High-Level Waste (HLW) is one of the most important and challenging problems of the modern world. Otherwise a clean, cheap, constant, and secure way to produce electricity, nuclear power plants create large amounts of highly hazardous waste. Repositories—deep Geological Disposal Facilities (GDF)—for these types of waste must prevent radionuclides from reaching the biosphere, for up to 1,000,000 years, migrating from a deep (more than 300m), stable geological environment. At present, there are no operating GDFs for SF and/or HLW, mostly due to the difficult and complex task of preparing safety cases and licensing. The purpose of this chapter is to validate the generic R&D activities in this area and present alternative concepts of Radioactive Waste (RW) management: retrievability, reversibility, regional GDFs, long-term storage, and deep borehole disposal, demonstrating the main engineering tasks in solving the problem of RW management and disposal.

Issues in the Timing of High Level Waste Disposal: An International Perspective

2008 ◽  
Author(s):  
Stan Gordelier ◽  
Pa´l Kova´cs
Keyword(s):  
Radioactive Waste ◽  
Waste Disposal ◽  
Nuclear Power ◽  
Nuclear Industry ◽  
High Level Waste ◽  
Geological Disposal ◽  
The Public ◽  
Deep Geological Disposal ◽  
High Level

The world is facing energy difficulties for the future, in terms of security of supply and climate change issues. Nuclear power is virtually carbon free and it contributes to energy security, being a quasi-domestic source. Whilst it cannot provide a complete answer to these challenges, it is certainly capable of providing a significant component of the answer. However, nuclear power remains controversial. In order to gain public acceptance, it is widely recognised that a number of key issues need to be addressed, amongst which is resolution of the high-level radioactive waste (HLW) (including spent fuel) disposal issue. This is an important issue for all countries with an existing nuclear programme, whether or not it is intended that nuclear power should be phased out or expanded — the waste already exists and must be managed in any event. It is equally important for countries planning a new nuclear power programme where none has previously existed. Since nuclear power was first developed over fifty years ago, HLW arisings have been stored as an interim measure. It is widely believed by experts (though not by many opponents of the nuclear industry, nor by the public) that deep geological disposal, after a reasonable cooling time in interim storage, is technically feasible and constitutes a safe option [1] at an acceptable cost. The total volume of HLW from nuclear reactors is relatively small. A key issue, however, is the time-scale for developing such a final disposal solution. Considerations of security and inter-generational equity suggest that geological disposal should be implemented as soon as possible irrespective of whether or not new arisings are created. The question of managing HLW is not necessarily related to the issue of building new nuclear power stations. However, many opponents argue that there has been insufficient demonstration of the long-term safety of deep geological disposal. The same opponents also argue that there should be a moratorium on building new nuclear power plants (NPPs) until the issue of long-term management of HLW is resolved. These arguments have a powerful influence on public opinion towards both the construction of a waste repository and the building of new NPPs. The intent of this paper (developed from the current OECD NEA study on “Timing of High Level Waste Disposal”) is to identify and discuss some of the factors influencing the timing of the implementation of a HLW disposal strategy and to demonstrate to decision makers how these factors are affecting country strategies, based on current experience. Determining an optimum timescale of HLW disposal may be affected by a wide range of factors. The study examines how social acceptability, technical soundness, environmental responsibility and economic feasibility impact on the timing of HLW disposal and can be balanced in a national radioactive waste management strategy taking the social, political and economic environment into account. There is clear evidence that significant fractions of the public still have serious misconceptions with respect to the issues surrounding nuclear waste. The nuclear industry, together with governments in those countries who would like a component of nuclear power in their energy mix, has a responsibility for and a significant challenge in presenting its case to the public.

Solution Composition Effects on the Dissolution of a CeO2 analogue for UO2 and ThO2 nuclear fuels

2015 ◽  
Vol 1744 ◽  
pp. 185-190 ◽  
Author(s):  
Claire L. Corkhill ◽  
Martin C. Stennett ◽  
Neil C. Hyatt
Keyword(s):  
Acidic Medium ◽  
Colloidal Particles ◽  
Spent Nuclear Fuel ◽  
Alkaline Solutions ◽  
Dissolution Mechanism ◽  
Nuclear Fuels ◽  
Solution Composition ◽  
Geological Disposal ◽  
Composition Effects

ABSTRACTThis study investigates the dissolution of CeO2, an isostructural analogue for UO2 and ThO2, which was synthesized to closely approximate the microstructure of a spent nuclear fuel matrix. Dissolution of CeO2 particles was performed in simplified solutions representative of saline, near-neutral and alkaline ground waters that may be encountered in geological disposal scenarios, and in acidic medium for comparison. The normalized mass loss of cerium was found to be significantly influenced by the formation of colloidal particles, especially in the near-neutral and alkaline solutions investigated. The normalized dissolution rate, RL(Ce), k (g m-2 d-1), in these two solutions was found to be similar, but significantly lower than in a nitric acid medium. The activation energies based on the normalized release rate of cerium, at 40°C, 70°C and 90°C in each solution, were in the range of 24 ± 3 kJ mol-1 to 27 ± 7 kJ mol-1, indicative of a surface-mediated dissolution mechanism. The mechanism of dissolution was postulated to be similar in each of the solutions investigated, and further work is proposed to investigate the role of carbonate on the CeO2 dissolution mechanism.

Modelling the Activation of H2 on Spent Fuel Surface and Inhibiting Effect of UO2 Dissolution

2013 ◽  
Vol 1518 ◽  
pp. 133-138 ◽  
Author(s):  
L. Duro ◽  
O. Riba ◽  
A. Martínez-Esparza ◽  
J. Bruno
Keyword(s):  
Nuclear Fuel ◽  
Spent Nuclear Fuel ◽  
Fuel Pellet ◽  
Dissolution Behavior ◽  
Dissolution Mechanism ◽  
Water Radiolysis ◽  
Spent Fuel ◽  
Secondary Phases ◽  
The Matrix ◽  
Fuel Storage

ABSTRACTThe dissolution of spent nuclear fuel is defined in two different time steps, i) the Instant Release Fraction (IRF) occurring shortly after water contacts the solid spent fuel and responsible of the fast release of those radionuclides that have been accumulated in the zones of the spent fuel pellet with low confinement, such as gap and grain boundaries and ii) the long term release of radionuclides confined in the spent fuel matrix, much slower and dependent on the conditions of the water that contacts the spent fuel.Several models have been developed to date to explain the dissolution behavior of spent nuclear fuel under disposal conditions. The Matrix Alteration Model (MAM) is one of the most evolved radiolytic models describing the dissolution mechanism in which an Alteration/Dissolution source term model is based on the oxidative dissolution of spent fuel. Under deep repository conditions and at the expected of water contacting time (after 1000 years of spent fuel storage), α radiation will be the main contributor to water radiolysis. In the current study, simulations evaluating the effect of surface area on the alteration/dissolution of spent fuel matrix are performed considering different particle sizes of spent fuel and simulations integrating the actinides dissolution have been performed considering the precipitation of secondary phases.

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