Uranium-Series Studies in Bedrock for the Safety Case of Deep Geological Disposal of Spent Fuel

AbstractA plutonia stabilised zirconia doped with yttria and erbia has been selected as inert matrix fuel (IMF) at PSI. The results of experimental irradiation tests on yttria-stabilised zirconia doped with plutonia and erbia pellets in the Halden research reactor as well as a study of zirconia solubility are presented. Zirconia must be stabilised by yttria to form a solid solution such as MAz(Y,Er)yPuxZr1-yO2-ζ where minor actinides (MA) oxides are also soluble. (Er,Y,Pu,Zr)O2-ζ (with Pu containing 5% Am) was successfully prepared at PSI and irradiated in the Halden reactor. Emphasis is given on the zirconia-IMF properties under in-pile irradiation, on the fuel material centre temperatures and on the fission gas release. The retention of fission products in zirconia may be stronger at similar temperature, compared to UO2. The outstanding behaviour of plutonia-zirconia inert matrix fuel is compared to the classical (U,Pu)O2 fuels. The properties of the spent fuel pellets are presented focusing on the once through strategy. For this strategy, low solubility of the inert matrix is required for geological disposal. This parameter was studied in detail for a range of solutions corresponding to groundwater under near field conditions. Under these conditions the IMF solubility is about 109 times smaller than glass, several orders of magnitude lower than UO2 in oxidising conditions (Yucca Mountain) and comparable in reducing conditions, which makes the zirconia material very attractive for deep geological disposal. The behaviour of plutonia-zirconia inert matrix fuel is discussed within a burn and bury strategy.

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Consequence modelling of hypothetical post-closure criticality events for spent fuel disposal

Mineralogical Magazine ◽

10.1180/minmag.2015.079.6.25 ◽

2015 ◽

Vol 79 (6) ◽

pp. 1505-1513 ◽

Cited By ~ 2

Author(s):

R. M. Mason ◽

J. K. Martin ◽

P. N. Smith ◽

R. J. Winsley

Keyword(s):

International Studies ◽

Quasi Steady State ◽

Spent Fuel ◽

Regulatory Requirement ◽

Geological Disposal ◽

Waste Package ◽

Decay Heat ◽

Disposal Facility ◽

Safety Case ◽

The Uk

AbstractIn support of the Radioactive Waste Management (RWM) safety case for a geological disposal facility (GDF) in the UK, there is a regulatory requirement to consider the likelihood and consequences of nuclear criticality. Waste packages are designed to ensure that criticality is not possible during the transport and operational phases of a GDF and for a significant period post-closure. However, over longer post-closure timescales, conditions in the GDF will evolve.For waste packages containing spent fuel, it can be shown that, under certain conditions, package flooding could result in a type of criticality event referred to as 'quasi-steady-state' (QSS). Although unlikely, this defines a 'what-if' scenario for understanding the potential consequences of post-closure criticality. This paper provides an overview of a methodology to understand QSS criticality and its application to a spent fuel waste package.The power of such a hypothetical criticality event is typically estimated to be a few kilowatts: comparable with international studies of similar systems and the decay heat for which waste packages are designed. This work has built confidence in the methodology and supports RWM's demonstration that post-closure criticality is not a significant concern.

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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

EPJ Nuclear Sciences & Technologies ◽

10.1051/epjn/2019038 ◽

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.

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Understanding the likelihood and consequences of post-closure criticality in a geological disposal facility

Mineralogical Magazine ◽

10.1180/minmag.2015.079.6.30 ◽

2015 ◽

Vol 79 (6) ◽

pp. 1551-1561 ◽

Cited By ~ 3

Author(s):

R. J. Winsley ◽

T. D. Baldwin ◽

T. W. Hicks ◽

R. M. Mason ◽

P. N. Smith

Keyword(s):

Spent Fuel ◽

Geological Disposal ◽

Safe Disposal ◽

Waste Package ◽

Disposal Facility ◽

Safety Case ◽

Operational Phase ◽

Strength Rock ◽

Criticality Safety

AbstractA geological disposal facility (GDF) will include fissile materials that could, under certain conditions, lead to criticality. Demonstration of criticality safety therefore forms an important part of a GDF's safety case.Containment provided by the waste package will contribute to criticality safety during package transport and the GDF operational phase. The GDF multiple-barrier system will ensure that criticality is prevented for some time after facility closure. However, on longer post-closure timescales, conditions in the GDF will evolve and it is necessary to demonstrate: an understanding of the conditions under which criticality could occur; the likelihood of such conditions occurring; and the consequences of criticality should it occur.Work has addressed disposal of all of the UK's higher-activity wastes in three illustrative geologies. This paper, however, focuses on presenting results to support safe disposal of spent fuel, plutonium and highlyenriched uranium in higher-strength rock.The results support a safety case assertion that post-closure criticality is of low likelihood and, if it was to occur, the consequences would be tolerable.

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Study of SIMFUEL corrosion under hyper-alkaline conditions in the presence of silicate and calcium

MRS Advances ◽

10.1557/adv.2016.619 ◽

2016 ◽

Vol 2 (10) ◽

pp. 543-548

Author(s):

Alexandra Espriu-Gascon ◽

David W. Shoesmith ◽

Javier Giménez ◽

Ignasi Casas ◽

Joan de Pablo

Keyword(s):

Corrosion Potential ◽

Oxidation Process ◽

Spent Fuel ◽

Cyclic Voltammetric ◽

Geological Disposal ◽

Similar Composition ◽

X Ray ◽

Deep Geological Disposal ◽

Alkaline Conditions ◽

Main Components

ABSTRACTCement has been considered as a possible material present in the Deep Geological Disposal (DGD) [1] . In order to determine the effect of cementitious waters on the oxidation of the surface of Spent Fuel (SF), a series of electrochemical experiments were performed, to study the influence of two main components of cementitious water: calcium and silicate.Test solutions with Na2SiO3 and/or CaCl2 were prepared at pH 12 and NaCl 0.1 mol·dm-3 as ionic medium. A 3 at.% doped SIMFUEL was used to perform cyclic voltammetric (CV), potentiostatic and corrosion potential (ECORR) experiments. After potentiostatic and ECORR experiments, the SIMFUEL surface was analyzed using X-Ray Photoelecton Spectroscopy (XPS).The results showed that the presence of silicate decreased the SIMFUEL oxidation between -100 mV and 300 mV. When Ca2+ was added, the whole oxidation process was shifted to higher potentials which indicated a protective effect of the combination of Ca2+ and SiO32- . The XPS results obtained after potentiostatic experiments at 200 mV showed that the presence of silicate partially suppressed the oxidation of SIMFUEL, as indicated by the contribution of both U(IV) and U(V) XPS to the U 4f7/2 band (∼ 38%). After the addition of calcium, the predominant uranium oxidized state contribution on the surface was U(V) (40%). After the ECORR experiments, the ECORR values were similar either with or without silicate in solution (-80 mV and -70 mV respectively). The resulting surface also exhibited a similar composition. When calcium was added to the electrolyte, the ECORR value was suppressed to -105 mV, and XPS showed that the surface was less oxidized than with the other two electrolytes.

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Preliminary modelling of radionuclide migration in the argillaceous sediments of the Sumer Formation (Northwestern Bulgaria)

Geologica Balcanica ◽

10.52321/geolbalc.49.3.13 ◽

2020 ◽

Vol 49 (3) ◽

pp. 13-18

Author(s):

Dimitar Antonov ◽

Madlena Tsvetkova ◽

Doncho Karastanev

Keyword(s):

Radioactive Waste Disposal ◽

High Level Waste ◽

Spent Fuel ◽

Radionuclide Migration ◽

Geological Disposal ◽

Disposal Facility ◽

Deep Geological Disposal ◽

High Level ◽

Host Rocks ◽

Selection Of

In Bulgaria, from the preliminary analyses performed for site selection of deep geological disposal of high-level waste (HLW) and spent fuel (SF), it was concluded that the most promising host rocks are the argillaceous sediments of the Sumer Formation (Lower Cretaceous), situated in the Western Fore-Balkan Mts. The present paper aims to compare the transport of three major radionuclides from a hypothetical radioactive waste disposal facility, which incorporates an engineering barrier of bentonite into the argillaceous (marl) medium. The simulations were performed by using HYDRUS-1D computer programme. The results are used for a preliminary estimation of argillaceous sediments as a host rock for geological disposal of HLW.

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An Analysis of the Deep Geological Disposal Concepts Considering Spent Fuel Rods Consolidation

Journal of the Nuclear Fuel Cycle and Waste Technology(JNFCWT) ◽

10.7733/jnfcwt.2014.12.4.287 ◽

2014 ◽

Vol 12 (4) ◽

pp. 287-297

Author(s):

Jongyoul Lee ◽

Hyeona Kim ◽

Minsoo Lee ◽

Geonyoung Kim ◽

Heuijoo Choi

Keyword(s):

Spent Fuel ◽

Fuel Rods ◽

Geological Disposal ◽

Deep Geological Disposal

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Radioactive waste management in France: safety demonstration fundamentals

Annals of the ICRP ◽

10.1016/j.icrp.2012.06.026 ◽

2012 ◽

Vol 41 (3-4) ◽

pp. 286-293 ◽

Cited By ~ 1

Author(s):

G. Ouzounian ◽

S. Voinis ◽

F. Boissier

Keyword(s):

Radioactive Waste ◽

Heat Generation ◽

Geological Disposal ◽

Sequence Of Events ◽

Main Challenge ◽

Wide Range ◽

Deep Geological Disposal ◽

Safety Case ◽

High Level ◽

Geological Timescale

The main challenge in development of the safety case for deep geological disposal is associated with the long periods of time over which high- and intermediate-level long-lived wastes remain hazardous. A wide range of events and processes may occur over hundreds of thousands of years. These events and processes are characterised by specific timescales. For example, the timescale for heat generation is much shorter than any geological timescale. Therefore, to reach a high level of reliability in the safety case, it is essential to have a thorough understanding of the sequence of events and processes likely to occur over the lifetime of the repository. It then becomes possible to assess the capability of the repository to fulfil its safety functions. However, due to the long periods of time and the complexity of the events and processes likely to occur, uncertainties related to all processes, data, and models need to be understood and addressed. Assessment is required over the lifetime of the radionuclides contained in the radioactive waste.

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Needs of countries with longer timescale for deep geological repository implementation

EPJ Nuclear Sciences & Technologies ◽

10.1051/epjn/2019042 ◽

2020 ◽

Vol 6 ◽

pp. 22

Author(s):

Bálint Nős

Keyword(s):

Nuclear Power ◽

Power Plants ◽

High Level Waste ◽

Deep Geological Repository ◽

Spent Fuel ◽

International Consensus ◽

Geological Disposal ◽

Geological Repository ◽

Deep Geological Disposal ◽

High Level

Countries operating nuclear power plants have to deal with the tasks connected to spent fuel and high-level radioactive waste management. There is international consensus that, at this time, deep geological disposal represents the safest and most sustainable option as the end point of the management of high-level waste and spent fuel considered as waste. There are countries with longer timescale for deep geological repository (DGR) implementation, meaning that the planned date of commissioning of their respective DGRs is around 2060. For these countries cooperation, knowledge transfer, participation in RD&D programmes (like EURAD) and adaptation of good international practice could help in implementing their own programmes. In the paper the challenges and needs of a country with longer implementation timescale for DGR will be introduced through the example of Hungary.

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