ICEM11 Final Program 9.7.11pm_ICEM07 Final Program ... - Events

Session 32 Abstracts
3) CHARACTERISATION OF BEDROCK HYDROGEOLOGY AT THE OLKILUOTO
SITE USING SURFACE BASED AND UNDERGROUND DATA (w/oP-59095)
Lee Hartley, Dave Swan, Steven Baxter, SERCO (UK)
Posiva Oy is responsible for implementing the programme for geological disposal of spent nuclear fuel in Finland. Olkiluoto
in Eurajoki has been selected as the primary site for the repository, subject to further detailed characterisation which is currently
focused on the construction of an underground rock characterisation and research facility (the ONKALO). An essential part of the
site investigation programme is analysis of groundwater flow and solute transport to depth by means of numerical flow modelling
as part of the 2011 site descriptive model. Groundwater flow in the crystalline rocks at Olkiluoto takes place predominantly in the
void space of the interconnected fractures in the bedrock. Many of the hydraulic characteristics of flow through such a system can
be represented by hydrogeological Discrete Fracture Network (DFN) models, since they capture some of the details of fracture
geometry, size, connectivity and openings. The paper describes how field data is used to derive such models, ultimately for use in
safety assessment.
Surface based site investigations at Olkiluoto include 53 sub-vertical deep core drilled boreholes and 27 shallower sub-vertical
boreholes. The characterisation of fractures is a key objective. Fracture geometrical data (fracture positions and orientations)
are determined from drill core mapping and/or borehole ...
4) SELF-DISPOSAL OPTION FOR HEAT-GENERATING WASTE (wP-59182)
Michael Ojovan, University of Sheffield; Pavel Poluektov, Vladimir Kascheev, A.A. Bochvar’s VNIINM (UK/Russia)
Self-descending heat generating capsules can be used for disposal of dangerous radioactive wastes in extremely deep layers of
the Earth preventing any release of radionuclides into the biosphere. Self-disposal option for heat-generating radioactive waste such
as spent fuel, high level reprocessing waste or spent sealed radioactive sources, known also as rock melting concept, was considered
in the 70s as a viable alternative disposal option by both Department of Energy in the USA and Atomic Industry Ministry in
the USSR. Self-disposal is currently reconsidered as a potential alternative route to existing options for solving the nuclear waste
problem and is associated with the renaissance of nuclear industry. Self-disposal option utilises the heat generated by decaying
radionuclides of radioactive waste inside a heavy and durable capsule to melt the rock on its way down. As the heat from radionuclides
within the capsule partly melts the enclosing rock, the relatively low viscosity and density of the silicate melt allow capsule
to be displaced upwards past the heavier capsule as it sinks. Eventually the melt cools and solidifies (e.g. vitrifies or crystallizes),
sealing the route along which the capsule passed. Descending or self-disposal continues until enough heat is generated by radionuclides
to provide partial ...
5) NUMOS APPROACH FOR LONG-TERM SAFETY ASSESSMENT (wP-59404)
Takeshi Ebashi, Kenichi Kaku, Katsuhiko Ishiguro, Nuclear Waste Management Organization of Japan (NUMO) (Japan)
In Japan, the Act on Final Disposal of Specified Radioactive Waste specifies that the repository siting process shall consist of
three stages. The Nuclear Waste Management Organization of Japan (NUMO) is responsible for geological disposal of vitrified
high-level waste and some types of TRU waste. NUMO has chosen to implement a volunteer approach to siting.
NUMO decided to prepare the 2010 Technical Report, which sets out three policies for ensuring safety. One of these is staged
project implementation and decision-making based on iterative confirmation of safety. Based on this, NUMO will gradually integrate
relevant interdisciplinary knowledge to build a safety case once a formal volunteer application is received that would allow
site investigations to be initiated. The safety assessment takes the central role in multiple lines of reasoning and argumentation by
providing a quantitative evaluation of long-term safety, a key aspect of which is uncertainty management.
This paper presents NUMOs basic strategy for long-term safety assessment, based on the above policy.
In concrete terms, safety assessment procedures are described in the context of the staged implementation programme, based
on integration of knowledge obtained from site investigation/evaluation and engineering studies and reflection of the safety assessment
results in the planning of ...
6) MODELING APPROACHES FOR EVALUATING THE EFFECT OF HETEROGENEITY ON
TWO-PHASE FLOW ASSOCIATED WITH THE MIGRATION OF WASTE GENERATED GAS
FROM SF/HLW- AND L/ILW REPOSITORIES IN LOW-PERMEABILITY FORMATIONS (wP-59196)
Alexandros Papafotiou, Rainer Senger, Intera Inc. Swiss Branch; Andrés Alcolea, TK Consult AG;
William Lanyon, Fracture-Systems Ltd; John Ewing, Intera Inc. Swiss Branch (Switzerland/UK)
Different low-permeability formations are considered as potential host rocks for Low / Intermediate Level waste (L/ILW) and
spent fuel / high-level / long-lived intermediate-level waste (SF/HLW/ILW) in Switzerland. As part of a generic site evaluation
process, emphasis is on the assessment of Mesozoic limestones, marls and claystones in six potential siting areas in Northern and
Central Switzerland. An important aspect in the site evaluation process is the characterization of the low-permeability formations
in terms of spatial variability of the relevant transport properties (porosity, permeability, clay content), as they may affect the migration
of waste-generated gas from L/ILW and SF/HLW/ILW repositories.
Numerical modeling studies are presented, aimed at quantifying the impact of spatial variability of rock properties on gas
release through the host rock on a deca- to hectometer scale. For this purpose, 2-D models of an emplacement tunnel embedded in
a low-permeability host rock are developed for both a sequence of limestones and marls with distinct lithological variability (Effingen
Beds) and a claystone of moderate spatial variability (Opalinus Clay). For the Effingen Beds, a composite geological model is
implemented, comprising stochastic representations of the different facies and the fracture systems. The facies model displays spatial
variations in clay content, porosity ...
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