The 12th International Conference on Environmental ... - Events

Session 15-16 Abstracts
5) MODELLING LONG-TERM CORROSION OF CEMENTED WASTE FORMS IN SALT BRINES - 16202
Bernhard Kienzler, Volker Metz, Forschungszentrum Karlsruhe (Germany)
Since 1979, leaching and corrosion experiments have been performed at the Asse II salt mine using simulated full-scale
cemented waste forms. <strong>The</strong> cement blocks, doped with 137Cs and uranium, have been exposed to saturated salt brines. <strong>The</strong> brines
have been sampled regularly and analysed with respect to the mobilized radionuclides, pH, and major solution components. In
2006, four of the cement blocks samples were recovered and solid samples were obtained by drilling vertically into the corroded
cement forms. <strong>The</strong> drill cores as well as abraded drill dust were analysed with respect to chemical and mineralogical compositions,
distributions of radionuclides and major waste components, thermogravimetric and mechanical properties. Results of these methods
show consistently that cement forms, having an initial W/C = 0.5, were homogeneously corroded in MgCl2 rich brine. No vertical
or radial variations were found with respect to major chemical components and mineral phases. In the cement blocks corroded
in NaCl saturated brine, spatial heterogeneities in the distribution of major anions (chloride, nitrate) and the trace cation Cs+
show that these cement / NaCl systems have not been completely homogenized within 22 years. Concentration profiles of Cl-, NO3 - and Cs+ were compared with calculated profiles to quantify diffusion coefficients and to get information on the kinetics of relevant
processes. Simulations of chemical alteration of the cement / brine system indicate that both MgCl2-rich and NaCl systems are
close to equilibrium with respect to stabilities of secondary mineral phases.
6) COUPLING TIME-DEPENDENT SORPTION VALUES OF DEGRADING
CONCRETE WITH A RADIONUCLIDE MIGRATION MODEL - 16220
Janez Perko, Dirk Mallants, Diederik Jacques, Lian Wang,Belgian Nuclear Research Centre SCK-CEN (Belgium)
Safety assessment of radioactive waste disposal facilities is usually carried out by means of simplified models. Abstraction of
the numerical model from the real physical environment is done in several steps. One of the most challenging issues in safety
assessment concerns the long time scales involved and the evolution of engineered barriers over thousands of years. For some
processes occurring in specific engineered barriers the uncertainties related to long time scales are addressed by implementing conservative
assumptions in the radionuclide migration models. Other processes such as chemical concrete degradation, however, can
be estimated for long time periods by the use of coupled geochemical transport models. For many near-surface disposal facilities,
concrete is a very important engineered barrier because it is used in the construction of disposal modules or vaults, in production
of high-integrity monoliths and their backfilling and for waste conditioning. Knowledge on the durability of such concrete components
and its relation to radionuclide sorption is important for a defensible safety assessment. Chemical degradation typically occurs
as the result of decalcification, dissolution and leaching of cement components and carbonation. <strong>The</strong>se reactions induce a gradual
change in the solid phase composition and the concrete pore-water composition, from “fresh” concrete porewater with a pH above
13 to a pH lower than 10 for “evolved” porewater associated with fully degraded concrete.
7) A NUMERICAL STUDY OF FACTORS AFFECTING RADIOACTIVE
GAS MIGRATION IN THE FAR-FIELD - 16273
Elina Kuitunen, Michael A. Hicks, <strong>The</strong> University of Manchester (UK)
Gases are produced in radiological waste repositories through several processes. While the bulk of the gas produced is expected
to be hydrogen, some gases labelled with radionuclides such as tritium and carbon-14 are also formed. <strong>The</strong> consequences of the
generation and migration of these gases need to be assessed in order to ensure the safety of a radiological waste repository.
Different disposal concepts are employed internationally to deal with repository gases and radionuclide migration. This paper
presents the results of preliminary analyses carried out using the code TOUGH2. Specifically, parametric studies for simplified
geometries have been carried out in order to assess the relative importance of the governing parameters of gas migration. This forms
the first stage of numerically assessing the safety of different repository designs with regards to radioactive gas migration. By identifying
the near-field factors with the highest impacts on gas migration in the far-field, the repository designs can be further
improved.
SESSION 16 - NATIONAL AND INTERNATIONAL PROGRAMS FOR SPENT FUEL, FISSILE,
TRU, AND HLW MANAGEMENT
1) NUMO-RMS: A PRACTICAL REQUIREMENTS MANAGEMENT SYSTEM FOR THE LONG-TERM
MANAGEMENT OF THE DEEP GEOLOGICAL DISPOSAL PROJECT - 16304
Hiroyoshi Ueda, Satoru Suzuki, Katsuhiko Ishiguro, NuclearWaste Management Organization of Japan (NUMO)
(Japan);Kiyoshi Oyamada, JGC Corporation (Japan); Shoko Yashio, Obayashi Corporation (Japan);
Matt White, Roger Wilmot,Galson Sciences Limited (UK)
NUMO (Nuclear Waste Management Organization of Japan) has the responsibility for implementing deep geological disposal
of high-level (HLW) and transuranic (TRU) radioactive waste from the Japanese nuclear programme. A formal Requirements Management
System (RMS) is planned to efficiently and effectively support the computerized implementation of the management strategy
and the methodology required to drive the step-wise siting processes, and the following repository operational phase,. <strong>The</strong> RMS
will help in the comprehensive management of the decision-making processes in the geological disposal project, in change management
as the disposal system is optimised, in driving projects such as the R&D programme efficiently, and in maintaining structured
records regarding past decisions, all of which lead to soundness of the project in terms of long-term continuity.
<strong>The</strong> system is planned to have information handling and management functions using a database that includes the
decisions/requirements in the programme under consideration, the way in which these are structured in terms of the decisionmaking
process and other associated information. A two-year development programme is underway to develop and enhance an existing trial
RMS to a practical system. Functions for change management, history management and association with the external timeline management
system are being implemented in the system development work. <strong>The</strong> database format is being improved to accommodate
the requirements management data relating to the facility design and to safety assessment of the deep geological repository.
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