The 12th International Conference on Environmental ... - Events
The 12th International Conference on Environmental ... - Events
The 12th International Conference on Environmental ... - Events
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Sessi<strong>on</strong> 15-16 Abstracts<br />
5) MODELLING LONG-TERM CORROSION OF CEMENTED WASTE FORMS IN SALT BRINES - 16202<br />
Bernhard Kienzler, Volker Metz, Forschungszentrum Karlsruhe (Germany)<br />
Since 1979, leaching and corrosi<strong>on</strong> experiments have been performed at the Asse II salt mine using simulated full-scale<br />
cemented waste forms. <str<strong>on</strong>g>The</str<strong>on</strong>g> cement blocks, doped with 137Cs and uranium, have been exposed to saturated salt brines. <str<strong>on</strong>g>The</str<strong>on</strong>g> brines<br />
have been sampled regularly and analysed with respect to the mobilized radi<strong>on</strong>uclides, pH, and major soluti<strong>on</strong> comp<strong>on</strong>ents. In<br />
2006, four of the cement blocks samples were recovered and solid samples were obtained by drilling vertically into the corroded<br />
cement forms. <str<strong>on</strong>g>The</str<strong>on</strong>g> drill cores as well as abraded drill dust were analysed with respect to chemical and mineralogical compositi<strong>on</strong>s,<br />
distributi<strong>on</strong>s of radi<strong>on</strong>uclides and major waste comp<strong>on</strong>ents, thermogravimetric and mechanical properties. Results of these methods<br />
show c<strong>on</strong>sistently that cement forms, having an initial W/C = 0.5, were homogeneously corroded in MgCl2 rich brine. No vertical<br />
or radial variati<strong>on</strong>s were found with respect to major chemical comp<strong>on</strong>ents and mineral phases. In the cement blocks corroded<br />
in NaCl saturated brine, spatial heterogeneities in the distributi<strong>on</strong> of major ani<strong>on</strong>s (chloride, nitrate) and the trace cati<strong>on</strong> Cs+<br />
show that these cement / NaCl systems have not been completely homogenized within 22 years. C<strong>on</strong>centrati<strong>on</strong> profiles of Cl-, NO3 - and Cs+ were compared with calculated profiles to quantify diffusi<strong>on</strong> coefficients and to get informati<strong>on</strong> <strong>on</strong> the kinetics of relevant<br />
processes. Simulati<strong>on</strong>s of chemical alterati<strong>on</strong> of the cement / brine system indicate that both MgCl2-rich and NaCl systems are<br />
close to equilibrium with respect to stabilities of sec<strong>on</strong>dary mineral phases.<br />
6) COUPLING TIME-DEPENDENT SORPTION VALUES OF DEGRADING<br />
CONCRETE WITH A RADIONUCLIDE MIGRATION MODEL - 16220<br />
Janez Perko, Dirk Mallants, Diederik Jacques, Lian Wang,Belgian Nuclear Research Centre SCK-CEN (Belgium)<br />
Safety assessment of radioactive waste disposal facilities is usually carried out by means of simplified models. Abstracti<strong>on</strong> of<br />
the numerical model from the real physical envir<strong>on</strong>ment is d<strong>on</strong>e in several steps. One of the most challenging issues in safety<br />
assessment c<strong>on</strong>cerns the l<strong>on</strong>g time scales involved and the evoluti<strong>on</strong> of engineered barriers over thousands of years. For some<br />
processes occurring in specific engineered barriers the uncertainties related to l<strong>on</strong>g time scales are addressed by implementing c<strong>on</strong>servative<br />
assumpti<strong>on</strong>s in the radi<strong>on</strong>uclide migrati<strong>on</strong> models. Other processes such as chemical c<strong>on</strong>crete degradati<strong>on</strong>, however, can<br />
be estimated for l<strong>on</strong>g time periods by the use of coupled geochemical transport models. For many near-surface disposal facilities,<br />
c<strong>on</strong>crete is a very important engineered barrier because it is used in the c<strong>on</strong>structi<strong>on</strong> of disposal modules or vaults, in producti<strong>on</strong><br />
of high-integrity m<strong>on</strong>oliths and their backfilling and for waste c<strong>on</strong>diti<strong>on</strong>ing. Knowledge <strong>on</strong> the durability of such c<strong>on</strong>crete comp<strong>on</strong>ents<br />
and its relati<strong>on</strong> to radi<strong>on</strong>uclide sorpti<strong>on</strong> is important for a defensible safety assessment. Chemical degradati<strong>on</strong> typically occurs<br />
as the result of decalcificati<strong>on</strong>, dissoluti<strong>on</strong> and leaching of cement comp<strong>on</strong>ents and carb<strong>on</strong>ati<strong>on</strong>. <str<strong>on</strong>g>The</str<strong>on</strong>g>se reacti<strong>on</strong>s induce a gradual<br />
change in the solid phase compositi<strong>on</strong> and the c<strong>on</strong>crete pore-water compositi<strong>on</strong>, from “fresh” c<strong>on</strong>crete porewater with a pH above<br />
13 to a pH lower than 10 for “evolved” porewater associated with fully degraded c<strong>on</strong>crete.<br />
7) A NUMERICAL STUDY OF FACTORS AFFECTING RADIOACTIVE<br />
GAS MIGRATION IN THE FAR-FIELD - 16273<br />
Elina Kuitunen, Michael A. Hicks, <str<strong>on</strong>g>The</str<strong>on</strong>g> University of Manchester (UK)<br />
Gases are produced in radiological waste repositories through several processes. While the bulk of the gas produced is expected<br />
to be hydrogen, some gases labelled with radi<strong>on</strong>uclides such as tritium and carb<strong>on</strong>-14 are also formed. <str<strong>on</strong>g>The</str<strong>on</strong>g> c<strong>on</strong>sequences of the<br />
generati<strong>on</strong> and migrati<strong>on</strong> of these gases need to be assessed in order to ensure the safety of a radiological waste repository.<br />
Different disposal c<strong>on</strong>cepts are employed internati<strong>on</strong>ally to deal with repository gases and radi<strong>on</strong>uclide migrati<strong>on</strong>. This paper<br />
presents the results of preliminary analyses carried out using the code TOUGH2. Specifically, parametric studies for simplified<br />
geometries have been carried out in order to assess the relative importance of the governing parameters of gas migrati<strong>on</strong>. This forms<br />
the first stage of numerically assessing the safety of different repository designs with regards to radioactive gas migrati<strong>on</strong>. By identifying<br />
the near-field factors with the highest impacts <strong>on</strong> gas migrati<strong>on</strong> in the far-field, the repository designs can be further<br />
improved.<br />
SESSION 16 - NATIONAL AND INTERNATIONAL PROGRAMS FOR SPENT FUEL, FISSILE,<br />
TRU, AND HLW MANAGEMENT<br />
1) NUMO-RMS: A PRACTICAL REQUIREMENTS MANAGEMENT SYSTEM FOR THE LONG-TERM<br />
MANAGEMENT OF THE DEEP GEOLOGICAL DISPOSAL PROJECT - 16304<br />
Hiroyoshi Ueda, Satoru Suzuki, Katsuhiko Ishiguro, NuclearWaste Management Organizati<strong>on</strong> of Japan (NUMO)<br />
(Japan);Kiyoshi Oyamada, JGC Corporati<strong>on</strong> (Japan); Shoko Yashio, Obayashi Corporati<strong>on</strong> (Japan);<br />
Matt White, Roger Wilmot,Gals<strong>on</strong> Sciences Limited (UK)<br />
NUMO (Nuclear Waste Management Organizati<strong>on</strong> of Japan) has the resp<strong>on</strong>sibility for implementing deep geological disposal<br />
of high-level (HLW) and transuranic (TRU) radioactive waste from the Japanese nuclear programme. A formal Requirements Management<br />
System (RMS) is planned to efficiently and effectively support the computerized implementati<strong>on</strong> of the management strategy<br />
and the methodology required to drive the step-wise siting processes, and the following repository operati<strong>on</strong>al phase,. <str<strong>on</strong>g>The</str<strong>on</strong>g> RMS<br />
will help in the comprehensive management of the decisi<strong>on</strong>-making processes in the geological disposal project, in change management<br />
as the disposal system is optimised, in driving projects such as the R&D programme efficiently, and in maintaining structured<br />
records regarding past decisi<strong>on</strong>s, all of which lead to soundness of the project in terms of l<strong>on</strong>g-term c<strong>on</strong>tinuity.<br />
<str<strong>on</strong>g>The</str<strong>on</strong>g> system is planned to have informati<strong>on</strong> handling and management functi<strong>on</strong>s using a database that includes the<br />
decisi<strong>on</strong>s/requirements in the programme under c<strong>on</strong>siderati<strong>on</strong>, the way in which these are structured in terms of the decisi<strong>on</strong>making<br />
process and other associated informati<strong>on</strong>. A two-year development programme is underway to develop and enhance an existing trial<br />
RMS to a practical system. Functi<strong>on</strong>s for change management, history management and associati<strong>on</strong> with the external timeline management<br />
system are being implemented in the system development work. <str<strong>on</strong>g>The</str<strong>on</strong>g> database format is being improved to accommodate<br />
the requirements management data relating to the facility design and to safety assessment of the deep geological repository.<br />
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