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

Abstracts Session 15
SESSION 15 - DISPOSAL SITE AND WASTE FORM CHARACTERIZATION AND PERFORMANCE ASSESSMENT
1) A PRELIMINARY POSTCLOSURE SAFETY ASSESSMENT OF OPGS PROPOSED
L&ILW DEEP GEOLOGIC REPOSITORY, CANADA - 16289
Richard Little, Quintessa Limited (UK); John Avis, Nicola Calder, Intera Engineering Limited (Canada); Nava Garisto,
Senes Consultants Limited (Canada) Paul Gierszewski, Helen Leung, Nuclear Waste Management Organization
(Canada);Laura Limer, James Penfold, George Towler, Russell Walke,Robert Walsh, Quintessa Limited (UK)
Ontario Power Generation (OPG) is proposing to build a Deep Geologic Repository (DGR) for Low and Intermediate Level
Waste (L&ILW) near the existing Western Waste Management Facility at the Bruce site in the Municipality of Kincardine, Ontario.
<strong>The</strong> Nuclear Waste Management Organization (NWMO), on behalf of OPG, is currently preparing an Environmental Impact Statement
(EIS) and Preliminary Safety Report (PSR) for the proposed repository. This involves investigation of the site’s geological
and surface environmental characteristics, conceptual design of the DGR, and technical studies to demonstrate the operational and
long-term safety of the proposed facility. A preliminary postclosure safety assessment (SA) was undertaken in 2008 and 2009.
Consistent with the guidelines for the preparation of the EIS for the DGR and the regulatory guide on assessing the long-term
safety of radioactive waste management, the SA evaluated the DGR’s performance and its potential impact on human health and
the environment through pathway analysis of contaminant releases, contaminant transport, receptor exposure and potential effects.
Consideration was given to the expected long-term evolution of the repository and site following closure (the Normal Evolution
Scenario) and four disruptive (what if) scenarios (Human Intrusion, Severe Shaft Seal Failure, Open Borehole, and Extreme Earthquake),
which considered events with uncertain or low probability that could disrupt the repository system.
2) NUMERICAL ASSESSMENT OF THE LONG-TERM SAFETY OF THE MORSLEBEN REPOSITORY
FOR LOW- AND INTERMEDIATE-LEVEL RADIOACTIVE WASTE - 16346
Juergen Wollrath, Juergen Preuss, Bundesamt fuerStrahlenschutz (BfS) (Germany); Dirk-Alexander Becker, Joerg
Moenig, Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH (UK)
<strong>The</strong> Morsleben repository has been in operation since 1971 as a repository for low- and intermediate-level radioactive waste.
Until the end of the disposal phase in 1998 a waste volume of about 37,000 m3 with a total activity of 4.5·1014 Bq was disposed
of. Currently, the German Federal Office for Radiation Protection (BfS) is applying for the licence to finally close the repository.
Concerning the possible release of radionuclides to the biosphere, the repository is subject to German radiation protection regulations.
<strong>The</strong>ir fulfilment has to be proven by means of numerical calculations as a part of the safety case.
A simplified repository model has been developed by GRS and used for calculating the consequences of different scenarios
and variants, as well as for a probabilistic uncertainty and sensitivity analysis. <strong>The</strong> application for licensing is, among others, based
on these results.
In this paper the main features of the model and the underlying assumptions, as well as the most important calculation results
are presented and explained.
3) THE DEVELOPMENT AND USE OF T2GGM: A GAS MODELLING CODE FOR THE POSTCLOSURE SAFETY
ASSESSMENT OF OPGS PROPOSED L&ILW DEEP GEOLOGIC REPOSITORY, CANADA - 16291
Paul Suckling, Quintessa Limited (UK); Nicola Calder, Intera Engineering Limited (Canada);
Paul Humphreys, University of Huddersfield (UK); Fraser King, Integrity Corrosion Consulting Limited Canada);
Helen Leung, Nuclear Waste Management Organization (Canada)
As part of the postclosure safety assessment of Ontario Power Generation’s (OPG’s) proposed Deep Geologic Repository
(DGR) for Low and Intermediate Level Waste (L&ILW) at the Bruce site, Ontario, a Gas Generation Model (GGM) has been developed
and used to model the detailed generation of gas within the DGR due to corrosion and microbial degradation of the organics
and metals present.
<strong>The</strong> GGM is based on a kinetic description of the various microbial and corrosion processes that lead to the generation and
consumption of various gases. It takes into account the mass-balance equations for each of the species included in the model,
including three forms of organic waste (cellulose, ion-exchange resins, and plastics and rubbers), four metallic waste forms and
container materials (carbon and galvanised steel, passivated carbon steel, stainless steel and nickel-based alloys, and zirconium
alloys), six gases (CO2 , N2, O2 , H2 , H2S, and CH4 ), five terminal electron acceptors (O2 , NO3 , Fe(III), SO 2-
4 , and CO2 ), five forms
of biomass (aerobes, denitrifiers, iron reducers, sulphate reducers, and methanogens), four types of corrosion product (FeOOH,
FeCO3 , Fe3O4 , and FeS), and water. <strong>The</strong> code includes the possibility of the limitation of both microbial and corrosion reactions
by the availability of water.
4) CURING TIME EFFECT ON THE FRACTION OF 137CS FROM IMMOBILIZED
RADIOACTIVE EVAPORATOR SLUDGE BY CEMENT - 16329
Ilija Plecas, Slavko Dimovic, Vinca Institute (Serbia)
Traditional methods of processing evaporator concentrates from NPP are evaporation and cementation.<strong>The</strong>se methods allow to
transform a liquid radioactive waste into the rather inert form, suitable for a final disposal. To assess the safety for disposal of
radioactive mortar-waste composition, the leaching of 137Cs from immobilized radioactive evaporator concentrate into a surrounding
fluid has been studied. Leaching tests were carried out in accordance with a method recommended by IAEA. Curing conditions
and curing time prior to commencing the leaching test are critically important in leach studies since the extent of hydration of the
cement materials determines how much hydration product develops and whether it is available to block the pore network, thereby
reducing leaching. Incremental leaching rates Rn (cm/d) of 137Cs from evaporator concentrates after 180 days were measured. <strong>The</strong>
results presented in this paper are examples of results obtained in a 20-year concrete testing project which will influence the design
of the engineer trenches system for future central Serbian radioactive waste storing center.
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