The 13th International Conference on Environmental ... - Events

Abstracts
determined concentration of Sn-126 was equivalent to 60% of that obtained by ORIGEN2 calculation, which suggests
that a part of Sn initially existed in the sample UO2 pellet precipitated as insoluble residue during the dissolution process.
18) 40103 – Selective Uptake of Palladium from High-Level Liquid Wastes by Hybrid Microcapsules
Hitoshi Mimura, Takashi Sakakibara, Yan Wu, Yuichi Niibori, Tohoku Univ. (Japan);
Shin-ichi Koyama, Takashi Ohnishi, JAEA (Japan)
Fine crystalline powders of KCuFC were immobilized with alginate gel polymers by sol-gel methods. <strong>The</strong> uptake
properties of KCuFC-microcapsules (KCuFC-MC) were examined by batch and column methods. <strong>The</strong> size of
KCuFC-MC particle was estimated to be about 1 mm in diameter, and KCuFC powders were uniformly dispersed in
KCuFC-MC particles. <strong>The</strong> uptake rate of Pd2+ for KCuFC-MC was attained within 3 d, and the uptake of Pd2+ was
found to be independent of the temperature and coexisting HNO3 concentration. As for the breakthrough properties of
Pd2+ through a column packed with KCuFC-MC, a breakpoint of 5% breakthrough was enhanced with lowering of flow
rate and independent of coexisting HNO3 concentration. <strong>The</strong> Pd2+ ions were selectively adsorbed in the KCuFC crystal
phase, while other metal ions such as Ru(NO)3+ and ZrO2+ were absorbed in the alginate phase. High uptake percentage
of 98.6% was obtained by using the dissolved solutions of spent fuel from FBR-JOYO (119 GWd/t, JAEA). <strong>The</strong> alginate
film enclosing KZnFC was further prepared by using the support of cellulose filter paper, where the Pd2+ ions were
selectively adsorbed on the KZnFC-MC film. <strong>The</strong> alginate film enclosing insoluble ferrocyanides are predicted for the
selective separation of Pd2+ as an ion-exchange filter. Thus, the microcapsules enclosing insoluble ferrocyanides are
effective for the selective separation of Pd2+ from high-level liquid waste (HLLW).
19) 40113 – An Empirical Model To Determine <strong>The</strong> Modes Of Corrosion Of Carbon Steel
Toshikatsu Maeda, Masatoshi Watanabe, Seiji Takeda, Shinichi Nakayama, JAEA (Japan)
Carbon steel is a candidate material for overpack of high-level radioactive waste disposal in Japan. One of its
expected functions is to avoid groundwater from contacting with vitrified waste form. <strong>The</strong> corrosion rate is a determining
factor for the overpack lifetime, and it is highly dependent on the mode of corrosion. Carbon steel is an alloy that could
be attacked by localized corrosion in the form of pitting corrosion or crevice corrosion under certain water chemistries.
For example, it is known that carbon steel is passivated in solutions above a limiting pH; pH that is referred to as the
general corrosion/passivation transition pH and is denoted as pHd. Carbon steel corrosion rates depend on the mode of
corrosion (general or local corrosion), which is determined by the pHd value. Predicting the pHd for carbon steel in near
field environments is essential to evaluate the expected lifetime of overpacks, especially considering the possibility of
highly alkaline environments induced by cementitious materials in the disposal facility. In this study, an empirical model
was developed to determine whether near field environments fall in the passivation or non-passivation domain for carbon
steel. Using the experimental data obtained by previous studies, the pHd was defined as a function of four factors shown
in equation (1), where the activity of proton ion ([H+]) for pHd is assumed to be a linear combination of the logarithms of
the total carbonate concentration (C total), the chloride ion concentration (Cl-), and the limiting current density of
dissolved oxygen diffusion (iO2), and the inverse of absolute temperature of contacting solution (T). <strong>The</strong> derived
equation fitted well experimental data from previous studies.
20) 40124 – Trends in Scenario Development Methodologies and Integration in NUMO's Approach
Takeshi Ebashi, Katsuhiko Ishiguro,NUMO (Japan); Keiichiro Wakasugi, JAEA (Japan);
Hideki Kawamura, Obayashi Corporation (Japan);
Irina Gaus, Stratis Vomvoris, Andrew Martin, Nagra (Switzerland);
Paul Smith, Safety Assessment Management (UK)
<strong>The</strong> development of scenarios for quantitative or qualitative analysis is a key element of the assessment of the safety
of geological disposal systems. As an outcome of an international workshop attended by European and the Japanese
implementers, a number of features common to current methodologies could be identified, as well as trends in their
evolution over time. In the late nineties, scenario development was often described as a bottom-up process, whereby
scenarios were said to be developed in essence from FEP databases. Nowadays, it is recognised that, in practice, the
approaches actually adopted are better described as top-down or "hybrid", taking as their starting point an integrated
(top-down) understanding of the system under consideration including uncertainties in initial state, sometimes assisted by
the development of "storyboards". A bottom-up element remains (hence the term "hybrid") to the extent that FEP
databases or FEP catalogues (including interactions) are still used, but the focus is generally on completeness checking,
which occurs parallel to the main assessment process. Recent advances focus on the consistent treatment of uncertainties
throughout the safety assessment and on the integration of operational safety and long term safety.
108