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Biodegradability of Different Size Classes of Bleached Kraft Pulp Mill Effluent Organic Halogens During Wastewater Treatment and in Lake Environments
Published in Mark R. Servos, Kelly R. Munkittrick, John H. Carey, Glen J. Van Der Kraak, and PAPER MILL EFFLUENTS, 2020
E.K. Saski, J.K. Jokela, M.S. Salkinoja-Salonen
The microcoulometric analyzer used as the chlorine detector of the HPLC chromatographic fractions in the above studies is halogen specific rather than chlorine specific. It also may give (although to our experience, rarely) false positive reponses if the studied sample contains nitrocompounds. We used neutron activation analysis (chlorine specific) to calibrate for the mass balance (solvent extracts of organohalogens), but the sensitivity of this method is too low to allow for measuring the chlorine contents of chromatographic fractions. In this paper we describe confirmatory results obtained using radiolabeled chlorine (36C12) as the chlorine indicator. This is a direct chlorine-specific method. Kraft pulp was bleached with 36C12, inorganic chloride removed and the molecular weight distribution of the radiochlorinated organic fraction was analyzed by the same HPLC column and eluent system as before. Figure 2 shows the result: also in this case the major part of the molecules were of sizes ranging from 200 to 2000 g mol−1. We therefore conclude that the molecular size of solvent soluble chlorolignin is in this range.
Soil-Water Budget
Published in Daniel B. Stephens, Andrea J. Kron, Andrea Kron, Vadose Zone Hydrology, 2018
Daniel B. Stephens, Andrea J. Kron, Andrea Kron
Based on its long half-life, chlorine-36 is potentially useful to date groundwater as old as about 2 million years. In many respects, chlorine-36 is an ideal tracer for dating old groundwater. Unlike carbon-14, chlorine-36 does not interact appreciably with most aquifers, although dead chloride can be dissolved from some salt-bearing natural formations to increase the apparent groundwater age. In clay-rich deposits the anion exclusion process may cause chloride ions to migrate slightly faster than the water. Chlorine-36 is readily detected in very small concentrations by a tandem accelerator-mass spectrometer, but this equipment is available for commercial use at only a few research institutions. The ratio of chlorine-36 to stable chloride is used to determine the groundwater age from Equation 23. This method has been applied to date groundwater in Canada (Phillips et al., 1986) and Australia (Bentley et al., 1986).
Simulating Properties of Canadian Research Reactor Fuels Important to Disposal
Published in Nuclear Science and Engineering, 2023
Aaron Barry, Markus H. A. Piro
Carbon-14 and chlorine-36 are other long-lived radionuclides important to disposal. When impurities are ignored (the effect of impurities is described in Sec. IV.G), no 36Cl generation was simulated above the selected cutoff value of 1E-12% mass. This is because 36Cl generation is driven by neutron activation of 35Cl. In the selected fuels, 14C was only observed in the CANDU, SLOWOKE, and WR-1 fuel, as they contained oxygen and carbon in their fuel chemical forms. In thermal neutron fluxes, 14C generation is driven by neutron activation of 13C and neutron capture and alpha decay of 17O. In fast neutron fluxes, it is driven by neutron capture and proton emission of 14N and neutron capture and 3He emission of 16O. The concentrations of 14C when impurities are ignored is shown in Fig. 8. From Fig. 8, it is apparent that UO2 CANDU fuel generates a higher concentration of 14C than UC WR-1 fuel when impurities are ignored, even though both have similar burnups.
Predictive Modeling of a Simple Field Matrix Diffusion Experiment Addressing Radionuclide Transport in Fractured Rock. Is It So Straightforward?
Published in Nuclear Technology, 2022
J. M. Soler, I. Neretnieks, L. Moreno, L. Liu, S. Meng, U. Svensson, A. Iraola, H. Ebrahimi, P. Trinchero, J. Molinero, P. Vidstrand, G. Deissmann, J. Říha, M. Hokr, A. Vetešník, D. Vopálka, L. Gvoždík, M. Polák, D. Trpkošová, V. Havlová, D.-K. Park, S.-H. Ji, Y. Tachi, T. Ito, B. Gylling, G. W. Lanyon
In the framework of the deep geological disposal of radioactive waste in fractured crystalline rocks, the diffusion of radionuclides from water-conducting fractures into the stagnant porewater of the adjacent wall rock, known as matrix diffusion (MD), combined with sorption in the rock matrix are the main retardation mechanisms for the radionuclides once they may have eventually been released from their disposal canisters and surrounding engineering barriers (e.g., cementitious or compacted bentonite backfills). Numerous field and laboratory experiments studying MD have been interpreted using mathematical solute transport models, including advection and dispersion (AD) in the fractures and diffusion and retention (sorption) in the rock matrix.1–9 However, the predictive capability of these models is difficult to quantify, especially in relation to the different concepts used in the models and their translation into effective transport and retention parameters. With this idea in mind, a purely predictive modeling exercise was designed within the SKB GroundWater Flow and Transport of Solutes (GWFTS) Task Force.awww.skb.se/taskforce. This Task Force is an international forum in the area of conceptual and numerical modeling of groundwater flow and solute transport in fractured rocks. Task 9 within the Task Force addresses the modeling of coupled MD and sorption in heterogeneous crystalline rock matrix at depth, which is performed in the context of in situ diffusion experiments at the ONKALO underground rock research facility (Finland) and at the Äspö Hard Rock Laboratory (Sweden). The modeling exercise described here (Task 9A) was designed for modeling teams to make predictive calculations of tracer breakthrough curves in the Water Phase Diffusion Experiments10,11 (WPDE-1 and WPDE-2) at ONKALO. These were field solute transport experiments in veined gneiss (VGN) subject to a simple well-characterized geometry. Synthetic groundwater containing several conservative and sorbing radiotracers (tracer pulses) was injected at one end of a borehole interval (Fig. 1). Hydrogen-3 [as trititiated water (HTO)], chlorine-36, and sodium-22 were used as tracers in both experiments. Additionally, 85Sr and 133Ba were injected in the WPDE-2. The injected water flowed along the annulus (slot aperture 1.25 mm) between an inner polyether ether ketone (PEEK) dummy and the borehole wall, simulating an open fracture in the rock. Tracers were able to diffuse into and out of the rock matrix around the borehole. Flow rates were 20.1 μL/min (48.7 m/year, WPDE-1) and 10.0 μL/min (24.2 m/year, WPDE-2). The main goal of this modeling exercise was the comparison of different predictive calculations and the analysis of the possible differences between the different sets of results. The discussion of the experimental results and their interpretation10,11 were not part of the modeling exercise and are not addressed here. However, the measured breakthrough curves are also reported and compared with the predictions.