Yuan Qian

Source Apportionment of Carbonaceous Particulate Matter in a Shanghai Suburb Based on Carbon Isotope Composition

In this article, a new approach was established to estimate the fractional contributions of soil dust, biomass burning, biogenic emissions, coal burning, and vehicle exhaust to the carbonaceous particulate matter by carbon isotope and linear regression techniques of OC-K+ (organic carbon) and OC-EC (elemental carbon). Using the method described herein, the fractional distributions of these sources were quantitatively determined for the OC and semiquantitatively for the EC in the size-resolved particles (size ranges: <0.49, 0.49–0.95, 0.95–1.5, 1.5–3.0, 3.0–7.2, and >7.2 μm) collected in Jiading District, a suburb of Shanghai, China. Distinct size distribution of contributions of these sources to the OC and EC was observed. Generally, biomass burning contributed a large fraction to OC in the smaller particles and biogenic emissions shared a bigger fraction to OC in the larger particles. Soil dust made contributions solely to the OC, for no EC fraction was found in the soil dust. OC from coal burning concentrated in the fine particles (smaller than 3.0 μm), and that from vehicle exhaust exhibited bimodal distribution, with peaks for both fine and coarse particles. The fossil sources dominated EC in almost all the size ranges. Though a few deviations are brought about in the calculation, this approach provides an effective way to distinguish the sources of the carbonaceous particulate matter. Copyright 2013 American Association for Aerosol Research

Development of the Tritium Transport Analysis Code for the Thorium-Based Molten Salt Reactor

Abstract The Thorium-Based Molten Salt Reactor (TMSR) has been highlighted for its safety, economy, and nuclear nonproliferation. A program for developing the TMSR system has been launched in Shanghai Institute of Applied Physics, Chinese Academy of Sciences. In the TMSR system, mixtures of LiF and BeF2, termed FLiBe, are proposed and used as the primary coolant salt, in which tritium is produced mainly by the neutron reactions of lithium. In the TMSR system, at high temperatures, tritium can permeate through metal walls to the surroundings, leading to a potential radiological hazard. Thus, tritium control becomes a major problem hindering the development of the TMSR system. Evaluation of the tritium distribution is necessary for tritium control in the TMSR system. In this study, the Tritium Transport Analysis Code (TTAC) has been developed for simulating the tritium behaviors in the TMSR system (hence, the code TMSR-TTAC), such as tritium chemical forms in coolant salts, tritium transport behaviors, and tritium distribution in the system. The model code is developed by the MATLAB/SIMULINK package, and it is based on the mass balance equations of the tritium-containing species and hydrogen. TMSR-TTAC is benchmarked with the molten salt reactor model, which is based on Molten Salt Reactor Experiment designs. The results show that TMSR-TTAC has the ability to calculate the tritium distribution in the TMSR system.

Tritium Transport Analysis in a 2-MW Liquid-Fueled Molten Salt Experimental Reactor with the Code TMSR-TTAC

Abstract In the Thorium-Based Molten Salt Reactor (TMSR), tritium is produced at a high rate, which results in huge difficulties regarding tritium control. Tritium distributions in a 2-MW liquid-fueled molten salt experimental reactor (TMSR-LF1) were simulated with the TMSR–Tritium Transport Analysis Code (TTAC) (TMSR-TTAC) that was developed for analysis of tritium behaviors in the TMSR. The simulation for normal operation showed that about 60% of the tritium would permeate through the metal walls of the system, 25% of the tritium was removed by the purge gas system, and 15% of the tritium was absorbed on the core graphite. In addition, the effects on tritium distribution of the chemical-redox potential in fuel salt, the tritium permeation behavior through the metal walls, and various tritium removal methods in the TMSR-LF1 have also been simulated. The simulation results based on those conditions are analyzed in this paper to improve the knowledge of tritium behavior in the TMSR-LF1 and to provide reliable methods and strategies for tritium control in the TMSR system.

Determination of the Mercury Isotopic Ratio by Cold Vapor Generation Sector Field–Inductively Coupled Plasma–Mass Spectrometry Using Lead as the Internal Standard

ABSTRACT Lead was applied as an internal standard for the determination of Hg isotopic ratios. Cold vapor generation (CV) coupled with sector field–inductively coupled plasma–mass spectrometry (CV-SF-ICP-MS) was used for determination of Hg. It was effective to avoid interferences of Pb from samples while improving the sensitivity of Hg isotopic analysis by an approximate factor of 45 times higher than the aerosol mode. CV-SF-ICP-MS system was constructed and operational parameters were optimized. Research showed that the long stability of the system was limited by SF-ICP-MS and had no relationship with CV under the optimized conditions. The optimized precision of Hg isotopic ratio analysis was approximately 0.1% during 4 h. Five models were applied for the mass bias correction and the Baxter model obtained the smallest relative difference, 0.52‰. The results showed that the mean value of NIST SRM 3133 Hg isotopic ratios obtained by Pb internal standard was nearly identical with the value for Tl. The same performance was also obtained in two environmental reference materials. The results show that Pb may be used as the internal standard for determination of Hg isotopic ratio instead of Tl.