Quantification of Trace and Ultra-trace Elements in Nuclear Grade Manufactured Graphites by Fast-Flow Glow Discharge Mas
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1215-V16-09
Quantification of Trace and Ultra-trace Elements in Nuclear Grade Manufactured Graphites by Fast-Flow Glow Discharge Mass Spectrometry and by Inductively Coupled Plasma – Mass Spectrometry after Microwave – Induced Combustion Digestions Xinwei Wang, Gaurav Bhagat, Kevin O’Brien and Karol Putyera Evans Analytical Group - New York, 6707 Brooklawn Parkway, Syracuse, NY 13211, U.S.A ABSTRACT Fast-Flow Glow Discharge Mass Spectrometry (FF-GDMS) and Inductively Coupled Plasma – Mass Spectrometry after Microwave – Induced Combustion Digestions (MIC-ICP-MS) methods were developed for the determination of mg/kg- and µg/kg-level B, Mg, Al, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Sb, W and Pb in nuclear-grade graphite. Consistent results have been achieved in determining trace elements like B, Ti, Cr, Mn, Zr, Sb and Pb by both methods, which vary mostly less than ±30%, and are in line with the manufacturer reference values. On Mg, Al, Fe, Co, Zn, Mo and W, FF-GDMS analyses also show good agreement with the manufacturer’s data. Continuing efforts in identifying source of interference, which has limited the MIC-ICP-MS analysis of these elements, is currently underway. INTRODUCTION “Nuclear”-grade graphite is the core structural material for the high-temperature gas-cooled (usually helium) reactor systems. Its performance and lifetime not only are closely related to the irradiation environment but also are dramatically affected by the specifics of the particular graphite: manufacturing process, graphitization temperature, composition (amount of coke, filler, etc., depending on where it was mined), and so on[1]. It is well documented that chemical and elemental impurities catalyse variety of reactions in graphite. The nuclear industry has come to realization that specific elemental impurities, even at trace levels (mass fractions on the mg/kg levels) could lead to damage of the structural integrity and thus affecting the long-term performance of graphite-made components[2,3]. For example, trace elements, such as Fe, Ni and Al accelerate the corrosion of graphite; Fe, Al, Cu and Ca promote thermal and radiolytic oxidation at the presence of trace CO2/CO in helium or in the event of air/water ingression [4]; B, Si and Ti enhance the sublimation of graphite [5]; B, Gd, Sm and Cd capture neutrons [6,7], whereas Li, Si, Al and others form undesirable artificial radioactive isotopes. There are suggested limits of elemental impurities identified in ASTM D7219, which are detrimental for isotropic & near-isotropic nuclear graphite (Table I). These impurities may originate from the precursors (e.g., coke, pitch, synthetic polymers), and/or be introduced either during graphitization processes and/or in the post-graphitization processes. Great efforts have been made on development of analytical protocols for measuring trace level concentrations in graphite [8], much of which were directed on solid sampling methods, like laser ablation inductively coupled plasma-atomic emission spectroscopy [9], solid sampling electrotherma
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