Abstract
Graphite material is extremely undissolvable to be turned into chemical solutions, therefore sample preparation is a serious problem faced in the determination of elemental impurity content in a graphite material. In this work, The nondestructive approach of instrumental neutron activation analysis (INAA) is applied to determine the concentration of multi-element in a graphite material, by employing both the forth floating process and the acid treatment method to the local Indonesian graphite. The sample was irradiated in the Rabbit system of G.A. Sywabessy Multi-Purpose Reactor at Serpong, Indonesia. The precision of the analysis was evaluated using certified reference materials which were obtained good performance with the most of concentration value in the range of 3 < zheta score < -3. Eleven elemental (Al, Sb, Co, Cu, La, Mn, Sc, Na, W, V, and Zn) concentration were determined in the forth floating process of the graphite. The Cu elemental is the most content with the value of 60,8 mg/kg or about 90% of total concentration content in graphite. Followed by the Sb content with a value of 5,5 mg/kg (about 8% of total impurities content in graphite). The remaining 2% includes the intermediate and the minor content of other impurity elements. After the acid treatment, the total concentration of impurities contained in the graphite material drastically decreases from 6.7% w/w to about 0,1; 0.6; and 0.59 % w/w for treatment employing the HF,  HNO3+H2SO4,and HF+HCl+H2SO4 acid reagent, respectively. Cu element makes the largest contribution to reduce the concentration of impurities in graphite which decreased from 60,675 mg/kg to 1,088 mg/kg; 925 mg/kg and 835 mg/kg for HF, HNO3+H2SO4 and HF+HCl+H2SO4 acid reagent, respectively. In addition, Sb element concentration dropped dramatically from 5,514 mg/kg to 93 mg/kg using HF reagents. The other trace elements (As, Ba, Ca, Ce, Eu, Fe, Mg, Sm, and Th) were also identified in the acid reagent treated graphite sample which are suspected to derivates from the impurity reagent and or from contamination during the sample preparation. The treated HF for graphite was obtained the low purity grades approach for nuclear graphite.
Highlights
Graphite which is a naturally occurring crystal carbon polymorphs is composed of a series of stacked parallel layer planes of the carbon structure
The total concentration of impurities contained in the graphite material drastically decreases from 6.7% w/w to about 0,1; 0.6; and 0.59 % w/w for treatment employing the HF, HNO3+H2SO4,and HF+HCl+H2SO4 acid reagent, respectively
Graphite was used in structural components supporting the reactor core in the Advanced Gas-cooled Reactors (AGRs) and High-Temperature Gas-cooled Reactors (HTGRs) as moderator, reflector and fuel matrix (Zhou et al 2017)
Summary
Graphite which is a naturally occurring crystal carbon polymorphs is composed of a series of stacked parallel layer planes of the carbon structure. Graphite has been widely used in many application in various fields, such as metallurgy and semiconductor process, electrical, automobile industry, alkaline batteries, electric conductors and industry electrodes (Pierson 1993). Graphite has good mechanical performances, thermal properties, resistant to irradiation and chemical attack, making it an excellent material for advanced application such as nuclear structural components. Graphite was used in structural components supporting the reactor core in the Advanced Gas-cooled Reactors (AGRs) and High-Temperature Gas-cooled Reactors (HTGRs) as moderator, reflector and fuel matrix (Zhou et al 2017). Information concerning the content of trace elements in graphite is very important to evaluate its suitability in the application. High purity graphite was needed for nuclear applications and semiconductor components. Some contaminants even at trace element contents could have a negative effect on its application (Pierson 1993).
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