Talanta 52 (2000) 885–892 Conductometric determination of carbon in uranium carbide and its solution in nitric acid M.K. Ahmed a, *, R. Geetha a , N.K. Pandey a , S. Murugesan a , S.B. Koganti a , B. Saha b , P. Sahoo b , M.K. Sundararajan b a Reprocessing Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603 102 Tamil Nadu, India b Ultra Sensitie Deices and Techniques Section, SHINE Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603 102 Tamil Nadu, India Received 6 December 1999; received in revised form 3 May 2000; accepted 11 May 2000 Abstract A simple but accurate method has been developed for the determination of carbon in uranium carbide powders/pel- lets as well as in solutions of uranyl nitrates. The methodology involves quantitative conversion of carbon present in the sample to carbon dioxide that is subsequently absorbed in a dilute solution of barium hydroxide. The conductivity shift of the barium hydroxide solution is monitored on-line continuously using a laboratory-built PC-based conductivity measurement system that has been developed in-house based on the direct conversion of conductance to the digital pulse frequency. A new gas absorption cell has been designed to ensure quantitative absorption during the residence time of the gas in the cell. The method is sensitive, accurate and precise to 1–3% at 600–1000 g of carbon in samples of uranium carbide. © 2000 Elsevier Science B.V. All rights reserved. Keywords: Carbon determination; Uranium carbide; Dissolver solution; Digital conductometry; Online monitoring www.elsevier.com/locate/talanta 1. Introduction Mixed carbide of uranium and plutonium of composition 70% PuC and 30% UC is used as fuel for the first time in the fast breeder test reactor (FBTR) at Kalpakkam [1]. Mixed carbide is cho- sen because of its certain advantageous properties such as higher heavy atom density, better thermal conductivity and high specific power [2]. While reprocessing this fuel after irradiation, it is first dissolved in nitric acid and then extracted into 30% TBP in n-dodecane for separation of fuel components (uranium and plutonium). During its dissolution, a portion of carbon (30 – 50%) present in the fuel is converted to carbon dioxide and the rest remains in the solution as a host of soluble organic compounds such as oxalic acid, mellitic acid, etc. These compounds have to be destroyed completely before the solvent extraction step, since the presence of the organic species leads to losses of plutonium due to the formation of com- plexes with these ligands [3]. Chemical as well as electrochemical methods are available for the de- * Corresponding author. Fax: +91-4114-40207. E-mail address: ahmed@igcar.ernet.in (M.K. Ahmed). 0039-9140/00/$ - see front matter © 2000 Elsevier Science B.V. All rights reserved. PII:S0039-9140(00)00442-2