BARC/2012/E/001 BARC/2012/E/001 COULOMETRY FOR THE DETERMINATION OF URANIUM AND PLUTONIUM: PAST AND PRESENT by M.K. Sharma, J.V. Kamat, A.S. Ambolikar, J.S. Pillai and S.K. Aggarwal Fuel Chemistry Division 2012 BARC/2012/E/001 GOVERNMENT OF INDIA ATOMIC ENERGY COMMISSION BARC/2012/E/001 COULOMETRY FOR THE DETERMINATION OF URANIUM AND PLUTONIUM: PAST AND PRESENT by M.K. Sharma, J.V. Kamat, A.S. Ambolikar, J.S. Pillai and S.K. Aggarwal Fuel Chemistry Division BHABHA ATOMIC RESEARCH CENTRE MUMBAI, INDIA 2012 BARC/2012/E/001 BIBLIOGRAPHIC DESCRIPTION SHEET FOR TECHNICAL REPORT (as per IS : 9400 - 1980) 01 Security classification : Unclassified 02 Distribution : External 03 Report status : New 04 Series : BARC External 05 Report type : Technical Report 06 Report No. : BARC/2012/E/001 07 Part No. or Volume No. : 08 Contract No. : 10 Title and subtitle : Coulometry for the determination of uranium and plutonium: past and present 11 Collation : 34 p., 2 figs., 7 tabs. 13 Project No. : 20 Personal author(s) : M.K. Sharma; J.V. Kamat; A.S. Ambolikar; J.S. Pillai; S.K. Aggarwal 21 Affiliation of author(s) : Fuel Chemistry Division, Bhabha Atomic Research Centre, Mumbai 22 Corporate author(s) : Bhabha Atomic Research Centre, Mumbai - 400 085 23 Originating unit : Fuel Chemistry Division, BARC, Mumbai 24 Sponsor(s) Name : Department of Atomic Energy Type : Government Contd... BARC/2012/E/001 30 Date of submission : December 2011 31 Publication/Issue date : January 2012 40 Publisher/Distributor : Head, Scientific Information Resource Division, Bhabha Atomic Research Centre, Mumbai 42 Form of distribution : Hard copy 50 Language of text : English 51 Language of summary : English, Hindi 52 No. of references : 55 refs. 53 Gives data on : 60 Abstract : Precise and accurate determination of uranium (U) and plutonium (Pu) in nuclear fuels is an essential requirement in nuclear fuel cycle for chemical quality assurance of these materials. The redox based electroanalytical methods viz. Potentiometry and Biamperometry are capable of meeting the requirements of high accuracy and precision using milligram amounts of the analyte. However, use of chemical reagents to perform redox reactions in these methods, generates radioactive liquid waste which needs to be processed to recover plutonium. The analytical waste generated by the controlled-potential coulometric (CPC) method is clean as the change in the oxidation state of the analyte is done by the electrolytic reaction. Therefore, the determination of U and Pu in nuclear fuel materials by controlled-potential coulometry is an attractive option instead of biamperometry and potentiometry. In this report, the work carried out to develop CPC employing indigenous coulometers is discussed. The coulometric results for both U and Pu using indigenous coulometers agreed within ± 0.2% with the biamperometric values. The results indicate that indigenous coulometers are suitable for U and Pu determination in nuclear fuel materials and the CPC method can be employed for nuclear fuel samples. 70 Keywords/Descriptors : VOLTAMETRY; URANIUM OXIDES; FUEL CYCLE; PLUTONIUM OXIDES; QUANTITATIVE CHEMICAL ANALYSIS; REDOX PROCESS; RADIOACTIVE EFFLUENTS; QUALITY ASSURANCE 71 INIS Subject Category : S11 99 Supplementary elements : Coulometry for the Determination of Uranium and Plutonium: Past and Present 1 Contents Sr. No. Title Page No. ABSTRACT 1. INTRODUCTION 2. TECHNIQUES AND INSTRUMENTATION 2.1 Galvanostatic or constant-current coulometry 2.2 Potentiostatic or controlled-potential coulometry 3. DETERMINATION OF URANIUM 3.1. Coulometric Titration of Uranium 3.2. Controlled-Potential Coulometry of Uranium at Mercury Pool Working Electrode 3.2.1. International Laboratories 3.2.2. Fuel Chemistry Division, BARC 3.3. Controlled-Potential Coulometry of Uranium at Solid Working Electrode 3.3.1. International Laboratories 3.3.2. Fuel Chemistry Division, BARC 3.4. Development and Performance Evaluation of Indigenous Controlled-Potential Coulometer 4. DETERMINATION OF PLUTONIUM 4.1. Coulometric Titration of Plutonium 4.2. Controlled-Potential Coulometry of Plutonium 4.2.1. International Laboratories 4.2.2. Fuel Chemistry Division, BARC 4+ 3+ 2+ + 5. INVESTIGATIONS ON REDOX BEHAVIOUR OF Pu /Pu and UO2 /UO2 REDOX COUPLES ON NANOPARTICLES MODIFIED ELECTRODES ACKNOWLEDGEMENTS REFERENCES Figures Fig. 1 Controlled-potential coulometric setup Fig. 2 Coulogram for determining the working electrode potential for irreversible redox couple Tables Table 1. Multiple oxidation states of uranium in aqueous solution Table 2. Redox potentials of various redox couples of uranium Table 3. The E0’ values for Pu (IV)/Pu (III) and Fe (III)/Fe (II) in various acids Table 4. Determination of Pu in chemical assay standard [K4Pu (SO4)4] by controlled-potential coulometry in two different supporting electrolytes Table 5. Determination of Pu in alloy samples by controlled potential coulometry Table 6. Determination of Pu in (Pu, U) mixed carbide samples by controlled potential coulometry Table 7. Results of the paired t-test for the data obtained by the two methodologies ÃÖÖ¸üÖÓ¿Ö −ÖÖ׳ÖúßμÖ ‡ÔÓ¬Ö−ÖÖêÓ ´Öë μÖæ¸êü×−ÖμÖ´Ö (U) †Öî¸ü ¯»Öæ™üÖê×−ÖμÖ´Ö (Pu) úÖ ÃÖÆüß ×−Ö¬ÖÖÔ¸üÖ, −ÖÖ׳ÖúßμÖ ‡ÓÔ¬Ö−Ö “ÖÎú ´Öë ‡−Ö ÃÖÖ´Ö×ÖÏμÖÖë úß ¸üÖÃÖÖμÖ×−Öú ÖãÖ¾Ö¢ÖÖ †ÖÀ¾ÖÖÃÖ−Ö êú ×»Ö‹ †ŸμÖÓŸÖ †Ö¾Ö¿μÖú Æîü… ¸êü›üòÖŒÃÖ †Ö¬ÖÖ׸üŸÖ ¾ÖîªãŸÖ ¾Öî¿»Öê×ÂÖú ¯Ö¨üןÖμÖÖë •ÖîÃÖê ¯ÖÖê™ëü׿ֆÖê×´Ö×ŸÖ †Öî¸ü ²ÖÖ‡ÔüÛ´¯Ö¸üÖê×´Ö×ŸÖ †Ö¾Ö׬Öú ¯Ö׸ü¿Ö㨟ÖÖ †Öî¸ü ÃÖãÖ´ÖŸÖÖü úß †Ö¾Ö¿μÖúŸÖÖ†Öë úÖê ¯Ö¨üןÖμÖÖë ‹−ÖÖ»ÖÖ‡™ü úß ü ×´Ö×»ÖÖÏÖ´Ö ´ÖÖ¡ÖÖ úÖ ¯ÖÏμÖÖêÖ ú¸üŸÖê Æãü‹ ¯Öæ¸üÖ ú¸ü ÃÖúŸÖê Æïü… ÆüÖ»ÖÖÓ×ú ‡−Ö ¯Ö¨üןÖμÖÖë ´Öë ¸êü›üÖòŒÃÖ †×³Ö×ÎúμÖÖ ú¸ü−Öê êú ×»Ö‹ ¸üÖÃÖÖμÖ×−Öú †×³ÖúÖ¸üúÖë êú ¯ÖÏμÖÖêÖ ÃÖêê ¸êü×›üμÖÖêÃÖ×ÎúμÖ ¦ü¾Ö †¯Ö׿Ö™ü ×−Öú»ÖŸÖÖ Æîü וÖÃÖê ¯»Öæ™üÖê×−ÖμÖ´Ö ×−ÖúÖ»Öê •ÖÖ−Öê ÆêüŸÖã ¯ÖÏÖêÃÖêÃÖ ×ú‹ •ÖÖ−Öê úß †Ö¾Ö¿μÖúŸÖÖ Æîü… ×−ÖμÖÓס֟Ö-¯ÖÖêê™êü−Ö׿ÖμÖ»Ö úæ»ÖÖò×´Ö×ŸÖ (CPC) ¯Ö¨ü×ŸÖ «üÖ¸üÖ ˆŸ¯Ö®Ö ¾Öî¿»Öê×ÂÖú †¯Ö׿Ö™ü þ֓”û Æîü •Ö²Ö ×ú ‡»ÖꌙÒüÖê×»Ö×™üú †×³Ö×ÎúμÖÖ «üÖ¸Ö ‹−ÖÖ»ÖÖ‡™ü úß †ÖŒÃÖß›êü¿Ö−Ö †¾ÖãÖÖü ´Öë ¯Ö׸ü¾ÖŸÖÔ−Ö ÆüÖêŸÖÖ Æîü… †ŸÖ: ×−ÖμÖÓס֟Ö-¯ÖÖê™êü−Ö׿ÖμÖ»Ö úæ»ÖÖò×´Ö×ŸÖ «üÖ¸üÖ −ÖÖ׳ÖúßμÖ ‡ÓÔ¬Ö−Ö ¯Ö¤üÖ£ÖÖí ´ÖêÓ ²ÖÖ‡ÔüÛ´¯Ö¸üÖê×´Ö×ŸÖ †Öî¸ü ¯ÖÖê™êü−Ö׿ֆÖê×´Ö×ŸÖ êú ²Ö•ÖÖ‹ U †Öî¸ü Pu Ö ×−Ö¬ÖÖÔ¸üÖ ‹ú †ÖúÂÖÔú ×¾Öú»¯Ö Æîü… ‡ÃÖ ×¸ü¯ÖÖê™Ôü ´Öë, þ֤êü¿Ö ´Öë ²Ö−Öê Æãü‹ úæ»ÖÖò´Öß™üüÃÖÔ úÖ ¯ÖÏμÖÖêÖ ú¸üŸÖê Æãü‹, CPC úÖ ×¾ÖúÖÃÖ ú¸ü−Öê êú ×»Ö‹ ×ú‹ Ö‹ úÖμÖÔ ¯Ö¸ü “Ö“ÖÖÔ úß Ö‡Ô… þ֤êü¿Öß úæ»ÖÖò´Öß™üüÃÖÔÔ úÖ ¯ÖÏμÖÖêÖ ú¸üŸÖê Æãü‹ U †Öî¸ü Pu ¤üÖê−ÖÖê êú æú»ÖÖò×´ÖןÖú ¯Ö׸üÖÖ´Ö ²ÖÖ‡ÔüÛ´¯Ö¸üÖê×´ÖŸÖßμÖ ´Öæ»μÖ êú ÃÖÖ£Ö 0.2% êú †Ó¤ü¸ü þÖßéúŸÖ Æãü‹… ¯Ö׸üÖÖ´ÖÖë ÃÖê μÖÆü ÃÖæ×“ÖŸÖ ÆüÖêŸÖÖ Æîü ×ú −ÖÖ׳ÖúßμÖ ‡ÔÓ¬Ö−Ö ¯Ö¤üÖ£ÖÖí ´Öë þ֤êü¿Öß úæ»ÖÖò´Öß™ü¸üü U †Öî¸ü Pu êú ×−Ö¬ÖÖÔ¸üÖ êú ×»Ö‹ ˆ¯ÖμÖãŒŸÖ Æîü †Öî¸ü −ÖÖ׳ÖúßμÖ ‡ÔÓ¬Ö−Ö −Ö´Öæ−ÖÖë êú ×»Ö‹ CPC ¯Ö¨ü×ŸÖ úÖ ¯ÖÏμÖÖêÖ ×úμÖÖ •ÖÖ ÃÖúŸÖÖ Æîü… Abstract: Precise and accurate determination of uranium (U) and plutonium (Pu) in nuclear fuels is an essential requirement in nuclear fuel cycle for chemical quality assurance of these materials. The redox based electroanalytical methods viz. Potentiometry and Biamperometry are capable of meeting the requirements of high accuracy and precision using milligram amounts of the analyte. However, use of chemical reagents to perform redox reactions in these methods, generates radioactive liquid waste which needs to be processed to recover plutonium. The analytical waste generated by the controlled-potential coulometric (CPC) method is clean as the change in the oxidation state of the analyte is done by the electrolytic reaction. Therefore, the determination of U and Pu in nuclear fuel materials by controlled-potential coulometry is an attractive option instead of biamperometry and potentiometry. In this report, the work carried out to develop CPC employing indigenous coulometers is discussed. The coulometric results for both U and Pu using indigenous coulometers agreed within ± 0.2 % with the biamperometric values. The results indicate that indigenous coulometers are suitable for U and Pu determination in nuclear fuel materials and the CPC method can be employed for nuclear fuel samples. Keywords: Controlled potential coulometry, Plutonium, Uranium, Pt, Hg, Graphite, Nanoparticles 1. INTRODUCTION Coulometry is based on the measurement of coulombs (unit of electrical charge named in honor of Charles-Augustin de Coulomb) and is the name given collectively to the electrochemical techniques used for quantitative determination of the analyte by measuring the charge consumed/produced when the analyte undergoes reduction/oxidation during exhaustive electrolysis at the large surface area electrode. Fundamental requirement of a coulometric analysis is that the electrode reaction should proceed with 100% current efficiency. Coulometry is an absolute technique since it is based on fundamental physical quantities. Faraday’s first law of electrolysis is used to calculate the amount of analyte where, ‘m’ is the mass of the analyte, ‘M’ is the molar mass of the analyte, ‘F’ (= 96487 C) is the Faraday constant, ‘n’ is the number of electrons change in the redox process, ‘Q’ is the amount of electrical charge consumed/produced, ‘I’ is the current passing through the electrical circuit for time ‘t’. The coulometric techniques can be grouped into two categories: (1) Galvanostatic or constant- current coulometry and (2) Potentiostatic or controlled-potential coulometry (CPC).