Fuel Chemistry Division, BARC, Mumbai.
Dr. N. Kumar joined Bhabha Atomic Research Centre (BARC) in 1981 after graduating from Poona University in 1980. Since his joining, he has been actively involved with the development of processes for the fabrication of ceramic nuclear fuels for Indian Nuclear Reactors. He was awarded Ph.D. degree from University of Mumbai for his work on "Ceramic Nuclear Fuel Preparation" in 2006. Dr. Kumar has a number of publications both in Indian as well as International journals. Recently, he has coauthored a book entitled " Thoria Based Nuclear Fuels" published by the famous International Publisher "Springer". Dr. Kumar was bestowed with FCD Analytical Scientist of the year award (2009), DAE Group Achievement Awards (2013 and 2015). Presently, he is the Head, Actinides Recovery & Engineering Services Section, of Fuel Chemistry Division, BARC.
Title: FUEL FOR INDIAN NUCLEAR REACTORS
India occupies an important place among the Asian countries in the indigenous design, development, construction, and operation of nuclear power reactors. India's nuclear power generation is a three-stage program which ultimately aims to make use of the abundant resources of thorium. The development of a successful nuclear fuel is one of the important requirements for any nuclear power program. Nuclear fuel could be broadly classified as metallic fuel and ceramic fuel. The most commercially used power reactor fuel is the ceramic fuel. India, has mastered the technology of fabricating ceramic oxide fuels for all its power reactors. The primary requirement for any nuclear fuel is it should maintain its dimensions within the specified tolerances, while delivering power at a specified rate. The fuel should have a relatively simple, economic and safe fabrication and reprocessing routes. In India, metallic fuel is used in research reactors and ceramic fuel is used in power reactors. Ceramic fuel can be an oxide, a carbide or nitride. India uses Natural uranium oxide in the form of cylindrical pellets in all its power reactors due to its simple and easy fabricating routes, good compatibility with the clad and a relatively high melting point. Natural uranium mainly consists of 238U with 0.72% of 235U, which is the fissile isotope.
The preparation of ceramic oxide fuel involves the conversion of the nitrate solutions of uranium to its oxide. The oxide powder thus formed is converted to oxide pellets of desired dimension and density by the well-established powder oxide pellet (POP) route. Sol-gel process, an alternative to the conventional route has been developed during the past few decades in BARC for the preparation of oxides and carbides. The advantage of sol-gel process is its ability to combine the conversion and consolidation steps, since the gel microspheres are directly obtained from metal nitrate solutions.
The microspheres obtained from this process can be packed by vibration (vipac) and can be used as fuel. Alternatively, the resulting microspheres could be made soft by suitably modifying the process conditions and heat treatment parameters to obtain soft microspheres which could be directly compacted into green pellets. This technique is referred to as sol-gel microsphere pelletization technique (SGMP).