Challenges of uranium fuel cycle for expanding nuclear power program

'Full text:' Nuclear power is experiencing a renaissance and stable growth all over the world and is emerging as one of the leading options for meeting the ever increasing demand for electricity, avoiding greenhouse gas emissions and global warming. Presently, some 437 Nuclear Power Reactors are in operation in 30 countries with total installed power of ~370 GWe, generating ~14.5% of global electricity. According to the projection of the International Atomic Energy Agency (IAEA), the installed nuclear power is likely to be in the range of 748 GWe by 2030. Natural Uranium is the basic raw material for nuclear fuel. It contains U235, the only fissile isotope in nature, and U238 which could be transmuted in a reactor to man-made element Plutonium, which has Pu239 and Pu241 fissile isotopes. Light Water Reactor (LWR) system is most common and account for nearly 90% of the operating nuclear power reactors, followed by the Pressurized Heavy Water Reactor(PHWR) system which contribute to some 6% . The LWRs and PHWRs use Low Enriched Uranium (LEU) containing up to 5% U235 and natural uranium (0.7% U235 ) as fuel respectively, in the form of high density uranium oxide pellets. Nuclear power reactor and fuel cycle activities go hand in hand. The front end of uranium fuel cycle consists of exploration and mining of uranium ores, their milling, purification and refining to UO₃, conversion to natural UO₂ powder for fabricating PHWR fuel and to UF₆ followed by U235 enrichment (up to 5%) and conversion to LEU di-oxide powder for LWR fuel. The UO₂ powder is subjected to pelletization, sintering and center less grinding to obtain fuel pellets which are encapsulated in zirconium alloy cladding tubes to form fuel pins that are subsequently clustered to form fuel assemblies. The major challenges in front end of uranium fuel cycle are meeting the growing annual demand of uranium, increasing fuel burn up and ensuring high performance and zero defect of fuel. The once-through 'open' fuel cycle utilizes < 1% of uranium mined for use as nuclear fuel and the rest is locked in tailings of enrichment plant as Depleted Uranium (DU) and in Spent Fuel as Reprocessed Uranium (RU). The back end of nuclear fuel cycle includes the activities related to spent fuel management. Most countries are following a long term interim storage policy. Very few have opted for 'once-through open fuel cycle', where the spent fuel will be treated as waste, stored for several decades, conditioned and finally disposed in repositories. China, France, India, Japan, Republic of Korea and Russia have opted for 'closed nuclear fuel cycle' option, where the spent fuel is subjected to Partitioning and Transmutation (P & T) to recover Pu, RepU and minor actinides (MA : Np, Am & Cm) and recycle them in fast reactor. Thus, more than 60% of the natural uranium resources are utilized and the volume, radio toxicity and decay heat of high level waste for permanent disposal are significantly reduced. The challenges in the back end are developing efficient process flow sheets for partitioning and ensuring proliferation-resistance of actinides. The present paper summarizes the recent development in the front and back end of uranium fuel cycle, highlighting the fuel development activities for thermal and fast reactors. (author)