FAST BREEDER REACTORS….”SUNSHINE” of Indian Nuclear Programme Over 55 years of Indian nuclear program, fast breeder reactors plays a key role. India’s nuclear programme started with research reactors, grown up with thermal reactors and now rising high with FBRs. Owing to the scarcity of fissile fuel, FBRs become the backbone for the sustenance of nuclear power in India. Designing FBR is highly challenging in itself by reason of its exigent core design, safety issues, high fissile fuel inventory and economics. FBR core design is highly demanding because of large neutron flux of high energy regime. Materials required within the core should withstand such environment. This book contains the basic information about the FBR core and design concept. Brief information about Indian nuclear program and introduction to rectors make it complete text to start with. Case study of optimized fuel pin design’s potential energy available will give a flavor of core design. This work is basically meant for the students requiring basic knowledge about the fast reactors so that they can further build upon. I wish them a very good luck and urge for their comments in order to improve the work.