Physics design of Indian thorium fuelled pebble bed reactor with FLiBe coolant

India is pursuing a comprehensive high temperature reactor program to fulfill its need for several crucial applications of nuclear energy such as hydrogen production. The program is designed on the basis of guidelines envisaging use of thorium based fuel, passive core heat removal by natural circulation of liquid coolant advanced safety features etc. The Innovative High Temperature Reactor (IHTR) is a 600-MWth pebble bed type reactor for hydrogen production with a fuel design similar to other existing HTRs, but with larger dimension pebbles of floating in a molten-salt (FLiBe) coolant flowing upward in natural circulation. Physics design analysis studies have been carried out to assess the neutronic feasibility of IHTR-600 core and efforts are being made to tackle various challenges encountered in the core design. Also, core neutronics studies are in advanced stage to design a 100 KWth Compact High Temperature Reactor (CHTR) which will serve as a technology demonstrator and a critical facility for the Indian high temperature reactor program. (author)