In the case of FBTR whether heavy water or ordinary water can be used as coolant instead of Sodium?
Since water rapidly deaccelerates the fast moving fission neutrons to less than the energy suitable for breeding, it cannot be used as coolant. The problem of removing large amount of heat from a small volume of fuel by a coolant which does not reduce the neutron energy unacceptably is solved in the FBR by the use of liquid Sodium because of its high thermal conductivity.
