In fast breeder nuclear reactor power plants, the ratio of fissile material produced to fissile material consumed is

The correct answer is greater than 1.

Key Points

• Fast breeder reactor (FBR) which uses fast (i.e. unmoderated) neutrons to breed fissile plutonium and possibly higher transuranic from fertile uranium-238.
• The fast spectrum is flexible enough that it can also breed fissile uranium-233 from thorium.
• One measure of a reactor's performance is the "conversion ratio", defined as the ratio of new fissile atoms produced to fissile atoms consumed. 
• A breeder reactor is a nuclear reactor that generates more fissile material than it consumes i.e., the ratio of fissile material produced to fissile material consumed is greater than 1.
• When the conversion ratio is greater than 1, it is often called the "breeding ratio". 

Therefore, the correct answer is greater than 1.