KLT-40S nuclear reactor is a small modular floating nuclear power plant which is used to supply electricity to isolated zones or installed in submarine/icebreakers. Increasing fuel life time in the reactor core is a premium target to improve the efficiency and enhance the operation time of the ships between refueling. Five different types of fuel are tested on an assembly of KLT-40S reactor. These types are: Typical UO2 fuel dispersed in silumin alloy, uranium nitride fuel, uranium nitride mixed with ZrO2 , thorium mixed with 235U and thorium mixed with 233U. The fuel enrichment and the ratio of Silumin alloy is fixed among all types of fuel. Characteristics and neutronic performance of all fuel types are analyzed. The results indicate that replacement of UO2 fuel by uranium nitride and thorium mixed with 233U increases the fuel cycle length by 24 % and 17 % respectively. Uranium nitride has the highest fissile plutonium breeding, thorium fuel supports proliferation resistance with low minor actinides production.