Why is plutonium always used as fuel in fast reactors?
It is so mainly because plutonium shows the highest potential for breeding in a fast reactor. Explanation: An isotope of plutonium, viz. Pu-239, is used as the fissile component of the fuel in fast reactors. As said earlier, the fissile fraction in the fuel is usually about 20 – 30 %, in a fast reactor. If the fissile fraction needed is ensured, the performance with respect to energy production would nearly be the same with the alternative fissile materials, viz. Pu-239, U-233, and U-235. These nuclides differ significantly with respect to the neutron generation factor, called eta (h), and also in its energy-wise variation. h (for a nuclide) is defined as the number of neutrons produced in fission per neutron absorbed. This quantity indicates that for every neutron absorbed in the previous generation, h neutrons are made available in the present generation. Out of h neutrons available, 1 neutron is needed to carry on the fission chain reaction, 1 neutron to be captured in the fertile m
