In a nuclear reactor, the kinetic energy of a fast-moving neutron is reduced by a series of yyy random collisions with moderator nuclei.
The final kinetic energy EfE_fEf of the neutron is given by:
Ef=E0e−by E_f = E_0 e^{-b y} Ef=E0e−bywhere E0E_0E0 is the initial kinetic energy of the neutron and b=0.56b = 0.56b=0.56.
A thermal neutron has kinetic energy equivalent to the average kinetic energy of a particle of an ideal gas at a temperature of 300 K300\text{ K}300 K.
A particular neutron is released during fission with an initial kinetic energy of 2.0 MeV2.0\text{ MeV}2.0 MeV.
Calculate the minimum number of collisions yyy required for this neutron to become a thermal neutron. (Boltzmann constant kB=1.38×10−23 J K−1k_B = 1.38 \times 10^{-23}\text{ J K}^{-1}kB=1.38×10−23 J K−1, electron charge e=1.60×10−19 Ce = 1.60 \times 10^{-19}\text{ C}e=1.60×10−19 C)
