Question

interaction cross section of the neutrons ith the nucleus, if the mean free path of the neutrons in the nuclear matter is about 10000m is?

Answer 1

The mean-free-path length is

$$\lambda=\frac{1}{\Sigma_t}\rightarrow\Sigma_t=\frac{1}{\lambda}=1/10000=1\cdot10^{-4}\text{ m}^{-1}.$$