Question

A gold foil of mass m = 0.20 g was irradiated during t = 6.0 hours by a thermal neutron flux falling normally on its surface. Following τ = 12 hours after the completion of irradiation the activity of the foil became equal to A = 1.9.10⁷ dis/s. Find the neutron flux density if the effective cross-section of formation of a radioactive nucleus is σ = 96 b, and the half-life is equal to T = 2.7 days.

Answer 1

We apply the formula of the previous problem except that have 

N = no. of radio nuclide and no. of host nuclei originally.

T = half life of the radionuclide.

After the source of neutrons is cut off the activity after time T will be