Thermal neutrons fall normally on the surface of a thin gold foil consisting of stable Au197 nuclide. The neutron flux density is J = 1.0 ∙ 1010 part./(s ∙ cm2). The mass of the foil is m = l0 mg. The neutron capture produces beta-active Au198 nuclei with half-life T = 2.7 days. The effective capture cross-section is σ = 98 b. Find:
(a) The irradiation time after which the number of Au197 nuclei decreases by η = 1.0%;
(b) The maximum number of Au198 nuclei that can be formed during protracted irradiation.