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Nuclear Reactions

Problem 6.287

A gold foil of mass m=0.20 gm=0.20 \mathrm{~g} was irradiated during t=6.0t=6.0 hours by a thermal neutron flux falling normally on its surface. Following τ=12\tau=12 hours after the completion of irradiation the activity of the foil became equal to A=1.9⋅107A=1.9 \cdot 10^{7} dis/s. Find the neutron flux density if the effective cross-section of formation of a radioactive nucleus is σ=96 b,\sigma=96 \mathrm{~b}, and the half-life is equal to T=2.7T=2.7 days.

Reveal Answer
 6.287. J=A˙eλt/σN0(1−e−λt)=6⋅109 part. /(cm2⋅s), where λ \text { 6.287. } J=\dot{A} \mathrm{e}^{\lambda t} / \sigma N_{0}\left(1-\mathrm{e}^{-\lambda t}\right)=6 \cdot 10^{9} \text { part. } /\left(\mathrm{cm}^{2} \cdot \mathrm{s}\right), \text { where } \lambda is the decay constant, N0N_{0} is the number of Au nuclei in the foil.
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