A technician plans a lead shield for a source

PHYSICS · Multi-part · Fermi University Physics · Nuclear Physics · Radiation interactions, detection and dosimetry · Radiation interactions, detection and dosimetry

The Nucleus Resolved, Ch Dose: kerma, cavity theory, and what energy does to a cell

Problem

A technician plans a lead shield for a

662\,\mathrm{keV}

^{137}\mathrm{Cs}

source, using

\mu_{\rm att} = 1.25\,\mathrm{cm^{-1}}

for lead at this energy. The working reads: "

5.0\,\mathrm{cm}

of lead gives

\mu_{\rm att}x = 1.25\times5.0 = 6.25

, so the transmitted fraction is

e^{-6.25} = 1.9\times10^{-3}

. The dose rate behind the shield is therefore

1.9\times10^{-3}

of the unshielded dose rate, and this fully accounts for the shielding." ((a)) Find the error in this calculation. ((b)) Given a build-up factor of

2.6

for this thickness and geometry, state the actual transmitted dose fraction and the factor by which the technician's working underestimates the dose behind the shield.

Related theory

Nuclear Physics

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