Interactive Lab · Health Physics

Time, Distance, and Shielding

Build a radiation-protection strategy and see how three different controls combine. The model uses an idealized gamma point source and narrow-beam shielding attenuation.

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Rate model

\dot D=\dot D_{1\,\mathrm m}\left(\frac{1\,\mathrm m}{r}\right)^2 2^{-x/\mathrm{HVL}}

Integrated dose

D=\dot D\,t

Model boundary: point-source geometry, no air attenuation, and narrow-beam photon attenuation. Real shielding design may require buildup, streaming, source geometry, and energy-spectrum treatment.

Protection plannerWithin target

Projected dose25.0 µSv5.0 µSv above target

Holding the other controls fixed, any one of these changes would meet the planning target.

t_{\max}=\frac{D_{\mathrm{target}}}{\dot D}

Maximum work time48.0 min

r_{\min}=1\,\mathrm m\sqrt{\frac{\dot D_{1\,\mathrm m}\,t\,T}{D_{\mathrm{target}}}}

Minimum distance2.24 m

x_{\min}=\mathrm{HVL}\log_2\!\left(\frac{D_{\mathrm{unshielded}}}{D_{\mathrm{target}}}\right)

Select a shield material—

f_t=\frac{t}{1\,\mathrm h}

1.00

f_r=\left(\frac{1\,\mathrm m}{r}\right)^2

0.250

T=2^{-x/\mathrm{HVL}}

1.000