Gamma Radiation Shielding Calculator
Radiation protection physics: Calculate narrow-beam and broad-beam gamma attenuation, Half-Value Layers (HVL), Tenth-Value Layers (TVL), and Taylor buildup factors.
Source & Shield Configuration
Attenuated Radiation Dose Rate
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Frequently Asked Questions
What is the difference between narrow-beam and broad-beam gamma attenuation?
Narrow-beam geometry (good geometry) assumes every photon that undergoes Compton scattering is completely deflected away from the detector, following the simple exponential law I = I0 * exp(-mu * x). In real broad-beam shielding, scattered photons can undergo multiple secondary Compton collisions and still emerge towards the target. The Buildup Factor B(mu*x) > 1 mathematically accounts for these scattered photons.
What is a Half-Value Layer (HVL) and Tenth-Value Layer (TVL)?
The Half-Value Layer (HVL = ln(2) / mu ≈ 0.693 / mu) is the thickness of a given shielding material needed to reduce gamma intensity by 50%. The Tenth-Value Layer (TVL = ln(10) / mu ≈ 2.303 / mu) is the thickness required to reduce intensity by 90% (a 10-fold reduction). Each additional TVL adds another order of magnitude of radiation protection.
Why is lead preferred for X-rays while concrete is preferred for nuclear reactors?
Lead has a high atomic number (Z = 82) and high density (11.34 g/cm³), making it compact and effective at stopping low-to-medium energy gammas via the photoelectric effect and Compton scattering. In nuclear reactors, thick concrete is preferred because it is economical in massive volumes, structurally load-bearing, and contains significant hydrogen (water of crystallization) that effectively thermalizes and captures fast neutrons alongside gamma rays.