Shielding converter
Convert radiation shielding between half-value layers and real thicknesses of lead or concrete.
That's about the same as a shielded wall. About 12.5% of the radiation still gets through.
What it means
How much gets stopped?
Thicknesses are for a 1 MeV gamma beam. Half-value layers change with photon energy, so a shield that works for one isotope may not for another.
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Your shielding in every unit
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Three things worth knowing
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Ten layers is a thousandth
2¹⁰ is 1,024, so ten halvings leave about one part in a thousand. Twenty leave one in a million.
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Why it never reaches zero
Each layer removes a fixed fraction, not a fixed amount, so the beam shrinks exponentially and never quite stops. Shielding is always a question of how much is acceptable.
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Layers depend on energy
Lead’s half-value layer is under a millimeter for an X-ray tube and about twelve millimeters for a cobalt-60 source. Quoting a thickness without the energy says very little.
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Background
About half-value layers
Shielding does not stop radiation; it halves it, again and again. One half-value layer lets half through, two let a quarter, ten let a thousandth.
Counting in layers rather than millimeters is what lets you compare materials: at 1 MeV, one layer is 8.9 mm of lead, 15.6 mm of steel or 47 mm of concrete.