Gamma Exposure Rate
Compute the exposure (or dose) rate of a point gamma source, X = Γ·A/d², from the exposure-rate constant (Γ, specific to the radionuclide), the source activity (A) and the distance (d). It combines the source strength with the inverse square law, allowing you to estimate the dose received at a given distance — fundamental in planning tasks with radioactive sources. Enter the gamma constant, the activity and the distance.
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Gamma exposure rate
How much dose per hour does a person receive near a gamma source? The exposure (or dose) rate from a point source is X = Γ·A/d², combining two factors: the source strength (its activity A) and the inverse square law (the fall-off with distance d). The gamma constant Γ is specific to each radionuclide and embeds the energy and the number of gamma photons emitted per disintegration — cobalt-60, for instance, is a 'hard' emitter with a high Γ, while others are milder. The result lets the medical physicist or the radiation protection supervisor estimate the dose of a task before carrying it out: if the rate reads a given value at 1 metre, what will it read at 3 metres? how long can I stay without exceeding the limit? It is the planning tool that puts the ALARA principle (As Low As Reasonably Achievable) into practice. Enter the gamma constant, the activity and the distance.
Related Tools
Decay Constant
Compute the radioactive decay constant, λ = ln(2)/T½, from the half-life (T½). The constant λ is the probability of a nucleus decaying per unit time — the larger it is, the more unstable the isotope and the shorter its half-life. It links the half-life (time for half the nuclei to decay) to the activity and to the exponential decay law. Enter the isotope's half-life.
Radioactive Activity
Compute the activity of a radioactive sample, A = λ·N, the product of the decay constant (λ) and the number of radioactive nuclei present (N). Activity, measured in becquerel (Bq = 1 disintegration/s) or curie, expresses how many nuclei decay per second. It is the fundamental quantity quantifying a radioactive source, and it decreases over time as nuclei decay. Enter the decay constant and the number of nuclei.
Maximum Noise Exposure Time
Calculate the maximum daily allowed noise exposure time, T = 8 ÷ 2^((SPL − 85) ÷ 5), from the sound pressure level SPL (dB(A)). The result, in hours, is the maximum exposure duration before reaching a 100% dose under the Brazilian NR-15 (85 dB(A) limit for 8 h, with a 5 dB dose-doubling rate). Every 5 dB above 85 halves the allowed time: 90 dB(A) allows 4 h, 95 dB(A) only 2 h. It is the basis for dose calculation and the planning of rotation and breaks. Enter the sound pressure level.
Normalized Exposure Level (NEN)
Calculate the 8-hour normalized exposure level (NEN), NEN = NE + 10·log₁₀(t ÷ 480), from the measured exposure level NE (dB(A)) and the actual exposure time t (minutes). The result, in dB(A), converts an exposure of any duration into the equivalent level that would produce the same dose over a standard 8-hour (480 min) shift, allowing direct comparison with the tolerance limit and action level. It is the quantity used by occupational hygiene standards to assess continuous or intermittent noise. Enter the measured level and the exposure time.
Effective Dose
Compute the effective dose, E = H·wT, multiplying the equivalent dose in an organ (H, in mSv) by the tissue weighting factor (wT) reflecting the tissue's radiosensitivity. While the equivalent dose accounts for the radiation type, the effective dose weights the risk by the irradiated organ (gonads and marrow are more sensitive than skin or bone). It is the quantity used in occupational dose limits. Enter the equivalent dose and the tissue weighting factor.
Radiation Shielding Attenuation
Compute the radiation intensity after passing through shielding, I = I₀·e^(−μ·x), by the exponential attenuation law, from the initial intensity (I₀), the material's linear attenuation coefficient (μ) and the thickness (x). Unlike alpha and beta particles (which have a finite range), gamma rays and X-rays are only exponentially attenuated — never fully blocked. It is the basis of shielding calculation. Enter the initial intensity, the attenuation coefficient and the thickness.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.