Exposure from Activity

Calculate exposure rate using the specific gamma-ray constant (Γ), activity (A), and distance (d): Ẋ = Γ · A / d²

Gamma Constant (Γ): μSv·m²/MBq·h mSv·m²/MBq·h Sv·m²/MBq·h μR·cm²/mCi·h mR·cm²/mCi·h R·cm²/mCi·h

Activity (A): Bq kBq MBq GBq mCi Ci

Distance (d): meters centimeters feet

Output Exposure Unit: μSv/h mSv/h Sv/h μR/h mR/h R/h

Assumes point source and no shielding. Uses the approximation 1 mR ≈ 10 μSv (thus 1 R ≈ 10,000 μSv) for photon fields.

Reference: Specific Gamma-Ray Constants of Common Radionuclides

Radionuclide	Half-life	Main γ Energy (keV)	Γ (R·cm² / mCi·h)
Tc-99m	6 h	140	0.78
I-131	8 d	364	2.2
F-18	110 min	511	5.7

Made by Poovendhan.