Exposure Rate with Specific Gamma Ray Constant

This calculates the exposure rate (D) from a gamma-emitting point source at a specified distance using the specific gamma ray constant (Γ). The formula is the same for both unit systems, but the units differ.

Formula

  • \( D = \frac{\Gamma \cdot A}{d^2} \)

US Units

Variable Units Description
D R/hr Exposure rate (Roentgens per hour)
Γ R·cm²/(mCi·hr) Specific gamma ray constant
A mCi Activity (millicuries)
d cm Distance from source

Conversion Notes

  • 1 mCi = 37 MBq
  • 1 R ≈ 8.77 mSv (for gamma in air)
  • 1 R/hr ≈ 8.77 mSv/hr ≈ 8770 µSv/hr
  • To convert Γ: Γ(µSv·m²/(MBq·hr)) ≈ Γ(R·cm²/(mCi·hr)) × 0.237

Exposure Rate with Specific Gamma Ray Constant

\( D = \frac{\Gamma \cdot A}{d^2} \)
D
R/hr = (
Γ
×
A
) /
d
2

Unit System:

Digits of Precision:

R·cm²/(mCi·hr)
mCi
cm