Point & Extended Sources
Plane / Disk Source (Spills & Walls)
Evaluates dose rates above circularly distributed floor spills, sumps, or contaminated walls across contact, transition, and far-field elevation zones.
d ≤ 0.1R: I₀ | 0.1R–0.7R: I₀/3 | d > 0.7R: (I₀/3)(0.7R/d)²
Input Parameters
Calculation Goal
Area Radius & Elevation Presets
Zone 3 (>0.7R)
Convert Rectangular Spill Area to Effective Radius (R = √(L×W / π))
Calculated Result & Visual Analysis
Nominal Solved Value Updated automatically
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Enter parameters on the left to calculate.
Geometry & Field Diagram
Interactive Model
Sensitivity Curve
Governing Equation & Parameters
Zone 1 (≤0.1R): Constant I₀; Zone 2 (0.1R–0.7R): I₀ / 3; Zone 3 (>0.7R): (I₀ / 3) × (0.7R / d)²
| Symbol | Parameter | Default Unit | Definition |
|---|---|---|---|
| R | cm | Radius of the circular contamination area or tank face. | |
| I₁ | R | Measured exposure rate at initial distance D₁ from the surface. | |
| D₁ | cm | Initial perpendicular distance from the center of the contaminated area. | |
| I₂ | R | Calculated exposure rate at target distance D₂. | |
| D₂ | cm | Target worker elevation or standoff distance from the surface. |
Health Physics Notes & Related Calculators
Operational Guidance
- Contact Zone (d ≤ 0.1R): The contaminated surface subtends nearly 2π steradians; dose rate remains effectively constant with height.
- Transition Zone (0.1R < d ≤ 0.7R): Dose rate steps down to approximately one-third of the contact reading.
- Far-Field Zone (d > 0.7R): Dose rate follows inverse-square drop-off anchored at 0.7R.
- For rectangular spills of length L and width W, use the effective circular radius R_eff = √(L × W / π).
Related Calculators
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