Point & Extended Sources
Line Source Geometry (Piping & Rods)
Models exposure rates around radioactive piping, coolant headers, and fuel rods where close-in intensity drops linearly (1/d) before transitioning toward inverse-square (1/d²) beyond half the pipe length.
d ≤ L/2: I₂ = I₁(d₁/d₂) | d > L/2: (L/2d₂)²
Input Parameters
Calculation Goal
Standard Pipe & Rod Lengths
Near Field (1/d)
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
Near-Field (d ≤ L/2): I₂ = I₁ × (d₁ / d₂) ; Far-Field: Transitions past L/2 to inverse-square
| Symbol | Parameter | Default Unit | Definition |
|---|---|---|---|
| L | cm | Length of the radioactive pipe segment or fuel assembly. | |
| I₁ | R | Measured exposure rate at initial perpendicular distance D₁. | |
| D₁ | cm | Initial perpendicular distance from the pipe centerline. | |
| I₂ | R | Resulting exposure rate at perpendicular distance D₂. | |
| D₂ | cm | Target perpendicular standoff distance from the pipe. |
Health Physics Notes & Related Calculators
Operational Guidance
- Near-Field Zone (d ≤ 0.5L): Radiation intensity is governed by cylindrical divergence and drops linearly with distance (I₂ = I₁ × d₁/d₂).
- Transition Zone (0.5L < d ≤ 1.0L): End effects reduce solid angle; empirical field rules scale as (d₁/d₂)^1.5.
- Analytical Sievert / Arctangent Model: I(d) ∝ (1/d) × arctan(L / 2d) provides a continuous curve across all distance regimes.
- Far-Field Zone (d > 1.5L): The pipe or rod behaves asymptotically like a point source (1/d²).
Related Calculators
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