RPR-25

Exclusion-zone radius

r = r0 √(Ḣ0 / Ḣ_lim). Inverse-square radius of a dose-rate contour.

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ZoningExclusion radius

Governing equation

r=r_0\sqrt{\dot H_0/\dot H_{\lim}}

$\dot H_{lim} \in \left[0.05, 25\right]$

where

\dot H_0: Rate at r0 (µSv/h)
r_0: Reference distance (m)
\dot H_{lim}: Contour limit (µSv/h)
r: Exclusion radius (m)

The figure, part by part

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①

Governing law — red

r=r_0\sqrt{\dot H_0/\dot H_{\lim}}

$\dot H_{lim} \in \left[0.05, 25\right]$

$\dot H_{lim} = 0.05$ $r = 40$

Along the curve

②

Domain of the variable — blue

\dot H_{lim}_{\min} = 0.05,\quad \dot H_{lim}_{\max} = 25

$\dot H_{lim} \in \left[0.05, 25\right]$

$\dot H_{lim} = 0.05$ $\dot H_{lim} = 0.05$

Along the curve

③

Response curve — green

r=r_0\sqrt{\dot H_0/\dot H_{\lim}}

$\dot H_{lim} \in \left[0.05, 25\right]$

$\dot H_{lim} = 0.05$ $r = 40$

Along the curve

④

Rate of change — amber

\frac{\mathrm{d}r}{\mathrm{d}\dot H_{lim}}

$\dot H_{lim} \in \left[0.05, 25\right]$

$\dot H_{lim} = 0.207$ $r^{\prime} = -80.21$

Along the curve

Lecture brief

Historical brief

Inverse-square, half-value layer, ICRP weighting and ALARA are the protection craft since the 1920s commissions. The lab computes transmission, equivalent dose and a shielding snapshot. This sheet (RPR-25 — Exclusion-zone radius) is the form associated with Exclusion radius. Working symbols: $\dot H_0$ , $r_0$ , $\dot H_{lim}$ $\rightarrow$ $r$ . Public 0.5 µSv/h and controlled 7.5 µSv/h are common contour values (≈1 mSv/y public at 2000 h). Scatter and shielding shrink the true radius.

Purpose

Purpose: compute

r

from

\dot H_0

r_0

\dot H_{lim}

in Radiation protection via

r=r_0\sqrt{\dot H_0/\dot H_{\lim}}

r = r0 √(Ḣ0 / Ḣ_lim). Inverse-square radius of a dose-rate contour. Use it when a real radiation protection question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

\dot H_0 = 80.000\,\mathrm{\mu Sv/h}

r_0 = 1.000\,\mathrm{m}

\dot H_{lim} = 0.500\,\mathrm{\mu Sv/h}

, the governing relation

r=r_0\sqrt{\dot H_0/\dot H_{\lim}}

yields

r = 12.65\,\mathrm{m}

. A source and a circular keep-out painted on the floor. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Rate at r0 \dot H_080 µSv/hReference distance r_01 mContour limit \dot H_{lim}0.5 µSv/h

Outputs

Exclusion radius r12.65 m

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Narration of this film

A source and a circular keep-out painted on the floor.

Public 0.5 µSv/h and controlled 7.5 µSv/h are common contour values (≈1 mSv/y public at 2000 h). Scatter and shielding shrink the true radius.

Reading speed

Watch on YouTube