RPR-26

Time–distance–shielding

H = Ḣ0 t (r0/r)² 10^{−x/TVL}. The three-lever protection product.

Reading speed

ALARATime-distance-shielding

Governing equation

H=\dot H_0 t\,(r_0/r)^{2}10^{-x/\mathrm{TVL}}

where

\dot H_0: Rate at r0, unshielded (µSv/h)
t: Time (min)
r_0: Reference distance (m)
r: Working distance (m)
x: Shield thickness (mm)
TVL: Tenth-value layer (mm)
H: Received dose (µSv)

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-26 — Time–distance–shielding) is the form associated with Time-distance-shielding. Working symbols: $\dot H_0$ , $t$ , $r_0$ , $r$ , $x$ , $TVL$ $\rightarrow$ $H$ . Time cuts linearly, distance as a square, shielding as decades of TVL. Always check scatter around the shield.

Purpose

Purpose: compute

H

from

\dot H_0

t

r_0

r

x

TVL

in Radiation protection via

H=\dot H_0 t\,(r_0/r)^{2}10^{-x/\mathrm{TVL}}

H = Ḣ0 t (r0/r)² 10^{−x/TVL}. The three-lever protection product. 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 = 200.000\,\mathrm{\mu Sv/h}

t = 10.000\,\mathrm{min}

r_0 = 1.000\,\mathrm{m}

r = 2.000\,\mathrm{m}

x = 6.000\,\mathrm{mm}

TVL = 4.000\,\mathrm{mm}

, the governing relation

H=\dot H_0 t\,(r_0/r)^{2}10^{-x/\mathrm{TVL}}

yields

H = 0.26\,\mathrm{\mu Sv}

. A stopwatch, a walk-back, a lead brick, a remaining dose. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Rate at r0, unshielded \dot H_0200 µSv/hTime t10 minReference distance r_01 mWorking distance r2 mShield thickness x6 mmTenth-value layer TVL4 mm

Outputs

Received dose H0.26 µSv

Reading speed

Watch on YouTube

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Narration of this film

A stopwatch, a walk-back, a lead brick, a remaining dose.

Time cuts linearly, distance as a square, shielding as decades of TVL. Always check scatter around the shield.

Reading speed

Watch on YouTube