RPR-18

Quality factor Q(L)

Q = 1 (L<10), 0.32L−2.2 (10–100), 300/√L (L>100 keV/μm). H = Q D.

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QuantitiesICRU Q(L)ICRP 60

Governing equation

Q(L)=\begin{cases}1&L<10\\0.32L-2.2&10\le L\le 100\\300/\sqrt L&L>100\end{cases}

where

L: Unrestricted LET (keV/µm)
D: Absorbed dose (mGy)
Q: Quality factor (—)
H: Dose equivalent (mSv)

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-18 — Quality factor Q(L)) is the form associated with ICRU Q(L) · ICRP 60. Working symbols: $L$ , $D$ $\rightarrow$ $Q$ , $H$ . Q is the operational ICRU factor; wR is the ICRP protection factor. They agree at the ends (photons 1, α ~20) and differ in between.

Purpose

Purpose: compute

Q

H

from

L

D

in Radiation protection via

Q(L)=\begin{cases}1&L<10\\0.32L-2.2&10\le L\le 100\\300/\sqrt L&L>100\end{cases}

Q = 1 (L<10), 0.32L−2.2 (10–100), 300/√L (L>100 keV/μm). H = Q D. 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

L = 10.000\,\mathrm{keV/\mu m}

D = 1.000\,\mathrm{mGy}

, the governing relation

Q(L)=\begin{cases}1&L<10\\0.32L-2.2&10\le L\le 100\\300/\sqrt L&L>100\end{cases}

yields

Q = 1.00\,\mathrm{—}

H = 1.000\,\mathrm{mSv}

. A LET slider, a Q bar, a sievert from a gray. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Unrestricted LET L10 keV/µmAbsorbed dose D1 mGy

Outputs

Quality factor Q1.00 —
Dose equivalent H1.000 mSv

Reading speed

Watch on YouTube

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Narration of this film

A LET slider, a Q bar, a sievert from a gray.

Q is the operational ICRU factor; wR is the ICRP protection factor. They agree at the ends (photons 1, α ~20) and differ in between.

Reading speed

Watch on YouTube