Annual dose and equivalent X-rays

Problem

Estimate, to order of magnitude, how many chest X-rays (about $0{,}1\ \text{mSv}$ each) are equivalent to:

• (a) the dose received on an intercontinental Rome–New York flight ($\approx 0{,}05\ \text{mSv}$ per leg, round trip);
• (b) the annual natural background dose on an Italian plain ($\approx 2{,}4\ \text{mSv}$).

Solution

(a) Round-trip flight. Two legs of $0{,}05\ \text{mSv}$ give a total dose $D_{\text{flight}} = 2\cdot 0{,}05 = 0{,}1\ \text{mSv}$. Dividing by the dose of one X-ray:

$n_{\text{flight}} = \frac{0{,}1}{0{,}1} = 1\ \text{chest X-ray}$

(b) Annual natural background. The background dose $D_{\text{background}} = 2{,}4\ \text{mSv}$ corresponds to:

$n_{\text{background}} = \frac{2{,}4}{0{,}1} = 24\ \text{chest X-rays}$

Comment. These are useful comparisons to give practical meaning to doses: a round-trip transatlantic flight “weighs” as much as a single X-ray, while the natural radioactivity we are exposed to in a year is equivalent to a couple of dozen chest X-rays.

$\ev{\text{round-trip flight}\equiv 1\ \text{X-ray};\ \text{annual background}\equiv 24\ \text{X-rays}}$

Collegamenti

Argomenti: Fisica nucleare Concetti: Decadimento radioattivo Competenze: Stime di Fermi