High School

\(^{57}\text{Co}\) emits 122-keV gamma rays. If a 70-kg person swallowed 1.85 \(\mu\)Ci of \(^{57}\text{Co}\), what would be the dose rate (Gy/day) averaged over the whole body? Assume that 50% of the gamma radiation is absorbed by the body.

Answer :

Final Answer:

The dose rate averaged over the whole body from swallowing 1.85 µCi of [tex]\(^{57}\)[/tex]Co is approximately 0.043 Gy/day.

Explanation:

To calculate the dose rate, first, we need to find the activity of [tex]\(^{57}\)[/tex]Co in becquerels (Bq). We convert the given activity from microcuries (µCi) to becquerels using the conversion factor [tex]1 µCi = \(3.7 \times 10^4\)[/tex] Bq. Then, we use the dose conversion factor for [tex]\(^{57}\)Co[/tex], which is 5.2 × 10⁻¹¹ Gy/Bq-s for an internal dose. Since we want to find the dose rate per day, we multiply by the number of seconds in a day. Dividing the result by the person's mass gives us the dose rate averaged over the whole body in grays per day (Gy/day).

The calculation is as follows:

[tex]Activity of \(^{57}\)Co = \(1.85 \, \mu Ci \times 3.7 \times 10^4 \, Bq/\mu Ci\) = \(6.845 \times 10^4 \, Bq\)[/tex]

[tex]Dose rate = \(\frac{{Activity \times Dose \, conversion \, factor \times 86,400 \, s/day}}{{70 \, kg}}\)[/tex]

[tex]\(= \frac{{6.845 \times 10^4 \, Bq \times 5.2 \times 10^{-11} \, Gy/Bq-s \times 86,400 \, s/day}}{{70 \, kg}}\)[/tex]

[tex]\(= 0.043 \, Gy/day\)[/tex]

Therefore, the dose rate averaged over the whole body is approximately 0.043 Gy/day.