The decay chain of uranium includes radon, a noble gas. When uranium in the soil

Question

The decay chain of uranium includes radon, a noble gas. When uranium in the soil decays to radon, it may seep into houses; this can be a significant source of radiation exposure. Most of the exposure comes from the decay products of radon, but some comes from alpha decay of the radon itself. If radon in the air in your home is at the maximum permissible level, the gas in your lungs will have an activity of about 0.22 Bq. Each decay generates an alpha particle with 5.5 MeV of energy, and essentially all that energy is deposited in lung tissue.

Over the course of 1 year, what will be the dose equivalent in Sv to the approximately 0.90 kg mass of your lungs?

dose equivalent= ___ mSv/yr

Explanation / Answer

Equivalent dose per year is given by

HT = WR * DT,R

HT - Equivalent dose in (Sv) absorber by tissue in one year

DT,R – Absorbed dose in Gray(Gy) in tissue T by radiation type R

        = A/m * E

        = 0.22 Bq / 0.9 kg * (5.5 * 106 * 1.6 * 10–19 J)

DT,R = 2.15 * 10-13 Gy

WR – Radiation weighting factor defined by regulation = 20 for alpha rays.

Hence

HT = 20 * 2.15 * 10-13

HT = 43 * 10-10 mSv

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