An average person is exposed to about 360 millirem of background radiation a year from a variety of sources.
Two-thirds of that comes from inhalation of 222Ra produced in soil. Given that 222Ra decays by alpha emission,
estimate the absorbed dose in a) Joules and b) Grays for a 60 kg person from one-year inhalation of radon.

Question

An average person is exposed to about 360 millirem of background radiation a year from a variety of sources. 
Two-thirds of that comes from inhalation of 222Ra produced in soil. Given that 222Ra decays by alpha emission, 
estimate the absorbed dose in a) Joules and b) Grays for a 60 kg person from one-year inhalation of radon.

Vocaloid · Answer

@imqwerty opinions on this? my instinct is to calculate the difference in mass between the parent and daughter nuclei, convert to that to the corresponding energy difference, unsure if this is the right approach

imqwerty · Answer

@vocaloid wrote:

@imqwerty opinions on this? my instinct is to calculate the difference in mass between the parent and daughter nuclei, convert to that to the corresponding energy difference, unsure if this is the right approach

You can do that, but it requires information about the number of parent nuclei and how much of the dose gets absorbed by the person. This info isn't directly given in the question but 360 millirems account for all of these. It basically measures the biologically effective dose. Useful formulas: dose in rem = dose in rad x Quality factor Quality factor for alpha particles = 20 1gray = 100 rads = 1 J/Kg

imqwerty · Answer

Make sure you take only 2/3rd of 360 millirems because it asks for absorbed dose by Radon inhalation and not the whole.