Gamma radiation dose from radioactive cobalt

Radiation Energy Transfer and Dose

⁵⁷₂₇Co emits 122 keV gamma-rays. If a 70kg person swallowed a 4 micro Curie sample of this, what would the dose rate (rads/day) averaged over the whole body. Assume that 50% of the gamma ray energy is absorbed by the body.

4 micro Ci is equivalent to 4.0x10⁶*3.7x10¹⁰ = 148000 disintegrations per second.

This is equivalent to 148000*122keV*1.6x10^-19 J/s = 1.4x10^-9 J/s released into the body, which absorbs half of this:

7x10^-10 J/s

0.000062 J/day

9x10^-7 J/kg/day

9x10^-5 rad/day