Internal Dosimetry
1. Starting with the retention function for tritium defined in ICRP 30, prove that as t → ∞ ,
the number of nuclear transitions reduces to [A0/λ].
2. The biological half-life of tritium is 10 days. A worker has 1 MBq of tritium activity left in his body after an uptake seven days ago.
(a) What was the initial uptake?
(b) Use the initial uptake to calculate how many nuclear transitions occurred in the body during those seven days.
3. For a fresh 90Sr source, calculate (analytically) the time required to build-in the maximum activity of 90Y. Graph both decays as a function of time. Is this secular or transient equilibrium? Explain the difference between the two.
4. Given a 3-compartment first-order kinetic model, and ending with 1015 atoms of the 2nd progeny (3rd compartment) after 100 hours, use Bateman equations to predict the number of atoms in the 1st compartment at time zero.
The half-life of transfer from the 1st to 2nd compartment is 15 hours, the half-life of transfer from the 2nd to 3rd compartment is 30 hours, and the half-life of transfer out of the 3rd compartment is 25 hours.
5. Construct a STELLA Model to execute the kinetics of problem #4. Run the problem for 100 hours and compare the STELLA results to your calculated results.