## How much of 218Po will be generated (nanograms)?

7. 222Rn decays to 218Po. At the time t=0, a pure Rn, which under normal pressure and temperature conditions would have volume of 0.65 m3, is captured and sealed in a vial:

a) What time (in min) is needed for accumulation of a maximal amount of 218Po?

b) How much of 218Po will be generated (nanograms)?

c) What will be the ratio of atoms of 222Rn and 218Po when they achieve equilibrium?

## a nuclidic ratio

In a rock, one finds a nuclidic ratio of 206Pb to 238U of 0.60. What is the age of the rock?

## an ore mixture at equilibrium

5. A measurement of an ore mixture at equilibrium shows 2.1×104 times as many 235U atoms as 231Pa atoms. Calculate the half-life of 235U from the assay data and the known half-life of 231Pa (3.28×104 yr)

## trapped potassium

4. Bones, containing trapped potassium, were found in 1960 in rock with a typical sample yielding a total of 0.25 g K. A fraction (assume 0.000117) of the trapped potassium was 40K, which decays into 40Ar. This sample contained 7.4×10-10 g of 40Ar, of which 9.3×10-11 g was determined to be contaminated from the air. What is the approximate age of the bones?

3. A short-lived radioisotope yttrium-90, a medical isotope, is produced by a Sr/Y -90 generator, where the long-lived parent Sr-90 is sorbed on a chromatographic column and yttrium is eluated. The half-lives are T1/2 (Sr-90) = 28.78 y, T1/2(Y-90) = 64 hours=2. 67 days.

a) If the activity concentration of Y-90 in the eluate is 120 kBq/mL, what volume of the physiological solution should be added to obtain a solution with 60 kBq/mL?

Correct Answer: The solution must be diluted two-fold, so the same volume it has now must be added. 60 kBq/mL

b) What time it takes for yttrium to achieve 75% of strontium activity?

## fission product mixture

1. If 140Ba is freshly separated from a fission product mixture and found to contain 125 milliCi, (a) what is the activity of 140La that will grow into the sample in 17.2 hr? (b) What is the maximum activity of 140La that will ever be present in the sample, and (c) when will it occur?