Download EVE 290 Introduction to Environmental Engineering HW #8 1. A

EVE 290
Introduction to Environmental Engineering
HW #8
1. A radioactive nuclide is reduced by 90% in 12 minutes. What is its half-life? Hint: What is the
“order” of the reaction process that is associated with radioactivity? (Ans: 3.6 minutes)
2. A radioactive waste from a clinical laboratory contains 0.2 microcuries of calcium-45 (45Ca) per
liter. The half-life of 45Ca is 152 days. How long must the waste be stored before the level of
radioactivity falls below the required maximum of 0.01 microcurie/liter? (Ans: approx. 650
days)
3. Initially, a bacteria culture that grows according to zero-order kinetics contains 1250 bacteria.
The count increases to approximately 12,500 bacteria 6 hours later. What is the doubling time
(td) for this bacterium? (Ans: 0.67 hr)
4. Repeat problem 3, assuming that second-order kinetics governs the bacterial growth.