1. Following a terrorist release of Cesium-137 (half-life of 30 years) in downtown, clean up efforts were successful in removing all but 100 curies. How long will it take for the contamination to decay to about 5 curies?
A. 90 years
B. 130 years
C. 175 Years
D. 215 years
Hello and thank you for posting your question to brainmass.
Every 30 years the amount of CS-137 drops by a factor of two.
If we start with N0 nuclei, then after 30 years we will have N0/2 ...
The solution shows how to obtain the time needed for the radiation to fall to a certain level.