> An estimated 300 curies of radioactive cobalt found their way to the two Mexican foundries, one of which manufactured metal table legs for shipment to the largest distributor of restaurant tables in the U.S., while the other produced steel rods used in the reinforcement of concrete building projects. About 600 tons of the contaminated steel were shipped to the U.S. from December 1983 to January 1984."

How much is 300 curies?

About 303 g according to the table in https://en.m.wikipedia.org/wiki/Curie_(unit)

883 μg/Ci * 300 Ci is less than a gram.

300 Ci is 11 TBq (terabecquerel), or 11·10^12 decays per second. Co-60 has a half life of 166 million seconds, so it was 11·166·10^18/ln 2 atoms=2.6·10^21 atoms, which is 0.004 moles (a mole is 6.02·10^23 atoms).

A mole of cobalt 60 weighs 60 g, so it was a quarter of a gram if I did the calculations right.

The ln 2 factor is because the probability of a decay happening in a second is ln 2 divided by the half life.

> 166 million seconds

Or 5,2 years

Yeah but becquerels are #decays per second, so I need the probability of a decay happening in a second, not in a year. :) Sooner or later the dreaded multiply by 86400*365 will happen.