Strontium-90 is produced in nuclear fission reactors.If ingested it can replace calcium in the bones.The half-life of ⁹⁰Sr is 27.7 years.If the activity of ⁹⁰Sr in the bones of an exposed person were 90 disintegrations per second,how long would it take the activity of ⁹⁰Sr to decrease to 7.8 disintegrations per second?

Question

Quizplus · Accepted Answer

The activity decreases by a factor of 90/7.8 = 11.54. Using the formula for radioactive decay, N(t) = N0 * (1/2)^(t/T), where T is the half-life, we solve for t: 11.54 = (1/2)^(t/27.7). Solving for t gives approximately 98 years.

Strontium-90 Is Produced in Nuclear Fission Reactors