Question

An accident in a laboratory results in a room being contaminated by a radioisotope with a half-life of 8 days. If the radiation is measured to be eight times the maximum permissible level, how much time must elapse before the room is safe to enter?

Answer 1

24 days

Explanation:

Let the permissible time be Ro

Let the initial activity be R= 8Ro

From;

0.693/t1/2 × t= 2.303 log R/Ro

Half life of the radionuclide= t1/2 = 8 days.

Hence;

0.693/8 × t = 2.303 log 8

t= 2.1/0.087

t= 24 days