Plutonium-239 (t1/2 = 2.41 * 104 yr) represents a serious nuclear waste hazard. if seven half-lives are required to reach a tolerable level of radioactivity, how long must 239 pu be stored? enter your answer in scientific notation.

The half-life of Plutonium-239, t1/2 is 2.41 * 10⁴ yrs

time taken to reach tolerable level = seven half-lives

= 7 x t1/2

= 7 x 2.41 * 10⁴ yrs

= 168700 yrs

= 1.687 x 10⁵ yrs

Hence, the period of time that Plutonium-239 must be stored is 1.687 x 10⁵ years.