Question #244040

Solve the following problems.

In a certain sample, 12% of the original number of radioactive nuclei have undergone disintegration in

a period of 100 years.

1. What percentage of the original radioactive nuclei will remain after 1,000 years?

2. In how many years will only one-fourth of the original number remain?

In a certain sample, 12% of the original number of radioactive nuclei have undergone disintegration in

a period of 100 years.

1. What percentage of the original radioactive nuclei will remain after 1,000 years?

2. In how many years will only one-fourth of the original number remain?

Expert's answer

(1)

To have less than one left, one needs a DF < 1/1000. no. 12%

This happens after 10 half-lives because (1/2)10 = 1/1024, so after 200 minutes (3 hrs 20 min).

(2)

• Ratio of total radioisotope activity to total mass of the element present

• Measured in Bq/g or Bq/mole

• Useful if radioactive and non-radioactive isotopes of the same element are in mixture (sample with carrier)

• Maximum Specific Activity in carrier-free samples:

Carrier Free Specific Activity (CFSA)

"CFSA [Bq\/g] \u2248 4.8\\times1018 \/(A\\times T1\/2) for T1\/2 \\space given\\space in\\space days,"

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