This question is about an accident at the Chernobyl nuclear power station in which radioactive gas and dust were released into the atmosphere. The radioactive isotopes in the Chernobyl fallout which caused most concern were iodine-131 and caesium-137. Both are beta and gamma emitters. Iodine-131, in rainfall, found its way into milk but caesium-137, with a half-life of 30 years, may cause more long term problems.

a. From which part of the atom do the beta and gamma rays come?

b. Explain what the number 131 tells you about the iodine atom.

c. After the Chernobyl accident, a milk sample containing iodine-131 was found to have an activity of 1600 units per litre. The activity of the sample was measured every 7 days and the results are shown in the table below.

i. Draw a graph of activity against time, using the gird on the next page as a guide.

ii. Estimate the half-life of iodine-131 and show on the graph how you arrived at your answer:

d. Give a reason why caesium-137 could cause longer-term problems than iodine-131.

Transcribed Image Text:

time/days activity/units per litre 21 28 1600 875 470 260 140 77 14 35