Problem set 7

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Radiation Dosage and Radiation Protection

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Potassium is a naturally radioactive element. 40K accounts for 0.012% of the total amount of potassium. Its half-life is 1.3 • 109 years and the atomic weight is 39.10 g/mol. A given person weights 70 kg and contains 140 g potassium.

  1. Calculate the rate of disintegration of 40k in this person
  2. For each decay in 40K a beta particle with an average energy of 400 keV will be emitted. Potassium is evenly distributed throughout the human body. Assume that all the beta radiation is absorbed and calculate the total radiation dosage this person receives from 40k during a year (hint: 1keV = 1.6 • 10-16J).

The department of health in Norway has set a limit for the content of radioactive Cs in meat from sheep and reindeer to 600 Bq per kg after the Tjernobyl accident. Assume 137Cs is the only radioisotope in the deposition. It has a half-life of 30 years. The biological half-life is set to 110 days and the excretion is assumed to have an exponential progression. A person eats 1.0 kg of reindeer meat containing 6000 Bq 137Cs. All of the Cs is absorbed in the body and evenly distributed.

  1. How many grams of 137Cs are consumed?
  2. Every disintegration of 137Cs will on average emit either a beta particle or a conversion electron with energy of 200 keV. Assume that all the beta radiation and all the conversion electrons are absorbed while the gamma radiation escapes. Calculate the whole body dosage this person will receive from the meal.

Working with radioactive material requires different degrees of care relative to the nuclide at hand. There exists and international list over nuclides and their dangers.
One value on this list is the AlI value. Explain what it is and what it applies to.
Write down at least three properties about radioactive nuclides that makes them especially dangerous and choose a few examples from the Chart of the Nuclides.