Reading and Answering 10


In the previous assignment, we used the level of cesium-137 in trout and char to determine the ecological half-life for cesium in a lake. That assignment was not interested in the radiation dose to the fish; the fish were only being used as a means to probe the radioactivity remaining in a Chernobyl-contaminated lake. In this assignment, however, we will examine some different methods of estimating the organ radiation doses to rainbow trout from uptake of I-131. You will notice that the methods used are very similar to the approaches used to assess organ doses in humans.

Read the paper below and answer the questions that follow.

Q1: The data used in this experiment was based on an intentional release of iodine-131 into Fern Lake in Washington State in 1957. (The radioactive iodine was being used as a tracer to follow the kinetics of stable iodine in the lake.) Suppose the radioactivity was released into the lake on July 1 and measurements indicated that by August 1 the iodine-131 concentration had reached on tenth of its original value. What would be the rate constant for exponential decline [Hint: calculate b in equation (2)], and would would be the halftime for iodine-131 in Fern Lake?

Q2: Now suppose that 100 MBq had be released into the lake on July 1. What would be the concentration of iodine-131 in a typical trout's thyroid on September 1? [Hint: you need to use the b you calculated in Q1 and solve equation (3) for B(t) where the thyroid is the "source organ."]

Q3: If a trout's thyroid is 5% of its total body mass, and the dose rate to a trout's thyroid in Fern Lake on September 1 is 0.005 mGy per day, then what is the Dose Conversion Factor (DCF)  in mGy d-1 per Bq kg-1 for iodine-131 dose to the thyroid in trout? [Hint: You are going to need equation (4).]

[Note: You need no other information than what you've read in the two articles above, to answer these questions.]  

please try answering the questions from your own words and don’t just copy from the articles even citation doesn’t work. my professor want you to paraphrase not just copy from the article.

  • 11 days ago
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