The ALI for inhalation of I-131 is determined by the nonstochastic limit on dose
ID: 180850 • Letter: T
Question
The ALI for inhalation of I-131 is determined by the nonstochastic limit on dose
equivalent to the thyroid. If as a result of a single intake of 4.32 x 103 Bq, the thyroid will
receive an average dose of 225 mrad of beta during the next 50 years.
a.What is the committed effective dose equivalent to the thyroid?
b.Based on the above information, what is the ALI for I-131 by inhalation?
c.What is the corresponding derived air concentration?
d.The person was monitored in a whole body counter over a period of 6 weeks. The
net counts over this time are shown below. From these data, determine the
metabolic half-life of iodine in the thyroid.
Time(days) 0 14 28 42
Net Counts 14,281 3,825 1,066 297
Explanation / Answer
4.32x103 Bq = 0.108 microCi
a). Committed effective dose equivalent (CEDE) to the thyroid is
5 rem x (0.108 microCi) = 0.0108 rem
50 micro Ci
b), ALI for I-131 by inhalation is
50 micro Ci
c) Corresponding derived air concentration is
50 microCi/ Litre
d). Half life of Iodine in Thyroid is nearly 7 days
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