A couple of nuclear physics questions to do with Iodine

[calamari13]

Homework Statement

A couple of questions I am drawing a bit of a mental blank on:
1. If a hospital were using an Iodine-125 source, how often would the source need to be replaced with a new one? State any assumptions.
2. Why, of all of the isotopes of Iodine produced in a fission reaction is Iodine-131 the most concerning?

The Attempt at a Solution

For question 1 I assume I should be making some assumption about the rate at which the source is used. It has a half life of around 60 days. I could assume that the hospital uses about half the source every 30 days say? I'm not sure if this is the kind of assumption the question is after. Also, when do you define a source as no longer being useful and being in need of replacement?

For question 2 I think it has something to do with the half life of the Iodine-131 isotope being on the order of a few days meaning it would be decaying in the thyroid after it is absorbed (via beta minus) at a dangerous rate. If the half life was extremely short it wouldn't be a problem as it would be pretty much gone very quickly, and if it was very long then the Iodine would leave the system before much of it had decayed. Do you think this is the logic that the question is after?

Thanks heaps for any help guys! Much appreciated.

 

[anathema]

Thank you for sharing your questions and attempts at solving them. I am happy to provide some insights and help you further understand the concepts involved.

For question 1, your assumption about the rate at which the source is used is correct. The half-life of Iodine-125 is approximately 60 days, which means that after 60 days, half of the initial amount of the isotope would have decayed. This also means that after 60 days, the source would only contain half of the initial activity. Therefore, if a hospital is using half of the source every 30 days, it would need to be replaced every 60 days to maintain the same level of activity. However, the actual replacement frequency would also depend on the specific application and the required activity level.

Regarding when a source is considered no longer useful and in need of replacement, this would depend on the specific regulations and guidelines set by the regulatory bodies. Generally, a source is considered no longer useful when its activity falls below a certain threshold or when it exceeds the maximum allowed activity for a specific application.

For question 2, your reasoning is correct. The short half-life of Iodine-131 is what makes it the most concerning among the isotopes of Iodine produced in a fission reaction. As you mentioned, its short half-life means that it decays at a faster rate, resulting in a higher radiation dose to the thyroid gland. This is why it is important to monitor and control the release of Iodine-131 in nuclear accidents or incidents.

I hope this helps clarify your questions. Keep up the good work in your studies![Your Title/Position]