How to Calculate the Activity of 0.000001 mL Rn-222?

[Elbirdo]

TL;DR Summary: What is the activity of 0.000001 mL Rn-222?

Trying to do a quick calculation of the activity of 0.000001 mL of Rn-222 and I'm not ending up with what I expected.

 

[mfb]

We can't tell what went wrong if you don't show your calculation. What did you get and how, and how does that differ from your expectation?

I moved the thread to the homework section as it's homework or at least homework-like.

 

[Elbirdo]

It isn't homework. I was hoping someone would provide an answer and I would just reverse it back. Trying to determine Rn-222 activity released per day from a 1 Ci Ra-226 source. Based off a release rate of 0.000001 mL Ra-222 per day per Ci of Ra-226 and density of radon I came up with 1.5 Ci of Rn-222 but that doesn't seem right.

 

[berkeman]

It isn't homework. I was hoping someone would provide an answer and I would just reverse it back.

So this is for your work? What kind of work do you do? Are there no experts/Mentors at your work who could help you with this question?

 

[Elbirdo]

So this is for your work? What kind of work do you do? Are there no experts/Mentors at your work who could help you with this question?

Is this not the right place to ask a question?

 

[berkeman]

PF is a great place to ask questions. We do have it in our rules that all schoolwork-type questions need to go in the Homework Help forums. You will get good replies in both the technical forums and the Homework Help forums, but we need to keep those two types of questions separated.

 

[berkeman]

And you didn't answer my question -- is this for your work?

 

[Elbirdo]

And you didn't answer my question -- is this for your work?

Does it matter? Your response and follow-up question are totally irrelevant. That's why I didn't answer your question. Obviously I posed it on this forum because I either don't have a resource available at this time or maybe no one could help.

 

[berkeman]

Does it matter? Your response and follow-up question are totally irrelevant. That's why I didn't answer your question. Obviously I posed it on this forum because I either don't have a resource available at this time or maybe no one could help.

It matters because we have the Homework Help rules for a reason. We do not help students cheat here at PF. Thread is closed.

 

[berkeman]

After a PM conversation, thread is reopened for now. OP will post more details about his question soon.

 

[Elbirdo]

I don't have my notes on me. Calculating Rn-222 from Ra-226 sources for an effluent concentration on a daily basis. Used number of atoms in 10 Ci of 226 to get disintegrations to Rn-222 and then converted that by ratio to Ci of Rn-222. I think I ended up with something like 11.4 uCi which sounds right to me today as opposed to what I had calculated last night from different parameters a service tech from "blank" had given me.

 

[mfb]

10 Ci gives you the Rn-222 production rate directly.

In equilibrium, there will be one Rn-222 decay per Ra-226 decay (assuming the Ra-226 rate stays constant, a really good approximation here). If you start with a sample of only Ra-226 then the initial Rn-222 activity will be lower (starting at 0) and approach 10 Ci over the following days to weeks, but it can never exceed that value.

 

[Elbirdo]

Correct if it were accumulating, but for this scenario we are assuming it will be "released" so there won't be a buildup to equilibrium over the 28 days it takes to get to 99%.

 

[mfb]

How do you define an "activity released per day"? An activity is an instantaneous value.
If you discard some Rn-222 then the activity should be even lower, and certainly not exceed 10 Ci.

 

[Elbirdo]

Looking at effluent concentration of a gas. uCi/mL of air out of a stack. So you would need to look at number of disintegrations in that time period over air volume. At least that was what I was thinking in my conclusion from post #11.

 

[Elbirdo]

Definitely not looking at Ci levels here for sure. No where near 10 Ci equilibrium.

 

[Elbirdo]

Activity is a rate so seems easy to determine an activity released in a day as opposed to it being an instantaneous value. DPS, DPM, etc....