What is the specific activity of the air inside the sealed warehouse?

Click For Summary

Discussion Overview

The discussion revolves around calculating the specific activity of air inside a sealed warehouse after a sample of 85Kr gas escapes. The focus includes theoretical considerations, mathematical approaches, and the implications of gas dispersion within a volume.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant seeks guidance on how to calculate the specific activity of the air after the escape of 85Kr gas.
  • Another participant notes that specific activity is a function of mass and that the activity per unit volume will decrease if the gas disperses in the air.
  • A participant provides a calculation for specific activity based on mass, presenting a formula and numerical results.
  • A later reply emphasizes the need to consider the dilution of the Kr gas in the air when calculating specific activity, suggesting that the mass of air must be included in the calculations.
  • Participants discuss the importance of the basis or units of specific activity, questioning if there is guidance in textbooks regarding this aspect.

Areas of Agreement / Disagreement

Participants express differing views on whether the specific activity should be calculated based solely on the Kr gas or if the dilution in air must be considered. The discussion remains unresolved regarding the appropriate method for calculating specific activity in this context.

Contextual Notes

There are limitations regarding the assumptions made about gas behavior, the definitions of specific activity, and the mathematical steps involved in the calculations. The scope of the discussion does not clarify how to reconcile the differing approaches to specific activity.

xamy
Messages
26
Reaction score
0
Can anyone please guide me how to find solution of this problem

A 0.2-g sample of 85Kr gas, which decays into stable 85Rb, is accidentally broken and escapes inside a sealed warehouse measuring 40×30×20 m. What is the specific activity of the air inside?
 
Engineering news on Phys.org
Specific activity is a function of mass, so the mass shouldn't change. The activity per unit volume will decrease if the gas disperses in the air/volume.

Also, Kr is a heavy gas and will tend to settle, although some would mix in the air.

The activity is given by the product of the decay constant and the number of atoms of a given species. The specific activity is simply the activity divided by the mass.
 
Thankyou for your reply

I have found the specific activity as a function of mass. But how to find the specific activity according to the volume mentioned in the question?
SA = 4.17×1023/ MT

SA=4.17×1023/ (85)(10.72x365x24x3600)

SA=14.5116TB q/g

1g=14.5116TBq

0.2g=2.902322927TBq
 
Using the theory that you have explained I have found the answer. Thank you so much
 
Caveat - if the question is asking for specific activity in the air, as opposed to specific activity if the Kr gas, then one would have to consider the dilution of the Kr gas in the air, and consider the mass of the air.

Activity could be given in terms of activity per volume of atmosphere, or mass of air, so one would consider the activity from the mass of the Kr-85, but then divide by the mass or volume of the combined air+Kr gas.

So the basis of the activity is important.

Is there any guidance in one's textbook as to the basis or units of the specific activity?

FYI - http://hpschapters.org/northcarolina/NSDS/krypton.pdf
 

Similar threads

Replies
8
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 19 ·
Replies
19
Views
6K
  • · Replies 2 ·
Replies
2
Views
6K
  • · Replies 19 ·
Replies
19
Views
10K
  • · Replies 1 ·
Replies
1
Views
10K
  • · Replies 8 ·
Replies
8
Views
5K
  • · Replies 9 ·
Replies
9
Views
29K