Calculating safe levels of radioactivity

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    Levels Radioactivity
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Discussion Overview

The discussion revolves around calculating the time it takes for radioactive elements, specifically Cesium-137, to decay to levels considered "safe." Participants explore the mathematical models related to radioactive decay, the definition of "safe" levels, and the implications of initial activity levels in various contexts, including environmental contamination.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning
  • Experimental/applied

Main Points Raised

  • Some participants emphasize the need to define "safe" levels and understand the initial activity of radioactive materials before performing calculations.
  • There is a suggestion that the decay formula can be applied to both the decay of the element and its activity, as both decay exponentially.
  • One participant proposes calculating the waiting time for contaminated spinach to reach safe levels based on initial and limit activity values.
  • Concerns are raised about the variability of cesium concentrations in drinking water, with some participants noting that values can differ significantly based on the source.
  • Some participants express confusion regarding the relationship between cesium concentration in water and its activity, questioning how to accurately measure or estimate these values.
  • There is a discussion about the implications of different scenarios, such as contamination from a nuclear meltdown versus natural sources, and how these affect calculations.
  • One participant argues that accumulating pure Cs-137 is always dangerous, while another emphasizes the importance of understanding how cesium distributes in the environment.
  • Participants express uncertainty about where to find reliable data for cesium contamination levels in water.

Areas of Agreement / Disagreement

Participants generally agree on the importance of defining "safe" levels and the need for accurate initial activity measurements. However, there are multiple competing views regarding how to approach the calculations and the variability of cesium concentrations in different contexts, leaving the discussion unresolved.

Contextual Notes

Participants highlight limitations in their understanding of cesium activity in water, the variability of contamination levels, and the need for empirical data to support calculations. There is also a recognition that different scenarios yield different results, complicating the analysis.

  • #31
mfb said:
So what do you get for the activity per gram if you convert 1.8 kBq/m3 to Bq/g?
0.0018 Bq/g
 
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  • #32
Right. A factor 100 below the 0.2 Bq/g limit.
 
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  • #33
mfb said:
Right. A factor 100 below the 0.2 Bq/g limit.
...

Help

Please
 
  • #34
What? You figured out that all the reported values in this thread were below the safety limits all the time.

If you want to calculate some time, you'll need water with more contamination. Or take something else, e. g. mushrooms in Bavaria.
 
  • #35
mfb said:
What? You figured out that all the reported values in this thread were below the safety limits all the time.

If you want to calculate some time, you'll need water with more contamination. Or take something else, e. g. mushrooms in Bavaria.

OK. I have looked now at examples from Fukushima Daichii 2011, but they're reporting the levels to now be near identical to pre incidental levels. Considering this is the largest incident since Chernobyl, is it safe to assume there have been no other incidents where water contamination was worthy to investigate?

I am considering just making a scenario and analysing that.
 
  • #36
Water contamination is one of the first things to go down, simply because water flows away and carries the radioactivity away with it.

Mushrooms are more promising, they tend to accumulate some elements that have long-living radioisotopes.
 
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