Radiation Exp: Converting μCi to dps & Understanding Half-Lives

In summary, the experiment measured the dose rate from various samples and found that paper did not protect against radiation. However, the sources contained a different number of radioactive atoms and therefore the activity in dps varied.
  • #1
Von Neumann
101
4
Question:

Recently I've conducted an experiment measuring the dose rate (in μR/h) from various samples (Ba-133, Cs-137, Co-60), at varying distances. In determining the efficiency of paper as a shield, it is required to convert the activity of the source to units of dinsintegrations/second (dps). On each of the sources was a label that stated the half-life. Additionally, each source said "1 μCi". So therefore, since 1 μCi = 3.7 x 10^4 dps, that would be the activity in dps. Correct? However, I don't understand how all of the sources could have the same activity in dps, but have different half-lives.

Note: the half-lives given on the sources for Ba-133, Cs-137, and Co-60 are 10.5, 30.2, and 5.27 years, respectively.
 
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  • #2
In determining the efficiency of paper as a shield, it is required to convert the activity of the source to units of dinsintegrations/second (dps).
Why? It should be sufficient to know the measured rate with and without shield.

However, I don't understand how all of the sources could have the same activity in dps, but have different half-lives.
Simple: they contain a different number of radioactive atoms.

Additionally, each source said "1 μCi". So therefore, since 1 μCi = 3.7 x 10^4 dps, that would be the activity in dps. Correct?
If the sources are new. Activity goes down with time, while the labels do not change.
 
  • #3
Yes that does seem to be quite obvious, sorry.

Furthermore, I am looking to estimate my total extra exposure in mR (dose above background) due to performing the experiment by taking into account how long I was near each source, the strength of the source, and its approximate distance from me.

If I take my distance as 0 inches (since I was holding each source throughout experiment) and the time as roughly 10 minutes per source, how would I go about doing this? Perhaps, since I have the measured values of the dose rate at 0 inches from each source, could I multiply the dose rate by the amount of time in order to get this result?
 
  • #4
That should give a reasonable upper limit on your dose rate. Even if you touched the radioactive part of the probe (I hope you did not), not all decay products have hit you.
 
  • #5
Yes, I was holding the sources. However, I don't believe my professor would have the class conduct a lab that would endanger our health in any way. The sources were in specially prepared cases from Oak Ridge National Laboratory.
 

1. What is radiation and why is it important to understand its effects?

Radiation is the energy emitted from unstable atoms as they decay. It is important to understand its effects because exposure to high levels of radiation can be harmful to living organisms, and it is commonly used in various industries such as medicine and energy production.

2. How is radiation measured and what are the units used?

Radiation is measured using a unit called the curie (Ci) or its smaller unit, the microcurie (μCi). Another commonly used unit is the becquerel (Bq). The curie is a measure of the rate of decay, while the becquerel is a measure of the number of decay events per second.

3. What is the relationship between μCi and dps?

The relationship between μCi and dps is that 1 μCi is equal to 37,000,000,000 (37 billion) decays per second (dps). This conversion factor can be used to convert between the two units.

4. What is a half-life and how does it relate to radiation exposure?

A half-life is the amount of time it takes for half of the atoms in a sample to decay. It is a measure of the stability of a radioactive substance. In terms of radiation exposure, a shorter half-life means that the substance is more radioactive and will emit more radiation in a shorter period of time.

5. How can we use half-lives to calculate the decay rate of a substance?

To calculate the decay rate of a substance, we can use the formula N = N0(1/2)t/h, where N is the final number of atoms, N0 is the initial number of atoms, t is the time elapsed, and h is the half-life of the substance. By plugging in the appropriate values, we can determine the rate at which the substance is decaying.

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