What is the Difference Between Becquerel and Sievert in Measuring Radioactivity?

  • Thread starter kiskrof
  • Start date
In summary, the conversation discusses the difficulties in understanding and interpreting units of measurement in the field of nuclear physics, particularly the Becquerel and the Sievert. While the Becquerel measures the rate of radioactive decay, the Sievert measures the absorbed dose of radiation in living organisms. Both units are precise but have limitations in providing a complete understanding of the effects of radiation. The conversation also mentions the different half-lives and accumulation rates of radioactive elements, as well as the challenges in accurately measuring and estimating radiation exposure in real-life situations. Ultimately, Becquerels and Sieverts are complementary measurements that provide different perspectives on the impact of radiation.
  • #1
kiskrof
13
1
To anyone new to the field of nuclear physics, the units are positively nonplussing. For example, I have just understood that the Becquerel (desintegration per second) is not very significant if you do not tell what kind of Becquerel you are talking about, since different desintegrations yield different quantities of energy.

Furthermore, we do not absorb different products the same way. For example,if we compare Cs137 (512 keV) and I131 (606 keV) beta decay energies they are similar. However, this 2011 article (http://www.bloomberg.com/news/2011-03-21/japan-sets-safe-limits-for-consuming-radiation-contaminated-food-table-.html ) tells us "The prescribed safe limit for I-131 in vegetables is set at 2,000 Becquerel (Bq) per kilogram and 500 Bq/kg for radioactive cesium."
I do not know why cesium is supposed to be more dangerous, but I guess it accumulates more in the body. It probably has something to do with the different half-lifes too (about a week for Iodine and 3 decades for Cs 137). I guess that if your body incorporates I 131, you are radioactive for a little while, if it incorporates Cs 137, you are radioactive for decades.

So my conclusion is, wherever I read "Becquerel" in an article about Fukushima or Tchernobyl, I do not really know what it means. I have never read any article that tried to make me aware of the fact that some Becquerels are more equal than others.

The energy absorbed by an object is measured in Grays (joules per kg). In the case a living organisms, alpha particle are considered 20 times more harmful thant alpha or beta. So if you receive 10 grays of alpha and 10 grays of beta, you get 210 sieverts of "effective dose". Why is the multiplication factor 20 and not 19 or 21? 20 is a round figure. We are talking about a rough estimate. So any measurement in Sieverts is by definition not very precise. For example, it does not make any sense to talk of "161 millisieverts", just say "160" to account for the lack of precision.
In the wikipedia article about the most radioactive town in the world, Ramsar, Iran, I read:"Record levels were found in a house where the effective radiation dose due to external radiation was 131 mSv/a". Such a figure is puzzling, since no one stays home 24h a day and I do not think the effective "home time" of the inhabitants of the building could be measured with very accurate precision.
The more I read things about radioactivity, the more I come across figures in sieverts that I have some reason to doubt. When you live in a radioactive environments, you might ingest, drink or inhale radioactive elements, or get affected by gamma rays that can travel even through walls. So estimates of the sievert result are often very difficult.

In conclusion, I think Becquerel measurements are precise but not very informative, while sievert measurement are informative, but not precise.
 
Last edited by a moderator:
Physics news on Phys.org
  • #2
kiskrof said:
In conclusion, I think Becquerel measurements are precise but not very informative, while sievert measurement are informative, but not precise.

Bq and Sv measure different things. Like miles driven and gallons of gasoline used. They are proportional and both well-defined, although the constant of proportionality depends on the system: like driving an econo-box vs. a truck.
 

Related to What is the Difference Between Becquerel and Sievert in Measuring Radioactivity?

1. What is the difference between Becquerel and Sievert?

Becquerel (Bq) and Sievert (Sv) are both units used to measure radiation. Becquerel measures the rate at which a radioactive substance decays, while Sievert measures the biological effect of that radiation on living organisms. In simple terms, Becquerel measures the amount of radiation emitted, while Sievert measures the potential harm of that radiation.

2. Which unit is used to measure the amount of radiation in a radioactive substance?

The Becquerel (Bq) is used to measure the amount of radiation in a radioactive substance. It is equivalent to one decay per second.

3. How does the conversion from Becquerel to Sievert work?

The conversion from Becquerel (Bq) to Sievert (Sv) depends on the type of radiation and the energy of the radiation. For example, for gamma radiation, 1 Sievert is equal to 1 Joule per kilogram of tissue exposed, which is equivalent to 1 Gray (Gy). This means that 1 Sv = 1 Gy x Quality Factor. The Quality Factor takes into account the type of radiation and its potential harm to living organisms.

4. What is the significance of Becquerel and Sievert in radiation safety?

Becquerel and Sievert are important units in radiation safety as they are used to measure and regulate exposure to radiation. The International Commission on Radiological Protection (ICRP) sets limits for radiation exposure in terms of Sieverts, based on the potential harm of that radiation. These limits are used to ensure the safety of individuals working with or around radioactive substances.

5. Are there any other units used to measure radiation besides Becquerel and Sievert?

Yes, besides Becquerel and Sievert, other units used to measure radiation include Gray (Gy), which measures the amount of energy absorbed by an object, and Roentgen (R), which measures the ionization of air caused by radiation. However, Becquerel and Sievert are the most commonly used units for measuring radiation in the scientific community.

Similar threads

  • High Energy, Nuclear, Particle Physics
Replies
2
Views
871
  • High Energy, Nuclear, Particle Physics
Replies
6
Views
1K
  • High Energy, Nuclear, Particle Physics
Replies
3
Views
1K
  • Introductory Physics Homework Help
Replies
12
Views
385
  • High Energy, Nuclear, Particle Physics
Replies
10
Views
2K
  • Nuclear Engineering
Replies
8
Views
7K
  • High Energy, Nuclear, Particle Physics
Replies
9
Views
2K
  • High Energy, Nuclear, Particle Physics
Replies
2
Views
876
  • Introductory Physics Homework Help
Replies
7
Views
5K
Back
Top