Extremely high radiation found in soil 40 km from Fukushima

[ReturnoftheDjedi]

Extremely high radiation found in soil

Japanese authorities have detected a concentration of a radioactive substance 1,600 times higher than normal in soil at a village, 40 kilometers away from the troubled nuclear power plant in Fukushima Prefecture.

The disaster task force in Fukushima composed of the central and local governments surveyed radioactive substances in soil about 5 centimeters below the surface at 6 locations around the plant from last Friday through Tuesday.

The results announced on Wednesday show that 163,000 becquerels of radioactive cesium-137 per kilogram of soil has been detected in Iitate Village, about 40 kilometers northwest of the plant.

Gakushuin University Professor Yasuyuki Muramatsu, an expert on radiation in the environment, says that normal levels of radioactive cesium-137 in soil are around 100 becquerels at most. The professor says he was surprised at the extremely high reading, which is 1,630 times higher than normal levels.

He warns that since radioactive cesium remains in the environment for about 30 years it could affect agricultural products for a long time. He is calling on the government to collect detailed data and come up with ways to deal with the situation.
Wednesday, March 23, 2011 19:02 +0900 (JST)
http://www3.nhk.or.jp/daily/english/23_28.html

[phantom power]

1. Does cesium concentrate up the food chain?

[DCKit]

4. Everything concentrates up the food chain.

Being on top is not always a good thing.

On edit: I heard some years ago that, if we were being honest, dead polar bears would be buried as toxic waste. Plankton and algae > fish > seals > polar bears.

[extropalopakettle]

18. Everything CAN'T concentrate up the food chain.

Just think about it. The total concentration of everything adds up to 100%. The concentration of mercury, or iodine, might increase further up the food chain, but if the concentration of everything increased, the total of all the concentrations of each substance would increase, which is impossible, since it always adds up to 100%

[leveymg]

2. Can someone please translate how becquerels translate into millisieverts?

Here's something I found on becquerels: http://www.ccohs.ca/oshanswers/phys_agents/ionizing.html

Radioactivity or the strength of radioactive source is measured in units of becquerel (Bq).

1 Bq = 1 event of radiation emission per second.

One becquerel is an extremely small amount of radioactivity. Commonly used multiples of the Bq unit are kBq (kilobecquerel), MBq (megabecquerel), and GBq (gigabecquerel).

1 kBq = 1000 Bq, 1 MBq = 1000 kBq, 1 GBq = 1000 MBq.

An old and still popular unit of measuring radioactivity is the curie (Ci).

1 Ci = 37 GBq = 37000 MBq.

One curie is a large amount of radioactivity. Commonly used subunits are mCi (millicurie), µCi (microcurie), nCi (nanocurie), and pCi (picocurie).

1 Ci = 1000 mCi; 1 mCi = 1000 µCi; 1 µCi = 1000 nCi; 1 nCi = 1000 pCi.

Another useful conversion formula is:

1 Bq = 27 pCi.

Becquerel (Bq) or Curie (Ci) is a measure of the rate (not energy) of radiation emission from a source.

[Statistical]

3. There is no direct relationship.

Sieverts is a measure of radiation. Radiation is energy like electricity (kWh), heat (BTU) or kinetic energy (horsepower).

Bq is a measure of the rate a radioactive material emits energy. Radioactive material isn't radiation, it produces radiation. Similar to an electrical generator produces electricity.

Radioactive material is far worse than radiation. Radiation doesn't "linger" it is instantaneousness. So if there is a reading of 20mSv and you aren't there then you didn't get any of that.

To convert the amount of mSv you would be exposed to from staying near a 1 Bq source you would need three other pieces of information
a) how much energy is release per decay (varies depending on the isotope)
b) how long were you exposed to the source.
c) how far were you from the source.

[ReturnoftheDjedi]

5. would you eat food grown in soil reading 163,000 Bq of Cesium 137?

[Statistical]

7. No. n/t

[kristopher]

11. Perhaps you could address the way ingesting particles affects those variables?

Variable c) from your list above, is what a linear variable?

What effect on variable b) does ingesting bring about?


(ETA) For example, compare particles 10 meters away with particles that are lodged in the body.


a) how much energy is release per decay (varies depending on the isotope)
b) how long were you exposed to the source.
c) how far were you from the source.

[FBaggins]

14. Here you go.

Variable c) from your list above, is what a linear variable?

Inverse square, not linear.

Which means that "inside the body" is MUCH more dangerous.

What effect on variable b) does ingesting bring about?

Controlled by the biological half-life of the material. In this case it's a couple months.

[kristopher]

15. Why don't you quantify that "much" for folks, given your habit of downplaying dangers...

...associated with radioactive fallout.

Your claim about "half life" is precisely that type of statement meant to downplay it.

Would you snort an itsy, bitsy teeny tiny cokespoon's worth of fallout?

[FBaggins]

16. Depends on what you're comparing it to of course

and it depends on the type of radiation.

given your habit of downplaying dangers ...associated with radioactive fallout.

I have no such "habit". What I do have a habit of doing is debunking wildly overinflated claims of risk by people who don't have a clue what they're talking about.

Your claim about "half life" is precisely that type of statement meant to downplay it.

Why is that? You don't think it's relevant how long you're exposed to a given radioactive element?

Would you snort an itsy, bitsy teeny tiny cokespoon's worth of fallout?

I guess that depends on what you mean by "fallout" and how much a "cokespoon" is. Is that like a teaspoon?

[leveymg]

13. Thanks for that concise answer.

Says a lot, and that's greatly appreciated.

[DLnyc]

6. Answer seems to be quite complicated, but here are some linkis and info

I'm no expert on this, but I've been trying to self-educate myself a little bit.

Becquerel seems to mean 1 radioactive decay per second. A Sievert seems to be a measure of biological damage. Since different radioactive materials give off different characteristic energies for each decay, different materials do different levels of damage per decay. Note also that a Sievert is an AMOUNT of dose, to be distinguished from a Sievert per hour (say) which is a RATE of dose.

Good (partial) answer from someone who appears to know what they are talking about here:
http://www.radprocalculator.com/FAQ.aspx (pick 3)
"This is not so much a FAQ but a search term that we see every day when viewing website statistics. Many people are searching for How do I convert activity to dose or dose-rate? We think that conversion is the wrong term. Conversion usually means, what number do I multiply Ci and Bq by to obtain R, rad, rem and Gy or Sv? What you should be asking is how do a I calculate dose-rate or dose for a given activity of an isotope? It is indeed a complicated calculation, not a simple conversion. There is no number that you multiply Ci and Bq by to get R or rad and Sv or Gy. Different isotopes emit different energy gammas and some emit more than one gamma. At the same rate of emission or decay, an isotope that emits more and higher energy gammas will give a higher rem/hr or Sv/hr. Ci and Bq are based on dpm/sec (dps). Consider the same emission rate (dps) for Cs-137 and Co-60. Co-60 will give you a higher dose-rate and dose because it emits two gammas above 1000 keV where Cs-137 emits only 1 gamma at 661.8 keV. Obviously Co-60 is emitting more electromagnetic energy per decay than Cs-137 which will give one a higher dose-rate in R/hr or Sv/hr. Also, the dose and dose-rate varies with the distance from the source. You cannot convert from Ci and Bq to R, rem or rad and Sv or Gy. You must do a complicated calculation on an isotope by isotope and a distance by distance basis. The formula can be found here. If you can eliminate the word "convert" from your question and replace it with "calculate", Rad Pro Calculator can give you your answer, here. Rad Pro Calculator also calculates dose-rate in rad/hr and Gy/hr from beta emitter activity here. "

Using the calculator I got, for each 163000 Bq of Cs-137 at a distance of 2 meters (typical human height):
http://www.radprocalculator.com/Gamma.aspx
163000 Bq of Cs-137 at 2 Meters Bq Meters mSv/hr Enter or Select Isotope Select Calculation . . .
get 3.089436E-006 milliSievert per hour (means about 3 times 10 to the minus 6 milliSievert, or like .003 microSieverts, I think).
Doesn't sound like much, but there are MANY kilograms of soil, each containing 163000 Bq, so I guess you would have to sum over those (but each at different distances)??

This isn't a very clear answer, but maybe it's a start. Perhaps some of those here who seem to have expertise in the area of radiation effects on humans and other biological entities could give some clearer numbers.

[Statistical]

8. To further explain your calculation.

You are right the amount if low in radiation (actual energy). If the only danger was that you would be exposed to that radiation at 2 m distance it wouldn't be much of a threat.

The larger danger is that you would EAT the Cs-137 (or possibly inhale it if you are the farmer). Then it would sit in your body producing radiation. The dose rate wouldn't be .003uSv per hour because it is no longer 2 meters away. Calculating dose for material inside the body is difficult due to the fact that cells at various distances would accumulate different dosages. Some types of cells are more vulnerable to radiation than others so the location where the material ends up matters a lot. Say just for illustration the average distance was 1 cm. At 1 cm you would rack up .12mSv per hour not 0.03uSv.

If it stayed in your body for a decade that is .12mSv per hour continually. This is why the biological half life is more important than the actual half life for material that can be ingested. The longer it remains in your body the more accumulated dose you get.

Radiation is bad but small amounts don't have much potential to hurt you. Even in larger doses *most* but not all people will have no ill-effect.

Radioactive Material especially longer lived isotopes live Cs-137 are much more of a danger. Think of them as radiation generators. If some gets inside you it will generate radiation continually for very long time and the accumulated dose can get very high.

[phantom power]

9. Aren't these elements also chemically toxic, at least in certain chemical forms?

[Statistical]

10. Some definately are.

Many fission product isotopes are heavy metals so the toxicity is similar to other heavy metals like lead and mercury.

[DLnyc]

12. Yes, thank you. Such biological effects are clearly the important issue.

I was simply trying to make sense of the relationship between Becquerels and Sieverts. But certainly ingesting these materials is a much higher source of danger than simply being physically close to them.

[DLnyc]

17. Oops, Dupe, sorry