Fukushima Daiichi: Cesium-137 and Iodine-131 levels in seawater near plant high but decreasing

Radiation measurements Saturday March 26 reported by IAEA

330 m east of the discharge points of Units 1 - 4.

74 000 Bq/liter of iodine-131

12 000 Bq/liter of cesium-137

12 000 Bq/liter of cesium-134

Radiation measurements Sunday March 27 reported by IAEA

330 m east of the discharge points of Units 1 - 4.

11 000 Bq/liter of iodine-131

1 900 Bq/liter of cesium-137

NHK reports that MEXT has been collecting seawater samples at 4 locations 30 kilometers off the coast of Fukushima Prefecture since March 23rd. The latest data are for March 27.

1.5 to 3.9 Bq/liter of cesium-137  - Sunday March 27

5.4 to 15 Bq/liter of iodine-131 - Sunday March 27

The amounts represent 1,000 to 2,600 times the levels measured in the same area 2 years ago.

But the current levels are only one-fifth to one-tenth of those detected on March 23rd.

What does this mean

For comparison the radioactivity of coffee is about 1000 Bq/kg.  The long term risk is that some organisms can concentrate these radioactive substances, especially cesium-137 which has a half life of about 30 years.

Comments

[David Chanin]

"the radioactivity of coffee is about 1000 Bq/kg"? That's quite an astounding claim to make, since EU standards for radiation in food range from 300 to 1000 Bq/kg, which would put "coffee" at very the top. Hopefully, that's from "dry weight" of beans and not the wet weight of resultant brewed coffee :>

First of all, the most radioactive food is widely known to be banana fruit because of its K-40 content due to high potassium levels. And the same is true for the natural radioactivity in soil (dominated by K-40) unless dominated by U and Th. See
http://baranwal.org/Research_files/postr_sinp.pdf

Pray tell where this radioactive coffee can be found so I can add it to my collection of harmless NORM used to demonstrate radiation detection with my Ludlum 3 using their 44-9 pancake probe.

[Geoff]

According to the Royal Society of Chemistry (http://www.rsc.org/images/number6_tcm18-17768.pdf)

Typical radioactivity levels in Bq per Kg
are:-
Soil (Berkshire) 1,000
Human Body 4,000
Coffee 1,000
Brazil Nuts 460
Tea (Indian) 630
Fertiliser 2,200
Grass (Dried) 600
Coal (UK) 300

I am sure you are right that that refers to beans, not brewed coffee

[Kurtis Kunesh]

With respect, we consider this comparison to be utterly misleading. Why? Radiation and contamination are not the same thing. Taking a flight will expose one to cosmic radiation not radioactive contamination. When radioactive isotopes enter into water, crops, milk that leads to radioactive contamination. Contamination occurs when material that contains radioactive isotopes is no longer contained. It is important to remember that radiation cannot spread or get "in" or "on" people; rather it is radioactive contamination that can do precisely that. Here lies the essential difference between the two.

Radioactive contamination and radiation exposure occur only if radioactive materials are released into the environment as the direct result of a nuclear accident, an event in nature -- such as ground radiation with radioactive isotopes -- or an act of war involving nuclear devices or radioactive isotopes. Such a release may expose living beings and contaminate their surroundings and their environment.

Radioactive contamination occurs when radioactive material is deposited on or in an object or a living being. Radioactive materials released into the environment can cause air, water, surfaces, soil, plants, buildings, people or animals to become contaminated. A contaminated living being has radioactive materials on or inside their body.

Read more: http://www.businessinsider.com/why-radiation-and-contamination-is-like-comparing-apples-and-oranges-2011-4#ixzz1ROOwq0gT