しょうゆ Soy Sauce

Posted on September 27, 2012

UC Berkeley Nuclear Engineering Air Monitoring Station has tested a sample of soy sauce

purchased in a local grocery store. The soy sauce was labeled as a product of Japan. No radioactive isotopes were detected that can be traced to the reactors at Fukushima. For comparison, the activity concentration of Potassium-40 (K-40) in the sample was approximately 100 Bq/L.

カリフォルニア大学バークレー校のモニタリングステーションは、地元のスーパーで購入したしょうゆのサンプルを検査しました。そのしょうゆには、日本産と記したラベルが張られています。福島由来の放射性各種は何も検出されませんでした。これに対し、カリウム４０は約１００ｂｑ/L(kg)でした。

Soy Sauce Sample

Collection Time(採取日）: 8/21/2012
Sample Volume(サンプル量）: 1.08 liters
Counting Time(測定時間）: 514,760 sec.
Energy Resolution(エネルギー分解能）: 2 keV (at 1461 keV)
Cs 134 Less Than MDA (0.29 bq/kg)
Cs 137 Less Than MDA (0.32 bq/kg)
セシウム検出限界（ＭＤＡ）以下

Collection Date	Sample Volume	I-131	I-132	Cs-134	Cs-137	Te-132
08/21/2012	1.08 L	< MDA [0.027bq/L]	< MDA [0.044bq/L]	< MDA [0.029bq/L]	< MDA [0.032bq/L]	< MDA [0.065/bq/L]

"MDA" is the estimated minimum detectable activity for a given isotope in the detector.


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自然放射能の内部被曝について
落合栄一郎氏の「原爆と原発」(P106)より
(Ｅｎｇｌｉｓｈ　ｔｒａｎｓｌａｔｉｏｎ　ｆｏｌｌｏｗｓ　ｂｅｌｏｗ）

そして、挙動の類似しているセシウムとカリウムは、「サイズその他に違いがあり、その違いが生体内での挙動の違いとして現れることがある。」とあります。

つまり、いつも一定の割合で「体全体に放射性物質がおよそ一様に分布している」Ｋ－４０やＣ－１４からの細胞１個あたりの被曝はほんのわずかだけれど、食事に含まれる人工的放射性各種であるセシウムの場合は、体に入って「直ちにに体中に分散する事がなく」、ある特定の場所に定着する事が問題で、その近辺の細胞が、かなりの放射性粒子を受けてしまう。

ということのようです。



About internal exposure from Natural Radiation
Source from "Atomic Bomb and Nuclear Power Plant"
written by Eichiro Ochiai

K-40 and C-14 exist inside of every creatures including human, as they are essential for us. They always exist in our body. In human's body,  potassium exists 2200ppm, 2.2g/kg. 93% of them are K 39 which is nonradioactive, and about 0.012% are K40 which emits β radiation. There are 2.6 x 10^-4 g of K-40 per 1kg. It means 66Bq radiation are emitted per second, which can be converted to about 0.17mSv/y.

Carbon is one of the main components of our organism. 194g/kg are contained in our body. 2x10^-10 g of them are C-14. It can be converted to about 0.03mSv/y. Adding 0.17mSv/y of K-40 to it will be total of 0.2mSv/y. In this book, I estimated 0.7mSv/y as an annual dose of internal exposure by adding the dose from various source of other natural radiation existing on our planet. It is unclear how close this estimate is to the actual, though. The amount of radiation exposure except this 0.2mSv also varies depending on the environment and locations, so each individual's dose also vary.

He also wrote, radioactive elements of Cs and K behave similarly, but "they are different in size which may cause the different behavior in our body. "

K40 and C14 "are distributed equally in whole body", and it limits the dose of exposure per cell to very small amount. But man-made radioactivity like Cs "would not be dispersed immediately after they are absorbed in the body", and the problem is that they would stay at specific parts, which allow the cells around to get high dose of radiation.

元素を組織的に配列した元素の周期律表

Periodic Table

埼玉大学名誉教授・市川定夫氏(放射線遺伝学)の講義