1,000 Tons Of Polluted Fukushima Water Dumped In Sea

[caraher]

20. Breaking this down...

"So, bananas emit measurable levels of cesium 137? How about other long-lived radionuclides?"

I don't think anyone has claimed bananas emit any radioisotopes, nor that they naturally contain Cs-137. K-40 is main isotope of interest in bananas. (I'm sure there's some level of C-14 present as well.) But in any event, the point is well-taken - bananas contain different radioisotopes from reactor-contaminated water. How much that matters is harder to assess...

"Is the "natural" radioactivity in bananas lethal at the atomic or molecular levels?"

There's no evidence that "natural" radioactivity is any more or less lethal than radioactivity from artificial radioisotopes. I think Christopher Busby claims otherwise, but his position is a very lonely one. I'd be inclined to say "yes," simply because we do know single radioactive decay events can trigger potentially lethal cancers, and that mechanism is present for decay of K-40.

"You don't mention becquerels, curies, sieverts or millisieverts. You don't mention that cesium 137 is lethal at the atomic or molecular level. You don't mention that less than a dime-sized piece of cesium 137 can contaminate many kilometers of land."

For reference, a typical banana checks in at around 15 Bq of K-40 and maybe 100 g. The OP said the water deliberately released was checked to have under 30 Bq Sr-90 per liter, or per 100 g, so it would be 1/5 as radioactive per unit mass as a banana - if Sr-90 were the only isotope present. From the article it didn't seem like the Cs-137 concentration factored into their thinking at all, so it could be anything at all.

Of course, the biggest problem with pushing the banana radioactivity thing too hard (which I didn't always fully appreciate) is that it's not the case that eating N bananas results in N times the dose of eating one banana. It's all about sustained potassium levels, and if you ate enough bananas to increase the potassium concentration greatly, your body would just excrete the excess, making any elevated exposure brief. That's why they were concerned with Sr-90 - it does accumulate in bone and essentially never leaves the body - and less concerned with Cs-137 - it has a biological half-life of a few months.

A dime-sized piece of anything can "contaminate" an arbitrary area, depending on the level at which you declare it "contaminated." What activity level (in Bq) is a "dime size" of Cs-137? And what is the level of contamination you're talking about? (Is the concern the external dose reaching some threshold in dose per unit time, or just that the soil should have less than some number of Bq per square meter?)

I think that in the end, it's hard to say, really, that the water has a lower specific activity than a banana, because we only know about one isotope and because there was also an uncontrolled release, according to the article. It does seem plausible that most of the water was radioactive at a "sub-banana" level; it's just hard to say for sure given the information available.

All assuming, of course, that we can believe TEPCO or the Japanese government. That's the biggest wildcard here, and their track record is terrible!