eli5: Fukushima fish with 180 times legal limit of radioactive cesium fuels water release fears


What does this mean? Is it really safe for human to consume the fish with 180 times legal limit of radioactive cesium fuels water?
What is the radioactive cesium fuels water ?

In: 3

It means nothing really, 18,000 Becquerels = 18,000 decay events per kilogram in this case. That probably sounds like a big number, but translated into a more useful metric, it’s the equivalent of eating between 4-18 Brazil nuts.

The syntax wasn’t “cesium fuels water” it’s “cesium fuels water release *fears*” so it’s saying that people are scared about it, not that there’s something called cesium fuels water.

It’s probably bad in an absolute sense, but also probably not as bad as you would think given headlines like that.

Well it certainly won’t be recommended to eat such fish. This highlights one of the core dilemmas.

By not diluting the contaminated water in the ocean and also not having a 100% foolproof way of disallowing wildlife like fish and birds into the area, the risk of having high concentrations in a few animals increases. Since cesium-137 has a half life of 30 years, it might take a few centuries before the radioactive contaminated water becomes relatively safe.

Diluting the contaminated water by releasing it into the ocean is fiercely opposed by many and yet may be the most practical solution. 1m tons of more radioactive water will fairly quickly be diluted into background radiation by the ocean (the ocean is a HUGE reservoir of water). So it becomes very unlikely that any fish will contain as high as 180x the legal limit. And that risk should fall off very quickly over time – just due to natural lifecycles.

So first off, this fish is apparently a *spectacular* outlier, being an order of magnitude above those other record fish the article mentions, which together were three out of 22 fish found above that legal limit of 100 Bq (the article neglects to mention how many fish were sampled *in total* — is this 22 out of 100, 22 out of 10,000…?).

Secondly, you’re kind of reading the title wrong; the “fuel” part relates to “fueling fear”, not something like “nuclear fuel”.

Having said that, the cesium-137 all came from the initial 2011 disaster. The water release plans that are somewhat controversial now are about cooling water that has built up ever since; this cooling water, after decontamination, still contains a very small amount of tritium (hydrogen-3 if you will). The plant operator is running out of space at the site and eventually needs to take that water somewhere. It’s clean enough that, especially once diluted by the ocean’s worth of water out front of the plant, the activity of that tritium is a non-issue and has been approved by the IAEA.


finding a few fish who gulped up some cesium-137 from the original disaster has essentially nothing to do with the present-day minimal tritium contamination in the water they plan to release. The former shouldn’t fuel any fears about the latter. Plus, [as another comment rightly points out](https://www.reddit.com/r/explainlikeimfive/comments/15drb54/eli5_fukushima_fish_with_180_times_legal_limit_of/ju3ivfl/), this one record fish isn’t even dangerous in practice. For more political reasons, though, china in particular seems very happy to grab on to headline-worthy radiation scares.