Wow…I did not know that there was such a lake.
I can not make difficult explanations in English…I can only talk about simple things, but I have studied various kinds of radioactivity.

Nuclear bombs like Hiroshima are powerful, but radiation is quickly disappearing, So neither that lake nor Hiroshima has little radioactivity now.

The problem is the nuclear power plant.
Radioactivity of nuclear plants such as Chernobyl and Fukushima will gradually accumulate around them…Sea, River, Soil,Vegetables, fish.
It accumulates in that place long, so it will be difficult to remove. It is the same for human body.
So The radiation accumulated in the body affects the people of the next generation.
Actually, That is happened to people in Chernobyl, so the same will happen to Japanese people from now on.

That is not a problem for Japanese only.
Radioactivity in the surrounding creatures and ocean current will threaten people in other countries.
Therefore, we Japanese people have to deal with this situation responsibly.
But I always talk…Japanese people believe in the media and ignore it😢

Anyway I appreciate your wonderful post.
And Thank you for listening to the long story!