which claim was made? the only claim I see is Japan asserting that it has nothing to do with the radioactive waste they are dumping into the ocean - I say the burden of proof is on them, since that is the claim they are making.
Where are you seeing Japan making that claim? From the article:
> The report noted that dead fish had begun washing ashore almost four months after the plant began discharging the water – which contains small quantities of the radioactive isotope tritium – into the Pacific.
> But no one has been able to confirm the cause. “The cause is unknown at the moment,” Mikine Fujiwara, a local fisheries official, told the newspaper. “We plan to sample the seawater at the site and examine it to uncover the cause.”
Or forbidding good sarcasm or jokes about it, because I don't know any PHD around me that don't have those in spades.