Japan: Harassment calls from China on Fukushima water release 'regrettable'

Japan's top government spokesman has said it was extremely regrettable that there were many instances of harassing phone calls from China regarding the release of treated radioactive water from the Fukushima nuclear power plant into the Pacific.

"A lot of harassment phone calls believed to be originating from China are occurring in Japan ... These developments are extremely regrettable and we are concerned," Chief Cabinet Secretary Hirokazu Matsuno told a regular news conference.

Japan on Thursday started the water discharge, a key step in decommissioning the Fukushima plant, which suffered triple meltdowns after being hit by a tsunami in 2011 following a powerful earthquake.

China's foreign ministry did not immediately respond to a Reuters request for comment on the Matsuno remarks.

China has repeatedly and strongly criticised the release plan, banned Japanese seafood imports and cast doubt on the expert assessments that concluded the operation poses no harm to the environment.

Nigel Marks, a physics professor at Australia's Curtin University, said the released water contains negligible amounts of radioactive tritium.

"The Pacific Ocean contains 8,400 grams of pure tritium, while Japan will release 0.06 grams of tritium every year," he said.

"The minuscule amount of extra radiation won't make the tiniest jot of difference."

Regardless of the science, the Fukushima release has created a political opening for Beijing, according to Mihai Sora, a former Australian diplomat who is now with the Lowy Institute in Sydney.

Japan has "done a lot of diplomacy to win over as many Pacific leaders as they can", he said, but "almost universally this will be an unpopular decision among Pacific communities".

"You can imagine Beijing using its diplomatic access to encourage some of its partners to speak out about this strongly because it serves Beijing's interests."

As well as fears about damaging vital fish supplies and sensitive marine ecosystems, the Fukushima water release has caused disquiet in a region where nuclear issues are highly sensitive.

For decades, major powers including the United States, Britain and France used the sparsely populated South Pacific to test atomic weapons -- with consequences that linger to this day.