TOKYO - Japan's nuclear authority plans to conduct radiation contamination surveys at 600,000 points on the seabed off the crippled Fukushima nuclear plant, up from 200 places so far, a report said on Saturday.
The Nuclear Regulation Authority is to survey the spots in a 1,000 sq km area that stretches 50km north-south and 20km east-west off Fukushima, the Yomiuri newspaper reported.
The surveys are meant to measure caesium levels to assess the long-term effect on marine resources of the radiation that has been leaking from the stricken plant since it was struck by a tsunami in 2011, the daily said.
Tokyo Electric Power (Tepco) has been struggling to contain contaminated water at the plant. It has poured thousands of tonnes of water on the plant's reactors to tame meltdowns sparked by the quake-tsunami disaster.
The utility operator said the reactors are now stable but need to be kept cool to prevent them from running out of control again. Much of the now-contaminated water is being stored in temporary tanks at the plant, and Tepco has so far revealed no clear plan for it.
The problem has worsened with leaks in some of the tanks believed to have affected groundwater running out to sea.
The continuing nuclear catastrophe has come under the international spotlight in recent weeks as Tokyo fought off challenges from Madrid and Istanbul for the right to host the 2020 Olympic Games.
Hours before Tokyo was chosen as host, Japanese Prime Minister Shinzo Abe gave an emphatic speech declaring that radioactive contaminants from the leakage were "completely blocked" in waters inside the bay near the plant.
But Mr Abe's remarks have backfired at home, with Japanese media and opposition lawmakers saying his comments that the leaks of contaminated water at Fukushima are "under control" were overkill.
But Ms Hikariko Ono of the Prime Minister's Office on Saturday defended Mr Abe's pledge, citing offshore monitoring results showing undetectable radioactivity.