In the world's worst nuclear accident in a quarter of a century, reactor meltdowns at the Fukushima facility after the March 2011 earthquake and tsunami sent radiation spewing over large areas, forcing more than 160,0000 people to flee.
"Overall, the conditions there have been maintained rather in a stable condition ... but there is no denying that the whole situation remains precarious of course," said Kenzo Oshima, a commissioner at Japan's Nuclear Regulation Authority (NRA).
The plant operator, Tokyo Electric Power Co (TEPCO), has taken extra safeguards and reinforcement measures concerning the spent fuel pool of Fukushima's No. 4 reactor in order for it to withstand any new earthquake, Oshima said.
"A lot of precaution, a lot of care, a lot of attention is still very much needed," he told reporters after meeting U.N. nuclear agency chief Yukiya Amano in Vienna.
In April, U.S. Senator Ron Wyden said after visiting the site that Japan, with assistance from the U.S. government, needed to do more to move spent fuel rods out of harm's way.
The NRA started operations in September, replacing two regulators that had been widely criticized for being too close to the industry they were supposed to monitor.
When a Reuters journalist went to the plant this month, workers were seen putting together water filtration systems and shifting equipment near the reactors, two of which remain capped by twisted steel and damaged concrete.
NRA head Shuichi Tanaka last week said it would impose tighter safety standards for nuclear plants. Japan's 50 reactors were shut after the disaster.
Oshima said the NRA would soon conduct an in-depth risk assessment regarding the Ohi nuclear facility, where two reactors were restarted this year despite warnings by some geologists of dangerous fault lines running beneath the plant.
Asked whether the plant could be shut as a result, he said: "It depends upon the findings, of course."
The regulator will abide by a government rule of a 40-year lifetime for reactors, even though it can be extended under certain circumstances by up to two decades, Oshima said.
"But basically I think the government has indicated its intention to have this rule applied as strictly as possible," he added.
(Reporting by Fredrik Dahl; editing by Jane Baird)
