Tokyo - Japan's earthquake-stricken nuclear complex is still emitting radiation but the source is unclear, a senior United Nations atomic agency official said, as workers made progress restoring electric power to the site.
The International Atomic Energy Agency (IAEA) also raised concerns about a lack of information from Japanese authorities, as workers battling to cool the nuclear reactors faced rising temperatures around the core of one reactor.
“We continue to see radiation coming from the site and the question is where exactly is that coming from?” James Lyons, a senior official of the International Atomic Energy Agency (IAEA), told a news conference in Vienna on Tuesday.
Despite hopes of progress in the world's worst nuclear crisis in a quarter of a century, triggered by an earthquake and tsunami that left at least 21 000 people dead or missing, plant operator Tokyo Electric Power Co (TEPCO) said it needed more time before it could say the reactors were stabilised.
Senior IAEA official Graham Andrew said that the overall situation remained “very serious” and that the UN atomic watchdog was concerned it had not received some information from Japan about the Fukushima nuclear plant.
“We have not received validated information for some time related to the containment integrity of unit 1. So we are concerned that we do not know its exact status,” he said.
The IAEA also lacks data on the temperatures of the spent fuel pools of reactors 1, 3 and 4, he said, though Japan was supplying other updates.
Technicians working inside an evacuation zone around the plant on Japan's northeast Pacific coast, 250km north of Tokyo, have attached power cables to all six reactors and started a pump at one to cool overheating nuclear fuel rods.
Local media reported late on Tuesday that lighting had been restored at one of the control rooms, bringing the operators a step closer to reviving the plant's cooling systems.
Earlier smoke and steam were seen rising from two of the most threatening reactors, No.2 and No.3, threatening to dash hopes of progress in bringing them under control.
There have been several blasts of steam from the reactors during the crisis, which experts say probably released a small amount of radioactive particles.
Hidehiko Nishiyama, the deputy-director general of Japan's nuclear safety agency, later said the smoke at reactor No.3 had stopped and there was only a small amount at No.2.
He gave no more details, but a TEPCO executive vice president, Sakae Muto, said the core of reactor No.1 was now a worry with its temperature at 380-390 degrees Celsius.
“We need to strive to bring that down a bit,” Muto told a news conference, adding that the reactor was built to run at a temperature of 302 degrees Celsius.
Asked if the situation at the problem reactors was getting worse, he said: “We need more time. It's too early to say that they are sufficiently stable.”
Reuters earlier reported that the Fukushima plant was storing more uranium than it was originally designed to hold, and that it had repeatedly missed mandatory safety checks over the past decade, according to company documents and outside experts.
Questions have also been raised about whether TEPCO officials waited too long to pump sea water into the reactors and abandon hope of saving the equipment in the aftermath of the earthquake and tsunami.
But one expert said the smoke or steam seen over the reactors did not seem to be linked to rises in radiation levels.
“Overall there is progress compared to a few days ago when everything seemed hopeless. But we still judge the situation to be critical,” said Per Bystedt,an analyst at the Swedish Radiation Protection Authority.
“The positive thing is that electric power is more or less connected to all the plants.” - Reuters