NHK [Japanese Public Television] has learned that a government panel of experts will say it has been unable to specify exactly how the radioactive release occurred at a reactor of the crippled Fukushima Daiichi nuclear power plant.
On March 15th, 4 days after the breakdown of the Fukushima Daiichi plant, its No. 2 reactor appeared to release the largest amount of radioactive substances since the start of the disaster.
The panel investigating the accident at Fukushima Daiichi will present a new observation in its final report later this month.
The report will say pressure in the suppression chamber of the No. 2 reactor was falling gradually between 1:30 pm to 6:00 pm on March 14th.
It will say this suggests that the suppression chamber collapsed at the time.
The plant operator, Tokyo Electric Power Company, has insisted that the suppression chamber was destroyed during the morning hours of March 15th, when pressure was falling rapidly, instead of the previous day.
The panel will take issue with TEPCO's view, saying their analysis probably does not reflect what actually happened.
It will conclude that it has been unable to specify the details of how the radioactive release occurred because the panel's on-site investigation and time were limited.
The panel will also propose that TEPCO continue its investigation to determine how the reactor was damaged.
Noting that an investigation using robots has just begun in the No.2 reactor, Professor Koji Okamoto at the University of Tokyo Graduate School says available information is still insufficient.
He also says the investigation should be continued with help from experts from abroad.