, Jan 29, 2015 (emphasis added): New Findings on Fallout

At 0:15 - Experts are still trying to grasp all the details of the [Fukushima] disaster. They have made new discoveries about the radioactive substances released from the reactors.

At 0:35 – On Mar 13, 2011, a U.S. aircraft carrier deployed off Northeastern Japan detected an increase in the level of radiation in the atmosphere. The crew kept a running record of the data.

At 1:00 - Up until now, people looking into the accident had focused on the 4 days immediately after the disaster. That’s because they thought the bulk of radioactive substances was released during that period. But the data analyzed by the researchers suggests something different — only 25% of the radioactive substances drifted during the first 4 days [and] the remaining 75% spread over the next 2 weeks. We analyzed why this happened.

At 1:50 in — Fire engines [tried] to spray water into the reactors to keep them from melting down. The fire engines pumped out 30 tons of water every hour, but an in house investigation by the plants operator shows only about 1 ton per hour reached the targets… We conducted an experiment to see if this contributed to the massive release of radioactive fallout… [Zirconium was] heated to 1,200°C, the estimated temperature inside the reactors when the accident happened [Nuclear Engineer: Temps were "2,800°C within 3 to 4 hours of loss of cooling power"]… The water from the fire engines [was added and the] temperature of the metal quickly began to climb — in 2 minutes, it surged by 78°C [86°F/minute]. Experts suspect this is why large amounts of radioactive substances escaped over an extended time.

At 3:00 - Masanori Naitoh, director of Institute for Applied Energy (a foundation authorized by Japan’s Ministry of International Trade and Industry): “Fuel keeps melting slowly as zirconium generates a relatively large amount of heat. The metal remained hot for some time. This means radioactive materials will be released for a longer time.”… The experiment shows that the water used to prevent the meltdowns may have actually sustained them. The experts say the the results show that radioactive substances kept leaking out and spreading into the atmosphere.

At 4:00 - ‘Why wasn’t the fallout discovered until now?‘ [Investigations have] tried to figure out why no one was able to control the situation. They focused on the 4 or 5 days after the disaster when Tepco failed to prevent the reactors from melting…  No one’s been able to get close enough to determine what’s happening inside. It’s possible there still may be more data to analyze about radioactive substances released from the plant. This is why experts believe it’ll take several decades to get a complete picture of what happened. In the mean time, everyone needs to keep in mind that no nuclear plant is perfectly safe. Members of the media need to  keep watching the situation and report on future developments as the happen.

NHK, partial transcript

Watch the broadcast here