TEPCO says water has leaked from one of the reactors, exposing fuel rods and trigging their meltdown. The news doesn't get any betterwith seawater samples near another reactor showing levels of radioactive caesium at 18-thousand times the legal limit.
Presenter: Mark Willacy
Junichi Matsumoto, Tepco General Manager; Nobuyuki Mizuno, Nuclear Expert
MARK WILLACY: After two long months things were supposed to be stabilising at reactors one, two and three at Fukushima.
But instead the operator TEPCO is now saying there's been another radioactive water leak from reactor three and that there's been a probable meltdown of fuel rods at reactor one.
So how do they know? Well for the first time since the tsunami workers have been finally been able to fix gauges in the badly damaged reactor one and those gauges revealed some bad news.
(Sound of Junichi Matsumoto speaking)
"All the fuel rods are unprotected at this point because the water level is below the reactor core," says TEPCO general manager Junichi Matsumoto.
"So we've come to the conclusion that the fuel could be at the bottom of the containment vessel," he says.
In other words it's melted down because water has been leaking from the containment vessel, leaving almost half the length of the four-metre tall nuclear fuel rods exposed.
But TEPCO insists there is some good news.
(Sound of Junichi Matsumoto speaking)
"The reactor core is cooling down," says TEPCO general manager Junichi Matsumoto, "and it's unlikely to heat up again. The internal pressure is also decreasing. So the company doesn't regard this situation as critical," he says.
But others don't share that sanguine assessment.
(Sound of nuclear expert Nobuyuki Mizuno speaking)
"A meltdown of the fuel makes cooling very difficult," says nuclear expert Nobuyuki Mizuno.
"The melted fuel is covered in water but inside this mass of material could be extreme temperatures. That makes it harder to keep the reactor stable," he says.
There's also the question of where is all the water being pumped into the reactor leaking to?
Every hour seven tonnes of water is forced in to douse the reactor.
At least TEPCO has found and fixed a radioactive water leak in reactor three, filling a pit with concrete to stop that problem but not before seawater samples near the reaction showed contamination of caesium-134 at a concentration 18,000 times the legal limit.
